Photosensitive resin composition

Abstract

To provide a photosensitive resin composition from which an insulation protective film capable of preventing hardening shrinkage even under high temperature atmosphere during thermosetting treatment can be obtained without impairing basic characteristics such as sensitivity by direct drawing exposure.SOLUTION: A photosensitive resin composition contains (A) a photosensitive resin, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) a coloring agent, wherein (D) the epoxy compound contains (D1) a bisphenol type epoxy resin, and (D2) a dimer acid glycidyl ester type epoxy resin, and an epoxy equivalent of (D1) the bisphenol type epoxy resin is 500 or more and 1,000 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photosensitive resin composition that can be used as a covering material, for example, an insulating covering material for covering a conductor circuit pattern formed on a substrate such as a printed wiring board or a flexible printed wiring board; a cured product obtained by curing the photosensitive resin composition; a substrate such as a printed wiring board coated with the cured product; and a dry film having a coating film formed by applying the photosensitive resin composition to a film. [Background technology]

[0002] A conductor circuit pattern made of a conductor (e.g., copper foil) is formed on a printed wiring board or flexible printed wiring board, electronic components are mounted on the soldering lands of the circuit pattern by soldering, and the circuit portion excluding the soldering lands is covered with an insulating coating (e.g., a solder resist film) as a protective film. A photocured film of a photosensitive resin composition containing a photosensitive resin and a photopolymerization initiator may be used as the insulating protective film for the circuit portion.

[0003] Dry films may also be used as a method for forming an insulating protective film on a substrate. Dry films can be produced by forming a coating film of a photosensitive resin composition on a resin support film such as polyethylene terephthalate using a coating method such as a die coater, drying the coating film to form an insulating film (e.g., a solder resist film) on the support film, and then laminating a cover film on the formed insulating film. The insulating film and the substrate are bonded together while peeling off the cover film of the dry film, thereby forming an insulating coating (e.g., a solder resist layer) on the substrate. Thereafter, the solder resist layer is exposed to light from above the support film to photocure it, and then further subjected to a thermal curing treatment, thereby forming an insulating protective film on the substrate.

[0004] When forming an insulating protective film such as a solder resist film on a printed wiring board or a flexible printed wiring board, an exposure step may be performed using a direct imaging exposure device that directly draws an image on a coating film formed on the printed wiring board or the like without using a photomask. Depending on the application of the printed wiring board or the like, the insulating protective film such as a solder resist film may be made white to improve the reflectance of the insulating protective film. In white photosensitive resin compositions, an acylphosphine oxide-based photopolymerization initiator having discoloration resistance may be used as the photopolymerization initiator (Patent Document 1).

[0005] On the other hand, when forming an insulating protective film such as a solder resist film on a flexible printed wiring board, after the exposure step, a thermal curing treatment is carried out, for example, at 130 to 170° C. However, in a high-temperature atmosphere of 130 to 170° C., conventional insulating protective films such as those disclosed in Patent Document 1 may shrink upon curing due to heat, resulting in the problem of warping of a substrate such as a flexible printed wiring board having an insulating protective film.

[0006] When warping occurs in a substrate such as a flexible printed wiring board having an insulating protective film, there are problems in that the substrate becomes difficult to handle and is difficult to incorporate into the main body of a device such as a smartphone. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-232402 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above circumstances, an object of the present invention is to provide a photosensitive resin composition that can provide an insulating protective film that can prevent cure shrinkage even in a high-temperature atmosphere during heat curing treatment, without impairing basic properties such as sensitivity in direct writing exposure. [Means for solving the problem]

[0009] The gist of the configuration of the present invention is as follows. [1] A composition comprising (A) a photosensitive resin, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) a colorant; the (D) epoxy compound contains (D1) a bisphenol-type epoxy resin and (D2) a dimer acid glycidyl ester-type epoxy resin, The photosensitive resin composition (D1) contains a bisphenol-type epoxy resin having an epoxy equivalent of 500 or more and 1,000 or less. [2] The photosensitive resin composition according to [1], wherein the epoxy equivalent of the (D1) bisphenol epoxy resin is 600 or more and 800 or less. [3] The photosensitive resin composition according to [1] or [2], comprising 20 parts by mass or more and 150 parts by mass or less of the dimer acid glycidyl ester type epoxy resin (D2) relative to 100 parts by mass of the bisphenol type epoxy resin (D1). [4] The photosensitive resin composition according to [1] or [2], wherein the total amount of the (D1) bisphenol-type epoxy resin and the (D2) dimer acid glycidyl ester-type epoxy resin is 20 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the (A) photosensitive resin. [5] The photosensitive resin composition according to [1] or [2], wherein the total amount of the (D1) bisphenol-type epoxy resin and the (D2) dimer acid glycidyl ester-type epoxy resin is 40 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the (A) photosensitive resin. [6] The photosensitive resin composition according to [1] or [2], wherein the (D1) bisphenol epoxy resin is a bisphenol A epoxy resin. [7] The photosensitive resin composition according to [1] or [2], further comprising (D3) a bisphenol-type epoxy resin having an epoxy equivalent of 150 or more and 400 or less. [8] The photosensitive resin composition according to [7], containing 10 parts by mass or more and 100 parts by mass or less of the bisphenol-type epoxy resin (D3) having an epoxy equivalent of 150 or more and 400 or less per 100 parts by mass of the photosensitive resin (A). [9] The photosensitive resin composition according to [1] or [2], wherein the (E) colorant is a white colorant.

[10] The photosensitive resin composition according to [9], wherein the white colorant is titanium oxide.

[11] A cured product of the photosensitive resin composition according to [1] or [2].

[12] A flexible printed wiring board comprising the cured product according to

[11] .

[13] A dry film comprising the photosensitive resin composition according to [1] or [2].

[0010] In the above embodiment, the (D) epoxy compound used is a bisphenol-type epoxy resin and a dimer acid glycidyl ester-type epoxy resin having an epoxy equivalent of 500 or more and 1000 or less. The epoxy equivalent of the dimer acid glycidyl ester-type epoxy resin is not particularly limited. [Effects of the Invention]

[0011] According to an embodiment of the photosensitive resin composition of the present invention, the (D) epoxy compound contains the (D1) bisphenol-type epoxy resin and the (D2) dimer acid glycidyl ester-type epoxy resin, and the (D1) bisphenol-type epoxy resin has an epoxy equivalent of 500 or more and 1000 or less. This makes it possible to obtain an insulating protective film that can prevent cure shrinkage even in a high-temperature atmosphere during heat curing treatment, without impairing basic properties such as sensitivity in direct imaging exposure.

