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Title:
BARRIER ELEMENTS FOR LIGHT DIRECTING ARTICLES
Document Type and Number:
WIPO Patent Application WO/2017/004003
Kind Code:
A1
Abstract:
The present disclosure relates to barrier elements and their use on a light directing articles, such as daylight redirecting articles, which comprise microstructured elements, for example, in the form of a microstructured optical film.

Inventors:
BAETZOLD, John, P. (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
PATEL, Suman, K. (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
TERZIC, Denis (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
PEKUROVSKY, Mikhail, L. (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
AHO, Erik, A. (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
TAPIO, Scott, M. (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
NIRMAL, Manoj (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
STRADINGER, John, J. (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
Application Number:
US2016/039750
Publication Date:
January 05, 2017
Filing Date:
June 28, 2016
Export Citation:
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Assignee:
3M INNOVATIVE PROPERTIES COMPANY (3M Center, Post Office Box 33427Saint Paul, MN, 55133-3427, US)
International Classes:
B32B3/30; G02B5/04; G02B5/124; F21V8/00
Foreign References:
US20130034682A12013-02-07
US20120219793A12012-08-30
US20130114142A12013-05-09
Attorney, Agent or Firm:
TÉLLEZ, Carlos, M. et al. (3M Center, Office of Intellectual Property CounselPost Office Box 3342, Saint Paul MN, 55133-3427, US)
Download PDF:
Claims:
What is claimed is:

1. An article comprising:

a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;

an adhesive layer;

wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

wherein the total surface area of the one or more barrier elements is greater than 60% of the light redirecting area;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, and

wherein the article allows transmission of visible light.

2. An article according to any of the preceding claims, wherein the one or more barrier

elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.5 Gpa to 3.4 Gpa.

3. An article according to any of the preceding claims, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 5 microns.

4. The article of any one of the preceding claims, wherein the barrier element comprises a crosslinked acrylate polymeric matrix.

5. The article of any one of the preceding claims, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity from 100 cPS to 1500 cPS.

6. An article according to any of the preceding claims, wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area.

7. An article according to any of the preceding claims, wherein a barrier element comprises a diffusing agent.

8. An article according to any of the preceding claims, wherein the adhesive in the adhesive layer is chosen from a pressure sensitive adhesive, a thermoset adhesive, hot melt adhesive, and a UV-curable adhesive.

9. An article according to any of the preceding claims, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 300 g/in.

10. A film comprising an article according to any of the preceding claims,

wherein the article further comprises a second substrate adjacent the second major surface of the adhesive layer;

wherein the article further comprises a window film adhesive layer adjacent the second major surface of the light redirecting layer; and

wherein the article optionally further comprises a liner adjacent the window film adhesive layer.

11. A window comprising a film as claimed as in any of the preceding claims directed to a film, wherein the window further comprises a glazing immediately adjacent the window film adhesive layer.

12. A film according to any of the preceding claims directed to films that comprise a diffuser, wherein the diffuser is chosen from bulk diffusers, surface diffusers, and embedded diffusers or combinations thereof.

13. A method of making an article comprising:

providing a first substrate having a first major surface and a second major surface opposite the first major surface;

applying an adhesive layer to the first major surface of the first substrate;

wherein the adhesive layer has a first major surface and a second major surface opposite the first major surface; and wherein the second major surface of the adhesive layer is immediately adjacent the first major surface of the first substrate;

printing one or more barrier elements on the first major surface of the adhesive layer; setting the one or more barrier elements;

laminating a light redirecting layer on the first major surface of the adhesive layer;

wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

wherein the total surface area of the one or more barrier elements is greater than 60% of the light redirecting area;

wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with the one or more barrier elements; wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

wherein the article allows transmission of visible light.

14. A method according to any of the preceding claims directed to methods, wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area.

15. A method according to any of the preceding claims directed to methods, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 300 g/in.

Description:
BARRIER ELEMENTS FOR LIGHT DIRECTING ARTICLES

Cross-Reference to Related Applications

This application claims priority from U.S. Provisional Application Serial No. 62/187,219, filed June 30, 2015, the disclosure of which is incorporated by reference in its entirety herein.

Field

The present disclosure relates to barrier elements and their use on a light directing articles, such as daylight redirecting articles, which comprise microstructured elements, for example, in the form of a microstructured optical film.

Background

Light directing articles have an ability to manipulate incoming light. Light directing films and sheeting typically include an optically active portion that may be microstructured elements or beads.

Light directing articles may allow portions of light to pass through the substrate in a controlled manner, such as light redirecting films. In these types of light redirecting articles, the microstructured elements are typically microstructured prisms. Alternatively, the light directing articles may not be transmissive to light and instead reflect all incident light. Throughout this disclosure the terms light directing articles and light redirecting articles are used interchangeably.

Daylight redirecting films (DRFs) provide natural lighting by redirecting incoming sunlight upward, onto the ceiling. This can lead to significant energy savings by reducing the need for artificial lights. Light Redirection Films can consist of linear optical microstructures that reflect incoming sunlight onto the ceiling. DRFs are typically installed on the upper clerestory section of windows T and above. A typical configuration is shown on Figure 1.

Sunlight that would normally land on the floor can be used to provide natural lighting by using suitable constructions involving daylight redirecting films. Figure 2 shows an example of the amount of light that can be redirected from the floor to the ceiling by the use of a DRF.

Buildings (residential & commercial) account for about 40% of all energy consumed and lighting represents about 30% of that energy. Substituting even a fraction of artificial lighting with natural light can yield significant energy savings.

In general, microstructured light redirecting films may be fragile under certain

circumstances because the microstructured features may be subject to mechanical damage and/or chemical damage (e.g. window cleaners). One challenge when attempting to protect the microstructured elements in a DRF is that the lamination process to add a cover or protective layer can cause damage to those microstructured elements. The same challenge is present when attempting to laminate any other type of functional layer or film, such as a diffuser, to a DRF on the side of the microstructured elements. Additionally, the presence of an additional layer next to the DRF may also modify its optical properties and significantly decrease or nullify its light redirecting properties.

Other embodiments of light directing articles may redirect incident light towards its originating source, and are referred to as retroreflective articles. The ability to retroreflect light has led to the wide-spread use of retroreflective sheetings on a variety of articles. For retroreflective articles, the microstructured element typically is a microstructured prism that is a cube-corner. U.S. Patent 5,450,235 shows an example of a cube-corner retroreflective sheeting.

Typically, a cube corner element includes three mutually perpendicular optical faces that intersect at a single apex. Generally, light that is incident on a corner cube element from a light source is totally internally reflected from each of the three perpendicular cube corner optical faces and is redirected back toward the light source. Presence of, for example, dirt, water, and adhesive on the optical faces can prevent total internal reflection (TIR) and lead to a reduction in the retroreflected light intensity. As such, the air interface is typically protected by a sealing film. However, sealing films may reduce the total active area, which is the area over which

retroreflection can occur. Further, sealing films increase the manufacturing cost. Additionally, the sealing process can create a visible pattern in the retroreflective sheeting that is undesirable for many applications, such as, for example, use in a license plate and/or in commercial graphics applications where a more uniform appearance is generally preferred. Metalized cube corners do not rely on TIR for retroreflective light, but they are typically not white enough for daytime viewing of, for example, signing applications. Furthermore, the durability of the metal coatings may be inadequate.

One of the goals of the present disclosure is to provide film constructions that allow the bonding of a microstructured film, to another functional film, without significantly sacrificing the optical performance of the microstructured film, while maintaining robust mechanical properties of the entire construction.

Summary

The disclosed light redirecting article comprises a structured layer, an adhesive layer, and barrier elements. The structured layer comprises multiple microstructured elements that are opposite a major surface. The adhesive layer has a first region and a second region. The second region is in contact with the structured layer. The barrier elements are in contact with the first region. Typically, the physical and rheological properties of the first and second regions are the same because they are part of the same adhesive material. In certain embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa. In other embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa.

Unless otherwise indicated, all numbers in the description and the claims expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviations found in their respective testing measurements.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. a range from 1 to 5 includes, for instance, 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

The term "adhesive" as used herein refers to polymeric compositions useful to adhere together two components (adherents).

The term "window film adhesive layer" as used herein refers to a layer comprising an adhesive suitable to bond a film to a window or glazing, such as, for example, a pressure sensitive adhesive.

The term "adjacent" as used herein refers to the relative position of two elements, such as layers in a film construction that are close to each other and may or may not be necessarily in contact with each other and may have one or more layers separating the two elements, as understood by the context in which "adjacent" appears. The term "immediately adjacent" as used herein refers to the relative position of two elements, such as layers in a film construction, that are immediately next to each other without having any other layers separating the two elements, as understood by the context in which "immediately adjacent" appears.

The term "construction" or "assembly" are used interchangeably in this application when referring to a multilayer film, in which the different layers can be coextruded, laminated, coated one over another, or any combination thereof.

The term "light redirecting layer" as used herein refers to a layer that comprises microstructured prismatic elements.

The term "light redirecting film" as used herein refers to a film that comprises one or more light redirecting layers and optionally other additional layers, such as substrates or other functional layers.

Light redirection, in general, may be called daylight redirection, sunlight redirection, or solar light redirection when the source of light is the sun.

The term "film" as used herein refers, depending on the context, to either a single layer article or to a multilayer construction, where the different layers may have been laminated, extruded, coated, or any combination thereof.

The term "barrier elements" as used herein refers to physical features laid on top of regions of an adhesive layer that help maintain the optical performance of the light redirecting layer when the adhesive layer and light redirecting layer are bonded to each other in opposing fashion. The barrier elements prevent the adhesive layer from filling the space surrounding microstructured prismatic elements and are able to provide an interface between the DRF and a low refractive index material, such as air or aerogel. In certain instances in this disclosure the barrier elements are also called "passivation islands," or "islands."

The term "microstructured prismatic element" as used herein refers to an engineered optical element, wherein at least 2 dimensions of the features are microscopic, that redirects input light with certain angular characteristics into output light with certain angular characteristics. In certain embodiments, the height of the microstructured prismatic element is less than 1000 microns. A microstructured prismatic element may comprise a single peak structure, a multipeak structure, such as a double peak structure, structures comprising one or more curves, or combinations thereof. The microstructured prismatic elements, including all of their physical and optical characteristics (e.g., glare, TIR angles, etc.), are disclosed in provisional applications titled "Room-Facing Light Redirecting Film with Reduced Glare" and "Sun-Facing Light Redirecting Film with Reduced Glare," both filed on October 20, 2014, and having application nos. 62/066,307 and 62/066,302respectively, are hereby incorporated by reference. The term "diffusing agent" as used herein refers to features or additives incorporated in the article that increase the angular spread of light passing through the same article.

The term "repeating 1-dimensional pattern" as used herein refers to features that are periodic along one direction in reference to the article.

The term "repeating 2-dimensional pattern" as used herein refers to features that are periodic along 2 different directions in reference to the article.

The term "random-looking 1- or 2-dimensional pattern" as used herein refers to features that appear not to be periodic or semi-periodic along one or two different directions in reference to the article. Those features may still be periodic but with a period sufficiently larger than the mean pitch of individual features so that the period is not noticeable to most viewers.

As used herein, the index of refraction of a material 1 ("RI1") is said to "match" the index of refraction of a material 2 ("RI2") if the value RI1 is within +/- 5% of RI2.

For the following definitions of "room-facing" and "sun-facing," it is assumed that a light redirecting layer has a first major surface and second major surface opposite the first major surface and that the first major surface of the light redirecting film comprises microstructured prismatic elements.

As used herein, the term "room-facing," in the context of a light redirecting film or a construction comprising a light redirecting film, refers to a film or construction where the incident light rays pass through the major surface of the light redirecting film not containing the microstructured prismatic elements before they pass through the major surface that contains the microstructured prismatic elements. In the most typical configuration, when the light redirecting film is located on an exterior window (i.e., when the window faces the exterior of a building), the microstructured prismatic elements in a "room-facing" configuration are oriented facing the interior of the room. However, the term "room-facing," as defined herein can also refer to configurations where the light redirecting film is on a glazing, or other kind of substrate, that does not face the exterior of the building, but is in between two interior areas.

As used herein, the term "sun-facing," in the context of a light redirecting film or a construction comprising a light redirecting film, refers to a film or construction where the incident light rays pass through the major surface of the light redirecting film containing the

microstructured prismatic elements before they pass through the other major surface (the major surface not containing the microstructured prismatic elements). In the most typical configuration, when the light redirecting film is located on an exterior window (i.e., when the window faces the exterior of a building), the microstructured prismatic elements in a "sun-facing" configuration are oriented facing the sun. However, the term "sun-facing," as defined herein can also refer to configurations where the light redirecting film is on a glazing that does not face the exterior of the building, but is in between two interior areas.

As used herein, the term "sealing" or "sealed" when referring to an edge of an article of this disclosure means blocking the ingress of certain undesired elements such as moisture or other contaminants.

The term "setting" as used herein refers to transforming a material from an initial state to its final desired state with different properties such as flow, stiffness, etc., using physical (e.g. temperature, either heating or cooling), chemical, or radiation (e.g. UV or e-beam radiation) means.

The term "visible light" as used herein refers to refers to radiation in the visible spectrum, which in this disclosure is taken to be from 400 nm to 700 nm.

Brief Description of the Drawings

FIGS. 1A and IB are schematic side views of one exemplary embodiment of a light redirecting article of the present disclosure.

FIG. 2 is schematic drawing of one exemplary intermediary step in forming the light redirecting article of FIG. 1.

FIG. 3 is a schematic drawing of one exemplary embodiment of a light redirecting article of the present disclosure.

FIG. 4 shows a construction having both clear view-through regions and light redirecting regions.

FIG. 5 shows a room-facing configuration having a light redirecting film and diffuser.

FIG. 6 shows two different sun-facing configurations having a light redirecting film and diffuser. The panel on the left-hand side is Figure 6A and the panel on the right-hand side is Figure 6B.

FIG. 7 is a schematic diagram of a typical process to bond a microstructured film to a second film. Figure 7A shows the film before bonding and Figure 7B shows the film after bonding.

FIG. 8 shows three different patterns for barrier elements.

FIG. 8A shows an example of a daylight redirecting glazing construction with see-through regions.

FIG. 9 shows barrier elements that have partially merged.

FIG. 10 shows barrier elements that are well defined.

FIG. 11 shows a DRF laminate in which the barrier elements show evidence of widespread failure. FIG. 12 is a cross-sectional view of failed barrier elements.

FIG. 13 is a photomicrograph of one embodiment of the invention, showing a DRF laminate in which the barrier elements show no sign of failure. While the above-identified drawings and figures set forth embodiments of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of this invention. The figures may not be drawn to scale.

Detailed Description

The disclosure in the present disclosure is exemplified by referring to light redirecting films and light redirecting layers as being part of the overall construction, but the concepts and subject matter taught and claimed in this application can extend to other microstructured optical films that are not light redirecting films, such as retroreflective film constructions.

