Photosensitive resin composition, dry film, solder resist, and printed wiring board

Abstract

The present invention provides a photosensitive resin composition which can improve developability and deep curing property even if titanium oxide is contained, and can improve the appearance and reflectivity of a solder resist layer. The photosensitive resin composition contains a carboxyl group-containing resin (A), a photopolymerization initiator (B), a photopolymerizable compound (C), an epoxy resin (D), and titanium oxide (E). The carboxyl group-containing resin (A) contains a vinyl polymer having a carboxyl group-containing residue and an ethylenic unsaturated group in a side chain, has a weight average molecular weight of 10,000 to 100,000, and contains an oligomer portion having a molecular weight of 450 to 1,000. The proportion of titanium oxide (E) is 20 parts by mass or more relative to 100 parts by mass of the carboxyl group-containing resin (A).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a photosensitive resin composition, a dry film, a solder resist, and a printed wiring board, and more particularly to a photosensitive resin composition containing a carboxyl group-containing resin, a photopolymerization initiator, a photopolymerizable compound, an epoxy resin, and titanium oxide, and a dry film, a solder resist, and a printed wiring board using the same. BACKGROUND

[0002] In the production of printed wiring boards in electronic devices and the like, the photosensitive resin composition used for the formation of a solder resist layer and the like is required to have excellent developability, that is, a short breakpoint as the time required for development, and a wide drying range, and it is possible to set a longer drying time of a coating film. In the above-described photosensitive resin composition, in order to be able to efficiently reflect light emitted from optical elements of electronic devices such as backlights of liquid crystal displays, titanium oxide is contained on the basis of a carboxyl group-containing resin, a photopolymerization initiator, a photopolymerizable compound, and an epoxy resin, and the solder resist layer is whitened (see Patent Documents 1 to 3).

[0003] In the case where the photosensitive resin composition contains titanium oxide as such, when the photosensitive resin composition is cured by exposure, it is difficult to cure due to the reflection or absorption of light by titanium oxide, and the developability is decreased. In addition, in the case where the content of titanium oxide is increased, it is difficult to cure the formed solder resist layer from the surface layer portion to the deep portion, and the deep portion curing property is decreased. Furthermore, wrinkles are generated in the solder resist layer due to the difference in the curing shrinkage between the deep portion and the surface layer portion of the solder resist layer, and the gloss is decreased, the appearance becomes poor, and the reflectance of the solder resist layer is decreased. The above-described existing composition containing titanium oxide has these poor properties.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-36574

[0007] Patent Document 2: International Publication No. 2016 / 052653

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2020-70436 SUMMARY

[0009] An object of the present application is to provide a photosensitive resin composition capable of improving developability and deep portion curing property even when titanium oxide is contained, and capable of improving the appearance and reflectance of a solder resist layer, and a dry film, a solder resist, and a printed wiring board using the same.

[0010] A photosensitive resin composition according to one embodiment of the present application contains a carboxyl group-containing resin (A), a photopolymerization initiator (B), a photopolymerizable compound (C), an epoxy resin (D), and titanium oxide (E). The carboxyl group-containing resin (A) contains a vinyl polymer having a carboxyl group-containing residue and an ethylenically unsaturated group in a side chain, has a weight average molecular weight of 10,000 to 100,000, and contains an oligomer fraction having a molecular weight of 450 to 1,000. The proportion of the titanium oxide (E) is 20 parts by mass or more relative to 100 parts by mass of the carboxyl group-containing resin (A).

[0011] A dry film according to one embodiment of the present application contains the photosensitive resin composition.

[0012] A solder resist according to one embodiment of the present application contains a cured product of the photosensitive resin composition.

[0013] A printed wiring board according to one embodiment of the present application has a solder resist layer containing a cured product of the photosensitive resin composition. DETAILED DESCRIPTION

[0014] <Photosensitive resin composition>

[0015] A photosensitive resin composition according to one embodiment of the present application contains a carboxyl group-containing resin (A), a photopolymerization initiator (B), a photopolymerizable compound (C), an epoxy resin (D), and titanium oxide (E). The carboxyl group-containing resin (A) contains a vinyl polymer having a carboxyl group-containing residue and an ethylenically unsaturated group in a side chain, has a weight average molecular weight of 10,000 to 100,000, and contains an oligomer fraction having a molecular weight of 450 to 1,000. The proportion of the titanium oxide (E) is 20 parts by mass or more relative to 100 parts by mass of the carboxyl group-containing resin (A).

[0016] The present inventors and others have conducted intensive studies in order to solve the problems of the present application, and as a result, have found that, when a resin (A) having a carboxyl group-containing residue and an ethylenically unsaturated group in a side chain is used as a carboxyl group-containing resin, the resin (A) has a weight average molecular weight within a specific range, and the resin (A) has an oligomer fraction having a molecular weight within a specific range, the developability and the deep curing property of a photosensitive resin composition, and the appearance and the reflectance of a solder resist layer formed therefrom can be improved, thereby completing the present application.

[0017] The composition (X) according to the present embodiment can improve developability and deep curing property even if titanium oxide is contained, and can improve the appearance and reflectivity of the solder resist layer. The reason why the composition (X) exerts the above effects by having the above configuration is not clear, but for example, it can be inferred as follows. It is considered that by making the proportion of the titanium oxide (E) in the composition (X) be the above value or more, making the weight average molecular weight (Mw) of the resin (A) be the above range, and making the resin (A) contain the oligomer portion having a molecular weight of 450 to 1000, the dispersibility of the titanium oxide (E) is further improved. Due to the improvement in the dispersibility of the titanium oxide (E), the reflectivity and gloss of the solder resist layer are improved. In addition, it is considered that on the basis of the improvement in the dispersibility of the titanium oxide (E), the properties such as the curing property of the solder resist layer are more uniformized due to the presence of the oligomer portion of the resin (A). That is, since the oligomer portion has a carboxyl group, the thermal curing property of the solder resist layer becomes more uniform, the breaking point becomes shorter, the allowable width of the drying time is wider, and the developability is improved. It is considered that since the oligomer portion has an ethylenic unsaturated group, the photocuring property of the solder resist layer becomes more uniform, the balance between the surface curing and the deep curing is better, and the deep curing property is improved. In addition, by the balance between the surface curing and the deep curing being better, the generation of wrinkles of the solder resist layer can be suppressed, and the appearance is improved. Thus, according to the present application, it is possible to provide a photosensitive resin composition which can improve developability and deep curing property even if titanium oxide is contained, and which can improve the appearance and reflectivity of the solder resist layer.

[0018] The composition (X) preferably contains an antioxidant (F) and a dispersant (G) in addition to the components (A) to (E), and can contain other components (H) and the like in addition to the components (A) to (G) within a range not impairing the effects of the present application. Hereinafter, each component will be described.

[0019] [Carboxyl group-containing resin (A)]

[0020] The "carboxyl group-containing resin" refers to a resin having a carboxyl group. The composition (X) can be thermally cured by reacting the carboxyl group of the resin (A) with the epoxy group of the epoxy resin (D). The acid value of the resin (A) is preferably 55 mgKOH / g to 145 mgKOH / g. In this case, the thermal curing property of the composition (X) can be further improved, and the developability can be further improved. The acid value of the resin (A) is more preferably 65 mgKOH / g to 130 mgKOH / g, and further preferably 75 mgKOH / g to 120 mgKOH / g. The "acid value" refers to the milligrams of potassium hydroxide required to neutralize 1 g of the solid content of the resin (A).

[0021] The resin (A) is a vinyl polymer having a residue having a carboxyl group (hereinafter, also referred to as a residue having a carboxyl group) as a monomer unit. The "vinyl polymer" means a polymer obtained by polymerizing a monomer composition containing a monomer having an ethylenic carbon-carbon double bond. The resin (A) can have, in addition to the residue from the monomer having an ethylenic carbon-carbon double bond, a residue from a monomer having an acetylenic carbon-carbon triple bond, a residue from a phenol compound and an aldehyde compound, a residue from a carboxylic acid compound and an alcohol compound or an amine compound, and the like.

[0022] Further, the resin (A) has an ethylenic unsaturated group in a side chain. The "side chain" means a chain other than a main chain in an atomic chain constituting the resin (A), and the "main chain" means the longest chain in the atomic chain constituting the resin (A). The "ethylenic unsaturated group" means a group containing an ethylenic carbon-carbon double bond. As the ethylenic unsaturated group, for example, an ethylene group such as a vinyl group, an allyl group, a (meth)acryl group, a styryl group, and the like can be given. The "(meth)acryl group" means one or both of an acryl group and a methacryl group.

[0023] The residue having a carboxyl group is usually formed from a monomer having a carboxyl group and an ethylenic carbon-carbon double bond. As such a monomer, for example, an unsaturated carboxylic acid such as (meth)acrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, propynoic acid, oleic acid, and vinylbenzoic acid can be given. The "(meth)acrylic acid" means one or both of acrylic acid and methacrylic acid.