[0012] According to an embodiment of the photosensitive resin composition of the present invention, the epoxy equivalent of the (D1) bisphenol epoxy resin is 600 or more and 800 or less, so that an insulating protective film can be obtained that can more reliably prevent cure shrinkage even in a high-temperature atmosphere during heat curing treatment.

[0013] According to one embodiment of the photosensitive resin composition of the present invention, the (D2) dimer acid glycidyl ester epoxy resin is contained in an amount of 20 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the (D1) bisphenol epoxy resin, thereby making it possible to obtain an insulating protective film that can more reliably prevent cure shrinkage even in a high-temperature atmosphere during heat curing treatment.

[0014] According to an embodiment of the photosensitive resin composition of the present invention, the total blending amount of the (D1) bisphenol-type epoxy resin and the (D2) dimer acid glycidyl ester-type epoxy resin is 20 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the (A) photosensitive resin, whereby an insulating protective film can be obtained that can more reliably prevent cure shrinkage even in a high-temperature atmosphere during thermal curing treatment.

[0015] According to an embodiment of the photosensitive resin composition of the present invention, the total blending amount of the (D1) bisphenol epoxy resin and the (D2) dimer acid glycidyl ester epoxy resin is 40 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the (A) photosensitive resin, thereby further reducing the elastic modulus of the cured product of the photosensitive resin composition and contributing to obtaining an insulating protective film that can more reliably prevent cure shrinkage even in a high-temperature atmosphere during thermal curing treatment.

[0016] According to an embodiment of the photosensitive resin composition of the present invention, the composition further contains (D3) a bisphenol-type epoxy resin having an epoxy equivalent of 150 or more and 400 or less, thereby improving the solder heat resistance of the cured product of the photosensitive resin composition.

[0017] According to an embodiment of the photosensitive resin composition of the present invention, the (D3) bisphenol-type epoxy resin having an epoxy equivalent of 150 or more and 400 or less is contained in an amount of 10 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the (A) photosensitive resin, thereby further reliably improving the solder heat resistance of the cured product of the photosensitive resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, the photosensitive resin composition of the present invention will be described in detail. The photosensitive resin composition of the present invention contains (A) a photosensitive resin, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) a colorant, wherein the (D) epoxy compound contains (D1) a bisphenol-type epoxy resin and (D2) a dimer acid glycidyl ester-type epoxy resin, and the (D1) bisphenol-type epoxy resin has an epoxy equivalent of 500 or more and 1000 or less. The above components (A) to (E) will be described in detail below.

[0019] (A) Photosensitive resin The chemical structure of the photosensitive resin of component (A) is not particularly limited, and examples thereof include a resin having one or more photosensitive unsaturated double bonds, preferably two or more unsaturated double bonds, in one molecule. Examples of the photosensitive resin include (A-1) a photosensitive resin (A-1 resin) obtained by reacting at least a part of the epoxy groups of a copolymer of an ester of a radically polymerizable unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid (hereinafter sometimes referred to as "(meth)acrylic acid") with a compound having one or more radically polymerizable unsaturated groups and an epoxy group with a radically polymerizable unsaturated monocarboxylic acid such as (meth)acrylic acid; (A-2) a photosensitive resin (A-2 resin) obtained by reacting an epoxy or alcohol with a carboxyl group of a radically polymerizable unsaturated monocarboxylic acid such as (meth)acrylic acid; and (A-3) a photosensitive resin (A-3 resin) obtained by reacting at least a part of the carboxyl groups of a polymer of a radically polymerizable unsaturated monocarboxylic acid such as (meth)acrylic acid or a radically polymerizable unsaturated monocarboxylic acid such as (meth)acrylic acid with (meth)acrylic acid. and (A-4) an acid-modified urethane-modified unsaturated monocarboxylated epoxy resin (A-4 resin (urethane-modified resin)) having a moiety obtained by reacting a radically polymerizable unsaturated monocarboxylic acid with at least some of the epoxy groups of a polyfunctional epoxy resin having two or more epoxy groups per molecule to obtain an unsaturated monocarboxylated epoxy resin, then subjecting the resulting hydroxyl groups to an addition reaction with a polyisocyanate compound, and further subjecting the isocyanate groups of the resulting polyisocyanate compound to an addition reaction with a compound having a hydroxyl group and a carboxyl group.

[0020] A-1 resin Examples of radically polymerizable unsaturated monocarboxylic acids constituting the ester of radically polymerizable unsaturated monocarboxylic acid include (meth)acrylic acid, crotonic acid, tiglic acid, angelic acid, and cinnamic acid. Among these, (meth)acrylic acid is preferred because of its ease of availability and handling. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more. Furthermore, the alcohol constituting the ester of radically polymerizable unsaturated monocarboxylic acid is not particularly limited, and examples include aliphatic monoalcohols having 1 to 10 carbon atoms, such as methanol, ethanol, propanol, butanol, and hexanol. These alcohols may be used alone or in combination of two or more.

[0021] Examples of compounds having one or more radically polymerizable unsaturated groups and epoxy groups include glycidyl compounds. Examples of glycidyl compounds include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, pentaerythritol triacrylate monoglycidyl ether, and pentaerythritol trimethacrylate monoglycidyl ether. The number of glycidyl groups in a molecule may be one or more. The above-mentioned compounds having one or more radically polymerizable unsaturated groups and epoxy groups may be used alone or in combination of two or more.

[0022] Examples of the radically polymerizable unsaturated monocarboxylic acid to be reacted with at least a portion of the epoxy groups of the copolymer include the same compounds as the radically polymerizable unsaturated monocarboxylic acids that constitute the esters of radically polymerizable unsaturated monocarboxylic acids, i.e., (meth)acrylic acid, crotonic acid, tiglic acid, angelic acid, cinnamic acid, etc. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

[0023] A-2 resin Examples of the radically polymerizable unsaturated monocarboxylic acid include the same compounds as those mentioned above, i.e., (meth)acrylic acid, crotonic acid, tiglic acid, angelic acid, cinnamic acid, etc. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

