Photocurable resin composition, cured product thereof, and electronic circuit board provided with cured product

Abstract

To provide a photopolymerizable resin composition that enables formation of a matte cured product while having a composition suitable for inkjet printing.SOLUTION: A photocurable resin composition used for inkjet printing, comprises a (meth)acrylate, a photoradical polymerization initiator, at least one of melamine and melamine resin, an epoxy resin and a photoacid generator, the (meth)acrylate and the epoxy resin being contained at a ratio of 3:1 to 15:1 on a mass basis.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable resin composition, and more particularly to a photocurable resin composition suitable for forming a cured product by inkjet printing, a cured product thereof, and an electronic circuit board provided with a coating made of the cured product. [Background technology]

[0002] In the production of electronic circuit boards such as printed wiring boards, curable resin compositions are used to form solder resists, markings, etc. Curable resin compositions used for such purposes are required to have various properties such as solder heat resistance and adhesion to insulating substrates or conductor layers, as well as the design and productivity of the cured product (i.e., the form of the solder resist or marking).For example, curable resin compositions capable of forming matte cured products have been proposed.

[0003] Conventionally, cured products have been formed by forming a coating film by a method such as screen printing, followed by exposure and development processes. However, in recent years, the development process has been omitted by forming the product by inkjet printing. In order to apply inkjet printing, it is necessary to reduce the viscosity of the curable resin composition compared to coating methods such as screen printing, so the composition is designed to avoid the use of high-molecular-weight polymers. For example, Patent Document 1 proposes a photocurable resin composition containing multiple types of (meth)acrylates and a photoradical polymerization initiator. Patent Document 2 also proposes a photocurable resin composition containing a cationically polymerizable compound such as an epoxy resin and a photoacid generator as a curable ink for inkjet printing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-115297 [Patent Document 2] Japanese Patent Application Publication No. 2019-172838 Summary of the Invention

[0005] The photocurable resin compositions described in Patent Documents 1 and 2 as mentioned above have high surface gloss when cured. While inorganic fillers and the like have traditionally been added to curable resin compositions to produce matte cured products, the viscosity of the photocurable resin composition increases as the amount of inorganic filler added increases. Furthermore, adding inorganic fillers to the photocurable resin composition can increase the average particle size of the photocurable resin composition and the viscosity of the photocurable resin composition, potentially resulting in printing defects. Therefore, there is a demand for a photocurable resin composition that is suitable for inkjet printing and can produce matte cured products.

[0006] Therefore, an object of the present invention is to provide a photocurable resin composition that is suitable for inkjet printing, yet can produce a matte cured coating and has good adhesion to dissimilar materials. Another object of the present invention is to provide a cured product of the photocurable resin composition and an electronic circuit board comprising the cured product.

[0007] The present inventors have discovered that by combining two polymerization species, a radical polymerizable monomer and a cationically polymerizable monomer, and utilizing the difference in curing speed between the two, a cured product having a matte surface can be obtained without using a filler such as an inorganic filler. They have also discovered that by further adding at least one of melamine and a melamine resin to the two types of radical polymerizable monomer and cationically polymerizable monomer, a matte cured product with reduced surface gloss can be obtained. The present invention is based on this discovery. Specifically, the gist of the present invention is as follows.

[0008] That is, the gist of the present invention is as follows. [1] A photocurable resin composition comprising: a (meth)acrylate; a photoradical polymerization initiator; at least one of melamine and a melamine resin; an epoxy resin; and a photoacid generator, wherein the (meth)acrylate and the epoxy resin are contained in a ratio of 3:1 to 15:1 by mass. [2] The photocurable resin composition according to [1], which has a viscosity at 25°C of 10 to 35 mPa·s. [3] The photocurable resin composition according to [1] or [2], wherein the epoxy resin comprises an epoxy resin that is liquid at room temperature. [4] The photocurable resin composition according to [2], wherein the epoxy resin that is liquid at room temperature contains a bisphenol A type epoxy resin. [5] The photocurable resin composition according to [4], wherein the bisphenol A epoxy resin has a viscosity of 15,000 mPa·s or less at 25°C. [6] The photocurable resin composition according to any one of [1] to [5], wherein the total amount of the (meth)acrylate and the epoxy resin is 80 mass % or more, calculated as solid content, based on the total amount of the photocurable resin composition. [7] The photocurable resin composition according to any one of [1] to [6], wherein at least one of the melamine and the melamine resin has an average particle size (D50) of 0.1 to 1 μm. [8] The photocurable resin composition according to any one of [1] to [7], wherein the total amount of the melamine and the melamine resin is 1 to 10 mass % in terms of solid content based on the total mass of the photocurable resin composition. [9] The photocurable resin composition according to any one of [1] to [8], wherein the (meth)acrylate has at least one cationically polymerizable functional group selected from the group consisting of a vinyl ether group, an epoxy group, a thioether group, a trioxane group, and an oxetane group.

[10] The particle size distribution (D 50 ) is 0.4 μm or less.

[11] The particle size distribution (D 100) is 1 μm or less.

[12] The photocurable resin composition according to any one of [1] to

[11] , which is used for inkjet printing.

[13] A cured product of the photocurable resin composition according to any one of [1] to

[12] .

[14] An electronic circuit board comprising the cured product according to

[13] .

[0009] The photocurable resin composition of the present invention can provide a photopolymerizable resin composition that is suitable for inkjet printing and yet can produce a matte cured product. Furthermore, the matte interface of the cured product provides excellent adhesion to different components, such as circuit boards. Furthermore, a cured product of the photocurable resin composition and an electronic circuit board including the cured product can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Definition] In this specification, "light" refers to active energy rays such as visible light, ultraviolet light, infrared light, X-rays, α-rays, β-rays, γ-rays, and i-rays. In this specification, the term "(meth)acrylate" is a general term for acrylate, methacrylate and mixtures thereof, and the same applies to other similar expressions. In addition, in this specification, "liquid" refers to a liquid state that has fluidity at 20°C, and includes not only a liquid state but also a semi-liquid state (paste state). Each component will be described in detail below.

[0011] [Photocurable resin composition] The photocurable resin composition according to the present invention contains, as essential components, a (meth)acrylate, a photoradical polymerization initiator, at least one of melamine and a melamine resin, an epoxy resin, and a photoacid generator. According to the present invention, by including at least one of melamine and a melamine resin in addition to a (meth)acrylate and an epoxy resin, a photocurable resin composition that is suitable for inkjet printing yet produces a matte cured product can be realized. The reason for this is unclear, but can be presumed as follows. Specifically, when the photocurable resin composition according to the present invention is cured by irradiation with light, radicals generated from the photoradical polymerization initiator promote the curing reaction of the (meth)acrylate, and acid generated from the photoacid generator promotes the curing reaction of the epoxy resin. However, the presence of at least one of melamine and a melamine resin slows down the curing reaction of the epoxy resin because the acid generated from the photoacid generator is captured by nitrogen atoms contained in the at least one of melamine and a melamine resin. Therefore, there is a difference in the curing speed between the (meth)acrylate and the epoxy resin, and the polymerized (meth)acrylate is dispersed in the still liquid epoxy resin before both are completely cured. As a result, it can be assumed that a cured product with an uneven surface morphology and a matte cured product with reduced gloss is obtained. However, this is merely speculation and is not intended to be limiting. Below, each component constituting the photocurable resin composition according to the present invention will be described.

