Field of the Disclosure

This disclosure relates to curable ink compositions which have a low dielectric constant relative to typically polymeric compositions, are printable, and can be used to form articles.

Background

Increasingly, optical devices are becoming more complicated and involve more and more functional layers. As light travels through the layers of the optical device, the light can be altered by the layers in a wide variety of ways. For example, light can be reflected, refracted or absorbed. In many cases, layers that are included in optical devices for non- optical reasons adversely affect the optical properties. For example, if a support layer is included that is not optically clear, the absorption of light by the non-optically support layer can adversely affect the light transmission of the entire device.

Multi-layer optical and electronic devices utilize a wide array of different materials with different properties. Adding to the complexity of the layers used in these devices is that often layers have to fulfill more than one function within an article. For example, a single material layer may be called upon to function as a barrier layer but must also provide exact spacing between layers and also be optically clear so as to not deleteriously affect the optical properties.

It has become increasingly difficult to prepare organic polymeric compositions which have suitable optical properties and yet retain the desirable features of organic polymers, features such as ease of processing, flexibility, and the like.

Summary

This disclosure includes curable ink composition, articles, and methods of preparing articles. In some embodiments, the curable ink composition comprises a first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms, a crosslinking monomer, and at least one initiator. The curable ink composition is solvent free and inkjet printable, having a viscosity of less than 30 centipoise at a temperature of from room temperature to less than 60°C. Upon curing, a non-crystalline, optically clear layer with a dielectric constant of less than or equal to 3.0 at 1 megaHertz is formed.

Also disclosed are articles. In some embodiments, the article comprises a substrate with a first major surface and a second major surface; a cured organic layer with a first major surface and a second major surface, where the first major surface of the cured organic layer is adjacent to at least a portion of the second major surface of the substrate. The cured organic layer comprises a crosslinked (meth)acrylate-based layer having a thickness of from 1-50 micrometers, and has a dielectric constant of 3.0 or less at 1 megaHertz, is non-crystalline, and optically clear.

Methods of preparing articles are also disclosed. In some embodiments, the method of preparing an article comprises providing a substrate with a first major surface and a second major surface, providing a curable ink composition, disposing the curable ink composition on at least a portion of the second major surface of the substrate to form a curable layer, curing the curable layer to form a cured organic layer having a first major surface and a second major surface, where the first major surface of the cured organic layer is adjacent to the second major surface of the substrate, and where the cured organic layer has a thickness of from 1-50 micrometers. The curable ink composition comprises a first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms, a crosslinking monomer, and at least one initiator. The curable ink composition is solvent free and inkjet printable, having a viscosity of less than 30 centipoise at a temperature of from room temperature to less than 60°C. When printed and cured, a layer formed from the curable ink composition has a dielectric constant of 3.0 or less at 1 megaHertz, and is non-crystalline and optically clear.

Brief Description of the Drawings

The present application may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings.

Figure 1 shows a cross sectional view of an embodiment of an article of this disclosure. Figure 2 shows a cross-sectional view of an embodiment of another article of this disclosure.

Figure 3 shows the ink droplet image analysis from Example 28.

In the following description of the illustrated embodiments, reference is made to the accompanying drawings, in which is shown by way of illustration, various embodiments in which the disclosure may be practiced. It is to be understood that the embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure. The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

Detailed Description

The increased complexity of optical devices places increasingly difficult requirements upon the materials used in them. In particular, organic polymeric materials have found widespread use in optical devices, but increasingly stringent requirements are being placed upon these polymeric materials.

For example, thin organic polymeric films are desirable for a wide range of uses in optical devices, as adhesives, protective layers, spacer layers, and the like. As articles have become more complex, the physical demands upon these layers have increased. For example, as optical devices have become more compact, and at the same time often include more layers, there has been an increasing need for thinner layers. At the same time, since the layers are thinner, the layers also need to be more precise. For example, a thin spacer layer (of 1 micrometer thickness) needs to be level and free of gaps and holes in order to provide the proper spacing function. This requires deposition of the organic layer in a precise and consistent manner.

One function that thin spacer layers are called upon to fulfill in multilayer optical and electronic devices is electrical insulation, in order to electrically isolate a layer or series of layers from other nearby layers. Therefore, it is desirable to have thin layers of organic polymeric materials that have a low dielectric constant. In this context, a low dielectric constant material is one which has a dielectric constant of 3.0 or less at 1 megaHertz. This function also requires precision in the formation of the layers as the presence of gaps or pinholes can destroy the insulating ability of the layer.

Additionally, not only do these layers have to fulfill their physical role (adhesion, protection, spacing, and the like) they must also provide the requisite optical properties. Among the properties that are becoming increasingly important is optical clarity.

For example, thin film encapsulation (TFE) layers are used to prevent air and moisture ingress into the OLED device. The TFE is typically composed of alternating layers of inorganic and organic materials (Chwang, Applied Physics Letters 83, 413 (2003)). The function of the inorganic layers is to block the ingress of air and moisture into the OLED device. The functions of the organic layers are twofold: 1) to planarize the substrate and present a smooth interface for the deposition of the inorganic layer; and 2) to decouple any defects (pinholes, micro-cracks) that may occur in the inorganic layers on either side of the organic layer. The organic layer can be thought of as a buffer layer that is critical for the success of the inorganic layer barrier function.

Among the methods that have been developed to provide a precise and consistent deposition of organic polymeric material are printing techniques. In printing techniques, a polymer or a curable composition that upon curing forms a polymer, is printed onto a substrate surface to form a layer. In the case of printable polymers, typically solvents are added to make the polymer a solution or dispersion capable of being printed. When polymers are used, typically a drying step is necessary after printing to produce the desired polymeric layer. In the case of curable compositions that upon curing form polymers, the curable compositions may or may not include a solvent. The curable composition is then cured, typically either with the application of heat or radiation (such as ETV light) and if a solvent is used the layer may also be dried. A wide variety of printing techniques can be used, with inkjet printing being particularly desirable because of the excellent precision of inkjet printing.

As was mentioned above, an example of an optical device that utilizes thin film layers are OLED (organic light-emitting diode) devices. In particular, the organic light- emitting devices are susceptible to degradation from the permeation of certain liquids and gases, such as water vapor and oxygen. To reduce permeability to these liquids and gases, barrier coatings are applied to the OLED device. Typically, these barrier coatings are not used alone, rather a barrier stack is used which can include multiple dyads. Dyads are two layer structures that include a barrier layer and decoupling layer. The decoupling layer provides a planarized and/or smooth surface for the deposition of the inorganic barrier layer.

In this disclosure, curable inks that are capable of being printed are described which have a number of traits that make them suitable for the formation of layers within multilayer optical devices. Many of these traits are contradictory to each other, and therefore it is unexpected that an ink composition can have these contradictory traits. For example, the formulations, when cured have a dielectric constant of 3.0 or less at 1 megaHertz. In order to achieve this low dielectric constant, monomers that are branched hydrocarbons, often highly branched hydrocarbons, with relatively long chains are used, and these branched, long chain monomers have a relatively high viscosity. However, in order to be printable, especially inkjet printable, the viscosity cannot be too high. Often this viscosity problem can be overcome through the use of solvents to dilute the monomer mixtures and thus reduce their viscosity. The use of solvents is not suitable for the inks of the present disclosure because it is undesirable to have to dry the prepared coatings, and drying is known to affect coatings by decreasing the thickness and drying can also adversely affect the surface smoothness and may also create defects in the coating. In many applications for optical devices, it is desired that the coatings be precise, that is to say that they do not lose thickness or smoothness upon drying. Therefore, the inks of the present disclosure are“100% solids”, meaning that they do not contain volatile solvents and that all of the mass that is deposited on a surface remains there, no volatile mass is lost from the coating. Another technique that can be used to decrease the viscosity of inks is to raise the temperature of the ink. However, this is also not suitable for the inks of the present disclosure because the inks are often applied to substrates that are either thermally sensitive or are kept at ambient temperature and therefore coating a hot ink onto the room temperature substrate can cause defects in the coating. These defects can come about either from a lack of proper wetting on the substrate surface or from other inconsistencies that form a non-uniform coating.

