Active energy ray curable composition and cured product thereof

Abstract

The present invention can provide: an active energy ray-curable composition having good mold releasability and a high refractive index and low viscosity; and a cured product of the active energy ray-curable composition. The active energy ray-curable composition according to the present invention contains inorganic nanoparticles (A), a (meth)acrylate compound (B), and a photopolymerization initiator (C). The (meth)acrylate compound (B) contains a monofunctional (meth)acrylate (B1), the content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) is at least 70 mass%, and the mass blending ratio [(A) / (B1)] of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) is in the range of 0.5-3.

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable composition and a cured product thereof. This application claims priority based on Japanese Patent Application No. 2022-106541 filed on June 30, 2022, and Japanese Patent Application No. 2022-146130 filed on September 14, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, optical sheets that have functions such as improving brightness and widening the viewing angle have been used in displays such as liquid crystal display devices. Such optical sheets typically have a substrate and an optical functional layer on the substrate that has a fine uneven structure. The uneven structure modulates light through geometric optical effects such as refraction, thereby achieving the desired function. Since such uneven structures are mainly produced by a method of shaping a resin material using a mold, the material used for the optical functional layer is required to be solvent-free and have low viscosity. Furthermore, the optical functional layer is required to be undamaged when peeled (released) from the mold after curing. On the other hand, materials used in the optical functional layer are required to have a high refractive index in line with the trend toward thinner displays and reduced power consumption, etc. To meet this demand, methods have been proposed, such as using monofunctional (meth)acrylates with high refractive index and low viscosity, or adding organic or inorganic fine particles with high refractive index (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 250721 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-249439 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-85539 Summary of the Invention [Problem to be solved by the invention]

[0004] However, resins with a low content of polyfunctional (meth)acrylates have fewer branches in the polymer structure after curing, which can lead to problems such as damage during demolding and resin residue remaining on the mold. Therefore, there was a demand for a material that has good demolding properties, a high refractive index, and low viscosity.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an active energy ray-curable composition and a cured product thereof, which have good mold releasability, a high refractive index, and a low viscosity. [Means for solving the problem]

[0006] The present invention was based on the finding that by setting the content of monofunctional (meth)acrylate in the (meth)acrylate compound within a specific range and blending a certain amount of inorganic nanoparticles, a high refractive index can be achieved while also exhibiting good releasability, leading to the filing of a patent application. The present disclosure includes the following embodiments. [1] An active energy ray-curable composition containing inorganic nanoparticles (A), a (meth)acrylate compound (B), and a photopolymerization initiator (C), the (meth)acrylate compound (B) contains a monofunctional (meth)acrylate (B1), the content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) is 70 mass% or more, The active energy ray-curable composition, wherein the mass blending ratio of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) [(A) / (B1)] is in the range of 0.5 to 3. [2] The active energy ray-curable composition according to [1], wherein the content of the inorganic nanoparticles (A) in the active energy ray-curable composition is 30 mass % or more. [3] The active energy ray-curable composition according to [1] or [2], wherein the inorganic nanoparticles (A) are at least one selected from the group consisting of zirconia, silica, barium sulfate, zinc oxide, barium titanate, cerium oxide, alumina, and titanium oxide. [4] The (meth)acrylate compound (B) further contains a polyfunctional (meth)acrylate (B2), the content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) is in the range of 70 to 90 mass %, The active energy ray-curable composition according to any one of [1] to [3], wherein the content of the polyfunctional (meth)acrylate (B2) in the (meth)acrylate compound (B) is in the range of 10 to 30 mass %. [5] The active energy ray-curable composition according to any one of [1] to [4], wherein the monofunctional (meth)acrylate (B1) contains a compound containing two aromatic rings in one molecule. [6] The active energy ray-curable composition according to [5], wherein the content of the compound containing two aromatic rings in one molecule in the monofunctional (meth)acrylate (B1) is 50 mass% or more. [7] Further containing a dispersant (D), the dispersant (D) contains a phosphate ester compound, The active energy ray-curable composition according to any one of [1] to [6], wherein the phosphate ester compound has at least one (meth)acryloyl group and at least one polyester chain. [8] The active energy ray-curable composition according to any one of [1] to [7], which has a viscosity at 25°C of 1200 mPa·s or less. [9] A cured product of the active energy ray-curable composition according to any one of [1] to [8].

[10] The cured product according to [9], having a refractive index (589 nm) at 25°C of 1.65 or more.

[11] An optical sheet comprising the cured product according to [9]. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an active energy ray-curable composition having good mold releasability, a high refractive index and a low viscosity, and a cured product thereof. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention will be described in further detail below, but the present invention is not limited to the following embodiments.

[0009] The symbol "to" means greater than or equal to the value before "to" and less than or equal to the value after "to". "(Meth)acrylic" is a general term for acrylic and methacrylic, and "(meth)acrylate compound (B)" is a general term for acrylate compounds and methacrylate compounds.

[0010] (Active energy ray-curable composition) The active energy ray-curable composition according to this embodiment contains inorganic nanoparticles (A), a (meth)acrylate compound (B), and a photopolymerization initiator (C). The (meth)acrylate compound (B) contains 70 parts by mass or more of a monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B). The mass ratio of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) [(A) / (B1)] is in the range of 0.5 to 3.

[0011] [Inorganic nanoparticles (A)] The inorganic nanoparticles (A) according to this embodiment are preferably one or more types selected from the group consisting of zirconia, silica, barium sulfate, zinc oxide, barium titanate, cerium oxide, alumina, and titanium oxide. The crystalline structure of the inorganic nanoparticles (A) according to this embodiment is not particularly limited, but for example, when the inorganic nanoparticles are zirconia, a monoclinic system is preferred because it provides excellent dispersion stability and a cured product with high light transmittance and refractive index.

[0012] The inorganic nanoparticles (A) according to this embodiment can be any known ones, and the shape of the particles is not particularly limited, but may be, for example, spherical, hollow, porous, rod-like, plate-like, fibrous, or amorphous. Among them, spherical nanoparticles are preferred because they have excellent dispersion stability and can produce cured products with high light transmittance and refractive index.