When a seal film is used for light redirecting articles, an additional adhesive is often needed on the seal film to secure the entire light redirecting article to a substrate. It is possible to use an adhesive sealing layer to function as both the seal film and to provide an adhesive surface to secure the light redirecting article to a substrate. (See for example, U.S. Patent Application Publications 2013-0034682 and 2013-0135731, the disclosures of which are herein incorporated by reference).

FIGS. 1A and IB are schematic side views of one exemplary embodiment of a light redirecting article 100 of the present disclosure, where the adhesive sealing layer 130 is a pressure sensitive adhesive. FIG. 2 is a schematic drawing of one exemplary intermediary step in forming the light redirecting article 100 of FIG. 1. FIG. 3 is a schematic drawing of one exemplary embodiment of a light redirecting article 100 of the present disclosure where the adhesive sealing layer 130 is a structured adhesive. Detailed descriptions of these constructions will be provided below. Similar elements in each of the figures are marked with similar reference numbers.

The disclosed light redirecting article 100 comprises a structured layer 110 and an adhesive sealing layer 130. The structured layer 110 comprises multiple microstructured elements 112 that are opposite a major surface 116 of the structured layer 110. The surface containing the microstructured elements 112 can be referred to as a structured surface 114 of the structured layer 110. The adhesive sealing layer 130 has a first region and a second region wherein the second region is in contact with the structured layer 110. A barrier element 134 is provided at the first region of the adhesive sealing layer 130. The first region with the barrier element and second region have sufficiently different properties to form a low refractive index region between the adhesive sealing layer 130 and the structured layer 110. In some embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa. In other embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa.

The type of bonding disclosed and taught in this application between two films refers to bonding only via selected areas in the light redirecting film in order to preserve the light redirecting function (or a suitable function in other microstructured optical films) of the film. Because the presence of the adhesive contacting the microstructured prismatic elements substantially destroys the ability to redirect light, there is a natural balance between the size of the areas that effect the bonding (partially optically active areas) between the two films and the size of the areas that are optically active (able to redirect light). Thus, to maximize the light management through the microstructured element, it is desired that the portions of the microstructured elements in contact with the barrier elements not be in contact with the adhesive or penetrate into the barrier element. The barrier element forms a physical "barrier" between the adhesive of the adhesive sealing layer and the microstructured element. Barrier element has sufficient structural integrity to prevent the adhesive sealing layer from flowing into a low refractive index region that is between structured surface and barrier layer. Barrier layer can directly contact or be spaced apart from or can push slightly into the tips of microstructured elements.

It is desired too that the microstructured element is not in contact with the adhesive of the adhesive sealing layer in areas where the barrier elements are present or that the microstructured element penetrate into the barrier element because then that microstructured element's ability to manage the incoming light is lost or minimized at that portion of the microstructured element that has penetrated into the adhesive or the barrier element. For example, if the light redirecting article is a retroreflective article, the cube-corner's ability to retroreflect the incident light is lost in the portion of the cube-corner prism that has penetrated into the barrier element. If the light redirecting article is a DRF, the ability to redirect light is lost or reduced because the refractive properties of the microstructure change in the portion that penetrates the barrier element.

Depending on the magnitude of the penetration, light leakage can occur, which may be manifested as glare in daylight redirecting films

The inventors originally believed that a highly crosslinked and tough barrier element would be ideal for maximizing the light management abilities of the microstructured elements adjacent to the barrier elements because the microstructured element would not be able to penetrate into the barrier element. However, to their surprise, the inventors found that highly crosslinked and tough barrier element did not perform as expected to prevent penetration or breakthrough. Barrier elements highly crosslinked cracked and, once cracked, the effectiveness of the barrier element is reduced. Unexpectedly, materials with relatively brittle properties and rigidity perform much better at preventing failure.

The inventors found that in acrylate systems, for example, the average functionality of the molecule can be used to describe its amount of cross-linking or tendency to be brittle. For example, for a bis epoxy acrylate molecule (below), the number of theoretical acrylates/molecule is 2 (end regions are acrylate groups).

The compositions chosen may be based on mono-acrylate, diacrylate, and higher multifunctional acrylate materials. For a mixture of acrylate materials, the average functionality is the weight average of the functionalities of all the components in the mixture. The chemistries may be chosen from many classes of acrylates, including urethane acrylates, polyester acrylates, acrylic acrylates, and pentaerythritol-based acrylates, for example.

The brittleness can be evaluated by creating thick films of the cured barrier element material and conducting tensile tests (stress versus strain) experiments. In general, brittle materials fail with little or no elongation. In addition, when cast into a film and cured, these films crack with little handling.

In some embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa. In other embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa.

The barrier elements 134 should be sufficiently thick to prevent the microstructured element 1 12 from breaking through into the adhesive sealing layer 130. In one embodiment, the crosslinked polymeric matrix of the barrier element 134 is at least 1.6 microns thick. In one embodiment, the barrier element 134 is at least 1.75 microns thick. In one embodiment, the barrier element 134 is at least 2.0 microns thick. In other embodiments, the barrier element 134 is at least 3 microns thick. In other embodiments, the barrier element 134 is at least 5 microns thick. In other embodiments, the barrier element 134 is at least 7 microns thick. In other embodiments, the barrier element 134 is at least 8 microns thick. In other embodiments, the barrier element 134 is at least 10 microns thick.

In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 5 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 3 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 2 microns.

In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 5 microns . In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 3 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 2 microns.

In other embodiments, the barrier element 134 has a thickness from 2 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 5 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 3 microns.

In other embodiments, the barrier element 134 has a thickness from 3 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 3 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 3 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 3 microns to 5 microns.

The disclosed barrier element prevents wetting of microstructured element 112 by the pressure sensitive and prevents the microstructured elements 1 12 from penetrating into the barrier element 134, for example, either initially during fabrication of the light redirecting article, during fabrication when the material is stacked, handled, or laminated, or over time due pressure and flexing of to the viscoelastic nature of the adhesive. Trapped air between pressure sensitive adhesive 130 and microstructured elements 1 12 creates low refractive index region 138. Other materials, such as aerogel, may be used in place of air, as long as the material has a refractive index that allows the microstructured elements to redirect light. The presence of the barrier element 134 permits the portions of structured surface 1 14 adjacent to low refractive index region 138 and/or barrier element 134 to redirect or retroreflect incident light 150. Barrier layers 134 may also prevent pressure sensitive adhesive 130 from wetting out the microstructured layer (e.g., DRF or cube sheeting). As mentioned before, pressure sensitive adhesive 130 that is not in contact with a barrier layer 134 adheres to the microstructed elements, thereby effectively sealing the areas to form optically active areas or cells. In some embodiments, the pressure sensitive adhesive 130 also holds the entire construction together, thereby eliminating the need for a separate sealing film and sealing process. In some embodiments, the pressure sensitive adhesive is in contact with or is directly adjacent to the structured surface of the DRF or the cube corner elements, as the case may be.

In general, any material that prevents the pressure sensitive adhesive from contacting microstructured elements 1 12 or flowing or creeping into low refractive index region 138 can be used in barrier element 134. Exemplary materials for use in barrier element 134 include resins, polymeric materials, dyes, inks, vinyl, inorganic materials, radiation-curable polymers (for example, UV curable or e-beam curable), pigment. In one embodiment, exemplary materials used to form the barrier elements include crosslinkable acrylates. In one embodiment, exemplary materials used to form the barrier elements include crosslinkable urethane acrylates, acrylic acrylates, polyester acrylates. In one embodiment, exemplary materials used to form the barrier elements include crosslinkable molecule with at least 2 acrylate groups.

In one embodiment, the composition further comprises a diluent to control viscosity of the composition. In one embodiment, the diluent has a viscosity of less than 200 cPS. In one embodiment, the diluent has a viscosity of less than 10 cPS. In one embodiment, the diluent has a viscosity of less than 50 cPS and greater than 3 cPS.

In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 2500 cPS or less. In one embodiment, the composition for forming the barrier islands 134 has a viscosity of 2000 cPS or less. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 1500 cPS or less. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 1000 cPS or less. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 100 cPS or greater. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 300 cPS or greater. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 400 cPS or greater. In other embodiments, the composition for forming the barrier elements 134 has a viscosity of 500 cPS or greater. In other embodiments, the composition for forming the barrier elements 134 has a viscosity of 800 cPS or greater. In other embodiments, the composition for forming the barrier elements 134 has a viscosity of 1000 cPS or greater.

In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 2500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 2000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 2500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 2000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 2500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 2000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 2500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 2000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 800 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 900 cPS to 1300 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 1000 cPS to 1300 cPS.

In one embodiment, the composition for forming the barrier islands 134 further comprises a photoinitiator. In one embodiment, the photoinitiator is present in at least 0.5% and less than 2.0 wt. % of the total composition for forming the barrier islands 134.

In one embodiment the composition for forming the barrier islands 134 further comprises a solvent that is ideally non-reactive and less than 10% wt. of the total composition for forming the barrier islands 134.

FIGS. 1A and IB show one exemplary embodiment of a light redirecting article 100. Light redirecting article 100 includes a structured layer 110 including microstructured elements 112 that collectively form a structured surface 114 opposite a major surface 116. Structured layer 1 10 also includes an optional overlay layer 1 18. An adhesive sealing layer 130 is adjacent to structured layer 1 10, and specifically is adjacent to the microstructured elements 1 12 at the structured surface 114. Adhesive sealing layer 130 includes one or more barrier elements 134. If the embodiment shown in FIGS. 1A and IB, is directed to retroreflective material, then the viewer 102 observes retroreflected light 150 from a microstructured element 1 12 that is a cube corner. It is understood that this basic construction for a light redirecting article 100 could be used when the microstructured element 1 12 is a prism that instead of retroreflects light the prism redirects the path of the light that enters the prism and leaves through the barrier element 134 and adhesive sealing layer 130. That is, if the embodiment shown in FIGS. 1A and IB is a DRF, then viewer 102 will observe refracted light exiting the construction on the opposite side (major surface) from where the incident light entered the construction.

As is shown in FIG. IB, in the case of a retroreflective article, a light ray 150 incident on a cube corner element 1 12 that is adjacent to low refractive index region 138 is retroreflected back to viewer 102. For this reason, a first region of light redirecting article 100 that includes low refractive index region 138 is referred to as an optically active area. In contrast, a second region does not include the low refractive index region 138 where the adhesive sealing layer 130 is in contact with the structured surface 1 14 of the structured layer 1 10. For a retroreflective article, at the second region incident light is not retroreflected and is referred to as an optically inactive area. For light redirecting articles that control the direction of light passing through the light redirecting article, at the second region the prisms do not direct light out in the predetermined fashion as is accomplished in the first region and is referred to as an optically inactive area. Examples of DRF are shown in Figures 4 to 6

Low refractive index region 138 includes a material that has a refractive index that is less than about 1.30, less than about 1.25, less than about 1.2, less than about 1.15, less than about 1.10, or less than about 1.05. Exemplary low refractive index materials include air and low index materials are described in U.S. Patent Application Publication 2012/0038984, which is hereby incorporated herein by reference.

In at least some embodiments, the adhesive layer includes a first region and a second region. The first region is in contact with the barrier elements. The second region is in contact with the structured surface. Typically, the physical and rheological properties of the first and second regions are the same because they are part of the same adhesive material. In some embodiments, the second region includes a pressure sensitive adhesive and the first region differs in composition from the second region. In some embodiments, the first region and the second region have different polymer morphology. In some embodiments, the first region and the second region have different flow properties. In some embodiments, the first region and the second region have different viscoelastic properties. In some embodiments, the first region and the second region have different adhesive properties. In some embodiments, the retroreflective article or the DRF include a plurality of second regions that form a pattern. In some embodiments, the pattern is one of an irregular pattern, a regular pattern, a grid, words, graphics, and lines.

Exemplary pressure sensitive adhesives for use in the adhesive sealing include crosslinked tackified acrylic pressure -sensitive adhesives. Other pressure sensitive adhesives such as blends of natural or synthetic rubber and resin, silicone or other polymer systems, with or without additives can be used. The PSTC (pressure sensitive tape council) definition of a pressure sensitive adhesive is an adhesive that is permanently tacky at room temperature which adheres to a variety of surfaces with light pressure (finger pressure) with no phase change (liquid to solid).

Acrylic Acid and Meth(acrylic) Acid Esters: The acrylic esters are present at ranges of from about 65 to about 99 parts by weight, preferably about 78 to about 98 parts by weight, and more preferably about 90 to about 98 parts by weight. Useful acrylic esters include at least one monomer selected from the group consisting of a first monofunctional acrylate or methacrylate ester of a non-tertiary alkyl alcohol, the alkyl group of which comprises from 4 to about 12 carbon atoms, and mixtures thereof. Such acrylates or methacrylate esters generally have, as

homopolymers, glass transition temperatures below about -25°C. A higher amount of this monomer relative to the other comonomers affords the PSA higher tack at low temperatures.

Acrylate or methacrylate ester monomers include, but are not limited to, those selected from the group consisting of n-butyl acrylate (BA), n-butyl methacrylate, isobutyl acrylate, 2- methyl butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate (IOA), isooctyl methacrylate, isononyl acrylate, isodecyl acrylate, and mixtures thereof.

Acrylates include those selected from the group consisting of isooctyl acrylate, n-butyl acrylate, 2-methyl butyl acrylate, 2-ethylhexyl acrylate, and mixtures thereof.

Polar Monomers: Low levels of (typically about 1 to about 10 parts by weight) of a polar monomer such as a carboxylic acid can be used to increase the cohesive strength of the pressure- sensitive adhesive. At higher levels, these polar monomers tend to diminish tack, increase glass transition temperature and decrease low temperature performance.

Useful copolymerizable acidic monomers include, but are not limited to, those selected from the group consisting of ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, and ethylenically unsaturated phosphonic acids. Examples of such monomers include those selected from the group consisting of acrylic acid (AA), methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, .beta.-carboxyethyl acrylate, sulfoethyl methacrylate, and the like, and mixtures thereof. Other useful copolymerizable monomers include, but are not limited to, (meth)acrylamides, Ν,Ν-dialkyl substituted (meth)acrylamides, N-vinyl lactams, and N,N- dialkylaminoalkyl (meth)acrylates. Illustrative examples include, but are not limited to, those selected from the group consisting of Ν,Ν-dimethyl acrylamide, Ν,Ν-dimethyl methacrylamide, Ν,Ν-diethyl acrylamide, Ν,Ν-diethyl methacrylamide, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl methacrylate, Ν,Ν-dimethylaminoethyl acrylate, N,N- dimethylaminopropyl acrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, and the like, and mixtures thereof.

Non-polar Ethylenically Unsaturated Monomers: The non-polar ethylenically unsaturated monomer is a monomer whose homopolymer has a solubility parameter as measured by the Fedors method (see Polymer Handbook, Bandrup and Immergut) of not greater than 10.50 and a Tg greater than 15°C. The non-polar nature of this monomer tends to improve the low energy surface adhesion of the adhesive. These non-polar ethylenically unsaturated monomers are selected from the group consisting of alkyl (meth)acrylates, N-alkyl (meth)acrylamides, and combinations thereof. Illustrative examples include, but are not limited to, 3,3,5-trimethylcyclohexyl acrylate, 3,3,5-trimethylcyclohexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, N-octyl acrylamide, N-octyl methacrylamide or combinations thereof. Optionally, from 0 to 25 parts by weight of a non-polar ethylenically unsaturated monomer may be added.