[0012] <(Meth)acrylate> As the (meth)acrylate, any commonly known (meth)acrylate can be used without limitation as long as it is polymerizable by radicals generated from a photoradical polymerization initiator. Examples of the commonly known (meth)acrylate include polyester (meth)acrylate, polyether (meth)acrylate, urethane (meth)acrylate, carbonate (meth)acrylate, and epoxy (meth)acrylate. Specific examples include hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; glycol diacrylates such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, and N,N-dimethylaminopropylacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; hexanediol, trimethylolpropane, pentaerythritol, diacrylates of ... Polyhydric acrylates such as polyhydric alcohols such as pentaerythritol and tris-hydroxyethyl isocyanurate, or their ethylene oxide adducts, propylene oxide adducts, or ε-caprolactone adducts; polyhydric acrylates such as phenoxy acrylate, bisphenol A diacrylate, and ethylene oxide adducts or propylene oxide adducts of these phenols; polyhydric acrylates of glycidyl ethers such as glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; and at least one of the following may be appropriately selected and used: acrylates obtained by directly acridating polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadienes, and polyester polyols, or urethane acrylates obtained by using diisocyanates; and melamine acrylates, as well as methacrylates corresponding to the above acrylates.

[0013] In addition to the above-mentioned (meth)acrylates, (meth)acrylates having one or more cationically polymerizable functional groups such as a vinyl ether group, an epoxy group, a thioether group, a trioxane group, or an oxetane group can also be suitably used in the present invention.

[0014] Among the above, in consideration of suitability for inkjet printing, liquid (meth)acrylates having a viscosity at 25°C in the range of 10 to 35 mPa·s, preferably 10 to 20 mPa·s, can be suitably used. Specifically, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, glycerin di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexamethylpropional ... Nonanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, EO adduct di(meth)acrylate of bisphenol A, EO adduct di(meth)acrylate of bisphenol F, PO adduct di(meth)acrylate of bisphenol A, cyclohexanedimethanol di(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, dicyclohexane Bifunctional monomers such as cyclohexanedimethanol divinyl ether, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, ditrimethylol Propane tetra(meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 3,3,5-trimethylcyclohexyl acrylate, adamantyl acrylate,2-Methyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl acrylate, 2-isopropyl-2-adamantyl acrylate, 1-(1-adamantyl)-1-methylethyl acrylate, 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate propyl, 2-methyl-3-vinyloxypropyl (meth)acrylate, 1,1-dimethyl-2-vinyloxyethyl (meth)acrylate, 3-vinyloxybutyl (meth)acrylate, 1-methyl-2-vinyloxypropyl (meth)acrylate, 2-vinyloxybutyl (meth)acrylate, 4-vinyloxycyclohexyl (meth)acrylate, 6-vinyloxyhexyl (meth)acrylate, 4-vinyloxymethylcyclohexylmethyl (meth)acrylate, 3-vinyloxymethylcyclohexylmethyl (meth)acrylate, 2-vinyloxymethyl (meth)acrylate ethylcyclohexylmethyl, p-vinyloxymethylphenylmethyl (meth)acrylate, m-vinyloxymethylphenylmethyl (meth)acrylate, o-vinyloxymethylphenylmethyl (meth)acrylate, 2-(vinyloxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxy)propyl (meth)acrylate, 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyl) (meth)acrylate 2-(vinyloxyisopropoxy)isopropyl, (meth)acrylate 2-(vinyloxyethoxyethoxy)ethyl, (meth)acrylate 2-(vinyloxyethoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyethoxyethoxy)propyl, (meth)acrylate 2-(vinyloxyethoxyisopropoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)propyl,2-(vinyloxyisopropoxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyethoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxy Examples of (meth)acrylates include 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, polyethylene glycol monovinyl ether (meth)acrylate, and polypropylene glycol monovinyl ether (meth)acrylate. These (meth)acrylates may be used alone or in combination of two or more.

[0015] In consideration of solder heat resistance, adhesion to an insulating substrate or a conductor layer, solvent resistance, inkjet printability, and the like, the (meth)acrylate is contained in the photocurable resin composition in an amount of preferably 60 to 90 mass %, more preferably 60 to 80 mass %.

[0016] Furthermore, from the viewpoint of inkjet printability and obtaining a matte cured product, the (meth)acrylate is preferably blended so that the blending ratio of the (meth)acrylate to the epoxy resin described below is 3:1 to 15:1 by mass, and more preferably 5:1 to 10:1.

[0017] <Photoradical polymerization initiator> The photoradical polymerization initiator is a compound that generates radicals upon irradiation with light in order to radically addi tion polymerize the above-mentioned (meth)acrylate, and any commonly used and knoWn photoradical polymerization initiator can be used Without limitation. Specifically, α-aminoacetophenone-based photoradical polymerization initiators such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and N,N-dimethylaminoacetophenone; hydroxyacetophenone-based photoradical polymerization initiators such as 1-hydroxy-cyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, and 2-hydroxy-2-methyl-1-phenylpropan-1-one;Bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine Acylphosphine oxide-based photoradical polymerization initiators such as sphingoinoxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphinic acid methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphinic acid isopropyl ester, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; benzoin-based photoradical polymerization initiators such as benzoin, benzil, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether; benzoin alkyl ether-based photoradical polymerization initiators; benzophenone, p-methylbenzophenone, and Michler's ketone. Benzophenone-based photoradical polymerization initiators such as acetophenone, methylbenzophenone, 4,4'-dichlorobenzophenone, and 4,4'-bisdiethylaminobenzophenone; acetophenone-based photoradical polymerization initiators such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone;Thioxanthone-based photoradical polymerization initiators such as thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; anthraquinone-based photoradical polymerization initiators such as anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, and 2-aminoanthraquinone; ketal-based photoradical polymerization initiators such as acetophenone dimethyl ketal and benzil dimethyl ketal; ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethylbenzoate, and the like. Examples of such initiators include benzoic acid ester-based radical photopolymerization initiators such as benzoate and p-dimethylbenzoic acid ethyl ester; oxime ester-based radical photopolymerization initiators such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime); and titanocene-based radical photopolymerization initiators such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium and bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium.

[0018] Among the above, α-aminoacetophenone-based photoradical polymerization initiators and acylphosphine oxide-based photoradical polymerization initiators are preferred, and it is more preferred to use an acylphosphine oxide-based photoradical polymerization initiator. One type of photoradical polymerization initiator may be used alone, or two or more types may be used in combination.

[0019] Commercially available α-aminoacetophenone-based photoradical polymerization initiators include Omnirad 907, 369, 369E, and 379 manufactured by IGM Resins. Commercially available acylphosphine oxide-based photoradical polymerization initiators include Omnirad 819 manufactured by IGM Resins. Commercially available titanocene-based photoradical polymerization initiators include JMT-784 manufactured by Yueyang Kimoutain Sci-tech Co., Ltd. and GR-FMT manufactured by Hubei Kimoutain Sci-tech Co., Ltd.

[0020] Alternatively, a photoradical polymerization initiator having two oxime ester groups in the molecule may be used, and specific examples thereof include oxime ester compounds having a carbazole structure represented by the following general formula (I). [ka]

[0021] In the above formula, X represents a hydrogen atom, an alkyl group having 1 to 17 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a phenyl group, a phenyl group (substituted with an alkyl group having 1 to 17 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an amino group, an alkylamino group having an alkyl group of 1 to 8 carbon atoms, or a dialkylamino group), a naphthyl group (substituted with an alkyl group having 1 to 17 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an amino group, an alkylamino group having an alkyl group of 1 to 8 carbon atoms, or a dialkylamino group), and Y and Z each represent a hydrogen atom, an alkyl group having 1 to 17 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a halogen group, a phenyl group, a phenyl group (substituted with an alkyl group having 1 to 17 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a dialkylamino group). Ar represents an alkylene having 1 to 10 carbon atoms, vinylene, phenylene, biphenylene, pyridylene, naphthylene, thiophene, anthrylene, thienylene, furylene, 2,5-pyrrole-diyl, 4,4'-stilbene-diyl, or 4,2'-styrene-diyl; and n is an integer of 0 or 1.