[0013] <Zirconia nanoparticles> The inorganic nanoparticles (A) according to this embodiment are preferably zirconia nanoparticles. The zirconia nanoparticles can be any known nanoparticles, and the shape of the particles is not particularly limited, but may be, for example, spherical, hollow, porous, rod-like, fibrous, etc., and among these, spherical is preferred. The average primary particle size of the zirconia nanoparticles according to this embodiment is preferably 1 to 50 nm, more preferably 1 to 30 nm. Furthermore, the crystal structure is not particularly limited, but a monoclinic system is preferred. The average primary particle size in the present invention can be measured by a method of directly measuring the size of primary particles from an electron micrograph using a TEM (transmission electron microscope). For example, the measurement method includes measuring the minor axis diameter and major axis diameter of each primary particle of inorganic fine particles and taking the average of the measured diameters as the average primary particle size of the primary particles. Specific examples of zirconia nanoparticles according to this embodiment include UEP-100 (average primary particle diameter: 11 nm) manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd. and PCS (average primary particle diameter: 20 nm) manufactured by Nippon Denko Corporation.

[0014] The mass ratio of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) [(A) / (B1)] is in the range of 0.5 to 3, preferably in the range of 0.7 to 2.5, more preferably in the range of 0.85 to 2, and even more preferably in the range of 1 to 1.5. By adjusting it to these ranges, both good releasability and low viscosity can be achieved.

[0015] [(Meth)acrylate compound (B)] The (meth)acrylate compound (B) according to this embodiment is not particularly limited as long as it contains 70 parts by mass or more of a monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B). Examples include conventionally known monofunctional (meth)acrylates (B1) or polyfunctional (meth)acrylates (B2) having a (meth)acryloyl group or a (meth)acryloyloxy group, which are used to form optical sheets. Oligomers or prepolymers may be used as needed. The (meth)acrylate compound (B) according to this embodiment preferably contains a monofunctional (meth)acrylate (B1) having one active energy ray-curable group (hereinafter simply referred to as "component (B1)") and a polyfunctional (meth)acrylate (B2) having two or more active energy ray-curable groups (hereinafter simply referred to as "component (B2)"). The active energy ray-curable group is preferably a (meth)acryloyl group. The (meth)acrylate compound (B) according to this embodiment does not include a dispersant (D) having a (meth)acryloyl group, or a silane coupling agent (E) having a (meth)acryloyl group or a (meth)acryloyloxy group. The components (B1) and (B2) will be described in detail below.

[0016] <Monofunctional (meth)acrylate (B1)> The monofunctional (meth)acrylate (B1) is a monofunctional (meth)acrylate having one active energy ray-curable group, and may be a chain aliphatic, cyclic alicyclic, or aromatic (meth)acrylate containing a heteroatom such as a halogen atom, a sulfur atom, an oxygen atom, or a nitrogen atom. For example, the monofunctional (meth)acrylates described in Patent Document 1 mentioned above can be used.

[0017] Examples of the monofunctional (meth)acrylate (B1) include aromatic mono(meth)acrylate compounds, aliphatic mono(meth)acrylate compounds, alicyclic mono(meth)acrylate compounds, heterocyclic mono(meth)acrylate compounds, and hydroxyl group-containing mono(meth)acrylate compounds. Examples of the monofunctional (meth)acrylate (B1) include polyoxyalkylene-modified mono(meth)acrylate compounds in which a polyoxyalkylene chain such as a polyoxyethylene chain, a polyoxypropylene chain, or a polyoxytetramethylene chain has been introduced into the molecular structure of the various mono(meth)acrylate compounds described above; and lactone-modified mono(meth)acrylate compounds in which a structure derived from a (poly)lactone has been introduced into the molecular structure of the various mono(meth)acrylate compounds described above.

[0018] Examples of the aromatic mono(meth)acrylate compound include benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, phenoxybenzyl (meth)acrylate, biphenylmethyl (meth)acrylate, benzylbenzyl (meth)acrylate, phenylphenoxyethyl (meth)acrylate, phenylphenol (EO)n (meth)acrylate, and phenol (EO)n (meth)acrylate.

[0019] Examples of the aliphatic mono(meth)acrylate compound include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, and 2-ethylhexyl(meth)acrylate. Examples of the alicyclic mono(meth)acrylate compound include cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, adamantyl mono(meth)acrylate, cyclohexylmethyl(meth)acrylate, cyclohexylethyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentanyloxyethyl(meth)acrylate, dicyclopentenyl(meth)acrylate, and dicyclopentenyloxyethyl(meth)acrylate. Examples of the heterocyclic mono(meth)acrylate compound include glycidyl (meth)acrylate and tetrahydrofurfuryl acrylate. Examples of the hydroxyl group-containing mono(meth)acrylate compound include hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, and hydroxybutyl(meth)acrylate. Examples of the lactone-modified mono(meth)acrylate compound include caprolactone-modified tetrahydrofurfuryl(meth)acrylate.

[0020] The monofunctional (meth)acrylate (B1) preferably contains an aromatic mono(meth)acrylate compound, more preferably a compound containing two aromatic rings in one molecule, and particularly preferably biphenylmethyl(meth)acrylate. Examples of the compound containing two aromatic rings in one molecule (aromatic mono(meth)acrylate compound) include phenoxybenzyl(meth)acrylate, biphenylmethyl(meth)acrylate, benzylbenzyl(meth)acrylate, phenylphenoxyethyl(meth)acrylate, phenylphenol(EO)n(meth)acrylate, and (1-naphthyl)methyl acrylate.

[0021] Specific examples of the monofunctional (meth)acrylate (B1) include the following monofunctional (meth)acrylates used in the examples. Compound (B1-1): orthophenylphenol (EO) acrylate, trade name: KOMERATE A011 (manufactured by Green Chemical Co., Ltd.) Compound (B1-2): Biphenylmethyl acrylate, trade name: MIRAMER M1192 (manufactured by MIWON SPECIALTY CHEMICAL CO., LTD.) Compound (B1-3): 3-phenoxybenzyl acrylate, trade name: KOMERATE A008 (manufactured by Green Chemical Co., Ltd.) Compound (B1-4): (1-naphthyl)methyl acrylate, trade name: Light Acrylate NMT-A (manufactured by Kyoei Chemical Co., Ltd.) Compound (B1-5): phenoxyethyl acrylate, trade name: Photomer 4035 (manufactured by IGM Resins Inc.) Compound (B1-6): benzyl acrylate, trade name: MIRAMER M1182 (manufactured by MIWON SPECIALTY CHEMICAL CO., LTD.)

[0022] The monofunctional (meth)acrylate (B1) may be used alone or in combination of two or more kinds. The content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) is 70% by mass, preferably 75% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more. It is also preferably 95% by mass or less, and more preferably 90% by mass or less. When the content of the monofunctional (meth)acrylate (B1) is within the above range, the mold releasability is good, and the composition has a high refractive index and a low viscosity.