[0024] The resin (A) can have other residues in addition to the residue having a carboxyl group. As a monomer giving the other residues, for example, a (meth)acrylate, an aromatic vinyl compound, a substituted or unsubstituted ethylene, an unsaturated nitrile, and the like can be given.

[0025] As the (meth)acrylate, for example, an alkyl (meth)acrylate such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate; a cycloalkyl (meth)acrylate such as cyclohexyl (meth)acrylate; an aromatic (meth)acrylate such as phenyl (meth)acrylate and benzyl (meth)acrylate; and the like can be given. The "(meth)acrylate" means one or both of an acrylate and a methacrylate.

[0026] As the aromatic vinyl compound, for example, styrene; α-methylstyrene; substituted styrenes such as o-, m-, and p-methylstyrene, and o-, m-, and p-chlorostyrene; and vinyl naphthalene can be given.

[0027] As the substituted ethylene, for example, an olefin such as propylene, butylene, and vinylcyclohexane; and 4-hydroxy-1-butene can be given.

[0028] As the unsaturated nitrile compound, for example, (meth)acrylonitrile, α-chloro(meth)acrylonitrile, α-ethyl(meth)acrylonitrile, vinylidene cyanide, and the like can be given.

[0029] The resin (A) can be synthesized, for example, by introducing an ethylenically unsaturated group or the like into a side chain of a vinyl polymer having a carboxyl-containing residue. Specifically, the resin (A) can be synthesized, for example, by reacting a carboxyl group of a vinyl polymer having a carboxyl-containing residue with a compound having an epoxy group and an ethylenically unsaturated group (hereinafter, also referred to as an ethylenically unsaturated compound containing an epoxy group). That is, the resin (A) preferably contains a reaction product of a vinyl polymer having a carboxyl-containing residue and an ethylenically unsaturated compound containing an epoxy group.

[0030] As the ethylenically unsaturated compound containing an epoxy group, for example, glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, and the like containing an epoxy group; a vinyl compound containing an epoxy group such as vinyl glycidyl ether; and the like can be given.

[0031] The vinyl polymer having a carboxyl-containing residue can be synthesized, for example, by performing a polymerization reaction on a monomer composition containing a monomer having a carboxyl group and an ethylenically carbon-carbon double bond and, as necessary, other monomers in the presence of a radical polymerization initiator in a solvent such as dipropylene glycol monomethyl ether. As the temperature of the polymerization reaction, for example, 50°C to 150°C, preferably 60°C to 90°C. As the time of the polymerization reaction, for example, 1 hour to 10 hours, preferably 3 hours to 7 hours.

[0032] As the radical polymerization initiator, for example, azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisisonobutyrate, peroxide-based polymerization initiators such as benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, and the like can be given.

[0033] The amount of use of the radical polymerization initiator in the synthesis of the vinyl polymer having a residue containing a carboxyl group is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and further preferably 5 parts by mass or less, relative to 100 parts by mass of the monomer having an ethylenic carbon-carbon double bond, when Mw is 10,000 or more. The amount of use is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and further preferably 2 parts by mass or more. By setting the amount of use of the radical polymerization initiator within the above range, the Mw of the resin (A) can be adjusted to a more appropriate value. In addition, when Mw is less than 10,000, the amount of use of the radical polymerization initiator is preferably 1 part by mass or more, more preferably 4 parts by mass or more, further preferably 10 parts by mass or more, and particularly preferably 20 parts by mass or more, relative to 100 parts by mass of the monomer having an ethylenic carbon-carbon double bond. By setting the amount of use of the radical polymerization initiator within the above range, the Mw of the obtained polymer can be made smaller, and as a result, the proportion of the oligomer portion in the resin (A) can be made larger. There is no particular limitation on the upper limit of the amount of use of the radical polymerization initiator, and for example, it is 50 parts by mass or less.

[0034] In the synthesis of the polymer having a residue containing a carboxyl group, a chain transfer agent is preferably used. That is, at least a part of the resin (A) is preferably a product of a polymerization reaction using a chain transfer agent. By using a chain transfer agent in the polymerization reaction, the Mw of the obtained polymer can be made smaller, and as a result, the proportion of the oligomer portion in the resin (A) can be made larger.

[0035] As the chain transfer agent, for example, unsaturated hydrocarbon compounds such as α-methylstyrene dimer, α-terpinene, dipentene, terpinolene, and the like; thiol compounds such as n-butyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl mercaptoacetate, and the like; halogen compounds such as carbon tetrachloride, dichloromethane, bromoform, and the like can be given. The chain transfer agent preferably contains an unsaturated hydrocarbon compound, and more preferably contains α-methylstyrene dimer. By using an unsaturated hydrocarbon compound as the chain transfer agent, an ethylenic unsaturated group can be introduced at the terminal of the resin (A) and the oligomer contained therein.

[0036] The amount of use of the chain transfer agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 8 parts by mass or more, and particularly preferably 15 parts by mass or more, relative to 100 parts by mass of the ethylenic unsaturated monomer. By setting the amount of use of the chain transfer agent within the above range, the Mw of the obtained polymer can be made smaller, and as a result, the proportion of the oligomer portion in the resin (A) can be made larger.

[0037] The resin (A) can be synthesized, for example, by mixing a vinyl polymer having a residue containing a carboxyl group with a compound having an epoxy group and an ethylenically unsaturated group, and performing an addition reaction between the carboxyl group and the epoxy group in the presence of a polymerization inhibitor such as Metokinon and a catalyst such as dimethylbenzylamine in a solvent such as dipropylene glycol monomethyl ether.

[0038] The vinyl polymer having a residue containing a carboxyl group can be synthesized, for example, not only by the above method but also by a method in which an epoxy group of a vinyl polymer having a residue containing an epoxy group is reacted with a carboxyl group of a compound having a carboxyl group and an ethylenically unsaturated group, and then reacted with a polycarboxylic acid or a polycarboxylic anhydride.

[0039] (weight average molecular weight)

[0040] In the composition (X), it is important that the weight average molecular weight (Mw) of the resin (A) is 10,000 to 100,000. When the Mw of the resin (A) is less than 10,000, the deep curing property of the photosensitive resin composition is decreased, and wrinkles or the like are generated in the solder resist layer, and the appearance becomes poor. In this case, the heat yellowing resistance of the solder resist layer is also decreased. If the Mw of the resin (A) exceeds 100,000, the developability of the composition (X) is decreased.

[0041] The Mw of the resin (A) is preferably 15,000 or more, more preferably 20,000 or more, and further preferably 23,000 or more. The Mw of the resin (A) is preferably 80,000 or less, more preferably 60,000 or less, and further preferably 40,000 or less.

[0042] The Mw of the resin (A) is usually calculated from the results of the molecular weight measurement based on gel permeation chromatography (GPC). The molecular weight measurement based on GPC can be performed, for example, under the following conditions.

[0043] GPC device: SHODEX SYSTEM 11 manufactured by Showa Denko K.K.

[0044] Column: 4 columns of SHODEX KF-800P, KF-005, KF-003, and KF-001 manufactured by Showa Denko K.K. connected in series

[0045] Mobile phase: tetrahydrofuran

[0046] Flow rate: 1 mL / minute

[0047] Column temperature: 45°C

[0048] Detector: differential refractive index (RI) detector

[0049] Standard substance: polystyrene

[0050] (oligomer portion)

[0051] In the composition (X), it is important that the resin (A) contains an oligomer portion having a molecular weight of 450 to 1000. The oligomer portion is a portion having a molecular weight of 450 to 1000 in the resin (A) which is a vinyl polymer having a residue containing a carboxyl group and an ethylenically unsaturated group in a side chain. The resin contained in the oligomer portion preferably has at least one of a residue containing a carboxyl group and an ethylenically unsaturated group, and more preferably has both of a residue containing a carboxyl group and an ethylenically unsaturated group.

[0052] The proportion of the oligomer portion having a molecular weight of 450 to 1000 in the resin (A) is preferably 0.1% or more, more preferably 0.2% or more, further preferably 0.3% or more, and particularly preferably 0.4% or more. The proportion of the oligomer portion having a molecular weight of 450 to 1000 in the resin (A) is preferably 9% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less. By making the proportion of the oligomer portion within the above range, the deep curing property of the composition (X) and the heat yellowing resistance of the solder resist layer can be further improved. The proportion of the oligomer portion having a molecular weight of 450 to 1000 in the resin (A) is usually determined by GPC using a differential refractive index detector, as the proportion of the area of the oligomer portion having a molecular weight of 450 to 1000 with respect to the total area of the resin (A) of 100%. That is, the proportion (%) of the oligomer portion means "(area from the oligomer portion) x 100 / total area from the resin (A)". In the GPC, the molecular weight of the oligomer is calculated using polystyrene as a standard substance. In addition, the total area from the resin (A) and the area from the oligomer portion having a molecular weight of 450 to 1000 can be calculated by the usual area calculation method based on baseline processing and peak processing in the GPC. Specifically, after the peaks in the GPC are divided into a peak from the resin (A) and a peak from components other than the resin (A) such as solvents, monomers, compounds having an epoxy group and an ethylenically unsaturated group, and the like, the portion from the oligomer portion having a molecular weight of 450 to 1000 is calculated in the peak from the resin (A). Thus, the proportion (%) of the oligomer portion is calculated by the formula (area from the oligomer portion) x 100 / (total area from the resin (A)).

