High refractive index compositions for coating optical substrates and uses thereof - Patents.com

Abstract

Provided are black coatings on optical substrates, compositions for producing such coatings, and uses of the compositions for edge blackening and stray light control. The coatings of the invention comprise a film formed by a curable composition admixed with nanoparticles and a black pigment, the film having a refractive index greater than 1.75. The curable compositions of the invention include 0-50 parts by weight of a curable polymer, 0-50 parts by weight of a curable monomer, 50-100 parts by weight of nanoparticles, and 0.1-20 parts by weight of a black pigment, the nanoparticles and black pigment being admixed with the curable polymer and monomer. The compositions of the invention exhibit refractive index values ​​that match those of high refractive index glass substrates while providing efficient edge blackening properties.

Description

[Technical field]

[0001] The present invention relates to coating optical substrates with curable compositions containing fillers. More specifically, the present invention relates to black coatings on optical substrates, compositions for producing such coatings, and uses of the compositions for edge blackening and stray light control. [Background technology]

[0002] Edge blackening coatings are applied to the edges of optical substrates or to certain limited locations of optical substrates, specifically substrates where light propagates within the substrate. Typically, coatings are applied to optical components such as lenses, prisms, beam splitters, waveguides, or diffractive optical elements to minimize unwanted reflections from the substrate-air interface of light propagating within the optical substrate. Additionally, edge blackening minimizes light entering the optical substrate from the coated area. Edge areas typically have a rough, unpolished surface. Light reflecting from edges typically leads to stray light, a common limiting factor in the performance of optical systems.

[0003] Reflection of light reaching the substrate-air interface can be minimized by applying an edge blackening coating, and for optimal performance the coating must minimize three effects, shown in Figure 1: 1) reflection at the substrate-coating interface, 2) light entering the substrate from within the optical coating, either due to reflection at the coating-air interface or from outside the coating, and 3) scattering within the optical coating back into the optical substrate.

[0004] To adequately reduce the reflection at the interface between the substrate and the coating (component 1 in Figure 1), the refractive index of the material used for the coating, more specifically the real part of the complex refractive index, must match that of the substrate. However, conventional edge blackening coatings do not work well with high refractive index (RI) substrates because they do not have a high refractive index. The k value, i.e. the complex part of the RI, is always non-zero for black materials, i.e. absorbing materials, and partially influences the reflectance. Optical substrates usually exhibit very high transmission of light of the required wavelengths, with k values ​​close to zero. For example, for normal incidence, the reflectance R at the interface between a transparent substrate and an absorbing coating is given by:

[0005]

number

[0006] where n s and c are the real parts of the complex refractive indices of the substrate and coating, respectively, and k c is the complex part of the refractive index of the coating. For coatings with high k values ​​(>0.05), even if the real parts of the RI are matched, the reflectance due to the k mismatch has a significant contribution to component 1 of the reflectance.

[0007] Once light enters the optical coating, the light absorbing properties of the material, i.e. its blackness, prevent it from re-entering the optical substrate (component 2 in Figure 1). The absorbance or optical density of the material at the required wavelength of light, usually visible light wavelengths, should be high enough so that only a minimal intensity of light re-enters the black coating. Another re-entry mechanism is scattering at the edge blackened coating (component 3 in Figure 1), causing diffuse reflection of the incident light.

[0008] The refractive index is usually increased by using high refractive index fillers. Increasing the refractive index above 1.75, especially above 1.80 at 589 nm, requires a large weight content of filler particles, which limits the use of the material due to high viscosity and poor coating properties unless the formulation is carefully balanced. Summary of the Invention

[0009] The present invention is based on the idea of ​​providing a black coating comprising a film formed by curing a composition of curable polymer and curable monomer mixed with high refractive index nanoparticles and a black pigment.

[0010] In one embodiment, the black coating comprises a film formed by a photocurable composition mixing metal oxide nanoparticles and a black pigment, the cured solid film having a weight percentage of metal oxide nanoparticles greater than 45%, particularly greater than 50%.

[0011] The composition for forming a coating on an optical substrate typically comprises: (one or more) curable monomers; Optionally, one or more curable polymers; Nanoparticles, A black pigment; and optionally an additive.

[0012] The nanoparticles, black pigment, and any optional additives are typically mixed with the curable monomer and any optional curable polymer.

[0013] The compositions may be used for edge blackening or stray light control of high refractive index materials, and are particularly useful for edge blackening of high refractive index materials, including optical substrates.

[0014] More specifically, the invention is characterized by what is stated in the independent claims.

[0015] The present invention provides significant advantages.

[0016] The compositions of the present invention exhibit properties that minimize light reflection at the interface between the optical substrate and the coating, provide efficient edge blackening properties, such as RI values ​​that match high RI glass substrates, minimize reflections due to k value mismatches, and tunable optical density that absorbs light within the coating at various thicknesses while minimizing light re-entry due to scattering.

[0017] Typically, the cured material has a high refractive index, for example, an RI greater than 1.75, or in the range of 1.80 to 2.3, when measured at 589 nm.

[0018] By using nanoparticles as fillers, the RI can be adjusted to match that of various substrates. The optical density, i.e. the logarithm to the base 10 of the reciprocal of the transmittance, can be modified by black pigments. The resin composition of the present invention allows the incorporation of nanoparticles, especially metal oxide nanoparticles, in excess of 45% by weight of the composition.

[0019] The composition may be provided in a solvent-free form to allow for a solvent-free product.

[0020] The viscosity can be adjusted by varying the composition, particularly the relative amounts of polymer(s) and monomer(s), and optionally by utilizing solvents to allow application by a variety of contact and non-contact methods. The materials are usually cured using light activation, particularly UV light. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 illustrates the phenomenon of how a high optical density black coating reduces the light reflectance at the interface between the optical substrate and the black coating. [Diagram 2] FIG. 2 shows the total reflectance of the interface of glass coatings with different black filler formulations. [Diagram 3] FIG. 3 shows the diffuse reflectance of the interface of glass coatings with different black filler formulations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] It should be noted that, as used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly indicates otherwise. Furthermore, it should be understood that, as used herein, the terms "comprises" and / or "comprising" specify the presence of stated features, steps, operations, elements, and / or components, but do not exclude the addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0023] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. Furthermore, terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0024] Unless otherwise stated herein or apparent from the context, percentages referred to herein are expressed as weight percent based on the total weight of the respective composition.

[0025] Unless otherwise specified, properties experimentally measured or determined herein are measured or determined at room temperature, which is 25° C. unless otherwise specified.

[0026] As used herein, the term "about" refers to a value of ±5% of the stated value.