[0023] When the monofunctional (meth)acrylate (B1) contains a compound containing two aromatic rings in one molecule (aromatic mono(meth)acrylate compound), the content of the compound containing two aromatic rings in one molecule in the monofunctional (meth)acrylate (B1) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. An example of the compound containing two aromatic rings in one molecule is biphenylmethyl(meth)acrylate. The content of the compound is not particularly limited, and a higher value is preferable. In terms of releasability, the content is preferably 95% by mass or less, and more preferably 90% by mass or less. Furthermore, when the compound containing two aromatic rings in one molecule in the monofunctional (meth)acrylate (B1) is biphenyl methyl acrylate, the composition is particularly excellent in terms of refractive index, viscosity, releasability, and substrate adhesion.

[0024] [Multifunctional (meth)acrylate (B2)] The (meth)acrylate compound (B) according to this embodiment preferably contains a polyfunctional (meth)acrylate (B2) (sometimes referred to as "component (B2)") in addition to the monofunctional (meth)acrylate (B1) according to this embodiment.

[0025] The polyfunctional (meth)acrylate (B2) is preferably a polyfunctional (meth)acrylate having three or more active energy ray-curable groups. It may be a chain aliphatic, cyclic alicyclic, or aromatic (meth)acrylate containing a heteroatom such as a halogen atom, a sulfur atom, an oxygen atom, or a nitrogen atom, and for example, the polyfunctional (meth)acrylate described in Patent Document 1 can be used.

[0026] Examples of the polyfunctional (meth)acrylate (B2) include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, tetrabutylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, Acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, glycerol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, caprolactone-modified hydroxypivalic acid neopentyl glycol di(meth)acrylate, tetrabromobisphenol A di(meth)acrylate, hydropivalaldehyde-modified trimethylolpropane di(meth)acrylate, bisphenol fluorene di(meth)acrylate, bisphenol fluorene (EO) n Di(meth)acrylate, bisphenol A (EO) n Di(meth)acrylate, trimethylolpropane (EO) n tri(meth)acrylate, 1,4-cyclohexanedimethanol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, glycerol tri(meth)acrylate, alkyl-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetra(meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, polyester (meth)acrylate, and other polyfunctional (meth)acrylates (B2).

[0027] These polyfunctional (meth)acrylates (B2) can be used alone or in combination of two or more. Among these, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, a reaction product of pentaerythritol and acrylic acid, a reaction product of dipentaerythritol and acrylic acid, and the like are preferred, since they can give (meth)acrylic resins excellent in drying properties, ink fluidity, and suitability for high-speed printing.

[0028] An example of the polyfunctional (meth)acrylate (B2) according to this embodiment is a mixture of a polyfunctional (meth)acrylate having three active energy ray-curable groups and a polyfunctional (meth)acrylate having four active energy ray-curable groups. Specific examples include a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (containing approximately 30 to 70% by mass of triacrylate and approximately 70 to 30% by mass of tetraacrylate). Examples of such mixtures include "Aronix M-305" (manufactured by Toagosei Co., Ltd., a reaction product of pentaerythritol and acrylic acid, containing approximately 60% triacrylate, and having a hydroxyl value of 116 mgKOH / g), which was used in the examples.

[0029] When the content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) is in the range of 70 to 90 mass%, the content of the polyfunctional (meth)acrylate (B2) in the (meth)acrylate compound (B) according to this embodiment is preferably in the range of 10 to 30 mass%, more preferably 10 to 25 mass%, and even more preferably 10 to 20 mass%. When it is in this range, the refractive index is excellent.

[0030] [Photopolymerization initiator (C)] The photopolymerization initiator (C) according to this embodiment is not particularly limited as long as it has the function of initiating polymerization of the (meth)acryloyl group of the (meth)acrylate compound (B) according to this embodiment or the like upon photoexcitation, and examples thereof include an intramolecular bond cleavage type photopolymerization initiator (C) and an intramolecular hydrogen abstraction type photopolymerization initiator (C). For example, monocarbonyl compounds, dicarbonyl compounds, acetophenone compounds, benzoin ether compounds, acylphosphine oxide compounds, aminocarbonyl compounds, etc. can be used.

[0031] Examples of the intramolecular bond cleavage type photopolymerization initiator (C) include acetophenone-based initiators such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoins such as benzoin methyl ether and benzoin isopropyl ether; acylphosphine oxide-based initiators such as 2,4,6-trimethylbenzoin diphenylphosphine oxide; and benzyl and methylphenyl glyoxyesters.

[0032] Examples of the intramolecular hydrogen abstraction type photopolymerization initiator (C) include benzophenone-based initiators such as benzophenone, o-benzoylmethylbenzoate-4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone-based initiators such as 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone; aminobenzophenone-based initiators such as Michler's ketone and 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone. The photopolymerization initiator (C) is preferably 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0033] Commercially available products of the photopolymerization initiator (C) include Omnirad-184, 651, 500, 907, 127, 369, 784, 2959, and TPO-H manufactured by IGM-Resins; and Esacure ONE manufactured by DKSH Japan Co., Ltd. Omnirad-907 and Omnirad-TPO-H are preferred because they provide excellent curing properties even when added in small amounts. Omnirad-184 is particularly preferred because it produces little coloring.

[0034] The photopolymerization initiator (C) is not limited to the above compounds, and any compound may be used as long as it has the ability to initiate polymerization by ultraviolet light. These photopolymerization initiators (C) may be used alone or in combination of two or more. The amount of the photopolymerization initiator (C) used is not particularly limited, but is preferably 0.1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the total nonvolatile content of the active energy ray-curable composition of the present embodiment. A known organic amine or the like may also be added as a sensitizer. Furthermore, in addition to the radical polymerization initiator, a cationic polymerization initiator can also be used in combination.

[0035] A specific example of the photopolymerization initiator (C) according to this embodiment is Runtecure 1108 (manufactured by Runtec Chemical Co., Ltd., structural formula or compound name: 2,4,6-trimethylbenzoyldiphenylphosphine oxide).

[0036] The content of the photopolymerization initiator (C) is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the mass of the nonvolatile content of the composition. The nonvolatile mass of a composition is the total mass of all components of the composition excluding the solvent contained in the composition.

[0037] [Dispersant (D)] The active energy ray-curable composition of the present embodiment preferably further contains a dispersant (D) (sometimes referred to as "component (D)"), and it is more preferable that the dispersant (D) contains a phosphate ester.

