Curable composition for forming low refractive index film, low refractive index film, optical device, and method for producing low refractive index film

Abstract

To provide a curable composition for forming a low refractive index film, which enables the formation of a cured film with excellent heat resistance.SOLUTION: A curable composition for forming a low refractive index film comprises a hollow filler (A), a polymerizable compound (B), and a polymerization initiator (C), and is free of alkali-soluble resins. The polymerizable compound (B) includes a compound (B1) having 5 or more polymerizable functional groups and a compound (B2) having 1 or more and 3 or less polymerizable functional groups. The ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 0.25 or more and 3 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a curable composition for forming a low refractive index film, a low refractive index film, an optical device, and a method for producing a low refractive index film. [Background technology]

[0002] Low refractive index films are used in optical components as optically functional films, including anti-reflection films, reflective films, semi-transmissive semi-reflective films, visible light reflective and infrared transmitting films, infrared reflective and visible light transmitting films, blue reflective films, green reflective films, red reflective films, emission line cut filters, and color tone correction films (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-271444 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the manufacturing process of optical components, heat treatment processes such as solder reflow and post-baking may be performed, so low refractive index films are also required to have heat resistance, but this point has not been fully considered.

[0005] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a curable composition for forming a low refractive index film capable of forming a cured film having excellent heat resistance, a low refractive index film made of a cured product of the curable composition, an optical device including the low refractive index film, and a method for producing a low refractive index film using the curable composition. [Means for solving the problem]

[0006] In order to solve the above problems, the present inventors conducted extensive research and found that, in a curable composition containing a hollow filler (A), a polymerizable compound (B), and a polymerization initiator (C) but not containing an alkali-soluble resin, the above problems can be solved if the ratio (B1 / B2) of the mass of the compound (B1) having 5 or more polymerizable functional groups to the mass of the compound (B2) having 1 to 3 polymerizable functional groups is 0.25 to 3, and thus the present invention was completed. Specifically, the present invention provides the following.

[0007] [1] A composition comprising a hollow filler (A), a polymerizable compound (B), and a polymerization initiator (C), and does not contain an alkali-soluble resin; the polymerizable compound (B) includes a compound (B1) having 5 or more polymerizable functional groups and a compound (B2) having 1 or more and 3 or less polymerizable functional groups; The curable composition for forming a low refractive index film, wherein the ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 0.25 or more and 3 or less.

[0008] [2] The compound (B1) is a compound having 5 or 6 polymerizable functional groups, The curable composition for forming a low refractive index film according to [1], wherein the compound (B2) is a compound having three polymerizable functional groups.

[0009] [3] The curable composition for forming a low refractive index film according to [1] or [2], wherein the ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 1.25 or more and 2 or less.

[0010] [4] The curable composition for forming a low refractive index film according to any one of [1] to [3], further comprising a surfactant (D).

[0011] [5] The curable composition for forming a low refractive index film according to [4], wherein the surfactant (D) contains a fluorine-based surfactant and / or a silicon-based surfactant.

[0012] [6] The curable composition for forming a low refractive index film according to any one of [1] to [5], wherein the hollow filler (A) contains hollow silica.

[0013] [7] A low refractive index film comprising a cured product of the curable composition for forming a low refractive index film according to any one of [1] to [6].

[0014] [8] An optical device comprising the low refractive index film according to [7].

[0015] [9] A step of forming a coating film of the curable composition for forming a low refractive index film according to any one of [1] to [6]; and curing the coating film.

[0016]

[10] The method for producing a low refractive index film according to [9], wherein the coating film is formed by a spin coating method, a spray coating method, a slit coating method, a bar coating method, or a dip coating method.

[0017]

[11] The method for producing a low refractive index film according to [9] or

[10] , wherein the coating film is cured by exposure to light. Effect of the Invention

[0018] According to the present invention, it is possible to provide a curable composition for forming a low refractive index film capable of forming a cured film having excellent heat resistance, a low refractive index film made of a cured product of the curable composition, an optical device including the low refractive index film, and a method for producing a low refractive index film using the curable composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The following describes in detail the embodiments of the present invention. However, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, in this specification, "to" indicates from greater than or equal to (lower limit) to less than or equal to (upper limit), unless otherwise specified. In this specification, when the term "curable composition" is used, it means a "curable composition for forming a low refractive index film" unless otherwise specified. In this specification, "(meth)acrylate" includes both acrylate and methacrylate. In this specification, "(meth)acrylic" includes both acrylic and methacrylic. In this specification, "(meth)acryloyl" includes both acryloyl and methacryloyl.

[0020] ≪Curable composition for forming low refractive index film≫ The curable composition for forming a low refractive index film contains a hollow filler (A), a polymerizable compound (B), and a polymerization initiator (C), and does not contain an alkali-soluble resin. The polymerizable compound (B) contains a compound (B1) having 5 or more polymerizable functional groups and a compound (B2) having 1 to 3 polymerizable functional groups. The ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 0.25 to 3. By using such a curable composition, a cured film having excellent heat resistance can be formed.

[0021] <Hollow filler (A)> The curable composition contains a hollow filler (A) in order to form a low refractive index film exhibiting a desired low refractive index. The hollow filler (A) is appropriately selected from hollow fillers that have been conventionally blended in curable compositions used for forming low refractive index films, within a range that does not impair the object of the present invention. As the hollow filler (A), one type of particle may be used, or two or more types of particles may be used in combination.

[0022] Hollow fillers refer to particles that have an internal cavity surrounded by an outer shell. The porosity of the hollow filler is preferably 10 to 80%, more preferably 40 to 80%, and particularly preferably 50 to 70%, because the hollow filler (A) has good durability and is easy to form a low refractive index film.