Therefore, the curable compositions of the present disclosure are useful as inks, meaning that they are capable of being printed by for example inkjet printing techniques without the use of solvents at a temperature of from room temperature to about 60°C, or even room temperature to 35°C. Typically, the printable curable composition has a viscosity at these temperatures of 30 centipoise or less. In some embodiments, the viscosity is from 1-20 centipoise at room temperature.

The curable ink composition, when coated and cured to form a cured organic layer, produces a cured organic layer that has a dielectric constant of 3.0 or less at 1 megaHertz and is optically clear. In some embodiments, the cured organic layer has a dielectric constant of 2.8 or less at 1 megaHertz, or 2.7 or less at 1 megaHertz, 2.6 or less at 1 megaHertz, 2.5 or less at 1 megaHertz, or even 2.3 or less at 1 megaHertz.

It is also desirable, and in some instances necessary, to provide a predictable dielectric response at a range of frequencies that are relevant to the end-use application. In some embodiments, it is desirable for the cured organic layer to have a small difference between the dielectric constant at 100 kHz and the dielectric constant at 1 MHz. This difference is referred to as the“Dk-Delta value”. Therefore, a desirable feature of the cured organic layer is having a low measured Dk-Delta value. In some embodiments, the cured organic layer has a Dk-Delta value less than 0.05, less than 0.04, or even below 0.03.

The cured organic layer typically has a thickness of from 1-50 micrometers, in some embodiments 2-10 micrometers, and a surface roughness of less than 10 nanometers, in some embodiments less than 5 nanometers. Surface roughness in this context refers to the arithmetic mean deviation R _a as defined by the equation:

Where the roughness trace includes n ordered equally spaced data points along the trace, and yi is vertical distance from the mean line to the 1 ^th point. In this way, the cured organic layer is suitable for use as a decoupling layer as described above.

The curable ink composition is a reactive mixture that comprises at least one first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms, a crosslinking monomer, and at least one initiator. The curable ink composition is solvent free and inkjet printable, having a viscosity of less than 30 centipoise at a temperature of from room temperature to less than 60°C, and upon curing forms a non crystalline, optically clear layer with a dielectric constant of 3.0 or less at 1 megaHertz. Also disclosed herein are articles, especially optical articles that comprise multiple layers of films, substrates and coatings. Among the articles of this disclosure are articles comprising a substrate, a cured organic layer adjacent to the substrate, and an inorganic barrier layer disposed on the cured organic layer. The cured organic layer comprises a crosslinked (meth)acrylate-based layer that has a thickness of from 1-50 micrometers, and has a dielectric constant of less than or equal to 3 at 1 megaHertz, and is optically clear.

Unless otherwise indicated, all numbers 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. The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 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. For example, reference to "a layer" encompasses embodiments having one, two or more layers. 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.

As used herein, the term“adjacent” refers to two layers that are proximate to another layer. Layers that are adjacent may be in direct contact with each other, or there may be an intervening layer. There is no empty space between layers that are adjacent.

The curable ink compositions are“substantially solvent free” or“solvent free”. As used herein,“substantially solvent free” refers to the curable ink compositions having less than 5 wt-%, 4 wt-%, 3 wt-%, 2 wt-%, 1 wt-% and 0.5 wt-% of non-polymerizable (e.g. organic) solvent. The concentration of solvent can be determined by known methods, such as gas chromatography (as described in ASTM D5403). The term“solvent free” as it implies that no solvent is present in the composition. It should be noted that whether the curable ink composition is substantially solvent free or solvent free, no solvent is deliberately added. Typically, the curable ink compositions are described as“100% solids”. As used herein,“100% solids” refers to curable ink compositions that do not contain volatile solvents and that all of the mass that is deposited on a surface remains there, no volatile mass is lost from the coating.

The terms“Tg” and“glass transition temperature” are used interchangeably. If measured, Tg values are determined by Differential Scanning Calorimetry (DSC) at a scan rate of l0°C/minute, unless otherwise indicated. Typically, Tg values for copolymers are not measured but are calculated using the well-known Fox Equation, using the monomer Tg values provided by the monomer supplier, as is understood by one of skill in the art.

The terms “room temperature” and “ambient temperature” are used interchangeably and have their conventional meaning, referring to temperatures of from 20-25°C.

The term“organic” as used herein to refer to a cured layer, means that the layer is prepared from organic materials and is free of inorganic materials.

The term“(meth)acrylate” refers to monomeric acrylic or methacrylic esters of alcohols. Acrylate and methacrylate monomers or oligomers are referred to collectively herein as "(meth)acrylates”. The term“(meth)acrylate-based” as used herein refers to a polymeric composition that comprises at least one (meth)acrylate monomer and may contain additional (meth)acrylate or non-(meth)acrylate co-polymerizable ethylenically unsaturated monomers. Polymers that are (meth)acrylate based comprise a majority (that is to say greater than 50% by weight) of (meth)acrylate monomers.

The terms“free radically polymerizable” and“ethylenically unsaturated” are used interchangeably and refer to a reactive group which contains a carbon-carbon double bond which is able to be polymerized via a free radical polymerization mechanism.

The terms“polymer” and“oligomer” are used herein consistent with their common usage in chemistry. In chemistry, an oligomer is a molecular complex that consists of a few monomer units, in contrast to a polymer, where the number of monomers repeat units is, in theory, not limited. Dimers, trimers, and tetramers are, for instance, oligomers composed of two, three and four monomer repeat units, respectively. Polymers on the other hand are macromolecules composed of many monomer repeated units. The term“hydrocarbon group” as used herein refers to any monovalent group that contains primarily or exclusively carbon and hydrogen atoms. Alkyl and aryl groups are examples of hydrocarbon groups.

The term“alkyl” refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. The alkyl can be linear, branched, cyclic, or combinations thereof and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.

The term“alkylene” refers to a divalent group that is a radical of an alkane. The alkylene can be straight-chained, branched, cyclic, or combinations thereof. The alkylene often has 1 to 20 carbon atoms. In some embodiments, the alkylene contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The radical centers of the alkylene can be on the same carbon atom (i.e., an alkylidene) or on different carbon atoms.

The term“alicyclic” as used herein refers to a group that is both aliphatic and cyclic in nature, containing one or more all-carbon rings which may be saturated or unsaturated, but are not aromatic in character, and may be substituted by one or more alkyl groups.

Unless otherwise indicated, "optically transparent" refers to a layer, film, or article that has a high light transmittance over at least a portion of the visible light spectrum (about 400 to about 700 nm). Typically, optically transparent layers, films, or articles have a luminous transmission of at least 85%, often at least 90%.

Unless otherwise indicated, "optically clear" refers to a layer, film, or article that has a high light transmittance over at least a portion of the visible light spectrum (about 400 to about 700 nm), and that exhibits low haze. Typically, optically clear layers, films, or articles have visible light transmittance values of at least 85%, or even 90%, often at least 95%, and haze values of 5% or less, often 2% or less. Luminous transmission and haze can be measured using the techniques described in the Examples section.