[0038] <Phosphate ester> The phosphate ester according to this embodiment is not particularly limited, but examples thereof include those having a polyester chain and those having a (meth)acryloyl group. Examples of those having a polyester chain include DISPERBYK-110 and DISPERBYK-111 (manufactured by BYK Japan KK).

[0039] Furthermore, examples of those having a (meth)acryloyl group include those represented by the following structural formula (1): In this case, the resulting inorganic fine particle dispersion has excellent dispersion stability, and the curable composition containing it has low viscosity and can form a cured coating film having high refractive index performance and excellent bleed-out resistance, which is preferable.

[0040] [ka] (R in the formula 1 is a hydrogen atom or a methyl group, and R 2 is an alkylene chain having 2 to 4 carbon atoms. In addition, x is an integer of 4 to 10, y is an integer of 1 or more, and n is an integer of 1 to 3.

[0041] In the phosphate ester compound represented by the structural formula (1), x is preferably 4 or 5, and y is preferably an integer of 2 to 7. This is because the resulting active energy ray-curable composition has low viscosity and can form a cured coating film having high refractive index performance and excellent bleed-out resistance. Furthermore, the dispersant (D) represented by the structural formula (1) may be a mixture in which n is 1, 2, and / or 3.

[0042] The content of the phosphate ester compound in the active energy ray-curable composition is more preferably in the range of 5 to 40 parts by mass, and even more preferably in the range of 10 to 25 parts by mass, per 100 parts by mass of zirconia, because a cured coating film having high refractive index performance and excellent bleed-out resistance can be formed.

[0043] [Silane coupling agent (E)] The active energy ray-curable composition of this embodiment may further contain a silane coupling agent (E) (sometimes referred to as "component (E)"). Examples of the silane coupling agent (E) according to this embodiment include (meth)acryloyloxy-based silane coupling agents such as 3-(meth)acryloyloxypropyltrimethylsilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, and 3-(meth)acryloyloxypropyltriethoxysilane; vinyl-based silane coupling agents such as allyltrichlorosilane, allyltriethoxysilane, allyltrimethoxysilane, diethoxymethylvinylsilane, trichlorovinylsilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris(2-methoxyethoxy)silane; Epoxy-based silane coupling agents such as diethoxy(glycidyloxypropyl)methylsilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styrene-based silane coupling agents such as p-styryltrimethoxysilane; amino-based silane coupling agents such as N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; ureido-based silane coupling agents such as 3-ureidopropyltriethoxysilane; Chloropropyl-based silane coupling agents such as 3-chloropropyltrimethoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; Sulfide-based silane coupling agents such as bis(triethoxysilylpropyl)tetrasulfide; Isocyanate-based silane coupling agents such as 3-isocyanatepropyltriethoxysilane; Examples include aluminum-based silane coupling agents such as acetoalkoxyaluminum diisopropylate. These silane coupling agents (E) can be used alone or in combination of two or more. Among these, 3-(meth)acryloyloxypropyltrimethoxysilane is preferred because of its good compatibility with the acrylate compound (B). The amount of the silane coupling agent (E) used in this embodiment is preferably in the range of 10 to 30 parts by mass per 100 parts by mass of zirconia, because the resulting active energy ray-curable composition has excellent dispersion stability and is low in viscosity, and a cured coating film having high refractive index performance and excellent bleed-out resistance can be formed.

[0044] [solvent] The active energy ray-curable composition of the present embodiment may contain a solvent. The solvent is not particularly limited, and various known organic solvents can be used.Specific examples include cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, acetone, acetylacetone, toluene, xylene, n-butanol, isobutanol, tert-butanol, n-propanol, isopropanol, ethanol, methanol, 3-methoxy-1-butanol, 3-methoxy-2-butanol, ethylene glycol monomethyl ether, ethylene glycol mono-n-butyl ether, 2-ethoxyethanol, 1-methoxy-2-propanol, diacetone alcohol, ethyl lactate, butyl lactate, propylene glycol monomethyl ether, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, 2-ethoxyethyl acetate, butyl acetate, isoamyl acetate, dimethyl adipate, dimethyl succinate, dimethyl glutarate, tetrahydrofuran, and methylpyrrolidone.Among these, methyl ethyl ketone is preferred. Two or more of these organic solvents may be used in combination. The active energy ray-curable composition of the present embodiment may contain, for example, a solvent used in synthesizing each resin. Furthermore, the active energy ray-curable composition of the present embodiment may be prepared by mixing the inorganic nanoparticles (A), a solvent, and any optional components to prepare an inorganic nanoparticle (A) dispersion, and then mixing the inorganic nanoparticles (A) with the (meth)acrylate compound (B) and the photopolymerization initiator (C). The above-mentioned example of containing a solvent is just one example, and even if a solvent is contained in the process of preparing the active energy ray-curable composition of the present embodiment, it is preferable that the solvent is finally volatilized and the content of the solvent is as small as possible. Therefore, when the active energy ray-curable composition of the present embodiment contains a solvent, the content of the solvent in the active energy ray-curable composition is preferably 0 to 5 mass %, more preferably 0 to 0.1 mass %.

[0045] [Viscosity of active energy ray-curable composition] The viscosity of the active energy ray-curable composition of this embodiment at 25°C is preferably 6500 Pa·s or less, more preferably 3500 mPa·s or less, and even more preferably 1500 mPa·s or less. Furthermore, the viscosity is preferably 1000 mPa·s or more. Within this range, the composition is suitable for coating.

[0046] [Method for preparing active energy ray-curable composition] The method for preparing the active energy ray-curable composition of the present embodiment is not particularly limited. For example, a method may be mentioned in which a dispersion of inorganic nanoparticles (A) is obtained, and then the dispersion of inorganic nanoparticles (A), the monofunctional (meth)acrylate (B1), the photoinitiator, and, if necessary, the polyfunctional (meth)acrylate (B2) and various other additives are mixed to produce the active energy ray-curable composition. The method for producing the active energy ray-curable composition of the present embodiment preferably includes the steps of: preparing a dispersion of inorganic nanoparticles (A); and mixing the dispersion of inorganic nanoparticles (A), the monofunctional (meth)acrylate (B1), a photoinitiator, and, if necessary, a polyfunctional (meth)acrylate (B2), and various other additives. The mixing method is not particularly limited, but for example, a method using a media-type wet disperser can be mentioned.