[0024] Examples of epoxy compounds to be reacted with the radically polymerizable unsaturated monocarboxylic acid include compounds having an alicyclic or aromatic ring skeleton and an epoxy group, and resins having an epoxy group. The epoxy equivalent is not particularly limited, but is preferably 100 to 1,000, and particularly preferably 100 to 500. Examples of alicyclic compounds include cyclohexane and cyclopentane. Examples of alicyclic epoxy compounds include 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate, vinylcyclohexene monoxide 1,2-epoxy-4-vinylcyclohexane, and 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol. Resins containing epoxy groups (epoxy resins) are not particularly limited, and examples include rubber-modified epoxy resins such as biphenylaralkyl epoxy resins, phenylaralkyl epoxy resins, biphenyl epoxy resins, naphthalene epoxy resins, dicyclopentadiene epoxy resins, and silicone-modified epoxy resins; ε-caprolactone-modified epoxy resins; phenol novolac epoxy resins such as bisphenol A epoxy resins and bisphenol F epoxy resins; cresol novolac epoxy resins such as ortho-cresol novolac; bisphenol A novolac epoxy resins; cycloaliphatic polyfunctional epoxy resins; glycidyl ester polyfunctional epoxy resins; glycidyl amine polyfunctional epoxy resins; heterocyclic polyfunctional epoxy resins; bisphenol-modified novolac epoxy resins; and polyfunctional modified novolac epoxy resins. These epoxy resins may also be used with halogen atoms such as Br and Cl introduced. These epoxy resins may be used alone or in combination.

[0025] The alcohol to be reacted with the radically polymerizable unsaturated monocarboxylic acid is not particularly limited, and examples thereof include C2-C olefins such as ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 2,2-diethyl-1,3-propanediol, 3,3-dimethylolheptane, 2-ethyl-2-butyl-1,3-propanediol, 1,12-dodecanediol, and 1,18-octadecanediol. 22 Examples of suitable alcohols include aliphatic diols such as alkanediols, 2-butene-1,4-diol, 2,6-dimethyl-1-octene-3,8-diol, and other alkenediols; alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol; aliphatic triols such as glycerin, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentane, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-(hydroxymethyl)pentane, and 2,2-bis(hydroxymethyl)-3-butanol; and polyols having four or more hydroxyl groups such as tetramethylolmethane, pentaerythritol, dipentaerythritol, and xylitol. These alcohols may be used alone or in combination of two or more.

[0026] A-3 resin Examples of monomers constituting the polymer of radically polymerizable unsaturated monocarboxylic acid include the same compounds as those described above, i.e., (meth)acrylic acid, crotonic acid, tiglic acid, angelic acid, cinnamic acid, etc. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more. Furthermore, examples of esters of radically polymerizable unsaturated monocarboxylic acids constituting the copolymer include the esters used in synthesizing the A-1 resin described above. Examples of compounds having one or more radically polymerizable unsaturated groups and an epoxy group that are reacted with at least a portion of the carboxyl groups of the polymer of radically polymerizable unsaturated monocarboxylic acid or at least a portion of the carboxyl groups of the copolymer obtained by reacting a radically polymerizable unsaturated monocarboxylic acid such as (meth)acrylic acid with an ester of a radically polymerizable unsaturated monocarboxylic acid such as (meth)acrylic acid, include, for example, glycidyl compounds. Examples of glycidyl compounds include the same compounds as those mentioned above, i.e., glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, pentaerythritol triacrylate monoglycidyl ether, pentaerythritol trimethacrylate monoglycidyl ether, etc. The number of glycidyl groups in one molecule may be one or more. The compounds having one or more radically polymerizable unsaturated groups and epoxy groups mentioned above may be used alone or in combination of two or more.

[0027] A-4 resin The multifunctional epoxy resin is not particularly limited, and examples thereof include the same epoxy resins as those described above, i.e., rubber-modified epoxy resins such as biphenylaralkyl epoxy resins, phenylaralkyl epoxy resins, biphenyl epoxy resins, naphthalene epoxy resins, dicyclopentadiene epoxy resins, and silicone-modified epoxy resins; ε-caprolactone-modified epoxy resins; phenol novolac epoxy resins such as bisphenol A epoxy resins and bisphenol F epoxy resins; cresol novolac epoxy resins such as ortho-cresol novolac; bisphenol A novolac epoxy resins; cycloaliphatic multifunctional epoxy resins; glycidyl ester multifunctional epoxy resins; glycidyl amine multifunctional epoxy resins; heterocyclic multifunctional epoxy resins; bisphenol-modified novolac epoxy resins; and multifunctional modified novolac epoxy resins. Furthermore, these resins may be further modified with halogen atoms such as Br or Cl. These multifunctional epoxy resins may be used alone or in combination.

[0028] Examples of the radically polymerizable unsaturated monocarboxylic acid to be reacted with the epoxy group of the polyfunctional epoxy resin include the same compounds as those mentioned above, i.e., (meth)acrylic acid, crotonic acid, tiglic acid, angelic acid, cinnamic acid, etc. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

[0029] The polyisocyanate compound is not particularly limited, and examples thereof include diisocyanates such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene diisocyanate (MDI), methylene biscyclohexyl isocyanate, trimethylhexamethyl diisocyanate, hexane diisocyanate, hexamethylamine diisocyanate, methylene biscyclohexyl isocyanate, toluene diisocyanate, 1,2-diphenylethane diisocyanate, 1,3-diphenylpropane diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethyl diisocyanate. These polyisocyanate compounds may be used alone or in combination of two or more.

[0030] The compound having a hydroxyl group and a carboxyl group is not particularly limited, and examples thereof include dialkanolalkanoic acids such as dimethylolalkanoic acids such as dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid, dimethylolheptanoic acid, etc. These compounds having a hydroxyl group and a carboxyl group may be used alone or in combination of two or more.

[0031] In addition to the above-mentioned A-1 to A-4 resins, the photosensitive resin may also be a polybasic acid-modified radically polymerizable unsaturated monocarboxylic acid (A-5 resin) obtained by reacting a radically polymerizable unsaturated monocarboxylic acid such as (meth)acrylic acid with at least some of the epoxy groups of a polyfunctional epoxy resin having two or more epoxy groups per molecule to obtain a radically polymerizable unsaturated monocarboxylic acid-modified epoxy resin, and then reacting the resulting hydroxyl groups with a polybasic acid or its anhydride to introduce free carboxyl groups. Examples of the polyfunctional epoxy resin and radically polymerizable unsaturated monocarboxylic acid that constitute the A-5 resin include the compounds described above.

[0032] Examples of polybasic acids include succinic acid, maleic acid, adipic acid, citric acid, phthalic acid, phthalic acid derivatives (e.g., tetrahydrophthalic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, 3-ethyltetrahydrophthalic acid, 4-ethyltetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid, 4-ethylhexahydrophthalic acid, methyltetrahydrophthalic acid, methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid, and methylendomethylenetetrahydrophthalic acid), trimellitic acid, pyromellitic acid, and diglycolic acid. Examples of polybasic acid anhydrides include anhydrides of the above-mentioned polybasic acids. These polybasic acids or polybasic acid anhydrides may be used alone or in combination of two or more.

