CN112585221A - Curable composition for forming light scattering layer - Google Patents

Abstract

The present invention provides curable compositions comprising at least one fluoropolymer, at least one monofunctional (meth) acrylate, at least one difunctional (meth) acrylate, and at least one initiator. The curable composition, when cured, forms an optical scattering layer comprising a matrix and phase separated microdomains. The matrix and the phase separated domains have different refractive indices and the domains are near or larger than the wavelength of visible light.

Description

Curable composition for forming light scattering layer

Technical Field

The present disclosure relates to optically light scattering layers formed from curable polymer compositions.

Background

Optical devices are becoming more complex and include more and more functional layers. As light passes through the layers of the optical device, the light may be altered by the layers in a wide variety of ways. For example, light may be reflected, refracted, or absorbed. In many cases, layers are included in an optical device for more than one purpose. For example, a layer may serve both a mechanical function, acting as a barrier separating two layers, and an optical function, such as transmitting or diffusing light.

One optical function that organic layers are utilized is to diffuse light. Optical devices include, for example, information displays such as liquid crystal displays and rear projection screens. For efficient operation and enhanced readability, these devices typically rely on light diffusing optical constructions. Such light diffusing constructions play a critical role in these displays by forward scattering light from the light source without significantly losing the intensity of the forward scattered light. This scattered, but highly transmissive, resultant light gives the desired background brightness for such displays by reducing the amount of incident light that is scattered or reflected back toward the light source. The elimination or limitation of this "backscattered" light is a key factor in the design of these light diffusing constructions. The diffuser may be incorporated into the optical system by adding additional diffuser components to the system, or in some cases by adding diffuse reflective properties to existing components.

The addition of an extra component to the optical system has the following disadvantages: introducing additional absorption and creating additional interfaces that can reflect light, thereby causing loss of illumination and other forms of image degradation. In addition, it may be difficult or impossible to add additional components in some multilayer systems.

Disclosure of Invention

The present disclosure relates to optically light scattering layers formed from curable polymer compositions. Curable compositions, articles prepared with these curable compositions, and methods of forming optical articles are described herein.

The curable composition of the present disclosure comprises at least one fluoropolymer, at least one monofunctional (meth) acrylate, at least one difunctional (meth) acrylate, and at least one initiator. In the present disclosure, the terms "curable composition", "curable ink" and "ink" are used interchangeably and refer to a curable composition that can be deposited and cured on a surface. Even though the curable composition may be described as an ink, it does not necessarily mean that it has been or needs to be applied by printing techniques. The curable composition is generally free of solvent and has a viscosity of less than 30 centipoise at a temperature of from room temperature to 60 ℃.

Articles of manufacture are also disclosed. In some embodiments, an article includes a substrate having a first major surface and a second major surface, and an optical scattering layer disposed on the first major surface of the substrate. The optical scattering layer includes a matrix and phase-separated micro-regions, wherein the matrix and the phase-separated micro-regions have different refractive indices, and wherein the micro-regions are near or larger than a wavelength of visible light.

Methods of making the articles are also disclosed. In some embodiments, the method comprises: providing a substrate having a first major surface and a second major surface; providing a curable composition; forming a layer of a curable composition on at least a portion of the first major surface of the substrate; the curable composition layer is cured to form a cured optical scattering layer. The curable composition comprises at least one fluoropolymer, at least one monofunctional (meth) acrylate, at least one difunctional (meth) acrylate, and at least one initiator. As noted above, the curable composition typically has a viscosity of less than 30 centipoise at temperatures from room temperature to 60 ℃. The cured optical scattering layer includes a matrix and phase-separated microdomains, wherein the matrix and phase-separated microdomains have different refractive indices, and wherein the microdomains are near or greater than the wavelength of visible light.

Drawings

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

Fig. 1A shows a schematic of a process of the present disclosure for forming an optical light scattering article.

Fig. 1B shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 1C shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 1D shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 1E shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 1F shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 1G shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 1H shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 1I shows a schematic of another process of the present disclosure for forming an optical light scattering article.

Fig. 2 shows a cross-sectional view of an optical microscopic view of the optically light scattering layer of example 2.

Fig. 3A shows a cross-sectional view of an AFM height image of the optically light scattering layer of example 2.

Fig. 3B shows a cross-sectional view of an AFM-IR map of the optically light scattering layer of example 2.

Figure 3C shows a cross-sectional view of an AFM-IR map of the optically light scattering layer of example 2.

Fig. 3D shows a cross-sectional view of an AFM-IR image ratio map of the optically light scattering layer of example 2.

Fig. 4 shows a cross-sectional view of an optical microscope image of the optically light scattering layer of example 1.

Fig. 5A shows a cross-sectional view of an AFM height image of the optically light scattering layer of example 1.

Fig. 5B shows a cross-sectional view of an AFM-IR map of the optically light scattering layer of example 1.

Fig. 5C shows a cross-sectional view of an AFM-IR map of the optically light scattering layer of example 1.

Fig. 5D shows a cross-sectional view of an AFM-IR image ratio map of the optically light scattering layer of example 1.

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 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 parts. It should be understood, however, 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 increasing complexity of optical devices makes it increasingly difficult to meet the requirements for the materials used in the optical devices. In particular, organic polymer materials have been widely used in optical devices, but the requirements for these polymer materials have become increasingly stringent.

For example, thin organic polymer films are desirable for a wide range of uses as adhesives, protective layers, interlayers, and the like in optical devices. As articles become more complex, the physical demands on these layers have increased. For example, as optical devices become more miniaturized, and at the same time typically include more layers, the need for thinner layers is increasing. Also, since the layer is thinner, more precision of the layer is also required. For example, to be effective spacers, thin spacers (1 micron thick) need to be flat and free of gaps and holes in order to provide proper spacing function. This requires that the organic layers be deposited in an accurate and consistent manner. Printing techniques have been developed to provide accurate and consistent deposition of organic polymeric materials. In printing techniques, a polymer or a curable composition that forms a polymer upon curing is printed onto a substrate surface to form a layer. In the case of printable polymers, solvents are typically added to prepare the polymer into a solution or dispersion that can be printed. When using polymers, a drying step is typically required after printing to produce the desired polymer layer. In the case of a curable composition that forms a polymer upon curing, the curable composition may or may not contain a solvent. The curable composition is then cured, typically by 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 its excellent accuracy.

Furthermore, these layers must provide not only their physical action (adhesion, protection, spacing, etc.), but also the desired optical properties. One optical property that is becoming increasingly important is light diffusion. In general, light diffusion has been achieved by using particles. The light-diffusing particles are dispersed within a polymerizable binder to form a curable mixture, the curable mixture is disposed on a surface and cured to form a layer having the light-diffusing particles suspended in a polymeric matrix.

Although this method for preparing a light-diffusing layer has been widely used, it has serious drawbacks and limitations. The addition of preformed particles and fillers can be problematic not only due to the complexity of backscattering, but also because the addition of these particles and fillers makes the filtration process more difficult, a process that is often required to improve coating uniformity. In addition, as layers become thinner, techniques such as inkjet printing are increasingly used to dispose curable layers onto surfaces, and the printing of preformed particle-filled mixtures can be very difficult because preformed particles tend to clog print head nozzles. In addition, while it is possible to produce a uniform diffusion layer in such a way, i.e. a layer having the same diffusion properties over the entire area of the layer, it is very difficult, if not impossible, to produce a selective diffusion layer in this way. As used herein, a selective diffusion layer refers to a layer having different diffusion properties in different regions of the layer.

Other techniques have been used to provide scattering layers without the use of preformed particles for optical applications.

Yang et al (US 2010/0259825) blend two incompatible monomers into an emulsion, coat, and then cure to lock the morphology. This does not allow for control of morphology during curing. Instead, control of morphology is performed prior to curing by varying the amount and/or speed of mixing prior to dispensing. To maintain stability and control the size of the domains formed, the emulsion requires stabilizers and other chemical components, which reduce the refractive index difference that may exist between the two phases, thereby reducing the amount of scattering that can be achieved. Control of the size of these phases outside of the initial emulsification was not demonstrated.

Young et al (US 9093666) also describe a phase separated solution of two different epoxysiloxane monomers mixed with a siloxane-free cycloaliphatic epoxy monomer and a photoinitiator. One of the epoxysilicone resins used is immiscible with the cycloaliphatic epoxy resin prior to curing and the epoxysilicone resin is agitated prior to curing for achieving a different particle size distribution in the range of 0.5 microns to 20 microns. This layer is applied as an encapsulation layer between two inorganic layers in order to enhance the light outcoupling of the OLED device. Control of the degree of phase separation during the curing step is not demonstrated or discussed.

Mazurek et al (US 8343633B2) use radiation curable telechelic siloxane-containing monomers dissolved in siloxane-free radiation curable monomers. In this method, the two phases are miscible with each other before curing, but phase separation occurs after curing. Some degree of control over domain size is demonstrated during the curing step, but since both phases contain crosslinkable (meth) acrylate moieties, crosslinking between the phases is allowed to occur, limiting the degree of diffusion and phase separation.

Another technique that has been used to prepare light diffusing pressure sensitive adhesives without the use of added particles is described in U.S. patent 9238762 (schafer et al). In this patent application, the block copolymer is dissolved in a solvent having an optically clear pressure sensitive adhesive matrix. After the solvent dries, the block copolymer phase separates from the polymer used in the pressure sensitive adhesive. The micro domains forming the block copolymer have a wavelength greater than that of visible light, thereby diffusing the visible light. Control of the degree of phase separation during the drying step is not discussed or demonstrated and the distribution of domain sizes is the same at all points along the layer.

The present disclosure differs from these in that a non-polymerizable amorphous fluoropolymer (typically a fluoroelastomer) is dissolved in an organic radiation curable monomer mixture to form an initially clear, miscible solution. Upon curing, the fluoropolymer phase separates from the methacrylate phase, providing a refractive index change that allows for sufficient optical scattering. This allows a greater degree of control over diffusion required for adequate phase separation, since the polymer does not copolymerize with the monomer during curing. For example, the ability to control particle size during the curing step by varying the light intensity used during curing to affect the rate of polymerization has been demonstrated. Furthermore, surprisingly, the fluoropolymer is soluble in the (non-fluorine containing) (meth) acrylate monomer, both being two materials with very different chemical structures. The use of such chemically different materials allows each of the components to have a large refractive index difference after phase separation has occurred. Finally, the ability to control phase separation during the curing step allows for the possibility of creating a variety of different domain sizes within a layer using patterning methods well known in the art, which may be beneficial in certain applications.

