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

Abstract

The 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 the low-refractive-index film. The present invention addresses the problem of providing a curable composition for forming a low-refractive-index film, which is capable of forming a cured film having excellent heat resistance. [Solution] A curable composition for forming a low-refractive-index film, which contains a hollow filler (A), a polymerizable compound (B) and a polymerization initiator (C) and does not contain an alkali-soluble resin, and wherein: the polymerizable compound (B) contains a compound (B1) having five or more polymerizable functional groups and a compound (B2) having one or more polymerizable functional groups (inclusive); the ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 0.25-3 (inclusive).

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 Art

[0002] Low refractive index films are used in optical components as optical functional films included in anti-reflection films, reflective films, semi-transmissive and semi-reflective films, visible light reflecting infrared transmitting films, infrared reflecting visible light transmitting films, blue reflecting films, green reflecting films, red reflecting films, bright line cutoff filters, color tone correction films, etc. (see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-271444 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the production process of optical components, heat treatment steps such as reflow and post-baking are sometimes performed. Therefore, heat resistance is also required for low-refractive index films, but sufficient research has not been conducted on this point.

[0008] The present invention has been made in view of the above circumstances, and its object 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 formed from a cured product of the curable composition, an optical device having the low refractive index film, and a method for producing a low refractive index film using the curable composition.

[0009] Means for solving problems

[0010] In order to solve the above-mentioned problems, the inventors of the present application have repeatedly conducted in-depth research and found that if the mass ratio (B1 / B2) of the compound (B1) having 5 or more polymerizable functional groups to the compound (B2) having 1 or more and 3 or less polymerizable functional groups 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 is 0.25 or more and 3 or less, the above-mentioned problems can be solved, thereby completing the present invention. Specifically, the present invention provides the following aspects.

[0011] [1] A curable composition for forming a low refractive index film, comprising a hollow filler (A), a polymerizable compound (B) and a polymerization initiator (C) but not containing an alkali-soluble resin,

[0012] 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.

[0013] 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.

[0014] [2] The curable composition for forming a low refractive index film according to [1], wherein the compound (B1) is a compound having 5 or 6 polymerizable functional groups,

[0015] The compound (B2) is a compound having three polymerizable functional groups.

[0016] [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.

[0017] [4] The curable composition for forming a low refractive index film according to any one of [1] to [3], further comprising a surfactant (D).

[0018] [5] The curable composition for forming a low refractive index film according to [4], wherein the surfactant (D) comprises a fluorine-based surfactant and / or a silicon-based surfactant.

[0019] [6] The curable composition for forming a low refractive index film according to any one of [1] to [5], wherein the hollow filler (A) comprises hollow silica.

[0020] [7] A low refractive index film formed from a cured product of the curable composition for forming a low refractive index film according to any one of [1] to [6].

[0021] [8] An optical device comprising the low refractive index film described in [7].

[0022] [9] A method for producing a low refractive index film, comprising the following steps:

[0023] 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

[0024] A step of curing the coating film.

[0025]

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

[0026]

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

[10] , wherein the coating film is cured by exposure.

[0027] Effects of the Invention

[0028] According to the present invention, there can be provided 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 formed from a cured product of the curable composition, an optical device having the low refractive index film, and a method for producing a low refractive index film using the curable composition. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

[0030] In addition, unless otherwise specified, "to" in this specification means above (lower limit value) to below (upper limit value).

[0031] In the present specification, when simply described as a "curable composition", it means a "curable composition for forming a low refractive index film" unless otherwise specified.

[0032] In this specification, "(meth)acrylate" includes both acrylate and methacrylate.

[0033] In this specification, "(meth)acryl-" includes both "acryl-" and "methacryl-".

[0034] In this specification, "(meth)acryloyl group" includes both an acryloyl group and a methacryloyl group.

[0035] 《Curable composition for forming a low refractive index film》

[0036] The curable composition for forming a low refractive index film contains a hollow filler (A), a polymerizable compound (B) and a polymerization initiator (C) but 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 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. By using such a curable composition, a cured film with excellent heat resistance can be formed.

[0037] <Hollow filler (A)>

[0038] In order to form a low refractive index film showing a refractive index as low as desired, the curable composition contains a hollow filler (A). The hollow filler (A) can be appropriately selected from hollow fillers conventionally used in curable compositions for forming low refractive index films within the range not hindering the purpose of the present invention.

[0039] As the hollow filler (A), one kind of particles may be used, or two or more kinds of particles may be used in combination.

[0040] Hollow fillers refer to particles having a cavity inside surrounded by an outer shell.

[0041] From the viewpoint of good durability of the hollow filler (A) and easy formation of a low refractive index film, the void ratio of the hollow filler is preferably 10 to 80%, more preferably 40 to 80%, and particularly preferably 50 to 70%.

[0042] The average particle size of the hollow filler (A) is not particularly limited within a range not inhibiting the purpose 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 even more preferably 40 to 80 nm.