[0053] The resin (A) can be used alone as one kind, and in addition, two or more kinds of resins having different Mw from each other can be used in mixture in order to adjust the proportion of the oligomer portion. The resin (A) can be, for example, a mixture of a resin having an Mw of 10000 or more and not containing an oligomer portion and a resin having an Mw of less than 10000 and containing an oligomer portion.

[0054] The proportion of the resin (A) with respect to the solid content of the composition (X) is preferably 10% by mass or more, and more preferably 20% by mass or more. The proportion is preferably 60% by mass or less, and more preferably 50% by mass or less. The "solid content" of the composition (X) refers to the sum of the components other than the solvent in the composition (X).

[0055] [Photopolymerization initiator (B)]

[0056] The photopolymerization initiator (B) is a component that can improve the photosensitivity of the photosensitive resin composition. The composition (X) can be cured at the exposed portion by containing the photopolymerization initiator (B). One or two or more kinds of photopolymerization initiators (B) can be used.

[0057] As the photopolymerization initiator (B), for example, an acylphosphine oxide-based photopolymerization initiator, an α-hydroxyalkylphenone-based photopolymerization initiator, or the like can be given.

[0058] As the acylphosphine oxide-based photopolymerization initiator, for example, the following can be given:

[0059] 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4,6-trimethylbenzoyl-ethyl-phenyl-phosphinic acid ester, and the like;

[0060] bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 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 oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, and the like.

[0061] As the α-hydroxyalkylphenone-based photopolymerization initiator, for example, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propane-1-one, and the like can be given.

[0062] As the photopolymerization initiator (B) other than the above, for example, benzoin and an alkyl ether thereof; acetophenone, benzil dimethyl ketal, and the like can be given as an acetophenone-based photopolymerization initiator; 2-methylanthraquinone and the like can be given as an anthraquinone-based photopolymerization initiator; 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diisopropylthioxanthone, and the like can be given as a thioxanthone-based photopolymerization initiator; benzophenone, 4-benzoyl-4'-methyl diphenyl sulfide, and the like can be given as a benzophenone-based photopolymerization initiator; 2,4-diisopropylxanthone and the like can be given as a xanthone-based photopolymerization initiator; 2-methyl-l-[4-(methylthio)phenyl]-2-morpholinopropanone and the like can be given as a nitrogen-containing photopolymerization initiator; 2-methyl-l-(4-methylthiophenyl)-2-morpholinopropan-l-one, 2-benzyl-2-dimethylamino-l-(4-morpholinophenyl)-butanone-l, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-l-[4-(4-morpholinyl)phenyl]-l-butanone, and the like can be given as an α-aminoalkylphenone-based photopolymerization initiator; 1-[4-(phenylthio)-l,2-octanedione-2-(O-benzoyl oxime)], l-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone-l-(O-acetyloxime), and the like oxime ester-based photopolymerization initiator, and the like can be given.

[0063] The photopolymerization initiator (B) preferably contains an acylphosphine oxide-based photopolymerization initiator. In this case, the developability and the deep curing property of the composition (X) can be further improved. The acylphosphine oxide-based photopolymerization initiator preferably contains bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. In this way, by using a substance having an absorption up to a long wavelength region as the photopolymerization initiator (B), the deep curing property of the composition (X) can be further improved.

[0064] When the photopolymerization initiator (B) contains an acylphosphine oxide-based photopolymerization initiator, the proportion of the acylphosphine oxide-based photopolymerization initiator in the photopolymerization initiator (B) is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and particularly preferably 20% by mass or more. The proportion is, for example, 100% by mass, and is preferably 80% by mass or less, and more preferably 50% by mass or less.

[0065] In addition, the photopolymerization initiator (B) preferably contains an α-hydroxyalkylphenone-based photopolymerization initiator in addition to the acylphosphine oxide-based photopolymerization initiator. In this case, the developability and the deep curing property of the composition (X) can be further improved, in addition, the surface curing property can be improved, and the solubility of the photopolymerization initiator is improved, so the storage stability of the composition (X) can be further improved.

[0066] When the photopolymerization initiator (B) contains an α-hydroxyalkyl phenone-based photopolymerization initiator, the proportion of the α-hydroxyalkyl phenone-based photopolymerization initiator in the photopolymerization initiator (B) is preferably 1% by mass or more, more preferably 10% by mass or more, and further preferably 50% by mass or more. The proportion is preferably 95% by mass or less, and more preferably 85% by mass or less.

[0067] When the photopolymerization initiator (B) contains an acylphosphine oxide-based photopolymerization initiator and an α-hydroxyalkyl phenone-based photopolymerization initiator, the total proportion of the acylphosphine oxide-based photopolymerization initiator and the α-hydroxyalkyl phenone-based photopolymerization initiator in the photopolymerization initiator (B) is preferably 10% by mass or more, more preferably 50% by mass or more, and further preferably 90% by mass or more. The proportion can be 100% by mass.

[0068] The proportion of the photopolymerization initiator (B) with respect to 100 parts by mass of the resin (A) is preferably 0.1 parts by mass to 100 parts by mass. In this case, the resolution and the deep curing property of the composition (X) can be further improved. The proportion is more preferably 1 part by mass to 90 parts by mass, further preferably 10 parts by mass to 80 parts by mass, and particularly preferably 20 parts by mass to 60 parts by mass.

[0069] The proportion of the photopolymerization initiator (B) with respect to the solid content of the composition (X) is preferably 1% by mass to 30% by mass, more preferably 3% by mass to 20% by mass, and further preferably 5% by mass to 15% by mass.

[0070] [Photopolymerizable compound (C)]

[0071] The photopolymerizable compound (C) is a component that imparts photocurability to the photosensitive resin composition. The photopolymerizable compound (C) generally contains a compound having an ethylenic unsaturated group. Among them, the above-described resin (A) does not belong to the photopolymerizable compound (C). The photopolymerizable compound (C) can cause the composition (X) to undergo photocuring by having an ethylenic unsaturated group, can cause the photopolymerizable compound (C) to undergo a crosslinking reaction with each other and / or between the photopolymerizable compound (C) and the resin (A) having an ethylenic unsaturated group, and form a crosslinked structure in the exposed region of the composition (X). One or two or more kinds of the photopolymerizable compound (C) can be used.

[0072] Examples of the photopolymerizable compound (C) include monofunctional (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; difunctional (meth)acrylates such as diethylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate; trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethylene glycol di(meth)acrylate, and the like; Trifunctional (meth)acrylates such as oxylated isocyanurate tri(meth)acrylate, ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate, and ethoxylated glycerol tri(meth)acrylate; and polyfunctional (meth)acrylates such as tetrafunctional or higher-functional (meth)acrylates such as pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ε-caprolactone-modified pentaerythritol hexa(meth)acrylate.

[0073] The photopolymerizable compound (C) preferably contains a trifunctional (meth)acrylate, i.e., a compound having three (meth)acryloyl groups in one molecule. If the photopolymerizable compound (C) contains a trifunctional (meth)acrylate, a more appropriate crosslinked structure can be formed by exposure, resulting in further improvement in the developability and deep curability of the composition (X), as well as the appearance of the solder resist layer.

[0074] The proportion of the photopolymerizable compound (C) is preferably 1 to 200 parts by mass per 100 parts by mass of the resin (A). In this case, the developability and deep curability of the composition (X) can be further improved. The proportion is more preferably 5 to 150 parts by mass, further preferably 20 to 100 parts by mass, and particularly preferably 50 to 100 parts by mass.

[0075] The ratio of the photopolymerizable compound (C) to the solid content of the composition (X) is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 20% by mass.

[0076] [Epoxy resin (D)]

[0077] Epoxy resin (D) is a component that imparts thermosetting properties to the photosensitive resin composition. Epoxy resin (D) is a compound having one or more epoxy groups per molecule, preferably two or more epoxy groups per molecule. One or more epoxy resins (D) can be used.

[0078] As the epoxy resin (D), for example, a crystalline epoxy resin, an amorphous epoxy resin, or the like can be given. The "crystalline epoxy resin" refers to an epoxy resin having a melting point, and the "amorphous epoxy resin" refers to an epoxy resin not having a melting point. The melting point of the crystalline epoxy resin is, for example, 70°C to 180°C.