The present disclosure provides a curable composition that is free of particles and capable of forming a light diffusing layer. The curable composition comprises a fluoropolymer and a (meth) acrylate and a free radical initiator and forms a uniform single phase prior to curing. In general, fluoropolymers have good miscibility with (meth) acrylate monomers, so that the uncured composition layer does not include fluorocarbon-rich domains, rather the fluoropolymer/(meth) acrylate mixture is substantially homogeneous and transparent. The terms fluoropolymer and fluorocarbon are used interchangeably to refer to the fluoropolymer of the present disclosure. Upon activation of the photoinitiator by ultraviolet radiation, free radicals are generated within the film due to a decrease in entropy and an increase in free energy of mixing between the two components, which induces polymerization of the (meth) acrylate monomer and results in phase separation of the fluoropolymer or poly (meth) acrylate into discrete domains. The formation of phase separated microdomains leads to increased forward scattering of light (also referred to as "haze") due to the refractive index difference between the poly (meth) acrylate and the fluoropolymer. As light is scattered forward, the light is diffused, but continues to travel in the same general direction of incidence. In reverse scattering, light is reflected back in the direction of incidence. Thus, in back-scattering, some of the light intensity is lost due to reflection back to the source. In forward scattering, only a small amount of light is lost due to reflection, and since most of the light is transmitted in the incident direction, it is only diffused. This is desirable in the case of using a point light source that produces a bright spot where there is light from the point light source and an adjacent non-illuminated spot where there is no transmitted light. By using a forward scattering diffuser, the light from the point source propagates over a larger area, eliminating the bright/un-illuminated spot phenomenon. Forward scattering and backscattering are well known to those skilled in the art.

A light diffusing layer is prepared by disposing a curable composition onto a substrate and curing the curable composition to form a cured organic layer having a matrix and phase separated microdomains, wherein the matrix and the phase separated microdomains have different refractive indices. This process of curing a miscible composition to form a cured composition with phase separation domains is sometimes referred to as PIPS (polymerization induced phase separation). In this patent application, the domain size is large enough to diffuse visible light, in other words, the domains have an average diameter close to or larger than the wavelength of visible light (about 400nm to 700 nm). The PIPS model indicates that the substrate can be expected to be a cross-linked (meth) acrylate substrate with fluoropolymer microdomains. Nevertheless, as will be explained in more detail below, the cured organic layer formed is much more complex than a simple cross-linked (meth) acrylate matrix with fluoropolymer microdomains. It has been found that the cured organic layer comprises at least one of three different composition types or regions. Each of the regions includes a matrix and phase separated microdomains. The first region is a region in which the substantially continuous matrix comprises a crosslinked (meth) acrylate matrix and phase separated fluorocarbon-rich domains, wherein the fluorocarbon-rich domains are primarily, if not substantially all, fluorocarbon. The region of this embodiment is described above. The second region is a region in which the substantially continuous matrix comprises a cross-linked (meth) acrylate matrix and the phase-separated microdomains comprise a (meth) acrylate material and a fluoropolymer. In these embodiments, the microdomains may still be described as fluoropolymer-rich microdomains, but the microdomains include both fluoropolymer-rich nanodomains and crosslinked (meth) acrylate nanodomains. The third region is a (meth) acrylate-rich region in which the substantially continuous matrix includes fluorocarbon-rich domains and the phase-separated microdomains, wherein the (meth) acrylate-rich microdomains include at least a crosslinked (meth) acrylate material, and may also include a fluoropolymer.

The optical scattering layer includes at least one of the above regions. In some embodiments, the optical scattering layer is all one region and is substantially uniform throughout the region. In other embodiments, the optical scattering layer comprises more than one region. This phenomenon of distinct regions is different from the selective diffusion properties described below and refers to the composition of the matrix and the phase separated microdomains.

Another feature of the present disclosure is the ability to use selective curing to create a selective diffusion layer. As used herein, a selective diffusion layer refers to a layer having different diffusion properties in different regions of the layer. This selectivity is described in more detail below, and can be achieved in a variety of ways, such as by using a variable intensity light source and masking techniques.

Disclosed herein are curable compositions comprising at least one fluoropolymer, at least one monofunctional (meth) acrylate, at least one difunctional (meth) acrylate, and at least one initiator. The curable composition typically has a viscosity of less than 30 centipoise at temperatures from room temperature to 60 ℃. This viscosity allows the curable composition to be printed by techniques such as inkjet printing techniques, but of course the curable composition may be applied using a variety of application techniques.

Also disclosed herein are articles comprising a cured layer prepared from the curable composition, wherein the cured layer comprises a matrix and phase-separated microdomains, wherein the matrix and the phase-separated microdomains have different refractive indices, and wherein at least some of the microdomains are close to or larger than the wavelength of visible light, thereby being capable of diffusing visible light. Additionally, the present disclosure describes methods of making such articles.

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 layer, two layers, 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 adjacent to one another. Adjacent layers may be in direct contact with each other, or intervening layers may be present. There is no empty space between adjacent layers.

The curable ink composition is "substantially solvent-free" or "solvent-free". As used herein, "substantially free of solvent" means that the curable ink composition has less than 5 wt.%, 4 wt.%, 3 wt.%, 2 wt.%, 1 wt.%, and 0.5 wt.% of non-polymerizable (e.g., organic) solvent. Solvent concentration can be determined by known methods, such as gas chromatography (as described in ASTM D5403). The term "solvent-free" as the name implies, means that no solvent is present in the composition. It should be noted that no solvent is intentionally added, whether the curable ink composition is substantially solvent-free or solvent-free.

Typically, the curable ink composition is described as "100% solids". As used herein, "100% solids" refers to a curable ink composition that does not contain volatile solvents such that all of the material deposited on the surface remains on the surface and no volatile material is lost from the coating.

As used herein, the term "polymer" refers to a macromolecular material that may be a homopolymer or a copolymer. As used herein, the term "homopolymer" refers to a polymeric material that is the reaction product of one monomer. As used herein, the term "copolymer" refers to a polymeric material that is the reaction product of at least two different monomers.

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 deg.C/minute, unless otherwise indicated. Typically, the Tg value of the copolymer is not measured, but is calculated using the monomer Tg value provided by the monomer supplier using the well-known Fox equation, as will be understood by those skilled in the art.

The terms "room temperature" and "ambient temperature" are used interchangeably and have their conventional meaning and refer to temperatures of from 20 ℃ to 25 ℃.

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 terms "fluoropolymer" or "fluorinated polymer" are used interchangeably and refer to a fluorocarbon-based polymer having multiple carbon-fluorine bonds. Fluoropolymers are hydrocarbon polymers in which hydrogen atoms (typically many hydrogen atoms, or even all hydrogen atoms) have been replaced by fluorine atoms. An example of a fluoropolymer is a "fluoroelastomer". Fluoroelastomers are specialty fluorocarbon-based synthetic rubbers that do not contain a significant amount of crystallinity.

The term "(meth) acrylate" refers to a monomeric acrylate or methacrylate of an alcohol. Acrylate and methacrylate monomers or oligomers are generally referred to herein as "(meth) acrylates". As used herein, the term "(meth) acrylate-based" refers to a polymer composition that includes at least one (meth) acrylate monomer and may include additional (meth) acrylate or non- (meth) acrylate copolymerizable ethylenically unsaturated monomers. The (meth) acrylate-based polymer comprises a majority (that is, 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 that contains a carbon-carbon double bond that is capable of polymerizing via a free-radical polymerization mechanism.

As used herein, the term "hydrocarbon group" refers to any monovalent group that includes primarily or exclusively carbon and hydrogen atoms. Examples of hydrocarbon groups are alkyl groups and aryl groups.

The term "alkyl" refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. The alkyl group can be linear, branched, cyclic, or a combination thereof, and typically has from 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 "aryl" refers to monovalent groups that are aromatic and carbocyclic. The aryl group may have one to five rings connected to or fused with an aromatic ring. The other ring structures may be aromatic, non-aromatic, or combinations thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthracenyl (anthryl), naphthyl, acenaphthenyl, anthraquinonyl, phenanthrenyl, anthracenyl, pyrenyl, perylenyl, and fluorenyl.

The term "alkylene" refers to a divalent group that is a radical of an alkane. The alkylene group can be linear, branched, cyclic, or a combination thereof. The alkylene group typically has 1 to 20 carbon atoms. In some embodiments, the alkylene group comprises 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 groups may be on the same carbon atom (i.e., alkylidene) or on different carbon atoms.

The term "heteroalkylene" refers to a divalent group comprising at least two alkylene groups connected by a thio, oxy, or-NR-, wherein R is an alkyl group. The heteroalkylene can be linear, branched, cyclic, substituted with an alkyl group, or a combination thereof. Some heteroalkylene groups are polyoxyalkylene groups in which the heteroatom is oxygen, such as for example

-CH₂CH₂(OCH₂CH₂)_nOCH₂CH₂-。

As used herein, the term "alicyclic" refers to a group containing one or more all-carbon rings that are both aliphatic and cyclic in nature, which may be saturated or unsaturated but not aromatic in character, and which may be substituted with one or more alkyl groups.

Unless otherwise indicated, "optically transparent" means that the layer, film or article has a high light transmission over at least a portion of the visible spectrum (about 400nm to about 700 nm). Typically, an optically transparent layer, film or article has a light transmission of at least 90%.

Unless otherwise indicated, "optically clear" means that the layer, film or article has high light transmittance over at least a portion of the visible spectrum (about 400nm to about 700nm) and exhibits low haze. Typically, an optically clear layer, film or article has a visible light transmittance value of at least 90%, usually at least 95%, and a haze value of 5% or less, usually 2% or less. Light transmission and haze can be measured using the techniques described in the examples section.