The terms“dielectric constant”,“dielectric loss”,“loss tangent” are used consistent their commonly understood definitions. Dielectric constant (at any frequency) is the amount of energy stored per cycle of electric field oscillation and is determined as the real part of the complex electrical permittivity defined for Maxwell’s equations. Dielectric loss (at any frequency) is the amount of energy dissipated per cycle of electric field oscillation and is determined as the imaginary part of the complex electrical permittivity defined for Maxwell’s equations. Loss tangent (at any frequency) is the ratio of the dielectric loss to the dielectric constant.

The term“Dk-Delta” as used herein refers to the difference between the dielectric constant at 100 kHz and the dielectric constant at 1 MHz.

Disclosed herein are curable compositions that are printable, and thus are described as inks. The curable compositions need not be used as inks, that is to say that they need not be printed and then cured, the curable compositions can be delivered to substrate surfaces in a wide variety of ways, but they are capable of being printed. In particular, the printable compositions of this disclosure are typically capable of being inkjet printed, which means that they have the proper viscosity and other attributes required to be inkjet printed. The term“inkjet printable” is not a process description or limitation, but rather is a material description, meaning that the curable compositions are capable of being inkjet printed, and not that the compositions necessarily have been inkjet printed. This is akin to the expression hot melt processable, which means that a composition is capable of being hot melt processed but does not mean that the composition has been hot melt processed.

The curable ink compositions of this disclosure are reactive mixtures that comprise at least one first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms, an optional second monomer, a crosslinking monomer, and at least one initiator. The term monomer as used herein may include oligomeric species. The curable ink composition is solvent free and inkjet printable, having a viscosity of less than 30 centipoise at a temperature of from room temperature to less than 60°C, and upon curing forms a non-crystalline, optically clear layer with a dielectric constant of less than or equal to 3 at 1 megaHertz. The ink compositions are inkjet printable and are free from solvents. By free from solvents it is meant that no solvents are added to the curable ink composition, and that no solvents are detectable in the curable composition. The term “solvents” is used herein consistent with the generally understood term of art and encompassing volatile organic and non-organic materials that are liquids at room temperature. A wide variety of monomeric species are suitable for use as the first monomer of the curable ink composition. The first monomer comprises a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms. The term“branched” as used herein is used according to the common understanding of the term when used to describe hydrocarbon chains, and means there is at least one branch point on the chain where a carbon atom of the chain is bonded to at least three other carbon atoms, instead of two carbon atoms as in a linear hydrocarbon.

Monomers with hydrocarbon chains that contain greater than 12 carbon atoms are frequently referred to as “long chain hydrocarbons”. Typically, these long chain hydrocarbon chains have 12-32 carbon atoms. The long chain hydrocarbons of the present disclosure are branched long chain hydrocarbons, meaning that they have at least one branch point along the hydrocarbon chain. In some embodiments, the branched long chain hydrocarbons have more than one branch point and are sometimes referred to as“highly branched hydrocarbons”.

Branched and highly branched long chain hydrocarbon monomers are desirable for use in the present curable compositions for a number of reasons. Long chain hydrocarbon monomers are desirable, because they contain a higher ratio of non-polarizable content (that is to say C-C and C-H bonds) relative to the polarizable content (from the carbonyl groups on the (meth)acrylate). It is desirable that the long chain hydrocarbon monomers be branched or even highly branched so that the curable and cured compositions are non crystalline. In the curable state, crystallinity is not desirable, especially when the curable composition is to be inkjet printed, as crystalline compositions can clog the inkjet nozzles. In the cured state, crystallinity can adversely affect the optical properties of the cured composition as is well known in the art. It is also well known in the chemical arts that “likes attract likes” meaning that similar chemical compositions tend to associate. A commonly used analogy is to view the hydrocarbon chains as strands of spaghetti, which when placed next to each other can agglomerate and form an associated mass. In the case of long chain hydrocarbon chains, especially when the hydrocarbon chains are 12 carbon atoms or larger, the hydrocarbon chains tend to associate and form crystallites. The formation of these crystallites can be prevented through the use of monomers with branched hydrocarbon chains, as the branching tends to disrupt the association of the hydrocarbon chains.

In some embodiments, the first monomer is derived from a 2-alkyl alkanol: i.e. a Guerbet alkanol. The molar carbon number average of said 2-alkyl alkanols of the Guerbet (meth)acrylates is 12 to 32 (C12-C32), more typically 12 to 20 (C12-C2 ₀ ) _. When the optional b)

C _1-12 alkanol (meth)acrylates are present, the carbon number molar average of the alkanols of the a) and b) (meth)acrylic acid ester is 12 to 20 (C ₁₂ -C ₂₀ ) _.

The (meth)acrylic acid ester monomer of 2-alkyl alkanols are derived from C ₁₂ -C ₃₂ Guerbet alkanols, typically C ₁₂ -C ₂₀ Guerbet alkanols. These Guerbet alkanols may be obtained by base-catalyzed self-condensation of linear and/or branched alkanols containing 4 to 14 and typically 6 to 12 carbon atoms. Primary or secondary alkanols may be used in the preparation of Guerbet alkanols.

It is known in the art that Guerbet alkanols may be formed from the same or different alkanols i.e. a homo or hetero system. That is, a Guerbet alkanol is the condensation product of two alkanol molecules joined at the beta carbon of the alkanol which has retained the hydroxyl functionality; i.e. 2-alkyl alkanols. The resultant product is therefore a branched primary alkanol containing a single hydroxyl group. It is possible to use mixtures of starting materials in the Guerbet reaction and condense them into mixtures of alkanol products. It is also possible to obtain products which are Guerbet alkanols from a short chained alkanol. It is desired for reasons of polarity, Tg and modulus that Guerbet alkanols having a molar carbon number average between 12-32 be used. An overview of Guerbet alkanols was published by A. J. O'Lennick in Soap Cosm. Chem. Spec. (April) 52 (1987). Reference may also be made to US Patent No. 6,419,797 (Sherf et al.) for method to produce Guerbet alkanols.

The (meth)acrylate ester monomer derived from the Guerbet alkanols is of the formula I below:

R G ue rbe t

Formula I, wherein

R ^Guerbet j _s d _erjveci from a C ₁₂ -C ₃₂ 2-alkyl alkanol, i.e. an alkyl groups branched at the 2 position; and R ³ is H or CH ₃ .

Generally, the (meth)acrylate ester monomer derived from the Guerbet alkanols is of the formula P below:

Formula P

wherein

R ¹ and R ² are each independently C ₄ to Ci ₄ saturated, and branched or linear alkyl; and R ³ is H or CH ₃ .

While in some embodiments, the Guerbet alkanol is derived from linear alkanols, i.e. R ¹ and R ² are linear alkyl groups, it has been found that such (meth)acrylate esters of “linear Guerbet alkanols” provide a lower Tg compared to monomers where R ¹ and R ² are branched, and for reasons explained below these monomers may not be particularly suitable for use in the current curable compositions. The Tg of the homopolymers of such monomers is < -20°C, or < -30°C, or even < -40°C.

These Guerbet alkanol derived (meth)acrylate esters have been used to prepare pressure sensitive adhesives, as described in, for example, US Patent No. 8,137,807. Pressure sensitive adhesive compositions are well known to those of ordinary skill in the art to possess properties including the following: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be cleanly removable from the adherend. Materials that have been found to function well as pressure sensitive adhesives are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power. Obtaining the proper balance of properties is not a simple process. It should be noted that the present curable ink compositions, upon curing are not pressure sensitive adhesives. Rather, the cured organic coatings prepared from the curable ink compositions of the present disclosure are not tacky and do not have the properties of the class of materials that are pressure sensitive adhesives.