[0023] The average particle size of the hollow filler (A) is not particularly limited as long as it does not impair the object of the present invention. The average particle size of the hollow filler (A) is preferably 1 to 200 nm, more preferably 10 to 100 nm, and further preferably 40 to 80 nm. The average particle size of the hollow filler (A) can be determined from an image obtained by observing the dispersed hollow filler particles with a transmission electron microscope. Specifically, the average particle size can be determined by the following steps 1) to 3): 1) The projected area of ​​each of a plurality of hollow filler particles is determined. 2) The circle equivalent diameter of each hollow filler particle is calculated from the projected area thus calculated. 3) The number average of the equivalent circle diameters of a plurality of hollow filler particles is calculated and this is regarded as the average particle diameter of the hollow filler (A). The average particle size is typically measured for 300 or more hollow filler particles.

[0024] The specific surface area of ​​the hollow filler (A) is 10 to 2000 m 2 / g is preferable, and 20 to 1800m 2 / g is more preferable, and 50 to 1500m 2 / g is particularly preferred.

[0025] The refractive index of the hollow filler (A) is preferably 1.10 to 1.40, more preferably 1.15 to 1.35, and particularly preferably 1.15 to 1.30. The refractive index here is the refractive index of the whole particle, and is not the refractive index of only the outer shell forming the hollow filler particle.

[0026] The material of the hollow filler particles is preferably an inorganic material from the viewpoint of lowering the refractive index of the low refractive index film. Examples of such inorganic materials include magnesium fluoride and silica particles. The inorganic material may be either a crystalline material or an amorphous material. As the hollow filler particles made of an inorganic material, hollow silica particles are preferred because they are easy to form a low refractive index film, can be easily and stably dispersed in a curable composition, and are inexpensive. The average primary particle size of the inorganic hollow filler particles is preferably from 1 to 100 nm, more preferably from 1 to 60 nm. The inorganic hollow filler particles may be monodisperse particles, or may contain aggregates formed by aggregation of primary particles.

[0027] When the hollow filler (A) is an inorganic particle, the surface of the inorganic particle may be subjected to a physical surface treatment such as a plasma discharge treatment or a corona discharge treatment, or a chemical surface treatment with a surfactant, a coupling agent, or the like, for the purpose of improving the dispersion stability of the hollow filler (A) in a dispersion liquid of the hollow filler (A) or in the curable composition, or for the purpose of increasing the affinity or binding property with components such as the polymerizable compound (B). Among such surface treatments, chemical surface treatments using coupling agents are preferred. As the coupling agent, a titanium coupling agent, a silane coupling agent, etc. are preferred, and a silane coupling agent is more preferred.

[0028] For example, when silica particles are treated with a silane coupling agent, organosilyl groups are bonded to the surfaces of the silica particles by a reaction between the silane coupling agent and silanol groups on the surfaces of the silica particles. Examples of the organic group introduced by the treatment with a silane coupling agent include a hydrocarbon group having 1 to 18 carbon atoms which may have an unsaturated bond, and a halogenated hydrocarbon group having 1 to 18 carbon atoms which may have an unsaturated bond. The surface treatment with a coupling agent may be carried out before the inorganic particles as the hollow filler (A) are blended into the curable composition, or the surface treatment of the hollow filler (A) may be carried out by adding a coupling agent to the curable composition.

[0029] The hollow filler (A) such as inorganic particles is preferably dispersed in a medium before preparing the curable composition, since this prevents aggregation and allows easy dispersion in the curable composition.

[0030] When silica particles are used as the hollow filler (A), commercially available silica particles can be suitably used. Specific examples of commercially available silica particles include the Surullia series manufactured by JGC Catalysts and Chemicals Co., Ltd. (isopropanol (IPA) dispersion, 4-methyl-2-pentanone (MIBK) dispersion, propylene glycol monomethyl ether dispersion, etc.); and Silinax manufactured by Nittetsu Mining Co., Ltd.

[0031] As described above, the hollow filler (A) is preferably blended in the curable composition as a dispersion in which it is dispersed in a medium. When silica particles are blended in the curable composition as a dispersion, the content of the silica particles in the dispersion is preferably from 10 to 50 mass %, more preferably from 15 to 40 mass %, and particularly preferably from 15 to 30 mass %.

[0032] When the hollow filler (A) is dispersed in a medium or a curable composition, a dispersing agent may be used. Specific examples of dispersants include dispersing resins such as polyamidoamines, polyamidoamine salts, polycarboxylic acids, polycarboxylates, high molecular weight unsaturated acid esters, modified polyurethanes, modified polyesters, modified poly(meth)acrylates, (meth)acrylic copolymers, and naphthalenesulfonic acid-formalin condensates. Furthermore, compounds such as polyoxyethylene alkyl phosphates, polyoxyethylene alkyl amines, and alkanol amines can be used as dispersants. Among the above dispersants, dispersing resins are preferred. Dispersing resins can be classified into linear polymers, terminal modified polymers, graft polymers, and block polymers based on their structures.

[0033] The dispersion resin is adsorbed to the surface of the hollow filler particles and acts to prevent the hollow filler particles from agglomerating, and therefore, examples of preferred structures include terminal modified polymers, graft polymers, and block polymers that have anchor sites to the hollow filler particle surfaces.

[0034] The mass average molecular weight (polystyrene equivalent value measured by GPC method) of the dispersing resin is preferably from 1,000 to 200,000, more preferably from 2,000 to 100,000, and particularly preferably from 5,000 to 50,000.