Disclosed herein are curable compositions, articles prepared using these curable compositions, and methods of preparing articles using these curable compositions. The curable composition of the present disclosure provides a method for selectively preparing an optical scattering layer. By optically scattering is meant that the layer scatters visible light forward. As described above, the optical scattering layer is an optical scattering layer for diffusing visible light. The diffusion of visible light occurs because the curable composition forms phase-separated microdomains within the matrix when cured, and the matrix and the phase-separated microdomains have different refractive indices. In the present disclosure, the phase separated domains are close to or greater than the wavelength of visible light. Since visible light is generally characterized as having a wavelength of 400nm to 700nm, the phase separated domains are generally at least 100nm or greater, and typically 100nm to 4,000 nm. The microdomains are "fluoropolymer-rich," meaning that they have a high concentration of fluoropolymer in the (meth) acrylate matrix but not necessarily consist entirely of fluoropolymer, or "acrylate-rich," meaning that they have a high concentration of (meth) acrylate in the fluoropolymer-rich matrix but not necessarily consist entirely of (meth) acrylate. The presence of micro-regions that differ in refractive index from the surrounding matrix means that, as described by Snell's law, visible light will be refracted or scattered as it passes through the matrix and encounters the micro-regions due to this refractive index mismatch. This scattering is commonly referred to as forward scattering or haze. As mentioned above, forward scattering is desirable because it produces diffuse light with little loss in light intensity.

In the present disclosure, a curable composition comprising a fluoropolymer and a curable (meth) acrylate monomer is provided. These curable compositions are optically clear or even optically clear because of the high miscibility of the fluoropolymer with the (meth) acrylate monomer. Curable compositions also have relatively low viscosities, allowing them to be applied in a variety of ways, including ink jet printing. Upon curing of the curable composition, the curable composition forms a cured organic layer having a matrix and phase-separated microdomains, wherein the matrix and phase-separated microdomains have different refractive indices, and at least some of the phase-separated microdomains are close to or greater than the wavelength of visible light (400nm to 700 nm). In some embodiments, the phase separated domains are in the range of 100nm to 4,000 nm. Also disclosed herein are methods for making articles having an optical scattering layer.

Disclosed herein are curable compositions. The curable composition comprises at least one fluoropolymer, at least one monofunctional (meth) acrylate, at least one difunctional (meth) acrylate, and at least one initiator. The curable composition typically has a viscosity of less than 30 centipoise at temperatures from room temperature to 60 ℃. Typically, the curable composition is solvent free. In many embodiments, the curable composition is optically clear or even optically clear. The advantage of these relatively low viscosity compositions is that they are ink jet printable. By ink jet printable is meant that the composition is capable of being ink jet printed and does not imply that the composition must be ink jet printed or that the composition has already been ink jet printed. As such, the expression ink jet printable is a compositional limitation of the curable composition, not a process limitation. The ink jet printable material can be applied in a variety of ways.

The curable composition comprises at least one fluoropolymer. The fluoropolymer is a fluorocarbon-based polymer having multiple carbon-fluorine bonds. It is characterized by high resistance to solvents, acids and bases. Fluoropolymers are hydrocarbon polymers in which hydrogen atoms (typically many hydrogen atoms, or even all hydrogen atoms) have been replaced by fluorine atoms.

Fluoropolymers share the properties of fluorocarbons because they are not as susceptible to van der waals forces as hydrocarbons. Thus, fluoropolymers such as fluorocarbons are very stable due to the strength of the carbon-fluorine bond, which is one of the strongest bonds in organic chemistry. The strength is a result of the electronegativity of fluorine, which imparts part of the ionic character through partial charges on the carbon and fluorine atoms, which shortens and strengthens the bond through favorable covalent interactions. In addition, since carbon has a high partial positive charge, multiple carbon-fluorine bonds increase the strength and stability of other nearby carbon-fluorine bonds on the same carbon nanotube. In addition, the multiple carbon-fluorine bonds also enhance the "backbone" carbon-carbon bonds from the inductive effect. Thus, saturated fluorocarbons are more chemically and thermally stable than their corresponding hydrocarbon counterparts and indeed any other organic compound. Saturated fluorocarbons are generally immiscible with most organic solvents (e.g., ethanol, acetone, ethyl acetate, and chloroform), but are miscible with some hydrocarbons (e.g., hexane in some cases). Saturated fluorocarbons have low refractive indices, typically less than 1.45.

The curable composition of the present disclosure comprises at least one fluoropolymer in an amount of 1 to 20% by weight based on 100% by weight of the total curable composition. An example of a suitable fluoropolymer is an amorphous fluoropolymer having a fluorine content of 60% to 70%. By fluorine content is meant that 60% to 70% of the substitutable hydrogen atoms have been substituted by fluorine groups. One particularly suitable class of fluoropolymers are fluoroelastomers. Fluoroelastomers are amorphous specialty fluorocarbon-based synthetic rubbers and do not contain a significant amount of crystallinity. Fluoroelastomers have a wide range of chemical resistance and excellent properties, especially in high temperature applications in different media. Fluoroelastomers are classified according to FKM ASTM D1418& ISO 1629 nomenclature. Such elastomers are a family of fluoroelastomers including copolymers of Hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2), terpolymers of Tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and Hexafluoropropylene (HFP), and specialty elastomers containing perfluoromethyl vinyl ether (PMVE). A particularly suitable fluoroelastomer is a copolymer of vinylidene fluoride (VDF) and Hexafluoropropylene (HFP), such as materials commercially available under the trade names FC 2145, FC 2178 and FC 2211 from 3M Company (3M Company, st. paul, MN), st.

As noted above, fluoropolymers generally have low miscibility with organic solvents and fluids. In the present disclosure, it has been observed that fluoropolymers have high miscibility with (meth) acrylate monomers comprising cyclic moieties in curable compositions. In fact, in many embodiments, the curable composition is optically clear. Other fluoropolymers that can be used are described in jin et al (US 2006/0147177 a 1).

One desirable feature of fluoropolymers is that they have a refractive index that is different from the (meth) acrylate matrix formed by polymerization of the (meth) acrylate monomers described below. Fluoropolymers typically have a refractive index in the range of 1.40-1.41. This refractive index is different from that of the (meth) acrylate matrix, which typically has a refractive index in the range of 1.48 to 1.50.

The curable composition further comprises at least one monofunctional (meth) acrylate. A wide range of monofunctional (meth) acrylates are suitable. In some embodiments, the monofunctional (meth) acrylate comprises a monofunctional methacrylate. In some embodiments, methacrylates are preferred over acrylates because methacrylates polymerize more slowly, allowing for a more controlled reaction rate and thus better control of the diffusion characteristics of the resulting film. Examples include, but are not limited to, acrylamides such as acrylamide, methacrylamide, N-ethylacrylamide, N-hydroxyethylacrylamide, diacetone acrylamide, N-dimethylacrylamide, N-diethylacrylamide, N-ethyl-N-aminoethylacrylamide, N-ethyl-N-hydroxyethylacrylamide, N-dihydroxyethylacrylamide, tert-butylacrylamide, N-dimethylaminoethylacrylamide and N-octylacrylamide. Examples of suitable monofunctional (meth) acrylates include cycloaliphatic methacrylates. Cycloaliphatic compounds are organic compounds that are both aliphatic and cyclic. They contain one or more all-carbon rings, which may be saturated or unsaturated, but which do not have aromatic character. The cycloaliphatic compound may have one or more pendant aliphatic chains attached. In some embodiments, the cycloaliphatic compound may include one or more heteroatoms. Monocyclic cycloalkanes and cycloalkenes include cyclopentane, cyclopentene, cyclohexane, cyclohexene, cycloheptane, cycloheptene, cyclooctane, cyclooctene, and the like. Bicyclic alkanes and alkenes include norbornane, norbornene and norbornadiene. Examples of suitable cycloaliphatic (meth) acrylates include trimethylcyclohexyl 3,3, 5-acrylate and methacrylate, adamantyl 1-acrylate and methacrylate, 3, 5-dimethyladamantyl 3, 5-methacrylate, and isobornyl acrylate and methacrylate. Examples of heteroatom functional cycloaliphatic (meth) acrylates include tetrahydrofurfuryl acrylate and methacrylate. The monofunctional (meth) acrylate may be present in a wide range of amounts. In some embodiments, the monofunctional (meth) acrylate comprises 60 to 95 parts by weight, based on the total weight of the curable components of the curable composition.

Monomers containing unsaturated groups in the form of vinyl groups may also be used. These monomers chemically react with and crosslink in a (meth) acrylate matrix are well known in the art. Preferred examples of vinyl-containing monomers (also containing cyclic moieties) include n-vinylpyrrolidone and n-vinylcaprolactam. A suitable range of the vinyl-containing monomer is 1 to 20 parts by weight based on the total weight of the curable components of the curable composition.

The curable composition further comprises at least one multifunctional (meth) acrylate. In some embodiments, the multifunctional (meth) acrylate comprises a difunctional (meth) acrylate. In some embodiments, the difunctional (meth) acrylate comprises a difunctional methacrylate. Also, as with monofunctional (meth) acrylates, difunctional methacrylates can be particularly suitable because they polymerize more slowly than the corresponding acrylates, allowing for better control of the polymerization rate. Examples of suitable difunctional (meth) acrylates include aliphatic (meth) acrylates having the general formula I:

H₂C＝CR2-(CO)-O-A-O-(CO)-R2C＝CH₂

formula I

Wherein R2 is hydrogen or methyl, (CO) is a carbonyl group C ═ O, and a is a divalent group comprising groups of alkylene and heteroalkylene groups. Examples of the alkylene group include alkylene groups having 4 to 20 carbon atoms, and may include cyclic groups. Examples of heteroalkylene groups include polyoxyethylene groups, polyoxypropylene groups, polythioether groups, and the like. Examples of useful multifunctional (meth) acrylates include, but are not limited to, 1, 6-hexanediol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, propylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, bisphenol A di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, poly (ethylene glycol) di (meth) acrylate, polybutadiene di (meth) acrylate, polyurethane di (meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri-acrylate, pentaerythritol tri and tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, and mixtures thereof, Ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate and ethoxylated and propoxylated versions and mixtures thereof.

The multifunctional (meth) acrylate or crosslinker can be present in a wide range of amounts. In some embodiments, the multifunctional (meth) acrylate comprises 1 to 20 parts by weight based on the total weight of the curable components of the curable composition. The amount and type (identity) of the one or more cross-linking agents may vary, but the total amount of cross-linking agent is typically present in an amount of at least 5 wt.%. By wt% is meant the% by weight of the total curable components of the curable ink composition.