[0079] As the crystalline epoxy resin, for example, 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, a hydroquinone type crystalline epoxy resin (as a specific example, a product number YDC-1312 manufactured by NIPPON STEEL Chemical & Material Co., Ltd.), a biphenyl type crystalline epoxy resin (as a specific example, a product number YX-4000 manufactured by Mitsubishi Chemical Corporation), a diphenyl ether type crystalline epoxy resin (as a specific example, a product number YSLV-80DE manufactured by NIPPON STEEL Chemical & Material Co., Ltd.), a bisphenol type crystalline epoxy resin (as a specific example, a product number YSLV-70XY, YSLV-80XY manufactured by NIPPON STEEL Chemical & Material Co., Ltd.), a tetraphenylol ethane type crystalline epoxy resin (as a specific example, a product number GTR-1800 manufactured by Japan Epoxy Resin Co., Ltd.), a bisphenol fluorene type crystalline epoxy resin, or the like can be given.

[0080] As the non-crystalline epoxy resin, for example, phenol novolac type epoxy resin (as a specific example, product number EPICLON N-775 manufactured by DIC Corporation), cresol novolac type epoxy resin (as a specific example, product number EPICLON N-695 manufactured by DIC Corporation), bisphenol A novolac type epoxy resin (as a specific example, product number EPICLON N-865 manufactured by DIC Corporation), bisphenol A type epoxy resin (as a specific example, product number jER1001 manufactured by Mitsubishi Chemical Corporation), bisphenol F type epoxy resin (as a specific example, product number jER4004P manufactured by Mitsubishi Chemical Corporation), bisphenol S type epoxy resin (as a specific example, product number EPICLON EXA-1514 manufactured by DIC Corporation), bisphenol AD type epoxy resin, biphenyl novolac type epoxy resin (as a specific example, product number NC-3000 manufactured by Nippon Kayaku Co., Ltd.), hydrogenated bisphenol A type epoxy resin (as a specific example, product number ST-4000D manufactured by NIPPON STEEL Chemical & Material Co., Ltd.), naphthalene type epoxy resin (as a specific example, product numbers EPICLON HP-4032, EPICLON HP-4700, EPICLON HP-4770 manufactured by DIC Corporation), t-butyl catechol type epoxy resin (as a specific example, product number EPICLON HP-820 manufactured by DIC Corporation), dicyclopentadiene type epoxy resin (as a specific example, product number EPICLON HP-7200 manufactured by DIC), adamantane type epoxy resin (as a specific example, product number ADAMANTATE X-E-201 manufactured by Asahi Denka Kogyo Co., Ltd.), special difunctional type epoxy resin (as a specific example, product numbers YL7175-500, YL7175-1000 manufactured by Mitsubishi Chemical Corporation; product numbers EPICLON TSR-960, EPICLON TER-601, EPICLON TSR-250-80BX, EPICLON 1650-75MPX, EPICLON EXA-4850, EPICLON EXA-4816, EPICLON EXA-4822, EPICLON EXA-9726 manufactured by DIC Corporation; product number YSLV-120TE manufactured by NIPPON STEEL Chemical & Material Co., Ltd.), rubber-like core-shell polymer modified bisphenol A type epoxy resin (as a specific example, product number MX-156 manufactured by Kaneka Corporation), rubber-like core-shell polymer modified bisphenol F type epoxy resin (as a specific example, product number MX-136 manufactured by Kaneka Corporation), and the like can be given.

[0081] The epoxy resin (D) preferably contains a crystalline epoxy resin. In this case, the developability and the deep curing property of the composition (X) can be further improved.

[0082] The epoxy equivalent of the epoxy resin (D) is, for example, 50 g / eq to 500 g / eq, preferably 80 g / eq to 250 g / eq. The "epoxy equivalent" means the mass of an epoxy resin having 1 gram equivalent of an epoxy group.

[0083] The equivalent of the epoxy group possessed by the epoxy resin (D) is preferably 0.7 times to 2.5 times, more preferably 0.7 times to 2.3 times, further preferably 0.7 times to 2.0 times, relative to the equivalent of the carboxyl group possessed by the resin (A).

[0084] The proportion of the epoxy resin (D) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 5 parts by mass or more, particularly preferably 10 parts by mass or more, relative to 100 parts by mass of the resin (A). In this case, the heat curing property of the composition (X) can be further improved, and as a result, the developability and the deep curing property can be further improved. The proportion is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, further preferably 40 parts by mass or less, particularly preferably 30 parts by mass or less. In this case, the appearance of the solder resist layer can be further improved.

[0085] The proportion of the epoxy resin (D) is preferably 1% by mass to 30% by mass, more preferably 2% by mass to 20% by mass, further preferably 3% by mass to 15% by mass, relative to the solid content of the composition (X).

[0086] [Titanium oxide (E)]

[0087] The titanium oxide (E) is an oxide of titanium, and examples thereof include TiO2, TiO, Ti n O 2n－1 (n = 4 to 9), Ti2O5, Ti2O3, and the like, and TiO2 (titania) is preferred. One or two or more kinds of titanium oxides (E) can be used.

[0088] As the titanium oxide (E), for example, rutile-type titanium oxide, anatase-type titanium oxide, and orthorhombic titanomorphite can be mentioned. One or two or more kinds of titanium oxides (E) can be used.

[0089] Rititanium Oxide Co., Ltd. : product number R-25, R-21, R-32, R-7E, R-5N, R-61N, R-62N, R-42, R-45M, R-44, R-49S, R-79, GTR-100, GTR-300, D-918, TCR-29, TCR-52, FTR-700, Ishihara Sangyo Kaisha, Ltd. : product number R-550, R-580, R-630, R-820, CR-50, CR-58, CR-60, CR-90, CR-97, CR-953, Fuji Titanium Industry Co., Ltd. : product number TR-600, TR-700, TR-750, TR-840, Titan Kogyo Co., Ltd. : product number KR-270, KR-310, KR-380, and the like.

[0090] Rititanium Oxide Co., Ltd. : product number A-110, TCA-123E, A-190, A-197, SA-1, SA-1L, Ishihara Sangyo Kaisha, Ltd. : product number A-100, A-220, W-10, Fuji Titanium Industry Co., Ltd. : product number TA-100, TA-200, TA-300, TA-400, TA-500, TP-2, Tayca Co., Ltd. : product number JA-1, JA-3, JA-4, JA-5, JA-C, Titan Kogyo Co., Ltd. : KA-10, KA-15, KA-20, KA-30, and the like.

[0091] Rititanium Oxide Co., Ltd. : product number A-110, TCA-123E, A-190, A-197, SA-1, SA-1L, Ishihara Sangyo Kaisha, Ltd. : product number A-100, A-220, W-10, Fuji Titanium Industry Co., Ltd. : product number TA-100, TA-200, TA-300, TA-400, TA-500, TP-2, Tayca Co., Ltd. : product number JA-1, JA-3, JA-4, JA-5, JA-C, Titan Kogyo Co., Ltd. : KA-10, KA-15, KA-20, KA-30, and the like. 0.5 TiO2.

[0092] The titanium oxide (E) is usually in a particulate form. As the shape of the particles of the titanium oxide (E), for example, there can be mentioned a plate shape, a spherical shape, a needle shape, an amorphous shape, and the like. The average particle diameter of the titanium oxide (E) is, for example, 10 μm or less, preferably 0.001 μm to 10 μm, and more preferably 0.01 μm to 5 μm.

[0093] The titanium oxide (E) preferably contains a rutile-type titanium oxide. In this case, the heat resistance of the composition (X) can be further improved, and as a result, the heat yellowing resistance of the solder resist layer can be further improved.

[0094] It is important that the proportion of titanium oxide (E) in the composition (X) is 20 parts by mass or more relative to 100 parts by mass of the resin (A). By making the proportion of titanium oxide (E) the above or more, the composition (X) can improve the reflectance. The proportion is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, further preferably 70 parts by mass or more, and particularly preferably 90 parts by mass or more. The upper limit of the proportion of titanium oxide (E) is not particularly limited, and is, for example, 300 parts by mass or less, preferably 250 parts by mass or less, and more preferably 200 parts by mass or less, relative to 100 parts by mass of the resin (A).

[0095] The proportion of titanium oxide (E) is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and particularly preferably 20% by mass or more, relative to the solid content of the composition (X). The upper limit of the proportion of titanium oxide (E) is not particularly limited, and is, for example, 50% by mass or less, and preferably 40% by mass or less.

[0096] [Antioxidant (F)]

[0097] The antioxidant is a component that contributes to the improvement of the heat discoloration resistance of the solder resist layer. The composition (X) can further improve the heat yellowing resistance of the solder resist layer by containing the antioxidant (F). The composition (X) can use one or two or more as the antioxidant (F).

[0098] As the antioxidant (F), for example, a hindered phenol-based antioxidant such as pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and the like; a hindered amine-based antioxidant such as tetra (1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, and the like; a phosphorus-based antioxidant such as bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, and the like; a sulfur-based antioxidant such as 2,2-bis{〔3-(dodecylthio)-1-oxopropoxy〕methyl}propane-1,3-diyl bis (3-(dodecylthio)propionate), and the like, and the like can be given.