[0035] Dispersing resins are commercially available. Specific examples of commercially available dispersing resins include: BYKChemie's Disperbyk-101 (polyamidoamine phosphate), Disperbyk-107 (carboxylic acid ester), Disperbyk-110 (copolymer containing acid groups), Disperbyk-111 (polyamide), Disperbyk-130 (polyamide), Disperbyk-161 (polymer copolymer), Disperbyk-162 (polymer copolymer), Disperbyk-163 (polymer copolymer), Disperbyk-164 (polymer copolymer), Disperbyk-165 (polymer copolymer), Disperbyk-166 (polymer copolymer), Disperbyk-170 (polymer copolymer), BYK-P104 (high molecular weight unsaturated polycarboxylic acid), BYK-P105 (high molecular weight unsaturated polycarboxylic acid); EFKA4047 (polyurethane), EFKA4050-4010-4165 (polyurethane), EFKA4330-4340 (block copolymer), EFKA4400-4402 (modified polyacrylate), EFKA5010 (polyester amide), EFKA5765 (high molecular weight polycarboxylate), EFKA6220 (fatty acid polyester), EFKA6745 (phthalocyanine derivative), EFKA6750 (azo pigment derivative), manufactured by EFKA; Ajisper PB821 and Ajisper PB822, manufactured by Ajinomoto Fantechno Co., Ltd.; FLOLLEN TG-710 (urethane oligomer), POLYFLOW No. 50E (acrylic copolymer), and POLYFLOW No. 300 (acrylic copolymer), manufactured by Kyoeisha Chemical Co., Ltd.; Disparlon KS-860 (polymeric polyester amine salt), Disparlon KS-873SN (polymeric polyester amine salt), Disparlon KS-874 (polymeric polyester amine salt), Disparlon 2150 (aliphatic polycarboxylic acid), Disparlon 7004 (polyether ester), Disparlon DA-703-50, Disparlon DA-705, and Disparlon DA-725, manufactured by Kusumoto Chemicals Co., Ltd.; Kao Corporation's Demol RN (naphthalenesulfonic acid formalin polycondensate), Demol N (naphthalenesulfonic acid formalin polycondensate), Demol MS (aromatic sulfonic acid formalin polycondensate), Demol C (aromatic sulfonic acid formalin polycondensate), Demol SN-B (aromatic sulfonic acid formalin polycondensate), Homogenol L-18 (polymeric polycarboxylic acid), Emulgen 920 (polyoxyethylene nonylphenyl ether), Emulgen 930 (polyoxyethylene nonylphenyl ether), Emulgen 935 (polyoxyethylene nonylphenyl ether), Emulgen 985 (polyoxyethylene nonylphenyl ether), and Acetamine 86 (stearylamine acetate); Solsperse 5000 (phthalocyanine derivative), Solsperse 22000 (azo pigment derivative), Solsperse 13240 (polyesteramine), Solsperse 3000 (terminal modified polymer), Solsperse 17000 (terminal modified polymer), Solsperse 27000 (terminal modified polymer), Solsperse 24000 (graft type polymer), Solsperse 28000 (graft type polymer), Solsperse 32000 (graft type polymer), Solsperse 38500 (graft type polymer), manufactured by Lubrizol; Nikkol T106 (polyoxyethylene sorbitan monooleate) and MYS-IEX (polyoxyethylene monostearate), manufactured by Nikko Chemical Co., Ltd.; Morishita Sangyo Co., Ltd.'s EFKA-46, EFKA-47, EFKA-47EA, EFKA Polymer 100, EFKA Polymer 400, EFKA Polymer 401, EFKA Polymer 450; San Nopco's Disperse Aid 6, Disperse Aid 8, Disperse Aid 15, Disperse Aid 9100; Examples include:

[0036] As the dispersant, a nonionic, anionic or cationic surfactant can be used. These surfactants are commercially available. Specific examples of commercially available surfactants include: EFKA-745 manufactured by EFKA; organosiloxane polymer KP341 from Shin-Etsu Chemical Co.; Polymer Polyflow No. 75, Polymer Polyflow No. 90, Polymer Polyflow No. 95 manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.; W001, W004, W005, W017 made by Yu Shosha; Solsperse 3000, Solsperse 5000, Solsperse 9000, Solsperse 12000, Solsperse 13240, Solsperse 13940, Solsperse 17000, Solsperse 24000, Solsperse 26000, Solsperse 28000 manufactured by Nippon Lubrizol Co., Ltd.; ADEKA Corporation's ADEKA Pluronic (registered trademark; the same applies below) L31, ADEKA Pluronic F38, ADEKA Pluronic L42, ADEKA Pluronic L44, ADEKA Pluronic L61, ADEKA Pluronic L64, ADEKA Pluronic F68, ADEKA Pluronic L72, ADEKA Pluronic P95, ADEKA Pluronic F77, ADEKA Pluronic P84, ADEKA Pluronic F87, ADEKA Pluronic P94, ADEKA Pluronic L101, ADEKA Pluronic P103, ADEKA Pluronic F108, ADEKA Pluronic L121, ADEKA Pluronic P-123; IsoNet S-20 manufactured by Sanyo Chemical Industries; Hinoact T-8000E manufactured by Kawaken Fine Chemicals Co., Ltd.; ELEBASE BA-100, ELEBASE BA-200, ELEBASE BCP-2, ELEBASE BUB-3, ELEBASE BUB-4, ELEBASE CP-800K, ELEBASE EDP-475, ELEBASE HEB-5, FINESURF 270, FINESURF 7045, FINESURF 7085, BROWNON DSP-12.5, BROWNON DT-03, BROWNON L-205, BROWNON LPE-1007, BROWNON O-205, BROWNON S-202, BROWNON S-204, BROWNON S-207, BROWNON S-205T manufactured by Aoki Oil Industries; Kao Corporation's Emulgen A-500, Emulgen PP-290, Amit 102, Amit 105, Amit 302, Amit 320, Aminone PK-02S, Emanone CH-25, Emulgen 104P, Emulgen 108, Emulgen 404, Emulgen 408, Emulgen A-60, Emulgen A-90, Emulgen B-66, Emulgen LS-106, Emulgen LS-114, and Leodo Le 430V, Rheodor 440V, Rheodor 460V, Rheodor TW-S106, Rheodor TW-S120V, Rheodor Super TW-L120, Phosphanol ML-200, Emeral 20T, Emeral E-27, Neo Pelex GS, Pelex NBL, Pelex SS-H, Pelex SS-L, Poise 532A, Ramtel ASK, Ramtel E-118B, Ramtel E-150; New Calgen 3000S, New Calgen FS-3PG, New Calgen FE-7PG, Paionin D-6414, Paionin A-24-EA, Paionin A-28-B, Paionin A-29-M, Paionin A-44-B, and Paionin A-44TW manufactured by Takemoto Oil Co., Ltd.; Dynol 604, Olfin PD-002W, Surfynol 2502, Surfynol 440, Surfynol 465, Surfynol 485, and Surfynol 61 manufactured by Nissin Chemical Industry Co., Ltd.; Clariant's EMULSOGEN COL-020, EMULSOGEN 070, EMULSOGEN 080, Plysurf A208B, Plysurf A210B, Plysurf A210G, Plysurf A219B, Plysurf AL, and Lavelin FC-45 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; AKYPO RLM100NV, AKYPO RLM45, AKYPO RLM45NV, AKYPO ECT-3, AKYPO ECT-3NEX, AKYPO ECT-7, Hosten HLP, Hosten HLP-1, Hosten HLP-TEA manufactured by Nippon Surfactant and Kogyo Co., Ltd.; Examples include: These dispersants may be used alone or in combination of two or more kinds.