The curable composition further comprises at least one initiator. Typically, the initiator is a photoinitiator, meaning that the initiator is activated by light, typically Ultraviolet (UV) light. Photoinitiators are well known to those skilled in the art of (meth) acrylate polymerization.

Useful photoinitiators include those known to be useful for photocuring free-radical polyfunctional (meth) acrylates. Exemplary photoinitiators include benzoin and derivatives thereof, such as alpha-methyl benzoin; alpha-phenyl benzoin; α -allylbenzoin; alpha-benzyl benzoin; benzoin ethers such as benzil dimethyl ketal (e.g., "OMNIRAD BDK" from IGM Resins USA inc., st. charles, IL, san charles, illinois), benzoin methyl ether, benzoin ethyl ether, benzoin n-butyl ether; acetophenone and its derivatives, such as 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g., from IGM Resins U.S. company of saint charles, illinois, under the trade name OMNIRAD 1173) and 1-hydroxycyclohexyl phenyl ketone (e.g., from IGM Resins U.S. company of saint charles, illinois, under the trade name OMNIRAD 184 (IGM Resins USA inc., st. charles, IL)); 2-methyl-1- [4- (methylthio) phenyl ] -2- (4-morpholinyl) -1-propanone (e.g., commercially available under the trade name OMNIRAD 907 from IGM Resins U.S. company of saint charles, illinois, st. charles, IL); 2-benzyl-2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl ] -1-butanone (e.g., commercially available under the trade name OMNIRAD 369 from IGM Resins USA, Inc., St. Charles, IL, san Charles, Ill.) and phosphine oxide derivatives such as ethyl-2, 4, 6-trimethylbenzoyl phenyl phosphinate (e.g., commercially available under the trade name TPO-L from IGM Resins USA, St. Charles, IL, san Charles, Ill.) and bis- (2,4, 6-trimethylbenzoyl) -phenyl phosphine oxide (e.g., commercially available under the trade name OMNIRAD 819 from IGM Resins USA, St. Charles, IL, san Charles, Ill.).

Other useful photoinitiators include, for example, pivaloin ethyl ether, anisoin ethyl ether, anthraquinones (e.g., anthraquinone, 2-ethylanthraquinone, 1-chloroanthraquinone, 1, 4-dimethylanthraquinone, 1-methoxyanthraquinone, or benzoanthraquinone), halomethyltriazines, benzophenones and derivatives thereof, iodonium salts and sulfonium salts, titanium complexes such as bis (η -2, 4-cyclopentadien-1-yl) -bis [2, 6-difluoro-3- (1H-pyrrol-1-yl) phenyl ] titanium (e.g., available under the trade name CGI 784DC from BASF, Florham Park, NJ, of fremopack, NJ); halomethyl-nitrobenzenes (e.g., 4-bromomethyl nitrobenzene), and combinations of photoinitiators in which one component is a monoacylphosphine oxide or a bisacylphosphine oxide (e.g., BASF, Florham Park, NJ, available under the trade names IRGACURE 1700, IRGACURE 1800, and IRGACURE 1850, and IGM Resins U.S. inc (IGM Resins USA inc., st. charles, IL), santa charles, illinois), new jersey.

Typically, the photoinitiator is used in an amount of 0.01 to 5 parts by weight, more typically 0.1 to 0.5 parts by weight, relative to 100 parts by weight of the total reactive components.

The curable composition may comprise additional optional additives. The optional additives may be reactive or non-reactive. A higher refractive index difference (Δ n) between the minority and majority phases will increase the haze and scattering power of the film. This will enable the use of less fluoropolymer in order to achieve the same optical effect as a larger amount of fluoropolymer with a smaller (Δ n). Less fluoropolymer will allow for a lower viscosity ink formulation, which will also be beneficial for inkjet performance. Metal oxide nanoparticles would be particularly useful for increasing the refractive index of the poly (meth) acrylate matrix phase.

A wide variety of metal oxide nanoparticles are suitable, but as noted above, metal oxide nanoparticles having a high refractive index are desirable because the objective is to increase the refractive index of the curable ink composition. Examples of suitable metal oxide nanoparticles include metal oxides of titanium, aluminum, hafnium, zinc, tin, cerium, yttrium, indium, antimony, and zirconium, as well as mixed metal oxides, such as indium tin oxide. In this context, high refractive index refers to a refractive index of 2.0 or higher. Among the more desirable metal oxide nanoparticles are those of titanium, aluminum and zirconium. Particularly suitable due to their high refractive index are titanium oxide nanoparticles, commonly referred to as titania nanoparticles. In many cases, a single type of metal oxide nanoparticles is used, but mixtures of metal oxide nanoparticles may also be used.

As previously mentioned, the size of such particles is selected to avoid significant visible light scattering. The surface-treated metal oxide nanoparticles may be particles having a (e.g., unassociated) primary particle size or an associated particle size of greater than 1nm, 5nm, or 10 nm. The primary or associated particle size is typically less than 100nm, 75nm or 50 nm. Typically, the primary particle size or associated particle size is less than 40nm, 30nm, or 20 nm. It is desirable that the nanoparticles be non-associated and remain non-associated over time. Their measurement can be based on Transmission Electron Microscopy (TEM) or Dynamic Light Scattering (DLS).

The zirconia nanoparticles and titania nanoparticles may have a particle size of 5nm to 50nm, or 5nm to 15nm, or 8nm to 12 nm. Suitable zirconia (nanoparticles of zirconium dioxide) is available from Nalco Chemical company (Nalco Chemical Co.) under the trade designation "Nalco OOSSOO 8", and from beller company (Buhler AG) (ugville, Switzerland) under the trade designation "Buhler zirconia Z-WO sol". Titanium dioxide nanoparticles (nanoparticles of titanium dioxide) are particularly suitable. Titanium dioxide nanoparticles comprising a mixture of anatase and brookite crystal structures are commercially available from Showa Denko Corp., japan under the trade designation "NTB-1".

The nanoparticles are preferably surface treated to improve compatibility with the organic matrix material and to maintain the nanoparticles unassociated, unagglomerated, or a combination thereof in the curable ink composition. The surface treatment used to produce the surface treated nanoparticles is a silane surface treatment agent comprising at least two silane functional surface treatment agents.

Another particularly suitable optional additive is an adhesion promoter. Adhesion promoters are used as additives or as primers to promote adhesion of coatings, inks or adhesives to the substrate of interest. Adhesion promoters generally have an affinity for the substrate and the coating, ink or adhesive applied. Suitable adhesion promoters are silane-functionalized compounds, titanates and zirconates. Examples of suitable titanates and zirconates include titanium butoxide or zirconium butoxide. Typically, the adhesion promoter, if used, comprises a silane-functionalized compound. Silane-functionalized adhesion promoters are sometimes called coupling agents because they have different functional groups at each end of the compound and are therefore useful for coupling different surfaces, such as inorganic and organic surfaces. A wide variety of silane adhesion promoters are suitable, such as the (meth) acrylate-functionalized alkoxysilane SILQUEST A-174 from Momentive Performance Materials. With this type of adhesion promoter, the alkoxysilane functionality interacts with the inorganic surface and the (meth) acrylate functionality is copolymerized with the curable ink composition. Other examples of suitable silane coupling agents include octadecyltrimethoxysilane, isooctyltrimethoxysilane, hexadecyltrimethoxysilane, hexyltrimethoxysilane, methyltrimethoxysilane, hexamethyldisilazane, hexamethyldisiloxane, aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, 3- (methacryloyloxy) propyltrimethoxysilane, and the like.

Useful additives may include functional group-containing polymers known in the art, such as epoxy groups, allyloxy groups, (meth) acrylate groups, (meth) acrylamide groups, epoxides, episulfide, vinyl, hydroxyl, cyano esters, acetoxy, thiol, silanol, carboxylic acid, amino, phenolic, acetaldehyde, alkyl halide, cinnamic acid, azide, aziridine, alkene, carbamate, imide, amide, alkyne, ethylenically unsaturated groups, vinyl ether groups, and any derivatives and any combinations thereof. Additionally, the polymer additive may be non-reactive, such as poly (methyl methacrylate), poly (vinyl butyral), poly (acrylic acid), poly (vinyl alcohol), and others may be used. These polymers may also include copolymers, that is, polymers made from more than one type of monomer unit during polymerization. The copolymers may comprise different structures such as linear, star, graft, random or block copolymers.

Other optional additives include heat stabilizers, ultraviolet light stabilizers, free radical scavengers, chain transfer agents, photosensitizers, and combinations thereof. Examples of suitable commercially available ultraviolet light stabilizers include those available from BASF corp (BASF corp., Parsippany, NJ) under the trade designation "UVINOL 400"; benzophenone-type ultraviolet light absorbers available under the trade designations "TINUVIN 900", and "TINUVIN 1130" from BASF, Tarrytown, NY. Examples of suitable concentrations of the ultraviolet light stabilizer in the polymerizable precursor range from about 0.1 wt% to about 10 wt%, and particularly suitable total concentrations range from about 1 wt% to about 5 wt%, relative to the total weight of the polymerizable precursor.

Examples of suitable free radical scavengers include Hindered Amine Light Stabilizer (HALS) compounds, hydroxylamines, hindered phenols, and combinations thereof. Examples of suitable commercially available HALS compounds include trade names "TINUVIN 123" and "TINUVIN 292" from BASF. An exemplary range of suitable concentrations of the radical scavenger in the polymerizable precursor is from about 0.05 wt.% to about 0.25 wt.% of the precursor solution.

Articles of manufacture are also disclosed herein. The article comprises: a substrate having a first major surface and a second major surface; and an optical scattering layer on the first major surface of the substrate, wherein the optical scattering layer. The optical scattering layer scatters visible light. The optical scattering layer is prepared by curing the above curable composition. The optical scattering layer is described in detail below.

A wide range of substrates are suitable for use in the articles of the present disclosure. The substrate included in the article may contain a polymeric material, a glass material, a ceramic material, a metal-containing material (e.g., a metal or metal oxide), or a combination thereof. The substrate may comprise multiple layers of materials, such as a support layer, a primer layer, a hard coat, a decorative design, and the like. The substrate may be permanently or temporarily attached to the adhesive layer. For example, a release liner may be temporarily attached and then removed to attach the adhesive layer to another substrate.