[0033] The above-mentioned A-1 resin to A-5 resin may be used alone or in combination of two or more kinds.

[0034] The mass average molecular weight of the photosensitive resin is not particularly limited, but from the viewpoints of the toughness of the cured product of the photosensitive resin composition and the dryness to touch of the photosensitive resin composition, the lower limit is preferably 3,000, and particularly preferably 5,000. On the other hand, from the viewpoints of preventing an increase in the viscosity of the photosensitive resin composition and obtaining excellent coatability, the upper limit of the mass average molecular weight is preferably 200,000, and particularly preferably 50,000.

[0035] The double bond equivalent of the photosensitive resin is not particularly limited, but the lower limit is preferably 1000 g / eq, and particularly preferably 1300 g / eq, from the viewpoint of imparting excellent flexibility to the cured product of the photosensitive resin composition, while the upper limit is preferably 3000 g / eq, and particularly preferably 2000 g / eq, from the viewpoint of imparting strength to the cured product of the photosensitive resin composition.

[0036] (B) Photopolymerization initiator Examples of the photopolymerization initiator include an oxime ester-based photopolymerization initiator and an acylphosphine oxide-based photopolymerization initiator.

[0037] Examples of the oxime ester-based photopolymerization initiator include an oxime ester-based photopolymerization initiator having a diphenyl sulfide skeleton. Examples of the oxime ester-based photopolymerization initiator having a diphenyl sulfide skeleton include an oxime ester-based photopolymerization initiator represented by the following general formula (1): [ka] (wherein R is H or a hydrocarbon group having 1 to 10 carbon atoms; R 1 is H or a hydrocarbon group having 1 to 10 carbon atoms, R 2 is O.C. n H 2n -OH), where n represents an integer of 1 to 10. Among these, R is preferably H or a chain hydrocarbon group having 1 to 5 carbon atoms, more preferably H or a chain hydrocarbon group having 1 to 3 carbon atoms, and particularly preferably H. In addition, R 1 is preferably H or a chain hydrocarbon group having 1 to 5 carbon atoms, more preferably H or a chain hydrocarbon group having 1 to 3 carbon atoms, and particularly preferably H. Furthermore, n is preferably an integer of 1 to 5, more preferably an integer of 2 to 4, and particularly preferably 2.

[0038] Examples of the oxime ester photopolymerization initiator having a diphenyl sulfide skeleton include those represented by the following formula (1-1): [ka] Examples of the compound include compounds represented by the following formula:

[0039] Furthermore, examples of oxime ester photopolymerization initiators (other oxime ester photopolymerization initiators) other than the oxime ester photopolymerization initiators having a diphenyl sulfide skeleton include 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), 2-(acetyloxyiminomethyl)thioxanthen-9-one, 1,8-octanedione, 1,8-bis[9-ethyl-6-nitro-9H-carbazol-3-yl]-, 1,8-bis(O-acetyloxime), 1,8-octanedione, 1,8-bis[9-(2-ethylhexyl)-6-nitro-9H-carbazol-3-yl]-, 1,8-bis(O-acetyloxime), (Z) -(9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime.

[0040] Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide.

[0041] Examples of photopolymerization initiators (other photopolymerization initiators) other than the oxime ester photopolymerization initiators and the acylphosphine oxide photopolymerization initiators include α-aminoalkylphenones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, benzoins such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, and benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, and acetophenone dimethyl ketone. Examples of such acetophenones include tar, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, and p-dimethylaminobenzoic acid ethyl ester.

[0042] Among these, it is preferable to use a combination of an oxime ester photopolymerization initiator having a diphenyl sulfide skeleton and an acylphosphine oxide photopolymerization initiator in order to improve the discoloration resistance of the photosensitive resin composition.

[0043] The amount of the photopolymerization initiator to be blended is not particularly limited, but the lower limit is preferably 1.0 part by mass, more preferably 5.0 parts by mass, and particularly preferably 10 parts by mass, relative to 100 parts by mass of the photosensitive resin (solid content, the same applies hereinafter), from the viewpoint of reliably improving sensitivity and resolution. On the other hand, the upper limit of the amount of the photopolymerization initiator to be blended is preferably 50 parts by mass, particularly preferably 40 parts by mass, relative to 100 parts by mass of the photosensitive resin, from the viewpoint of reliably reducing warpage of the cured product of the photosensitive resin composition even in a high-temperature atmosphere during heat curing treatment.

[0044] (C) Reactive diluent The reactive diluent is, for example, a photopolymerizable monomer, which is a compound having at least one polymerizable double bond per molecule, preferably two or more polymerizable double bonds per molecule. The reactive diluent reinforces the photocuring of the photosensitive resin composition and contributes to the formation of a cured film having sufficient strength.

[0045] Examples of reactive diluents include monofunctional (meth)acrylate compounds and polyfunctional (meth)acrylate compounds having two or more functional groups. Examples of the (meth)acrylate compounds include monofunctional (meth)acrylate compounds such as hydroxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, diethylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and caprolactone-modified (meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and ethylene oxide. Examples of the (meth)acrylate compound include bifunctional (meth)acrylate compounds such as modified phosphoric acid di(meth)acrylate, allylated cyclohexyl di(meth)acrylate, and isocyanurate di(meth)acrylate; trifunctional (meth)acrylate compounds such as trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, and tris(acryloxyethyl)isocyanurate; and tetrafunctional or higher functional (meth)acrylate compounds such as ditrimethylolpropane tetra(meth)acrylate, propionic acid-modified dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Examples of the (meth)acrylate compound include monofunctional or difunctional or higher functional epoxy (meth)acrylate compounds. These (meth)acrylate compounds may be used alone or in combination of two or more.

[0046] The amount of reactive diluent added is not particularly limited, but is preferably 50 parts by mass or more and 250 parts by mass or less, and particularly preferably 100 parts by mass or more and 200 parts by mass or less, per 100 parts by mass of the photosensitive resin.