Tackifiers: tackifiers include terpene phenolics, rosins, rosin esters, esters of

hydrogenated rosins, synthetic hydrocarbon resins and combinations thereof. These provide good bonding characteristics on low energy surfaces. Hydrogenated rosin esters and hydrogenated C9 aromatic resins are the most preferred tackifiers because of performance advantages that include high levels of "tack", outdoor durability, oxidation resistance, and limited interference in post crosslinking of acrylic PSAs.

Tackifiers may be added at a level of about 1 to about 65 parts per 100 parts of the monofunctional acrylate or methacrylate ester of a non-tertiary alkyl alcohol, the polar monomer, and the nonpolar ethylenically unsaturated monomer to achieve desired "tack". Preferably, the tackifier has a softening point of about 65 to about 100. degree. C. However, the addition of tackifiers can reduce shear or cohesive strength and raise the Tg of the acrylic PSA, which is undesirable for cold temperature performance.

Crosslinkers: In order to increase the shear or cohesive strength of acrylic pressure- sensitive adhesives, a crosslinking additive is usually incorporated into the PSA. Two main types of crosslinking additives are commonly used. The first crosslinking additive is a thermal crosslinking additive such as a multifunctional aziridine. One example is 1, !'-(!, 3 -phenylene dicarbonyl)-bis-(2-methylaziridine) (CAS No. 7652-64-4), referred to herein as "bisamide". Such chemical crosslinkers can be added into solvent-based PSAs after polymerization and activated by heat during oven drying of the coated adhesive.

In another embodiment, chemical crosslinkers that rely upon free radicals to carry out the crosslinking reaction may be employed. Reagents such as, for example, peroxides serve as a source of free radicals. When heated sufficiently, these precursors will generate free radicals, which bring about a crosslinking reaction of the polymer. A common free radical generating reagent is benzoyl peroxide. Free radical generators are required only in small quantities, but generally require higher temperatures to complete the crosslinking reaction than those required for the bisamide reagent.

The second type of chemical crosslinker is a photosensitive crosslinker that is activated by high intensity ultraviolet (UV) light. Two common photosensitive crosslinkers used for hot melt acrylic PSAs are benzophenone and 4-acryloxybenzophenone, which can be copolymerized into the PSA polymer. Another photocrosslinker, which can be post-added to the solution polymer and activated by UV light is a triazine; for example 2,4-bis(trichloromethyl)-6-(4-methoxy-phenyl)-s- triazine. These crosslinkers are activated by UV light generated from artificial sources such as medium pressure mercury lamps or a UV blacklight.

Hydrolyzable, free-radically copolymerizable crosslinkers, such as monoethylenically unsaturated mono-, di- and trialkoxy silane compounds including, but not limited to,

methacryloxypropyltrimethoxysilane (SILANE™ A- 174 available from Union Carbide Chemicals and Plastics Co.), vinyldimethylethoxysilane, vinylmethyldiethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriphenoxy silane, and the like are also useful crosslinking agents.

Crosslinker is typically present from 0 to about 1 part by weight based on 100 parts by weight of acrylic acid or meth(acrylic) acid esters, polar monomers, and non-polar ethylenically unsaturated monomers.

Aside from thermal, moisture, or photosensitive crosslinkers, crosslinking may also be achieved using high-energy electromagnetic radiation such as gamma or e-beam radiation. In this case, no crosslinker may be required.

Other Additives: Because acrylic pressure-sensitive adhesives have excellent oxidative stability, additives such as antioxidant and UV light absorbers are generally not needed. Small amounts of heat stabilizer can be utilized in hot melt acrylic PSAs to increase thermal stability during processing.

Plasticizers: Optionally, low levels of plasticizer (e.g., less than about 10 parts by weight) may be combined with tackifier to adjust the Tg in order to optimize the peel and the low temperature performance of the adhesive. Plasticizers that may be added to the adhesive of the invention may be selected from a wide variety of commercially available materials. In each case, the added plasticizer must be compatible with the tackified acrylic PSA used in the formulation. Representative plasticizers include polyoxyethylene aryl ether, dialkyl adipate, 2-ethylhexyl diphenyl phosphate, t-butylphenyl diphenyl phosphate, di(2-ethylhexyl) adipate,

toluenesulfonamide, dipropylene glycol dibenzoate, polyethylene glycol dibenzoate,

polyoxypropylene aryl ether, dibutoxyethoxy ethyl formal, and dibutoxyethoxy ethyl adipate.

Various polymeric film substrates comprised of various thermosetting or thermoplastic polymers are suitable for use as the overlay. The structured layer, or referred to as the body layer, may be a single layer or multi-layer film. Illustrative examples of polymers that may be employed as the body layer film for flexible retroreflective articles include (1) fluorinated polymers such as poly(chlorotrifluoroethylene), poly(tetrafluoroethylene-co-hexafluoropropylene),

poly(tetrafluoroethylene-co-perfluoro(alkyl)vinylether), poly(vinylidene fluoride-co- hexafluoropropylene); (2) ionomeric ethylene copolymers poly(ethylene-co-methacrylic acid) with sodium or zinc ions such as SURLYN-8920 Brand and SURLYN-9910 Brand available from E.I. duPont Nemours, Wilmington, Del.; (3) low density polyethylenes such as low density polyethylene; linear low density polyethylene; and very low density polyethylene; plasticized vinyl halide polymers such as plasticized poly (viny chloride); (4) polyethylene copolymers including acid functional polymers such as poly(ethylene-co- acrylic acid) "EAA", poly (ethylene - co-methacrylic acid) "EMA", poly(ethylene-co-maleic acid), and poly(ethylene-co-fumaric acid); acrylic functional polymers such as poly(ethylene-co-alkylacrylates) where the alkyl group is methyl, ethyl, propyl, butyl, et cetera, or CH3 (CH2)n- where n is 0 to 12, and poly(ethylene-co- vinylacetate) "EVA"; and (5) (e.g.) aliphatic polyurethanes. The body layer is preferably an olefinic polymeric material, typically comprising at least 50 wt-% of an alkylene having 2 to 8 carbon atoms with ethylene and propylene being most commonly employed. Other body layers include for example poly(ethylene naphthalate), polycarbonate, poly(meth)acrylate (e.g., polymethyl methacrylate or "PMMA"), polyolefms (e.g., polypropylene or "PP"), polyesters (e.g., polyethylene terephthalate or "PET"), polyamides, polyimides, phenolic resins, cellulose diacetate, cellulose triacetate, polystyrene, styrene-acrylonitrile copolymers, cyclic olefin copolymers, epoxies, and the like.

Exemplary liners for protecting the exposed adhesive surfaces for use in the light redirecting articles of the present disclosure include silicone coated materials such as papers and polymeric films, including plastics. The liner base material may be single or multiple layer.

Specific examples include, polyester (for example polyethylene terephthalate), polyethylene, polypropylene (including cast and biaxially oriented polypropylene), and papers (including clay coated paper, polyethylene coated paper or a polyethylene coated poly(ethylene terephthalate) film. In some embodiments, wherein the light redirecting article is a retroreflective article 100, cube corner elements 112 are in the form of a tetrahedron or a pyramid. The dihedral angle between any two facets may vary depending on the properties desired in an application. In some embodiments (including the one shown in FIGS. 1A and IB when the article is a retroreflective article), the dihedral angle between any two facets is 90 degrees. In such embodiments, the facets are substantially perpendicular to one another (as in the corner of a room) and the optical element may be referred to as a cube corner. Alternatively, the dihedral angle between adjacent facets can deviate from 90° as described, for example, in U.S. Patent No. 4,775,219, the disclosure of which is incorporated in its entirety herein by reference. Alternatively, the optical elements in the retroreflective article can be truncated cube corners. The optical elements can be full cubes, truncated cubes, or preferred geometry (PG) cubes as described in, for example, U.S. Patent No. 7,422,334, the disclosure of which is incorporated in its entirety herein by reference.

For the structured layer 100 of FIGS. 1A and IB is shown as including overlay layer 1 18 and no land layer or land portion. A land layer may be defined as continuous layer of material coextensive with the microstructured elements 1 12 and composed of the same material. This construction may be desirable for flexible embodiments. Those of skill in the art will appreciate that structured layer 1 10 can include a land layer or land portion.

As is schematically shown in FIG. 2, one method of making at least some of the light redirecting articles 100 of the present disclosure involves placing barrier elements 134 onto a pressure sensitive adhesive material 132 and then laminating the resulting pressure sensitive adhesive layer 130 to a structured layer 1 10. The pressure sensitive adhesive layer 130 can be formed in a variety of ways including but not limited to the following exemplary methods. In one exemplary embodiment, the material(s) forming the barrier elements are printed onto the pressure sensitive adhesive. The method of printing can be, a non-contact method such as, for example, printing using an inkjet printer. The method of printing can be a contact printing method such as, for example, flexographic printing. In another exemplary embodiment, the material(s) forming the barrier elements are printed onto a flat release surface using, for example, an inkjet or screen printing method, and are then subsequently transferred from the flat release surface onto the pressure sensitive adhesive. In another exemplary embodiment, the material(s) forming the barrier elements are flood coated onto a microstructured adhesive surface (e.g. , a Comply liner manufactured by 3M Company of St. Paul, MN). The barrier elements are subsequently transferred from the microstructured liner to the pressure sensitive adhesive by, for example, lamination. The light redirecting article may then, optionally, be adhesively bonded to a substrate (e.g. , a window pane or an aluminum substrate) to form, for example, covered window or a license plate or sign. FIG. 3 shows an alternative exemplary light redirecting article 100 where the adhesive sealing layer 130 is a structured adhesive. Structured adhesive sealing layer 130 includes raised areas (a region that is raised relative to a surrounding region) of adhesive in a closed pattern, such as, for example, a hexagonal array. Barrier element 180 is included in the bottom of the well formed by the structured adhesive sealing layer 130.

Structured adhesive sealing layer 130 includes structured adhesive liner 140 and exposed adhesive layer 150. Structured adhesive sealing layer 130, when bonded to structured layer 110, defines low refractive index regions 138 that permit the portions of structured surface 114 adjacent to low refractive index regions 138 to direct incident light 150. As such, portions with that include microstructured elements 112 adjacent to low refractive index regions 138 are optically active. In contrast, portions with the structured adhesive layer 130 adjacent to microstructured elements 112 are optically inactive areas. Structured adhesive sealing layer 130 holds the entire construction together, thereby eliminating the need for a separate sealing layer and sealing process.

In some embodiments the adhesive sealing layer 130 includes at least one of, for example, a thermoplastic polymer, a cross-linkable material, and a radiation curable material. In some embodiments the adhesive sealing layer 130 comprises an adhesive, such as, for example, a heat activated adhesive, and/or a pressure sensitive adhesive or other material that can be formed using replication, heat embossing, extrusion replication, or the like. These constructions are

characterized by having an embossed, replicated, or a similarly formed adhesive sealing layer 130 laminated to the back of the structured layer 110.

The structured adhesive sealing layer 130 can be formed in several different ways. The structured adhesive layer can include, for example, multiple layers formed at the same time or can be built through repeated coating steps. One exemplary method starts with a flat film of adhesive, optionally on a carrier web. The adhesive is nipped between a flat roll and a roll with the required relief pattern. With the addition of temperature and pressure, the relief pattern is transferred to the adhesive. A second exemplary method requires a castable or extrudable adhesive material. A film of the adhesive is created by extruding the material onto a roll with the required relief pattern. When the adhesive material is removed from the roll, it retains the relief pattern associated with the roll. The structured adhesive layer is then laminated to the retroreflective layer.

The structured adhesive sealing layer 130 is then bonded to the structured layer 110 by nipping the two films together in a nip consisting of two flat rolls. With the addition of temperature and pressure, the films adhesively bond, creating pockets of air that form the low refractive index region.

The structured adhesive layers can include, for example, a thermoplastic polymer, a heat- activated adhesive, such as, for example, an acid/acrylate or anhydride/acrylate modified EVA's such as, for example, Bynel 3101, such as described in, for example, U.S. Patent No. 7,611,251, the entirety of which is herein incorporated by reference. The structured adhesive layers can include, for example, an acrylic PSA, or any other embossable material with adhesive

characteristics that will adhere to the corner cube elements. The interface between the seal film layer and the (e.g., cube-corner) microstructured layer typically include an adhesion promoting surface treatment. Various adhesion promoting surface treatments are known and include for example, mechanical roughening, chemical treatment, (air or inert gas such as nitrogen) corona treatment (such as described in US2006/0003178A1), plasma treatment, flame treatment, and actinic radiation.

In one embodiment, the light redirecting article 100 is a retroreflective article. The coefficient of retroreflection R A , can be modified depending on the properties desired in an application. In some embodiments, RA meets the ASTM D4956 - 07el standards at 0 degree and 90 degree orientation angles. In some embodiments, R A is in a range from about 5 cd/(lux m 2 ) to about 1500 cd/(lux m 2 ) when measured at 0.2 degree observation angle and +5 degree entrance angle according to ASTM E-810 test method or CIE 54.2; 2001 test method. In some

embodiments, such as in embodiments where the retroreflective article is used in a traffic control sign, a delineator, or a barricade, R A is at least about 330 cd/(lux m 2 ), or at least about 500 cd/(lux m 2 ), or at least about 700 cd/(lux m 2 ) as measured according to ASTM E-810 test method or CIE 54.2; 2001 test method at 0.2 degree observation angle and +5 degree entrance angle. In some embodiments, such as in motor vehicle related applications, RA is at least about 60 cd/(lux m 2 ), or at least about 80 cd/(lux m 2 ), or at least about 100 cd/(lux m 2 ) as measured according to ASTM E-810 test method or CIE 54.2; 2001 test method at 0.2 degree observation angle and +5 degree entrance angle.

Another way of measuring retroreflective performance involves measuring the fractional retroreflectance RT, which is explained in detail in ASTM E808-01. Fractional retroreflectance is the fraction of unidirectional flux illuminating a retroreflector that is received at observation angles less than a designated maximum value, otmax. Thus, RT represents the portion of light being returned within a prescribed maximum observation angle, otmax- In a manner consistent with ASTM E808-01, R T can be calculated as follows:

where a is the observation angle (expressed in radians), γ is the presentation angle (also expressed in radians), β is the entrance angle, and Ra is the conventional coefficient of retroreflection expressed in units of candelas per lux per square meter. For purposes of this application, RT refers to the fractional retroreflectance expressed as a decimal, and %RT refers to the fractional retroreflectance expressed as a percentage, i.e., %RT = RT X 100%. In either case, the fractional retroreflectance is unitless. As a graphical aid in understanding the observation angularity of a retroreflective sheeting, fractional retroreflectance may be plotted as a function of maximum observation angle, otmax. Such a plot is referred to herein as an Rr-otmax curve, or a %Rr-a ma x curve.