[0099] The antioxidant (F) preferably contains a hindered phenol-based antioxidant. The antioxidant (F) can further improve the heat yellowing resistance of the solder resist layer by containing the hindered phenol-based antioxidant.

[0100] The melting point of the antioxidant (F) is preferably 50°C to 150°C. In this case, bleeding of the antioxidant from the solder resist layer and precipitation of crystals of the antioxidant are inhibited, and the uniformity of the surface of the solder resist layer is improved. As such an antioxidant (F), for example, product number Irganox 1010 (melting point 110 to 125°C) manufactured by BASF Corporation, product number ADK STAB AO-60 (110 to 130°C) manufactured by ADEKA Corporation, and the like can be given.

[0101] The proportion of the antioxidant (F) with respect to the solid content of the composition (X) is, for example, 0.01 to 3 mass%, and preferably 0.1 to 1.5 mass%.

[0102] [Dispersant (G)]

[0103] The dispersant (G) is a component for further improving the dispersibility of the particles in the composition. As the dispersant (G), for example, a high-molecular dispersant having a functional group, and the like can be given. As the functional group, for example, an acidic functional group such as a phosphoric acid group, a carboxyl group, a sulfonic acid group, and the like; a base of these acidic functional groups; a primary, secondary, or tertiary amino group; a quaternary ammonium base; a group derived from a nitrogen-containing aromatic heterocycle such as pyridine, pyrimidine, pyrazine, and the like; and the like can be given. As the functional group possessed by the dispersant (G), a phosphoric acid group is preferred. The dispersant (G) further improves the dispersibility of the titanium oxide (E) in the composition (X) by having a phosphoric acid group, and is capable of further improving the developability, the deep curing property, and the appearance of the solder resist layer of the composition (X). When the dispersant (G) has an acidic functional group, the acid value of the dispersant (G) is, for example, 50 to 200 mgKOH / g. One or two or more kinds of the dispersant (G) can be used in the composition (X).

[0104] The proportion of the dispersant (G) with respect to the solid content of the composition (X) is, for example, 0.01 to 5 mass%, and preferably 0.1 to 2 mass%.

[0105] [Other component (H)]

[0106] As the other component (H), for example, melamine or a derivative thereof, an antifoaming agent, a curing agent, a curing accelerator, barium sulfate, silica, talc, bentonite, calcium carbonate, barium titanate, aluminum hydroxide, and the like inorganic filler other than the titanium oxide (E), a coupling agent such as a silane coupling agent, a surfactant, a leveling agent, a thixotropic agent, an anti-halo agent, a flame retardant, a solvent, and the like can be given. One or two or more kinds of the other component (H) can be used in the composition (X).

[0107] (Melamine or a derivative thereof)

[0108] The composition (X) can further improve adhesion between the cured product of the composition (X) and metals such as copper by containing at least one of melamine and a melamine derivative. In this case, the composition (X) can be particularly suitable for use as an insulating material for a printed wiring board. In addition, the plating resistance of the cured product of the composition (X), that is, the whitening resistance during electrolytic nickel / gold plating treatment is improved.

[0109] Melamine is 2,4,6-triamino-l,3,5-triazine. As the melamine derivative, for example, a compound having one triazine ring and an amino group in one molecule, etc. can be given, and specifically, for example, guanamine; methylguanamine; benzoguanamine; 2,4-diamino-6-methacryloyloxyethyl s-triazine, 2-vinyl-4,6-diamino-s-triazine, 2-vinyl-4,6-diamino-s-triazine • isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl s-triazine • isocyanuric acid adduct, and the like s-triazine derivatives; reaction products of melamine and anhydride such as melamine-tetrahydrophthalic acid salt, and the like can be given. When the composition (X) contains melamine or a derivative thereof, the ratio of melamine and the derivative thereof with respect to the solid content of the composition (X) is, for example, 0.01 to 5% by mass, and preferably 0.1 to 2% by mass.

[0110] (Antifoaming agent)

[0111] As the antifoaming agent, for example, a silicone-based antifoaming agent such as product number KS-66 manufactured by Shin-Etsu Chemical Co., Ltd.; a non-silicone-based antifoaming agent such as product number FOAM KILLER NSI-0.00 manufactured by Aoki Oil & Fat Co., Ltd.; and the like can be given. When the composition (X) contains an antifoaming agent, the ratio of the antifoaming agent with respect to the solid content of the composition (X) is, for example, 0.001 to 2% by mass, and preferably 0.01 to 1% by mass.

[0112] (Solvent)

[0113] The composition (X) can contain a solvent. The composition (X) is more easily prepared by containing a solvent. The solvent is not particularly limited, and for example, an organic solvent such as a glycol ether such as dipropylene glycol monomethyl ether, and the like can be given, and a reaction solvent used in the synthesis of the resin (A) can also be directly used as the solvent of the composition (X). When the composition (X) contains a solvent, the ratio of the solvent with respect to the entire composition (X) is, for example, 1 to 80% by mass, and preferably 5 to 40% by mass.

[0114] The composition (X) can be prepared by compounding the raw materials of the composition (X) as described above, and mixing, etc. using a publicly known mixing method using, for example, a three-roll mill, a ball mill, a sand mill, and the like.

[0115] <Dry film>

[0116] The dry film of the present embodiment contains the above-mentioned composition (X), specifically, a dried coating film of the composition (X). The dry film of the present embodiment can be formed by applying the composition (X) to, for example, a base film, drying the resulting wet coating film, and removing the solvent or the like, and is obtained in the form of a dry film with the base film. As the base film, for example, a polyethylene terephthalate (PET) film or the like can be mentioned. As the method of applying the composition (X), for example, a dipping method, a spray method, a spin coating method, a roll coating method, a curtain coating method, a screen printing method, or the like can be mentioned. As the temperature at the time of drying, for example, 50°C to 120°C is mentioned. As the drying time, for example, 1 minute to 2 hours is mentioned. The thickness of the dry film is, for example, 1 μm to 100 μm.

[0117] The dry film of the present embodiment can be suitably used as an electrically insulating material for a printed wiring board, and particularly, can be suitably used for forming an electrically insulating layer such as a solder resist layer, a plating resist layer, a resist layer, an interlayer insulating layer, or the like.

[0118] < Solder resist >

[0119] The solder resist of the present embodiment contains a cured product of the above-mentioned composition (X), specifically, a cured film of the composition (X). The solder resist of the present embodiment can be formed, for example, by applying the composition (X) to at least a part of the surface of a substrate such as a printed wiring board, and then thermally curing the resulting coating layer. As the method of thermally curing the composition (X), for example, a heating method or the like can be mentioned. As the heating temperature, for example, 100°C to 250°C, preferably 120°C to 200°C is mentioned. As the heating time, for example, 1 minute to 10 hours, preferably 10 minutes to 3 hours is mentioned. In the formation of the solder resist, light curing and development can be performed before thermal curing. The thickness of the solder resist is, for example, 1 μm to 100 μm.

[0120] < Printed wiring board >

[0121] The printed wiring board of the present embodiment is provided with a solder resist layer containing a cured product of the above-mentioned composition (X). The printed wiring board of the present embodiment can be formed, for example, by forming a solder resist layer on a printed wiring board. The solder resist layer can be formed, for example, by applying the composition (X) to a printed wiring board (coating step), light curing at least a part of the resulting coating layer by irradiating the coating layer with active energy rays after the light curing step (light curing step), then removing the unexposed part of the coating layer by development (development step), and then thermally curing the coating layer after the development step (thermal curing step). Note that, light curing can be further performed after the development step or the thermal curing step, or after both the development step and the thermal curing step.

[0122] The irradiation of active energy rays can be performed, for example, in a state of directly abutting against the negative mask, or can be performed by a method other than the method using the negative mask, for example, the coated layer can be exposed by a direct drawing method of irradiating active energy rays emitted from a light source only on a portion of the coated layer to be exposed. As the active energy rays for the irradiation, for example, ultraviolet rays, visible rays, near infrared rays, and the like can be mentioned, which are appropriately selected in accordance with the composition of the composition (X) or the like. The active energy rays are preferably ultraviolet rays. The light source of the ultraviolet rays is selected from, for example, a chemical fluorescent lamp, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a YAG laser, an LED, a xenon lamp, and a metal halide lamp. The exposure amount of the active energy rays is, for example, 10 mJ / cm 2 ~ 5000 mJ / cm 2 , preferably 100 mJ / cm 2 ~ 800 mJ / cm 2 When the cured film is produced from the dry film, the dry film can be exposed, for example, after the support is peeled off from the dry film in advance. Note that the dry film can also be exposed by irradiating the dry film with ultraviolet rays through the support in a state where the support is overlapped on the dry film, and then peeling the support from the exposed dry film.

[0123] The developer used for the development can be appropriately selected from, for example, an aqueous solution of an alkali such as sodium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide, or the like; a solution of an organic amine such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, or the like; and the like, in accordance with the composition of the composition (X) or the like.