[0047] (D) Epoxy compounds The photosensitive resin composition of the present invention contains, as the (D) epoxy compound, a (D1) bisphenol-type epoxy resin and a (D2) dimer acid glycidyl ester-type epoxy resin. Furthermore, in the photosensitive resin composition of the present invention, a bisphenol-type epoxy resin having an epoxy equivalent of 500 or more and 1000 or less is used as the (D1) bisphenol-type epoxy resin. By using, as the (D) epoxy compound, a (D1) bisphenol-type epoxy resin having an epoxy equivalent of 500 or more and 1000 or less (hereinafter simply referred to as "(D1) bisphenol-type epoxy resin") and a (D2) dimer acid glycidyl ester-type epoxy resin, the cured product of the photosensitive resin composition can be made to have low elasticity, preventing cure shrinkage of the photosensitive resin composition even when exposed to a high-temperature atmosphere during a heat curing treatment (e.g., an atmosphere of 130 to 170°C) or even when exposed to a high-temperature atmosphere during a heat curing treatment, without impairing basic properties such as sensitivity in direct imaging exposure. As a result, an insulating protective film having cure shrinkage prevented can be obtained. Therefore, by blending (D1) a bisphenol-type epoxy resin having an epoxy equivalent of 500 or more and 1000 or less and (D2) a dimer acid glycidyl ester-type epoxy resin as the epoxy compound (D), it is possible to prevent warping of a substrate having an insulating protective film formed from the photosensitive resin composition of the present invention, thereby preventing deterioration in the handleability of the substrate and preventing deterioration in the ease of incorporating the substrate into the main body of a device such as a smartphone.

[0048] The (D) epoxy compound also contributes to increasing the crosslink density of the cured product of the photosensitive resin composition, thereby forming a cured film with sufficient strength. In the photosensitive resin composition of the present invention, the (D) epoxy compound comprises a (D1) bisphenol-type epoxy resin and a (D2) dimer acid glycidyl ester-type epoxy resin, and may be configured to contain no epoxy compounds of other chemical structures, or may further comprise an epoxy compound of other chemical structures. As will be described later, the (D) epoxy compound comprises a (D1) bisphenol-type epoxy resin, a (D2) dimer acid glycidyl ester-type epoxy resin, and a (D3) bisphenol-type epoxy resin with an epoxy equivalent of 150 or more and 400 or less, and may be configured to contain no epoxy compounds of other chemical structures, or may further comprise an epoxy compound of other chemical structures.

[0049] The epoxy equivalent of the (D1) bisphenol epoxy resin is not particularly limited as long as it is in the range of 500 or more and 1000 or less. However, from the viewpoint of obtaining an insulating protective film that can more reliably prevent cure shrinkage even in the high-temperature atmosphere during heat curing treatment and even after being subjected to the high-temperature atmosphere during heat curing treatment, the range of 550 or more and 900 or less is preferred, and the range of 600 or more and 800 or less is particularly preferred.

[0050] Examples of (D2) dimer acid glycidyl ester epoxy resins include epoxy resins glycidyl-esterified with epichlorohydrin of dimer acid. The epoxy equivalent of (D2) dimer acid glycidyl ester epoxy resins is not particularly limited, but is preferably in the range of 200 to 700, more preferably 300 to 600, and particularly preferably 350 to 550, from the viewpoint of obtaining an insulating protective film that can more reliably prevent cure shrinkage.

[0051] The blending ratio of the (D1) bisphenol epoxy resin and the (D2) dimer acid glycidyl ester epoxy resin is not particularly limited, but the lower limit of the blending amount of the (D2) dimer acid glycidyl ester epoxy resin per 100 parts by mass of the (D1) bisphenol epoxy resin is preferably 20 parts by mass, and more preferably 30 parts by mass, in order to obtain an insulating protective film that reliably reduces the elasticity of the cured product of the photosensitive resin composition and prevents cure shrinkage even in the high-temperature atmosphere during heat curing treatment and after exposure to the high-temperature atmosphere during heat curing treatment. On the other hand, the upper limit of the blending amount of the (D2) dimer acid glycidyl ester epoxy resin per 100 parts by mass of the (D1) bisphenol epoxy resin is preferably 150 parts by mass, and more preferably 130 parts by mass, in order to obtain excellent solder heat resistance.

[0052] The total amount of the bisphenol epoxy resin (D1) and the dimer acid glycidyl ester epoxy resin (D2) is not particularly limited, but the lower limit is preferably 20 parts by mass per 100 parts by mass of the photosensitive resin (A) to obtain an insulating protective film that can more reliably prevent cure shrinkage even in the high-temperature atmosphere of the heat curing treatment and after the high-temperature atmosphere of the heat curing treatment, and 40 parts by mass is more preferred, and 50 parts by mass is particularly preferred to further reduce the modulus of elasticity of the cured product of the photosensitive resin composition, contributing to obtaining an insulating protective film that can more reliably prevent cure shrinkage even in the high-temperature atmosphere of the heat curing treatment and after the high-temperature atmosphere of the heat curing treatment. On the other hand, the upper limit of the total amount of the bisphenol epoxy resin (D1) and the dimer acid glycidyl ester epoxy resin (D2) is preferably 150 parts by mass, and 120 parts by mass is particularly preferred to obtain excellent alkali developability.

[0053] (D1) Examples of bisphenol-type epoxy resins include bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, etc. Among these, bisphenol A-type epoxy resins are preferred because they can provide an insulating protective film that can more reliably prevent cure shrinkage.

[0054] The photosensitive resin composition of the present invention may contain, as the epoxy compound, in addition to the (D1) bisphenol-type epoxy resin and the (D2) dimer acid glycidyl ester-type epoxy resin, if necessary, a (D3) bisphenol-type epoxy resin having an epoxy equivalent of 150 or more and 400 or less. By containing the (D3) bisphenol-type epoxy resin having an epoxy equivalent of 150 or more and 400 or less (hereinafter sometimes simply referred to as "(D3) bisphenol-type epoxy resin"), the solder heat resistance of the cured product of the photosensitive resin composition is improved.

[0055] The epoxy equivalent of the (D3) bisphenol type epoxy resin is not particularly limited as long as it is in the range of 150 or more and 400 or less, but from the viewpoint of reliably improving solder heat resistance, it is preferably in the range of 180 or more and 350 or less, and particularly preferably in the range of 200 or more and 300 or less.

[0056] The amount of the bisphenol epoxy resin (D3) blended is not particularly limited, but the lower limit is preferably 10 parts by mass, and particularly preferably 20 parts by mass, per 100 parts by mass of the photosensitive resin (A), from the viewpoint of further improving the solder heat resistance of the cured product of the photosensitive resin composition. On the other hand, the upper limit of the amount of the bisphenol epoxy resin (D3) blended is preferably 100 parts by mass, and particularly preferably 70 parts by mass, from the viewpoint of further improving anti-warping properties.

[0057] (D3) Examples of bisphenol type epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, etc. Among these, bisphenol A type epoxy resins are preferred because they further reliably improve solder heat resistance.