Another useful parameter for characterizing retroreflection is RT Slope, which can be defined as the change in RT for a small change or increment in the maximum observation angle, Aotmax. A related parameter, %RT Slope, can be defined as the change in %RT for a small change in maximum observation angle, Aotmax. Thus, RT Slope (or %RT Slope) represents the slope or rate of change of the RT-otmax curve (or %RT-otmax curve). For discrete data points these quantities may be estimated by calculating the difference in RT (or %RT) for two different maximum observation angles a ma x, and dividing that difference by the increment in maximum observation angle, Aotmax, expressed in radians. When Aotmax is expressed in radians, RT Slope (or %RT Slope) is the rate of change per radian. Alternatively and as used herein, when Aotmax is expressed in degrees, RT Slope (or %RT Slope) is the rate of change per degree in observation angle.

The equation given above for RT involves integrating the coefficient of retroreflection RA and other factors over all presentation angles (γ = -π to +π) and over a range of observation angles (a = 0 to a ma x). When dealing with discrete data points this integration can be performed using RA measured at discrete observation angle amax values (0.1 degrees) separated by increments Aa max .

In at least some embodiments of the present disclosure, the structured surface exhibits a total light return that is not less than about 5%, not less than 8%, not less than 10%, not less than 12%, not less 15% for incident visible light at an entrance angle of -4 degrees. In at least some of the embodiments of the present disclosure, the structured surface of the retroreflective article exhibits a coefficient of retroreflection RA that is not less than about 40 cd/(lux m2), not less than 50 cd/(lux m2), not less than 60 cd/(lux m2), not less than 70 cd/(lux m2), and not less than 80 cd/(lux m2) for an observation angle of 0.2 degrees and an entrance angle of -4 degrees.

With appropriate choice of barrier elements 134, size, structure, and/or spacing, the retroreflective articles of the present disclosure have a more uniform appearance than can be attained with conventional retroreflective articles including a sealing layer. Additionally, the retroreflective articles of the present disclosure do not require the inclusion or use of a sealing layer, reducing their cost.

Microsealed prismatic sheeting is especially suitable in applications such as license plates and graphics. The prismatic sheeting provides benefits such as significantly lower manufacturing cost, reduced cycle time, and elimination of wastes including especially solvents and CO2 when replacing glass bead sheeting. Furthermore, prismatic constructions return significantly increased light when compared to glass bead retroreflectors. Proper design also allows this light to be preferentially placed at the observation angles of particular importance to license plates, e.g., the range 1.0 to 4.0 degrees. Finally, micro sealed sheeting provides the brilliant whiteness and uniform appearance at close viewing distances needed in these product applications.

Exemplary retroreflective articles include, for example, retroreflective sheeting, retroreflective signage (including, for example, traffic control signs, street signs, highway signs, roadway signs, and the like), license plates, delineators, barricades, personal safety products, graphic sheeting, safety vest, vehicle graphics, and display signage.

The following examples describe some exemplary constructions of various embodiments of the retroreflective articles and methods of making the retroreflective articles described in the present disclosure. The following examples are intended to be illustrative, but are not intended to limit the scope of the present disclosure.

Although specific embodiments have been shown and described herein, it is understood that these embodiments are merely illustrative of the many possible specific arrangements that can be devised. Numerous and varied other arrangements can be devised in accordance with these principles by those of skill in the art without departing from the spirit and scope of the invention. Thus, the scope of the present invention should not be limited to the structures described in this application, but only by the structures described by the language of the claims and the equivalents of those structures.

DAYLIGHT REDIRECTING FILMS

In some embodiments, the light redirecting article is a DRF comprising suitable barrier elements to bond a daylight redirecting layer comprising microstructured prismatic elements to another film. The barrier elements of the present disclosure have sufficient structural integrity to substantially prevent flow of the adhesive into the microstructured prismatic elements, which would displace the air. U.S. Provisional Application No. 62/065,932 titled "Light Redirecting Film Constructions and Methods of Making Them" filed October 20, 2014, discloses constructions comprising a DRF and a second film bonded together using barrier elements and its disclosure is incorporated herein by reference in its entirety, to the extent its disclosure does not conflict with the present disclosure.

In some embodiments, cross-linkable monomers include mixtures of multifunctional acrylates, urethane acrylates, or epoxies. In some embodiments, the barrier elements comprise a plurality of inorganic nanoparticles. The inorganic nanoparticles can include, for example, silica, alumina, or Zirconia nanoparticles. In some embodiments, the nanoparticles have a mean diameter in a range from 1 to 200 nanometers, or 5 to 150 nanometers, or 5 to 125 nanometers. In illustrative embodiments, the nanoparticles can be "surface modified" such that the nanoparticles provide a stable dispersion in which the nanoparticles do not agglomerate after standing for a period of time, such as 24 hours, under ambient conditions.

In some embodiments, the barrier element traps a low refractive index material (such as air or aerogel) in the area adjacent the microstructured prismatic elements.

As explained before, the type of bonding disclosed and taught in this application between two films refers to bonding only via selected areas in the daylight redirecting film in order to preserve the daylight redirecting function (or a suitable function in other microstructured optical films) of the film. Because the presence of the adhesive contacting the microstructured prismatic elements substantially destroys the ability to redirect light, there is a natural balance between the size of the areas that effect the bonding (partially optically active areas) between the two films and the size of the areas that are optically active (able to redirect light). That is, as the size of the bonding area between the two films increases, the strength of the bond increases, which is beneficial, but there is also less area left to perform the daylight redirecting function of the original daylight redirecting film. Conversely, as the size of the daylight redirecting area increases, the higher amount of light is redirected, but the size of the area available for bonding decreases as does the strength of the bond between the two films.

The inventors of the present application have surprisingly created articles where the optically area is greater than 90% of the total available area but that still have suitable bond strength to maintain both films bonded for certain applications, including preparation of window films for commercial, residential, and even automotive applications.

Basic constructions

In one embodiment, the present disclosure is directed to an article comprising: a) a daylight redirecting layer comprising a first major surface and a second major surface; b) one or more barrier elements; and c) an adhesive layer; subject to the following conditions (see also Figures 4 to 6):

• the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area;

« the total surface area of the one or more barrier elements is greater than 60% of the daylight redirecting area;

• the adhesive layer comprises a first major surface and a second major surface;

• the first major surface of the adhesive layer has a first region and a second region;

• the first region of the first surface of the adhesive layer is in contact with one or more barrier elements; • the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

• the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and

• the article allows transmission of visible light.

In some embodiments, the article further includes a first substrate adjacent the second major surface of the adhesive layer. In certain embodiments, the first substrate includes a diffuser having an optical haze of 20 to 85 percent and an optical clarity of no more than 50 percent. In certain embodiments, the daylight redirecting layer comprises a daylight redirecting substrate, and the one or more microstructured prismatic elements are on the daylight redirecting substrate.

In other embodiments, to provide support to the microstructured prismatic elements, the constructions of this disclosure further comprise a first substrate adjacent the second major surface of the adhesive layer.

Diffusive layers coupled to daylight redirecting films

While one of the main incentives for using daylight redirecting films is energy savings, visual comfort needs to be taken in account. In a typical DRF construction, while most of the sunlight is directed upwards a fraction goes downwards. This downward light can cause glare for the occupants. In addition since the microstructured prismatic elements are typically linear and oriented horizontally the incoming rays are refracted/reflected mainly in the vertical direction. Sunlight is highly collimated with about 0.5 degree spread and appears as a solar disk. The effect of the daylight redirecting film is to spread this light vertically to form a solar column, such as that shown in Figure 3.

A variety of articles have been developed to redirect sunlight to provide illumination within rooms. For example, the following patents and patent applications describe various daylight redirecting films and daylight redirecting microstructures: US Patent Publication No. 2008/0291541, titled "Light Redirecting Solar Control Film", filed 05/23/2007 (Padiyath et al.) and pending US Patent Applications Nos. 61/287360, titled "Light Redirecting Constructions" filed 12/17/2009 (Padiyath et al), and 61/287354, titled "Light Redirecting Film Laminate" filed 12/17/2009 (Padiyath et al.); PCT Application Publication No. WO 2012/134787, titled "Hybrid Light Redirecting and Light Diffusing Constructions", filed 03/12/2012 (Padiyath et al.), US Patent No. 5,551,042, titled "Structured Films and Use Thereof for Daylight Illumination", issued 08/27/1996 (Lea, et al.), US Patent Publication No. 2014/021 1331, titled "Multiple Sequenced Daylight Redirecting Layers", filed 03/27/2014 (Padiyath et al.), US Patent Publication No. 2014/0198390, titled "Dual-sided Daylight Redirecting Film", filed 03/27/2014 (Padiyath, et al), US Patent Publication No. 2008/0292820, titled "Light Diffusing Solar Control Film", filed 05/23/2007 (Padiyath, et al.), US Patent No. 6,456,437, titled "Optical Sheets Suitable for Spreading Light", issued 09/24/2002 (Lea, et al.) The daylight redirecting films and daylight redirecting microstructures disclosed in the patents and patent applications in this paragraph are herein incorporated by reference. In general, any daylight redirecting film or layer, including those mentioned in this paragraph, and others known in the art, can be used in the constructions of this disclosure.

Both the total fraction of downward directed light and brightness of the solar column contribute to glare (visual discomfort). The brightness of the solar column depends on its angular spread. One solution to reduce glare is to introduce a diffuser layer in the optical path. The diffuser helps to spread out the solar column. In addition the diffuser layer provides more uniform ceiling illumination by diffusing the upward directed light. The diffuser layer spreads both the upward and downward directed light. The use of the diffuser layer reduces glare and the visibility of the solar column significantly.

A variety of diffusers have been developed and are known in the art. For example, the following patents and patent applications describe various type of diffusers: U.S. Patent

Publication No. 2014/0104689, titled "Hybrid Light Redirecting and Light Diffusing

Constructions, filed 12/05/2013, (Padiyath, et al); PCT Application Publication No. WO

2014/0931 19, titled "Brightness Enhancing Film with Embedded Diffuser", filed 12/05/2013, (Boyd et al.); U.S. Patent No. 6,288, 172, titled "Light Diffusing Adhesive", issued 09/1 1/2001 (Goetz, et al); PCT Application Publication No. WO 2013/158475, titled "Brightness

Enhancement Film with Substantially Non-imaging Embedded Diffuser", filed 04/12/2013, (Boyd, et al.) The diffusers disclosed in the patents and patent applications in this paragraph are herein incorporated by reference. In general, any diffuser or diffusive layer, including those mentioned in this paragraph, and others known in the art, can be used in the constructions of this disclosure.

U.S. Provisional Patent Application No. 62/186,871, titled "Light Redirecting Film Constructions and Methods of Making Same", filed concurrently with this application on June 30, 2015, is incorporated by reference herein in its entirety, to the extent its disclosure does not conflict with the disclosure of the instant application. U.S. Provisional Patent Application No.

62/186,871 discloses constructions where the article further includes a first substrate adjacent the second major surface of the adhesive layer. In certain embodiments discloses in that application, the first substrate includes a diffuser having an optical haze of 20 to 85 percent and an optical clarity of no more than 50 percent. One option to combine the effect of a diffuser layer with a daylight redirecting film is to adhere the daylight redirecting film to the window and mount the diffuser to an added pane. The present disclosure presents a solution where the difiuser layer and the daylight redirecting film are in a single construction.

In some embodiments, the diffusing properties can lie with the barrier elements, the adhesive, the window film adhesive, or any of the substrates that may be part of the daylight redirecting construction. In certain embodiments, the diffusing properties of any of the elements mentioned in the preceding sentence may be modified by introducing surface roughness, bulk diffusion, or using embedded diffusers.

In certain embodiments, the surface of a layer part of a daylight redirecting construction can be treated in such a manner that the layer diffuses visible light. Surface roughness to create diffusing properties in a layer can be accomplished by imparting a pattern on the surface of a layer that increases the angular spread of input light in a desired manner. Some methods used to impart such a pattern include embossing, replication, and coating.

In other embodiments, bulk diffusion can be accomplished by adding one or more diffusing agents to the window film adhesive. Diffusing agents can comprise opaque particles or beads. Examples of diffusing agents include: polymeric or inorganic particles and/or voids included in a layer.

In yet other embodiments, a substrate or a layer part of a daylight redirecting construction can contain embedded diffusers. An embedded diffuser layer is formed in between the daylight redirecting layer and the substrate. This layer may consist of a matrix with diffusing agents.

Alternatively the layer may be a surface diffuser layer consisting of a material with a refractive index sufficiently different from the daylight redirecting layer to obtain a desired level of diffusion. In other embodiments, various types of diffusers may also be used in combination.

Barrier elements

As mentioned before, one solution to form an assembly between a daylight redirecting film and a second film, such as a diffuser, involves "barrier elements," also called "passivation islands." In this approach a base film or liner is typically coated with a continuous layer of adhesive, for example a pressure sensitive adhesive (PSA), a hot melt, a thermoset adhesive, or a UV-curable adhesive. The adhesive layer is then printed with "barrier elements" or "islands" comprising a curable, non-tacky ink. Exposed regions of the adhesive remain tacky while the regions with the printed barrier elements are typically hard, and non-tacky. That is, the adhesive is passivated in those regions.

In one embodiment, the film with the printed barrier elements can be laminated to the daylight redirecting film. Lamination typically occurs under heat and pressure to allow the adhesive to flow into the microstructured prismatic elements. The two films are bonded in the regions with exposed, unprinted adhesive. FIG.7 is a schematic diagram of a typical process to bond a microstructured film to a second film.

The microstructured prismatic elements of a daylight redirecting film, typically formed from resins, require an air interface to function. The barrier elements prevent the adhesive from flowing into the microstructured prismatic elements in those regions and maintain an air interface. This situation can also be seen in Figure 7. The microstructured prismatic elements retain their optical performance in those areas. In the bonded regions the adhesive "wets" out the

microstructured prismatic elements and their optical performance (e.g., their ability to redirect light) may be degraded. Light incident on these areas may not be redirected but instead would pass right through the construction. This phenomenon is referred to as punch through. In one embodiment, punch through could be eliminated if an opaque adhesive is used in the areas where the adhesive is in contact with the microstructured prismatic elements.

The optical performance of the assembly may be modified by varying the ratio of the area of barrier elements to the area of exposed adhesive. As mentioned before, the adhesion between the two substrates, measured in peel strength, is proportional to the exposed adhesive area. The required peel strength is dependent on the specific application. The peel strength and the optical performance of the assembly must be balanced when determining the area exposed to adhesive. In addition, for applications such as daylight redirecting films, the aesthetics of the pattern should also be taken into account because, not only the size of the area exposed to adhesive, but also the location of those regions within the entire film can affect how a user perceives the construction.