[0047] In addition, in the step of preparing the inorganic nanoparticle (A) dispersion, at least a portion of the monofunctional (meth)acrylate (B1) and, if necessary, at least a portion of the polyfunctional (meth)acrylate (B2) may be added.

[0048] <Inorganic nanoparticle (A) dispersion> The inorganic nanoparticle (A) dispersion according to this embodiment preferably contains, for example, the inorganic nanoparticles (A), the solvent, and the dispersant (D) as the additive. The inorganic nanoparticle (A) dispersion according to this embodiment may further contain at least a portion of the monofunctional (meth)acrylate (B1), or, if necessary, at least a portion of the polyfunctional (meth)acrylate (B2). The dispersant (D) preferably has an acid value in the range of 50 to 300 mgKOH / g. Generally, the dispersant (D) is prone to aggregation of inorganic nanoparticles in the system due to interactions between the inorganic nanoparticles (A) and other resin components contained in the active energy ray-curable composition of this embodiment, resulting in a decrease in the storage stability of the active energy ray-curable composition and a decrease in the transparency of the cured coating film. By using a dispersant (D) with an acid value in the range of 50 to 300 mgKOH / g, a curable composition with excellent stability over time can be obtained, and the cured product will not only have a high refractive index, but also excellent light transmittance and scratch resistance. The inorganic nanoparticle (A) dispersion according to this embodiment preferably further contains the silane coupling agent (E) as the additive. Functional groups can be introduced onto the surfaces of the inorganic nanoparticles (A) using the various silane coupling agents (E) described above.

[0049] The method for producing the inorganic nanoparticle (A) dispersion according to this embodiment is not particularly limited, and examples thereof include a method for producing the dispersion by dispersing raw materials containing the inorganic nanoparticles (A), the dispersant (D), and, if necessary, the silane coupling agent (E) in a media-type wet disperser.

[0050] The media-type wet disperser used in the production method can be any known one without any restrictions, and examples thereof include bead mills (Star Mill LMZ-015 manufactured by Ashizawa Finetech Co., Ltd., Ultra Apex Mill UAM-015 manufactured by Kotobuki Industries Co., Ltd., etc.).

[0051] The media used in the disperser are not particularly limited as long as they are commonly known beads, but preferred examples include zirconia, alumina, silica, glass, silicon carbide, and silicon nitride. The average particle size of the media is preferably 50 to 500 μm, and more preferably 50 to 200 μm. If the particle size is 50 μm or more, the impact force on the raw material powder is appropriate, and dispersion does not require an excessive amount of time. On the other hand, if the particle size of the media is 500 μm or less, the impact force on the raw material powder is appropriate, which can suppress an increase in the surface energy of the dispersed particles and prevent re-agglomeration.

[0052] The dispersion process time can also be shortened by using a two-stage method in which large-particle size media with a large impact force are used in the initial stage of grinding the raw material powder, and then small-particle size media that are less likely to re-agglomerate are used after the particle size of the dispersed particles has become smaller.

[0053] Furthermore, it is desirable to use media that has been sufficiently polished in order to prevent a decrease in the light transmittance of the resulting dispersion.

[0054] In the production method using the media-type wet disperser, the order in which the raw materials are charged into the disperser is not particularly limited, but by supplying at least the dispersant (D) last, a curable composition with excellent dispersion stability can be obtained using a small amount of dispersant (D). More specifically, a method in which the raw materials other than the dispersant (D) are charged first, and then mixing or pre-dispersion is performed, and then the dispersant (D) is charged last and the main dispersion step is performed can be mentioned.

[0055] After dispersion is complete, various additives may be added depending on the intended use, or volatile components may be removed by distillation, thereby obtaining the curable composition of the present invention.

[0056] Furthermore, the particle diameter (referred to as the average particle diameter) of the inorganic nanoparticles (A) in the inorganic nanoparticle (A) dispersion is larger than the average primary particle diameter of the inorganic nanoparticles (A) that are the raw material for the inorganic nanoparticle (A) dispersion, since the inorganic nanoparticles (A) are partially aggregated in the dispersion. Therefore, the average particle size of the inorganic nanoparticles (A) in the inorganic nanoparticle (A) dispersion is preferably 100 nm or less, and more preferably in the range of 20 to 100 nm, since this results in a cured product with a high refractive index and excellent light transmittance.

[0057] [Characteristics of active energy ray-curable composition] The active energy ray-curable composition of this embodiment has good releasability, a high refractive index, and a low viscosity. Examples of the active energy ray-curable composition of this embodiment include LUXYDIR (registered trademark) (manufactured by DIC Corporation).

[0058] (cured product) The cured product of this embodiment is a cured product of the active energy ray-curable composition of this embodiment described above. The cured product of this embodiment can be used for various applications, such as optical lenses, optical films, antireflection materials, thin film encapsulating materials, optical pressure-sensitive adhesives, optical adhesives, and diffusion microlenses. The shape of the cured product of the present embodiment is not particularly limited, and can be selected depending on the application, such as a flat sheet having a smooth surface, a sheet having a fine uneven structure, or a sheet having a curved surface like a concave or convex lens. The cured product of this embodiment preferably has a refractive index (589 nm) at 25°C of 1.62 or more, more preferably 1.65 or more, and even more preferably 1.66 or more. This is because, when used in optical lenses, it allows for thinner films; in optical films, the difference in refractive index between the transparent electrode and the cured product is reduced to make the transparent electrode less noticeable; when combined with a low refractive index layer, it provides anti-reflection functionality; and in LED encapsulants, it improves the light extraction efficiency from the light-emitting element. Furthermore, the upper limit of the refractive index is not particularly limited, and a higher value is preferable. In terms of balance with viscosity, the refractive index is preferably 1.62 to 1.70, and more preferably 1.65 to 1.69.

[0059] [Method of manufacturing the cured product] The method for producing the cured product of the present embodiment is not particularly limited, and includes, for example, a coating step of coating the active energy ray-curable composition of the present embodiment onto a substrate such as a transparent film; and a curing step of irradiating the film of the active energy ray-curable composition obtained in the coating step with active energy rays to cure it. As a method for applying the composition to a substrate such as a transparent film, a known method can be used. For example, a method using a rod or a wire bar, or various coating methods such as microgravure, gravure, die, curtain, lip, slot, or spin coating can be used.

[0060] The active energy rays can be used without any particular limitation as long as they are active energy rays that cause curing of the curable composition of the present invention, but it is particularly preferable to use ultraviolet rays.