[0058] (E) Colorant By incorporating a colorant, a desired color can be imparted to the cured film of the photosensitive resin composition. The colorant is not particularly limited to a pigment, a dye, or the like. Furthermore, any colorant can be used depending on the desired color, such as a white colorant, a blue colorant, a green colorant, a yellow colorant, a purple colorant, a black colorant, a red colorant, or an orange colorant. By incorporating a white colorant as the colorant, a white cured film can be formed, thereby improving the reflectance of the cured film. Examples of the white colorant include titanium oxide. Examples of titanium oxide include anatase-type titanium oxide and rutile-type titanium oxide. Of these, rutile-type titanium oxide is preferred from the viewpoint of improving reflectance.

[0059] The amount of the colorant to be added is not particularly limited. In the case of a white colorant, the amount is not particularly limited, but from the viewpoint of improving the reflectance and flexibility of the cured film, the amount is preferably 100 parts by mass or more and 600 parts by mass or less, and particularly preferably 300 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the photosensitive resin.

[0060] In addition to the components (A) to (E) described above, the photosensitive resin composition of the present invention may contain various other components, such as a curing catalyst, a flame retardant, an elastomer, a non-reactive diluent, and an antifoaming agent, as needed.

[0061] Examples of curing catalysts include dicyandiamide (DICY) and its derivatives, melamine and its derivatives, boron trifluoride-amine complex, organic acid hydrazide, diaminomaleonitrile (DAMN) and its derivatives, guanamine and its derivatives, amine imide, and polyamine.

[0062] Flexible printed wiring boards are often equipped with electronic components and light sources that generate a large amount of heat. Therefore, by incorporating a flame retardant into a photosensitive resin composition, flame retardancy can be imparted to a cured film of the photosensitive resin composition. Examples of flame retardants include phosphorus-based flame retardants such as organic phosphates.Examples of phosphorus-based flame retardants include halogen-containing phosphorus compounds such as tris(chloroethyl)phosphate, tris(2,3-dichloropropyl)phosphate, tris(2-chloropropyl)phosphate, tris(2,3-bromopropyl)phosphate, tris(bromochloropropyl)phosphate, 2,3-dibromopropyl-2,3-chloropropyl phosphate, tris(tribromophenyl)phosphate, tris(dibromophenyl)phosphate, and tris(tribromoneopentyl)phosphate. Phosphate esters; non-halogenated aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, and tributoxyethyl phosphate; triphenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, tricresyl phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, tris(isopropylphenyl) phosphate, isopropylphenyl diphenyl phosphate, and diisopropyl phosphate. Examples of suitable phosphine compounds include non-halogen aromatic phosphate esters such as propylphenylphenyl phosphate, tris(trimethylphenyl)phosphate, tris(t-butylphenyl)phosphate, hydroxyphenyldiphenylphosphate, and octyldiphenylphosphate; metal salts of phosphinic acid such as aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanyl bismethylethylphosphinate, titanium tetrakismethylethylphosphinate, titanyl bisdiphenylphosphinate, and titanium tetrakisdiphenylphosphinate; and phosphine oxide compounds such as diphenylvinylphosphine oxide, triphenylphosphine oxide, trialkylphosphine oxide, and tris(hydroxyalkyl)phosphine oxide.

[0063] The incorporation of an elastomer into a photosensitive resin composition contributes to imparting flexibility, warpage resistance, discoloration resistance, and high reflectivity to a cured film of the photosensitive resin composition. Examples of the elastomer include silicone-based elastomers. Examples of the defoaming agent include silicone-based polymers, hydrocarbon-based polymers, and acrylic-based polymers.

[0064] The non-reactive diluent is used to appropriately adjust the viscosity, drying property, coatability, etc. of the photosensitive resin composition. Examples of the non-reactive diluent include organic solvents. Examples of the organic solvent include ketones such as methyl ethyl ketone; aromatic hydrocarbons such as benzene, toluene, and xylene; alcohols such as methanol, n-propanol, isopropanol, and cyclohexanol; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; cellosolves such as cellosolve and butyl cellosolve; carbitols such as carbitol and butyl carbitol; and esters such as ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, diethylene glycol monomethyl ether acetate, and ethyl diglycol acetate. These organic solvents may be used alone or in combination of two or more.

[0065] The method for producing the photosensitive resin composition of the present invention is not limited to a specific method, and the composition can be produced, for example, by blending the above-mentioned components in a predetermined ratio and then kneading or mixing them at room temperature (e.g., 25° C.) using a kneading means such as a triple roll mill, a ball mill, a sand mill, a bead mill, or a kneader, or a stirring means such as a super mixer or a planetary mixer. Furthermore, prior to the kneading or mixing, pre-kneading or pre-mixing may be carried out as necessary.

[0066] Next, examples of methods for using the photosensitive resin composition of the present invention will be described. First, a method for forming a solder resist film on a flexible printed wiring board having a circuit pattern formed by etching copper foil on a substrate will be described as an example.

[0067] The dry film has a laminated structure comprising a support film (e.g., a thermoplastic resin film such as a polyethylene terephthalate film or a polyester film), a solder resist layer coated on the support film, and a cover film (e.g., a polyethylene film or a polypropylene film) that protects the solder resist layer. The photosensitive resin composition of the present invention is coated onto the support film by a known method such as a die coater method to form a coating film of the photosensitive resin composition having a predetermined thickness. If necessary, the formed coating film of the photosensitive resin composition is pre-dried by heating at a temperature of about 70 to 120°C for about 10 to 60 minutes to volatilize the non-reactive diluent in the photosensitive resin composition. The pre-drying volatilizes the non-reactive diluent from the photosensitive resin composition, rendering the surface of the coating film tack-free, thereby forming a solder resist layer on the support film. A cover film is then laminated on the resulting solder resist layer to produce a dry film comprising the photosensitive resin composition of the present invention.

[0068] The prepared dry film is laminated onto a flexible printed wiring board while peeling off the cover film, thereby forming a solder resist layer on the flexible printed wiring board. The support film remains laminated on the solder resist layer formed on the flexible printed wiring board. A negative film having a circuit pattern in which areas other than the lands are transparent is then placed on the support film, and ultraviolet light (e.g., wavelengths in the range of 300 to 400 nm) is irradiated onto the negative film to photocure the solder resist layer. The support film is then peeled off, and the unexposed areas corresponding to the lands are removed with a dilute alkaline aqueous solution, thereby developing the solder resist layer. Examples of development methods include a spray method and a shower method. Examples of the dilute alkaline aqueous solution used include a 0.5 to 5% by mass sodium carbonate aqueous solution. After the alkaline development, the solder resist layer is subjected to a thermal curing treatment (post-cure) for 20 to 80 minutes in a hot air circulation dryer at 130 to 170°C, etc., to form a solder resist film on the flexible printed wiring board.