In certain embodiments, the peel strength for the bond between a the layer bonded to the daylight redirecting layer, such as a first substrate, and the daylight redirecting layer is from 25 g/in to 2,000 g/in. In other embodiments, the peel strength for the bond between the first substrate and the daylight redirecting layer is greater than 300 g/in, or greater than 400 g/in, or greater than 500 g/in.

Typically, a film with structured layer (e.g., comprising microstructure prismatic elements) is laminated onto the barrier element-modified adhesive. As mentioned before, the barrier element aids to maintain the optical performance of the structured film, including its ability to refract light. The optical performance may be compromised if the structured layer penetrates into the barrier element or breaks through. This can result in light leakage, which may be manifested as glare in daylight redirecting films or a loss of brightness in retroreflected films.

In general, the barrier element is formed by applying a curable fluid material (referred to as an ink) onto the adhesive and curing (e.g. radiation curing, drying, chemically cross-linking) to reach a final state. The barrier element properties can be characterized and related to the optical performance of the total construction. In some embodiments, the barrier element diffuses visible light. As mentioned before, diffusion can be accomplished by creating surface diffusers, bulk diffusers, and embedded diffusers.

In other embodiments, the barrier elements can comprise one or more light stabilizers in order to enhance durability, for example in environments exposed to sunlight. These stabilizers can be grouped into the following categories: heat stabilizers, UV light stabilizers, and free-radical scavengers. Heat stabilizers are commercially available from Witco Corp., Greenwich, Conn, under the trade designation "Mark V 1923" and Ferro Corp., Polymer Additives Div., Walton Hills, Ohio under the trade designations "Synpron 1163", "Ferro 1237" and "Ferro 1720". In some embodiments, such heat stabilizers can be present in amounts ranging from 0.02 to 0.15 weight percent. In one embodiment, UV light stabilizers can be present in amounts ranging from 0.1 to 5 weight percent. Benzophenone-type UV-absorbers are commercially available from BASF Corp., Parsippany, N.J. under the trade designation "Uvinol 400"; Cytec Industries, West Patterson, N.J. under the trade designation "Cyasorb UV1164" and Ciba Specialty Chemicals, Tarrytown, N.Y., under the trade designations "Tinuvin 900", "Tinuvin 123" and "Tinuvin 1130". In certain embodiments, free-radical scavengers can be present in an amount from 0.05 to 0.25 weight percent. Nonlimiting examples of free-radical scavengers include hindered amine light stabilizer (HALS) compounds, hydroxylamines, sterically hindered phenols, and the like. HALS compounds are commercially available from Ciba Specialty Chemicals under the trade designation "Tinuvin 292" and Cytec Industries under the trade designation "Cyasorb UV3581."

Patterns for the barrier elements

In certain window film applications, such as those that contemplate a daylight redirecting film with a diffuser in a single construction, it may be desirable to minimize the visibility of the barrier elements. This may be achieved by judicious selection of the pattern in which the barrier elements are printed on the adhesive. Based on the inventors' experience, the following are some factors that affect pattern visibility based on considerations of the human visual system include:

• Minimizing barrier elements size;

• Avoiding long continuous edges or channels that have no interruptions; and

• Minimizing adhesive linewidths.

FIG. 8 shows three different sample patterns. The black areas represent the barrier elements while the white areas represent the exposed adhesive. The left panel in FIG. 8 represents a 1-dimmensional pattern consisting of lines. The lines may be oriented in any direction. When laminated to the structured film, this construction would only be fully sealed along two edges. A full seal may still be achieved by providing an exposed adhesive border or by edge-sealing the laminate. In general, the barrier elements can be laid out in a pattern chosen from a repeating 1- dimensional pattern, a repeating 2-dimensional pattern, and a random-looking 1- or 2-dimensional pattern.

A fully sealed construction may also be achieved by using a 2-dimensional pattern as shown in the center panel of FIG. 8. That pattern is an example of an ordered grid pattern consisting of a rectangular array of squares. The right panel in FIG. 8 shows random-looking polygons and may be less visible to the human eye compared to the center panel in FIG. 8 due to the breakup of the long straight edges present in pattern 9b. The edges in the 2- dimensional patterns may be straight or have curves. Other patterns could include random or ordered arrays of dots or decorative features.

The patterns in FIG. 8 may be characterized by two independent parameters:

• the pitch, which is meant to represent the center-to-center distance between

corresponding barrier elements. For random-looking structures, such as those in the right panel of FIG. 8, the pitch may represent the average distance between the centers of adjacent polygons. In certain embodiments, the average pitch in the construction is from 0.035 millimeters to 100 millimeters. In other embodiments, the average pitch in the article is from 0.1 millimeters to 10 millimeters, or from 0. 5 millimeters to 5 millimeters, or from 0.75 millimeters to 3 millimeters. In the inventors view, patterns with smaller pitches may be less visible; and

• Coverage, which is understood as the ratio of the total surface area of barrier element area to the total area. The total area refers to the area defined by the microstructured prismatic elements that form the daylight redirecting film. For that reason, in this disclosure, the total surface area is also called the daylight redirecting area. Patterns with higher coverage may have less "punch through" while patterns with lower coverage may have higher peel strength.

In some embodiments, the total surface area of the barrier elements is greater than 50% of the daylight redirecting area. In other embodiments, the total surface area of the barrier elements is greater than 60%, or greater than 65%, or greater than 70%, or greater than 75%, or greater than 80%, or greater than 85%, or greater than 90%, or greater than 95%, or greater than 98%,of the daylight redirecting area

The gap, which represents the exposed adhesive width between barrier elements may be deduced once the pitch and coverage are known. In some embodiments, the average gap in the construction is from 0.01 millimeters to 40 millimeters. In other embodiments, the average gap in the construction is from 0.05 mm to 20 mm; or from 0.1 mm to 20 mm; or from 0.2 mm to 20 mm. For reference, both patterns in the left and center panels in FIG. 8 have about 80% coverage. The "punch through" refers to glare due to incident light not being diffracted by the construction because the adhesive has fully or partially replaced air at the region immediately adjacent the microstructure elements. Punch through degrades redirection performance. Higher coverage patterns result in decreased punch through and bond strength between the films in the assembly.

Pattern visibility is also determined by feature sizes: size of the barrier elements (related to pattern pitch) and gap widths. The gap visibility is determined by the gap width and the viewing distance. Gap visibility may be estimated based on the resolution of the human visual system for a given viewing distance.

The patterns of barrier elements may be printed by direct or offset printing using a variety of known printing methods such as flexographic printing, gravure printing, screen printing, letterpress printing, lithographic printing, ink-jet printing, digitally controlled spraying, thermal printing, and combinations thereof. For direct printing methods, barrier elements printed by flexographic printing can have thickness up to 10 micrometers, by gravure printing, thickness can be up to 30 micrometers, and by screen printing, the thickness can be up to 500 um. The inks are typically printed in liquid form and then cured in place. Curing methods can include UV, E-beam, chemical, thermal curing, or cooling. Durability of the ink may be increased by additives such as light stabilizers.

The following table describes exemplary components of the curable compositions, which when cured, become barrier element.

mixture of cross-linker, with optional: diluent molecules, fillers, diffusing

materials, colorant , photoinitiator(s), and a solvent

compositio

has no or low solvent added (non-reactive species); in some

solvent embodiments, solvent no more than 10w% molecules with at least 2 acrylate groups per molecule (functionality

cross-linker is the number of acrylates per molecule) ^functionality is the average number of acryaltes on a molecule

chemistry may be urethane acrylates, acrylic acrylates,

acrylates polyester acrylates

acrylate molecules with a functionality of 1 or 2 and a viscosity of

less than 200 cPS

more typically less than 100 cPS; even more typically 3 to 50 cPS ioptically transparent thermoplastic resins, thermosetting resins, : polyester resins, polyuurethane resins, polystyrenee resins, ipolyamide resins, polyimide resins, melamine resins, phenol resins, isilicone resins, flurocarbon resins, and others. Addition of the filler a material which does not appreciably react with the other imust not make the viscosity of the composition out of range of a composition materials. Examples include resins, polymers, iprocessable composition. The filler also must not interfere with the inorganic materials. : required rheology for processing (e.g. splitting of a flexographic ink)

a material or treatment that will cause light to scatter. Examples: !See e.g, US 2008/0002256 . The particles used for barrier : particles which have index mismatching/matching properties with ielements are typically in the range of 200 nm to 8 microns, more

• Diffusing the other material(s) in the composition or roughening of the itypcially 500 to 4.5 microns US 2008/0002256 .is incorporated by. ; Materia : surface. preference herein for its disclosure of diffusing particles and compositions colorant : pigments, dyes

photoinitiator for UV curable systems only; typically 0.5 to 2.0 w%

not neccesaary for electron beam curable systems for example

^functionality of a mixture is the average number of acryaltes over 11 the molecules in the system. These are the groups where cross-

•compositio :lin iking takes place. The higher the number, in general, the more •functionality icross-linked the polymer matrix.

compositio

viscosity :The viscosity allows for the processing of the radiation curable DRF) 500 to 2500 cPS at room temperature ^composition with flexographic methods.

700 to 1500

800 to 1300

The optical properties of the ink (material used to print the barrier elements) may also be adjusted by modifying the ink's refractive index and/or its diffusing characteristics. The diffusing properties of the ink may be modified, for example by introducing surface roughness or bulk 5 diffusers. In some embodiments, a barrier element with diffusion is used to prepare a daylight redirecting construction with both clear view-through regions and daylight redirecting regions, such as the construction exemplified in FIG. 4.

In the embodiment of FIG. 4, the diffuser is integrated in the barrier elements. Regions in which the adhesive wets out the microstructures would provide clear view through areas.

0 Blurriness in these regions could be reduced by matching the refractive index of the microstructured prismatic elements to the refractive index of the adhesive. In certain

embodiments, clear view through regions could be desirable to provide visibility past the construction.

In certain embodiments whether the DRF is in a room-facing configuration or a sun-facing configuration, the crosslinked polymeric matrix of the barrier element is at least 1.6 microns thick. In one embodiment, the barrier element 134 is at least 1.75 microns thick. In one embodiment, the barrier element 134 is at least 2.0 microns thick. In one embodiment, the barrier element 134 is at least 3.0 microns thick. In other embodiments, the barrier element 134 is at least 3 microns thick. In other embodiments, the barrier element 134 is at least 5 microns thick. In other embodiments, the barrier element 134 is at least 7 microns thick. In other embodiments, the barrier element 134 is at least 8 microns thick. In other embodiments, the barrier element 134 is at least 10 microns thick.

DAYLIGHT REDIRECTING FILM CONFIGURATIONS

Room-Facing Configurations

A room-facing light redirecting assembly is shown in FIG. 5. In this embodiment, the redirecting film with the structures oriented towards the room is bonded to the cover/diffusing film using the barrier elements approach. The cover film may include diffusing properties depending on the optical performance of the daylight redirecting microstructure. The diffuser may be surface, bulk, or embedded diffuser. Diffusion may also be included in the adhesive or the barrier elements. The assembly may be mounted to a window or glazing using window film adhesive.

In certain embodiments, the present disclosure is directed to a film comprising an article, wherein the article comprises:

a daylight redirecting layer comprising a first major surface and a second major surface; wherein the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area;

one or more barrier elements;

wherein the total surface area of the one or more barrier elements is greater than 90% of the daylight redirecting area;

an adhesive layer;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first major surface of the adhesive layer is in contact with one or more barrier elements; wherein the second region of the first major surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

a first substrate adjacent the second major surface of the adhesive layer;

wherein the first substrate is a diffuser; and

a window film adhesive layer adjacent the second surface of the daylight redirecting layer; wherein the article allows transmission of visible light;

wherein the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and

wherein the film optionally further comprises a liner immediately adjacent the window film adhesive layer.

Sun-Facing Configurations

Two sun-facing daylight redirecting configurations are shown in FIG.6. In both embodiments, the microstructures are oriented towards the incoming sunlight. In this embodiment, the microstructure substrate may also have diffusing properties integrated into it. In certain embodiments, diffusive properties can be achieved by coating a surface diffuser on the substrate side opposing the microstructured prismatic elements. This substrate could also include bulk diffusion properties. In FIG. 6(a), the daylight redirecting substrate is bonded to a second substrate using the barrier elements approach. This substrate may have a window film adhesive coated on the opposing face to attach to a glazing.

In certain embodiments, the present disclosure is directed to a film comprising an article, wherein the article comprises:

a daylight redirecting layer comprising a first major surface and a second major surface; wherein the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area;

one or more barrier elements;

wherein the total surface area of the one or more barrier elements is greater than 90% of the daylight redirecting area;

an adhesive layer;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements; a diffuser adjacent the second major surface of the daylight redirecting layer;

a first substrate immediately adjacent the adhesive layer;

a window film adhesive layer immediately adjacent the first substrate;

wherein the article allows transmission of visible light;

wherein the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and

wherein the film optionally further comprises a liner immediately adjacent the window film adhesive layer.

In FIG 6(b), the second substrate is eliminated and the bonding adhesive is used both to laminate the barrier elements to the microstructured prismatic elements and to attach the assembly to the glazing. This configuration is potentially a simpler, lower cost, and thinner construction.

In certain embodiments, the present disclosure is directed to a film comprising an article, wherein the article comprises:

a daylight redirecting layer comprising a first major surface and a second major surface; wherein the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area;

one or more barrier elements;

wherein the total surface area of the one or more barrier elements is greater than 90% of the daylight redirecting area;

an adhesive layer;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

a diffuser adjacent the second major surface of the daylight redirecting layer;

wherein the article allows transmission of visible light;

wherein the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and

wherein the film optionally further comprises a liner immediately adjacent the adhesive layer. In some embodiments, the present disclosure is directed to a window comprising any of the films described above.

In certain embodiments, such as in the above room-facing and sun-facing constructions, diffusion may be incorporated in the substrates and/or adhesives. Diffusers may be surface, bulk, or embedded diffusers.

In some embodiments, the window film adhesive diffuses visible light. As mentioned before, diffusion can be accomplished by creating surface diffusers, bulk diffusers, and embedded diffusers.

In other embodiments, such as those involving DRFs, it may be useful to seal the edges of the daylight redirecting construction to prevent ingress of contaminants such as moisture and dirt. In those embodiments, one option to seal at least a portion of the edge is for the adhesive layer to fill the space between at least two immediately adjacent microstructured prismatic elements. In other embodiments, the entire edge can be sealed in this manner if the adhesive fills the space between the microstructured prismatic elements near the edge.

In some embodiments, the construction has a rectangular or square shape and the edge of one or more sides, up to all four sides, is sealed. In certain embodiments, the sealing can occur: by the use of a sealing agent, by the adhesive layer as described above, by using an edge sealing tape, or by using pressure, temperature, or some combination of both, including the use of a hot knife.

In other embodiments, the shape of the construction is circular or ellipsoidal and the edge of the construction is sealed all around. As mentioned before, the sealing can occur: by the use of a sealing agent, by the adhesive layer as described above, by using an edge sealing tape, or by using pressure, temperature, or some combination of both, including the use of a hot knife.