The substrate may serve a variety of functions, such as providing flexibility, encapsulation, barrier, stiffness, strength or support, reflectivity, antireflectivity, polarization, or transmissivity (e.g., selective transmission of different wavelengths). That is, the substrate may be flexible or rigid; reflective or non-reflective; visually clear, colored but transmissive, graphical (i.e., with a printed image or indicia), or opaque (e.g., non-transmissive); and polarized or unpolarized.

Exemplary substrates include, but are not limited to, the outer surface of an electronic display, such as a liquid crystal display, an inorganic (LED) or Organic Light Emitting Diode (OLED) display, the outer surface of a window or glazing, the outer surface of an optical element, such as a reflector, polarizer, diffraction grating, mirror or lens, another film, such as a graphic or decorative film, or another optical film, and the like.

Representative examples of polymeric substrates include those comprising polycarbonate, polyesters (such as polyethylene terephthalate and polyethylene naphthalate), polyurethane, poly (meth) acrylates (such as polymethyl methacrylate), polyvinyl alcohol, polyolefins (such as polyethylene and polypropylene), polyvinyl chloride, polyimide, cellulose triacetate, acrylonitrile-butadiene-styrene copolymer, and the like.

The substrate may also include an inorganic layer. The inorganic layer may be made of 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 for use in the metal oxides, metal nitrides and metal oxynitrides, and in particular suitable metals include Al, Zr, Si, Zn, Sn and Ti. One particularly suitable inorganic barrier material is silicon nitride. In some embodiments, the inorganic layer provides an encapsulation and barrier function to prevent water and oxygen from entering the display device.

The articles of the present disclosure may be included in larger articles and devices. In some embodiments, the substrate with the light scattering coating may be incorporated into a display device.

The articles of the present disclosure include an optical scattering layer. The optical scattering layer is prepared by curing the above curable composition. The cured optical scattering layer includes a matrix having microdomains of a material different from the matrix material. The matrix component and the domain component have been found to be more complex than expected from the PIPS (polymerization induced phase separation) model. In the PIPS model, curable compositions comprising a fluoropolymer and a (meth) acrylate monomer that are miscible with each other, and thus are optically clear fluids, are expected to form domains of fluoropolymer within a crosslinked (meth) acrylate matrix upon curing. While this does occur upon curing, the composition of the resulting matrix and domains is much more complex.

The optical scattering layer has at least one type of region of three different types of regions. Each of the regions includes a matrix and phase separated microdomains, wherein the matrix and phase separated microdomains have different refractive indices, and wherein the microdomains are near or greater than the wavelength of visible light. Typically, the wavelength of visible light is in the range of 400 nanometers to 700 nanometers. Generally, the phase separated domains have an average diameter of 100nm to 4,000nm, or 400nm to 2,000 nm, or 400nm to 1,000 nm, or even 400nm to 700 nm. The first type of region is a region in which the substantially continuous matrix comprises a cross-linked (meth) acrylate matrix and phase separated fluorocarbon-rich domains. The second type of region is a region where the substantially continuous matrix comprises a cross-linked (meth) acrylate matrix and the phase-separated microdomains comprise a (meth) acrylate material and a fluoropolymer. In these embodiments, the microdomains may still be described as fluoropolymer-rich microdomains, but the microdomains include both fluoropolymer-rich nanodomains and crosslinked (meth) acrylate nanodomains. The third type of region is one in which the substantially continuous matrix comprises fluorocarbon-rich domains and phase-separated (meth) acrylate-rich domains, wherein the (meth) acrylate-rich domains comprise at least a crosslinked (meth) acrylate material, and may further comprise a fluoropolymer.

The optical scattering layer comprises at least one of the above-mentioned types of regions. In some embodiments, the optical scattering layer includes only one type of region and is substantially uniform throughout the optical scattering layer. In other embodiments, the optical scattering layer includes more than one type of region.

In some embodiments, the optical scattering layer comprises a cured cross-linked (meth) acrylate matrix having fluoropolymer-rich microdomains. In some embodiments, substantially all of the fluoropolymer-rich microdomains comprise fluoropolymer (type 1 regions). In other embodiments, the fluoropolymer-rich microdomains comprise (meth) acrylate material and fluoropolymer (type 2 regions). In these embodiments, the fluoropolymer-rich microdomains include nano-domains of fluoropolymer and nano-domains of cross-linked (meth) acrylate. In some embodiments, the optical scattering layer can include a type 1 region and a type 2 region.

In other embodiments, the cured optical scattering layer comprises (meth) acrylate-rich regions (type 3 regions) in which the substantially continuous matrix is fluorocarbon-rich and the phase-separated microdomains are. Typically, when a type 3 region is present, a region of type 1, type 2, or a combination of type 1 and type 2 is also present. Because the fluorocarbon is present as a minor component (less than 50 wt%) of the curable composition, the presence of fluorocarbon is insufficient to form continuous domains throughout the cured organic layer, and instead, type 3 regions are present in localized regions of the cured optically scattering layer.

As mentioned above, it is undesirable to create three different types of regions in the cured optical scattering layer. The PIPS model will suggest a relatively simple method for forming a cured optical scattering layer from a curable composition comprising a fluorocarbon and a (meth) acrylate material. It is somewhat surprising that the fluorocarbon polymer and (meth) acrylate monomer are miscible because the fluorocarbon polymer and (meth) acrylate polymer are generally incompatible with each other. However, because the two materials are miscible with each other prior to forming the crosslinked poly (methacrylate) matrix, but the fluoropolymer is not miscible with the crosslinked poly (methacrylate) matrix, it is assumed that fluoropolymer domains will be formed when the (meth) acrylate matrix is formed by polymerization. It is desirable that the size of the domains can be controlled such that they are microdomains having an average diameter of 100nm to 4,000nm, or 400nm to 2,000 nm, or 400nm to 1,000 nm, or even 400nm to 700 nm. As mentioned above, the cured optical scattering layer is much more complex than proposed by the PIPS model.

The cured optical scattering layer has been shown as an optical scattering layer, whether it comprises only one type of region or more than one type of region. The fact that the cured optical scattering layer has a haze value of 5% or more when measured as described in the examples section demonstrates that the optical scattering layer can scatter visible light forward as desired.

The complexity of the cured optically scattering layer, i.e. the presence of at most three different types of regions within the layer, is examined by a relatively new technique of Atomic Force Microscopy (AFM) combined with infrared spectroscopy (IR). This new technique is abbreviated AFM-IR. AFM-IR is a technique based on the photo-thermal induced resonance effect (PTIR) and is a combination of Atomic Force Microscopy (AFM) and infrared spectroscopy (IR) for nanoscale characterization. Which provides both morphological and chemical information of sub-50 nm features. The AFM-IR technique uses a gold-coated sharp AFM tip to detect rapid thermal expansion of the sample caused by the absorption of short (10 nanosecond) pulses of IR radiation. When the monochromatic laser radiation is near the IR frequency that excites molecular vibrations in the sample, the light is absorbed and causes rapid thermal expansion of the sample in contact with the AFM tip. This causes the AFM tip to deflect simultaneously and causes the cantilever to "ring down" at its natural deflection resonant frequency as heat is dissipated. These movements of the cantilever are "detected" by a second laser beam reflected from the top of the cantilever and the signal is measured using a position sensitive photodetector. The amplitude of the resonance induced in the cantilever is proportional to the amount of IR radiation absorbed by the sample. Thus, the AFM-IR spectrum is generated by measuring the ring-down amplitude while tuning the IR laser on the IR fingerprint region. Furthermore, the IR laser can be tuned to a fixed wavenumber so that the IR absorption can be measured as a function of the position of the AFM tip as it is scanned across the sample. Thus, a chemical composition map was created to show the distribution of chemical components across the sample.

Also disclosed herein are methods of making the articles. In some embodiments, the method comprises: providing a substrate having a first major surface and a second major surface; providing a curable composition; forming a layer of a curable composition on at least a portion of the first major surface of the substrate; the curable composition layer is cured to form a cured crosslinked optical scattering layer. Curable compositions have been described above and comprise at least one fluoropolymer, at least one monofunctional (meth) acrylate, at least one difunctional (meth) acrylate, and at least one initiator, wherein the curable composition typically has a viscosity of less than 30 centipoise at temperatures from room temperature to 60 ℃. The cured crosslinked layer includes a (meth) acrylate matrix and fluoropolymer-rich microdomains, wherein the microdomains are near or greater than the wavelength of visible light. Generally, the domains range from 100 nanometers to 4,000 nanometers, in some embodiments from 400 nanometers to 2,000 nanometers, from 400 nanometers to 1,000 nanometers, or even from 400 nanometers to 700 nanometers.

The formation of the curable composition layer may be performed by a variety of coating, printing, or other patterning techniques. Printing techniques are particularly suitable because these techniques provide excellent control in the formation of the layers. Examples of suitable printing techniques include screen printing, ink jet printing, flexographic printing, gravure printing, flexographic printing, needle dispensing, and patch coating. In some embodiments, the curable composition is applied by ink jet printing. Typically, the shaping layer has a thickness of 1 to 76 microns, in some embodiments, 1 to 51 microns or even 1 to 25 microns.

Curing of the curable composition is carried out by activating an initiator present in the curable composition to initiate free radical polymerization. Typically, the initiator is a photoinitiator, typically activated by UV or visible light. UV light may be provided by a variety of different sources, such as lamps. The radiation source used for curing may be "internal" (e.g., if a coating is applied to the display, the display sub-pixels themselves may be used for curing) or external (a laser, an array of UV black light tubes, UV-LED lamps, etc.). If an internal light source is used, a red, green or blue photosensitizer may be added to the resin along with a standard free radical initiator. Assuming that the absorption of the visible light photosensitizers do not overlap, a series of red, green, or blue flash lamps on the display can be used to cure the ink over each sub-pixel. Each color flash may have a different intensity corresponding to the desired curing speed of each sub-pixel scattering layer. A blanket UV flood exposure may be used to complete the curing of areas of the coating not directly over the subpixels.

