Field of the Disclosure

This disclosure relates to curable ink compositions which have a low dielectric constant relative to typical 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 relates to curable ink compositions which have a low dielectric constant relative to typical polymeric compositions, are printable, and can be used to form articles. In some embodiments, the curable ink composition comprises a curable ink mixture comprising at least a first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms, at least one crosslinking monomer, and at least one initiator, and an adhesion promoter entity. The adhesion promoter entity comprises at least one co-reactive (meth)acrylate alkoxysilane containing at least one nitrogen group or at least one co-reactive (meth)acrylate alkoxysilane and a second, non-(meth)acrylate moiety. The non-(meth)acrylate moiety is an alkoxy silane or an organotitanate or an organozirconate. 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, the curable composition forms a non-crystalline, optically clear layer with a dielectric constant of less than or equal to 3 at 1 megaHertz. The cured layer has increased adhesion to substrates comprising a silicon oxide, silicon nitride, or silicon oxynitride surface compared to the adhesion of a cured compositions without the adhesion promoter entity.

Also disclosed are articles. In some embodiments, the articles comprise a substrate comprising a silicon oxide, silicon nitride, or silicon oxynitride surface, a cured organic layer adjacent to at least a portion of the silicon oxide, silicon nitride, or silicon oxynitride surface of the substrate, and an inorganic barrier layer in contact with the cured organic layer. 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. The cured organic layer is formed from a curable ink composition that has been printed and cured on the second major surface of the substrate, where the curable ink composition is described above.

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.

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 to meet requirements upon the materials used in them. In particular, organic polymeric materials have found widespread use in optical devices, but increasing 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) in order to be effective as a spacer 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 supply 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 electroluminescent devices such as OLED (organic light-emitting diode) devices and QD (quantum dot) devices. 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 electroluminescent 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.

Because the barrier layers are present to provide moisture resistance, it is desirable that the barrier layers exhibit superior mechanical properties such as elasticity and flexibility yet still have low oxygen or water vapor transmission rates. Additionally, it is desirable that the barrier layers retain adhesion even when exposed to elevated temperature, high humidity or a combination thereof. In particular, delamination or curl can arise from thermal stresses or shrinkage in a multilayer structure.

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, are 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 UV 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 electroluminescent devices such as OLED (organic light-emitting diode) and QD (quantum dots) 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.

Among the issues with printable TFE layers is that the substrates on which the layers are printed are often substrates that are difficult for layers to adhere to. Among these substrates are silicon oxide, silicon nitride, and silicon oxynitride substrates. Often the printed layers at least partially lift off from the substrate surface. The likelihood of the layer lifting off of the substrate surface can be determined by a wide range of testing protocols. A particularly suitable testing protocol is the crosshatch adhesion test (ASTM D3359-09) as described in the Examples section. The current curable ink compositions have increased adhesion to the above described substrates.

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 60°C, or even room temperature of room temperature to 35°C. Typically, the printable curable composition has a viscosity at these temperatures of 30 centipoise or less.

The curable ink composition, when coated and cured to form a cured organic layer, gives a cured organic layer that has a dielectric constant of 3.0 or less at 1 megaHertz and is optically clear. The cured organic layer typically has a thickness of from 1-50 micrometers, in some embodiments 5-30 micrometers, and is suitable for use as a decoupling layer as described above.

Additionally, the curable ink compositions have increased adhesion to substrates that include silicon oxide, silicon nitride, and silicon oxynitride substrates. This adhesion is increased through the use of an adhesion promoter entity as described below. The addition of this adhesion promotion entity increases the adhesion of the curable ink composition without adversely affecting any of the other desirable properties of the curable ink composition. The cured inks of this disclosure also typically maintain adhesion even after high temperature and humidity aging.

The curable ink composition is a blend of a reactive ink mixture that upon curing has a low dielectric constant, and a co-reactive adhesion promoter entity. The reactive ink mixture 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 co-reactive adhesion promoter entity comprises at least one (meth)acrylate alkoxysilane. 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, 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” refers to there being no solvent 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 10°C/minute, unless otherwise indicated. Typically, Tg values for copolymers are not measured but are calculated using the well-known Fox Equation, using the homopolymer 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.