In other embodiments, the daylight redirecting construction can have: (a) a see-through region where the adhesive layer fills the space between adjacent microstructured prismatic elements such that no daylight redirecting occurs and light passes through the construction with no significant refraction, and (b) a daylight redirecting region as described in the embodiments disclosed above (that is, having barrier elements surrounded by the adhesive layer that bonds the daylight redirecting layer to a second layer or substrate). Figure 8 A shows an example of such an embodiment. In those embodiments the barrier elements within the active daylight redirecting region may optionally be diffusive, for example by comprising a diffusing agent or a surface diffuser.

In yet other embodiments constructions as described in the preceding paragraph may have a diffuser (bulk, surface, or embedded) on what originally was a see-through region. EXAMPLES

TEST METHODS:

Nanoindentation :

a) Sample Preparation: Samples of light directing articles were provided, wherein the light directing articles comprising a structured layer having a first side (i.e., front side) and an opposite second side (i.e., back side), an optional top layer adjacent the first side of the structured layer, and an adhesive sealing layer adjacent the second side of the structured layer. The adhesive sealing layer further included an adhesive layer and barrier elements disposed thereon. The barrier elements comprising a crosslinked polymeric matrix. The samples were prepared for testing by first separating the structured layer and top film from the adhesive sealing layer by attaching an adhesive tape to the adhesive sealing layer, dipping the construction in liquid nitrogen and pulling the construction apart. This resulted in a separation of the adhesive sealing layer from the structured surface and top film, and exposure of the barrier elements which were previously adjacent the structured surface. The barrier elements were then embedded in an epoxy adhesive (available under the trade designation Struers SpeciFix Resin mixed with a curing agent Struers SpeciFix-20 at a ratio of 7: 1 by weight), cured for 24 hours and subsequently cryomicrotomed at a temperature of -20°C using a LEICA EM UC6 from Leica Mycrosystems of Illinois, USA. The resulting multilayer construction comprised adhesive tape/adhesive layer/barrier elements/epoxy layer. Next, the multilayer construction was sectioned, exposing its cross-section.

b) Modulus of elasticity measurement: modulus of elasticity of barrier elements was measured using nanoindentation. A nanoindenter model G200 (from Keysight technologies) coupled to a DCM II transducer (from Keysight Technologies, Santa Rosa, CA), and a Berkovich diamond tip (commercially available from Microstar Technologies, Huntsville, TX) were used. Indenter calibrations were performed on a fused silica standard prior to each test to verify integrity of tip area function. All tests were conducted such that surface contact criteria was greater than 50 N/m at approach velocity of 40 nm/s. Load, displacement, and harmonic contact stiffness were obtained after contact using constant strain rate of 0.05 s "1 and command depth of 300 nm.

Maximum drift setpoint was set at 0.5 nm/s. Modulus and hardness were determined at depths from 30 nm to 200 nm. Elastic modulus was obtained using equations (1) and (2),

(2)

wherein Er corresponded to reduced modulus [N/m 2 ] or [GPa] measured directly by the instrument during experiment; S corresponded to contact stiffness [N/m]; vi corresponded to Poisson's ratio of sample material; Ei corresponded to the elastic modulus of diamond; and E corresponded to the elastic modulus of the sample material

Contact stiffness S, was measured by a technique in which a harmonic wave is superimposed over the DC signal that drives motion of the indenter, so that contact stiffness is measured continuously during loading using a harmonic frequency of 75 Hz, with 1 nanometer amplitude. Values for Elastic Modulus and Poisson ratio of diamond were taken as 1141 GPa and 0.07 respectively.

Hardness was determined the ratio of maximum load (Pmax) by contact area (A). Contact area was determined via the calibration tests in which contact area (tip area function) was found as a function of penetration depth.

MATERIALS

SR 420 3, 3, 5 - trimethylcyclohexyl acrylate Sartomer Americas

SR 217 Cycloaliphatic acrylate monomer Sartomer Americas

SR 506D Isobornyl Acrylate Sartomer Americas

E. I. du Pont de Nemours and

Ti0 2 Titanium dioxide

Company, Wellington, DE

2,2'azobis-(2-isobutyronitrile),

VAZO 64 E. I. du Pont

polymerization initiator

G77758-MS-6-10

BIS Bisamide crosslinker

Comparative Example A and Examples 1-6

Light directing articles comprising a structured layer including multiple microstructured elements were prepared as generally described in U.S. Patent No. 8,371,703 (Smith et al), the disclosure of which is incorporated herein by reference in its entirety. A master tool was prepared by cutting three grooves onto a machinable metal using a high precision diamond tool (such as "K&Y Diamond," manufactured and sold by Mooers of New York, U.S.A) to form microprisms. The tool comprised a 4.0 mil primary groove pitch and isosceles base triangles having base angles of 58 degrees.

The master tool was removed from the groove-forming machine. A first generation negative tooling was made from the master by nickel electroforming the master in a nickel sulfamate bath as generally described in U.S. Patent Nos. 4,478,769 (Pricone) and 5,156,863 (Pricone), both of which are incorporated herein by reference in their entirety. Multiple second generation negative tools containing microcube prism recesses were subsequently turned into an endless belt 20 feet (6.1 m) in length in the downweb direction and 3 feet (0.92 m) in the crossweb direction, as generally described in U.S. Patent No. 7,410,604 (Erickson), the disclosure of which is incorporated herein by reference in its entirety.

A polycarbonate resin (such as commercially available under the trade designation "MAKROLON 2407" by Mobay Corporation, Pennsylvania, U.S.A.) was cast at a temperature of 550°F (287.8°C) onto the endless belt, which was heated to 420° F (215.6°C). Coincident with filling the microcube recesses, additional polycarbonate was deposited in a continuous land layer above the endless belt with a thickness of approximately 102 micrometer (0.004 inch). The polycarbonate was then cooled with room temperature air, allowing the material to solidify and resulting in a microstructured layer. The microstructured layer was subsequently removed from the belt.

A radiation-polymerizable pressure sensitive adhesive (PSA) was prepared as described in U.S. Patent No. 5,804,610 (Hamer), incorporated herein by reference. The PSA composition was made by mixing 95 parts by weight isooctyl acrylate (IOA), 5 parts by weight acrylic acid (AA), 0.1 parts by weight of IRGACURE 651, 0.02 parts by weight of isooctylthioglycolate (IOTG), and 0.4 parts by weight of IRGANOX 1076. The PSA composition was placed into packages made of an ethylene vinyl acetate copolymer film of 0.0635 mm thickness (commercially available under the trade designation "VA-24" from Pliant Corporation, Dallas, TX) measuring approximately 10 centimeters by 5 centimeters and heat sealed. The PSA composition was then polymerized. After polymerization, the PSA composition was compounded in a twin screw extruder with 50wt% FORAL 85 tackifier and 18 wt% of a mixture of T1O 2 /EVA pigment and cast as a film onto a silicone coated release liner at a thickness of about 15 grains per 4 in by 6 in sample as generally described in U.S. Patent No. 5,804,610. The PSA film was then subjected to a radiation crosslinking step.

Barrier compositions were prepared by mixing the ingredients listed in Table 1, below, in the order provided. Mixing was conducted at room temperature and using a magnetic plate and stir bar for up to 12 hours to ensure adequate homogenization. In some embodiments, the mixture was heated to a temperature of about 60°C to ensure adequate homogenization. The amount of each ingredient is shown as weight percent (wt%) based on the total weight of the composition. Average functionality of each barrier composition was calculated as weighted average of the functionality of each ingredient in the composition. Modulus of elasticity was calculated according to the procedure described above. Functionality and modulus of elasticity are also reported in Table 1, wherein N/M as used herein means not measured. Table 1

Barrier elements of Comparative Example A and Examples 1-6 were prepared by selectively applying, respectively, Barrier Composition A and Barrier Compositions 1-6 onto the PSA film. The barrier elements were printed at a printing speed of 20 fpm using a flexographic printer comprising a printing plate made with 0.067 Cyrel DPR, commercially available from SGS Corporation. The plate was designed to print squares arranged in a grid pattern, wherein each square was 400 by 400 microns. Pitch (distance between the centers of each adjacent square) was 730 microns. The distance between each square (width) was 330 microns. Theoretical area coverage (% area) was calculated to be about (400/(400+330)) Λ 2=30%. The barrier elements were subsequently cured using UV H bulbs.

Light directing articles of Comparative Example A and Examples 1-6 were prepared by laminating the printed PSA films to the structured side of microstructured layers, prepared as described above.

Retroreflectivity (RA) was measured using a retroreflectometer (model RetroSign GR3, available from Delta Danish Electronics, Light & Acoustics, Denmark) at observation angles of 0.2, 0.5 and 1.0 degrees, entrance angle of -4 degrees, and orientation of 0 deg. Results are reported in cd/lux.m 2 as an average of four individual readings in Table 2, below.

Table 2

The light directing articles were subjected to additional pressure using a platen press at room temperature (25°C) or heated to temperature of about 49°C (120°F), using a pressure of about 5000 lbs (2268 kg) or about 15000 lbs (6804 kg), a compression area of about 1-3/8 in by 1-7/8 in or about 2.6 in 2 (about 17 cm 2 ) and a dwell time of 15 sec. Initial reflectivity at an observation angle of 0.2 (Rl), final reflectivity (after the platen press treatment) at an observation angle of 0.2 (R2), and retention (Rt) ((R2/R1)* 100) were measured and/or calculated. Results obtained with the platen press heated to 25°C are reported in Table 3, below. Results obtained with the platen press heated to about 49°C are reported in Table 4, below.

Table 3

Barrier elements of Examples 3, 4, and 5 were found to have improved adhesion of the adhesive sealing layers to the structured layer when compared to other barrier elements.

Examples 7-10

Light directing articles of Examples 7-10 were prepared as described in Comparative Example A and Examples 1-6, with the following exceptions: (i) a different PSA adhesive was used; (ii) a different printing pattern was used; and (iii) different barrier compositions were used. These differences are further described below.

The PSA composition used in Examples 7- 10 was a solution polymerized pressure sensitive adhesive polymer prepared by adding about 90 parts of isooctyl acrylate monomer and 10 parts of acrylic acid monomer to about 80 parts of a solvent mixture comprising 65% heptane and 35% acetone. A free-radical initiator (VAZO 64) was added at a level of about 0.08% as a percentage of the monomer mixture, and reacted at about 140°C for about 24 hours. The resulting polymer solution was cooled to about room temperature and diluted with a solvent mixture comprising 65% heptane and 35% acetone to about 40 percent solids. About 8 parts of a color concentrate comprising about 58 parts of titanium dioxide and 42 parts of "G7758-MS- 16-60" was added to about 100 parts of the solvent based polymer solution. About 8 parts of a bisamide crosslinker was added to about 100 parts of the polymer solution and the mixture was stirred well for about 15 minutes. The mixture was coated onto a silicone coated paper liner using a roll coater set up with a smoothing bar, adjusted to attain a dry coating weight of about 15 grains per 4 in by 6 in (10.2 cm by 15.2 cm). The wet adhesive was dried using a multi-zone oven with a line speed of about 60 fpm (18.3 m/min) and temperatures starting at 230°F (110°C) and ending at 270°F (132°C) to form an adhesive film on a silicone coated paper liner.

The printing pattern was designed to print squares arranged in a grid pattern, wherein each square was 420 by 420 microns. Pitch (distance between the centers of each adjacent square) was 600 microns. The distance between each square (width) was 180 microns. Theoretical area coverage (% area) was calculated to be about (420/(420+ 180)) Λ 2=49%.

Barrier Compositions 7-10 were used to prepare, respectively, Examples 7-10. The barrier compositions were prepared using the ingredients shown in Table 5, below, wherein amount of each ingredient is expressed as weight percent (wt%) based on the total weight of the composition. Functionality, hardness and modulus of each composition is also reported, wherein N/M means not measured.

Table 5

The light directing articles were subjected to additional pressure as described above, except that the platen press was heated to a temperature of about 110°F (43°C). Initial reflectivity at an observation angle of 0.2 (Rl), final reflectivity (after the platen press treatment) at an observation angle of 0.2 (R2), and retention (Rt) ((R2/R1)* 100) were measured and calculated. Results are reported in Table 6, below.

Table 6

DAYLIGHT REDIRECTING FILMS

These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims. All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, unless noted otherwise. Solvents and other reagents used were obtained from Sigma-Aldrich Chemical Company, Milwaukee, WI, unless otherwise noted.

Table 1 : Materials

Nanoindentation

Modulus of elasticity

The modulus of elasticity of barrier elements was measured using nanoindentation. A nanoindenter model G200 coupled to a DCM II transducer (Keysight Technologies, Santa Rosa, CA) and a Berkovich diamond tip (Microstar Technologies, Huntsville, TX) were used. Indenter calibrations were performed on a fused silica standard prior to each test to verify integrity of tip area function. All tests were conducted such that surface contact criteria was greater than 50 N/m at approach velocity of 40 nm/s. Load, displacement, and harmonic contact stiffness were

obtained after contact using constant strain rate of 0.05 s "1 and command depth of 300 nm.

Maximum drift setpoint was set at 0.5 nm/s. Modulus and hardness were determined at depths from 30 nm to 200 nm. Elastic modulus was obtained using equations (1) and (2),

wherein E r corresponded to reduced modulus [N/m 2 ] or [GPa] measured directly by the instrument during experiment; S corresponded to contact stiffness [N/m]; v, corresponded to Poisson's ratios of indenter; v corresponded to Poisson ratio of sample material; E, corresponded to the elastic modulus of diamond; and E corresponded to the elastic modulus of the sample material.

Contact stiffness

Contact stiffness S, was measured by a technique in which a harmonic wave is superimposed over the DC signal that drives motion of the indenter, so that contact stiffhess is measured continuously during loading using a harmonic frequency of 75 Hz, with 1 nanometer amplitude. Values for

Elastic Modulus and Poisson ratio of diamond were taken as 1141 GPa and 0.07 respectively.

Hardness

Hardness was determined by dividing the maximum load (Pmax) by the contact area (A). Contact area was determined via the calibration tests in which contact area (tip area function) was found as a function of penetration depth.

Ink compositions

The curable compositions (often referred to as inks) used to create the barrier elements were formulated by combining materials in the weight proportions provided in Table 2 until uniformly blended. Blending was normally done at room temperature, but formulations were heated at temperatures up to 60°C if necessary to obtain a uniform mixture.

Table 2: Barrier Element Ink Compositions (C.E. is a Comparative Example)

10 11 12 13 14 C.E.

Printing methods

Barrier elements were formed by applying fluid inks onto the surface of adhesive sheets and curing the inks with UV radiation.

The adhesive sheets were created by solution coating RD 2738 adhesive containing 0.1% of a bisamide cross-linker onto T50 silicone release liner to provide a dry film thickness of 3 mils.