[0061] Sources of ultraviolet rays include fluorescent chemical lamps, black lights, low-pressure, high-pressure, and ultra-high-pressure mercury lamps, metal halide lamps, sunlight, etc. For example, an 80W high-pressure mercury lamp can be used. The irradiation intensity of ultraviolet light may be constant throughout the curing process, or the intensity may be changed during the curing process to finely adjust the physical properties after curing. For example, when using an 80 W high-pressure mercury lamp in a nitrogen atmosphere, ultraviolet light is irradiated at an intensity of 0.5 to 3.0 kJ / m 2 It can be irradiated with an energy value of

[0062] In addition to ultraviolet rays, other active energy rays that can be used include visible light and electron beams.

[0063] (optical sheet) The optical sheet of this embodiment can be formed using the cured product of this embodiment described above. The optical sheet of this embodiment may include, for example, a substrate and the cured product according to this embodiment formed on the substrate. The optical sheet of this embodiment may include, for example, a fine pattern layer having a fine uneven structure or the like that is a cured product of the active energy ray-curable composition of this embodiment, and a transparent substrate. The fine pattern layer having a fine uneven structure or the like may have a fine uneven structure of, for example, 10 to 500 μm on its surface depending on the application of the optical sheet. Furthermore, the cured product of the active energy ray-curable composition in the optical sheet of this embodiment may have a smooth surface without having a fine uneven structure. The shape can be selected appropriately depending on various applications. Examples of the optical sheet include a polarizing film, a retardation film, an anti-reflection film, a brightness enhancing film (such as a prism sheet or a microlens sheet), a light diffusing film, and a hard coat film.

[0064] [Base material] Examples of the substrate in this embodiment include polyethylene terephthalate (PET), triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polycarbonate, vinyl chloride, polymethacrylimide, polyimide, polyester, acrylic substrates mainly composed of polymethyl methacrylate (PMMA), glass, and silicon wafers. The thickness of the substrate according to this embodiment is preferably 1 to 300 μm, and more preferably 5 to 100 μm. A specific example of the substrate according to this embodiment is a 125 μm polyethylene terephthalate (PET) substrate (product name: A4300, manufactured by Toyobo Co., Ltd.) used in the examples.

[0065] When the substrate is transparent, a transparent substrate used in a conventionally known optical sheet such as a prism sheet can be used. For example, the transparent substrate described in Patent Document 2 can be used. The transparent substrate may be a resin substrate or a glass substrate. Examples of preferred transparent resin substrates include acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylimide resin, polyimide resin, polyester resin, cycloolefin polymer (COP) resin, cycloolefin copolymer (COC) resin, and cellulose triacetate (TAC) resin.

[0066] The transparent substrate may be in a long shape or in a sheet shape of a predetermined size. The thickness of the transparent substrate is usually preferably 50 to 500 μm, but is not limited to this. The light transmittance of the transparent substrate is ideally 100% for installation in front of a display, and preferably 85% or more. The transparent substrate may have its surface subjected to a conventionally known matte treatment (formation of light-diffusing micro-irregularities), antistatic treatment, antireflection treatment, etc. Furthermore, the transparent resin and the substrate may be interposed between them and the substrate, or these may be used in any combination.

[0067] [Optical sheet manufacturing method] The method for producing the optical sheet of this embodiment is not particularly limited, and includes, for example, a step of applying the active energy ray-curable composition of this embodiment to the substrate, and a step of irradiating the substrate with active energy rays such as ultraviolet rays to form a cured coating film. A method for producing the laminate of this embodiment includes, for example, a step of applying the active energy ray-curable composition of this embodiment to a triacetyl cellulose substrate film (TAC substrate film) having a thickness of 40 to 100 μm, and a step of irradiating the substrate with ultraviolet rays at 0.5 to 3.0 kJ / m using a 60 to 100 W high-pressure mercury lamp under a nitrogen atmosphere. 2 and forming a cured coating film having a thickness of 5 to 20 μm on the TAC substrate film.

[0068] As shown in Figure 2 of Patent Document (JP 2009-37204 A), for example, a method for producing the optical sheet of this embodiment involves placing the composition in a mold having a fine pattern such as a desired fine concavo-convex structure, overlaying a transparent substrate layer thereon, pressing the transparent substrate layer onto the composition using a laminator or the like, and curing the composition with ultraviolet light or the like to form a fine pattern such as a fine concavo-convex structure. Next, the fine pattern mold is peeled or removed, thereby obtaining an optical sheet having optical function-exhibiting portions having the desired fine pattern on the transparent substrate layer.

[0069] <Prism sheet> A specific example of the optical sheet of this embodiment is a prism sheet. The prism sheet has, for example, a microrelief structure layer that is a cured product of the active energy ray-curable composition of this embodiment, and a transparent substrate. The microrelief structure layer has a microrelief structure with a period P of 10 to 100 μm on its surface. The thickness of the microrelief structure layer is, for example, 5 μm to 100 μm.

[0070] Typically, when the content of monofunctional (meth)acrylate (B1) in a composition is high, the polymer structure after curing has less branching, which tends to result in poor mold releasability of the cured product. Focusing on this tendency, the present invention has been able to improve mold releasability by setting the mass ratio [(A) / (B1)] of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) to be in the range of 0.5 to 3. More specifically, when [(A) / (B1)] is in the range of 0.5 to 3, the inorganic nanoparticles (A) are more likely to be present on the surface (i.e., near the interface between the composition and the mold) when the composition is applied to a substrate, which is thought to reduce adhesion of the cured product of the composition to the mold. Furthermore, the inclusion of a silane coupling agent and a phosphate ester-based dispersant containing a (meth)acryloyl group in the composition further improved the mold releasability of the cured product. This is thought to be because the inorganic nanoparticles (A) become compatible with the components other than (A) in the composition via the silane coupling agent and the phosphate ester-based dispersant, increasing the strength of the cured product and making it less likely to remain on the mold when the cured product is peeled from the mold. Furthermore, in the present invention, substrate adhesion was particularly improved when orthophenylphenol (EO) acrylate, biphenyl methyl acrylate, or (1-naphthyl)methyl acrylate was used as the monofunctional (meth)acrylate (B1). These compounds are monomers with relatively high glass transition temperatures, and are thought to also improve the coating hardness of the composition. This improvement in hardness and several other factors may have combined to improve substrate adhesion. In addition, when phenoxyethyl acrylate was used as the monofunctional (meth)acrylate (B1), the adhesion to the substrate was also good. This is thought to be because phenoxyethyl acrylate contains a highly polar ethylene oxide structure in the molecule, which enhances the interaction with the substrate. As described above, configurations that provide greater effects and mechanisms that are thought to produce these effects have been explained, but the present invention is not limited to these configurations, and the problems of the present invention can also be solved with a composition that does not contain a silane coupling agent and a phosphate ester-based dispersant, or a composition that does not contain a specific compound as the monofunctional (meth)acrylate (B1). [Example]

[0071] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. (raw materials) "Zirconia (A)": UEP-100 (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) "Dispersant (D)" (phosphate ester compound): Dispersant D-1 (a compound represented by the following structural formula (1)

[0072] [ka]

[0073] (In the formula, R 1 is a methyl group, and R 2 is an ethylene chain having 2 carbon atoms, x is 5, y is 2 (average value), and n is an integer of 1 to 3.