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. 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 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 a blend of a curable ink mixture and an adhesion promoter entity. The curable ink mixture comprises at least a first monomer comprising a branched alkyl (meth)acrylate monomer with 12 or more carbon atoms, at least one crosslinking monomer, and at least one initiator and the adhesion promoter entity comprises at least one co-reactive (meth)acrylate alkoxysilane containing at least one nitrogen group or at least one co-reactive (meth)acrylate alkoxysilane and a second, non-(meth)acrylate moiety. Suitable adhesion promoter entities are described in greater detail below. 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 encompasses 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 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 hydrocarbons 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, long chain hydrocarbon monomers are desirable for use in the present curable compositions because it is desirable that the cured compositions be non crystalline. 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-C20) _. When the optional b)

Ci-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 (C12-C20) _. Examples of suitable (meth)acrylate monomers are described in PCT Publication No. WO 2019/123123.

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.

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- hydroxyethyl (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-butylcyclohexyl (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, 1,4-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, tricyclodecane dimethanol di(meth)acrylate, polyethylene glycol) di(meth)acrylates, polybutadiene di(meth)acrylate, polyurethane di(meth)acrylates, and glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tris(2-hydroxyethyl)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 tricyclodecane 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.

As mentioned above, the curable ink compositions also comprise an adhesion promoter entity. The adhesion promoter entity may be a single component or a combination of components, but all of the adhesion promoter entities include at least one co-reactive (meth)acrylate alkoxysilane. The adhesion promoter entity comprises one of three different embodiments described below, or a combination of the embodiments. A first embodiment of an adhesion promoter entity is a co-reactive (meth)acrylate alkoxysilane with at least one nitrogen group comprising a compound of the general formula 1 :

H ₂ C=CR ¹ -(CO)-L-Si(OR ² )„(R ³ ) ₃ -„

Formula 1 wherein R ¹ is a hydrogen atom or methyl group; L is a divalent linking group comprising alkylene groups or functionalized alkylene groups, with urethane linkages, amino linkages, urea linkages, amide linkages, or a combination thereof; each R ² is an alkyl or aryl group; each R ³ is an alkyl or aryl group; and n is an integer of 1-3.

Examples of first embodiment adhesion promoter entities include compounds of general formula 1 with divalent linking group L comprising general formula 2:

-A-0-(CO)-NH-B- Formula 2 wherein each A and B independently comprise alkylene or substituted alkylene groups with 2-8 carbon atoms.

Other examples of first embodiment adhesion promoter entities include compounds of general formula 1 with divalent linking group L comprising general formula 3 :

-D-NH-E- Formula 3 wherein D comprises a hydroxy-substituted alkylene group with 2-8 carbon atoms; and E comprises an alkylene or substituted alkylene group with 2-8 carbon atoms.

Suitable examples of first embodiment adhesion promoter entities include those described by formulas 1A, IB, and 1C:

H ₂ C=CH-(C0)-(CH2-CH2)-0-(C0)-NH-(CH2-CH2-CH ₂ )-Si(0CH3)3

Formula 1A

H ₂ C=C(-CH3)-(C0)-(CH2-CH2)-0-(C0)-NH-(CH2-CH2-CH2)-Si(0C H ₂ CH3)3

Formula IB

H ₂ C=CH-(CO)-(CH2-CH(OH)-CH2)-NH-(CH2-CH2-CH2)-Si(OCH ₂ CH3)3

Formula 1C Some of these adhesion promotion monomers are commercially available. The monomer of Formula IB is commercially available as SIM6480.8 from Gelest, and the monomer of Formula 1C is commercially available as SIA0180.0 from Gelest. The preparation of the monomer of Formula 3A is described in US Patent NO. 9,790,396, preparative example 7.

A second embodiment of adhesion promoter entities comprise at least one (meth)acrylate alkoxy silane and an alkoxy silane with a nitrogen group. These 2 components are described below.