[0043] The average particle size of the hollow filler (A) can be determined from an image obtained by observing dispersed hollow filler particles using a transmission electron microscope. Specifically, the following steps 1) to 3) are performed:

[0044] 1) For each of a plurality of hollow filler particles, the projected area is calculated.

[0045] 2) From the obtained projected area, the equivalent circle diameter of each hollow filler particle is obtained.

[0046] 3) The number average of the equivalent circle diameters of a plurality of hollow filler particles is calculated and taken as the average particle size of the hollow filler (A).

[0047] In addition, the average particle size is typically measured on 300 or more hollow filler particles.

[0048] The specific surface area of ​​the hollow filler (A) is preferably 10 to 2000 m 2 / g, more preferably 20 to 1800 m 2 / g, particularly preferably 50 to 1500 m 2 / g.

[0049] 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 refers to the refractive index of the entire particle, not the refractive index of only the outer shell forming the hollow filler particle.

[0050] From the perspective of lowering the refractive index of the low-refractive index film, the material of the hollow filler particles is preferably an inorganic material. Examples of the inorganic material include particles of magnesium fluoride and silicon dioxide. The inorganic material may be a crystalline material or an amorphous material.

[0051] As the hollow filler particles formed of an inorganic material, hollow silica particles are preferred from the viewpoints of easy formation of a low refractive index film having a low refractive index, easy and stable dispersion in a curable composition, and low cost.

[0052] The average primary particle size of the inorganic hollow filler particles is preferably 1 to 100 nm, more preferably 1 to 60 nm.

[0053] The inorganic hollow filler particles may be monodisperse particles or may include aggregates formed by agglomeration of primary particles.

[0054] 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 using a surfactant, a coupling agent, or the like, in order to improve the dispersion stability of the hollow filler (A) in a dispersion of the hollow filler (A) or in a curable composition, and to improve the affinity and bonding properties with components such as a polymerizable compound (B).

[0055] Among the surface treatments, chemical surface treatment using a coupling agent is preferred.

[0056] As the coupling agent, a titanium coupling agent, a silane coupling agent, etc. are preferred, and a silane coupling agent is more preferred.

[0057] For example, when silica particles are treated with a silane coupling agent, the organic silyl groups are bonded to the surfaces of the silica particles through the reaction between the silane coupling agent and the silanol groups on the surfaces of the silica particles.

[0058] Examples of the organic group introduced by the treatment with the 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.

[0059] The surface treatment with a coupling agent may be performed before the inorganic particles as the hollow filler (A) are added to the curable composition. Alternatively, the surface treatment of the hollow filler (A) may be performed by adding a coupling agent to the curable composition.

[0060] From the viewpoint of preventing aggregation and facilitating dispersion in the curable composition, the hollow filler (A) such as inorganic particles is preferably dispersed in a medium before preparing the curable composition.

[0061] When using silica particles as the hollow filler (A), commercially available silica particles can be preferably used.

[0062] Specific examples of commercially available silica particles include THRULYA series (isopropyl alcohol (IPA) dispersion, 4-methyl-2-pentanone (MIBK) dispersion, propylene glycol monomethyl ether dispersion, etc.) manufactured by JGC Catalysts & Chemicals Co., Ltd. and SiliNax manufactured by Nippon Steel Mining Co., Ltd.

[0063] As described above, the hollow filler (A) is preferably blended into the curable composition in the form of a dispersion dispersed in a medium.

[0064] When the silica particles are mixed in the curable composition as a dispersion, the content of the silica particles in the dispersion is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and particularly preferably 15 to 30% by mass.

[0065] When the hollow filler (A) is dispersed in a medium or a curable composition, a dispersant may be used.

[0066] Specific examples of the dispersant include dispersing resins such as polyamide amine, polyamide amine salts, polycarboxylic acids, polycarboxylates, high molecular weight unsaturated acid esters, modified polyurethanes, modified polyesters, modified poly(meth)acrylates, (meth)acrylic acid copolymers, and naphthalenesulfonic acid formaldehyde condensates.

[0067] In addition, compounds such as polyoxyethylene alkyl phosphate, polyoxyethylene alkylamine, and alkanolamine can be used as the dispersant.

[0068] Among the above-mentioned dispersants, dispersion resins are preferred. Dispersion resins can be classified into linear polymers, terminal-modified polymers, graft polymers, and block polymers according to their structures.

[0069] The dispersing resin can be adsorbed on the surface of the hollow filler particles to prevent the aggregation of the hollow filler particles. Therefore, terminal modified polymers, graft polymers, and block polymers having anchoring sites on the surface of the hollow filler particles can be cited as preferred structures.

[0070] The mass average molecular weight (value measured by GPC method in terms of polystyrene) of the dispersion resin is preferably 1,000 to 200,000, more preferably 2,000 to 100,000, and particularly preferably 5,000 to 50,000.

[0071] The dispersion resin is available as a commercial product.