Test samples of barrier elements were printed onto the adhesive sheets using a Flexiproof 100 test printer (RK PrintCoat Instruments Ltd., Royston, Hertfordshire, UK) outfitted with a 6.5 billion cubic microns per square inch (6.5 bcm), 8 bcm, or 10 bcm anilox roll. Printing was done using a print speed of 15 meters per minute and a random polygon stamp with a pitch of 1237 microns and a gap between barrier elements of 70 microns, yielding an area coverage of 89%. The inks were printed at 100% solids according to the formulations in Table 2. A Fusion UV Light Hammer UV curing system with an H bulb was used to cure the printed inks (Heraeus Noblelight America LLC, Gaithersburg, MD). Samples were cured at a line speed of 30 feet per minute under a nitrogen atmosphere using 100% UV power.

Barrier element analysis

The printed, cured barrier elements were then examined under magnification to evaluate whether the barrier elements were distinct and isolated from one another or had joined together prior to cure. The results are reported in Table 3 as 'well defined' or 'merged', respectively. Inks having a viscosity of at least 500 centipoise provided barrier elements that were well defined. Barrier elements that have partially merged are shown in Figure 9. In Figure 9, the gaps between barrier elements appear as linear structures that define the roughly hexagonal shapes of the barrier elements. It can be seen that some gaps are incomplete and others are missing entirely. In contrast, Figure 10 shows barrier elements where the gaps are continuous and the barrier elements are therefore well defined. Table 3: Ink viscosity and surface tension and results of visual inspection of printed and cured barrier elements.

To investigate the effect of ink composition and anilox roll volume, barrier elements were printed onto adhesive strips using the process described above in the combinations provided in Table 4. Table 4 also provides the average acrylate functionality (f) of each ink, and further provides the elastic modulus (as provided by the nanoindentation test method), thickness, and rigidity of the cured barrier elements. The rigidity of a barrier element composition (D) can be determined by using the plate equation:

Π— C *3

:L E is the tensile or Young ' s Modulus.

12(1 -n) t is the thickness, n is Poisson's ratio (0.3-0

The Young's storage modulus of a series of materials was determined with dynamic mechanical analysis of cast and cured films of the barrier element materials.

Table 4: Barrier element compositions used in the construction of daylight redirecting films. The Poisson's ratio used to calculate rigidity was n = 0.3.

Composition used volum acrylates/comp Nanoindentation elastic Barrier Rigidity Example e ω modulus at 23 °C element (D)

(bcm) (Gpa) thickness GPa

(microns) microns 3 at 23°C

27 3 6.5 1.9 2.5 1.5 1.00

28 4 8 2.4 2.58 1.6 1.26

29 4 10 2.4 2.58 2.02 2.53

30 5 8 3.8 3.42 1.62 1.73

31 1 8 4.12 no data 1.62 no data

32 2 8 3.39 3.29 1.62 1.67

Film lamination

Daylight Redirecting Films (DRFs) were made by laminating the adhesive layer coated with cured barrier elements to a film comprising microstructures according to the conditions in Table 5. The films were oriented in the laminate so that the barrier elements were adjacent to the

microstructures. The barrier elements were printed onto the adhesive and cured as described above using the ink and anilox roll specified in the barrier element compositions of Table 4. The

microstructured film was fabricated using the methods provided in United States Patent

Application No. 62/066,302, filed 20 October 2014, titled "Sun-Facing Light Redirecting Films with Reduced Glare", which is hereby incorporated by reference in its entirety. The specific

microstructure applied to the microstructured film was that provided in Example 2 of this patent application.

Table 5: DRF lamination conditions.

The laminated DRFs were inspected using microscopy to evaluate the degree of barrier element failure. For DRFs, the structured layer will direct light away from the field of view in the barrier element region. This makes that area appear dark or gray when the structured layer is separated from the adhesive by the action of the barrier elements. Conversely, in the gaps between barrier elements, light will not be redirected, and so the gaps appear relatively bright. When a barrier element is compromised, either by partial penetration or break-through of the adjacent

microstructure elements, light will be incompletely redirected, resulting in bright regions. Figure 11 shows a DRF with catastrophic barrier element failure, which appears as the fine vertical lines within individual barrier elements.

In Fig. 12, a cross section of a DRF laminate that was made using the ink of the Comparative Example (C.E.) is shown, in which the adhesive has flowed through a breach in a barrier element and filled the gap between adjacent microstructures. Because the light redirecting ability of the DRF laminate depends on maintaining the air gap above the microstructures, this adhesive ingress results in failure. Fig. 13 shows a photomicrograph of DRF Laminate Example 36, demonstrating a robust DRF construction. The individual barrier elements are distinct, have uniform optical properties, and do not show evidence of failure.

ADDITONAL EXEMPLARY EMBODIMENTS

The following non-limiting embodiments are provided as additional examples of articles of the present disclosure.

1. A light directing article, comprising:

a structured layer comprising multiple microstructured elements that is opposite a major surface;

an adhesive sealing layer having a first region and a second region wherein the second region is in contact with the structured layer; and

a barrier element at the first region;

wherein the first region with the barrier element and second region have sufficiently different properties to form a low refractive index layer between the adhesive sealing layer and the structured layer;

wherein the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity greater than 1.5 GPa and less than 4.4 GPa. 2. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness greater than 1.6 microns. 3. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness greater than 1.75 microns. 4. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness greater than 3.0 microns.

5. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked acrylate polymeric matrix.

6. The light directing article of any one of the preceding embodiments, wherein the crosslinked acrylate polymeric matrix is one of a urethane acrylate, acrylic acrylate, epoxy acrylate, or polyester acrylate. 7. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity of greater than 100 and less than 2000 cPS.

8. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a diluent;

a photoinitiator;

wherein the reaction product mixture has a viscosity of greater than 300 and less than 1500 cPS.

9. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a diluent;

a photoinitiator

wherein the reaction product mixture has a viscosity of greater than 400 and less than 1000 cPS. 10. The light directing article of any one of the preceding embodiments, wherein the microstructured elements comprise prisms.

11. The light directing article of any one of the preceding embodiments, is a retroreflective article and the microstructured elements comprise cube corners.

12. The light directing article of any one of the preceding embodiments, wherein the adhesive sealing layer comprises a pressure sensitive adhesive. 13. The light directing article of any one of the preceding embodiments, wherein the adhesive sealing layer comprises a structural adhesive.

14. The light directing article of any one of the preceding embodiments, wherein the structural adhesive is a hot melt adhesive.

15. The light directing article of any one of the preceding embodiments, wherein the pressure sensitive adhesive layer is in intimate contact with the microstructured elements of the structured layer. 16. The light directing article of any one of the preceding embodiments, wherein the adhesive sealing layer comprises a structured adhesive with legs and a base forming a well.

17. The light directing article of any one of the preceding embodiments, wherein the legs of the structured adhesive are in intimate contact with the microstructured elements of the structured layer and the barrier elements are in the well.

18. The light directing article of any one of the preceding embodiments, wherein the adhesive sealing layer is transparent. 19. The light directing article of any one of the preceding embodiments, wherein the adhesive sealing layer is opaque.

20. The light directing article of any one of the preceding embodiments, wherein the low refractive index layer includes at least one of air or a low refractive index material. 21. The light directing article of any one of the preceding embodiments, wherein the barrier element includes at least one of a resin, an ink, a dye, a pigment, an inorganic material, and a polymer. 22. The light directing article of any one of the preceding embodiments, further comprising a plurality of second regions that form a pattern.

23. The light directing article of any one of the preceding embodiments, further comprising a plurality of first regions that form a pattern.

24. The light directing article of any one of the preceding embodiments, wherein the pattern is one of an irregular pattern, a regular pattern, a grid, words, graphics, images, lines, and intersecting zones that form cells. 25. The light directing article of any one of the preceding embodiments, wherein the first region is surrounded by the second region.

26. The light directing article of any one of the preceding embodiments, wherein the barrier element has sufficient structural integrity to substantially prevent flow of the pressure sensitive adhesive into the low refractive index layer.

27. The light directing article of any one of the preceding embodiments, further comprising a plurality of first regions each with a barrier element that form a pattern. 28. The light directing article of any one of the preceding embodiments, further comprising a plurality of second regions that form a pattern.

29. The light directing article of any one of the preceding embodiments, wherein the structured surface at the first region is optically active.

30. The light directing article of any one of the preceding embodiments, where in at least about 30% of the structured surface is optically active.

31. The light directing article of claim 1, wherein the structured surface at the second region is optically inactive . 32. The light directing article of any one of the preceding embodiments, wherein the low refractive index layer is encapsulated by the barrier element. 33. The light directing article of any one of the preceding embodiments, including multiple optically active areas and multiple optically inactive areas and at least some of the optically inactive areas and optically active areas form a pattern.

34. A method of forming a light directing article, comprising:

providing a structured layer comprising multiple microstructured elements that is opposite a major surface; and

applying to an adhesive sealing layer a plurality of barrier elements that form first regions on the sealing layer;

crosslinking the barrier elements so that the barrier elements have a modulus of elasticity greater than 1.5 GPa and less than 4.4 GPa;

applying the adhesive sealing layer to the structured layer to form a low refractive index layer between the first regions of the adhesive sealing layer and the structured layer.

35. The method of any of the preceding embodiments directed to methods, wherein multiple barrier create a discrete first regions.

36. The method of any of the preceding embodiments directed to methods, wherein the adhesive sealing layer comprises a pressure sensitive adhesive layer. 37. The method of any of the preceding embodiments directed to methods, wherein the adhesive sealing layer comprises a structured adhesive layer.

38. The method of any of the preceding embodiments directed to methods, wherein a second major surface of the adhesive sealing layer is adjacent to a liner.

FURTHER EXEMPLARY EMBODIMENTS

1. An article comprising:

a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;

an adhesive layer; wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, and

wherein the article allows transmission of visible light.

An article comprising:

a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;

an adhesive layer;

wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

wherein the total surface area of the one or more barrier elements is greater than 60% of the light redirecting area;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, and

wherein the article allows transmission of visible light.

An article comprising:

a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;

an adhesive layer;

wherein the light redirecting layer comprises one or more microstructured elements on its first major surface defining a light redirecting area;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured elements;

wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa,

wherein the microstructured elements are retroreflective, and

wherein the article does not transmit visible light.

An article according to any of the preceding embodiments, wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa.

An article according to any of the preceding embodiments, wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.3 Gpa to 4.3 Gpa.

An article according to any of the preceding embodiments, wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.5 Gpa to 3.4 Gpa.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 1.6 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 1.75 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 2 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 3 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 5 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 7 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 8 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness of 10 microns or greater. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 10 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 8 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 7 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 5 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 3 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 2 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.75 microns to 10 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 8 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 7 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 5 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 3 microns. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 2 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 10 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 8 microns. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 7 microns. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 5 microns. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 3 microns. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 10 microns.

An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 8 microns. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 7 microns. An article according to any of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 5 microns. The article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked acrylate polymeric matrix.

The article of any one of the preceding embodiments, wherein the crosslinked acrylate polymeric matrix is one of a urethane acrylate, acrylic acrylate, epoxy acrylate, or polyester acrylate.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity of from 100 cPS to 2500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of: an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity of from 100 cPS to 2000 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity from 100 cPS to 1500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity from 100 cPS to 1000 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity from 300 cPS to 2500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity from 300 cPS to 2000 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator;

wherein the reaction product mixture has a viscosity from 300 cPS to 1500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 300 cPS to 1000 cPS. The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of: an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 400 cPS to 2500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 400 cPS to 2000 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 400 cPS to 1500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 400 cPS to 1000 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 500 cPS to 2500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 500 cPS to 2000 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 500 cPS to 1500 cPS. The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of: an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 500 cPS to 1000 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 800 cPS to 1500 cPS.

The article of any one of the preceding embodiments, wherein the barrier element comprises the reaction product of:

an acrylate polymer with at least two acrylate groups;

a photoinitiator

wherein the reaction product mixture has a viscosity from 900 cPS to 1300 cPS.

The article of any one of the preceding embodiments, wherein the microstructured elements comprise prisms.

The article of any one of the preceding embodiments, is a retroreflective article and the microstructured elements comprise cube corners.

The article of any one of the preceding embodiments, wherein the adhesive layer comprises a pressure sensitive adhesive.

The light redirecting article of any one of the preceding embodiments, wherein the adhesive layer comprises a structural adhesive.

The light redirecting article of any one of the preceding embodiments, wherein the structural adhesive is a hot melt adhesive.

The article of any one of the preceding embodiments, wherein the adhesive sealing layer comprises a structured adhesive with legs and a base forming a well.

The article of any one of the preceding embodiments, wherein the legs of the structured adhesive are in contact with the microstructured elements of the structured layer and the barrier elements are in the well.

The article of any one of the preceding embodiments, wherein the adhesive sealing layer is transparent.

The article of any one of the preceding embodiments, wherein the adhesive sealing layer is opaque.

The article of any one of the preceding embodiments, further comprising a plurality of second regions that form a pattern. The article of any one of the preceding embodiments, further comprising a plurality of first regions that form a pattern.

The article of any one of the preceding embodiments, wherein the pattern is one of an irregular pattern, a regular pattern, a grid, words, graphics, images, lines, and intersecting zones that form cells.

The article of any one of the preceding embodiments, wherein the first region is surrounded by the second region.

The article of any one of the preceding embodiments, wherein the barrier element has sufficient structural integrity to substantially prevent flow of the pressure sensitive adhesive into the low refractive index region.

The article of any one of the preceding embodiments, further comprising a plurality of first regions each with a barrier element that form a pattern.

The article of any one of the preceding embodiments, further comprising a plurality of second regions that form a pattern.

The article of any one of the preceding embodiments, wherein the structured surface at the first region is optically active.

The article of any one of the preceding embodiments, where in at least about 30% of the structured surface is optically active.

The article of embodiment 1, wherein the structured surface at the second region is optically inactive.

The article of any one of the preceding embodiments, wherein the low refractive index region is adjacent to the barrier element.

The article of any one of the preceding embodiments, including multiple optically active areas and multiple optically inactive areas and at least some of the optically inactive areas and optically active areas form a pattern.

A method of forming an article, comprising:

providing a structured layer comprising multiple microstructured elements that is opposite a major surface; and

applying to an adhesive layer a plurality of barrier elements that form first regions on the adhesive layer;

crosslinking the barrier elements so that the barrier elements have a modulus of elasticity from 1.5 Gpa to 4.4 Gpa;

applying the adhesive layer to the structured layer to define a low refractive index region between the first region of the adhesive sealing layer and the structured layer. 78. The method according to any of the preceding embodiments directed to methods of forming an article, wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa.

79. The method according to any of the preceding embodiments directed to methods of

forming an article, wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.3 Gpa to 4.3 Gpa.

80. The method according to any of the preceding embodiments directed to methods of

forming an article, wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.5 Gpa to 3.4 Gpa.

81. The method according to the preceding embodiments directed to methods of forming an article, wherein multiple barrier create a discrete first regions.

82. The method according to the preceding embodiments directed to methods of forming an article, wherein the adhesive sealing layer comprises a pressure sensitive adhesive layer.

83. The method according to the preceding embodiments directed to methods of forming an article, wherein the adhesive sealing layer comprises a structured adhesive layer.