Particularly suitable branched alkyl (meth)acrylate monomers with 12 or more carbon atoms, are those which are highly branched, meaning that they contain at least two branch points along the hydrocarbon chain. These are monomers of Formula II wherein at least one of R ¹ and R ² comprises a branched hydrocarbon chain. These molecules tend to have Tg values that are surprisingly higher than the corresponding straight chain monomers. When the Tg of these monomers is discussed, it is meant that homopolymers of these monomers have a Tg of greater than or equal to -20°C when measured by DSC (as described in the Tg definition above). In some embodiments, the Tg of particularly suitable branched alkyl (meth)acrylate monomers is greater than or equal to -l8°C when measured by DSC.

Among the particularly suitable branched alkyl (meth)acrylate monomers is the isostearyl acrylate monomer commercially available from Kowa as“NK ESTER S1800 ALC”. The chemical of NK ESTER S 1800 ALC is shown below as Formula IP:

Formula HI

In some embodiments, the curable composition may optionally include additional monomers besides the first monomer, referred to in this disclosure as the second monomer. A wide array of additional monomers are suitable, typically being a monofunctional ethylenically unsaturated monomer with a homopolymer Tg of greater than that homopolymer Tg of the first monomer. Without being bound by theory, it is thought that increasing the Tg of the cured ink formulation reduces the mobility of the polarizable bonds in the crosslinked matrix, leading to a lower Dk-Delta, as defined above.

Typically, the second monomer is a (meth)acrylamide or a (meth)acrylate. Examples include, but are not limited to, acrylamides, such as acrylamide, methacrylamide, N-methyl acrylamide, N-ethyl acrylamide, N- hydroxyethyl acrylamide, diacetone acrylamide, N,N-dimethyl acrylamide, N, N-diethyl acrylamide, N-ethyl-N- aminoethyl acrylamide, N-ethyl-N- hydroxyethyl acrylamide, N,N-dihydroxyethyl acrylamide, t-butyl acrylamide, N,N-dimethylaminoethyl acrylamide, and N-octyl acrylamide, and (meth)acrylates, such as 2,2-(diethoxy)ethyl (meth)acrylate, 2- hydroxy ethyl (meth)acrylate, caprolactone (meth)acrylate, 3-hydroxypropyl (meth)acrylate, methyl (meth)acrylate, isobomyl (meth)acrylate, 2-(phenoxy)ethyl (meth)acrylate, biphenyl methyl (meth)acrylate, t-butyl cyclohexyl (meth)acrylate, cyclohexyl (meth)acrylate, dimethyladamantyl (meth)acrylate, 2-naphthyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, t-butyl (meth)acrylate, 2,3,3-trimethyl buten-2yl -acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, n-hexyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, 3, 3, 5 -trimethyl cyclohexyl (meth)acrylate, isopropyl (meth)acrylate, ethylhexyl (meth)acrylate, n-vinyl pyrollidinone, and n-vinyl caprolactam.

Additionally, the curable ink compositions include, besides the first monomer and the optional second monomer, at least one crosslinker. Crosslinkers are well understood in the polymer arts as polyfunctional molecules that link polymer chains together. In the present curable ink compositions, the crosslinker typically is a multifunctional (meth)acrylate. Examples of useful multifunctional (meth)acrylate include, but are not limited to, di(meth)acrylates, tri(meth)acrylates, and tetra(meth)acrylates, such as 1,6- hexanediol di(meth)acrylate, l,4-butanediol di(meth)acrylate, propylene glycol di(meth)acrylates, ethylene glycol di(meth)acrylates, hydroxy pivalic acid neopentyl glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, bisphenol A di(meth)acrylates, tri cyclodecane dimethanol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylates, polybutadiene di(meth)acrylate, polyurethane di(meth)acrylates, and glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tri s(2 -hydroxy ethyl )isocyanurate triacrylate, pentaerythritol tri- and tetra(meth)acrylate and, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated and propoxylated versions and mixtures thereof. Particularly suitable crosslinkers include tri cyclodecane dimethanol diacrylate, and trimethylolpropane triacrylate. The amount and identity of the crosslinker or crosslinkers can vary, but typically the total amount of crosslinkers are present in an amount of at least 5 weight %. By weight % it is meant the % by weight of the total curable components of the curable ink composition.

In some embodiments, the curable ink composition comprises 1-95 weight % of the first monomer, 0-50 weight % of the second monomer, and at least 5 weight % crosslinking monomer. By weight % it is meant the % by weight of the total curable components of the curable ink composition.

The curable ink composition also comprises at least one initiator. Typically the initiator is a photoinitiator, meaning that the initiator is activated by light, generally ultraviolet (UV) light, although other light sources could be used with the appropriate choice of initiator, such a visible light initiators, infrared light initiators, and the like. Thus, the curable ink compositions are generally curable by UV or visible light, typically UV light. Therefore, typically, UV photoinitiators are used as the initiator. Photoinitiators are well understood by one of skill in the art of (meth)acrylate polymerization. Examples of suitable free radical photoinitiators include IRGACURE 4265, IRGACURE 184, IRGACURE 651, IRGACURE 1173, IRGACURE 819, IRGACURE TPO, IRGACURE TPO-L, commercially available from BASF, Charlotte, NC. Particularly suitable photoinitiators include those that feature high absorbance above 365 nm wavelength. These include the acylphosphine oxide family of photoinitiators such as IRGACURE TPO, IRGACURE TPO-L, and IRGACURE 819.

Generally the photoinitiator is used in amounts of 0.01 to 10 parts by weight, more typically 0.1 to 2.0, parts by weight relative to 100 parts by weight of total reactive components.

Besides the curable components described above, the curable ink composition may include additional optional non-curable components, as long as such components do not interfere with curing of the curable ink composition and do not adversely affect the properties of the cured composition. As mentioned above, solvents are not suitable additives for the curable ink compositions, as the curable ink compositions are desirably 100% solids compositions. While a variety of optional components are suitable, since the cured compositions are not pressure sensitive adhesives, as was pointed out above, tack generating agents are not suitable additives, and the curable ink compositions are generally free of tack generating agents. Tack generating agents are resins that are added to polymeric compositions to increase or to generate tack, especially pressure sensitive adhesive tack in the polymeric composition. The ink formulations may also contain polymerization inhibitors, UV absorbers, light stabilizers (e.g. hindered amine light stabilizers (HALS)), adhesion promoters, sensitizers, synergists, antioxidants, catalysts, dispersants, desiccants, surfactants, leveling agents, and the like as needed or desired. Polymeric surfactants and/or desiccants may be added to inks to prevent the formation of satellite drops and splattering effects during inkjet printing. It is desirable that any non- curable polymeric components present in the formulation also have a dielectric constant less than or equal to 3 at 1 MHz . Examples of such materials are polyisobutylene oligomers such as the GLISSOPAL series (BASF) and the TPC series (TPC Group, Houston, TX).

One particularly suitable optional additive is an adhesion promoter. An adhesion promoter is used as an additive or as a primer to promote adhesion of coatings, inks, or adhesives to the substrate of interest. An adhesion promoter usually has an affinity for the substrate and the applied coating, ink, or adhesive. Among the suitable adhesion promoters are silane-functional compounds, titanates, and zirconates. Examples of suitable titanates and zirconates include titanium or zirconium butoxide. Typically, if used, the adhesion promoter comprises a silane-functional compound. Sometimes silane- functional adhesion promoters are called coupling agents since they have different functionality at each end of the compound and thus can act to couple different surfaces such as inorganic surfaces and organic surfaces. A wide variety of silane adhesion promoters are suitable such as the (meth)acrylate-functional alkoxy silane SILQLrEST A- 174 from Momentive Performance Materials. With this type of adhesion promoter the alkoxy silane functionality interacts with an inorganic surface and the (methacrylate- functionality co-polymerizes with the curable ink composition. Other examples of silane coupling agents that are suitable include octadecyltrimethoxysilane, isooctyltrimethoxysilane, hexadecyltrimethoxysilane, hexyltrimethoxysilane, methyl trimethoxysilane, hexamethyldisilazane, hexamethyldisiloxane, aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane and the like.