[0027] Unless otherwise specified, properties experimentally measured or determined herein are measured or determined at atmospheric pressure.

[0028] In this specification, unless otherwise specified, the term "average molecular weight" refers to the weight average molecular weight ("M W " or abbreviated as "Mw").

[0029] As used herein, molecular weights are determined by gel permeation chromatography using polystyrene standards.

[0030] "Particle size" and "average particle size" referred to herein refer to the number average particle size based on the largest linear dimension of the particle (also called "diameter"). This is determined by light scattering, specifically dynamic light scattering. The average value reported is the Z-average, an intensity-weighted average of the hydrodynamic diameter.

[0031] As used herein, the term "average particle size" refers to the D50 value of the cumulative volume distribution curve, below which 50% of the volume of the particles have a diameter.

[0032] In this specification, unless otherwise specified, the term "viscosity" refers to a viscosity of 2.5 s at 25°C. -1 "Kinematic viscosity" refers to the dynamic viscosity measured by a rheometer at a shear rate of 100 s.

[0033] In the present context, the term "black pigment" refers to a pigment or particle that has an absorption coefficient in the visible light range, i.e., from about 380 to 740 nm, and that appears visually black. For example, if a black pigment is present at a concentration of 4% in a coating 50 μm thick, the optical density of the coating will be greater than 2.

[0034] In the present context, the term "black coating" means a coating containing a black pigment, which coating has an optical density, measured spectrophotometrically, of greater than 2 in the visible light range, i.e., from about 380 to 740 nm.

[0035] In the present context, "optical substrate" refers to a material or stack of materials that has a high internal transmission (>90%) and a low level of attenuation by scattering or emission (<10%) at the wavelength of light used (usually visible wavelengths). In the present context, the optical substrate to which the coating is applied has a high refractive index, in particular the refractive index of the optical substrate is 1.75 or more, in particular 1.8 or more, in particular about 1.8 to 2.5, usually 1.85 to 2.3, at a wavelength of 589 nm.

[0036] The optical substrate may include an amorphous material such as glass, a crystalline material such as a mineral crystalline material, a polymeric material, or an optical coating including inorganic fillers embedded in a polymeric matrix, etc. The optical substrate may be in the form of a wafer material, for example, and the optical substrate may be comprised of a single layer or may be comprised of a multi-layer structure.

[0037] In one embodiment, the optical substrate is an optical glass, such as flint glass or crown glass, which may further contain additives such as zinc oxide, boron oxide, barium oxide, fluorite, lead, or combinations thereof.

[0038] Embodiments of the present technology provide high RI edge blackening and / or stray light control materials.

[0039] The embodiments further provide a formulation that can be applied onto an optical substrate, such as a glass wafer, to achieve a black coating.

[0040] In embodiments, the formulations of the present invention comprise, consist of, or consist essentially of binders such as curable polymers, particularly prepolymers with crosslinking groups such as siloxane polymers, curable monomers with crosslinking groups such as acrylate groups, mixed with nanoparticles such as titanium dioxide to adjust the refractive index (RI) to match that of the optical substrate, and mixed with black pigments (such as soot or carbon black) to achieve high optical density.

[0041] In an embodiment, the black coating comprises a film formed by a photocurable composition mixing metal oxide nanoparticles and a black pigment, the cured solid film having a proportion of metal oxide nanoparticles of more than 45%, in particular more than 50%, for example 55-90%, or 55-80%, calculated by weight of the film.

[0042] In one embodiment, the black coating comprises a film having a thickness of 1 to 300 μm. In one embodiment, the black coating comprises a film having a thickness of 5 to 100 μm, for example 10 to 50 μm. In one embodiment, the black coating comprises a film having a thickness of 50 μm and exhibiting an optical density of greater than 2 at wavelengths of 400 to 740 nm.

[0043] In one embodiment, the curable monomer is selected from compounds that include crosslinking groups, examples of which include epoxy, glycidyl, vinyl, allyl, acrylate, methacrylate, and combinations thereof.

[0044] The weight ratio of the curable polymer(s) to the curable monomer(s) is generally from 1:100 to 100:1, for example from 10:100 to 100:10, in particular from 15:50 to 50:15.

[0045] In one embodiment, the nanoparticles are selected from non-absorbing metal oxide particles having k values ​​of less than 0.05 at visible wavelengths. Examples of such particles include titanium dioxide, zirconium dioxide, hafnium dioxide, germanium dioxide, aluminum oxide, barium titanate, niobium oxide, and combinations thereof.

[0046] In one embodiment, the nanoparticles are selected from metal oxide particles such as titanium dioxide and zirconium oxide.

[0047] In one embodiment, the nanoparticles have a Z-average particle size of 1 to 200 nm, in particular 2 to 100 nm.

[0048] The Z-average particle size of the nanoparticles affects the viscosity and refractive index of the final formulation. Larger sized nanoparticles usually have a higher refractive index and lower viscosity than smaller sized nanoparticles. For example, by selecting the particle size of the nanoparticles to control and adjust the viscosity, the final formulation can be adapted to various application methods to obtain a practical formulation.

[0049] In one embodiment, the nanoparticles are generally free of agglomerates.

[0050] In one embodiment, the nanoparticles are used as coated nanoparticles, where the coating is used to prevent the particles from agglomerating. Typical nanoparticle coatings are various silane monomers such as methacrylate propyltrimethoxysilane, hexyltrimethoxysilane, glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, etc. Other oxide coatings such as ZrO2, Al2O3, TiO2, etc. may also be used to further stabilize the nanoparticles against photocatalysis.

[0051] In one embodiment, the nanoparticles are provided as a non-dried dispersion.

[0052] In one embodiment, the weight ratio of nanoparticles to the curable composition formed by the curable polymer(s) and the curable monomer(s) is from 95:5 to 50:50, in particular from 90:10 to 50:50, for example from 85:15 to 50:50.

[0053] In one embodiment, the black pigment is selected from soot, carbon black, graphite, synthetic graphite, carbon nanotubes, metal complex dyes, metal oxide particles, and combinations thereof. The black pigment may also include black organic pigments.

[0054] The concentration of the black pigment in the film, calculated from the weight of the curable polymer and nanoparticles, is selected in the range of 0.1-20%, for example 0.5-10%, to adjust the optical density of the cured coating at the desired coating thickness.

[0055] Black pigments, such as carbon black, typically have an average particle size of about 10-100 nm for the primary particles, while the particle size of the secondary particles, such as agglomerates, is about 1-100 μm. The black pigment is selected to minimize light scattering by the pigment and secondary particles, such as agglomerates.

[0056] In one embodiment, the composition comprises a non-agglomerated black pigment.