84. The method according to the preceding embodiments directed to methods of forming an article, wherein a second major surface of the adhesive sealing layer is adjacent to a liner.

85. An article according to any of the preceding embodiments, wherein the light redirecting layer comprises a light redirecting substrate, and wherein the one or more microstructured prismatic elements are on the light redirecting substrate.

86. An article according to any of the preceding embodiments, wherein the total surface area of the one or more barrier elements is greater than 65% of the light redirecting area.

87. An article according to any of the preceding embodiments, wherein the total surface area of the one or more barrier elements is greater than 70% of the light redirecting area.

88. An article according to any of the preceding embodiments, wherein the total surface area of the one or more barrier elements is greater than 80% of the light redirecting area.

89. An article according to any of the preceding embodiments, wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area.

90. An article according to any of the preceding embodiments, wherein the total surface area of the one or more barrier elements is greater than 95% of the light redirecting area.

91. An article according to any of the preceding embodiments, wherein the total surface area of the one or more barrier elements is greater than 98% of the light redirecting area.

92. An article according to any of the preceding embodiments, wherein a barrier element diffuses visible light. 93. An article according to any of the preceding embodiments, wherein a barrier element comprises a diffusing agent.

94. An article according to any of the preceding embodiments, wherein a barrier element comprises particles as a diffusing agent

95. An article according to any of the preceding embodiments, wherein the adhesive layer comprises a diffusing agent.

96. An article according to any of the preceding embodiments, wherein the adhesive layer comprises particles as a diffusing agent.

97. An article according to any of the preceding embodiments, wherein the window film adhesive layer comprises a diffusing agent.

98. An article according to any of the preceding embodiments, wherein the window film adhesive layer comprises particles as a diffusing agent.

99. An article according to any of the preceding embodiments, wherein the surface roughness of a barrier element provides visible-light diffusing properties to the barrier element.

100. An article according to any of the preceding embodiments, wherein a barrier element comprises one or more light stabilizers.

101. An article according to any of the preceding embodiments, wherein the material of the barrier elements has been cured using UV radiation or heat.

102. An article according to any of the preceding embodiments, wherein the barrier elements are laid out in a pattern chosen from a repeating 1 -dimensional pattern, a repeating 2- dimensional pattern, and a random-looking 1- or 2-dimensional pattern.

103. An article according to any of the preceding embodiments, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is from 0.035 millimeters to 100 millimeters.

104. An article according to any of the preceding embodiments, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is from 0.1 millimeters to 10 millimeters.

105. An article according to any of the preceding embodiments, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is from 0. 5 millimeters to 5 millimeters.

106. An article according to any of the preceding embodiments, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is from 0.75 millimeters to 3 millimeters. 107. An article according to any of the preceding embodiments, wherein the width of a channel of the second region of the first surface of the adhesive layer defines a gap; and wherein the average gap in the article is from 0.01 millimeters to 40 millimeters.

108. An article according to any of the preceding embodiments, wherein the adhesive in the adhesive layer is chosen from a pressure sensitive adhesive, a thermoset adhesive, hot melt adhesive, and a UV-curable adhesive.

109. An article according to any of the preceding embodiments, wherein the adhesive in the adhesive layer is a pressure sensitive adhesive.

110. An article according to any of the preceding embodiments, wherein the adhesive layer comprises one or more UV stabilizers.

111. An article according to any of the preceding embodiments, wherein the refractive index of the material of the microstructured prismatic elements matches the refractive index of the adhesive layer.

112. An article according to any of the preceding embodiments, further comprising a first substrate adjacent the second major surface of the adhesive layer.

113. An article according to any of the preceding embodiments, wherein the peel strength for the bond between the first substrate and the light redirecting layer is from 25 g/in to 2,000 g/in.

114. An article according to any of the preceding embodiments, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 300 g/in.

115. An article according to any of the preceding embodiments, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 400 g/in.

116. An article according to any of the preceding embodiments, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 500 g/in.

117. An article according to any of the preceding embodiments, wherein the second region of the first major surface of the adhesive layer fills the space between at least two immediately adjacent microstructured prismatic elements.

118. An article according to any of the preceding embodiments, wherein the article has a

rectangular or square shape and the edge of all four sides is sealed.

119. An article according to any of the preceding embodiments, wherein the article has a

rectangular or square shape and the edge of at least one side is sealed by the adhesive layer.

120. An article according to any of the preceding embodiments, wherein the article has a

rectangular or square shape and the edge of at least one side is sealed with a sealing agent. 121. An article according to any of the preceding embodiments, wherein the article has a rectangular or square shape and the edge of at least one side is sealed with an edge sealing tape.

122. An article according to any of the preceding embodiments, wherein the article has a rectangular or square shape and the edge of at least one side is sealed using pressure, temperature, or a combination of both pressure and temperature.

123. An article according to any of the preceding embodiments, wherein the article has a circular or ellipsoidal shape and the edge of the article is sealed all around.

124. An article according to any of the preceding embodiments, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed by the adhesive layer.

125. An article according to any of the preceding embodiments, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed with a sealing agent.

126. An article according to any of the preceding embodiments, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed with an edge sealing tape.

127. An article according to any of the preceding embodiments, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed using pressure, temperature, or a combination of both pressure and temperature.

128. A film comprising an article according to any of the preceding embodiments,

wherein the article further comprises a second substrate adjacent the second major surface of the adhesive layer;

wherein the article further comprises a window film adhesive layer adjacent the second major surface of the light redirecting layer; and

wherein the article optionally further comprises a liner adjacent the window film adhesive layer.

129. A film according to embodiment 10, further comprising a diffuser adjacent the second substrate.

130. A film according to embodiment 10, further wherein the second substrate comprises a diffuser.

131. A window comprising a film as claimed as in any of the preceding embodiments directed to a film, wherein the window further comprises a glazing immediately adjacent the window film adhesive layer. 132. A film comprising an article according to any of the preceding embodiments directed to an article,

wherein the article further comprises a second substrate adjacent the second major surface of the light redirecting layer;

wherein the article optionally further comprises a liner adjacent the adhesive layer.

133. A film according to embodiment Error! Reference source not found., further comprising a diffuser adjacent the second substrate.

134. A film according to embodiment Error! Reference source not found., further wherein the second substrate comprises a diffuser.

135. A window comprising a film as claimed as in any of embodiments Error! Reference source not found, to Error! Reference source not found., wherein the window further comprises a glazing immediately adjacent the adhesive layer.

136. A film comprising an article according to any of the preceding embodiments directed to an article, wherein the article further comprises:

• a second substrate adjacent the second major surface of the light redirecting layer

• a third substrate immediately adjacent the adhesive layer;

• a window film adhesive layer immediately adjacent the third substrate; and

• optionally a liner adjacent the window film adhesive layer.

137. A film according to embodiment Error! Reference source not found., further comprising a diffuser adjacent the second substrate.

138. A film according to embodiment Error! Reference source not found., further wherein the second substrate comprises a diffuser.

139. A window comprising a film as claimed as in any of embodiments Error! Reference source not found, to Error! Reference source not found., wherein the window further comprises a glazing immediately adjacent the window film adhesive layer.

140. A film according to any of the preceding embodiments directed to films that comprise a diffuser, wherein the diffuser is chosen from bulk diffusers, surface diffusers, and embedded diffusers or combinations thereof.

141. A window according to any of the preceding embodiments directed to windows that comprise a diffuser, wherein the diffuser is chosen from bulk diffusers, surface diffusers, and embedded diffusers or combinations thereof.

142. A film comprising an article,

wherein the article comprises:

a light redirecting layer comprising a first major surface and a second major surface; wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

one or more barrier elements;

wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area;

an adhesive layer;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

a first substrate adjacent the second major surface of the adhesive layer;

wherein the first substrate comprises a diffuser; and

a window film adhesive layer adjacent the second surface of the light redirecting layer; wherein the article allows transmission of visible light;

wherein the film optionally further comprises a liner immediately adjacent the window film adhesive layer.

A film comprising an article,

wherein the article comprises:

a light redirecting layer comprising a first major surface and a second major surface; wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

one or more barrier elements;

wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area;

an adhesive layer;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

a diffuser adjacent the second major surface of the light redirecting layer;

a first substrate immediately adjacent the adhesive layer; a window film adhesive layer immediately adjacent the first substrate;

wherein the article allows transmission of visible light;

wherein the film optionally further comprises a liner immediately adjacent the window film adhesive layer.

A film comprising an article,

wherein the article comprises:

a light redirecting layer comprising a first major surface and a second major surface; wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

one or more barrier elements;

wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area;

an adhesive layer;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

a diffuser adjacent the second major surface of the light redirecting layer;

wherein the article allows transmission of visible light;

wherein the film optionally further comprises a liner immediately adjacent the adhesive layer.

145. An article comprising:

a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;

an adhesive layer;

wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

wherein the total surface area of the one or more barrier elements in at least a portion of the article defined as a light redirecting region is greater than 60% of the light redirecting area;

wherein the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

wherein the article allows transmission of visible light.

An article according to embodiment Error! Reference source not found., wherein portions of the light redirecting area that are not part of the light redirecting region are clear enough to allow a user to see through the construction.

A method of making an article comprising:

providing a first substrate having a first major surface and a second major surface opposite the first major surface;

applying an adhesive layer to the first major surface of the first substrate;

wherein the adhesive layer has a first major surface and a second major surface opposite the first major surface; and wherein the second major surface of the adhesive layer is immediately adjacent the first major surface of the first substrate;

printing one or more barrier elements on the first major surface of the adhesive layer; setting the one or more barrier elements;

laminating a light redirecting layer on the first major surface of the adhesive layer;

wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;

wherein the total surface area of the one or more barrier elements is greater than 60% of the light redirecting area;

wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with the one or more barrier elements;

wherein the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;

wherein the article allows transmission of visible light.

A method according to embodiment 13, wherein printing of the one or more barrier elements occurs by direct or offset printing and by process chosen from flexographic printing, gravure printing, screen printing, letterpress printing, lithographic printing, ink- jet printing, digitally controlled spraying, thermal printing, and combinations thereof. A method according to any of the preceding embodiments directed to methods, wherein setting the one or more barrier elements occurs by a method chosen from UV -radiation curing, e-beam -radiation curing, thermal curing, chemical curing, and cooling. 150. A method according to any of the preceding embodiments directed to methods, wherein the first substrate comprises a diffuser chosen from bulk diffusers, surface diffusers, and embedded diffusers or combinations thereof.

151. A method according to any of the preceding embodiments directed to methods, wherein the light redirecting layer comprises a light redirecting substrate, and wherein the one or more microstructured prismatic elements are on the light redirecting substrate.

152. A method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 65% of the light redirecting area.

153. A method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 70% of the light redirecting area.

154. A method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 80% of the light redirecting area.

155. A method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area.

156. A method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 95% of the light redirecting area.

157. A method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 98% of the light redirecting area.

158. A method according to any of the preceding embodiments directed to methods, wherein a barrier element diffuses visible light.

159. A method according to any of the preceding embodiments directed to methods, wherein a barrier element comprises a diffusing agent.

160. A method according to any of the preceding embodiments directed to methods, wherein a barrier element comprises particles as a diffusing agent

161. A method according to any of the preceding embodiments directed to methods, wherein the adhesive layer comprises a diffusing agent.

162. A method according to any of the preceding embodiments directed to methods, wherein the adhesive layer comprises particles as a diffusing agent. 163. A method according to any of the preceding embodiments directed to methods, wherein the window film adhesive layer comprises a diffusing agent.

164. A method according to any of the preceding embodiments directed to methods, wherein the window film adhesive layer comprises particles as a diffusing agent.

165. A method according to any of the preceding embodiments directed to methods, wherein the surface roughness of a barrier element provides visible-light diffusing properties to the barrier element.

166. A method according to any of the preceding embodiments directed to methods, wherein a barrier element comprises one or more light stabilizers.

167. A method according to any of the preceding embodiments directed to methods, wherein the material of the barrier elements has been cured using UV radiation or heat.

168. A method according to any of the preceding embodiments directed to methods, wherein the barrier elements are laid out in a pattern chosen from a repeating 1 -dimensional pattern, a repeating 2-dimensional pattern, and a random-looking 1- or 2-dimensional pattern.

169. A method according to any of the preceding embodiments directed to methods, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is between 0.035 millimeters and 100 millimeters.

170. A method according to any of the preceding embodiments directed to methods, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is between 0.1 millimeters and 10 millimeters.

171. A method according to any of the preceding embodiments directed to methods, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is between 0. 5 millimeters and 5 millimeters.

172. A method according to any of the preceding embodiments directed to methods, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is between 0.75 millimeters and 3 millimeters.

173. A method according to any of the preceding embodiments directed to methods, wherein the width of a channel of the second region of the first surface of the adhesive layer defines a gap; and wherein the average gap in the article is between 0.01 millimeters and 40 millimeters.

174. A method according to any of the preceding embodiments directed to methods, wherein the adhesive in the adhesive layer is chosen from a pressure sensitive adhesive, a thermoset adhesive, hot melt adhesive, and a UV-curable adhesive. A method according to any of the preceding embodiments directed to methods, wherein the adhesive in the adhesive layer is a pressure sensitive adhesive.

A method according to any of the preceding embodiments directed to methods, wherein the adhesive layer comprises one or more UV stabilizers.

A method according to any of the preceding embodiments directed to methods, wherein the refractive index of the material of the microstructured prismatic elements matches the refractive index of the adhesive layer.

A method according to any of the preceding embodiments directed to methods, further comprising a first substrate adjacent the second major surface of the adhesive layer. A method according to any of the preceding embodiments directed to methods, wherein the peel strength for the bond between the first substrate and the light redirecting layer is from 25 g/in to 2,000 g/in.

A method according to any of the preceding embodiments directed to methods, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 300 g/in.

A method according to any of the preceding embodiments directed to methods, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 400 g/in.

A method according to any of the preceding embodiments directed to methods, wherein the peel strength for the bond between the first substrate and the light redirecting layer is greater than 500 g/in.

A method according to any of the preceding embodiments directed to methods, wherein the second region of the first major surface of the adhesive layer fills the space between at least two immediately adjacent microstructured prismatic elements.

A method according to any of the preceding embodiments directed to methods, wherein the article has a rectangular or square shape and the edge of all four sides is sealed.

A method according to any of the preceding embodiments directed to methods, wherein the article has a rectangular or square shape and the edge of at least one side is sealed by the adhesive layer.

A method according to any of the preceding embodiments directed to methods, wherein the article has a rectangular or square shape and the edge of at least one side is sealed with a sealing agent.

A method according to any of the preceding embodiments directed to methods, wherein the article has a rectangular or square shape and the edge of at least one side is sealed with an edge sealing tape. 188. A method according to any of the preceding embodiments directed to methods, wherein the article has a rectangular or square shape and the edge of at least one side is thermally sealed.

189. A method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and the edge of the article is sealed all around.

190. A method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed by the adhesive layer.

191. A method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed with a sealing agent.

192. A method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed with an edge sealing tape.

193. A method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is thermally sealed.




 
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