[0072] Specific examples of commercially available dispersion resins include:

[0073] 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) manufactured by BYK Chemie;

[0074] EFKA 4047 (polyurethane), EFKA 4050-4010-4165 (polyurethane), EFKA 4330-4340 (block copolymer), EFKA 4400-4402 (modified polyacrylate), EFKA 5010 (polyester amide), EFKA 5765 (high molecular weight polycarboxylate), EFKA 6220 (fatty acid polyester), EFKA 6745 (phthalocyanine derivative), EFKA 6750 (azo pigment derivative) manufactured by EFKA;

[0075] AJISPER PB821 and AJISPE R PB822 manufactured by Ajinomoto Fine-Techno Co., Inc.;

[0076] FLOWLEN TG-710 (urethane oligomer), Polyflow No.50E (acrylic copolymer), Polyflow No.300 (acrylic copolymer) manufactured by Kyoeisha Chemical Co., Ltd.;

[0077] DISPARLON KS-860 (polymer polyester amine salt), DISPARLON KS-873SN (polymer polyester amine salt), DISPARLON KS-874 (polymer polyester amine salt), DISPARLON 2150 (aliphatic polycarboxylic acid), DISPARLON 7004 (polyether ester), DISPARLON DA-703-50, DISPARLON DA-705, DISPARLON DA-725 manufactured by Kusumoto Chemicals Co., Ltd.

[0078] Demol RN (naphthalenesulfonic acid formaldehyde condensation product), Demol N (naphthalenesulfonic acid formaldehyde condensation product), Demol MS (aromatic sulfonic acid formaldehyde condensation product), Demol C (aromatic sulfonic acid formaldehyde condensation product), Demol SN-B (aromatic sulfonic acid formaldehyde condensation product), 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 ACETAMIN 86 (stearylamine acetate) manufactured by Kao Corporation;

[0079] 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 (grafted polymer), Solsperse 28000 (grafted polymer), Solsperse 32000 (grafted polymer), Solsperse 38500 (grafted polymer) manufactured by Lubrizol;

[0080] Nikkol T106 (polyoxyethylene sorbitan monooleate) and MYS-IEX (polyoxyethylene monostearate) manufactured by Nikko Chemicals;

[0081] EFKA-46, EFKA-47, EFKA-47EA, EFKA Polymer 100, EFKA Polymer 400, EFKA Polymer 401, EFKA Polymer 450 manufactured by Morishita Industries;

[0082] Disperse Aid 6, Disperse Aid 8, Disperse Aid 15, and Disperse Aid 9100 manufactured by SAN NOPCO.

[0083] In addition, as the dispersant, nonionic, anionic, or cationic surfactants can be used. These surfactants are available as commercial products.

[0084] Specific examples of commercially available surfactants include:

[0085] EFKA-745 manufactured by EFKA;

[0086] Organosiloxane polymer KP341 manufactured by Shin-Etsu Chemical Co., Ltd.;

[0087] Polyflow No.75, Polyflow No.90, Polyflow No.95 manufactured by Kyoeisha Oil and Fat Chemical Industry Co., Ltd.;

[0088] W001, W004, W005, and W017 manufactured by Yushang Company;

[0089] Solsperse 3000, Solsperse 5000, Solsperse 9000, Solsperse 12000, Solsperse 13240, Solsperse 13940, Solsperse 17000, Solsperse24000, Solsperse manufactured by Nippon Lubrizol 26000, Solsperse 28000;

[0090] ADEKA Pluronic (registered trademark, the same 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 manufactured by ADEKA Corporation;

[0091] ISONET S-20 manufactured by Sanyo Chemical Co.;

[0092] Hinoact T-8000E manufactured by Kawaken Fine Chemicals Co., Ltd.;

[0093] Manufacturer of ELEBASE BA-100, ELEBASE BA-200, ELEBASE BCP-2, ELEBASE BUB-3, ELEBASE BUB-4, ELEBASE E CP-800K, ELEBASE EDP-475, ELEBASE HEB-5, Finesurf 270, Finesurf 7045, Finesurf 7085, DSP-12.5, DT-03, L-205, LPE-1007, O-205 S-202, S-204, S-207, S-205T,

[0094] Manufacturers Emulgen A-500, Emulgen PP-290, Amiet 102, Amiet 105, Amiet302, Amiet 320, Aminon PK-02S, Emanon CH-25, Emulgen 104P、Emulgen 108、Emulgen404、Emulgen 408、Emulgen A-60、Emulgen A-90、Emulgen B-66、Emulgen LS-106、EmulgenLS-114、Rheodol 430V、Rheodol 440V、Rheodol 460V、Rheodol TW-S106、Rheodol TW-S120V、Rheodol Super TW-L120、Phosphanol ML-200、EMAL 20T、EMAL E-27、Neo PelexGS、P elex NBL、Pelex SS-H, Pelex SS-L, Poiz 532A, LATEMUL ASK, LATEMUL E-118B, LATEMUL E-150.

[0095] Manufacturers of Newcalgen 3000S, Newcalgen FS-3PG, Ne wcalgen FE-7PG, PIONIN D-6414, PIONIN A-24-EA, PIONIN A-28-B, PIONIN A-29-M, PIONIN A-44-B, PIONEER-44TW.