[0057] In one embodiment, the film is deposited on a glass wafer, specifically on the unpolished surface of the glass wafer.

[0058] In one embodiment, the film is deposited on an optical substrate or stack of optical substrates having a refractive index at 589 nm of greater than 1.75, or greater than 1.8, in particular 1.8 to 2.3, for example 1.80 to 2.1. In one embodiment, the film has a refractive index at 589 nm of 1.80 to 2.05, or 1.90 to 2.1, or 1.95 to 2.1.

[0059] The refractive index of the film deposited on the optical substrate is matched or equal to that of the optical substrate. Thus, in one embodiment, the refractive index of the film differs from that of the optical substrate at 589 nm by no more than ±0.4 units, particularly no more than ±0.1 units, and particularly no more than ±0.05 units.

[0060] In one embodiment, the film coated on a flat glass wafer has a ratio of total reflection to diffuse reflection at the interface between the optical substrate and the coating of more than 10:1, particularly more than 100:1, and typically up to 1000:1.

[0061] In one embodiment, the black pigment is selected to provide a black coating with a diffuse reflectance of less than 1.5%, particularly less than 1.0%.

[0062] The thickness of the optical substrate is usually in the range of 100 μm to 10,000 μm, for example, 300 to 1500 μm.

[0063] In one embodiment, the coating has a thickness of 5-100 μm and is deposited on an optical substrate having a thickness of 100-1500 μm.

[0064] In one embodiment, the total reflection at the interface between the optical substrate and the coating is less than 2%, and in particular less than 1.0% from 420 to 740 nm.

[0065] In one embodiment, the optical substrate including a black coating further comprises a sheet having an edge defining the sheet, the black coating covering at least an area of ​​the sheet adjacent the edge.

[0066] Preferably, the sheet has a width, length and area, and the black coating covers no more than 50%, in particular no more than 25%, of the total area of ​​the sheet. In one embodiment, the black coating comprises an integral layer extending along the width and length of the sheet and covering 5-20% of the total area of ​​the substrate adjacent the edges of the sheet.

[0067] In one embodiment, the composition for coating an optical substrate comprises: up to 50 parts by weight of one or more curable polymers; up to 50 parts by weight of one or more curable monomers; up to 50 to 100 parts by weight, for example 55 to 90 parts by weight or 55 to 85 parts by weight of metal oxide nanoparticles; 0.1 to 20 parts by weight, particularly 0.5 to 10 parts by weight, of a black pigment; Comprising, consisting of, or consisting essentially of.

[0068] In the composition, the nanoparticles and the black pigment are usually mixed, particularly homogeneously, with the curable polymer.

[0069] In one embodiment, the composition always contains at least some curable monomer and optionally a curable polymer.

[0070] In addition to the above components, the composition in some embodiments comprises a solvent capable of at least partially dissolving the curable polymer and, optionally, the monomer. Typically, the solvent forms 0.1 to 50% of the total weight of the composition, for example 1 to 30% of the total weight of the composition.

[0071] In one embodiment, the composition for coating an optical substrate comprises: up to 50 parts by weight of one or more curable polymers; up to 50 parts by weight of one or more curable monomers; 50 to 100 parts by weight, for example 55 to 90 parts by weight or 55 to 85 parts by weight of metal oxide nanoparticles; 0.1 to 20 parts by weight, particularly 0.5 to 10 parts by weight, of a black pigment; 0.1 to 50%, for example 1 to 30%, by weight of the composition, of a liquid capable of at least partially dissolving the curable polymer and, optionally, the monomer; The composition may comprise, consist of, or consist essentially of a mixture of

[0072] In one embodiment, the composition includes a black pigment in a concentration of 0.1 to 10%, for example 0.5 to 6%, calculated from the total weight of the composition excluding the solvent.

[0073] In the above embodiments, there is also typically present from 0.1 to 25%, for example from 1 to 10%, of a photoinitiator or combination of photoinitiators, calculated by weight of the total composition, as described below.

[0074] In one embodiment, the composition is provided in a solvent-free or substantially solvent-free form, in particular the composition comprises less than 5%, in particular less than 2%, of a solvent, calculated on the total weight of the composition.

[0075] The solvent-free and solvent-containing compositions comprise, consist or consist essentially of a mixture of 0-25 parts by weight, e.g. 1-15 parts by weight, of a polymer or polymers, 5-50 parts by weight, e.g. 10-40 parts by weight, of a monomer or monomer mixture, and 0.1-20 parts by weight of a black pigment. Typically, they further contain 0.1-25%, e.g. 1-10%, of (one or more) photoinitiators, calculated on the weight of the total composition.

[0076] In one embodiment, the molecular weight of the curable polymer (M w ) is between 500 and 100,000 g / mol. Typically, curable polymers exhibit reactive groups that allow crosslinking of the polymer during curing.

[0077] In one embodiment, the curable polymer comprises a siloxane polymer.

[0078] To produce siloxane polymers, the chemical formula SiR 1 a R 2 4-a wherein a is 1 to 3 and R 1 is a reactive group, R 2 is an alkyl or aryl group. It also has the chemical formula SiR 3 b R 4 c R 5 4-(b+c) Also provided is a second compound having the formula: 3 is a cross-linking functional group, and R 4 is a reactive group, R 5 is an alkyl or aryl group, b=1-2, and c=1-(4-b). An optional third compound is provided with the first and second compounds and polymerized therewith. An optional fourth compound is provided with the first, second, and third compounds and polymerized therewith. The third and fourth compounds have the formula SiR 9 f R 10 g where R9 is a reactive group, f=1-4, R 10 is an alkyl or aryl group, and g=4-f. When both a third and a fourth compound are provided along with the first and second compounds, the third and fourth compounds are not the same. The first, second, third and fourth compounds may be provided in any order, and oligomeric partially polymerized versions of any of these compounds may be provided in place of the monomers described above.

[0079] In the first, second, third and fourth compounds, and any compounds described below, when such compounds have multiple "R" groups of a single type, such as multiple aryl or alkyl groups, multiple reactive groups, or multiple crosslinking functional groups, the multiple R groups are independently selected to be the same or different at each occurrence. For example, when the first compound is SiR 1 2R 2 2, multiple R 1 The groups are independently selected to be the same or different from each other. 2 The groups are independently selected to be the same or different from one another, as well as for other compounds described herein unless expressly stated otherwise.

[0080] A catalyst is also provided. The catalyst may be a base catalyst or other catalysts described below. The catalyst provided should be capable of polymerizing the first compound and the second compound together. As mentioned above, the order of addition of the compound and catalyst may be in any order. The various components provided together are polymerized to produce a siloxane polymer material with the desired molecular weight and viscosity. After polymerization, particles such as microparticles, nanoparticles, or other desired particles are added along with other optional components such as coupling agents, catalysts, stabilizers, adhesion promoters, etc. The combination of the components of the composition may be performed in any order.