[0124] The heat curing is performed, for example, by heating the coated layer after the development. The heating temperature is, for example, 100°C to 250°C, preferably 120°C to 200°C. The heating time is, for example, 1 minute to 10 hours, preferably 10 minutes to 3 hours, more preferably 20 minutes to 120 minutes.

[0125] The thickness of the solder resist layer is, for example, 1 μm to 100 μm. As described above, the printed wiring board having the solder resist layer containing the cured product of the composition (X) can be produced.

[0126] Example

[0127] Hereinafter, the present application will be specifically described by examples, but the present application is not limited to the examples.

[0128] Preparation of Carboxyl Group-Containing Resin Solution

[0129] (1) Synthesis Example 1

[0130] In a four-necked flask equipped with a reflux condenser, a thermometer, a glass tube for nitrogen replacement, and a stirrer, 38.5 parts by mass of methacrylic acid, 51.5 parts by mass of methyl methacrylate, 10 parts by mass of styrene, 160 parts by mass of dipropylene glycol monomethyl ether, and 6 parts by mass of azobisisobutyronitrile were charged. The liquid in the four-necked flask was heated at 75°C for 5 hours under a stream of nitrogen to carry out a polymerization reaction, whereby a copolymer solution having a concentration of 40% by mass was obtained.

[0131] To the copolymer solution, 0.05 parts by mass of Metokinon, 34 parts by mass of glycidyl methacrylate, and 0.4 parts by mass of dimethylbenzylamine were added, and an addition reaction was carried out at 80°C for 24 hours. Thus, a 47% by mass solution of a vinyl polymer having a carboxyl group-containing residue and an ethylenic unsaturated group in a side chain, i.e., a carboxyl group-containing resin A, was obtained. The weight average molecular weight of the carboxyl group-containing resin A was 24300. In addition, the carboxyl group-containing resin A did not have an oligomer fraction having a molecular weight of 450 to 1000.

[0132] (2) Synthesis Example 2

[0133] In a four-necked flask equipped with a reflux condenser, a thermometer, a glass tube for nitrogen replacement, and a stirrer, 38.5 parts by mass of methacrylic acid, 51.5 parts by mass of methyl methacrylate, 10 parts by mass of styrene, 160 parts by mass of dipropylene glycol monomethyl ether, and 6 parts by mass of azobisisobutyronitrile were charged. The liquid in the four-necked flask was heated at 75°C for 5 hours under a stream of nitrogen to carry out a polymerization reaction, whereby a copolymer solution having a concentration of 40% by mass was obtained.

[0134] To the copolymer solution, 0.05 parts by mass of Metokinon, 34 parts by mass of glycidyl methacrylate, and 0.4 parts by mass of dimethylbenzylamine were added, and an addition reaction was carried out at 80°C for 24 hours. Thus, a 47% by mass solution of a vinyl polymer having a carboxyl group-containing residue and an ethylenic unsaturated group in a side chain, i.e., a carboxyl group-containing resin A, was obtained. The weight average molecular weight of the carboxyl group-containing resin A was 24300. In addition, the carboxyl group-containing resin A did not have an oligomer fraction having a molecular weight of 450 to 1000.

[0135] (3) Synthesis Example 3

[0136] In a four-necked flask equipped with a reflux condenser, a thermometer, a glass tube for nitrogen replacement, and a stirrer, 38.5 parts by mass of methacrylic acid, 51.5 parts by mass of methyl methacrylate, 10 parts by mass of styrene, 160 parts by mass of dipropylene glycol monomethyl ether, and 6 parts by mass of azobisisobutyronitrile were charged. The liquid in the four-necked flask was heated at 75°C for 5 hours under a stream of nitrogen to carry out a polymerization reaction, whereby a copolymer solution having a concentration of 40% by mass was obtained.

[0137] To the copolymer solution was added Metokinon 0.05 parts by mass, glycidyl methacrylate 34 parts by mass, and dimethylbenzylamine 0.4 parts by mass, and an addition reaction was performed by heating at 80°C for 24 hours. Thus, a 51% by mass solution of a vinyl polymer having a carboxyl group-containing residue and having an ethylenically unsaturated group in a side chain, i.e., a carboxyl group-containing resin C, was obtained. The weight average molecular weight of the carboxyl group-containing resin C was 3884. In addition, the carboxyl group-containing resin C had an oligomer portion having a molecular weight of 450 to 1000.

[0138] (4) Synthesis Example 4

[0139] In a four-necked flask equipped with a reflux condenser, a thermometer, a glass tube for nitrogen replacement, and a stirrer, were placed methacrylic acid 38.5 parts by mass, methyl methacrylate 51.5 parts by mass, styrene 10 parts by mass, α-methylstyrene dimer 20 parts by mass, dipropylene glycol monomethyl ether 195 parts by mass, and azobisisobutyronitrile 22.5 parts by mass. The liquid in the four-necked flask was heated at 75°C for 5 hours under a stream of nitrogen to perform a polymerization reaction, thus obtaining a copolymer solution having a concentration of 42% by mass.

[0140] To the copolymer solution was added Metokinon 0.05 parts by mass, glycidyl methacrylate 34 parts by mass, and dimethylbenzylamine 0.4 parts by mass, and an addition reaction was performed by heating at 80°C for 24 hours. Thus, a 51% by mass solution of a vinyl polymer having a carboxyl group-containing residue and having an ethylenically unsaturated group in a side chain, i.e., a carboxyl group-containing resin C, was obtained. The weight average molecular weight of the carboxyl group-containing resin C was 3884. In addition, the carboxyl group-containing resin C had an oligomer portion having a molecular weight of 450 to 1000.

[0141] Preparation of the photosensitive resin composition

[0142] A mixture obtained by compounding the components shown in Table 1 described later was mixed with a triple roll mill to obtain a photosensitive resin composition. Note that the details of the components shown in Table 1 are as follows.

[0143] - photopolymerization initiator (B):

[0144] • Photopolymerization initiator A: acyloxyphosphine-based, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by BASF Corporation, product number Irgacure 819.

[0145] • Photopolymerization initiator B: acyloxyphosphine-based, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by BASF Corporation, product number Irgacure TPO.

[0146] • Photopolymerization initiator C: α-hydroxyalkyl phenone type, 2-hydroxy-2-methyl-l-phenyl-propane-l-one, manufactured by BASF Corporation, product number Irgacure 1173.

[0147] • Photopolymerization initiator D: α-hydroxyalkyl phenone type, 1-hydroxy- cyclohexyl-phenyl-ketone, manufactured by BASF Corporation, product number Irgacure 184.

[0148] - Photopolymerizable compound (C):

[0149] • Photopolymerizable compound A: trimethylolpropane triacrylate (TMPTA).

[0150] • Photopolymerizable compound B: mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (manufactured by Nippon Shokubai Co., Ltd., product number KAYARAD DPHA).

[0151] - Epoxy resin (D):

[0152] • Epoxy resin A: crystalline epoxy compound, 1,3,5-tris(2,3-epoxypropyl)-l,3,5- triazine-2,4,6(lH,3H,5H)-trione (high melting point type) (TEPIC-HB), epoxy equivalent 99 g / eq.

[0153] • Epoxy resin B: crystalline epoxy compound, hydroquinone type crystalline epoxy resin, manufactured by NIPPON STEEL Chemical & Material Co., Ltd., product number YDC-1312, epoxy equivalent 176 g / eq.

[0154] • Epoxy resin C: amorphous epoxy compound, hydrogenated bisphenol A type liquid epoxy resin, manufactured by NIPPON STEEL Chemical & Material Co., Ltd., product number ST-3000, epoxy equivalent 230 g / eq.

[0155] - Titanium oxide (E):

[0156] • Titanium oxide A: rutile type titanium oxide manufactured by sulfuric acid method, manufactured by KAKI CHEMICAL CO., LTD., product number R-79.

[0157] • Titanium oxide B: rutile type titanium oxide manufactured by chlorine method, manufactured by Ishihara Sangyo Kaisha, Ltd., product number CR-90.

[0158] - Antioxidant (F):

[0159] • Antioxidant: hindered phenol type, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4- hydroxyphenyl) propionate], manufactured by BASF Corporation, product number Irganox 1010.

[0160] - dispersant (G):

[0161] • Dispersant: Phosphate ester-based pigment dispersant, manufactured by BYK Chemie Co., Ltd., product number BYK-111 (liquid organic compound having 2 phosphate groups (phosphate ester compound having phosphate groups at both terminals of a copolymer), acid value 129 mgKOH / g, nonvolatile content 95%.

[0162] - other ingredients (H)

[0163] • Melamine: manufactured by Nissan Chemical Industries, Ltd., fine powder melamine.

[0164] • Defoaming agent: manufactured by Shin-Etsu Silicone Co., Ltd., product number KS-66.