[0096] Dynol 604, Olfine PD-002W, Surfynol 2502, Surfynol 440, Surfynol 465, Surfynol 485, Surfynol 61 manufactured by Nissin Chemical Industry Co., Ltd.

[0097] EMULSOGEN COL-020, EMULSOGEN 070, EMULSOGEN 080, made by Clariant

[0098] Plysurf A208B, Plysurf A210B, Plysur f A210G, Plysurf A219B, Plysurf AL, and LAVELIN FC-45 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0099] AKYPO RLM100NV, AKYP O RLM45, AKYPORLM45NV, AKYPO ECT-3, AKYPO ECT-3NEX, AKYPO ECT-7, Hosuten HLP, Hosuten HLP-1, Hosuten H LP-TEA made by Nihon Surfactant Kogyo KK.

[0100] These dispersants may be used alone or in combination of two or more.

[0101] 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 relative to 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, relative to the mass of the hollow filler.

[0102] The amount of the hollow filler (A) used in the curable resin composition is not particularly limited within the range that does not hinder the purpose of the present invention. The content of the hollow filler (A) in the curable composition is preferably 80% by mass or less, more preferably 20 to 80% by mass, and particularly preferably 30 to 70% by mass, relative to the mass of the curable composition excluding the mass of the organic solvent (S) described later.

[0103] <Polymerizable Compound (B)>

[0104] The curable resin composition contains a polymerizable compound (B). 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.

[0105] Examples of the polymerizable functional group include ethylenically unsaturated groups and examples of the ethylenically unsaturated group include (meth)acryloyl groups.

[0106] (Compound (B1) having 5 or more polymerizable functional groups)

[0107] The number of polymerizable functional groups in the compound (B1) is 5 or more, preferably 5 to 10, more preferably 5 or 6.

[0108] The compound (B1) may be used in combination of two or more types.

[0109] As the compound (B1), a compound represented by the following formula (b1) is preferred.

[0110] (MA-(OR 11 -(CO) n13 ) n12 -X) n11 -A-((X) n15 -R 12 ) n14 ···(b1)

[0111] (In formula (b1), A is a hexavalent organic group, MA is independently a (meth)acryloyl group, X is independently an oxygen atom, -NH-, or -N(CH3)-, R 11 Each independently represents 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.)

[0112] The number of carbon atoms of the hexavalent organic group as A is preferably 2 to 20, more preferably 6 to 15, and even more preferably 10 to 12.

[0113] As for the hexavalent organic group as A, there can be mentioned an aliphatic hydrocarbon group; an aromatic hydrocarbon group; a heterocyclic group; 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 connecting group; etc. Among them, an aliphatic hydrocarbon group and a group in which two or more aliphatic hydrocarbon groups are bonded via a divalent connecting group are preferred, and a group in which two or more aliphatic hydrocarbon groups are bonded via a divalent connecting group is more preferred.

[0114] Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing a ring in the structure, etc. Among them, a linear or branched aliphatic hydrocarbon group is preferred, and a linear or branched saturated aliphatic hydrocarbon group is more preferred.

[0115] Examples of the divalent linking group include -CONH-, -NH-, -N=N-, -CH=N-, -COO-, -O-, -CO-, -SO-, -SO2-, -S-, and -SS-. Among them, -O- is preferred.

[0116] As the hexavalent organic group as A, groups having the following structures and the like are exemplified.

[0117] [Chemical formula 1]

[0118]

[0119] X is preferably an oxygen atom.

[0120] As R 11 The number of carbon atoms in the alkylene group is preferably 1 or more and 5 or less, more preferably 2 or 3.

[0121] About R 11 The alkylene group having 1 to 10 carbon atoms includes ethane-1,2-diyl, propane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, and propane-1,5-diyl. Among them, ethane-1,2-diyl, propane-1,2-diyl, and propane-1,3-diyl are preferred.

[0122] About R 12 The alkyl group having 1 to 4 carbon atoms includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl. Among these alkyl groups, methyl and ethyl are preferred.

[0123] As R 12 The acyl group preferably has 1 to 3 carbon atoms.

[0124] About R 12The acyl group having 1 to 4 carbon atoms includes a group represented by -COR (R is a linear or branched alkyl group) and the like.

[0125] As R 12 , preferably a hydrogen atom or an acyl group having 1 to 4 carbon atoms.

[0126] n12 is preferably 0 to 5, more preferably 0 to 3, and even more preferably 0.

[0127] n13 is preferably 0.

[0128] n15 is preferably 1.

[0129] 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 Yakuin Kogyo Co., Ltd. Among them, dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate are more preferred.

[0130] (Compound (B2) Having 1 or More and 3 or Less Polymerizable Functional Groups)

[0131] The number of polymerizable functional groups in the compound (B2) is 1 or more and 3 or less, and preferably 3.

[0132] The compound (B2) may be used in combination of two or more types.

[0133] Examples of the compound (B2) having one polymerizable functional group include (meth)acrylamide, hydroxymethyl (meth)acrylamide, methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, butoxymethoxymethyl (meth)acrylamide, N-hydroxymethyl (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-butylacrylamidesulfonic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, Ester, 2-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, glycerol 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, (meth)acrylic acid half ester of phthalic acid derivatives, isobornyl (meth)acrylate, and the like.