[0037] The content of the dispersant in the curable composition is preferably 1 to 100% by mass, more preferably 5 to 80% by mass, and particularly preferably 10 to 60% by mass, based on the mass of the hollow filler. When the dispersant is a dispersion resin, the amount of the dispersant used is preferably 5 to 100% by mass, more preferably 10 to 80% by mass, based on the mass of the hollow filler.

[0038] The amount of hollow filler (A) used in the curable resin composition is not particularly limited as long as it does not impair the object of the present invention. The content of hollow filler (A) in the curable composition is preferably 80 mass% or less, more preferably 20 to 80 mass%, and particularly preferably 30 to 70 mass%, based on the mass of the curable composition excluding the mass of the organic solvent (S) described below.

[0039] <Polymerizable compound (B)> The curable resin composition contains a polymerizable compound (B). The polymerizable compound (B) contains a compound (B1) having 5 or more polymerizable functional groups and a compound (B2) having 1 to 3 polymerizable functional groups. The ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 0.25 or more and 3 or less.

[0040] Examples of the polymerizable functional group include an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include a (meth)acryloyl group.

[0041] (Compound (B1) Having Five or More Polymerizable Functional Groups) The compound (B1) has 5 or more polymerizable functional groups, preferably 5 to 10, and more preferably 5 or 6. Two or more kinds of compound (B1) may be used in combination.

[0042] The compound (B1) is preferably a compound represented by the following formula (b1). (MA-(OR 11 -(CO) n13 ) n12 -X) n11 -A-((X) n15 -R 12 ) n14 (b1) In formula (b1), A is a hexavalent organic group, each MA is independently a (meth)acryloyl group, each X is independently an oxygen atom, -NH-, or -N(CH3)-, and R 11 are each independently an alkylene group having 1 to 10 carbon atoms; R 12 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an acyl group having 1 to 4 carbon atoms, n11 is 5 or 6, n12 is each independently an integer of 0 to 10, n13 is each independently 0 or 1, n14 is 0 or 1, n15 is 0 or 1, and n11+n14 is 6.

[0043] The hexavalent organic group represented by A preferably has 2 or more and 20 or less carbon atoms, more preferably 6 or more and 15 or less, and further preferably 10 or more and 12 or less carbon atoms.

[0044] Examples of the hexavalent organic group represented by A include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a heterocyclic group, and a group in which two or more groups selected from the group consisting of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a heterocyclic group are bonded via a single bond or a divalent linking group. Among these, an aliphatic hydrocarbon group and a group in which two or more aliphatic hydrocarbon groups are bonded via a divalent linking group are preferred, and a group in which two or more aliphatic hydrocarbon groups are bonded via a divalent linking group is more preferred. Examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups, aliphatic hydrocarbon groups containing a ring in the structure, etc. Among these, linear or branched aliphatic hydrocarbon groups are preferred, and linear or branched saturated aliphatic hydrocarbon groups are more preferred. Examples of the divalent linking group include -CONH-, -NH-, -N=N-, -CH=N-, -COO-, -O-, -CO-, -SO-, -SO2-, -S-, -SS-, etc. Of these, -O- is preferred.

[0045] Examples of the hexavalent organic group represented by A include groups having the following structures. [ka]

[0046] X is preferably an oxygen atom.

[0047] R 11 The alkylene group as the alkyl group preferably has 1 or more and 5 or less, more preferably 2 or 3, carbon atoms. R 11 Examples of the alkylene group having 1 to 10 carbon atoms include an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, and a propane-1,5-diyl group. Of these, an ethane-1,2-diyl group, a propane-1,2-diyl group, and a propane-1,3-diyl group are preferred.

[0048] R 12Examples of the alkyl group having 1 to 4 carbon atoms as the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Among these alkyl groups, a methyl group and an ethyl group are preferred. R 12 The number of carbon atoms in the acyl group as the alkyl group is preferably 1 or more and 3 or less. R 12 Examples of the acyl group having 1 to 5 carbon atoms as the aryl group include a group represented by -COR (R is a linear or branched alkyl group). R 12 is preferably a hydrogen atom or an acyl group having 1 to 5 carbon atoms.

[0049] n12 is preferably 0 or more and 5 or less, more preferably 0 or more and 3 or less, and further preferably 0. n13 is preferably 0. n15 is preferably 1.

[0050] Preferred examples of the compound represented by formula (b1) include dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, alkylene oxide-modified dipentaerythritol penta(meth)acrylate, alkylene oxide-modified dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, KAYARAD D-310 manufactured by Nippon Kayaku Co., Ltd., and SA-TE manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. Among them, dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate are more preferred.

[0051] (Compound (B2) having 1 to 3 polymerizable functional groups) The compound (B2) has 1 or more and 3 or less polymerizable functional groups, and preferably 3. Two or more kinds of compound (B2) may be used in combination.

[0052] Among the compounds (B2), examples of the compounds having one polymerizable functional group include (meth)acrylamide, methylol (meth)acrylamide, methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, butoxymethoxymethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, (meth)acrylic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, crotonic acid, 2-acrylamido-2-methylpropanesulfonic acid, tert-butylacrylamidosulfonic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2- Examples of the acrylates include ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, glycerin mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, half (meth)acrylate of phthalic acid derivatives, and isobornyl (meth)acrylate.