[0081] More specifically, in one example, the siloxane polymer is made by polymerizing a first compound with a second compound, the first compound having the chemical formula I:

[0082]

number

[0083] a is an integer from 1 to 3; R 1 is a reactive group, R 2 is an alkyl group or an aryl group.

[0084] The second compound has the formula II.

[0085]

number

[0086] R 3 is a cross-linking functional group, R 4 is a reactive group, R 5 is an alkyl or aryl group, b is an integer from 1 to 2; and c is an integer from 1 to (4-b).

[0087] The first compound has 1 to 3 alkyl or aryl groups (R 2). Combinations of different alkyl groups, combinations of different aryl groups, or combinations of both alkyl and aryl groups are possible. In the case of alkyl groups, the alkyl preferably contains 1 to 18, more preferably 1 to 14, and especially preferably 1 to 12 carbon atoms. Shorter alkyl groups, such as 1 to 6 carbons (e.g., 2 to 6 carbon atoms), are envisaged. The alkyl groups may be branched in the alpha or beta position with one or more, preferably two, C1 to C6 alkyl groups. In particular, the alkyl groups are lower alkyls containing 1 to 6 carbon atoms, optionally bearing one to three substituents selected from methyl and halogen. Methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl and t-butyl are particularly preferred. Cyclic alkyl groups, such as cyclohexyl, adamantyl, norbornene or norbornyl, are also possible.

[0088] R 2 When is an aryl group, the aryl group can be phenyl, optionally having 1-5 substituents on the ring selected from halogen, alkyl or alkenyl, or naphthyl, optionally having 1-11 substituents on the ring structure selected from halogen, alkyl or alkenyl, which can be optionally fluorinated (including perfluorinated or partially fluorinated). When the aryl group is a polycyclic aromatic group, the polycyclic aromatic group can be, for example, anthracene, naphthalene, phenanthracene, tetracene, which can optionally have 1-8 substituents, and which can optionally be "spaced" from the silicon atom by an alkyl, alkenyl, alkynyl or aryl group containing 1-12 carbons. Single ring structures such as phenyl can also be spaced from the silicon atom in this way.

[0089] The siloxane polymer is prepared by conducting a polymerization reaction, preferably a base-catalyzed polymerization reaction, between a first compound and a second compound. Additional optional compounds, as described below, may be included as part of the polymerization reaction.

[0090] The first compound may include any suitable reactive group R, such as a hydroxyl, halogen, alkoxy, carboxyl, amine, or acyloxy group. 1 For example, when the reactive group of the first compound is an -OH group, more specific examples of the first compound include silanediols such as diphenylsilanediol, dimethylsilanediol, diisopropylsilanediol, di-n-propylsilanediol, di-n-butylsilanediol, di-t-butylsilanediol, diisobutylsilanediol, phenylmethylsilanediol, and dicyclohexylsilanediol.

[0091] The second compound may include any suitable reactive group R, such as a hydroxyl, halogen, alkoxy, carboxyl, amine, or acyloxy group. 4 These reactive groups may be the same or different from the reactive groups of the first compound. In one example, the reactive groups are not -H in either the first compound or the second compound (or any compound participating in the polymerization reaction to form the siloxane polymer, such as a third compound), and the resulting siloxane polymer is free or substantially free of any H groups bonded directly to Si in the siloxane polymer. 5 A group, when present in a second compound, independently represents an R 2 The alkyl or aryl group R 5 is the R of the first compound 2 may be the same as or different from the group.

[0092] The cross-linking reactive group R of the second compound 3 can be any functional group capable of crosslinking by acid, base, radical or thermal catalysis. These functional groups can be, for example, any epoxide, oxetane, acrylate, alkenyl, alkynyl or thiol group.

[0093] In the case of epoxy groups, they may be cyclic ethers having three ring atoms that can be crosslinked using acid, base, or thermal catalysis. Examples of these epoxide-containing crosslinking groups include the glycidoxypropyl group and the (3,4-epoxycyclohexyl)ethyl group.

[0094] In the case of the oxetane group, it may be a cyclic ether having four ring atoms that can be crosslinked using acid, base, or thermal catalysis. Examples of such oxetane-containing silanes include 3-(3-ethyl-3-oxetanylmethoxy)propyltriethoxysilane, 3-(3-methyl-3-oxetanylmethoxy)propyltriethoxysilane, 3-(3-ethyl-3-oxetanylmethoxy)propyltrimethoxysilane, or 3-(3-methyl-3-oxetanylmethoxy)propyltrimethoxysilane.

[0095] In the case of an acrylate group, this may be an acrylate or methacrylate that can be crosslinked using a radical initiator, and can be activated with either UV light or heat. Examples of such acrylate-containing silanes include 3-(trimethoxysilyl)propyl methacrylate, 3-(trimethoxysilyl)propyl acrylate, 3-(triethoxysilyl)propyl methacrylate, 3-(triethoxysilyl)propyl acrylate, 3-(dimethoxymethylsilyl)propyl methacrylate, or 3-(methoxydimethylsilyl)propyl methacrylate.

[0096] In the case of alkenyl groups, such groups may preferably have 2 to 18, more preferably 2 to 14, particularly preferably 2 to 12 carbon atoms. The ethylene group, i.e. the two carbon atoms joined by a double bond, is preferably located at the 2-position or higher relative to the Si atom in the molecule. The branched alkenyl is preferably branched at the alpha or beta position with one or more, preferably two, C1-C6 alkyl, alkenyl or alkynyl groups, optionally fluorinated or perfluorinated alkyl, alkenyl or alkynyl groups.

[0097] In the case of an alkynyl group, it may preferably have 2 to 18 carbon atoms, more preferably 2 to 14 carbon atoms, and particularly preferably 2 to 12 carbon atoms. The ethylene group, i.e., the group of two carbon atoms bonded by a triple bond, is preferably located at the 2-position or higher relative to the Si or M atom in the molecule. The branched alkynyl is preferably branched at the alpha or beta position with one or more, preferably two, C1-C6 alkyl, alkenyl or alkynyl groups, optionally perfluorinated alkyl, alkenyl or alkynyl groups.

[0098] In the case of the thiol group, it can be any organosulfur compound that contains a carbon-bonded sulfhydryl group. Examples of thiol-containing silanes include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

[0099] The reactive group of the second compound may be an alkoxy group. The alkyl residue of the alkoxy group may be linear or branched. Preferably, the alkoxy group is a lower alkoxy group having 1 to 6 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, and a t-butoxy group. Specific examples of the second compound include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(trimethoxysilyl)propyl methacrylate, 3-(trimethoxysilyl)propyl acrylate, (3-glycidyloxypropyl)trimethoxysilane, or 3-glycidyloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, and the like.