[0022] In particular, an oxime ester-based photoradical polymerization initiator in which, in the above formula, X1 and Y1 are each a methyl group or an ethyl group, Z is methyl or phenyl, n is 0, and Ar is phenylene, naphthylene, thiophene, or thienylene is preferred.

[0023] In addition to the above-mentioned photoradical polymerization initiators, benzoin compounds, acetophenone compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, xanthone compounds, and the like can also be used as photoradical polymerization initiators. However, it is preferable to use these compounds as a photoradical polymerization initiator aid or sensitizer in combination with the above-mentioned photoradical polymerization initiator rather than using them alone as a photoradical polymerization initiator. Among the above, from the viewpoint of deep section curing, thioxanthone compounds and tertiary amine compounds are preferred, and thioxanthone compounds are more preferred. Two or more of the above compounds may also be used in combination.

[0024] The amount of the photoradical polymerization initiator is preferably 1 to 50 parts by mass, more preferably 1 to 20 parts by mass, based on 100 parts by mass of (meth)acrylate, calculated as solid content. When a benzoin compound or the like is contained as an auxiliary agent for the photoradical polymerization initiator, the amount is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, based on 100 parts by mass of (meth)acrylate, calculated as solid content.

[0025] <Melamine and melamine resins> The photocurable resin composition of the present invention contains at least one of melamine and a melamine resin. Because melamine and a melamine resin contain a nitrogen atom in the triazine skeleton, they have the effect of capturing the acid generated from the photoacid generator and delaying the curing reaction of the epoxy resin. As a result, when the photocurable resin composition of the present invention is irradiated with light, the curing reaction of the (meth)acrylate proceeds first, and the curing reaction of the epoxy resin is completed later. As a result, the surface of the cured product has a finely textured shape, imparting a suitable matte finish, without the composition substantially containing an inorganic filler.

[0026] The melamine resin contained in the photocurable resin composition of the present invention includes not only resins cured by addition condensation of melamine (2,4,6-triamino-1,3,5-triazine) and formaldehyde, but also methylol melamine, the initial reaction product of melamine and formaldehyde, and its alkylated product, alkylated methylol melamine. Melamine resins also include modified melamines such as methylated methylol melamine, propylated methylol melamine, butylated methylol melamine, and isobutylated methylol melamine. Melamine-modified products such as melamine (meth)acrylate are also included. Melamine and melamine resins may be mixtures of the above-mentioned melamine with other resins such as acrylic resins, epoxy resins, and alkyd resins. Examples include acrylic melamine, alkyd melamine, polyester melamine, and epoxy melamine. Among the above, melamine is more preferred due to its excellent solder heat resistance and adhesion to dissimilar components. These melamines and melamine resins may be used singly or in combination of two or more.

[0027] Particle size distribution D of the above melamine and melamine resin 50 (that is, the average particle size) is preferably 0.1 to 1 μm, more preferably 0.1 to 0.8 μm, further preferably 0.1 to 0.5 μm, and particularly preferably 0.1 to 0.3 μm.

[0028] Particle size distribution D 50 By containing melamine and melamine resins having a particle size distribution D in the above range, the inkjet printing properties are good and a suitable matte finish can be imparted to the surface of the cured product. 50 refers to the particle size when the cumulative percentage from the smallest particle size in the particle size distribution measurement results measured by laser diffraction method is 50%, and specifically, it can be measured by the method described below.

[0029] From the viewpoint of providing a matte finish to the cured product while satisfying inkjet printability, the total amount of melamine and melamine resin blended is preferably 1 to 10 parts by mass, and more preferably 3 to 7 parts by mass, calculated as solid content, based on the entire photocurable resin composition.

[0030] <Epoxy resin> The epoxy resin contained in the photocurable resin composition of the present invention can be any commonly known epoxy resin, without limitation, as long as it is polymerizable by an acid generated from a photoacid generator described below. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexanedimethanol type epoxy resins, glycidyl amine type epoxy resins, epoxy resins having a butadiene structure, bixylenol type epoxy resins, cresol novolac type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol type epoxy resins, biphenyl type epoxy resins, naphthylene ether type epoxy resins, anthracene type epoxy resins, and tetraphenylethane type epoxy resins.

[0031] Among the above, epoxy resins that are liquid at room temperature (25°C) are preferred for use in terms of inkjet printing suitability. Specific examples include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol AF epoxy resins, phenol novolac epoxy resins, tert-butyl-catechol epoxy resins, glycidylamine epoxy resins, aminophenol epoxy resins, and alicyclic epoxy resins. These epoxy resins may be used alone or in combination of two or more. Among these liquid epoxy resins, bisphenol A epoxy resins are preferred, and bisphenol A epoxy resins with a viscosity of 15,000 mPa·s or less at 25°C are particularly preferred.

[0032] In consideration of solder heat resistance, adhesion to the insulating substrate or conductor layer, solvent resistance, suitability for inkjet printing, etc., the epoxy resin is contained in the photocurable resin composition in an amount of preferably 5 to 40 mass %, and more preferably 10 to 25 mass %, converted into solid content.

[0033] Furthermore, from the viewpoint of obtaining a cured product with good adhesion to marking ink and a matte finish while satisfying suitability for inkjet printing, the total amount of the (meth)acrylate and the epoxy resin, converted into solid content, is preferably 80% by mass or more of the entire photocurable resin composition, more preferably 80% by mass or more and 95% by mass or less, and particularly preferably 80% by mass or more and 90% by mass or less.

[0034] To achieve inkjet printability while also achieving excellent adhesion to marking ink and a matte-finished cured product, the blending ratio of (meth)acrylate to epoxy resin is set to a range of 3:1 to 15:1 by mass. The curing reaction of (meth)acrylate is a radical polymerization reaction, resulting in a higher curing reaction rate than that of epoxy resin, which proceeds via cationic polymerization. Therefore, when the (meth)acrylate and epoxy resin are contained in an appropriate ratio, the curing rates of the respective components differ, and the cured solid (meth)acrylate is dispersed in the still-liquid epoxy resin before both components are fully cured. It is expected that this will result in a cured product with an uneven surface morphology and a matte-finished cured product with reduced gloss. However, this is merely speculation and is not intended to be limiting. The blending ratio of the two components is preferably in the range of 5:1 to 10:1, and more preferably in the range of 6:1 to 10:1.

[0035] <Photoacid generator> The photoacid generator is a compound capable of releasing an acidic active substance capable of polymerizing the above-mentioned epoxy resin upon irradiation with light, and is composed of a cation moiety that absorbs light and an anion moiety that serves as an acid generating source. Examples include diazonium salt compounds, iodonium salt compounds, sulfonium salt compounds, phosphonium salt compounds, selenium salt compounds, oxonium salt compounds, ammonium salt compounds, bromine salt compounds, metallocene complexes, and iron arene complexes. These may be used alone or in combination of two or more.