Also disclosed herein are articles. A wide variety of articles may be prepared utilizing the cured organic layers described above. The articles may be relatively simple articles such as a substrate with a layer of cured organic layer disposed on it. In other embodiments, the articles are more complex, such as multilayer articles comprising a substrate, and an inorganic barrier layer, with a cured organic layer between them, where the cured layer functions as a decoupling layer. The substrate may optionally have an inorganic coating layer present on its surface, so that the cured organic layer may be in contact with substrate surface or with the optional inorganic coating layer.

An example of a simple article is shown in Figure 1, where article 100 comprises substrate 120 with cured organic layer 110 disposed on the substrate.

Substrate 120 includes a wide array of flexible and non-flexible substrates. For example substrate 120 may be glass or a relatively thick layer of a polymeric material such as PMMA (polymethyl methacrylate) or PC (polycarbonate). Alternatively, substrate 120 may be flexible polymeric film such as films of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PC (polycarbonate), polyimide, PEEK (polyetherether ketone), and the like.

Cured organic layer 110 is a (meth)acrylate-based cured layer of the curable ink compositions described above. Again, it is important to note that while the curable composition is described as an“ink”, this just means that the composition is printable and not necessarily that the cured organic layer 110 has been printed, since as described above, other coating methods can also be used. In many embodiments, however, the cured organic layer 110 has been coated by printing, especially inkjet printing, and then has been cured. Cured organic layer 110 has all of the properties described above, namely the layer has a thickness of from 1-50 micrometers, in some embodiments from 5-30 micrometers, the layer has a dielectric constant of 3.0 or less at 1 megaHertz, and is optically clear. Additionally, in many embodiments, the cured organic layer 110 has a surface roughness of less than or equal to 10 nanometers, in some embodiments less than or equal to 5 nanometers.

Figure 2 shows a device that includes a multilayer article of the present disclosure. Figure 2 shows article 200 comprising substrate 230 with device 240 disposed on substrate 230. Inorganic barrier layer 250 is in contact with device 240, and cured organic layer 210 is in contact with the inorganic barrier layer 250. Figure 2 also includes optional inorganic layer 260 that is in contact with cured organic layer 210. Optional layer 270 is in contact with optional inorganic layer 260 and also with substrate 280. Additionally, between optional layer 260 and optional layer 270, there may be optional alternating pairs of layers of cured organic (210) and inorganic (260). For clarity these optional layers are not shown, but one can readily envision a stack of layers in the sequence 250/210/260/210/260, or 250/210/260/210/260/210/260, and so on.

The inorganic layer barrier layer 250 in contact with cured organic layer 210 can be prepared from a variety of materials including metals, metal oxides, metal nitrides, metal oxynitrides, metal carbides, metal oxyborides, and combinations thereof. A wide range of metals are suitable use in the metal oxides, metal nitrides, and metal oxynitrides, particularly suitable metals include Al, Zr, Si, Zn, Sn, and Ti. One particularly suitable inorganic barrier layer material is silicon nitride.

The thickness of the inorganic barrier layer 250 is not particularly limited, generally it is between 20 nanometers and 1 micrometer (1000 nanometers). More typically the thickness is from 20 nanometers to 100 nanometers.

The inorganic barrier layer can be deposited in a variety of ways. In general, any suitable deposition method can be utilized. Examples of suitable methods include vacuum processes such as sputtering, chemical vapor deposition, ALD (atomic layer deposition), metal-organic chemical vapor deposition, plasma enhanced chemical vapor deposition, evaporation, sublimation, electron cyclotron resonance-plasma enhanced chemical vapor deposition, and combinations thereof.

Optional inorganic barrier layer 260 is of a similar thickness as inorganic barrier layer 250 and may comprise the same inorganic material, or it may be a different inorganic material.

One embodiment of the device 200 is a touch sensing device. In this device, substrate 230 is a thin film transistor, device 240 is an OLED device, optional layer 270 is an optically clear adhesive layer, and substrate 280 is a touch sensor.

Also disclosed herein are methods for preparing articles, especially optical articles. These methods comprise, providing a substrate with a first major surface and a second major surface, providing a curable ink composition, disposing the curable ink composition on the second major surface of the substrate to form a curable layer, and curing the curable layer to form a cured organic layer with thickness of from 1-50 micrometers, where the cured organic layer has a dielectric constant of 3.0 or less at 1 megaHertz. In many embodiments, the surface roughness of the cured organic layer is less than 10 nanometers, in some embodiments less than or equal to 5 nanometers. To the surface of this cured organic layer may be deposited an inorganic barrier layer.

In many embodiments, the disposing of the curable ink composition on the second major surface of the substrate to form a curable layer comprises printing, especially inkjet printing. As described above, inkjet printing has a variety of desirable features that make it particularly suitable for preparing the curable layer, including the ability to deposit precise patterns on complex substrates and form a uniform coating with a surface roughness that is less than 10 nanometers, in some embodiments less than or equal to 5 nanometers.

The curable ink compositions used in this method are the curable ink compositions described above. Since the curable ink compositions include a photoinitiator, curing of the curable layer comprises photo curing. The nature of the photoinitiator determines the curing conditions, i.e. radiation wavelength used, duration of the exposure to radiation, etc.

As described above, the articles of this disclosure may include additional elements. In some embodiments, the method may further comprise providing a device such as an OLED, and placing the device on the second major surface of the substrate prior to disposing the curable ink composition on the second major surface of the substrate to form a curable layer. Also, the article may further comprise an inorganic layer disposed on the substrate and device surfaces. In these embodiments, the inorganic layer is disposed on the substrate and device surfaces prior to disposing the curable ink composition on the second major surface of the substrate to form a curable layer. Additionally, as described above, additional layers may be added to the exposed surface of the inorganic barrier after the inorganic barrier layer is disposed on the cured organic layer.

Also disclosed herein are methods for preparing articles, especially optical articles. These methods comprise, providing a substrate with a first major surface and a second major surface, providing a curable ink composition, disposing the curable ink composition on the second major surface of the substrate to form a curable layer, and curing the curable layer to form a cured organic layer with thickness of from 1-50 micrometers, where the cured organic layer has a dielectric constant of 3.0 or less at 1 megaHertz. In many embodiments, the surface roughness of the cured organic layer is less than 10 nanometers, in some embodiments less than or equal to 5 nanometers. To the surface of this cured organic layer is deposited an inorganic barrier layer.

In many embodiments, the disposing of the curable ink composition on the second major surface of the substrate to form a curable layer comprises printing, especially inkjet printing. As described above, inkjet printing has a variety of desirable features that make it particularly suitable for preparing the curable layer, including the ability to deposit precise patterns on complex substrates and form a uniform coating with a surface roughness that is less than 10 nanometers, in some embodiments less than or equal to 5 nanometers.

The curable ink compositions used in this method are the curable ink compositions described above. Since the curable ink compositions include a photoinitiator, curing of the curable layer comprise photo curing. The nature of the photoinitiator determine the curing conditions, i.e. radiation wavelength used, duration of the exposure to radiation, etc.

As described above, the articles of this disclosure may include additional elements. In some embodiments, the method may further comprise providing a device such as an OLED, and placing the device on the second major surface of the substrate prior to disposing the curable ink composition on the second major surface of the substrate to form a curable layer. Also, the article may further comprise an inorganic layer disposed on the substrate and device surfaces. In these embodiments, the inorganic layer is disposed on the substrate and device surfaces prior to disposing the curable ink composition on the second major surface of the substrate to form a curable layer. Additionally, as described above, additional layers may be added to the exposed surface of the inorganic barrier after the inorganic barrier layer is disposed on the cured organic layer.