[0074] "Silane coupling agent (E)": KBM-503 (Shin-Etsu Chemical Co., Ltd., 3-(trimethoxysilyl)propyl methacrylate)

[0075] "Monofunctional (meth)acrylate compound (B1)": Orthophenylphenol (EO) acrylate, product name: KOMERATE A011 (manufactured by Green Chemical Co., Ltd.) Biphenyl methyl acrylate, trade name: MIRAMER M1192 (manufactured by MIWON SPECIALTY CHEMICAL CO., LTD.) 3-Phenoxybenzyl acrylate, product name: KOMERATE A008 (manufactured by Green Chemical Co., Ltd.) (1-Naphthyl)methyl acrylate, product name: Light Acrylate NMT-A (manufactured by Kyoei Chemical Co., Ltd.) Phenoxyethyl acrylate, product name: Photomer 4035 (manufactured by IGM Resins Inc.) Benzyl acrylate, trade name: MIRAMER M1182 (manufactured by MIWON SPECIALTY CHEMICAL CO., LTD.)

[0076] "Multifunctional (meth)acrylate compound (B2)" A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (containing approximately 60% triacrylate), trade name: Aronix M305 (manufactured by Toagosei Co., Ltd.)

[0077] "Photopolymerization initiator (C)": 2,4,6-trimethylbenzoyldiphenylphosphine oxide, trade name: Runtecure 1108 (manufactured by Runtec Chemical Co., Ltd.)

[0078] <Liquid refractive index> The active energy ray-curable composition was directly applied to the prism of the Abbe refractometer, and measurement was carried out at 25° C. Measurement wavelength: 589 nm.

[0079] <Film refractive index> The active energy ray-curable composition was sandwiched between a glass plate and a transparent, easy-adhesion treated PET film (product name: A4300, thickness: 125 μm, manufactured by Toyobo Co., Ltd.) as a transparent substrate, and spread to a film thickness of approximately 10 μm using a rubber hand roller. It was then cured by irradiation with active energy rays. The PET film was then peeled off from the glass plate together with the active energy ray-curable resin layer, forming a cured coating film of the curable composition on the surface of the substrate. The refractive index of the coating film was measured using a PRISM COUPLER MODEL 2010 / M (manufactured by Metricon). "Irradiation conditions" Light source: Ultraviolet light from an ultra-high pressure mercury lamp Accumulated light output: 400mJ / cm 2 "Measurement conditions" Wavelength: 594nm Measurement mode: single film

[0080] <Viscosity> The viscosity was evaluated by measuring the viscosity at a temperature of 25°C using an E-type rotational viscometer ("TVE-25H" manufactured by Toki Sangyo Co., Ltd.).

[0081] <Mold releasability> The active energy ray-curable composition was filled between a phosphorus nickel mold and a PET film (product name: A4300, thickness: 125 μm, manufactured by Toyobo Co., Ltd.), and then exposed to 400 mJ / cm 2 of an ultra-high pressure mercury lamp. 2The film was cured by irradiating it with ultraviolet light from the PET film side. The phosphorus nickel mold had a concave-convex shape formed with a linear array of unit prisms (pitch 50 μm, height 25 μm). The PET film was a transparent substrate that had been treated for easy adhesion. Next, the PET film was peeled off from the mold together with the resin layer made of the active energy ray-curable composition, and a cured product with a PET film shape transferred with the required shape was produced. The area of ​​the resin layer remaining on the mold upon peeling was evaluated visually and judged as follows: ◎: No resin layer remains on the mold ○: Part of the resin layer remains on the mold ×: The entire surface remains on the mold

[0082] <Adhesion to substrate> The adhesiveness of the cured PET film obtained in the same manner as in the above-mentioned <releasability> evaluation method was evaluated by the cross-cut adhesion test. Using a cutter knife and a cutter guide, 11 cuts were made at 1 mm intervals on the test surface, reaching down to the base material, creating 100 grids. Next, Scotch tape (registered trademark) was firmly pressed onto the grids, and the edge of the tape was quickly peeled off. The number of grids that remained intact in the resin layer was counted and evaluated.

[0083] Example 1 As zirconia, UEP-100, 45.00 parts by mass, As a phosphate ester, 6.75 parts by mass of phosphate ester 1 (dispersant D-1), As a silane coupling agent (1), 4.50 parts by mass of KBM-503; 96.8 parts by mass of methyl ethyl ketone (hereinafter abbreviated as "MEK") The mixture was mixed and stirred for 30 minutes using a dispersion stirrer to perform coarse dispersion. The resulting mixture was then dispersed using zirconia beads with a particle size of 100 μm in a media-type wet disperser (Ashizawa Finetech Co., Ltd.'s "Star Mill LMZ-015"). The dispersion was continued for 100 minutes while checking the particle size during the process, to obtain an inorganic fine particle dispersion. In this inorganic fine particle dispersion, 37.25 parts by mass of compound (B1-2): MIRAMER M1192 (manufactured by MIWON SPECIALTY CHEMICAL CO., LTD.) as a monofunctional (meth)acrylate (B1) and 5.00 parts by mass of compound (B2-1): ARONIX M305 (manufactured by TOAGOSEI CO., LTD.) as a polyfunctional (meth)acrylate compound (B2) were added, and the volatile components were removed under reduced pressure while heating in an evaporator. 0.7 parts by mass of Runtecure 1108 (manufactured by Runtec Chemical Co., Ltd.) as a photopolymerization initiator; An active energy ray-curable composition P1 (composition P1) of this embodiment was prepared by adding the above. The liquid refractive index and viscosity of composition P1 were evaluated using the evaluation methods described above. In addition, the film refractive index, mold releasability, and substrate adhesion of a cured product of composition P1 were evaluated. The results are shown in Table 1.