[0165] < Evaluation Test >

[0166] (1) Preparation of test piece

[0167] A glass epoxy copper-clad laminate having a copper foil with a thickness of 35 μm was prepared. The glass epoxy copper-clad laminate was subjected to etching to form a conductor wiring, thereby obtaining a printed wiring board. A photosensitive resin composition was applied to the entire surface of the printed wiring board by screen printing, thereby obtaining a coating film. The coating film was dried by heating at 80°C for 20 minutes. The thickness of the coating film on the dried copper foil (dried coating film) was 20 μm. In a state where a negative mask was directly abutted against the surface of the dried coating film, the dried coating film was selectively exposed to ultraviolet rays under conditions of an exposure amount of 400 mJ / cm 2 After the negative mask was removed from the dried coating film, the dried coating film was subjected to a development treatment using a 1 mass% sodium carbonate aqueous solution at 30°C for 60 seconds, thereby leaving the portion of the dried coating film that was cured by exposure as a solder resist layer on the printed wiring board. The solder resist layer was further heat-cured by heating at 150°C for 60 minutes. Thereby, a test piece having a solder resist layer was obtained.

[0168] The test piece was subjected to the following evaluation test.

[0169] (2) Development property (break point)

[0170] The development was performed using a 1 mass% sodium carbonate aqueous solution at 30°C at a spraying pressure of 0.2 MPa for 90 seconds, and the development property (break point) was evaluated in accordance with the following evaluation criteria.

[0171] A: Break point (time required for development of the dried coating film) was greater than 0 seconds and was 20 seconds or less, and there was no un-developed portion.

[0172] B: Break point was greater than 20 seconds and was 40 seconds or less, and there was no un-developed portion.

[0173] C: Break point is greater than 40 seconds and is 60 seconds or less, and there is no unexposed portion.

[0174] D: Break point is greater than 60 seconds, and there is no unexposed portion.

[0175] E: There is an unexposed portion.

[0176] (3) Developability (Drying Range)

[0177] In evaluating the developability (drying range) of the photosensitive resin composition, a test piece for developability (drying range) evaluation different from the above-described test piece was prepared. First, a wet coating film was formed on the printed wiring board by the same method as described above. Then, the wet coating film was heated at a heating temperature of 80°C for a heating time of 20 minutes, 40 minutes, 60 minutes, and 80 minutes to form a dry coating film. The dry coating film thus formed had a thickness of 20 μm. The dry coating film after the preliminary drying was subjected to a development treatment for 90 seconds with a 1 mass% sodium carbonate aqueous solution at 30°C at a spraying pressure of 0.2 MPa. The coating film after the development treatment was observed, and the developability (drying range) was evaluated in accordance with the following evaluation criteria.

[0178] A: The coating film dried at a heating temperature of 80°C for a heating time of 80 minutes was developable.

[0179] B: The coating film dried at a heating temperature of 80°C for a heating time of 60 minutes was developable, but a development residue was confirmed for the coating film dried at a heating temperature of 80°C for a heating time of 80 minutes.

[0180] C: The coating film dried at a heating temperature of 80°C for a heating time of 40 minutes was developable, but a development residue was confirmed for the coating film dried at a heating temperature of 80°C for a heating time of 60 minutes.

[0181] D: The coating film dried at a heating temperature of 80°C for a heating time of 20 minutes was developable, but a development residue was confirmed for the coating film dried at a heating temperature of 80°C for a heating time of 40 minutes.

[0182] E: A development residue was confirmed for the coating film dried at a heating temperature of 80°C for a heating time of 20 minutes.

[0183] (4) Deep Curing Property (Solder Bridge Residue Evaluation)

[0184] A printed wiring board having a conductor pattern of copper with a line width / line space of 0.2 mm / 0.3 mm and a thickness of 40 μm was prepared. In addition, a negative mask having a mask pattern for forming solder dams with widths of 30 μm, 40 μm, 50 μm, and 60 μm was used. Except for using these printed wiring boards and the negative mask, solder dams with a thickness of 60 μm were formed on the printed wiring boards under the same conditions as in the case of producing the above-described test pieces.

[0185] The solder dams were subjected to a glassine tape peeling test, whereby the minimum width of the solder dam that did not peel and remained on the printed wiring board was analyzed, and the deep curing property was evaluated in accordance with the following evaluation criteria.

[0186] A: The minimum width of the remaining solder dam was 30 μm.

[0187] B: The minimum width of the remaining solder dam was 40 μm.

[0188] C: The minimum width of the remaining solder dam was 50 μm.

[0189] D: The minimum width of the remaining solder dam was 60 μm.

[0190] E: No solder dam remained.

[0191] (5) Reflectance

[0192] The Y value in the CIE colorimetric system representing visual reflectance of the solder resist layer on the copper foil of the just-produced test piece was measured with a spectrophotometer (Model CM-600d) manufactured by Konica Minolta Sensing, Inc., and the reflectance was evaluated in accordance with the following evaluation criteria. The value of the reflectance is shown in parentheses in Table 1 together with the evaluation (A to E).

[0193] A: The Y value was 85 or greater.

[0194] B: The Y value was 80 or greater but less than 85.

[0195] C: The Y value was 75 or greater but less than 80.

[0196] D: The Y value was 70 or greater but less than 75.

[0197] E: The Y value was less than 70.

[0198] (6) Appearance

[0199] The solder resist coating surface on the copper foil of the test piece was observed. Furthermore, the specular glossiness of the coating surface at an incident angle of 60°, as determined in accordance with JIS-Z8741, was measured using a "GLOSS CHECKER" manufactured by Horiba, Ltd. Appearance was evaluated according to the following evaluation criteria. In Table 1, the gloss values ​​are shown in parentheses along with the evaluations (A to E).

[0200] A: No wrinkles are generated on the coating surface, and the gloss value is 80 or higher.

[0201] B: No wrinkles are generated on the coating film surface, and the gloss value is 75 or more and less than 80.

[0202] C: No wrinkles are generated on the coating film surface, and the gloss value is 70 or more and less than 75.

[0203] D: No wrinkles are generated on the coating surface, and the gloss value is less than 70.

[0204] E: Wrinkles are generated on the coating film surface.

[0205] (7) Heat yellowing resistance

[0206] The L value of the solder resist layer of the test piece just made was measured using a spectrophotometer (model CM-600d) manufactured by Konica Minolta Sensing. ＊ a ＊ b ＊ b in the color system ＊ Next, the test piece was heat treated at 250°C for 5 minutes, and the b value of the solder resist layer was measured again. ＊ Calculate the b value of the solder mask after heat treatment. ＊ The value minus the b value of the solder mask before heat treatment ＊ The value obtained by ＊ ), and based on the results, the heat yellowing resistance was evaluated according to the following evaluation criteria.

[0207] A: Δb ＊ The value is less than 1.5.

[0208] B: Δb ＊ The value is 1.5 or more and less than 2.0.

[0209] C:Δb ＊ The value is greater than or equal to 2.0 and less than 2.5.

[0210] D: Δb ＊ The value is 2.5 or more and less than 3.0.

[0211] E:Δb ＊ The value is 3.0 or above.

[0212] (8) Storage stability

[0213] The photosensitive resin composition was stored at 4°C in a refrigerator for 3 days, 7 days, 10 days, and 14 days. Next, the photosensitive resin composition was coated on a glass plate at a film thickness of 20 μm, and the coated film was visually observed, and the storage stability was evaluated according to the following evaluation criteria.

[0214] A: No substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 14 days.

[0215] B: No substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 10 days, but substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 14 days.

[0216] C: No substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 7 days, but substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 10 days.

[0217] D: No substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 3 days, but substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 7 days.

[0218] E: Substance (fine particles) was found in the coated film of the photosensitive resin composition stored at 4°C for 3 days.

[0219] [Table 1]

[0220]

[0221] According to the results of Table 1, it was shown that the photosensitive resin compositions of Examples 1 to 14 could improve the developability and the deep curing property, and in addition, could improve the appearance and the reflectance of the solder resist layer formed from the photosensitive resin composition. On the other hand, it was also shown that the photosensitive resin compositions of Comparative Examples 1 and 2, which contained the carboxyl group-containing resin without the oligomer portion, had poor deep curing property, and in addition, the photosensitive resin compositions of Comparative Examples 3 and 4, in which the weight average molecular weight of the carboxyl group-containing resin was outside the prescribed range, had poor deep curing property and appearance of the solder resist layer.

[0222] (Summary)

[0223] The photosensitive resin composition according to the first aspect contains a carboxyl group-containing resin (A), a photopolymerization initiator (B), a photopolymerizable compound (C), an epoxy resin (D), and titanium oxide (E). The carboxyl group-containing resin (A) contains a vinyl polymer having a carboxyl group-containing residue and an ethylenically unsaturated group in a side chain, has a weight average molecular weight of 10,000 to 100,000, and contains an oligomer fraction having a molecular weight of 450 to 1,000. The proportion of titanium oxide (E) is 20 parts by mass or more relative to 100 parts by mass of the carboxyl group-containing resin (A).