The disclosure includes the following embodiments:

Among the embodiments are curable ink compositions. Embodiment 1 includes a curable ink composition comprising: a first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms; a crosslinking monomer; and at least one initiator, wherein the curable ink composition is solvent free and inkjet printable, having a viscosity of less than 30 centipoise at a temperature of from room temperature to less than 60°C, and upon curing forms a non-crystalline, optically clear layer with a dielectric constant of less than or equal to 3.0 at 1 megaHertz.

Embodiment 2 is the curable ink composition of embodiment 1, wherein the dielectric constant is less than or equal to 2.8 at 1 megaHertz.

Embodiment 3 is the curable ink composition of embodiment 1, wherein the dielectric constant is less than or equal to 2.7 at 1 megaHertz.

Embodiment 4 is the curable ink composition of embodiment 1, wherein the dielectric constant is less than or equal to 2.6 at 1 megaHertz.

Embodiment 5 is the curable ink composition of embodiment 1, wherein the dielectric constant is less than or equal to 2.5 at 1 megaHertz.

Embodiment 6 is the curable ink composition of embodiment 1, wherein the dielectric constant is less than or equal to 2.3 at 1 megaHertz.

Embodiment 7 is the curable ink composition of any of embodiments 1-6, wherein the first monomer comprises a branched alkyl (meth)acrylate monomer with 12-32 carbon atoms, with at least two branch points.

Embodiment 8 is the curable ink composition of any of embodiments 1-7, wherein the first monomer comprises a branched alkyl (meth)acrylate monomer with 12-20 carbon atoms, with at least two branch points.

Embodiment 9 is the curable ink composition of any of embodiments 1-6, wherein the first monomer is derived from a Guerbet alkanol.

Embodiment 10 is the curable ink composition of any of embodiments 1-9, wherein the first monomer has a homopolymer Tg of greater than or equal to -20°C.

Embodiment 11 is the curable ink composition of any of embodiments 1-9, wherein the first monomer has a homopolymer Tg of greater than or equal to -l8°C.

Embodiment 12 is the curable ink composition of any of embodiments 1-11, wherein the curable ink composition further comprises at least one second monomer, the second monomer comprising a monofunctional (meth)acrylate monomer that has a homopolymer Tg of greater than that homopolymer Tg of the first monomer.

Embodiment 13 is the curable ink composition of any of embodiments 1-11, wherein the curable components of the curable ink composition comprise: 1-95 weight % of the first monomer; 0-50 weight % of a second monomer; and at least 5 weight % crosslinking monomer.

Embodiment 14 is the curable ink composition of any of embodiments 1-13, wherein the curable ink composition is free of tack generating agents.

Embodiment 15 is the curable ink composition of any of embodiments 1-14, further comprising at least one additive selected from polymeric additives, polymerization inhibitors, ETV absorbers, light stabilizers, adhesion promoters, sensitizers, synergists, antioxidants, catalysts, dispersants, desiccants, surfactants, and leveling agents.

Embodiment 16 is the curable ink composition of embodiment 15, wherein the at least one additive comprises a polymeric additive having a dielectric constant less than equal to 3.0 at 1 megaHertz.

Embodiment 17 is the curable ink composition of embodiment 16, wherein the polymeric additive is polyisobutylene oligomer.

Embodiment 18 is the curable ink composition of any of embodiments 1-17, further comprising at least one adhesion promoter.

Embodiment 19 is the curable ink composition of embodiment 18, wherein the adhesion promoter comprises at least one silane.

Embodiment 20 is the curable ink composition of embodiment 19, wherein the silane comprises octadecyltrimethoxysilane, isooctyltrimethoxysilane, hexadecyltrimethoxysilane, hexyltrimethoxysilane, methyl trimethoxysilane, hexamethyldisilazane, hexamethyldisiloxane, aminopropyltrimethoxysilane, or 3- acryloxypropyltrimethoxysilane.

Embodiment 21 is the curable ink composition of any of embodiments 1-20, wherein the initiator comprises a photoinitiator, present in a level of 0.01-10 parts by weight compared to 100 parts by weight of curable components.

Embodiment 22 is the curable ink composition of any of embodiments 1-21, wherein the curable composition is photocurable, curable with ultraviolet or visible light radiation.

Also disclosed are articles. Embodiment 23 includes an article comprising: a substrate with a first major surface and a second major surface; a cured organic layer with a first major surface and a second major surface, where the first major surface of the cured organic layer is adjacent to at least a portion of the second major surface of the substrate, wherein the cured organic layer comprises a crosslinked (meth)acrylate-based layer and has a thickness of from 1-50 micrometers, and has a dielectric constant of 3.0 or less at 1 megaHertz, and is non-crystalline and optically clear.

Embodiment 24 is the article of embodiment 23, wherein the dielectric constant is less than or equal to 2.8 at 1 megaHertz.

Embodiment 25 is the article of embodiment 23, wherein the dielectric constant is less than or equal to 2.7 at 1 megaHertz.

Embodiment 26 is the article of embodiment 23, wherein the dielectric constant is less than or equal to 2.6 at 1 megaHertz.

Embodiment 27 is the article of embodiment 23, wherein the dielectric constant is less than or equal to 2.5 at 1 megaHertz.

Embodiment 28 is the article of embodiment 23, wherein the dielectric constant is less than or equal to 2.3 at 1 megaHertz.

Embodiment 29 is the article of any of embodiments 23-28, wherein the cured organic layer has a Dk-Delta value of less than 0.05, where Dk-Delta is the difference between the dielectric constant at 100 kiloHertz and the dielectric constant at 1 MegaHertz.

Embodiment 30 is the article of any of embodiments 23-28, wherein the cured organic layer has a Dk-Delta value of less than 0.04, where Dk-Delta is the difference between the dielectric constant at 100 kiloHertz and the dielectric constant at 1 MegaHertz.

Embodiment 31 is the article of any of embodiments 23-28, wherein the cured organic layer has a Dk-Delta value of less than 0.03, where Dk-Delta is the difference between the dielectric constant at 100 kiloHertz and the dielectric constant at 1 MegaHertz.

Embodiment 32 is the article of any of embodiments 23-31, wherein the substrate comprises an inorganic coating layer present on the second major surface, such that the first major surface of the cured organic layer is in contact with the inorganic coating layer.

Embodiment 33 is the article of any of embodiments 23-32, wherein the second major surface of the cured organic layer is in contact with an inorganic coating layer. Embodiment 34 is the article of any of embodiments 23-33, wherein the cured organic layer comprises a curable ink composition that has been printed and cured on at least a portion of the second major surface of the substrate, wherein the curable ink composition comprises: a first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms; a crosslinking monomer; and at least one initiator, wherein the curable ink composition is inkjet printable and is free from solvents, having a viscosity of less than 30 centipoise at a temperature of from room temperature to less than 60°C.

Embodiment 35 is the article of embodiment 34, wherein the first monomer comprises a branched alkyl (meth)acrylate monomer with 12-32 carbon atoms, with at least two branch points.

Embodiment 36 is the article of any of embodiments 34-35, wherein the first monomer comprises a branched alkyl (meth)acrylate monomer with 12-20 carbon atoms, with at least two branch points.

Embodiment 37 is the article of any of embodiments 34-36, wherein the first monomer is derived from a Guerbet alkanol.

Embodiment 38 is the article of any of embodiments 34-37, wherein the first monomer has a homopolymer Tg of greater than or equal to -20°C.