Typically, the (meth)acrylate alkoxy silane is free from nitrogen groups, and is of the general formula 4:

H ₂ C=CR ¹ -(CO)-G-Si(OR ² ) _n (R ³ )3-n Formula 4 wherein R ¹ is a hydrogen atom or methyl group; G is a divalent linking group comprising alkylene groups or functionalized alkylene groups; each R ² is an alkyl or aryl group; each R ³ is an alkyl or aryl group; and n is an integer of 1-3.

A wide variety of (meth)acrylate-functional alkoxy silane compounds are commercially available such as SILQUEST A- 174 from Momentive Performance Materials.

The second embodiment of adhesion promoter entity also comprises an alkoxy silane with a nitrogen group. In many embodiments, the alkoxy silane with a nitrogen group comprises an aminosilane. Examples of aminosilanes include amine-functional silane coupling agents such as aminopropyltrimethoxysilane, and the like.

A third embodiment of adhesion promoter entities comprise at least one (meth)acrylate alkoxy silane and an organotitanate or organozirconate. These 2 components are described below.

Typically, the (meth)acrylate alkoxy silane is free from nitrogen groups, and are of the general formula 4 described above.

The third embodiments of adhesion promoter entities also comprise an organotitanate or organozirconate. Organozirconates are essentially the same as organotitanates with a zirconium atom instead of a titanium atom. The below description of organotitanates applies equally to organozirconates. Since organozirconates are much more expensive, they are less commonly used than their organotitanate analogs.

Organotitanates are well known in the art. They can be regarded as derivatives of ortho-titanic acid, Ti(OH)4, and hence are commonly known as organotitanates rather than by their systematic names. Organotitanates include alkoxytitanium esters, titanium chelates and titanium acylates, which have Ti-O-C linkages in their molecules. Organotitanates are used as modifiers for plastics, metals, glass, coating materials, etc., and as catalysts for chemical reactions. In addition, sputtered layers of organotitanate have been used as tie layers between metal oxide and polymer layers as described in US Patent Publication No 2019/0180968.

A wide variety of organotitanates are suitable, including titanium(IV) butoxide, titanium(IV) ethoxide, titanium (IV) ethylhexyloxide, titanium(IV) isopropoxide, titanium(IV)oxyacetylacetonate, titanium(IV) propoxide, titanium(IV)

(triethanolaminato)isopropoxide, and titanium diisopropoxide bis(acetylacetonate). They are commercially available from a variety of vendors including under the TYZOR trade name from Dorf Ketal (Stafford, Texas), as well as from Sigma-Aldrich (St. Louis, MO).

Examples of suitable organozirconates include zirconium(IV) bis(diethyl citrato)dipropoxide, zirconium(IV) acetyl acetonate, zirconium(IV) butoxide, zirconium(IV) ethoxide, zirconium(IV) 2-ethylhexanoate, zirconium(IV) isopropoxide, and zirconium(IV) propoxide. They are commercially available from a variety of vendors including under the TYZOR trade name from Dorf Ketal (Stafford, Texas), as well as from Sigma-Aldrich (St. Louis, MO).

Whichever embodiment of adhesion promoter entity is used, the adhesion promoter comprises a minor component of the curable ink composition. Typically, the adhesion promoter entity is present in the amount of 5% or less by weight of the total weight of the curable ink composition. Where the adhesion promoter entity is a combination of components, typically the non-(meth)acrylate moiety (such as aminosilane, organotitanate, or organozirconate) is present is an amount less that 1% by weight of the total ink composition.

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, tackifiers are not suitable additives, and the curable ink compositions are generally free of tackifiers. The ink formulations may also contain polymerization inhibitors, UV absorbers, light stabilizers (e.g. HALS hindered amine light stabilizers), synergists, antioxidants, catalysts, dispersants, leveling agents, and the like as needed or desired.

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 has an inorganic coating layer present on its surface, so that the cured organic layer may be in contact with the inorganic coating layer, where the inorganic coating layer comprises silicon oxide, silicon nitride, or silicon oxynitride.

An example of a simple article is shown in Figure 1, where article 100 comprises substrate 120 with surface layer 121 and cured organic layer 110 disposed on the substrate.