[0134] 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, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, alkylene oxide-modified trimethylolpropane tri(meth)acrylate, glycerol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate. Ester, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, (meth)acrylate 2-hydroxy-3-(meth)acryloxypropyl, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ether di(meth)acrylate, glycerol tri(meth)acrylate, 1,3,5-tri(meth)acryloylhexahydro-1,3,5-triazine (tri(meth)acrylformal), tricyclodecane dimethanol di(meth)acrylate, etc.

[0135] As the compound (B2), a compound represented by the following formula (b2-1) or (b2-2) is preferred.

[0136] (MA-(OR 21 -(CO) n22 ) n21 -X-CH2)3-C-CH2-R 22 ···(b2-1)

[0137] (MA-(OR 21 -(CO) n22 ) n21 -X-CH2)2-CH-X-((CO) n22 -R 21 -O) n21 -MA···(b2-2)

[0138] (In formula (b2-1) and formula (b2-2), MA is independently a (meth)acryloyl group, X is independently an oxygen atom, -NH-, or -N(CH3)-, and R 21 Each independently represents 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, n21 is each independently an integer of 0 to 10, and n22 is each independently 0 or 1.

[0139] X is preferably an oxygen atom.

[0140] As R 21 The number of carbon atoms in the alkylene group is preferably 1 or more and 5 or less, more preferably 2 or 3.

[0141] About R 21 The alkylene group having 1 to 10 carbon atoms includes ethane-1,2-diyl, propane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, and propane-1,5-diyl. Among them, ethane-1,2-diyl, propane-1,2-diyl, and propane-1,3-diyl are preferred.

[0142] About R 22 The alkyl group having 1 to 4 carbon atoms includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl. Among these alkyl groups, methyl and ethyl are preferred.

[0143] n21 is preferably 0 to 5, and more preferably 1 to 3.

[0144] n22 is preferably 0.

[0145] 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, glycerol tri(meth)acrylate, alkylene oxide-modified glycerol tri(meth)acrylate, caprolactone-modified glycerol tri(meth)acrylate, etc. Among them, alkylene oxide-modified trimethylolpropane tri(meth)acrylate is more preferred.

[0146] The mass ratio of compound (B1) to compound (B2) (B1 / B2) is 0.25 to 3, preferably 1.1 to 2.5, and more preferably 1.25 to 2. When the ratio is 0.25 to 3, a cured film having excellent heat resistance can be formed.

[0147] 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, further preferably 95% by mass or more, and may be 100% by mass.

[0148] The content of the polymerizable compound (B) is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, based on the mass of the curable composition excluding the mass of the organic solvent (S) described below.

[0149] <Polymerization Initiator (C)>

[0150] The curable composition contains a polymerization initiator (C).

[0151] The polymerization initiator (C) is not particularly limited, and conventionally known photopolymerization initiators, thermal polymerization initiators, etc. can be used. Among them, photopolymerization initiators are preferred. The polymerization initiators can be used alone or in combination of two or more.

[0152] The photopolymerization initiator is not particularly limited, and a conventionally known photopolymerization initiator can be used.

[0153] Specific examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropane-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, bis(4-dimethylaminophenyl)ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butane-1-one, O-acetyl -1-[6-(2-methylbenzoyl)-9-ethyl-9H-carbazole-3-yl]ethanone oxime, O-acetyl-1-[6-(pyrrol-2-ylcarbonyl)-9-ethyl-9H-carbazole-3-yl]ethanone oxime, (9-ethyl-6-nitro-9H-carbazole-3-yl)[4-(2-methoxy-1-methylethoxy)-2-methylphenyl]methanone O-acetyl oxime, 2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]-1-octanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 4-benzoyl-4'-methyldimethyl sulfide, 4-dimethylaminobenzoic acid, 4-dimethylaminobenzoic acid methyl ester, 4-dimethylaminobenzoic acid ethyl ester, 4-dimethylaminobenzoic acid butyl ester, 4-dimethylamino-2-ethylhexyl benzoic acid, 4-dimethylamino-2-isoamyl benzoic acid, benzyl-β-methoxyacetal, benzyl dimethyl ketal, 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime, methyl o-benzoylbenzoate, 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-mercapto Benzothiazole, 2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl)-imidazolyl dimer, benzophenone, 2-chlorobenzophenone, 4,4'-bisdimethylaminobenzophenone, 4,4'-bisdiethylaminobenzophenone, 4,4'-dichlorobenzophenone, 3,3-dimethyl-4-methoxybenzophenone, 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-dimethylaminoacetophenone, dichloroacetophenone, trichloroacetophenone, p-tert-butylacetophenone, p-dimethylaminoacetophenone, p-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, α,α-Dichloro-4-phenoxyacetophenone, thioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, dibenzosuberone, 4-dimethylaminobenzoic acid pentyl ester, 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)vinyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(furan-2-yl)vinyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(4-diethylamino-2-methylphenyl)vinyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2,

[0154]

[0043] -(3,4-dimethoxyphenyl)vinyl]-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-ethoxyphenyl)-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)phenylphenyl-s-triazine, 2,4-bis(trichloromethyl)-6-(2-bromo-4-methoxy)phenylphenyl-s-triazine, etc. These photopolymerization initiators may be used alone or in combination of two or more.