[0069] Next, as an example of a method for using the photosensitive resin composition of the present invention, a method will be described in which the photosensitive resin composition of the present invention is applied as a solder resist film onto a flexible printed wiring board having a circuit pattern formed on a substrate by etching copper foil.

[0070] The photosensitive resin composition of the present invention is applied to a flexible printed wiring board to a desired thickness using a known coating method, such as screen printing, a spray coater, a bar coater, an applicator, a blade coater, a knife coater, a roll coater, or a gravure coater. After application, if a non-reactive diluent is incorporated into the photosensitive resin composition, the composition is pre-dried by heating at a temperature of approximately 70 to 120°C for approximately 10 to 60 minutes to volatilize the non-reactive diluent in the photosensitive resin composition, forming a tack-free coating film. Next, the photosensitive resin composition is directly irradiated with active energy rays (e.g., ultraviolet rays) according to the desired pattern using a direct imaging device, and the coating film is photocured in the desired pattern. The coating film is then developed by removing the unexposed areas with a dilute alkaline aqueous solution. Examples of the development method include a spray method and a shower method. Examples of the dilute alkaline aqueous solution include a 0.5 to 5% by mass aqueous sodium carbonate solution. Next, the developed coating film is thermally cured by performing a heat curing treatment (post-cure) for 20 to 80 minutes in a hot air circulation dryer or the like at 130 to 170°C, and a cured product of the photosensitive resin composition having the desired pattern can be formed on the flexible printed wiring board. [Example]

[0071] Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as they do not depart from the spirit of the present invention.

[0072] Examples 1 to 5, Comparative Examples 1 to 2 The components shown in Table 1 below were blended in the blending ratios shown in Table 1 below, and mixed and dispersed at room temperature using a three-roll mill to prepare photosensitive resin compositions used in Examples 1 to 5 and Comparative Examples 1 and 2. Unless otherwise specified, the blending amount of each component shown in Table 1 below means parts by mass.

[0073] Details of each component in Table 1 are as follows:

[0074] (A) Photosensitive resin FLX-2089: Urethane-modified resin (A-4 resin), Nippon Kayaku Co., Ltd. (solid content 65% by mass) Synthetic resin The acrylic copolymer resin was synthesized as follows (in Table 1, "Synthetic Resin A"). A 3-liter separable flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen or air inlet tube was charged with 1500 g of propylene glycol monomethyl ether (Arcosolve PM, Sanyo Chemical Industries, Ltd.). The temperature was raised to 105°C, and a solution containing 142 g of glycidyl methacrylate (Blenmer GH, NOF Corporation), 1279 g of n-butyl methacrylate, 360 g of propylene glycol monomethyl ether, and 15.0 g of dimethyl 2,2'-azobis(2-methylpropionate) (V-601, Wako Pure Chemical Industries, Ltd.) was added dropwise over 3 hours. After the dropwise addition, the reaction was continued for 3 hours under a nitrogen atmosphere for aging. Next, a solution containing 690 g of acrylic acid, 3 g of triphenylphosphine, and 3 g of methoxyphenol was added under an air atmosphere, and the reaction was continued for 10 hours at 110°C. This resulted in a solution (solid content 65% by mass) of synthetic resin A having an acid value of 1.2 mgKOH / g, a double bond equivalent of 1500 g / eq, and a weight average molecular weight of 22000. Synthetic resin A is A-1 resin.

[0075] (B) Photopolymerization initiator SPEEDCURE TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide, acylphosphine oxide photoinitiator, LAMBSON An oxime ester photopolymerization initiator having a diphenyl sulfide skeleton and a chemical structure represented by formula (1-1):

[0076] (C) Reactive diluent EBECRYL3708: Daicel Allnex Co., Ltd.

[0077] (D) Epoxy compounds Epicoat 1003: (D1) Bisphenol-type epoxy resin with an epoxy equivalent weight of 500 to 1000, Mitsubishi Chemical Corporation jER871: (D2) Dimer acid glycidyl ester type epoxy resin, Mitsubishi Chemical Corporation EPICRON860: (D3) Bisphenol-type epoxy resin with an epoxy equivalent weight of 150 to 400, manufactured by DIC Corporation

[0078] (E) Colorant CR-80: White colorant, Ishihara Sangyo Kaisha, Ltd.

[0079] curing catalyst DICY-7: Mitsubishi Chemical Corporation Melamine: Nissan Chemical Industries, Ltd. flame retardants Exolit OP-935: Clariant Japan Elastomer EP-2601: Toray Dow Corning Co., Ltd. Non-reactive diluents ·EDGAC: Sanyo Chemical Industries, Ltd. Antifoaming agents AC-2000HF: Kyoeisha Chemical Co., Ltd.

[0080] Test specimen production process Substrate: Polyimide film (film thickness 25 μm, copper foil thickness 12 μm, Nippon Steel & Sumikin Chemical Co., Ltd. "ESPANEX") Surface treatment: 5% by mass sulfuric acid treatment Printing method: Screen printing Dry film thickness: 20 μm Pre-drying: 80°C, 20 minutes Exposure: 300 mJ / cm on photosensitive resin composition 2 (Direct imaging exposure device "Nuvogo1000R" (light source: laser, main wavelength 375nm, 405nm), manufactured by Orbotech) Alkaline development: 1% by mass Na2CO3 aqueous solution, liquid temperature 30°C, spray pressure 0.2 MPa, development time 60 seconds Post-cure heat treatment: 150°C, 60 minutes

[0081] Evaluation items (1) Sensitivity (Direct Imaging (LDI) Exposure Sensitivity) For the substrate that had undergone the preliminary drying process of the above test specimen preparation process, a step tablet for sensitivity measurement (Kodak, Stouffer 21 step) was placed on the coating film, and ultraviolet rays with wavelengths of 375 nm and 405 nm were irradiated at 300 mJ / cm using a direct writing exposure device "Nuvogo1000R" through the step tablet. 2 The irradiated specimen was used as a test piece. The obtained test piece was developed in the same manner as in the above-mentioned test specimen preparation process. The exposed portion that was not removed after development was represented by a number (number of steps). The larger the number of steps, the better the sensitivity.