[0036] Among the above-mentioned photoacid generators, phosphonium salt compounds can be preferably used. Examples of the phosphonium salt compounds include triphenylsulfonium hexafluoroacylate, triphenylsulfonium hexahexafluoroborate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetrakis(pentafluorobenzyl)borate, methyldiphenylsulfonium tetrafluoroborate, methyldiphenylsulfonium tetrakis(pentafluorobenzyl)borate, dimethylphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, diphenylnaphthylsulfonium hexafluoroarsenate, tritoylsulfonium hexafluorophosphate, anisyldiphenylsulfonium hexahexafluoroantimonate, 4-butoxyphenyldiphenylsulfonium tetrafluoroborate, 4-butoxyphenyldiphenylsulfonium tetrakis(pentafluorobenzyl)borate, 4-chlorophenyl Diphenylsulfonium hexafluoroantimonate, tris(4-phenoxyphenyl)sulfonium hexafluorophosphate, di(4-ethoxyphenyl)methylsulfonium hexafluoroarsenate, 4-acetylphenyldiphenylsulfonium tetrafluoroborate, 4-acetylphenyldiphenylsulfonium tetrakis(pentafluorobenzyl)borate, tris(4-thiomethoxyphenyl)sulfonium hexafluorophosphate, di(methoxysulfonylphenyl)methylsulfonium hexafluoroantimonate, di(methoxynaphthyl)methylsulfonium tetrafluoroborate, di(methoxynaphthyl)methylsulfonium tetrakis(pentafluorobenzyl)borate, di(carbomethoxyphenyl)methylsulfonium hexafluorophosphate, (4-octyloxyphenyl)diphenylsulfonium tetrakis(3,5-bis-trifluoromethylphenyl)borate, tris(dodecylphenyl)sulfonium tetrakis(3,5-bis-trifluoromethylphenyl)borate, 4-acetamidophenyldiphenylsulfonium tetrafluoroborate, 4-acetamidophenyldiphenylsulfonium tetrakis(pentafluorobenzyl)borate, dimethylnaphthylsulfonium hexafluorophosphate, trifluoromethyldiphenylsulfonium tetrafluoroborate, trifluoromethyldiphenylsulfonium tetrakis(pentafluorobenzyl)borate, phenylmethylbenzylsulfonium hexafluorophosphate, 10-methylphenoxathiinium hexafluorophosphate, 5 10-methylthianthrenium hexafluorophosphate, 10-phenyl-9,9-dimethylthioxanthenium hexafluorophosphate, 10-phenyl-9-oxothioxanthenium xanthenium tetrafluoroborate, 10-phenyl-9-oxothioxanthenium tetrakis(pentafluorobenzyl)borate, 5-methyl-10-oxothiathrenium tetrafluoroborate, 5-methyl-10-oxothiathrenium tetrakis(pentafluorobenzyl)borate, and 5-methyl-10,10-dioxothiathrenium hexafluorophosphate. These may be used alone or in combination of two or more.

[0037] In addition, a sensitizer may be used in combination with the photoacid generator as appropriate to improve the photosensitivity and to impart sensitivity to light of long wavelengths such as g-line (436 nm), h-line (405 nm), and i-line (365 nm).

[0038] The amount of the photoacid generator is preferably 1 to 50 parts by mass, more preferably 1 to 30 parts by mass, based on 100 parts by mass of the epoxy resin, calculated as solid content.

[0039] <Thermosetting compounds> The photocurable resin composition of the present invention may contain a thermosetting compound in addition to the above components. The inclusion of a thermosetting compound can improve the heat resistance and hardness of the cured product. Examples of thermosetting compounds that can be used in the present invention include amino resins other than melamine resins, such as benzoguanamine resins and benzoguanamine derivatives, blocked isocyanate compounds, cyclocarbonate compounds, thermosetting components other than the above-mentioned epoxy resins having a cyclic (thio)ether group, and known thermosetting resins such as bismaleimide and carbodiimide resins. Other examples include aromatic amines having a benzene ring and reaction products of amine compounds and epoxy compounds.

[0040] As the thermosetting compound having a cyclic (thio)ether group other than the above-mentioned epoxy resins, a compound having two or more of either one or both of a 4- or 5-membered cyclic ether group or a cyclic thioether group in the molecule is preferred, and examples thereof include a compound having at least two or more oxetanyl groups in the molecule, i.e., a polyfunctional oxetane compound, and a compound having two or more thioether groups in the molecule, i.e., an episulfide resin.

[0041] Examples of the polyfunctional oxetane compound include polyfunctional oxetanes such as bis[(3-methyl-3-oxetanylmethoxy)methyl]ether, bis[(3-ethyl-3-oxetanylmethoxy)methyl]ether, 1,4-bis[(3-methyl-3-oxetanylmethoxy)methyl]benzene, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, (3-methyl-3-oxetanyl)methyl acrylate, (3-ethyl-3-oxetanyl)methyl acrylate, (3-methyl-3-oxetanyl)methyl methacrylate, (3-ethyl-3-oxetanyl)methyl methacrylate, and oligomers or copolymers thereof, as well as ethers of oxetane alcohols with novolac resins, poly(p-hydroxystyrene), cardo-type bisphenols, calixarenes, calixresorcinarenes, silsesquioxane, and other resins having a hydroxyl group. Other examples include copolymers of unsaturated monomers having an oxetane ring and alkyl (meth)acrylates.

[0042] As the episulfide resin, which is a compound having two or more cyclic (thio)ether groups in the molecule, for example, an episulfide resin in which the oxygen atom of the epoxy group of a novolac epoxy resin is replaced with a sulfur atom can be used.

[0043] Isocyanate compounds and blocked isocyanate compounds are compounds having multiple isocyanate groups or blocked isocyanate groups in one molecule. Examples of such compounds having multiple isocyanate groups or blocked isocyanate groups in one molecule include polyisocyanate compounds and blocked isocyanate compounds. A blocked isocyanate group is a group in which an isocyanate group is protected and temporarily inactivated by reaction with a blocking agent; when heated to a predetermined temperature, the blocking agent dissociates to generate an isocyanate group. Addition of the polyisocyanate compound or blocked isocyanate compound can improve the curability of the composition and the toughness of the cured product.

[0044] Examples of such polyisocyanate compounds include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples of aromatic polyisocyanates include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,5-diisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate, and 2,4-tolylene dimer.

[0045] Specific examples of aliphatic polyisocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4-methylenebis(cyclohexyl isocyanate), and isophorone diisocyanate.

[0046] Specific examples of alicyclic polyisocyanates include bicycloheptane triisocyanate, as well as adducts, biuret compounds, and isocyanurates of the isocyanate compounds listed above.

[0047] The blocked isocyanate compound is an addition reaction product of an isocyanate compound and an isocyanate blocking agent. Examples of the isocyanate compound that can react with the blocking agent include the above-mentioned polyisocyanate compounds.

[0048] Examples of isocyanate blocking agents include phenol-based blocking agents such as phenol, cresol, xylenol, chlorophenol, and ethylphenol; lactam-based blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; active methylene-based blocking agents such as ethyl acetoacetate and acetylacetone; methanol, ethanol, propanol, butanol, amyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, benzyl ether, methyl glycolate, butyl glycolate, diacetone alcohol, and methyl lactate. and ethyl lactate; oxime-based blocking agents such as formaldehyde oxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, and cyclohexane oxime; mercaptan-based blocking agents such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, thiophenol, methylthiophenol, and ethylthiophenol; acid amide-based blocking agents such as acetic acid amide and benzamide; imide-based blocking agents such as succinimide and maleimide; amine-based blocking agents such as xylidine, aniline, butylamine, and dibutylamine; imidazole-based blocking agents such as imidazole and 2-ethylimidazole; and imine-based blocking agents such as methyleneimine and propyleneimine.

[0049] The blocked isocyanate compound may be a commercially available product, and examples thereof include Sumidur BL-3175, BL-4165, BL-1100, BL-1265, Desmodur TPLS-2957, TPLS-2062, TPLS-2078, TPLS-2117, Desmotherm 2170, and Desmotherm 2265 (all manufactured by Sumika Covestro Urethane Co., Ltd.), Coronate 2512, Coronate 2513, and Coronate 2520 (all manufactured by Tosoh Corporation), B-830, B-815, B-846, B-870, B-874, and B-882 (all manufactured by Mitsui Chemicals, Inc.), TPA-B80E, 17B-60PX, and E402-B80T (all manufactured by Asahi Kasei Corporation). Sumidur BL-3175 and BL-4265 are obtained by using methyl ethyl oxime as a blocking agent. Such compounds having multiple isocyanate groups or blocked isocyanate groups in one molecule may be used alone or in combination of two or more.