[0100] A third and fourth compound are provided with and polymerized with the first and second compounds. The third and fourth compounds can independently have the formula III:

[0101]

number

[0102] R 9 is a reactive group, f=1 to 4, R 10 is an alkyl or aryl group, g=4~f.

[0103] One such example is tetramethoxysilane. Other examples include phenylmethyldimethoxysilane, trimethylmethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltrippropoxysilane, propylethyltrimethoxysilane, phenylmethyldiethoxysilane, trimethylethoxysilane, dimethyldiethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, methyltriethoxysilane, methyltrippropoxysilane, propylethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and the like.

[0104] When a fourth compound is provided in addition to the first, second, and third compounds, the fourth compound is different from the third compound.

[0105] The polymerization of the first compound and the second compound may be carried out using an acid catalyst, but a base catalyst is preferred. The base catalyst used in the base-catalyzed polymerization between the first compound and the second compound may be any suitable basic compound. Examples of these basic compounds include any amine, such as triethylamine, and any barium hydroxide, such as barium hydroxide, barium hydroxide monohydrate, barium hydroxide octahydrate, etc. Other base catalysts include magnesium oxide, calcium oxide, barium oxide, ammonia, ammonium perchlorate, sodium hydroxide, potassium hydroxide, imidazone, or n-butylamine, etc. In a particular example, the base catalyst is Ba(OH)2. The base catalyst may be provided in a lower amount, such as less than 0.5% by weight percent or less than 0.1% by weight percent, based on the combined amount of the first compound and the second compound.

[0106] The polymerization can be carried out in the melt phase or in a liquid medium. The temperature is in the range of about 20-200°C, usually about 25-160°C, in particular about 40-120°C. Generally, the polymerization is carried out at normal pressure, the maximum temperature being determined by the boiling point of the solvent used. The polymerization can be carried out under reflux conditions. Other pressures and temperatures can also be used. The molar ratio of the first compound to the second compound is 95:5-5:95, in particular 90:10-10:90, preferably 80:20-20:80. In a preferred example, the molar ratio of the first compound to the second compound (or the second compound to other compounds involved in the polymerization reaction, i.e. see below) is at least 40:60, or 45:55 or more.

[0107] In one example, the first compound has -OH groups as reactive groups, and the second compound has alkoxy groups as reactive groups. Preferably, the total number of -OH groups relative to the amount of the first compound added is less than or equal to the total number of reactive groups, e.g., alkoxy groups, in the second compound, and is preferably less than the total number of reactive groups in the second compound (or the second compound and other compounds to which alkoxy groups are added, e.g., tetramethoxysilane added or other third compounds involved in the polymerization reaction, as described herein). When the number of alkoxy groups exceeds the number of hydroxyl groups, all or substantially all of the -OH groups are reacted and removed from the siloxane, such as with methanol if the alkoxysilane is a methoxysilane, or ethanol if the alkoxysilane is an ethoxysilane. The number of -OH groups in the first compound and the number of reactive groups (preferably other than -OH groups) in the second compound can be substantially the same, but it is preferred that the total number of reactive groups in the second compound is at least 10% greater than the number of -OH groups in the first compound, preferably at least 25% greater. In some embodiments, the number of reactive groups of the second compound is 40% or more, or 60% or more, 75% or more, or 100% or more more than the number of -OH groups of the first compound. Depending on the compound selected, methanol, ethanol, or other by-products of the polymerization reaction are removed after polymerization, preferably evaporated in a drying chamber.

[0108] The siloxane polymer is first provided in the form of a prepolymer having a weight average molecular weight of, for example, 500 to 5,000 g / mol, for example, 750 to 3,000 g / mol.

[0109] Upon curing, the molecular weight is typically up to 200,000 g / mol.

[0110] In one particular embodiment, the curable polymer has a molecular weight (M w ), wherein the siloxane prepolymer preferably exhibits one or more reactive groups selected from epoxy, glycidyl, vinyl, allyl, acrylate, methacrylate, and combinations thereof.

[0111] In one embodiment, the curable monomer is selected from compounds having crosslinkable reactive groups such as epoxy, glycidyl, vinyl, allyl, acrylate, methacrylate, and combinations thereof.

[0112] Examples of these monomers include methyl acrylate, ethyl acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, butyl (meth)acrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, ethylene diacrylate, tetra(ethylene glycol) diacrylate, ethyl 2-cyanoacrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, 2-carboxyethyl acrylate, trimethylolpropane (EO)n triacrylate, caprolactone acrylate, polypropylene glycol monomethacrylate, cyclic trimethylolpropane formal acrylate, phenoxybenzyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, isobornyl acrylate, o-phenylphenol EO acrylate, 4-tert-butylcyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, methyl ... acrylate, biphenyl methyl acrylate acrylate, lauryl acrylate, lauryl methacrylate, tridecyl acrylate, lauryl tetradecyl methacrylate, isodecyl acrylate, isodecyl methacrylate, phenol (EO) acrylate, phenoxyethyl methacrylate, phenol (EO) 2 acrylate, phenol (EO) 4 acrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, nonylphenol (PO) 2 acrylate, nonylphen (EO)4 acrylate, nonylphenol (EO)8 acrylate, ethoxyethoxyethyl acrylate, stearyl acrylate, stearyl methacrylate, methoxy PEG 600 methacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol (EO)n diacrylate, polypropylene glycol 400 diacrylate, 1,4-butanediol dimethacrylate, polypropylene glycol 700 (EO)6 dimethacrylate, 1,6-Hexanediol (EO)n diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, bisphenol A (EO)10 diacrylate, bisphenol A (EO)10 dimethacrylate, neopentyl glycol dimethacrylate, neopentyl glycol (PO)2 diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, dipropylene glycol diacrylate, bisphenol A (EO)30 diacrylate, bisphenol A (EO)30 dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, bisphenol A (EO)4 diacrylate, bisphenol A (EO)4 dimethacrylate, bisphenol A (EO)3 diacrylate, bisphenol A (EO)3 dimethacrylate, 1,3-Butylene glycol dimethacrylate, tricyclodecane dimethanol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol 400 diacrylate, polyethylene glycol 400 dimethacrylate, polyethylene glycol 200 diacrylate, polyethylene glycol 200 dimethacrylate, polyethylene glycol 300 diacrylate, polyethylene glycol 600 diacrylate, polyethylene glycol 600 dimethacrylate, bisphenol F(EO)4 diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane(EO )3 triacrylate, trimethylolpropane (EO)15 triacrylate, trimethylolpropane (EO)6 triacrylate, trimethylolpropane (EO)9 triacrylate, glycerin (PO)3 triacrylate, pentaerythritol triacrylate, trimethylolpropane (PO)3 triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, pentaerythritol (EO)n tetraacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, etc.,

[0113] In one embodiment, the curable polymer and monomer are cured by free radical curing.