Embodiment 39 is the article of any of embodiments 34-37, wherein the first monomer has a homopolymer Tg of greater than or equal to -l8°C.

Embodiment 40 is the article of any of embodiments 34-39, wherein the curable ink composition further comprises at least one second monomer, the second monomer comprising a monofunctional (meth)acrylate monomer that has a homopolymer Tg of greater than that homopolymer Tg of the first monomer.

Embodiment 41 is the article of any of embodiments 34-39, wherein the curable components of the curable ink composition comprise: 1-95 weight % of the first monomer; 0-50 weight % of a second monomer; and at least 5 weight % crosslinking monomer.

Embodiment 42 is the article of any of embodiments 34-41, wherein the curable ink composition is free of tack generating agents. Embodiment 43 is the article of any of embodiments 34-42, further comprising at least one additive selected from polymeric additives, polymerization inhibitors, UV absorbers, light stabilizers, adhesion promoters, sensitizers, synergists, antioxidants, catalysts, dispersants, desiccants, surfactants, and leveling agents.

Embodiment 44 is the article of embodiment 43, wherein the at least one additive comprises a polymeric additive having a dielectric constant less than equal to 3.0 at 1 megaHertz.

Embodiment 45 is the article of embodiment 44, wherein the polymeric additive is polyisobutylene oligomer.

Embodiment 46 is the article of any of embodiments 34-45, wherein the curable ink composition further comprising at least one adhesion promoter.

Embodiment 47 is the article of embodiment 46, wherein the adhesion promoter comprises at least one silane.

Embodiment 48 is the article of embodiment 47, wherein the silane comprises octadecyltrimethoxysilane, isooctyltrimethoxysilane, hexadecyltrimethoxysilane, hexyl trimethoxysilane, methyl trimethoxysilane, hexamethyldisilazane, hexam ethyl disiloxane, aminopropyltrimethoxysilane, or 3- acryloxypropyltrimethoxysilane.

Embodiment 49 is the article of any of embodiments 43-48, wherein the initiator comprises a photoinitiator, present in a level of 0.01-10 parts by weight compared to 100 parts by weight of curable components.

Embodiment 50 is the article of any of embodiments 43-49, wherein the curable ink composition is photocurable, curable with ultraviolet or visible light radiation.

Embodiment 51 is the article of any of embodiments 23-50, wherein the cured organic layer has a surface roughness of less than 5 nanometers.

Embodiment 52 is the article of any of embodiments 23-51, wherein the article further comprises a device disposed on the second major surface of the substrate, and adjacent to the first major surface of the cured organic layer.

Embodiment 53 is the article of embodiment 52, wherein the device comprises an OLED (organic light-emitting diode). Embodiment 54 is the article of embodiment 52 or 53, further comprising an inorganic coating layer disposed on the device and on the second major surface of the substrate, such that the first major surface of the cured organic layer is in contact with the inorganic coating layer.

Embodiment 55 is the article of any of embodiments 23-54, further comprising additional substrates or layers in contact with the second major surface of the cured organic layer.

Also disclosed are methods of preparing articles. Embodiment 56 includes a method of preparing an article comprising: providing a substrate with a first major surface and a second major surface; providing a curable ink composition wherein the curable ink composition comprises: a first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms; a crosslinking monomer; and at least one initiator, wherein the curable ink composition is solvent free and inkjet printable, having a viscosity of less than 30 centipoise at a temperature of from room temperature to less than 60°C, and wherein the curable ink composition when printed and cured has a dielectric constant of 3.0 or less at 1 megaHertz, and is non-crystalline and optically clear; disposing the curable ink composition on at least a portion of the second major surface of the substrate to form a curable layer; curing the curable layer to form a cured organic layer having a first major surface and a second major surface, where the first major surface of the cured organic layer is adjacent to the second major surface of the substrate.

Embodiment 57 is the method of embodiment 56, wherein the dielectric constant is less than or equal to 2.8 at 1 megaHertz.

Embodiment 58 is the method of embodiment 56, wherein the dielectric constant is less than or equal to 2.7 at 1 megaHertz.

Embodiment 59 is the method of embodiment 56, wherein the dielectric constant is less than or equal to 2.6 at 1 megaHertz.

Embodiment 60 is the method of embodiment 56, wherein the dielectric constant is less than or equal to 2.5 at 1 megaHertz.

Embodiment 61 is the method of embodiment 56, wherein the dielectric constant is less than or equal to 2.3 at 1 megaHertz. Embodiment 62 is the method of any of embodiments 56-61, wherein the cured organic layer has a Dk-Delta value of less than 0.05, where Dk-Delta is the difference between the dielectric constant at 100 kiloHertz and the dielectric constant at 1 MegaHertz.

Embodiment 63 is the method of any of embodiments 56-61, wherein the cured organic layer has a Dk-Delta value of less than 0.04, where Dk-Delta is the difference between the dielectric constant at 100 kiloHertz and the dielectric constant at 1 MegaHertz.

Embodiment 64 is the method of any of embodiments 56-61, wherein the cured organic layer has a Dk-Delta value of less than 0.03, where Dk-Delta is the difference between the dielectric constant at 100 kiloHertz and the dielectric constant at 1 MegaHertz.

Embodiment 65 is the method of any of embodiments 56-64, wherein the substrate comprises an inorganic coating layer present on the second major surface, such that the first major surface of the cured organic layer is in contact with the inorganic coating layer.

Embodiment 66 is the method of any of embodiments 56-64, wherein the second major surface of the cured organic layer is in contact with an inorganic coating layer.

Embodiment 67 is the method of any of embodiments 56-66, wherein the first monomer comprises a branched alkyl (meth)acrylate monomer with 12-32 carbon atoms, with at least two branch points.

Embodiment 68 is the method of any of embodiments 56-67, wherein the first monomer comprises a branched alkyl (meth)acrylate monomer with 12-20 carbon atoms, with at least two branch points.

Embodiment 69 is the method of any of embodiments 56-68, wherein the first monomer is derived from a Guerbet alkanol.

Embodiment 70 is the method of any of embodiments 56-69, wherein the first monomer has a homopolymer Tg of greater than or equal to -20°C.

Embodiment 71 is the method of any of embodiments 56-69, wherein the first monomer has a homopolymer Tg of greater than or equal to -l8°C.

Embodiment 72 is the method of any of embodiments 56-71, wherein the curable ink composition further comprises at least one second monomer, the second monomer comprising a monofunctional (meth)acrylate monomer that has a homopolymer Tg of greater than that homopolymer Tg of the first monomer.

Embodiment 73 is the method of any of embodiments 56-71, wherein the curable components of the curable ink composition comprise: 1-95 weight % of the first monomer; 0-50 weight % of a second monomer; and at least 5 weight % crosslinking monomer.

Embodiment 74 is the method of any of embodiments 56-73, wherein the curable ink composition is free of tack generating agents.

Embodiment 75 is the method of any of embodiments 56-74, further comprising at least one additive selected from polymeric additives, polymerization inhibitors, ETV absorbers, light stabilizers, adhesion promoters, sensitizers, synergists, antioxidants, catalysts, dispersants, desiccants, surfactants, and leveling agents.

Embodiment 76 is the method of embodiment 75, wherein the at least one additive comprises a polymeric additive having a dielectric constant less than equal to 3.0 at 1 megaHertz.

Embodiment 77 is the method of embodiment 76, wherein the polymeric additive is polyisobutylene oligomer.

Embodiment 78 is the method of any of embodiments 56-77, wherein the curable ink composition further comprising at least one adhesion promoter.

Embodiment 79 is the method of embodiment 78, wherein the adhesion promoter comprises at least one silane.