[0050] When the photocurable resin composition of the present invention contains a thermosetting compound, the amount of the thermosetting compound is preferably 1 to 30 mass % based on the total mass of the photocurable resin composition, from the viewpoint of improving the storage stability of the composition and the toughness and heat resistance of the cured product.

[0051] Furthermore, when the photocurable resin composition of the present invention contains a thermosetting compound, it may contain a thermosetting catalyst component that helps cure the thermosetting compound. The thermosetting catalyst component can be a compound that promotes a curing reaction when mixed with the main component and heated. Among the thermosetting catalyst components, it is preferable to contain at least one of a basic catalyst and an acidic catalyst, as this promotes rapid thermal crosslinking. Furthermore, among these, the inclusion of a basic catalyst is more preferable, as it facilitates crosslinking. Examples of the basic catalyst include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, and 4-methyl-N,N-dimethylbenzylamine; phosphine compounds such as tributylphosphine and triphenylphosphine; and hydrazine compounds such as adipic acid dihydrazide and sebacic acid dihydrazide. Commercially available examples include 2MZ-A, 2MZ-OK, 2PHZ, 2P4BHZ, and 2P4MHZ (all trade names of imidazole compounds), DBU, DBN, U-CATSA102, and U-CAT5002 (all bicyclic amidine compounds and their salts) manufactured by Shikoku Chemical Industry Co., Ltd. S-triazine derivatives such as guanamine, acetoguanamine, benzoguanamine, melamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine-isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine-isocyanuric acid adduct can also be used. Preferably, these compounds that also function as adhesion promoters can be used in combination with the thermal curing catalyst. These basic catalysts may be used alone or in suitable combination of two or more.

[0052] Examples of acidic catalysts for thermosetting catalysts include novolac resins and acid anhydrides. Examples of novolac resins include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, and poly-p-vinylphenol. These novolac resin-based acidic catalysts may be used alone or in appropriate combination of two or more.

[0053] Examples of acid anhydride-based acidic catalysts include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, benzophenonetetracarboxylic anhydride, succinic anhydride, methylsuccinic anhydride, dimethylsuccinic anhydride, dichlorosuccinic anhydride, methylnadic acid, dodecylsuccinic acid, chlorendec anhydride, maleic anhydride, 3,6-endomethylenetetrahydrophthalic anhydride, hexachloroendomethylenetetrahydrophthalic anhydride, methyl-3,6-endomethylenetetrahydrophthalic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, ethylene glycol bisanhydrotrimellitate, and glycerin bis(anhydrotrimellitate) monoacetate. These acid anhydride-based acidic catalysts may be used alone or in appropriate combination of two or more.

[0054] <Coloring agent> The photocurable composition of the present invention may contain a colorant component. The inclusion of a colorant component can prevent malfunctions due to infrared rays and the like emitted from surrounding devices when a cured product formed from the photocurable composition is provided on an electronic circuit board. Furthermore, when the cured product is engraved by means of laser marking or the like, marks such as letters and symbols can be easily recognized.

[0055] As the colorant component, organic or inorganic pigments and dyes can be used alone or in combination of two or more. Among these, black pigments are preferred from the viewpoint of electromagnetic wave and infrared shielding properties. Examples of black pigments that can be used include, but are not limited to, carbon black, naphthalene black, perylene black, iron oxide, manganese dioxide, aniline black, activated carbon, etc. Carbon black is particularly preferred from the viewpoint of preventing malfunction of semiconductor devices. In addition, red, blue, green, yellow, or other pigments or dyes can be mixed in place of carbon black to produce black or a black-like color.

[0056] Red colorants include monoazo-based, disazo-based, azo-lake-based, benzimidazolone-based, perylene-based, diketopyrrolopyrrole-based, condensed azo-based, anthraquinone-based, and quinacridone-based colorants, and specific examples thereof include the following.Monoazo red colorants such as Pigment Red 1, 2, 3, 4, 5, 6, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 112, 114, 146, 147, 151, 170, 184, 187, 188, 193, 210, 245, 253, 258, 266, 267, 268, 269, disazo red colorants such as Pigment Red 37, 38, 41, Pigment Red 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 50:1, 52:1, 52:2, 53:1, 53:2, 57 Monoazo lake-based red colorants such as Pigment Red 171, Pigment Red 175, Pigment Red 176, Pigment Red 185, and Pigment Red 208; benzimidazolone-based red colorants such as Solvent Red 135, Solvent Red 179, Pigment Red 123, Pigment Red 149, Pigment Red 166, Pigment Red 178, Pigment Red 179, and P perylene-based red colorants such as Pigment Red 190, Pigment Red 194, and Pigment Red 224; diketopyrrolopyrrole-based red colorants such as Pigment Red 254, Pigment Red 255, Pigment Red 264, Pigment Red 270, and Pigment Red 272; Pigment Red 220, Pigment Red 144, Pigment Red 166, Pigment Red 214, Pigment Red 220, Pigment Red 221, P Examples of suitable red colorants include condensed azo red colorants such as Pigment Red 242, anthraquinone red colorants such as Pigment Red 168, Pigment Red 177, Pigment Red 216, Solvent Red 149, Solvent Red 150, Solvent Red 52, and Solvent Red 207, and quinacridone red colorants such as Pigment Red 122, Pigment Red 202, Pigment Red 206, Pigment Red 207, and Pigment Red 209.

[0057] Blue colorants include phthalocyanine and anthraquinone types, and pigment types include compounds classified as pigments, such as Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Blue 15:6, Pigment Blue 16, and Pigment Blue 60. Dye types include Solvent Blue 35, Solvent Blue 63, Solvent Blue 68, Solvent Blue 70, Solvent Blue 83, Solvent Blue 87, Solvent Blue 94, Solvent Blue 97, Solvent Blue 122, Solvent Blue 136, Solvent Blue 67, and Solvent Blue 70. In addition to these, metal-substituted or unsubstituted phthalocyanine compounds can also be used.

[0058] Green colorants include phthalocyanine-based, anthraquinone-based, and perylene-based compounds, and specific examples that can be used include Pigment Green 7, Pigment Green 36, Solvent Green 3, Solvent Green 5, Solvent Green 20, and Solvent Green 28. In addition to the above, metal-substituted or unsubstituted phthalocyanine compounds can also be used.

[0059] Green colorants include phthalocyanine, anthraquinone, and perylene compounds, such as Pigment Green 7, Pigment Green 36, Solvent Green 3, Solvent Green 5, Solvent Green 20, and Solvent Green 28. In addition to the above, metal-substituted or unsubstituted phthalocyanine compounds and iodine green can also be used.

[0060] Yellow colorants include monoazo-based, disazo-based, condensed azo-based, benzimidazolone-based, isoindolinone-based, and anthraquinone-based colorants, and specific examples thereof include the following. Anthraquinone-based yellow colorants such as Solvent Yellow 163, Pigment Yellow 24, Pigment Yellow 108, Pigment Yellow 193, Pigment Yellow 147, Pigment Yellow 199, and Pigment Yellow 202; isoindolinone-based yellow colorants such as Pigment Yellow 110, Pigment Yellow 109, Pigment Yellow 139, Pigment Yellow 179, and Pigment Yellow 185; Pigment Yellow 93, Pigment Yellow 94, Pigment Yellow 95, Pigment Yellow 128, Pigment Yellow 155, Pigment Yellow 166, and Pigment Yellow 1 condensed azo-based yellow colorants such as Pigment Yellow 80, benzimidazolone-based yellow colorants such as Pigment Yellow 120, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 156, Pigment Yellow 175, and Pigment Yellow 181, and Pigment Yellows 1, 2, 3, 4, 5, 6, 9, 10, 12, 61, 62, and 6 Monoazo yellow colorants such as 2:1, 65, 73, 74, 75, 97, 100, 104, 105, 111, 116, 167, 168, 169, 182, and 183, and disazo yellow colorants such as Pigment Yellow 12, 13, 14, 16, 17, 55, 63, 81, 83, 87, 126, 127, 152, 170, 172, 174, 176, 188, and 198 can be used.