[0053] Among the compounds (B2), examples of the compounds having two or three polymerizable functional groups include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexane glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, alkylene oxide-modified trimethylolpropane tri(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, and the like. Examples of the acrylates include thritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, 2-hydroxy-3-(meth)acryloyloxypropyl(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, glycerin tri(meth)acrylate, tri(meth)acrylformal, and tricyclodecane dimethanol di(meth)acrylate.

[0054] The compound (B2) is preferably a compound represented by the following formula (b2-1) or (b2-2). (MA-(OR 21 -(CO) n22 ) n21 -X-CH2)3-C-CH2-R 22 (b2-1) (MA-(OR 21 -(CO) n22 ) n21 -X-CH2)2-CH-X-((CO) n22 -R 21 -O) n21 -MA···(b2-2) (In formula (b2-1) and formula (b2-2), each MA is independently a (meth)acryloyl group; each X is independently an oxygen atom, -NH-, or -N(CH3)-; R 21 are each independently an alkylene group having 1 to 10 carbon atoms; R 22 is a hydroxyl group or an alkyl group having 1 to 4 carbon atoms, each n21 is independently an integer of 0 to 10, and each n22 is independently 0 or 1.

[0055] X is preferably an oxygen atom.

[0056] R 21 The alkylene group as the alkyl group preferably has 1 or more and 5 or less, more preferably 2 or 3, carbon atoms. R 21 Examples of the alkylene group having 1 to 10 carbon atoms include an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, and a propane-1,5-diyl group. Of these, an ethane-1,2-diyl group, a propane-1,2-diyl group, and a propane-1,3-diyl group are preferred.

[0057] R 22 Examples of the alkyl group having 1 to 4 carbon atoms as the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Among these alkyl groups, a methyl group and an ethyl group are preferred. n21 is preferably 0 or more and 5 or less, and more preferably 1 or more and 3 or less. n22 is preferably 0.

[0058] Preferred examples of the compound represented by the following formula (b2-1) or (b2-2) include trimethylolpropane tri(meth)acrylate, alkylene oxide-modified trimethylolpropane tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, alkylene oxide-modified glycerin tri(meth)acrylate, caprolactone-modified glycerin tri(meth)acrylate, etc. Among them, alkylene oxide-modified trimethylolpropane tri(meth)acrylate is more preferred.

[0059] The ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is from 0.25 to 3, preferably from 1.1 to 2.5, and more preferably from 1.25 to 2. When the ratio is from 0.25 to 3, a cured film having excellent heat resistance can be formed.

[0060] The total content of the compound (B1) and the compound (B2) in the polymerizable compound (B) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 100% by mass.

[0061] The content of the polymerizable compound (B) is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, based on the mass of the curable composition excluding the mass of the organic solvent (S) described below.

[0062] <Polymerization initiator (C)> The curable composition contains a polymerization initiator (C). The polymerization initiator (D) is not particularly limited, and a conventionally known photopolymerization initiator or thermal polymerization initiator can be used. Among them, a photopolymerization initiator is preferable. The polymerization initiator can be used alone or in combination of two or more kinds.

[0063] The photopolymerization initiator is not particularly limited, and any conventionally known photopolymerization initiator can be used. Specific examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, bis(4-dimethylaminophenyl)ketone, 2-methylpropan-1-one, and the like. 2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, O-acetyl-1-[6-(2-methylbenzoyl)-9-ethyl-9H-carbazol-3-yl]ethanone oxime, O-acetyl-1-[6-(pyrrol-2-ylcarbonyl)-9-ethyl-9H-carbazol-3-yl]ethanone oxime, (9-ethyl-6-nitro-9H-carbazol-3-yl)[4-(2-methoxy-1-methylethoxy)-2- methylphenyl]methanone O-acetyloxime, 2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]-1-octanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 4-benzoyl-4'-methyldimethyl sulfide, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, butyl 4-dimethylaminobenzoate, 4-dimethylamino-2-ethylhexylbenzoic acid, 4-dimethylamino-2-isoamylbenzoic acid, benzyl-β-methoxyethyl a cetal, benzyl dimethyl ketal, 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime, o-benzoylmethylbenzoate, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 1-chloro-4-propoxythioxanthone, thioxanthene, 2-chlorothioxanthene, 2,4-diethylthioxanthene, 2-methylthioxanthene, 2-isopropylthioxanthene, 2-ethylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-Diphenylanthraquinone, azobisisobutyronitrile, benzoyl peroxide, cumene hydroperoxide, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-(o-chlorophenyl)-4,5-di(m-methoxyphenyl)-imidazolyl dimer, benzophenone, 2-chlorobenzophenone, p,p'-bisdimethylaminobenzophenone, 4,4'-bisdiethylaminobenzophenone, 4,4'-dichlorobenzophenone, 3,3-dimethyl-4-methoxy Benzophenone, benzil, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, benzoin butyl ether, acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, dichloroacetophenone, trichloroacetophenone, p-tert-butylacetophenone, p-dimethylaminoacetophenone, p-tert-butyltrichloroacetophenone acetophenone, p-tert-butyldichloroacetophenone, α,α-dichloro-4-phenoxyacetophenone, thioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, dibenzosuberone, pentyl-4-dimethylaminobenzoate, 9-phenylacridine, 1,7-bis-(9-acridinyl)heptane, 1,5-bis-(9-acridinyl)pentane, 1,3-bis-(9-acridinyl)propane, p-methoxytriazine, 2,4,6-tris(trichloromethyl)-s-triazine, 2-methyl-4,6- Bis(trichloromethyl)-s-triazine, 2-[2-(5-methylfuran-2-yl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(furan-2-yl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(4-diethylamino-2-methylphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(3,4-dimethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxyphenyl)-4,Examples of the photopolymerization initiator include 6-bis(trichloromethyl)-s-triazine, 2-(4-ethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-n-butoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis-trichloromethyl-6-(3-bromo-4-methoxy)phenyl-s-triazine, 2,4-bis-trichloromethyl-6-(2-bromo-4-methoxy)phenyl-s-triazine, 2,4-bis-trichloromethyl-6-(3-bromo-4-methoxy)styrylphenyl-s-triazine, and 2,4-bis-trichloromethyl-6-(2-bromo-4-methoxy)styrylphenyl-s-triazine. These photopolymerization initiators can be used alone or in combination of two or more.