[0084] (Examples 2 to 14, Comparative Examples 1 to 6) Compositions P2 to P14 and cP1 to cP6 of Examples 2 to 14 and Comparative Examples 1 to 6 were prepared in the same manner as Example 1, except that the components and compositional ratios shown in Table 1 were used. As in Example 1, the amount of MEK used was 2.15 times the amount of inorganic nanoparticles listed in Table 1. As in Example 1, the liquid refractive index, film refractive index, and viscosity of each composition were evaluated. Furthermore, the mold releasability and substrate adhesion of the cured product of each composition were evaluated. The results are shown in Table 1.

[0085] [Table 1]

[0086] In the table, the meaning of each item is as follows: The compositions of Comparative Examples 1 to 6 had poor releasability and could not be used to prepare prism sheets, so that the adhesion test could not be carried out (measurement not possible). [(A) / (B1)]: mass ratio of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) [(B1) / (B)]: content of monofunctional (meth)acrylate (B1) in (meth)acrylate compound (B) (unit: mass%) [Compound containing a compound having two aromatic rings in one molecule / (B)]: Content of a compound containing a compound having two aromatic rings in one molecule in the (meth)acrylate compound (B) (unit: mass%) Inorganic nanoparticles (A) (1): Zirconia, product name: UEP-100 (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) Phosphate ester compound (1): Dispersant D-1, a compound represented by the above structural formula (1) Silane coupling agent (E) (1): 3-(trimethoxysilyl)propyl methacrylate, trade name: KBM-503 (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0087] Compound (B1-1): orthophenylphenol (EO) acrylate, trade name: KOMERATE A011 (manufactured by Green Chemical Co., Ltd.) Compound (B1-2): biphenyl methyl acrylate, trade name: MIRAMER M1192 (manufactured by MIWON SPECIALTY CHEMICAL CO., LTD.) Compound (B1-3): 3-phenoxybenzyl acrylate, trade name: KOMERATE A008 (manufactured by Green Chemical Co., Ltd.) Compound (B1-4): (1-naphthyl)methyl acrylate, trade name: Light Acrylate NMT-A (manufactured by Kyoei Chemical Co., Ltd.) Compound (B1-5): phenoxyethyl acrylate, trade name: Photomer 4035 (manufactured by IGM Resins Inc.) Compound (B1-6): benzyl acrylate, trade name: MIRAMER M1182 (manufactured by MIWON SPECIALTY CHEMICAL CO., LTD.) Compound (B2-1): a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (containing approximately 60% of the triacrylate), trade name: Aronix M305 (manufactured by Toagosei Co., Ltd.)

[0088] Photopolymerization initiator (C): 2,4,6-trimethylbenzoyldiphenylphosphine oxide, trade name: Runtecure 1108 (manufactured by Runtec Chemical Co., Ltd.)

[0089] (Consideration) As shown in Table 1, in Examples 1 to 14, in which the content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) was 70 mass % or more and the mass blending ratio of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) [(A) / (B1)] was in the range of 0.5 to 3, it was confirmed that the composition had a high refractive index and low viscosity, and the cured product had good releasability and a high film refractive index. Among these, it was confirmed that Examples 1 to 9 and 12 to 14, which used at least one of compound (B1-1) (orthophenylphenol (EO) acrylate), compound (B1-2) (biphenyl methyl acrylate), compound (B1-4) ((1-naphthyl)methyl acrylate), compound (B1-5) (phenoxyethyl acrylate), and compound (B2-1) (pentaerythritol triacrylate (containing pentaerythritol tetraacrylate)) as the (meth)acrylate compound (B), had better substrate adhesion. Furthermore, Examples 11 to 13, in which a compound containing two aromatic rings in one molecule was used as the monofunctional (meth)acrylate (B1), had a refractive index higher than Examples 9 and 10, in which a compound not containing two aromatic rings in one molecule was used as the monofunctional (meth)acrylate (B1).On the other hand, in Comparative Examples 1 to 5, in which the mass blending ratio [(A) / (B1)] of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) was less than 0.5, the release properties of the cured product were poor, and therefore a prism sheet could not be produced. In Comparative Example 6, which did not contain inorganic nanoparticles (A), the refractive index was significantly poor and good releasability was not obtained.

Claims

1. An active energy ray-curable composition containing inorganic nanoparticles (A), a (meth)acrylate compound (B), and a photopolymerization initiator (C), the (meth)acrylate compound (B) contains a monofunctional (meth)acrylate (B1), the content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) is 70 mass% or more, the mass blending ratio [(A) / (B1)] of the monofunctional (meth)acrylate (B1) to the inorganic nanoparticles (A) is in the range of 1 to 3; the content of the inorganic nanoparticles (A) in the active energy ray-curable composition is 30% by mass or more, Further containing a dispersant (D), The dispersant (D) is represented by the following structural formula (1): An active energy ray-curable composition having a viscosity at 25°C of 1200 mPa·s or less. 【Chemical 1】 (In the formula R １ is a hydrogen atom or a methyl group, and R ２ is an alkylene chain having 2 to 4 carbon atoms, x is an integer of 4 to 10, y is an integer of 1 or more, and n is an integer of 1 to 3.

2. The active energy ray-curable composition according to claim 1 , wherein the inorganic nanoparticles (A) are zirconia.

3. The (meth)acrylate compound (B) further contains a polyfunctional (meth)acrylate (B2), the content of the monofunctional (meth)acrylate (B1) in the (meth)acrylate compound (B) is in the range of 70 to 90 mass %, 3. The active energy ray-curable composition according to claim 1, wherein the content of the polyfunctional (meth)acrylate (B2) in the (meth)acrylate compound (B) is in the range of 10 to 30 mass%.

4. The active energy ray-curable composition according to claim 1 or 2, wherein the monofunctional (meth)acrylate (B1) contains a compound containing two aromatic rings in one molecule.

5. The active energy ray-curable composition according to claim 5 , wherein the content of the compound containing two aromatic rings in one molecule in the monofunctional (meth)acrylate (B1) is 50% by mass or more.

6. A cured product of the active energy ray-curable composition according to claim 1 or 2.

7. The cured product according to claim 6, which has a refractive index (589 nm) at 25°C of 1.66 or more.

8. An optical sheet comprising the cured product according to claim 6 .

9. An optical sheet comprising the cured product according to claim 7 .

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