[0061] In addition, colorants such as purple, orange, brown, etc. may be added to adjust the color tone. Specific examples include Crystal Violet, Pigment Violet 19, 23, 29, 32, 36, 38, 42, Solvent Violet 13, 36, CI Pigment Orange 1, CI Pigment Orange 5, CI Pigment Orange 13, CI Pigment Orange 14, CI Pigment Orange 16, CI Pigment Orange 17, CI Pigment Orange 24, CI Pigment Orange 34, CI Pigment Orange 36, CI Pigment Orange 38, CI Pigment Orange 40, CI Pigment Orange 43, CI Pigment Orange 46, CI Pigment Orange 49, CI Pigment Orange 51, CI Pigment Orange 61, CI Pigment Orange 63, CI Pigment Orange 64, CI Pigment Orange 71, CI Pigment Orange 73, CI Pigment Brown 23, CI Pigment Brown 25, CI Pigment Black 1, and CI Pigment Black 7.

[0062] When the above-mentioned colorants contain inorganic pigments, a coupling agent component may be included as necessary to improve the dispersibility of the inorganic pigment in the composition or to improve the adhesiveness and adhesion to the substrate when a cured coating is formed. Examples of coupling agents include titanate-based coupling agents, aluminate-based coupling agents, and silane coupling agents. Among these, silane coupling agents are preferred. Note that the coupling agent does not necessarily need to be included in both the base agent and the curing agent, and may be included in either one.

[0063] Examples of organic groups contained in the silane coupling agent include vinyl groups, epoxy groups, styryl groups, methacryloxy groups, acryloxy groups, amino groups, ureido groups, chloropropyl groups, mercapto groups, polysulfide groups, and isocyanate groups. Commercially available silane coupling agents can be used, and examples thereof include KA-1003, KBM-1003, KBE-1003, KBM-303, KBM-403, KBE-402, KBE-403, KBM-1403, KBM-502, KBM-503, KBE-502, KBE-503, KBM-5103, KBM-602, KBM-603, KBE-603, KBM-903, KBE-903, KBE-9103, KBM-9103, KBM-573, KBM-575, KBM-6123, KBE-585, KBM-703, KBM-802, KBM-803, KBE-846, and KBE-9007 (all trade names; manufactured by Shin-Etsu Silicone Chemical Co., Ltd.). These may be used alone or in combination of two or more.

[0064] <Inorganic filler> The photocurable resin composition of the present invention preferably contains substantially no inorganic filler. Examples of conventionally known inorganic fillers include barium sulfate, barium titanate, silica (e.g., amorphous silica, crystalline silica, fused silica, and spherical silica), talc, clay, Neuburg silica particles, boehmite, magnesium carbonate, calcium carbonate, titanium oxide, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, and calcium zirconate, as well as metal powders (e.g., copper, tin, zinc, nickel, silver, palladium, aluminum, iron, cobalt, gold, and platinum). However, the inclusion of these inorganic fillers in the photocurable resin composition of the present invention may result in an increase in the average particle size of the photocurable resin composition or an increase in the viscosity of the photocurable resin composition, potentially resulting in printing defects. Therefore, the photocurable resin composition of the present invention preferably contains substantially no inorganic filler. In the present invention, even if the photocurable resin composition does not contain an inorganic filler, a matte-finish cured product can be obtained as described above.

[0065] In this specification, "substantially free" means that the component is not actively blended as a constituent, and does not exclude the inclusion of a small amount within a range that does not impair the effects of the present invention. For example, the content is 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, converted to solid content, in the photocurable resin composition.

[0066] The photocurable resin composition of the present invention has a particle size distribution D 50 The particle size distribution D of the components contained in the photocurable resin composition is preferably 0.4 μm or less, and more preferably 0.3 μm or less. 100 The particle size distribution D of the components contained in the photocurable resin composition is preferably 1 μm or less, and more preferably 0.8 μm. 50 and D 100 When the particle size distribution D is within the above range, the photocurable resin composition has good coatability when applied to inkjet printing. 50 This refers to the particle size when the cumulative percentage from the smallest particle size in the particle size distribution measurement results measured as follows is 50%. 50 refers to the particle size when the cumulative percentage is 100%.

[0067] In the present invention, the particle size distribution D 50 and D 100 was measured using a Microtrac under the following conditions: First, prepare the following equipment and supplies. Particle size distribution meter: Nikkiso Microtrac MT3300EX Circulation device: ASVR manufactured by Nikkiso Co., Ltd. Next, enter the measurement conditions using the following procedure. Launch the software provided with the Microtrac ("Particle Size Distribution Measurement"), proceed from the SET UP screen, and set the time from the measurement condition setting options. Set the set zero time to 30 seconds, the measurement to 30 seconds, and the number of measurements to 2. Next, enter the analysis conditions. In the analysis information, set the particle refractive index to 1.81 (fixed value: average refractive index of all inorganic substances), the particle characteristics to transparent, and the shape to aspherical. In the solvent information, select DPM (dipropylene glycol methyl ether) and set the solvent refractive index to 1.42. Next, enter the scale settings. In the particle size range, set the minimum particle size to 0.021 μm and the maximum particle size to 704 μm. Next, enter the sampling system settings. Set the ASVR cleaning count to 4 times, the flow rate to 50%, the ultrasonic output to 40 W, and the ultrasonic time to 300 seconds. After entering all the measurement conditions, click Save in the measurement condition settings to close. Next, the sample is prepared using the following procedure. 0.3 g of sample (photocurable resin composition) is weighed into a screw bottle, 30 g of dipropylene glycol methyl ether is added little by little using a dropper, and the screw bottle is shaken to dissolve the sample, producing an adjusted sample. The adjusted sample is not subjected to external dispersion or pre-dispersion. Next, the adjusted sample is measured. Click on particle size distribution measurement in the software provided with the Microtrac to open the sample loading screen. Use the dropper to drip a few drops of the adjusted sample into the sample inlet on the main unit. When a red indicator bar appears on the sample loading screen, drip the adjusted sample into the sample inlet until it falls within the red to green range. Once it falls within the green range, press the measurement button to start measurement. The process from sample preparation to adjusted sample measurement is completed within 5 minutes. The particle size distribution D in the particle size distribution results measured by the above operations is 50 and D 100 Ask for.

[0068] <Other ingredients> In addition to the components described above, the photocurable resin composition of the present invention may contain, as necessary, known and commonly used additives such as a surface tension adjuster, a surfactant, a matting agent, at least one of a polyester resin, a polyurethane resin, a vinyl resin, an acrylic resin, a rubber resin, waxes, a silicone-based, a fluorine-based, a polymer-based or other antifoaming agent and leveling agent for adjusting the film properties, and an adhesion imparting agent such as an imidazole-based, thiazole-based, triazole-based, or silane coupling agent.

[0069] The photocurable resin composition of the present invention may contain an organic solvent, if necessary, to adjust the viscosity. Examples of the organic solvent include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents. More specific examples of the solvent include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, dipropylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, and propylene glycol butyl ether acetate; alcohols such as ethanol, propanol, ethylene glycol, and propylene glycol; carbonates such as ethylene carbonate and propylene carbonate; aliphatic hydrocarbons such as octane and decane; and petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. The organic solvents may be used alone or in combination of two or more.

[0070] The photocurable resin composition of the present invention may be adjusted to a viscosity suitable for inkjet printing. A cured product can be obtained by applying the composition to a desired high-resolution pattern by inkjet printing and curing the resulting coating. From the viewpoint of suitability for inkjet printing, the viscosity of the photocurable resin composition at 25°C is preferably 10 to 35 mPa·s or less, and more preferably 10 to 20 mPa·s. In this specification, unless otherwise specified, viscosity refers to the viscosity measured at 25°C, 100 rpm, and 30 seconds using a cone-plate viscometer (TVE-33H, manufactured by Toki Sangyo Co., Ltd.) with a 1°34' x R24 cone rotor in accordance with the viscosity measurement method using a 10 cone-plate rotational viscometer specified in JIS K8803:2011.