[0064] The thermal polymerization initiator is not particularly limited, and any conventionally known thermal polymerization initiator can be used. Specific examples of the thermal polymerization initiator include ketone peroxides (methyl ethyl ketone peroxide, cyclohexanone peroxide, etc.), peroxyketals (2,2-bis(tert-butylperoxy)butane, 1,1-bis(tert-butylperoxy)cyclohexane, etc.), hydroperoxides (tert-butyl hydroperoxide, cumene hydroperoxide, etc.), dialkyl peroxides (di-tert-butyl peroxide (Perbutyl (registered trademark) D (manufactured by NOF Corporation) and di-tert-hexyl peroxide (Perhexyl (registered trademark) D (manufactured by NOF Corporation))), diacyl peroxides (isobutyryl peroxide, lauroyl peroxide, benzoyl peroxide, etc.), peroxydicarbonates (diisopropyl peroxydicarbonate, etc.), peroxyesters (tert-butyl peroxyisobutyrate and 2,5-dimethyl peroxyisobutyrate), Organic peroxides such as 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[2-methyl-N-(2-propenyl)propionamidine] dihydrochloride, etc. Examples of the thermal polymerization initiator include azo compounds such as dimethyl 2,2'-azobis(2-methylpropionamide), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2-methylpropane), 2,2'-azobis(2,4,4-trimethylpentane) and dimethyl 2,2'-azobis(2-methylpropionate). These thermal polymerization initiators can be used alone or in combination of two or more.

[0065] The content of the polymerization initiator (C) is preferably 0.5 to 30 mass %, more preferably 1 to 20 mass %, based on the mass of the curable composition excluding the mass of the organic solvent (S) described below. By setting the content of the polymerization initiator (C) within the above range, a curable composition having good curability can be obtained.

[0066] <Surfactant (D)> The curable composition preferably contains a surfactant (D).

[0067] As the surfactant (D), any of nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants can be used. The surfactant (D) may be a fluorine-based surfactant, a silicon-based surfactant, etc. As the surfactant (D), a fluorine-based surfactant or a silicon-based surfactant is preferred, and a silicon-based surfactant is more preferred. Two or more types of surfactants (D) may be used in combination.

[0068] The fluorosurfactant is not particularly limited as long as it is a surfactant containing a fluorine atom, and may be any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant. Two or more types of fluorosurfactants may be used in combination.

[0069] Specific examples of fluorine-based surfactants include commercially available fluorine-based surfactants such as BM-1000, BM-1100 (all manufactured by BM Chemie), Megafac F142D, Megafac F172, Megafac F173, Megafac F183 (all manufactured by Dainippon Ink and Chemicals), Fluorad FC-135, Fluorad FC-170C, Fluorad FC-430, Fluorad FC-431 (all manufactured by Sumitomo 3M), Surflon S-112, Surflon S-113, Surflon S-131, Surflon S-141, Surflon S-145 (all manufactured by Asahi Glass Co., Ltd.), SH-28PA, SH-190, SH-193, SZ-6032, and SF-8428 (all manufactured by Toray Silicones), but are not limited to these.

[0070] As the fluorine-based surfactant, a compound having a fluoroalkyl group on the side chain is also preferred. Examples of the compound having a fluoroalkyl group on the side chain include the compounds represented by the following formulas (e-1) to (e-4). In formula (e-1) and formula (e-2), x1 is an integer of 0 to 7. In formula (e-3), x2 is an integer of 0 to 8. In formula (e-4), x3 is an integer of 6 to 20. [ka] [ka] [ka]

[0071] As the silicon-based surfactant, a polysiloxane-based surfactant is preferred. Silicone surfactants are surfactants that contain silicon atoms. Polysiloxane surfactants are surfactants that have a main chain consisting of repeated Si-O bonds.

[0072] Examples of polysiloxane surfactants include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, and aralkyl-modified polymethylalkylsiloxane.

[0073] Polysiloxane-based surfactants are commercially available, and examples thereof include BYK-331, BYK-310, and BYK-322 manufactured by BYK Japan Co., Ltd.; and TEGO Glide 440 manufactured by Evonik.

[0074] The content of the surfactant (D) is preferably 0.001 to 3 mass%, more preferably 0.001 to 2 mass%, further preferably 0.001 to 1.5 mass%, and most preferably 0.001 to 1 mass%, based on the total mass of the hollow filler (A) and the polymerizable compound (B) in the curable composition.

[0075] <Alkali-soluble resin> The curable composition does not contain an alkali-soluble resin. In this specification, an alkali-soluble resin refers to a resin that dissolves to a thickness of 0.01 μm or more when a resin film of 1 μm thickness is formed on a substrate using a resin solution (solvent: propylene glycol monomethyl ether acetate) with a resin concentration of 20 mass % and then immersed in an aqueous solution of tetramethylammonium hydroxide (TMAH) with a concentration of 0.05 mass % for 1 minute. Examples of such alkali-soluble resins include alkali-soluble resins that are incorporated into various compositions used in processes involving development with an alkaline developer.

[0076] <Organic solvent (S)> The curable composition preferably contains an organic solvent (S) for improving the coatability and adjusting the viscosity.