If an external light source is used, raster scanning, laser direct writing, or UV source flood exposure techniques with a photomask may be used. If a laser is used for patterning, the laser may have a different wavelength or intensity required to produce the scattering layer. A laser may be used to illuminate the film at an angle to produce a cone of scattering particles within the film, rather than a column of scattering particles. In a UV source flood exposure, three different photomasks may be used, each photomask including a windowing corresponding to the position of a red, green or blue subpixel, respectively. The same fine metal mask used to evaporate the three different luminescent dyes in an OLED display may also be used as a photomask for the phase separated ink. Different radiation intensities may then be used for each exposure as desired.

Curing may be performed in selective segments of the layer, or the entire layer may be cured. In some embodiments, curing comprises curing selected areas of the layer in a pattern such that the layer comprises a series of microdomains. This pattern-wise curing can be performed by selective irradiation or by using a mask. The selective illumination can be performed in a wide variety of ways. For example, irradiation at different points with different intensities may provide variable irradiation, or irradiation of selective areas with an irradiation source may be performed in the selective areas using a laser or similar light source, followed by curing of the remainder of the surface area with a conventional light source. One layer of the curable composition formulation may be applied as a single film over the entire area of the device, or, for example, three different inkjet print heads may deposit three different ink formulations on each of the R, G and B sub-pixels. Each of these three formulations can be adjusted to correct for imperfections at each emission wavelength.

After deposition of the curable composition, the first (low) radiation intensity may be used to form and lock the scattering domains into the cross-linked matrix. A second radiation pulse (of much higher intensity) may be used to complete the curing of the remaining acrylate monomers. It is likely that higher strengths will also result in phase separated fluoropolymer domains, but these domains will be so small that they can be considered optically insignificant. Other uses of such multi-modal or gradient distributions of domain sizes, such as for some degree of light guidance or optical focusing, are also contemplated.

Upon initiation of polymerization, an optically scattering layer is formed. As described above, three different types of regions may be formed in a layer. The optical scattering layer includes a matrix and phase separated microdomains. The microdomains may be fluoropolymer-rich or (meth) acrylate-rich. Without being bound by theory, since the formation of domains is considered diffusion limited, the rate of formation of the crosslinked poly (meth) acrylate matrix may directly affect the domain size. Since the curing speed of a poly (meth) acrylate matrix can be directly influenced by varying the intensity of the curing radiation, the ability to pattern different degrees of scattering using different intensities of light is expected. For example, low light intensity may be used to produce large fluoropolymer or acrylate microdomains in one region of the layer, and high light intensity may be used to produce small fluoropolymer or (meth) acrylate microdomains in another region of the layer. Different domain sizes will result in variations in haze and optical scattering in each region of the layer. According to mie theory, assuming that the particles are smaller than the wavelength of light, the intensity of scattered light is proportional to the square of the refractive index difference between the two phases and the sixth power of the dispersed phase radius. Other ways of affecting the cure speed include changing the functionality, viscosity, and molecular weight of the (meth) acrylate monomers used in the resin mixture. Thus, when curing is selectively performed (i.e., different areas of the curable composition layer are exposed to different radiation), the formation of micro-domains is likewise different. In other words, selective curing may produce a light-diffusing layer having different microdomains at different points on the layer. Such selectivity is not possible with particle-based light diffusing layers or with the light diffusing layers described in us patent 9238762 (schafer et al), since the light diffusing layers in these documents are identical at all points of the layer.

The method of the present disclosure may be further understood by referring to fig. 1A through 1I. Fig. 1A through 1I illustrate a wide range of curing methods that may be used to prepare the optical scattering layers of the present disclosure. It should be noted that the figures are intended to be exemplary and not drawn to scale.

Fig. 1A shows a curable layer including a substrate layer 10A on which a curable composition 20A is disposed. The curable composition is exposed to actinic radiation 30A. The actinic radiation is typically UV light and it causes the curable composition 20A to cure to form a cured matrix 50A having phase separated microdomains 40A.

Fig. 1B shows a curable layer comprising a substrate layer 10B on which a curable composition 20B is disposed. Exposing the curable composition to different intensities (shown as I)₁、I₂And I₃) 31B, 32B and 33B. Actinic radiation 31B has an intensity I₁Actinic radiation 32B having an intensity I₂Actinic radiation 33B having an intensity I₃Wherein the relative intensity of actinic radiation is: i is₁<I₂<I₃. The actinic radiation is typically UV light and it causes curable composition 20B to cure to form cured matrix 50B having phase separated microdomains 41B, 42B, and 43B. The sizes of the phase separated micro-regions 41B, 42B and 43B are shown to be different. Although the phase separated micro-regions 41B, 42B, and 43B are different, it should be noted that the dimensions are representative and are not drawn to scale.

Fig. 1C shows a curable layer comprising a substrate layer 10C on which a curable composition 20C is disposed. The curable compositions were exposed to actinic radiation 31C, 32C, and 33C of varying intensities. The intensity of actinic radiation 31C is lower than the intensity of actinic radiation 32C, and the intensity of actinic radiation 33C is lower than the intensity of actinic radiation 32C and may be the same or different than the intensity of actinic radiation 31C. The actinic radiation is typically UV light and it causes the curable composition 20C to cure to form a cured matrix 50C having phase separated microdomains 41C, 42C, and 43C. The sizes of the phase separated micro-domains 41C, 42C, and 43C are shown to be different. Although the phase separated micro-regions 41C, 42C and 43C are different, it should be noted that the dimensions are representative and not drawn to scale.

Fig. 1D shows a curable layer including a base layer 10D, a curable composition layer disposed on the base layer and including curable composition sublayers 21D, 22D, and 23D. In this embodiment, the curable composition sublayers may represent, for example, curable compositions having different viscosities. For clarity, three sublayers are shown, but it should be understood that a wide range of sublayers are possible. The sub-layer may be created by a gradient in the intensity of light received throughout the volume of the film. For example, a film comprising molecules that absorb ultraviolet radiation (such as an ultraviolet absorber) may receive a higher light intensity at the top of the film than at the bottom of the film. The curable composition is exposed to actinic radiation 30D. The actinic radiation is typically UV light and it causes the curable composition sublayers 21D, 22D, and 23D to cure to form a cured matrix 50D having phase separated microdomains 41D, 42D, and 43D. The sizes of the phase separated micro-regions 41D, 42D, and 43D are shown to be different. Although the phase separated micro-regions 41D, 42D, and 43D are different, it should be noted that the dimensions are representative and are not drawn to scale.

Fig. 1E shows a curable layer comprising a substrate layer 10E, a curable composition layer disposed on the substrate layer and comprising curable composition sublayers 21E and 22E. In this embodiment, the curable composition sub-layers are different because the surface sub-layer 22E is exposed to an oxygen atmosphere because the curable article is not present in an inert atmosphere such as nitrogen. The curable composition is exposed to actinic radiation 30E. The actinic radiation is typically UV light and it causes the curable composition sublayers 21E and 22E to cure to form a cured matrix 50E having phase separated microdomains 41E and 42E. The presence of oxygen in the surface sub-layer 22E is expected to retard the rate of polymerization in that sub-layer. The sizes of the phase separated micro-regions 41E and 42E are shown to be different. Although the phase separated micro-regions 41E and 42E are different, it should be noted that the dimensions are representative and are not drawn to scale.

Fig. 1F shows a curable layer including a substrate layer 10F on which a curable composition 20F is disposed. A portion of curable composition 20F is blocked by mask 60F. The curable composition was exposed to actinic radiation 30F. Due to the mask 60F, only a portion of the curable composition 20F receives actinic radiation 30F. The actinic radiation is typically UV light, and it causes the curable composition 20F to cure to form a cured matrix 50F having phase separated microdomains 40F in the areas receiving the radiation 30F. Mask 60F is removed and the composition is exposed to actinic radiation 30F'. Actinic radiation 30F' may be the same as or different from actinic radiation 30F. The actinic radiation is typically UV light and it causes the uncured curable composition to cure to form a cured matrix 51F having phase separated microdomains 41F and 42F in the areas where the radiation 30F' is received.

Fig. 1G shows a curable layer including a substrate layer 10G, with a curable composition 20G disposed on the substrate layer. A portion of curable composition 20G is exposed to actinic radiation 70G. Actinic radiation 70G can be, for example, a laser. Due to the narrowness of light source 70G, only a portion of curable composition 20G receives actinic radiation. The actinic radiation cures the curable composition 20G to form a cured matrix 50G having phase separated microdomains 40G in areas that receive radiation 70G. The composition was exposed to actinic radiation 30G. Actinic radiation 30G is typically a flood exposure of UV light and it causes the uncured curable composition to cure to form a cured matrix 51G having phase separated microdomains 41G and 42G in the areas where radiation 30G is received.

Fig. 1H shows a curable layer including a substrate layer 10H on which a curable composition 20H is disposed. Curable composition 20H includes nanoparticles 80H. Curable composition 20H is exposed to actinic radiation 30H. The actinic radiation is typically UV light and it causes curable composition 20H to cure to form cured matrix 50H with phase separated microdomains 40H. The surface of the nanoparticles may be designed to act as seeds to nucleate phase separation, or they may serve other functions, such as changing the refractive index.

Fig. 1I shows a curable layer comprising a substrate layer 10I on which a curable composition 20I is disposed. The tool film 90I has a microstructured pattern on one surface. In step 100, tool film 90I is contacted with curable composition 20I to form a laminate construction. The curable composition is exposed to actinic radiation 30I. The actinic radiation is typically UV light and it causes the curable composition 20I to cure to form a cured matrix 50I having phase separated microdomains 40I. Tool film 90I is then removed in step 110 to produce a structured solidified layer having solidified matrix 50I and phase separated microdomains 40I.

The present disclosure includes the following embodiments:

these embodiments have curable compositions. Embodiment 1 includes a curable composition comprising: at least one fluoropolymer; at least one monofunctional (meth) acrylate; at least one difunctional (meth) acrylate; and at least one initiator.

Embodiment 2 is the curable composition of embodiment 1, wherein the curable composition is free of solvent and has a viscosity of less than 30 centipoise at a temperature of from room temperature to 60 ℃.

Embodiment 3 is the curable composition of embodiment 1 or 2, wherein the at least one monofunctional (meth) acrylate comprises a monofunctional cycloaliphatic (meth) acrylate.

Embodiment 4 is the curable composition of any one of embodiments 1-3, wherein the at least one monofunctional (meth) acrylate comprises a monofunctional cycloaliphatic methacrylate.