Embodiment 80 is the method of embodiment 79, wherein the silane comprises octadecyltrimethoxysilane, isooctyltrimethoxysilane, hexadecyltrimethoxysilane, hexyl trimethoxysilane, methyl trimethoxysilane, hexamethyldisilazane, hexam ethyl disiloxane, aminopropyltrimethoxysilane, or 3- acryloxypropyltrimethoxysilane.

Embodiment 81 is the method of any of embodiments 56-80, wherein the initiator comprises a photoinitiator, present in a level of 0.01-10 parts by weight compared to 100 parts by weight of curable components.

Embodiment 82 is the method of any of embodiments 56-81, wherein the curable ink composition is photocurable, curable with ultraviolet or visible light radiation. Embodiment 83 is the method of any of embodiments 56-82, wherein disposing of the curable ink composition on the second major surface of the substrate to form a curable layer comprises inkjet printing.

Embodiment 84 is the method of any of embodiments 56-83, wherein second major surface of the cured organic layer has a surface roughness that is less than 5 nanometers.

Embodiment 85 is the method of any of embodiments 56-84, wherein the cured organic layer has a thickness of from 1-50 micrometers.

Embodiment 86 is the method of any of embodiments 56-85, further comprising providing a device; and disposing the device on the second major surface of the substrate prior to disposing the curable ink composition on the second major surface of the substrate to form a curable layer.

Embodiment 87 is the method of embodiment 86, further comprising disposing an inorganic layer on the substrate and device surfaces prior to disposing the curable ink composition on the second major surface of the substrate to form a curable layer.

Embodiment 88 is the method of embodiment 87, further comprising disposing additional layers to the second major surface of the cured organic layer.

Examples

Low dielectric-constant inkjet ink compositions were prepared. The materials were applied to substrates and the physical, optical and mechanical properties were evaluated as shown in the following examples. 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, St. Louis, Missouri unless otherwise noted. The following abbreviations are used herein: in = inch; mm = millimeters; cm = centimeters; um = micrometer; J = Joule; sec = seconds; min = minutes; mL = milliliters; pL = picoliter; K = 1,000 (ie 15K = 15,000 Daltons molecular weight); Hz = Hertz; cps = centipoise; Dk = dielectric constant. The terms wt%, and % by weight are used interchangeably.

Table 1. Materials

Component Description

Test Methods

Sample Coating Coatings for the optical tests were made on substrate Sl using a wire-wound rod (Model: RDS10, RDS Specialties, Webster, NY). Ultraviolet (UV) curing of the films was performed immediately after coating using a“LIGHT HAMMER” system (Heraeus Noblelight Fusion UV Inc., Gaithersburg, MD) using a“D-bulb” with two passes of the conveyor belt running at 30 feet per minute (9.3 m/min). The total dose received was ~ 2 J/cm ² .

Test Method 1 : Transmission. Haze. Clarity and b* Measurements

The measurement of average % transmission, haze clarity and b* were conducted with a haze meter (BYK Gardiner, under the trade designation“BYK HAZEGARD Plus, Columbia, MD”) based on ASTM D1003-13. B* values were measured using an X-RITE SP62 portable spectrophotometer (X-RITE, Grand Rapids, MI). Results are recorded in Table 7.

Test Method 2: Viscosity Measurements l7mL of each ink formulation was loaded into a 25mm diameter double gap coaxial concentric cylinder apparatus (DIN 53019) on a viscometer (BOHLIN VISCO 88, Malvern Instruments Ltd, Malvern, UK). A thermal jacket equipped to the double gap cell allowed for the flow of recirculating water heated to 25°C and the system was allowed to equilibrate for 30 minutes prior to taking each measurement. The shear rate was ramped from 100 to 1000 Hz at 100 hz intervals, and the measurement was repeated three times. An average and standard deviation across all data points was taken as the viscosity, in units of centipoise. Results are recorded in Table 5.

Test Method 4: Dielectric Spectroscopy Thick films of each formulation were prepared for the dielectric spectroscopy measurement. The films were made by first taping easy and premium release liners to 5” x 5” (12.7 cm x 12.7 cm) borosilicate glass plates. Ll was used as the easy release liner, and L2 was used as the premium release liner. A 400 micron thick Teflon sheet with a 3” (7.6 cm) diameter circle punched out of the center, along with a side injection port was clamped in between the two release liners. 3 mL of each of the formulations were injected with a pipette into the construction via the injection port. The construction was clamped with binder clips and cured with a UV-LED lamp (CF2000, l=365-400hih, Clearstone Technologies, Hopkins, MN) 5 minutes per side, for a total radiation dose of -14 J/cm ² . The samples were carefully removed from the cell and peeled from the liners. The samples were run through a“LIGHT HAMMER” system (Heraeus Noblelight Fusion ETV Inc., Gaithersburg, MD) using a medium pressure mercury lamp (“D-bulb”) for a total dose of 4 J/cm2. The dielectric properties and electrical conductivity measurements were performed with an Alpha- A High Temperature Broadband Dielectric Spectrometer modular measurement system from Novocontrol Technologies Gmbh (Montabaur, Germany). All testing was performed in accordance with the ASTM D150 test standard. Some of the films were painted with copper paint, and some were laminated directly on the brass electrode without any copper paint depending on how well the samples were able to conform to the electrode surface. The Novocontrol ZGS Alpha Active Sample Cell was implemented once each sample was placed between two optically polished brass disks (diameter 40.0 mm and thickness 2.00 mm). Results are recorded in Table 6.

Test Method 3: Inkjet Printing and Drop Analysis

A piezoelectric drop-on-demand printhead (KM512M, Konica Minolta IJ Technologies, Tokyo, Japan) was used for Inkjet Printing Tests Konica Minolta's inkjet head is based on a piezo electric material (PZT), which can be made to move via application of an electric field. Ink channels composed of piezo walls can eject small drops of ink in accordance with the electrical signals applied to the electrodes on the walls. The KM512 P Head is driven by“shear mode”, in which the walls bend inward and outward to generate a pressure wave inside the channel. The relevant parameters of operation and waveform settings used for the printhead are shown below in Table 2. Images of the drops were captured at a regular time interval of 10 microseconds (psec) using a JetXPert instrument (Image XPert, Nashua, NH). The images from 10 psec to 400 psec were stitched together to form a composite image.

Table 2. Piezo inkjet parameters

Table 3. Table of Formulations

Table 4. Ink Formulation Components and Calculated Properties

Ink Preparation

Table 3 shows the general ink compositions. Table 4 shows the component amounts used for each of the Example formulations. F _ave is equivalent to the average functionality of the formulations, as described in the below equation:

P _ave = (1 MF) + (2 * OF) 4- (3 * 77· ),

Where MF is equal to the percent mono-functional components in the formulation, DF is equal to the percentage of di -functional components in the formulation, and TF is equal to the percentage of tri -functional components in the formulation. The Tg is calculated based on the well-known Flory-Fox equation, using literature values for each of the components. 2.0 wt.% PH1 and 0.5 wt.% II (based on total resin solids) was added to each of the formulations in Table 4. The formulations were mixed in an amber vial until homogenous using a sonicating bath. Examples were tested using the Test Methods listed above. Quantitative Results are shown in Tables 5, 6 and 7 below.

Results

Table 5. Viscosity of Uncured Inks at 25°C Table 6. Dielectric Response Properties of Cured Ink Formulations

Table 7. Measurement of Cured Ink Film Optical Properties

Inkjet Printing Results

Figure 3 shows a stitched image of the ink droplets from the Example 28 formulation over time, beginning 10 microseconds from the initial ejection from the printhead nozzle. A well-defined drop was formed within 160 micrometers of the nozzle, without any visible satellite droplet formation thereafter. The jetting velocity was over 2500 mm/sec and the characteristics of the ink were stable over time.