[0077] Specific examples of the organic solvent (S) include alkane monools such as methanol, ethanol, n-propanol, isopropanol, and n-butanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, 3-methoxy-n-butanol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono (Poly)alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, and other (poly)alkylene glycol monoalkyl ether acetates; other ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, tetrahydrofuran, and other ketones such as methyl ethyl ketone, cyclohexanone, 2-heptanone, and 3-heptanone; alkyl esters of lactate such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate;Ethyl 2-hydroxy-2-methylpropionate, Methyl 3-methoxypropionate, Ethyl 3-methoxypropionate, Methyl 3-ethoxypropionate, Ethyl 3-ethoxypropionate, Ethoxyethyl acetate, Ethyl hydroxyacetate, Methyl 2-hydroxy-3-methylbutanoate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutylpropionate, Ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, n-pentyl formate, i-pentyl acetate, benzyl acetate, n-butyl propionate, Ethyl butyrate, n-propyl butyrate, i-propy butyrate Other esters such as butyl, n-butyl butyrate, methyl pyruvate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, ethyl 2-oxobutanoate, 1,4-butanediol diacetate, etc.; aromatic hydrocarbons such as toluene and xylene; nitrogen-containing polar organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylisobutyric acid, N,N-diethylacetamide, N,N-diethylformamide, N-methylcaprolactam, 1,3-dimethyl-2-imidazolidinone, pyridine, and N,N,N',N'-tetramethylurea; etc.;

[0078] Among these, 1,4-butanediol diacetate, (poly)alkylene glycol monoalkyl ether acetates, and (poly)alkylene glycol monoalkyl ethers are preferred, and (poly)alkylene glycol monoalkyl ethers are more preferred. In terms of the solubility of each component, it is also preferable that the organic solvent (S) contains a nitrogen-containing polar organic solvent. As the nitrogen-containing polar organic solvent, N,N,N',N'-tetramethylurea, etc. can be used. These solvents can be used alone or in combination of two or more kinds.

[0079] The content of the organic solvent (S) is not particularly limited, and is appropriately set according to the coating film thickness at a concentration that allows application to a substrate, etc. For example, the viscosity of the curable composition is preferably 1 to 500 cp, more preferably 1 to 50 cp, and even more preferably 1 to 30 cp. The solid content concentration of the curable composition is preferably 1 to 50 mass%, and more preferably 1 to 20 mass%.

[0080] <Other ingredients> The curable composition may contain additives such as a photoacid generator, an adhesion improver, a thermal polymerization inhibitor, an antifoaming agent, a colorant, a silane coupling agent, etc. Any of the additives may be a conventionally known additive.

[0081] The curable composition preferably contains a silane coupling agent because it is easy to form a low refractive index film that has a good shape and excellent adhesion to the substrate. As the silane coupling agent, any conventionally known silane coupling agent can be used without any particular limitation.

[0082] <Manufacturing method of low refractive index film> As a method for producing the low refractive index film, a conventionally known method for producing a low refractive index film using a curable composition containing a polymerizable compound (B) can be used without any particular limitation.

[0083] A suitable method for producing a low refractive index film is forming a coating film of the curable composition; and curing the coating film.

[0084] In order to form a low refractive index film using a curable composition, first, the curable composition is applied onto a substrate selected depending on the application of the low refractive index film to form a coating film. As the substrate, when an image sensor is formed, for example, a substrate having RGB colored films on a semiconductor layer such as silicon and having microlenses on the colored films is used.

[0085] The method for forming the coating film is not particularly limited, and may be, for example, a contact transfer type coating device such as a roll coater, a reverse coater, or a bar coater, or a non-contact type coating device such as a spinner (spin coater, rotary coating device), a dip coater, a spray coater, a slit coater, or a curtain flow coater. Of these, a spin coating method using a spinner, a spray coating method using a spray coater, a slit coating method using a slit coater, a bar coating method using a bar coater, or a dip coating method using a dip coater is preferred.

[0086] The applied curable composition is dried as necessary to form a coating film. The drying method is not particularly limited, and examples thereof include (1) a method of drying on a hot plate at a temperature of 80 to 120°C, preferably 90 to 100°C, for 60 to 120 seconds, (2) a method of leaving it at room temperature for several hours to several days, and (3) a method of placing it in a hot air heater or an infrared heater for several tens of minutes to several hours to remove the solvent.

[0087] The coating film is then cured. The curing method is not particularly limited, and may be exposure to light, heating, or a combination of exposure to light and heating. Of these, curing by exposure to light is preferred. Exposure is performed by irradiating the coating film with active energy rays such as ultraviolet light or excimer laser light.

[0088] Next, the cured film may be baked (post-baked). The baking temperature is not particularly limited, but is preferably 180 to 250° C., and more preferably 220 to 230° C. The baking time is typically 10 to 90 minutes, and preferably 20 to 60 minutes.

[0089] The cured film thus formed can be suitably used as a low refractive index film. When the cured film is used as a low refractive index film, the refractive index of the low refractive index film (wavelength 633 nm, measurement temperature 25° C.) is preferably 1.4 or less, more preferably 1.25 to 1.38.

[0090] The low refractive index film can be preferably used in optical devices such as image sensors, etc. When the low refractive index film is used as a coating layer for coating a microlens formed on an RGB colored film in an image sensor, the reflection of light incident on the microlens is improved, thereby suppressing the occurrence of flare in the image sensor. The above-mentioned curable composition can form a cured film having excellent heat resistance, and therefore can be used in the production of optical devices which require heat treatment steps such as solder reflow and post-bake. EXAMPLES

[0091] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0092] [Examples 1 to 6 and Comparative Examples 1 to 6] The following hollow filler (A) in the amount shown in Table 1, the following polymerizable compound (B) in the type and amount shown in Table 1, the following polymerization initiator (C) in the amount shown in Table 1, and 0.01 parts by mass of the following surfactant (D) of the type shown in Table 1 were mixed into the following organic solvent (S) to give a solids concentration of 31 mass%, to obtain curable resin compositions for each of the Examples and Comparative Examples.

[0093] As the hollow filler (component (A)), Sururia 4330 (product name, manufactured by JGC Catalysts and Chemicals, a dispersion of hollow silica particles having an average primary particle size of 60 nm, solid content concentration of 30% by mass) was used.