[0071] [Cured product] The photocurable resin composition of the present invention can be applied to various printing methods, but in particular, an inkjet method can be used to apply the composition in a desired high-definition pattern and then cure the coating to obtain a cured product such as a cured coating film. The method for applying the photocurable resin composition of the present invention to an object to be coated using the inkjet method is not particularly limited, but from the viewpoints of high-definition patterning and the physical properties of the coating film, the curable composition is ejected from the nozzle of an inkjet printer and deposited at a desired position on the object to be coated.

[0072] After the photocurable resin composition is applied to the substrate, it is irradiated with light. The light irradiation cures the (meth)acrylate and epoxy resin, hardening the coating film or increasing the viscosity of the coating film, thereby preventing the coating film applied to the substrate from spreading. Therefore, it is preferable to irradiate with light as quickly as possible after the curable composition is applied to the substrate. For example, after the curable composition is ejected from the nozzle of an inkjet printer, light irradiation is preferably carried out within 1.0 second, more preferably within 0.5 seconds. High-resolution patterning can be achieved by irradiating with light promptly after ejection. The direction in which the coating film to which the photocurable resin composition is applied is not particularly limited; however, light irradiation can be carried out from an oblique direction on the side of the substrate, or from the back of the substrate if the substrate is transparent. Furthermore, thermal curing may be carried out as needed.

[0073] Suitable light sources for light irradiation include LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, and metal halide lamps. Other sources that can be used include electron beams, alpha rays, beta rays, gamma rays, X-rays, and neutron beams. One or more irradiation light sources can be used, and if two or more light sources are used, it is possible to combine light sources with different wavelengths.

[0074] The amount of light irradiation varies depending on the thickness of the coating film, but is generally 10 to 10,000 mJ / cm 2 , preferably 20 to 2000 mJ / cm 2 , more preferably 100 to 2000 mJ / cm 2 The range may be:

[0075] Furthermore, when the maximum absorption wavelengths of the photoradical polymerization initiator and the photoacid generator are different, they may be irradiated separately using light sources corresponding to their respective maximum absorption wavelengths. In this case, light irradiation is first performed using a light source corresponding to the maximum absorption wavelength of the photoradical polymerization initiator, and then light irradiation is performed using a light source corresponding to the maximum absorption wavelength of the photoacid generator, thereby obtaining a cured product with an even more excellent matte finish. The obtained cured product is suitable for use as a solder resist or marking for electronic circuit boards such as printed wiring boards. [Example]

[0076] The present invention will now be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following, "parts" and "%" are all by mass unless otherwise specified.

[0077] [Preparation of Photocurable Resin Composition] The components shown in Table 1 below were blended, premixed in a stirrer, and then filtered through a glass fiber filter with a pore size of 1 μm to prepare curable compositions for inkjet 1 to 16. The blend amounts in the table indicate parts by mass of solid content unless otherwise specified.

[0078] The values ​​*1 to *8 in the table are as follows: The viscosity of the epoxy resin was measured at 25°C, 5 rpm, and 30 seconds in accordance with the viscosity measurement method using a cone-plate rotational viscometer of JIS K8803:2011, using a cone-plate viscometer (TVH-33H manufactured by Toki Sangyo Co., Ltd.) with a 3° x R9.7 cone rotor.

[0079] *1: Acylphosphine oxide photoinitiator (IGM Resins Omnirad 819) *2: Melamine (Nissan Chemical Co., Ltd., D50=0.5μm) *3: Methylol melamine (Nikaresin, manufactured by Nippon Carbide Industries Co., Ltd.) *4: Bisphenol A epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828, solid content 100% by mass, viscosity 12000 mPa·s) *5: Alicyclic epoxy resin (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, manufactured by Daicel Corporation, Celloxide 2021P, solid content 100% by mass, viscosity 220 mPa·s) *6: Alicyclic epoxy resin (Limonene Dioxide, manufactured by Tomoe Engineering Co., Ltd., Limonene Dioxide, solid content 100% by mass, viscosity 8 mPa·s) *7: Sulfonium salt compound (manufactured by San-Apro Co., Ltd., CPI-110P, dissolved in ethylene carbonate) *8: Ethylene carbonate

[0080] [evaluation] (1) Viscosity The viscosity of each of the photocurable resin compositions 1 to 16 prepared as described above was measured. The viscosity was measured at 25°C, 100 rpm, and 30 seconds using a cone-plate viscometer (TVH-33H manufactured by Toki Sangyo Co., Ltd.) with a 1°34' x R24 cone rotor, in accordance with the viscosity measurement method using a 10 cone-plate rotational viscometer of JIS K8803:2011. The measurement results are shown in Tables 1 and 2.

[0081] (2) Glossiness of the cured product Each of the photocurable resin compositions 1 to 16 prepared as described above was applied to a copper-clad laminate using a 30 μm applicator (manufactured by ERICHSEN), and then exposed to 150 mJ / cm 2 using an LED lamp (manufactured by Panasonic, ANUJ6164). 2 Thereafter, the composition was heated in a hot air circulating drying oven at 150°C for 60 minutes to produce a cured product. Next, the 60-degree specular reflectance of the cured product surface was measured using a Micro Trigloss (manufactured by BYK Japan). The average of the measured values ​​was calculated and rounded to one decimal place to obtain the gloss. The gloss of the cured products formed from each photocurable resin composition was as shown in Tables 1 and 2 below.

[0082] (2) Solvent resistance A substrate having a cured product obtained as described above in (2) Gloss of the cured product was immersed in a bath of propylene glycol monomethyl ether acetate (PGMAc) for 30 minutes. After removing the substrate from the bath and drying, cellophane tape peeling was performed. The evaluation criteria were as follows: ○: No peeling of the cured product △: Slight peeling ×: Peeling The evaluation results are shown in Tables 1 and 2 below.

[0083] (3) Solder heat resistance A rosin-based flux was applied to a substrate having the cured product obtained as described above in (2) Gloss of the cured product, and the substrate was immersed in a solder bath pre-set to 260°C for 10 seconds. The substrate was then removed from the bath and washed with denatured alcohol to remove the flux. After drying, the substrate was peeled with cellophane tape and the cured product was visually evaluated for swelling and peeling. The evaluation criteria were as follows: ◎: No peeling after 10 seconds, 3 times ○: No peeling after 10 seconds △: Slight peeling ×: Peeling The evaluation results are shown in Tables 1 and 2 below.

[0084] (4) Inkjet printability Each of the photocurable resin compositions 1 to 16 was applied to a copper-clad laminate at 25°C using an inkjet printer (FUJIFILM Corporation, Material Printer DMP-2850) to form a 150 μm line and a 100 mm × 100 mm square coating film, and then exposed to an LED lamp (Panasonic ANUJ6164) at 150 mJ / cm 2 The printer cartridge used was a DMC11610 (16 nozzles, coating volume 10 pL). The coating film was heated in a hot air circulating drying oven at 150°C for 60 minutes, and the appearance of the lines and squares was visually inspected. The evaluation criteria for inkjet printability were as follows: Note that satellite refers to small scattering observed when inkjet lines are drawn. ○: No satellites or repellency, and the surface of the coating film is smooth △: No satellites or repellency, but some thin areas are observed ×: Both satellite and bounce are recognized The evaluation results are shown in Tables 1 and 2 below.