[0224] According to the first aspect, by making the proportion of titanium oxide (E) the above value or more, making the Mw of the carboxyl group-containing resin (A) the above range, and making the carboxyl group-containing resin (A) contain an oligomer fraction having a molecular weight of 450 to 1,000, the dispersibility of titanium oxide (E) is further improved, whereby the reflectance and gloss of the solder resist layer are improved. In addition, the properties of the solder resist layer such as the curing property are more uniform, the thermal curing property is more uniform, the breaking point is shorter, the allowable range of the drying time is wider, and the development property is improved. Furthermore, the photocuring property of the solder resist layer is more uniform, the balance between the surface curing and the deep curing is better, whereby the generation of wrinkles of the solder resist layer is suppressed, and the appearance is improved. Thus, even if the photosensitive resin composition contains titanium oxide, the development property and the deep curing property can be improved, and the appearance and the reflectance of the solder resist layer can be improved.

[0225] The photosensitive resin composition according to the second aspect is such that, in the first aspect, the proportion of the area of the oligomer fraction relative to the total area of 100% of the carboxyl group-containing resin (A) is 0.1% to 3% as measured by gel permeation chromatography using a differential refractive index detector.

[0226] According to the second aspect, the deep curing property of the photosensitive resin composition and the heat yellowing resistance of the solder resist layer can be further improved.

[0227] The photosensitive resin composition according to the third aspect is such that, in the first or second aspect, at least a part of the carboxyl group-containing resin (A) is a product of a polymerization reaction using a chain transfer agent.

[0228] According to the third aspect, the Mw of the resulting polymer can be made smaller, and as a result, the proportion of the oligomer fraction in the carboxyl group-containing resin (A) can be made larger.

[0229] The photosensitive resin composition according to the fourth aspect is such that, in the third aspect, the chain transfer agent contains an α-methylstyrene dimer.

[0230] According to the fourth aspect, by using an unsaturated hydrocarbon compound as the chain transfer agent, an ethylenically unsaturated group can be introduced to the terminal of the carboxyl group-containing resin (A) and the oligomer contained therein.

[0231] The photosensitive resin composition of the fifth mode further contains an antioxidant (F) in any one of the first to fourth modes.

[0232] According to the fifth mode, the heat yellowing resistance of the solder resist layer can be further improved.

[0233] The photosensitive resin composition of the sixth mode contains a hindered phenol-based antioxidant in the fifth mode.

[0234] According to the sixth mode, the heat yellowing resistance of the solder resist layer can be further improved.

[0235] The photosensitive resin composition of the seventh mode further contains a dispersant (G) in any one of the first to sixth modes.

[0236] According to the seventh mode, the dispersibility of the particles in the photosensitive resin composition can be further improved.

[0237] The photosensitive resin composition of the eighth mode has the dispersant (G) having a phosphoric acid group in the seventh mode.

[0238] According to the eighth mode, the dispersibility of the titanium oxide (E) in the photosensitive resin composition is further improved, and the developability, the deep curing property of the photosensitive resin composition, and the appearance of the solder resist layer can be further improved.

[0239] The photosensitive resin composition of the ninth mode contains an acyloxyphosphine-based photopolymerization initiator in any one of the first to eighth modes.

[0240] According to the ninth mode, the developability and the deep curing property of the photosensitive resin composition can be further improved.

[0241] The photosensitive resin composition of the tenth mode further contains an α-hydroxyalkylphenone-based photopolymerization initiator in the ninth mode.

[0242] According to the tenth mode, the developability and the deep curing property of the photosensitive resin composition can be further improved, and the surface curing property can be improved, and since the solubility of the photopolymerization initiator is improved, the storage stability of the photosensitive resin composition can be further improved.

[0243] The photosensitive resin composition of the eleventh mode contains a trifunctional (meth)acrylate in any one of the first to tenth modes.

[0244] According to the eleventh mode, a more appropriate crosslinked structure can be formed by exposure, and as a result, the developability and the deep curing property of the photosensitive resin composition, and the appearance of the solder resist layer can be further improved.

[0245] The photosensitive resin composition of the twelfth aspect is any one of the first to eleventh aspects, and the epoxy resin (D) contains a crystalline epoxy resin.

[0246] According to the twelfth aspect, the developability and the deep curing property of the photosensitive resin composition can be further improved.

[0247] The photosensitive resin composition of the thirteenth aspect is any one of the first to twelfth aspects, and the titanium oxide (E) contains a rutile-type titanium oxide.

[0248] According to the thirteenth aspect, the heat resistance of the photosensitive resin composition can be further improved, and as a result, the heat yellowing resistance of the solder resist layer can be further improved.

[0249] The dry film of the fourteenth aspect contains the photosensitive resin composition of any one of the first to thirteenth aspects.

[0250] According to the fourteenth aspect, the developability and the deep curing property of the dry film can be improved, and the appearance and the reflectance of the solder resist layer obtained by curing the dry film can be improved. Therefore, the dry film can be suitably used as an electrically insulating material for a printed wiring board, and in particular, can be suitably used for forming an electrically insulating layer such as a solder resist layer, a solder plating resist layer, a resist layer, an interlayer insulating layer, and the like.

[0251] The solder resist of the fifteenth aspect contains a cured product of the photosensitive resin composition of any one of the first to thirteenth aspects.

[0252] According to the fifteenth aspect, the appearance and the reflectance of the solder resist layer can be improved.

[0253] The printed wiring board of the sixteenth aspect has a solder resist layer containing a cured product of the photosensitive resin composition of any one of the first to thirteenth aspects.

[0254] According to the sixteenth aspect, the appearance and the reflectance of the solder resist layer can be improved, and as a result, the performance of the printed wiring board can be improved.

Claims

1. A photosensitive resin composition comprising: a carboxyl group-containing resin A, a photopolymerization initiator B, a photopolymerizable compound C, an epoxy resin D, and titanium oxide E, wherein the carboxyl group-containing resin A contains a vinyl polymer having a carboxyl group-containing residue and an ethylenically unsaturated group in a side chain, has a weight average molecular weight of 10,000 to 100,000, and contains an oligomer portion having a molecular weight of 450 to 1,000, wherein a proportion of an area of the oligomer portion to 100% of a total area of the carboxyl group-containing resin A as determined by gel permeation chromatography using a differential refractive index detector is 0.1% to 9%, and wherein a proportion of the titanium oxide E to 100 parts by mass of the carboxyl group-containing resin A is 20 parts by mass or more.

2. The photosensitive resin composition according to claim 1, wherein a proportion of an area of the oligomer portion to 100% of a total area of the carboxyl group-containing resin A as determined by gel permeation chromatography using a differential refractive index detector is 0.1% to 3%.

3. The photosensitive resin composition according to any one of claims 1 to 2, wherein at least a part of the carboxyl group-containing resin A is a product of a polymerization reaction using a chain transfer agent.

4. The photosensitive resin composition according to claim 3, wherein the chain transfer agent contains an α-methylstyrene dimer.

2. The photosensitive resin composition according to claim 1, wherein 5. The photosensitive resin composition according to any one of claims 1 to 4, further comprising an antioxidant F.

3. The photosensitive resin composition according to claim 1 or 2, wherein, 6. The photosensitive resin composition according to claim 5, wherein the antioxidant F contains a hindered phenol-based antioxidant.

4. The photosensitive resin composition according to claim 3, wherein 7. The photosensitive resin composition according to any one of claims 1 to 6, further comprising a dispersant G.

5. The photosensitive resin composition according to claim 1 or 2, wherein 8. The photosensitive resin composition according to claim 7, wherein the dispersant G has a phosphoric acid group.

6. The photosensitive resin composition according to claim 5, wherein 9. The photosensitive resin composition according to any one of claims 1 to 8, wherein the photopolymerization initiator B contains an acyloxyphosphine-based photopolymerization initiator.

7. The photosensitive resin composition according to claim 1 or 2, wherein 10. The photosensitive resin composition according to any one of claims 1 to 9, wherein the photopolymerization initiator B further contains an α-hydroxyalkylphenone-based photopolymerization initiator.

8. The photosensitive resin composition according to claim 7, wherein 11. The photosensitive resin composition according to any one of claims 1 to 10, wherein the photopolymerizable compound C contains a trifunctional (meth)acrylate.

9. The photosensitive resin composition according to claim 1 or 2, wherein 12. The photosensitive resin composition according to any one of claims 1 to 11, wherein the epoxy resin D contains a crystalline epoxy resin.

10. The photosensitive resin composition according to claim 9, wherein 13. The photosensitive resin composition according to any one of claims 1 to 12, wherein the titanium oxide E contains rutile-type titanium oxide.

11. The photosensitive resin composition according to claim 1 or 2, wherein 14. A dry film comprising the photosensitive resin composition according to any one of claims 1 to 13.

12. The photosensitive resin composition according to claim 1 or 2, wherein 15. A solder resist comprising a cured product of the photosensitive resin composition according to any one of claims 1 to 13.

13. The photosensitive resin composition according to claim 1 or 2, wherein 16. A printed wiring board provided with a solder resist layer containing a cured product of the photosensitive resin composition according to any one of claims 1 to 13. ​ ​ ​

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