Substrate 120 includes a wide array of flexible and non-flexible substrates. Substrate 120 has surface coating 121, where the surface coating is silicon oxide, silicon nitride, or silicon oxynitride. 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 has increased adhesion to the substrate surface, 121 compared to the adhesion of the cured organic layer without the adhesion promoter entity. This increased adhesion is evidenced by an improvement in crosshatch adhesion using the test method (ASTM D3359-09) described in the Examples section below.

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 silicon oxide, silicon nitride, or silicon oxynitride 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, as mentioned above, is a layer of silicon oxide, silicon nitride, or silicon oxynitride. This surface is a layer that is relatively hard for cured organic layers to bond.

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 electroluminescent device such as an OLED device or a QD device, optional layer 270 is an optically clear adhesive layer, and substrate 280 is a touch sensor.

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; Milwaukee, Wisconsin unless otherwise noted. The following abbreviations are used: cm = centimeters; nm = nanometers; mL = milliliters; min = minutes; MHz = MegaHertz; mW = milliwatts; . The terms “weight %”, “% by weight”, and “wt%” are used interchangeably.

Table 1. Materials

Ink Formulations

Table 2. Compositions of low dielectric formulations Dkl, Dk2, Dk3 Table 2 shows three example base low dielectric ink formulations carrying wetting agent(s) present at 0.37 wt%. Adhesion promoter entities are added to these base formulations as shown in Tables 3-5. In Tables 3-5, the identity of the additive (adhesion promoter entity) and level (wt%) are shown.

Crosshatch Adhesion Testing Crosshatch adhesion was performed at room temperature on glass slides or silicon nitride substrates (PECVD / Silicon Valley Microelectronics, Santa Clara, CA). Substrates were plasma cleaned before coating (Harrick plasma cleaner PDC-3XG / air / 3 min / Rf level 13MHz / full power / 20 Watts). Samples were prepared by depositing 0.25 mL of formulation onto the substrate via pipette, covering with an RF02N liner, (SKC Haas, Korea; 2 mil; 51 micrometers), and curing using a Clearstone CF1000 UV LED system (395 nm, 50% intensity corresponding to 181 mW/cm ² for one minute at a distance of 1 cm from the surface of the sample). Thicknesses of coatings after cure were measured to be in the range 140-150 micrometers. Crosshatch adhesion tests were performed as described in ASTM D3359-09 (Standard Test Methods for Measuring Adhesion by Tape Test) where 0B denotes poor adhesion (greater than 65% of area detached) through a range up to 5B which denotes the best adhesion (no detachment and no damage to scored crosshatch lines).

Table 3. Crosshatch adhesion of low Dkl base formulation with various additives.

Table 4. Crosshatch adhesion of low Dk2 and low Dk3 base formulations with various additives.

The data in Tables 3 and 4 shows that adhesion is generally improved when acrylate or methacrylate-functionalized promoters are used (ACRYLATE 1 and 2, METHACRYLATE 1, 2 and 3). Good performance is generally obtained when the promoters have both acrylate and amine functionality present, either in a single silane (CARBAMATES 1 and 2) or in a mixture of silanes (ACRYLATE/ AMINO, AZASILANE). The carbamate without any silane content (CARBAMATE 3) gives less improvement in adhesion performance. In mixtures, adhesion decreases with increasing aminosilane loading. Amino- and butyl-functionalized silanes (AMINO and BUTYL) do not promote adhesion. The 98/2 ACRYLATE 1 / titanium butoxide additive gives better adhesion than ACRYLATE 1 alone or titanium butoxide alone. In most cases, optimum promoter loading is 1 wt%. Table 5. Crosshatch adhesion of formulations carrying 98/2 ACRYLATE 1 / TiOBu adhesion promoter with various wetting agents.

The data in Table 5 shows that for a given adhesion promoter (98/2 ACRYLATE 1 / TiOBu) good adhesion can be maintained relative to promoter-free control formulations in the presence of various different wetting agents, where wetting agents are used to control the degree of ink droplet spread on the substrate.