Embodiment 5 is the curable composition of any one of embodiments 1 to 4, wherein the at least one difunctional (meth) acrylate comprises a difunctional aliphatic (meth) acrylate.

Embodiment 6 is the curable composition of any one of embodiments 1 to 5, wherein the at least one difunctional (meth) acrylate comprises a difunctional aliphatic methacrylate.

Embodiment 7 is the curable composition of any one of embodiments 1 to 6, wherein the difunctional (meth) acrylate comprises 1 to 20 parts by weight based on the total weight of the curable components of the curable composition.

Embodiment 8 is the curable composition of any one of embodiments 1 to 7, wherein the at least one fluoropolymer comprises 1 to 20 weight percent based on 100 weight percent of the total curable composition.

Embodiment 9 is the curable composition of any one of embodiments 1 to 8, wherein the at least one fluoropolymer comprises an amorphous fluoropolymer having a fluorine content of 60% to 70%.

Embodiment 10 is the curable composition of any one of embodiments 1 to 9, wherein the at least one fluoropolymer comprises a fluoroelastomer.

Embodiment 11 is the curable composition of any one of embodiments 1 to 10, further comprising at least one copolymerizable vinyl monomer.

Embodiment 12 is the curable composition of embodiment 11, wherein the copolymerizable vinyl monomer comprises N-vinyl pyrrolidone or N-vinyl caprolactam monomer.

Embodiment 13 is the curable composition of any one of embodiments 1 to 12, further comprising at least one additive selected from the group consisting of metal oxide nanoparticles, adhesion promoters, functional polymers, heat stabilizers, ultraviolet light stabilizers, free radical scavengers, chain transfer agents, photosensitizers, and combinations thereof.

Articles of manufacture are also disclosed. Embodiment 14 includes an article comprising: a substrate having a first major surface and a second major surface; and an optical scattering layer on the first major surface of the substrate, wherein the optical scattering layer is prepared from a curable composition, wherein the curable composition comprises: at least one fluoropolymer; at least one monofunctional (meth) acrylate; at least one difunctional (meth) acrylate; and at least one initiator; and wherein the optical scattering layer comprises a matrix and phase separated microdomains, wherein the matrix and the phase separated microdomains have different refractive indices, and wherein the microdomains are close to or larger than the wavelength of visible light.

Embodiment 15 is the article of embodiment 14, wherein the optical scattering layer has at least one of three types of regions, wherein: the first type of region comprises a (meth) acrylate matrix having fluorocarbon-rich phase-separated microdomains; the second type of region comprises a (meth) acrylate matrix having fluorocarbon-rich phase-separated microdomains, wherein the fluorocarbon-rich phase-separated microdomains further comprise (meth) acrylate-rich nanodomains; and a third type of region comprises a fluorocarbon-rich matrix having (meth) acrylate-rich phase separated domains.

Embodiment 16 is the article of embodiment 15, wherein the optical scattering layer comprises at least two types of regions of the three types of regions.

Embodiment 17 is the article of embodiment 15, wherein the optical scattering layer comprises three types of regions.

Embodiment 18 is the article of any one of embodiments 14 to 17, wherein at least some of the phase separated microdomains comprise fluorocarbon-rich microdomains.

Embodiment 19 is the article of any one of embodiments 14 to 18, wherein the phase separated microdomains are from 100 nanometers to 4,000 nanometers.

Embodiment 20 is the article of any one of embodiments 14 to 18, wherein the phase separated microdomains are from 400 nanometers to 2,000 nanometers.

Embodiment 21 is the article of any one of embodiments 14 to 18, wherein the phase separated microdomains are from 400 nanometers to 1,000 nanometers.

Embodiment 22 is the article of any one of embodiments 14 to 18, wherein the phase separated microdomains are from 400 nanometers to 700 nanometers.

Embodiment 23 is the article of any one of embodiments 14 to 22, wherein the optical scattering layer comprising phase separated microdomains comprises regions having different concentrations of phase separated microdomains, different sizes of phase separated microdomains, or a combination thereof.

Embodiment 24 is the article of embodiment 23, wherein the optical scattering layer comprises regions having different concentrations of phase separated microdomains, different sizes of phase separated microdomains, or a combination thereof, the optical scattering layer comprising a concentration difference through the thickness of the layer.

Embodiment 25 is the article of embodiment 23, wherein the optical scattering layer comprises regions having different concentrations of phase separated microdomains, different sizes of phase separated microdomains, or a combination thereof, the optical scattering layer comprising concentration differences in regions of the length and width of the layer.

Embodiment 26 is the article of any one of embodiments 14 to 25, wherein the optical scattering layer has a thickness of 1 to 76 microns.

Embodiment 27 is the article of any one of embodiments 14 to 25, wherein the optical scattering layer has a thickness of 1 to 51 microns.

Embodiment 28 is the article of any one of embodiments 14 to 25, wherein the optical scattering layer has a thickness of 1 to 25 microns.

Embodiment 29 is the article of any one of embodiments 14 to 28, wherein the article comprises a display article.

Embodiment 30 is the article of any one of embodiments 14 to 29, wherein the optical scattering layer comprises a structured surface.

Embodiment 31 is the article of embodiment 30, wherein the structured surface comprises a microstructured surface.

Methods of making the articles are also disclosed. Embodiment 32 includes a method of making an article, comprising: providing a substrate having a first major surface and a second major surface; providing a curable composition comprising: at least one fluoropolymer; at least one monofunctional (meth) acrylate; at least one difunctional (meth) acrylate; and at least one initiator forming a layer of the curable composition on at least a portion of the first major surface of the substrate; curing the curable composition layer to form a cured optical scattering layer, the cured optical scattering layer comprising: an optical scattering layer on the first major surface of the substrate, wherein the optical scattering layer comprises a matrix and phase separated microdomains, wherein the matrix and the phase separated microdomains have different refractive indices, and wherein the microdomains are near or greater than the wavelength of visible light.

Embodiment 33 is the method of embodiment 32, wherein the curable composition is free of solvent and has a viscosity of less than 30 centipoise at a temperature of from room temperature to 60 ℃.

Embodiment 34 is the method of embodiment 32 or 33, wherein forming the layer of the curable composition on at least a portion of the first major surface of the substrate comprises printing of the curable composition.

Embodiment 35 is the method of embodiment 34, wherein printing comprises inkjet printing.

Embodiment 36 is the method of any one of embodiments 32 to 35, wherein the phase separated microdomains are from 100 nanometers to 4,000 nanometers.

Embodiment 37 is the method of any one of embodiments 32 to 35, wherein the phase separated microdomains are from 400 nanometers to 2,000 nanometers.

Embodiment 38 is the method of any one of embodiments 32 to 35, wherein the phase separated microdomains are from 400 nanometers to 1,000 nanometers.

Embodiment 39 is the method of any one of embodiments 32 to 35, wherein the phase separated microdomains are from 400 nanometers to 700 nanometers.

Embodiment 40 is the method of any one of embodiments 32-39, wherein curing comprises curing selected areas of the layer in a pattern such that the layer comprises a series of phase separated microdomains.

Embodiment 41 is the method of embodiment 40, wherein patternwise curing comprises exposing different regions of the layer to radiation of different intensities.

Embodiment 42 is the method of embodiment 40, wherein patternwise curing comprises employing a photomask over a portion of the layer and exposing the layer to radiation.

Embodiment 43 is the method of embodiment 42, further comprising removing the photomask and exposing the layer to radiation, wherein the radiation is different than the radiation employed when the photomask is in place.

Embodiment 44 is the method of embodiment 40, wherein patternwise curing comprises curing selected areas of the layer with a laser.

Embodiment 45 is the method of embodiment 44, further comprising curing the remainder of the layer by exposing the remainder of the layer to radiation.

Embodiment 46 is the method of any one of embodiments 32 to 45, wherein the cured optical scattering layer has a thickness of 1 to 76 microns.

Embodiment 47 is the method of any one of embodiments 32 to 45, wherein the cured optical scattering layer has a thickness of 1 to 51 microns.

Embodiment 48 is the method of any one of embodiments 32 to 45, wherein the cured optical scattering layer has a thickness of 1 to 25 microns.

Examples

A curable ink composition is prepared. Materials were applied to the substrate and physical, optical and mechanical properties were evaluated as shown in the examples below. These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. All parts, percentages, ratios, etc. in the examples, as well as the remainder of the specification, are by weight unless otherwise indicated. Unless otherwise indicated, solvents and other reagents used were obtained from Sigma Aldrich Chemical Company of st. The following abbreviations are used herein: nm is nano; mm is millimeter; cm is equal to centimeter; um is micron; m is rice; n ═ newton; mW to milliwatt; min is minutes; k ═ 1,000 (i.e., 15KDa ═ 15,000 daltons molecular weight); Hz-Hz; cPs ═ centipoise; mol is mol; DEG C is centigrade; t ═ transmittance; h-haze; c-sharpness, avg-mean and stdev-standard deviation. The terms "wt%", "wt%" are used interchangeably.

Table 1: material table

Test method

Sample preparation

Coatings for optical testing were made on substrate S1 using a wire wound rod (model: RDS10, RDS Special instruments, Webster, NY) from Webster, N.Y.. Immediately after coating, Ultraviolet (UV) curing of the film was performed using a CA-3200UV-LED curing chamber and an integrated N2 purge (λ 365nm to 400nm, Clearstone Technologies inc., Hopkins, MN).

Samples were prepared by sandwiching the resin between two pieces of primed PET (S1) substrate. The S1/resin/S1 stack was then placed on top of a photomask (IG1) patterned with chromium of varying thickness to achieve several discrete intensity levels across the sample when ultraviolet radiation was passed through the mask. Another piece of bare glass was placed on top of the S1/resin/S1 stack and the entire construction was then clamped into tight contact with the binder clip. A thick piece of black plastic was placed on top of the clamped construction to prevent back reflection of UV from the top of the curing chamber during curing. Curing through a photomask for 30 minutes, and then carrying out a 15 minute photomask-free UV intensity of 95.6mW/cm²Is exposed to light. The intensity of light passing through each of the regions of the photomask was measured with a UV PowerPuck II Electronic meter and Technology (UV PowerPuck II, Electronic Instrumentation and Technology inc., Sterling, VA) radiometer from stirling, virginia, as shown in tables 4 and 5.