[0155] The thermal polymerization initiator is not particularly limited, and a conventionally known thermal polymerization initiator can be used.

[0156] Specific examples of the thermal polymerization initiator include ketone peroxides (methyl ethyl ketone peroxide and cyclohexanone peroxide, etc.), peroxy ketals (2,2-bis(tert-butylperoxy)butane and 1,1-bis(tert-butylperoxy)cyclohexane, etc.), hydroperoxides (tert-butyl hydroperoxide and 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 and benzoyl peroxide, etc.), peroxydicarbonates (diisopropyl peroxydicarbonate, etc.), peroxyesters (tert-butyl peroxyisobutyrate and 2,5-dimethyl-2,5-di(phenylene)carbonate, etc.), and the like. The thermal polymerization initiator may be an organic peroxide such as cyclohexane (formyl peroxide) or the like, 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, 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 2,2'-azobis(2-methylpropionic acid) dimethyl ester. These thermal polymerization initiators may be used alone or in combination of two or more.

[0157] The content of the polymerization initiator (C) is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, relative to the mass of the curable composition excluding the mass of the organic solvent (S) described below. By making the content of the polymerization initiator (C) within the above range, a curable composition with good curability can be obtained.

[0158] <Surfactant (D)>

[0159] The curable composition preferably contains a surfactant (D).

[0160] As surfactant (D), any surfactant among nonionic surfactant, cationic surfactant, anionic surfactant and amphoteric surfactant can be used. Surfactant (D) can be fluorine-based surfactant, silicon-based surfactant, etc. As surfactant (D), fluorine-based surfactant, silicon-based surfactant, more preferably silicon-based surfactant. Two or more surfactants (D) can be used in combination.

[0161] The fluorine-based surfactant is not particularly limited as long as it is a surfactant containing a fluorine atom, and may be any of anionic surfactants, cationic surfactants, and nonionic surfactants.

[0162] Two or more fluorine-based surfactants may be used in combination.

[0163] Specific examples of the fluorine-based surfactant include BM-1000, BM-1100 (all manufactured by BM CHEMI), MEGAFACE F142D, MEGAFACE F172, MEGAFACE F173, MEGAFACE F183 (all manufactured by Dainippon Ink & Chemicals Co., Ltd.), Fluorad FC-135, Fluorad FC-170C, Fluorad FC-430, Fluorad FC-431 (all manufactured by Sumitomo 3M Ltd.), 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, SF-8428 (all manufactured by Toray Silicone Co., Ltd.) and other commercially available fluorine-based surfactants, but not limited thereto.

[0164] Furthermore, as the fluorine-based surfactant, a compound having a fluoroalkyl group in a side chain is also preferred.

[0165] Examples of the compound having a fluoroalkyl group in a side chain include compounds represented by the following formulae (e-1) to (e-4).

[0166] In formula (e-1) and formula (e-2), x1 is an integer of 0-7.

[0167] In formula (e-3), x2 is an integer of 0 to 8. In formula (e-4), x3 is an integer of 6 to 20.

[0168] [Chemical formula 2]

[0169]

[0170] [Chemical formula 3]

[0171]

[0172] [Chemical formula 4]

[0173]

[0174] As the silicon-based surfactant, a polysiloxane-based surfactant is preferred.

[0175] Silicon-based surfactants are surfactants containing silicon atoms. Polysiloxane-based surfactants are surfactants having a main chain formed by repeated Si-O bonds.

[0176] Examples of the polysiloxane-based surfactant include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, and aralkyl-modified polymethylalkylsiloxane.

[0177] The polysiloxane-based surfactant is available as a commercial item, and examples thereof include BYK-331, BYK-310, and BYK-322 manufactured by BYK Chemie Japan KK; and TEGO Glide 440 manufactured by Evonik.

[0178] The content of the surfactant (D) is preferably 0.001 to 3% by mass, more preferably 0.001 to 2% by mass, further preferably 0.001 to 1.5% by mass, and most preferably 0.001 to 1% by mass, relative to the total mass of the hollow filler (A) and the polymerizable compound (B) in the curable composition.

[0179] <Alkali-soluble resin>

[0180] The curable composition does not contain an alkali-soluble resin.

[0181] In this specification, the so-called alkali-soluble resin refers to the following resin: a resin film with a thickness of 1 μm is formed on a substrate using a resin solution with a resin concentration of 20 mass% (solvent: propylene glycol monomethyl ether acetate), and the resin is dissolved in an amount with a film thickness of 0.01 μm or more when immersed in a tetramethylammonium hydroxide (TMAH) aqueous solution with a concentration of 0.05 mass% for 1 minute.

[0182] Examples of such alkali-soluble resins include alkali-soluble resins blended in various compositions used in processes including development with an alkali developer.