[0114] Typically, monomers and polymers can be cured by photopolymerization using active energy rays such as visible light, electron beams, and especially ultraviolet (UV) rays.

[0115] In an embodiment of the present technology, the composition further comprises at least a photoinitiator(s), and optionally a coinitiator(s), such as a spectral sensitizer(s), and optionally a reducing agent.

[0116] In one embodiment, the composition comprises a photoinitiator or a combination thereof, particularly a UV initiator or a combination of UV initiators, to achieve the curing of the curable polymer. Examples of photoinitiators and UV initiators include carbonyl compounds such as aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazoles, ketoxime esters, borate compounds, azinium compounds, as well as metallocene compounds, active ester compounds and alkylamine compounds.

[0117] In one embodiment, a ketoxime ester is used as the photoinitiator.

[0118] Typically, the content of the photopolymerization initiator or UV initiator is 0.1 to 25% by weight, particularly 0.5 to 20% by weight, for example 0.5 to 10% by weight, of the composition.

[0119] The composition preferably includes an additive capable of adjusting the properties of the composition. Such an additive may be selected from the group of additives capable of adjusting the wettability, adhesion, thixotropy, foamability, and combinations thereof of the composition. Usually, the concentration of the additive is 0.01 to 15%, particularly about 0.1 to 10%, of the total weight of the composition including the solvent.

[0120] In one embodiment, the composition includes a solvent for the curable polymer. The solvent may be selected as needed, particularly when an organic black pigment is used, so that it is also capable of dissolving the black pigment.

[0121] In one embodiment, the solvent primarily dissolves the curable polymer, while the nanoparticles and black pigment are dispersed rather than dissolved in the liquid phase.

[0122] The kinematic viscosity of the composition at 25° C. is generally in the range of 5 mPas to 1,000,000 mPas or 5 mPas to 500,000 mPas, for example about 50 to 50,000 mPas or about 100 to 200,000 mPas, in particular 200 to 100,000 mPas, for example 250 to 10,000 mPas, and preferably 2.5 s-1 The shear rate is measured in a rheometer.

[0123] For application, the viscosity of the composition can be adjusted, for example, by adjusting the solids content of the composition. Generally, the solids content is in the range of 10 to 100% by weight, particularly about 30 to 100% by weight, for example 40 to 100% by weight, or 60 to 100% by weight, particularly 80 to 100% by weight, of the total composition.

[0124] In one embodiment, the viscosity of the composition is adjusted by adjusting the amount of solvent for the curable polymer. Thus, the viscosity can be adjusted by adding 10 to 200 parts by weight of a liquid capable of dissolving the curable polymer for every 100 parts by weight of solids formed by the polymer, nanoparticles and black pigment.

[0125] The solvent is selected from the group of organic solvents such as, for example, ketones, ethers, alcohols, esters, etc. Specific examples include acetone, tetrahydrofuran (THF), toluene, methanol, ethanol, 2-propanol, propylene glycol monomethyl ether, methyl-tert-butyl ether (MTBE), propylene glycol propyl ether, propylene glycol propyl ether (PnP), propylene glycol monomethyl ether acetate (PGMEA), and propylene glycol monomethyl ether PGME.

[0126] In one embodiment, propylene glycol monomethyl ether acetate (abbreviated as "PGMEA") is used.

[0127] In one embodiment, the viscosity of the composition is adjusted by adjusting the amount of monomer. This allows the provision of a solvent-free composition having a desired viscosity. More specifically, in one embodiment, 50-100% of the curable components of the coating are provided by the monomers in the composition, the percentage being calculated from the total weight of the curable components, in particular the polymer(s) and the monomer(s).

[0128] In one embodiment, in a composition for producing a coating having a RI of 1.9 or greater, 80-100% of the hardenable components of the coating are provided by the monomers in the composition.

[0129] In one embodiment, the composition for coating an optical substrate comprises: adding metal oxide nanoparticles in a liquid phase to the curable monomer(s) and the curable polymer(s) to obtain a mixture; Evaporating at least a portion or all of the liquid phase; adding a black pigment, a curing catalyst and additives to the mixture; Offered by.

[0130] The mixture of polymer, monomer and nanoparticles typically becomes a viscous liquid or syrup after evaporation of the solvent.

[0131] In one embodiment, a black pigment is added to a mixture formed with other ingredients to form a modified mixture which is then milled to disperse or dissolve the black pigment.

[0132] In one embodiment, agglomeration of the black pigment is prevented during preparation of the composition.

[0133] The composition can be applied onto the surface of the substrate by several application methods.

[0134] In one embodiment, the application method is selected from the group consisting of non-contact or contact methods, in particular from the group of dispensing, spraying, slit coating, spin coating, doctor blade coating, curtain coating, non-contact or contact painting and printing, such as flexographic printing or screen printing.

[0135] The composition is then cured by exposure to light, such as UV light, to form a cured film. As a result, the polymers and monomers harden and form a crosslinked network on the surface. This polymer matrix adheres to the surface and binds the nanoparticles and black pigment thereto.

[0136] The UV light used to achieve photocuring typically peaks in the range of 250 nm to 450 nm, and when using a single wavelength UV light such as an LED, the wavelength is typically selected from one or more of 285 nm, 300 nm, 310 nm, 365 nm, 385 nm, 395 nm, and 405 nm. The energy amount of the UV light, according to one embodiment, is 1 to 500 J / cm. 2 , for example 5 to 100 J / cm 2 , e.g. 10~50J / cm 2 The range is.

[0137] In one embodiment, the composition is used for blackening the high refractive index edges of high refractive index materials, which typically comprise a glass substrate, particularly a glass substrate having an unpolished rough surface onto which the composition is applied.

[0138] By applying the composition in a solvent-free form, the solvent does not evaporate or does not substantially evaporate during curing, resulting in the formation of a uniform film on the surface and the uniform distribution of the nanoparticles and black pigment on the surface.