Test method 1: transmittance, haze, clarity and b measurement

The measurement of the average transmission, haze clarity and b x was performed based on ASTM D1003-13 using a haze meter (obtained under the trade designation "BYK haze gard Plus, Columbia, MD" from BYK Gardiner). The results are reported in table 5.

The test method 2: viscosity measurement

17mL 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 with a double gap unit allows the flow of recycled water heated to 25 ℃ and 35 ℃ respectively. The system was allowed to equilibrate for 30 minutes before each measurement was taken. The shear rate was ramped from 100Hz to 1000Hz at 100Hz intervals and the measurements were repeated three times. The average and standard deviation of all data points were taken as viscosity in centipoise. The results are reported in table 3.

Test method 3: atomic Force Microscopy (AFM)

Samples of the cured resin between the substrates S1 were cross-sectioned at room temperature using a Leica EM UC6 Microtome. Atomic force microscopy was used to image a cross section of the phase separated ink coating. Imaging was performed under ambient conditions in air on a Bruker Dimension Icon microscope (Bruker Nano inc.,112Robin Hill Road 112, Santa Barbara, CA) operating in tapping mode. A bruke OTESPA silicon cantilever tip with an aluminum back coating was used during operation (nominal spring constant 40N/m, nominal frequency 300kHz, nominal tip radius 8 nm). The image size was 20 microns by 20 microns with data points 1024 by 1024. At each light intensity, domain size analysis was performed on 3 images of each sample. The Nanoscope Analysis v1.7(Bruker, Santa Barbara, Calif.) software was used to obtain accurate measurements of domain size for each measurement. The mean and standard deviation were recorded and tabulated in table 4.

Test method 4: atomic force microscope-Infrared Spectroscopy (AFM-IR)

The samples were cryosectioned to obtain 250nm cross-sectional slides for AFM-IR studies. Cryosections were performed at-40 ℃ using a Leica Ultramicrotome EM UC7 unit. The cross-sectional slices were then transferred to 10mm x 10mm ZnS single crystal planes for AFM-IR testing.

AFM-IR experiments were performed with a nanoIR2-FS platform (Bruker Anasys, Santa Barbara, Calif.). Thin cross-sectional slices were examined in contact mode using a gold plated SiN AFM tip (Anasys Instruments) with a nominal tip radius of 20nm the repetition rate of the IR laser was tuned to match the 2 nd contact resonance of the AFM cantilever to enhance sensitivity.

At two characteristic laser frequencies 1730cm^-1And 1210cm^-1The cross-section of the film sample is infrared mapped, with characteristic laser frequencies being the characteristic IR absorption bands of the methacrylate and fluoroelastomer, respectively.

Examples

Preparation

A stock solution of neat fluoroelastomer in each methacrylate monomer was prepared. Fluoroelastomer pieces were cut from larger pieces into small squares of 2mm x 2mm and added to each pure methacrylate monomer in amber vials. The vial was placed on a roller for two days or until a clear homogenous solution was formed. An aliquot was removed from the stock solution vial and mixed with the other components. For most examples, a 80:20 molar ratio of monofunctional to difunctional monomers was used for the photocurable portion of the formulation. Photoinitiator (PH1) and spacer beads (B1) were added relative to the total weight of the fluoropolymer/monomer solution. The solution was sonicated for 30 minutes or until a homogenous blend was formed. The formulations used in each example are shown in table 2.

Table 2: preparation table

Table 3: viscosity data of uncured inks

Table 4: domain size measurement of cured formulations

Table 5: optical measurement of cured film

AFM and AFM-IR imaging

Fig. 2 and 4 show optical micrographs of cross sections of the films produced in example 2 and example 1, respectively, and via test method 3: analysis was performed by atomic force microscopy. The atomic force microscope IR map clearly shows the spatial distribution of methacrylate and fluoropolymer, confirming the different phase separation. AFM-IR technique for fixing the frequency of IR laser at 1730cm^-1And 1210cm^-1The chemical composition is mapped over a 30 μm by 30 μm region of the cross-section. 1730cm is shown in FIGS. 3B and 3C^-1And 1210cm^-1IR map of (a). FIG. 3A shows an AFM morphology map obtained simultaneously with the IR map. Fig. 3B and 3C clearly identify the different chemical separations between the fluoropolymer phase and the methacrylate phase. The substrate of the image in FIG. 3B is lighter in color on the data scale, indicating that the region is 1730cm^-1Has a higher IR absorption, which corresponds to a C ═ O (carbonyl chemical moiety) stretching mode in the methacrylate phase. FIG. 3C identifies these micro-regions at 1210cm^-1Has a higher IR absorption, which corresponds to the C-F stretch mode in the fluoroelastomer phase. This color reversal between fig. 3B and fig. 3C indicates that the matrix is rich in methacrylate and the domains are rich in fluoroelastomer. In addition, more careful observation of the interior of the fluoroelastomer-rich domains revealed methyl propyl groupsThe nanodomains of the enoate phase, indicate a more complex phase separation phenomenon. To eliminate morphology-induced image artifacts, the absorption intensity ratio of the IR map is calculated. The absorption intensity ratios of the IR maps were calculated using the built-in software of the nanoIR2-FS equipment (Bruker Anasys, Santa Barbara, Calif.). The absorption ratio at two IR laser frequencies is calculated for each pixel on the map. FIG. 3D shows 1210cm^-1Map to 1730cm^-1The absorption intensity ratio of the map is mapped. The greatly improved contrast clearly shows the phase separated morphology of the methacrylate and fluoropolymer. Similarly, fig. 5 shows the morphological and chemical maps of example 1. As shown by the two IR maps (fig. 5B and 5C) and the image ratio (fig. 5D), the methacrylate-rich spherical domains are dispersed in the fluoroelastomer-rich matrix, which is in stark contrast to the phase-separated morphology in fig. 3.

Claims (24)

1. A curable composition comprising:

at least one fluoropolymer;

at least one monofunctional (meth) acrylate;

at least one difunctional (meth) acrylate; and

at least one initiator.

2. The curable composition of claim 1, wherein the curable composition is free of solvent and has a viscosity of less than 30 centipoise at a temperature of from room temperature to 60 ℃.

3. The curable composition of claim 1, wherein the at least one monofunctional (meth) acrylate comprises a monofunctional cycloaliphatic (meth) acrylate.

4. The curable composition of claim 1, wherein the at least one monofunctional (meth) acrylate comprises a monofunctional cycloaliphatic methacrylate.

5. The curable composition of claim 1, wherein the at least one difunctional (meth) acrylate comprises a difunctional aliphatic (meth) acrylate.

6. The curable composition of claim 1, wherein the at least one difunctional (meth) acrylate comprises a difunctional aliphatic methacrylate.

7. The curable composition of claim 1, wherein the difunctional (meth) acrylate comprises from 1 part by weight to 20 parts by weight based on the total weight of curable components of the curable composition.

8. The curable composition of claim 1 wherein the at least one fluoropolymer comprises from 1 to 20 wt% based on 100 wt% of the total curable composition.

9. The curable composition of claim 1 wherein the at least one fluoropolymer comprises an amorphous fluoropolymer having a fluorine content of from 60% to 70%.

10. The curable composition of claim 1, wherein the at least one fluoropolymer comprises a fluoroelastomer.

11. The curable composition of claim 1, further comprising at least one copolymerizable vinyl monomer.

12. The curable composition of claim 11, wherein the copolymerizable vinyl monomer comprises N-vinyl pyrrolidone or N-vinyl caprolactam monomer.

13. An article of manufacture, comprising:

a substrate having a first major surface and a second major surface; and

an optical scattering layer on the first major surface of the substrate, wherein the optical scattering layer is prepared from a curable composition, wherein the curable composition comprises:

at least one fluoropolymer;

at least one monofunctional (meth) acrylate;

at least one difunctional (meth) acrylate; and

at least one initiator; and wherein the optical scattering layer comprises a matrix and phase separated microdomains, wherein the matrix and the phase separated microdomains have different refractive indices, and wherein the microdomains are close to or larger than the wavelength of visible light.

14. The article of claim 13, wherein the optical scattering layer has at least one of three types of regions, wherein:

the first type of region comprises a (meth) acrylate matrix having fluorocarbon-rich phase-separated microdomains;

the second type of region comprises a (meth) acrylate matrix having fluorocarbon-rich phase-separated microdomains, wherein the fluorocarbon-rich phase-separated microdomains further comprise (meth) acrylate-rich nanodomains; and is

The third type of region includes a fluorocarbon-rich matrix having (meth) acrylate-rich phase-separated microdomains.

15. The article of claim 14, wherein the optical scattering layer comprises at least two of the three types of regions.

16. The article of claim 13, wherein the phase separated microdomains are from 100 nanometers to 4,000 nanometers.

17. The article of claim 13, wherein the optical scattering layer comprising phase separated microdomains comprises regions having different concentrations of phase separated microdomains, different sizes of phase separated microdomains, or a combination thereof.

18. The article of claim 13, wherein the optical scattering layer has a thickness of 1 to 76 microns.

19. The article of claim 13, wherein the article comprises a display article.

20. The article of claim 13, wherein the optical scattering layer comprises a structured surface.

21. A method of making an article, the method comprising:

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

providing a curable composition comprising:

at least one fluoropolymer;

at least one monofunctional (meth) acrylate;

at least one difunctional (meth) acrylate; and

at least one initiator, wherein the curable composition has a viscosity of less than 30 centipoise at a temperature of from room temperature to 60 ℃,

forming a layer of the curable composition on at least a portion of the first major surface of the substrate;

curing the layer of curable composition to form a cured optical scattering layer comprising:

an optical scattering layer on the first major surface of the substrate, wherein the optical scattering layer comprises a matrix and phase separated microdomains, wherein the matrix and the phase separated microdomains have different refractive indices, and wherein the microdomains are near or greater than the wavelength of visible light.

22. The method of claim 21, wherein the size of the phase separated domains is in the range of 100 nanometers to 4,000 nanometers.

23. The method of claim 21, wherein curing comprises curing selected areas of the layer in a pattern such that the layer comprises a series of phase separated microdomains.

24. The method of claim 21, wherein the cured optical scattering layer has a thickness of 1 to 76 microns.

Images