[0183] <Organic Solvent (S)>

[0184] The curable composition preferably contains an organic solvent (S) for the purpose of improving coating properties and adjusting viscosity.

[0185] Specific examples of the organic solvent (S) include alkane monoalcohols 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 (Poly) alkylene glycol monoalkyl ethers such as mono-n-butyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol monoethyl ether; (Poly) alkylene glycol monoalkyl ether acetates 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), and propylene glycol monoethyl ether acetate; other ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, and tetrahydrofuran; ketones such as methyl ethyl ketone, cyclohexanone, 2-heptanone, and 3-heptanone; 2-hydroxy Lactic acid alkyl esters such as methyl propionate and ethyl 2-hydroxypropionate; ethyl 2-hydroxy-2-methylpropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutyrate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutyl propionate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl formate, isopentyl acetate, benzyl acetate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, Isopropyl butyrate, n-butyl butyrate, methyl pyruvate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, ethyl 2-oxobutyrate, 1,4-butanediol diacetate and other esters; 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-dimethylisobutyramide, N,N-diethylacetamide, N,N-diethylformamide, N-methylcaprolactam, 1,3-dimethyl-2-imidazolidinone, pyridine, and N,N,N',N'-tetramethylurea; etc.

[0186] Among them, 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.

[0187] In addition, the organic solvent (S) preferably contains a nitrogen-containing polar organic solvent from the viewpoint of solubility of each component, etc. As the nitrogen-containing polar organic solvent, N,N,N',N'-tetramethylurea and the like can be used.

[0188] These solvents can be used alone or in combination of two or more.

[0189] The content of the organic solvent (S) is not particularly limited and can be appropriately set according to the coating film thickness within a concentration that can be applied 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 further preferably 1 to 30 cp. In addition, the solid content concentration of the curable composition is preferably 1 to 50% by mass, more preferably 1 to 20% by mass.

[0190] <Other ingredients>

[0191] The curable composition may contain additives such as a photoacid generator, an adhesion enhancer, a thermal polymerization inhibitor, a defoaming agent, a colorant, and a silane coupling agent as necessary. As any of the additives, conventionally known additives may be used.

[0192] The curable composition preferably contains a silane coupling agent from the viewpoint of easily forming a low refractive index film having a good shape and excellent adhesion to a substrate. As the silane coupling agent, a conventionally known silane coupling agent can be used without particular limitation.

[0193] 《Method for producing low refractive index film》

[0194] As the 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 adopted without particular limitation.

[0195] As a preferred method for producing a low refractive index film, there can be mentioned a method comprising the following steps:

[0196] a step of forming a coating film of the curable composition; and

[0197] The step of curing the coating film.

[0198] In order to form a low refractive index film using a curable composition, first, the curable composition is applied on a substrate selected according to the application of the low refractive index film to form a coating film.

[0199] When forming an image sensor, for example, a substrate having RGB colored films on a semiconductor layer such as silicon and a microlens on the colored films can be used as the substrate.

[0200] The method for forming the coating film is not particularly limited, and the coating film can be formed using, for example, a contact transfer coating device such as a roll coater, a reverse coater, and a rod coater, a spin coater (spin coater, a rotary coating device), a dip coater, a spray coater, a slit coater, a curtain coating flow coater, and other non-contact coating devices. Among them, the spin coating method using a spin coater, the spray coating method using a spray coater, the slit coating method using a slit coater, the rod coating method using a rod coater, and the dip coating method using a dip coater are preferred.

[0201] The applied curable composition is dried as needed to form a coating film. The drying method is not particularly limited, and examples thereof include: method (1), drying at 80 to 120°C, preferably 90 to 100°C, for 60 to 120 seconds using a hot plate; method (2), leaving it at room temperature for several hours to several days; method (3), placing it in a hot air heater or infrared heater for tens of minutes to several hours to remove the solvent; and the like.

[0202] Next, the coating film is cured. The curing method is not particularly limited, and may be exposure, heating, or a combination of exposure and heating. Among them, curing is preferably performed by exposure. Exposure is performed by irradiating active energy rays such as ultraviolet rays, excimer lasers, etc.

[0203] Next, the cured film may be baked (post-baked). The baking temperature is not particularly limited, but is preferably 180 to 250° C., more preferably 220 to 230° C. Typically, the baking time is 10 to 90 minutes, preferably 20 to 60 minutes.

[0204] 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.

[0205] The low refractive index film can be preferably used in optical devices such as image sensors. In an image sensor, when the low refractive index film is used as a coating layer for a microlens formed on an RGB color film, light incident on the microlens can be fully reflected, thereby suppressing the generation of flare in the image sensor.

[0206] The above-mentioned curable composition can form a cured film having excellent heat resistance, and therefore can be used for the production of optical devices requiring a heat treatment process such as reflow soldering or post-baking.