[0082] (2) Warp prevention The test specimens prepared in the above test specimen preparation process were cut into 3 cm x 3 cm pieces, and the cut test specimens were placed on a horizontal table with the top concave. Without applying any external force, the vertical distance between the four corners of the test specimen and the table was measured with a ruler, and the maximum value was used to evaluate the test specimens on the following four-point scale. A rating of △ or better was considered a pass. ◎: Less than 1 mm, ○: 1mm or more and less than 3mm, △: 3mm or more and less than 5mm, ×: 5mm or more

[0083] (3) Elastic modulus (GPa) The photosensitive resin composition prepared as described above was applied to a polyethylene terephthalate film by screen printing to a thickness of 50 μm ± 10 μm, and then the test specimen preparation process was carried out from pre-drying to post-cure to form a cured coating film. The resulting cured coating film was peeled from the polyethylene terephthalate film, and the elastic modulus of the cured coating film test specimen cut to a predetermined size was measured using an autograph manufactured by Shimadzu Corporation. The test conditions were a test specimen size of 3.0 mm × 40.0 mm and a pulling speed of 5 mm / min.

[0084] (4) Solder heat resistance The cured coating film of the test specimen obtained in the test specimen preparation process was immersed in a solder bath at 260°C for 30 seconds in accordance with the test method of JIS C-6481, and then subjected to a peeling test using cellophane tape, which constituted one cycle. This was repeated 1 to 3 times, after which the condition of the cured coating film was visually observed and rated on the following 3-point scale. A rating of △ or higher was considered a pass. The evaluation was based on the following criteria. ◯: No change was observed in the cured coating film even after two cycles. Δ: No change was observed in the cured coating film after one cycle, but a change was observed in the cured coating film after two cycles. ×: Changes such as peeling were observed in the cured coating film after one cycle.

[0085] The evaluation results are shown in Table 1 below.

[0086] [Table 1]

[0087] As can be seen from Table 1 above, in Examples 1 to 5, which used (D1) a bisphenol-type epoxy resin with an epoxy equivalent of 500 to 1000 and (D2) a dimer acid glycidyl ester-type epoxy resin as the epoxy compound, the substrate was able to obtain anti-warping properties even after heat treatment at 150°C for 60 minutes without impairing direct imaging exposure (LDI exposure). Therefore, it was found that in Examples 1 to 5, an insulating protective film that can prevent cure shrinkage can be obtained even after exposure to a high-temperature atmosphere during thermal curing treatment.

[0088] In addition, in Examples 1 to 5, the modulus of elasticity of the cured coating film formed from the photosensitive resin composition was reduced to 1 GPa or less, which contributed to preventing warpage. Furthermore, in Examples 1 to 5, the addition of (D3) a bisphenol-type epoxy resin having an epoxy equivalent of 150 to 400 provided solder heat resistance.

[0089] On the other hand, as can be seen from Table 1 above, in Comparative Example 1, which did not contain (D2) dimer acid glycidyl ester epoxy resin, and Comparative Example 2, which did not contain (D1) bisphenol epoxy resin with an epoxy equivalent of 500 or more and 1000 or less, warping occurred in the substrate after heat treatment at 150°C for 60 minutes, and it was not possible to obtain an insulating protective film that could prevent cure shrinkage. Furthermore, in Comparative Example 2, which did not contain (D3) bisphenol epoxy resin with an epoxy equivalent of 150 or more and 400 or less, solder heat resistance was also not obtained. [Industrial Applicability]

[0090] The photosensitive resin composition of the present invention can prevent warping of a substrate even when subjected to a high-temperature atmosphere during a heat curing treatment, and is therefore highly useful particularly in the field of forming an insulating coating, which is a cured product, on a flexible printed wiring board.

Claims

1. (A) a photosensitive resin, (B) a photopolymerization initiator, (C) a reactive diluent, (D) an epoxy compound, and (E) a colorant; the (D) epoxy compound contains (D1) a bisphenol-type epoxy resin and (D2) a dimer acid glycidyl ester-type epoxy resin, the epoxy equivalent of the bisphenol epoxy resin (D1) is 500 or more and 1000 or less, A photosensitive resin composition comprising 20 parts by mass or more and 150 parts by mass or less of the dimer acid glycidyl ester type epoxy resin (D2) relative to 100 parts by mass of the bisphenol type epoxy resin (D1).

2. A composition comprising: (A) a photosensitive resin; (B) a photopolymerization initiator; (C) a reactive diluent; (D) an epoxy compound; and (E) a colorant; the (D) epoxy compound contains (D1) a bisphenol-type epoxy resin and (D2) a dimer acid glycidyl ester-type epoxy resin, the epoxy equivalent of the bisphenol epoxy resin (D1) is 500 or more and 1000 or less, a photosensitive resin composition in which the total amount of the bisphenol-type epoxy resin (D1) and the dimer acid glycidyl ester-type epoxy resin (D2) is 20 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the photosensitive resin (A).

3. A composition comprising: (A) a photosensitive resin; (B) a photopolymerization initiator; (C) a reactive diluent; (D) an epoxy compound; and (E) a colorant; the (D) epoxy compound contains (D1) a bisphenol-type epoxy resin and (D2) a dimer acid glycidyl ester-type epoxy resin, the epoxy equivalent of the bisphenol epoxy resin (D1) is 500 or more and 1000 or less, a photosensitive resin composition in which a total blending amount of the (D1) bisphenol-type epoxy resin and the (D2) dimer acid glycidyl ester-type epoxy resin is 40 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the (A) photosensitive resin.

4. A photosensitive resin composition described in any one of claims 1 to 3, wherein the epoxy equivalent of the (D1) bisphenol type epoxy resin is 600 or more and 800 or less.

5. 4. The photosensitive resin composition according to claim 1, wherein the bisphenol epoxy resin (D1) is a bisphenol A epoxy resin.

6. 4. The photosensitive resin composition according to claim 1, further comprising (D3) a bisphenol-type epoxy resin having an epoxy equivalent of 150 or more and 400 or less.

7. 7. The photosensitive resin composition according to claim 6, comprising 10 parts by mass or more and 100 parts by mass or less of the bisphenol-type epoxy resin (D3) having an epoxy equivalent of 150 or more and 400 or less per 100 parts by mass of the photosensitive resin (A).

8. 4. The photosensitive resin composition according to claim 1, wherein the colorant (E) is a white colorant.

9. 9. The photosensitive resin composition according to claim 8, wherein the white colorant is titanium oxide.

10. A cured product of the photosensitive resin composition according to any one of claims 1 to 3.

11. A flexible printed wiring board comprising the cured product according to claim 10.

12. A dry film comprising the photosensitive resin composition according to any one of claims 1 to 3.

Images