[0085] (5) Adhesion to the base The 100mm x 100mm dried coating film prepared in the above (4) Inkjet printability section was measured using an automatic cross-cut tester (Coating Tester Co., Ltd., No. 807-KS2) with a cut length of 1mm on each side. 2 The surface was scratched so that there were 100 squares. Peeling of the resin layer was then confirmed using a tape peel. The evaluation criteria for adhesion were as follows: ◎: No peeling or chipping ○: Number of peeling or chipping is 1 or more and 25 or less △: Number of peeling or chipping is more than 25 and less than 50 ×: More than 50 peeled or chipped pieces The evaluation results are shown in the following Tables 1 and 2. In Table 2, "Not rated" means that the viscosity was too high to be inkjet printed.

[0086] (6) Adhesion to inkjet marking ink Marking ink (IJPR-4000 MW300, manufactured by Taiyo Ink Co., Ltd., Korea) was applied to the surface of the 100 mm x 100 mm dried coating film prepared in the above (4) Inkjet printability section using an inkjet printer (FUJIFILM Corporation, Material Printer DMP-2850) at a temperature of 50°C to form a 50 mm x 50 mm square coating film with a thickness of 20 μm, and the film was then illuminated with an LED lamp (Panasonic Corporation, ANUJ6164) at 200 mJ / cm. 2Then, after heating in a hot air circulating drying oven at 150°C for 60 minutes, the area where the marking ink coating was formed was scratched in the same manner as above using an automatic cross-cut tester, and peeling of the resin layer was confirmed using tape peel. The evaluation criteria for adhesion were as follows: ◎: No peeling or chipping ○: Peeling or chipping: 1 or more, 10 or less △: More than 10 peeled or chipped pieces, 50 or less ×: More than 50 peeled or chipped pieces The evaluation results are shown in the following Tables 1 and 2. In Table 2, "Not rated" means that the viscosity was too high to be inkjet printed.

[0087] (7) Particle size distribution (D 50 and D 100 ) For each of the photocurable resin compositions 1 to 9, the particle size distribution D of the components in the composition 50 and D 100 was measured as follows: First, the following equipment and supplies were prepared. Particle size distribution meter: Nikkiso Microtrac MT3300EX Circulation device: ASVR manufactured by Nikkiso Co., Ltd. Next, enter the measurement conditions using the following procedure. Launch the software provided with the Microtrac ("Particle Size Distribution Measurement"), proceed from the SET UP screen, and set the time from the measurement condition setting options. Set the set zero time to 30 seconds, the measurement to 30 seconds, and the number of measurements to 2. Next, enter the analysis conditions. In the analysis information, set the particle refractive index to 1.81 (fixed value: average refractive index of all inorganic substances), the particle characteristics to transparent, and the shape to aspherical. In the solvent information, select DPM (dipropylene glycol methyl ether) and set the solvent refractive index to 1.42. Next, enter the scale settings. In the particle size range, set the minimum particle size to 0.021 μm and the maximum particle size to 704 μm. Next, enter the sampling system settings. Set the ASVR cleaning frequency to 4 times, the flow rate to 50%, the ultrasonic output to 40 W, and the ultrasonic time to 300 seconds. After entering all the measurement conditions, click Save in the measurement condition settings to close. Next, the sample is prepared using the following procedure. 0.3 g of sample (photocurable resin composition) is weighed into a screw bottle, 30 g of dipropylene glycol methyl ether is added little by little using a dropper, and the screw bottle is shaken to dissolve the sample, producing an adjusted sample. The adjusted sample is not subjected to external dispersion or pre-dispersion. Next, the adjusted sample is measured. Click on particle size distribution measurement in the software provided with the Microtrac to open the sample loading screen. Use the dropper to drip a few drops of the adjusted sample into the sample inlet on the main unit. When a red indicator bar appears on the sample loading screen, drip the adjusted sample into the sample inlet until it falls within the red to green range. Once it falls within the green range, press the measurement button to start measurement. The process from sample preparation to adjusted sample measurement is completed within 5 minutes. The particle size distribution D in the particle size distribution results measured by the above operations is 50 and D 100 Ask for. Particle size distribution D 50 and D 100 As a result of measuring the D of the components contained in each of the photocurable resin compositions 1 to 9, 50 is 0.3 μm or less, and D 100was less than 0.8 μm.

[0088] [Table 1]

[0089] [Table 2]

[0090] As is clear from the evaluation results in Table 1, the photocurable resin compositions (Examples 1 to 9) containing (meth)acrylate, a photoradical polymerization initiator, at least one of melamine and a melamine resin, an epoxy resin, and a photoacid generator, in which the (meth)acrylate and the epoxy resin are contained in a predetermined ratio, can produce matte cured products with a moderately suppressed gloss while satisfying inkjet suitability, and also have good adhesion to dissimilar components.

[0091] In contrast, a photocurable resin composition (Comparative Example 1) containing (meth)acrylate, a photoradical polymerization initiator, and at least one of melamine and a melamine resin, but not containing an epoxy resin or a photoacid generator, not only does not satisfy inkjet suitability, but also does not produce a matte cured product and has insufficient adhesion to dissimilar components. Furthermore, a photocurable resin composition (Comparative Example 2) containing at least one of melamine and melamine resin, an epoxy resin, and a photoacid generator but not containing a (meth)acrylate or a photoradical polymerization initiator, had satisfactory inkjet suitability but did not provide a matte cured product, and was also found to have insufficient solvent resistance, solder heat resistance, and adhesion to inkjet marking ink. Furthermore, in the photocurable resin compositions (Comparative Examples 3 to 7) that contain (meth)acrylate, a photoradical polymerization initiator, an epoxy resin, and a photoacid generator but do not contain at least one of melamine and a melamine resin, although the inkjet suitability is satisfactory, a matte cured product cannot be obtained, and the solder heat resistance and adhesion to the inkjet marking ink are insufficient.

Claims

1. A photocurable resin composition comprising: a (meth)acrylate; a photoradical polymerization initiator; at least one of melamine and a melamine resin; an epoxy resin; and a photoacid generator, wherein the (meth)acrylate and the epoxy resin are contained in a ratio of 3:1 to 15:1 by mass.

2. 2. The photocurable resin composition according to claim 1, having a viscosity at 25°C of 10 to 35 mPa·s.

3. The photocurable resin composition according to claim 1 , wherein the epoxy resin comprises an epoxy resin that is liquid at room temperature.

4. The photocurable resin composition according to claim 2 , wherein the epoxy resin that is liquid at room temperature comprises a bisphenol A type epoxy resin.

5. 5. The photocurable resin composition according to claim 4, wherein the bisphenol A type epoxy resin has a viscosity of 15,000 mPa·s or less at 25°C.

6. 2. The photocurable resin composition according to claim 1, wherein the total amount of the (meth)acrylate and the epoxy resin is 80 mass % or more, calculated as solid content, based on the total amount of the photocurable resin composition.

7. At least one of the melamine and the melamine resin has an average particle diameter (D ５０ The photocurable resin composition according to claim 1 , wherein

8. 2. The photocurable resin composition according to claim 1, wherein the total amount of the melamine and the melamine resin is 1 to 10 mass % in terms of solid content based on the total mass of the photocurable resin composition.

9. 2. The photocurable resin composition according to claim 1, wherein the (meth)acrylate has at least one cationically polymerizable functional group selected from the group consisting of a vinyl ether group, an epoxy group, a thioether group, a trioxane group, and an oxetane group.

10. The particle size distribution (D ５０ 2. The photocurable resin composition according to claim 1, wherein the particle size is 0.4 μm or less.

11. The particle size distribution (D １００ 2. The photocurable resin composition according to claim 1, wherein the particle size is 1 μm or less.

12. The photocurable resin composition according to claim 1, which is used for inkjet printing.

13. A cured product of the photocurable resin composition according to any one of claims 1 to 12.

14. An electronic circuit board comprising the cured product according to claim 13.

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