[0139] The following non-limiting examples illustrate some embodiments. EXAMPLES

[0140] (Synthesis of siloxane polymer)

[0141] A 500 mL round bottom flask equipped with a stir bar and reflux condenser was charged with diphenylsilanediol (60 g, 45 mol%), [3-(methacryloyloxy)propyl]trimethoxysilane (55.12 g, 36.7 mol%) and tetramethoxysilane (17.20 g, 18.3 mol%). The flask was heated to 80° C. under nitrogen atmosphere and 0.08 g of barium hydroxide monohydrate dissolved in 1 mL of methanol was added dropwise to the mixture of silanes. The silane mixture was stirred at 80° C. for 30 min during which time the diphenylsilanediol reacted with the alkoxysilane. After 30 min the methanol formed was evaporated under vacuum. The viscosity of the siloxane polymer was 1200 mPas, M w was 1200 g / mol.

[0142] (Formation of the composition)

[0143] The siloxane polymer from the previous step was mixed with a curable monomer and a solution of TiO2 nanoparticles in PGMEA to achieve a predetermined ratio of polymer to nanoparticles. The solvent was evaporated under vacuum using a rotary evaporator, and the curing catalyst, additives, and black absorbing pigment were added and the formulation was thoroughly mixed. Finally, the composition was milled using a three-roll mill to obtain a homogenous mixture.

[0144] Six different formulations (Formulations 1-6) were made using three different nanoparticle contents and two types of TiO2 nanoparticles (Nanoparticle A with Z-average of 37 nm and Nanoparticle B with Z-average of 81 nm). The compositions by weight percent are listed in Table 1.

[0145] The refractive index of the formulation was measured from the formulation before adding the black absorbing pigment. Samples of the siloxane polymer and nanoparticle solutions were spin-coated onto silicon wafers and exposed to a 405 nm UV-LED and 20 J / cm2. 2 The resin was cured at a dose of 1000 nm. The refractive index was measured using an ellipsometer (Woollam alpha-SE) at a wavelength of 589 nm. The viscosity of the final formulation was measured using a rheometer at a shear rate of 10 1 / s.

[0146] [Table 1]

[0147] The results show that the TiO2 particle size is important in controlling both the viscosity and refractive index of the formulations in the solvent-free state. When the TiO2 particle size is small, the formulation has a higher viscosity than the formulations with larger particle size. At the highest nanoparticle content (formulations 3 and 6), the formulations with small nanoparticles are dry and the viscosity cannot even be measured.

[0148] Another finding is the refractive index of the formulation. Larger particle size TiO2 nanoparticles have a higher refractive index than smaller particle size nanoparticles in the same formulation. Smaller particle sizes are favored in the formulation due to their lower scattering cross section, improving performance. Scattering by larger nanoparticles contributes to the reflectivity at the interface between the optical substrate and the coating by creating diffuse reflection.

[0149] Another set of compositions is made by varying the black pigment / filler used. Formulations 7-11 were made similar to formulation 1, but with different pigment types / fillers. Three carbon black powders were tested: Furnace Black 47250 from Kremer Pigment, MA11 carbon black (average particle size 29 nm) from Mitsubishi Chemical, and M1100 carbon black from Cabot (surface treated for better dispersion). One black pigment, X55 from BASF, was also tested, and a PGMEA dispersion of MA11 was made by rock milling MA11 in a PGMEA solution (20% total solids) with 30% by weight of PX4310 from Efka. For the MA11 dispersion, carbon black was added prior to the solvent evaporation step to remove excess PGMEA from the dispersion. The composition by weight percent of formulations 7-11 is shown in Table 2.

[0150] [Table 2]

[0151] For reflectance studies, the formulations were applied as 60 μm layers on high refractive index glass substrates (RI 1.8 at 589 nm) by doctor blading. After application as thin films, 20 J / cm 2 The films were UV cured using a 405 nm UV-LED with a UV dose of 10 ...

[0152] The ability of the formulations to function as edge blackening materials is demonstrated by measuring the reflectance from the interface between high index glass and formulations 7-11. Reflectance was measured using a Konica Minolta CM-3600A spectrophotometer, which uses an integrating sphere and can measure diffuse and total reflectance. The angle of incidence of the light is 8°. The samples were placed in the instrument with the uncoated glass side facing the light beam. Note that with this setup, the reflectance of the glass-coating interface cannot be measured without the reflectance from the air-glass interface. Therefore, this reflectance is corrected from the reflectance data as follows:

[0153] First, measure the reflectance of a clean substrate. Assume that the reflectance of the substrate, R, has only a specular reflection component. The clean substrate has two identical surfaces with reflectance r1, and the measured reflectance can be approximated from the reflectance as follows:

[0154]

number

[0155] The single interface reflectance is calculated from the measured substrate data using the previous formula.

[0156] From the reflectance of the air-glass interface r1 and the reflectance of the glass-coating interface r2, the reflectance of the sample coating can be approximated as follows:

[0157]

number

[0158] The measured diffuse reflectance component is corrected by a simplified correction factor (1-r1) -2 to correct for the loss of intensity of the incident light at the air-glass interface and for the scattered light reflection at the glass-air interface. The correction for the scattered light reflection is simplified by using the same reflectance as the air-glass interface measured at an 8° angle of incidence, but this results in an underestimation of the correction.

[0159] The calculated reflectance values ​​r2 of the glass coating and interface are shown in Figure 2 (total reflectance) and Figure 3 (diffuse reflectance). The reference value for uncoated glass is reflectance r1.

[0160] The results show that the black pigment / filler has a significant effect on the total reflectance, especially the diffuse reflectance included in the total reflectance value. This shows how much scattering caused by the black pigment filler affects the performance of the edge blackening material. The measurements show that the diffuse reflectance dominates the total reflectance since the refractive index difference is minimized.

[0161] The lowest total and specular reflectance is obtained with X55 black pigment, which is dissolved in the resin system, so scattering from the black pigment is very low. The second lowest total and specular reflectance is obtained with Cabot M1100 carbon black, which has been surface treated to improve dispersibility. Mitsubishi MA11 clearly improves diffuse reflectance when the carbon black is dispersed in PGMEA using a dispersant, but the total reflectance is higher than that of MA11 used as a powder. Untreated high particle size carbon black 47250 can have a higher reflectance because light scattering can be greater between the resin and the black filler.

Claims

1. A black coating, 1. A black coating comprising a film formed from a photocurable composition incorporating metal oxide nanoparticles and a black pigment, the cured solid film having a weight percentage of metal oxide nanoparticles greater than 45%.

2. 10. The black coating of claim 1, wherein the film has a refractive index greater than 1.75, the refractive index measured at 589 nm.

3. The black coating according to claim 1 or 2, wherein the film has a thickness of 1 to 300 μm.

4. 3. The black coating of claim 1, wherein the film has an optical density of greater than 2 at wavelengths from 400 to 740 nm.