[0094] As the polymerizable compound (component (B)), the following B1 and B2 were used. B1: KAYARAD DPHA (product name, manufactured by Nippon Kayaku Co., Ltd., a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate) B2: M-360 (product name, manufactured by Toagosei Co., Ltd., trimethylolpropane EO-modified triacrylate represented by the following formula, n≒2) [CH2=CHCO-(OC2H4) n -OCH2]3-CCH2CH3 B3: NK Ester A-DCP (product name, manufactured by Shin-Nakamura Chemical Co., Ltd., tricyclodecane dimethanol diacrylate) B4: Light Ester IB-X (product name, Kyoeisha Chemical Co., Ltd., isobornyl methacrylate)

[0095] As the polymerization initiator (component (C)), 1-hydroxycyclohexyl phenyl ketone was used.

[0096] As the surfactant (component (D)), the following D1 to D3 were used. D1: PF-656 (product name, manufactured by Omnova, fluorosurfactant represented by the following formula) [ka] D2: BYK-310 (product name, BYK Japan Co., Ltd., polyester-modified polydimethylsiloxane, silicone surfactant) D3: TEGO Glide 440 (product name, manufactured by Evonik, polyether-modified polysiloxane copolymer, silicone surfactant)

[0097] As the organic solvent (component (S)), propylene glycol monomethyl ether was used.

[0098] 〔evaluation〕 The curable resin compositions of the Examples and Comparative Examples were evaluated for appearance, refractive index, and heat resistance according to the following methods. The evaluation results are shown in Table 1.

[0099] (exterior) The curable resin composition of each Example and Comparative Example was applied onto a glass substrate using a spin coater (MS-B200 manufactured by Mikasa Co., Ltd.) so that the applied film had a thickness of 3000 nm. The formed applied film was heated (prebaked) at 100°C for 1 minute, and then exposed to light at 1 J / cm using an exposure device (imprint device ST-200 manufactured by Shibaura Machine Co., Ltd.). 2 The cured film was then exposed to light at a vacuum of 200 Pa to obtain a cured film. If the appearance of the obtained cured film was colorless and transparent, it was evaluated as "◯", and if it was cloudy, it was evaluated as "×".

[0100] (Refractive Index) The curable resin composition of each Example and Comparative Example was applied onto a silicon substrate using a spin coater (MS-B200 manufactured by Mikasa Co., Ltd.) so that the applied film had a thickness of 1000 nm. The formed applied film was heated (prebaked) at 100° C. for 1 minute, and then exposed to light at 1 J / cm 2 using an exposure device (imprint device ST-200 manufactured by Shibaura Machine Co., Ltd.). 2 The cured film was then exposed to light at a vacuum of 200 Pa to obtain a cured film. The refractive index of the cured film was measured using a refractive index measuring device (Spectroscopic Ellipsometer M-2000 manufactured by JA Woollam Corporation).

[0101] (heat resistance) The thickness of the cured film obtained in the appearance evaluation was measured. The cured film was heated at 260°C for 10 seconds three times, and the thickness of the cured film after heating was measured. The change in thickness before and after heating was calculated based on the following formula, and a change in thickness of 1% or less was evaluated as "◎", a change in thickness of more than 1% and less than 2% was evaluated as "○", and a change in thickness of more than 2% was evaluated as "×". Film thickness change rate (%) = (|film thickness before heating - film thickness after heating| / film thickness before heating) × 100

[0102] [Table 1]

[0103] According to Table 1, in a curable composition containing a hollow filler (A), a polymerizable compound (B), a polymerization initiator (C), and a surfactant (D) and not containing an alkali-soluble resin, when the polymerizable compound (B) contains a compound (B1) having 5 or more polymerizable functional groups and a compound (B2) having 1 to 3 polymerizable functional groups, and the ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 0.25 to 3, a cured film having excellent heat resistance can be formed. On the other hand, when the polymerizable compound (B) contains only one of the compound (B1) having 5 or more polymerizable functional groups and the compound (B2) having 1 to 3 polymerizable functional groups, or when the ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is not 0.25 to 3, a cured film having poor heat resistance is obtained.

Claims

1. A composition comprising a hollow filler (A), a polymerizable compound (B), and a polymerization initiator (C), and does not contain an alkali-soluble resin; the polymerizable compound (B) includes a compound (B1) having 5 or more polymerizable functional groups and a compound (B2) having 1 or more and 3 or less polymerizable functional groups, A curable composition for forming a low refractive index film, wherein a ratio (B1 / B2) of a mass of the compound (B1) to a mass of the compound (B2) is 0.25 or more and 3 or less.

2. the compound (B1) is a compound having 5 or 6 polymerizable functional groups, The curable composition for forming a low refractive index film according to claim 1 , wherein the compound (B2) is a compound having three polymerizable functional groups.

3. The curable composition for forming a low refractive index film according to claim 1, wherein a ratio (B1 / B2) of a mass of the compound (B1) to a mass of the compound (B2) is 1.25 or more and 2 or less.

4. The curable composition for forming a low refractive index film according to claim 1 , further comprising a surfactant (D).

5. The curable composition for forming a low refractive index film according to claim 4 , wherein the surfactant (D) comprises a fluorine-based surfactant and / or a silicon-based surfactant.

6. The curable composition for forming a low refractive index film according to claim 1 , wherein the hollow filler (A) comprises hollow silica.

7. A low refractive index film comprising a cured product of the curable composition for forming a low refractive index film according to any one of claims 1 to 6.

8. An optical device comprising the low refractive index film according to claim 7.

9. A step of forming a coating film of the curable composition for forming a low refractive index film according to any one of claims 1 to 6; and curing the coating film.

10. The method for producing a low refractive index film according to claim 9 , wherein the coating film is formed by a spin coating method, a spray coating method, a slit coating method, a bar coating method, or a dip coating method.

11. The method for producing a low refractive index film according to claim 9 , wherein the coating film is cured by exposure to light.

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