[0207] Example

[0208] The present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0209] [Examples 1 to 8 and Comparative Examples 1 to 6]

[0210] The following hollow filler (A) in the amount described in Table 1, the polymerizable compound (B) in the type and amount described in Table 1, the following polymerization initiator (C) in the amount described in Table 1, and 0.01 parts by mass of the following surfactant (D) of the type described in Table 1 were mixed in the following organic solvent (S) so that the solid content concentration became 31% by mass, to obtain the curable resin composition of each Example and Comparative Example.

[0211] As the hollow filler (component (A)), THRULYA 4330 (product name, manufactured by JGC Catalysts & Chemicals Co., Ltd., a dispersion of hollow silica particles having an average primary particle size of 60 nm and a solid content concentration of 30% by mass) was used.

[0212] As the polymerizable compound (component (B)), the following B1 to B4 were used.

[0213] B1: KAYARAD DPHA (product name, manufactured by Nippon Kayaku Co., Ltd., a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate)

[0214] B2: M-360 (product name, manufactured by Toagosei Co., Ltd., trimethylolpropane EO-modified triacrylate represented by the following formula, n≈2)

[0215] [CH2=CHCO-(OC2H4) n -OCH2]3-CCH2CH3

[0216] B3: NK ester A-DCP (product name, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., tricyclodecane dimethanol diacrylate)

[0217] B4: LIGHT ESTER IB-X (product name, manufactured by Kyoeisha Chemical Co., Ltd., isobornyl methacrylate)

[0218] As the polymerization initiator (component (C)), 1-hydroxycyclohexyl phenyl ketone was used.

[0219] As surfactants (component (D)), the following D1 to D3 were used.

[0220] D1: PF-656 (product name, manufactured by Omnova, fluorine-based surfactant represented by the following formula)

[0221] [Chemical formula 5]

[0222]

[0223] D2: BYK-310 (product name, manufactured by BYK Chemie Japan KK, polyester-modified polydimethylsiloxane, silicone-based surfactant)

[0224] D3: TEGO Glide 440 (product name, manufactured by Evonik, polyether-modified polysiloxane copolymer, silicone-based surfactant)

[0225] Propylene glycol monomethyl ether was used as the organic solvent (component (S)).

[0226] 〔evaluate〕

[0227] The curable resin compositions of the Examples and Comparative Examples were used to evaluate the appearance, refractive index, and heat resistance according to the following methods.

[0228] (Appearance)

[0229] The curable resin composition of each example and comparative example was applied to a glass substrate using a spin coater (MS-B200 manufactured by MIKASA Co., Ltd.) so that the coating thickness was 3000 nm. The formed coating film was heated (prebaked) at 100°C for 1 minute and then exposed to light at 1 J / cm2 using an exposure device (imprint device ST-200 manufactured by Shibaura Machine Co., Ltd.). 2 The cured film was exposed (under a vacuum atmosphere of 200 Pa) and evaluated as "A" if the appearance of the obtained cured film was colorless and transparent, and evaluated as "B" if the appearance was turbid.

[0230] (Refractive Index)

[0231] The curable resin composition of each example and comparative example was applied to a silicon substrate using a spin coater (MS-B200 manufactured by MIKASA Co., Ltd.) so that the coating thickness was 1000 nm. The formed coating film was heated (prebaked) at 100°C for 1 minute and then exposed to light at 1 J / cm2 using an exposure device (imprint device ST-200 manufactured by Shibaura Machine Co., Ltd.). 2 The cured film was obtained by exposure (vacuum 200 Pa atmosphere). The refractive index of the obtained cured film was measured using a refractive index measuring device (spectroscopic ellipsometer M-2000 manufactured by JA Woollam).

[0232] (Heat resistance)

[0233] The film thickness of the cured film obtained in the appearance evaluation was measured. The operation of heating the cured film at 260°C for 10 seconds was repeated three times, and the film thickness of the cured film after heating was measured. The film thickness change rate before and after heating was calculated based on the following formula, and the case where the film thickness change rate was 1% or less was evaluated as "A", the case where the film thickness change rate was greater than 1% and less than 2% was evaluated as "B", and the case where the film thickness change rate was greater than 2% was evaluated as "C".

[0234] Film thickness change rate (%) = (|film thickness before heating - film thickness after heating| / film thickness before heating) × 100

[0235] [Table 1]

[0236]

[0237] 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) but 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 or more and 3 or less 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 or more and 3 or less, a cured film with excellent heat resistance can be formed. On the other hand, it is known that 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 or more and 3 or less polymerizable functional groups, and the ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is not 0.25 or more and 3 or less, a cured film with poor heat resistance is formed.

Claims

1. A curable composition for forming a low refractive index film, comprising a hollow filler (A), a polymerizable compound (B) and a polymerization initiator (C) but not 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 ratio (B1 / B2) of the mass of the compound (B1) to the mass of the compound (B2) is 0.25 to 3.

2. The curable composition for forming a low refractive index film according to claim 1, wherein The compound (B1) is a compound having 5 or 6 polymerizable functional groups, 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 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. 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) includes 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 formed of a cured product of the curable composition for forming a low-refractive-index film according to claim 1 .

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

9. A method for producing a low refractive index film, comprising the following steps: 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 A step of 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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