5. 3. The black coating according to claim 1 or 2, wherein the nanoparticles are selected from non-absorbing metal oxide particles, such as titanium dioxide, zirconium dioxide, hafnium dioxide, aluminum oxide, germanium dioxide, barium titanate, niobium oxide and combinations thereof, and have a Z-average particle size of 1 to 200 nm, in particular 2 to 100 nm.

6. 3. The black coating of claim 1, wherein the black coating has a refractive index, the complex part of the refractive index being less than 0.

05.

7. 3. The black coating according to claim 1 or 2, wherein the weight ratio of nanoparticles to curable component is from 95:5 to 50:50, in particular from 90:10 to 50:50, for example from 85:15 to 50:

50.

8. 3. The black coating of claim 1, wherein the black pigment is selected from soot, carbon black, carbon nanotubes, graphite, organic pigments, metal complex dyes, and metal oxide particles, and combinations thereof.

9. 3. The black coating according to claim 1, wherein the black pigment is selected to obtain a black coating with a diffuse reflectance of less than 1.5%, in particular less than 1.0%.

10. 3. The black coating according to claim 1, wherein the film is on an optical substrate and the refractive index of the film is equal to the refractive index of the optical substrate, in particular the refractive index of the film is no more than ±0.4 units, in particular no more than ±0.1 units, in particular no more than ±0.05 units from the refractive index of the optical substrate, the refractive index being measured at 589 nm.

11. 3. The black coating according to claim 1 or 2, wherein the film is deposited on an optical substrate or stack of optical substrates having a refractive index greater than 1.75, in particular greater than 1.

80.

12. 3. The black coating of claim 1, wherein the total reflection at the interface between the optical substrate and the coating film is less than 2% from 400 to 740 nm.

13. 3. The black coating of claim 1 or 2, wherein the composition is cured by UV light.

14. The composition comprises: 0 to 50 parts by weight of a curable polymer; Monomer in an amount of up to 50 parts by weight; 50 to 100 parts by weight of nanoparticles; 0.1 to 20 parts by weight, particularly 0.5 to 5 parts by weight, of a black pigment, 3. The black coating of claim 1, wherein the nanoparticles and black pigment are mixed with a curable polymer and a curable monomer.

15. The curable polymer, if present, exhibits one or more reactive groups, in particular selected from epoxy, glycidyl, vinyl, allyl, acrylate, methacrylate and combinations thereof, and preferably has a molecular weight (M ｗ ), 3. The black coating of claim 1 or 2, wherein the curable monomer is selected from compounds having crosslinkable reactive groups such as epoxy, glycidyl, vinyl, allyl, acrylate, methacrylate, and combinations thereof.

16. 1. A composition for a cured solid coating of an optical substrate, comprising: 0 to 50 parts by weight of a curable polymer; Monomer in an amount of up to 50 parts by weight; 50 to 100 parts by weight of nanoparticles; 0.1 to 20 parts by weight of a black pigment; The nanoparticles and black pigment are mixed with a curable polymer and a curable monomer to form a cured solid coating composition for an optical substrate.

17. The curable polymer has a molecular weight (M ｗ 17. The composition of claim 16, wherein the prepolymer is selected from a prepolymer having a hydroxyl group selected from the group consisting of hydroxyl, hydroxypropyl ...

18. 18. The composition of claim 16 or 17, wherein the curable monomer exhibits one or more reactive groups selected from epoxy, glycidyl, vinyl, allyl, acrylate, hydride, thiol, methacrylate, and combinations thereof.

19. 18. The composition according to claim 16 or 17, wherein the nanoparticles have a Z-average particle size of 1 to 200 nm, in particular 2 to 100 nm, selected from metal oxide particles such as titanium dioxide, zirconium dioxide, hafnium dioxide, aluminum oxide, germanium dioxide, barium titanate, niobium oxide and combinations thereof.

20. 18. The composition according to claim 16 or 17, wherein the weight ratio of the nanoparticles to the curable component is from 95:5 to 50:50, in particular from 90:10 to 50:50, for example from 85:15 to 50:

50.

21. 18. A composition according to claim 16 or 17, comprising black pigment in a concentration of from 0.1 to 10%, such as from 0.5 to 6%, calculated on the total weight of the composition excluding solvent.

22. 18. The composition of claim 16 or 17, comprising a solvent for modifying the viscosity of the composition, said solvent also being capable of dissolving said black pigment, if desired.

23. 18. A composition according to claim 16 or 17, wherein the solids content of the composition is from 60 to 100% by weight, in particular from 80 to 100% by weight, the remainder comprising the solvent.

24. A composition according to claim 16 or 17, comprising from 0.1 to 25%, such as from 1 to 10%, of the total weight of the composition of a photoinitiator or a combination of photoinitiators.

25. 18. The composition of claim 16 or 17, comprising an additive capable of adjusting the properties of the composition selected from the group consisting of wetting, adhesive, thixotropic, foaming, and combinations thereof.

26. Using a rheometer, 25°, 10 s －１ 18. The composition of claim 16 or 17, having a kinematic viscosity of 5 mPas to 1,000,000 mPas, for example about 50 to 50,000 mPas, at a shear rate of 1000 kJ / min.

27. up to 50 parts by weight, in particular 1 to 15 parts by weight, of a curable polymer(s); up to 50 parts by weight, in particular 10 to 40 parts by weight, of curable monomer(s); 50 to 100 parts by weight of nanoparticles; 0.1 to 20 parts by weight, particularly 0.5 to 5 parts by weight, of a black pigment; If necessary, from 0.1 to 50%, in particular from 1 to 30%, of a solvent calculated on the total weight of the composition; 18. The composition of claim 16 or 17, comprising:

28. 18. The composition of claim 16 or 17, comprising less than 5% solvent, calculated on the total weight of the composition.

29. An optical substrate provided with the black coating according to claim 1 or 2.

30. 30. The optical substrate of claim 29, comprising a sheet having an edge defining the sheet, the black coating covering at least an area of ​​the sheet adjacent the edge.

31. 30. The optical substrate of claim 29, comprising a sheet having a width, length and area, wherein the black coating covers no more than 50%, in particular no more than 25%, of the total area of ​​the sheet.

32. 30. The optical substrate of claim 29, wherein the black coating comprises an integral layer extending along the width and length of the sheet and covering 5-20% of the total area of ​​the substrate adjacent the edges of the sheet.

33. 18. Use of a composition according to claim 16 or 17 for blackening the high refractive index edges of high refractive index materials or for stray light control.

34. 34. The use according to claim 33, wherein the high refractive index material comprises an optical substrate, in particular a glass substrate, onto which the composition is coated.

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