Photosensitive resin composition, photocured product of photosensitive resin composition, and printed wiring board having photocured film of photosensitive resin composition

Abstract

To provide a photosensitive resin composition which enables formation of an insulation film that is excellent in flux resistance without impairing various basic characteristics such as insulation reliability, coating film hardness, developability and tackiness.SOLUTION: A photosensitive resin composition contains (A) a carboxyl group-containing photosensitive resin, (B) a cationic polymerization initiator, (C) a photo-radical polymerization initiator, (D) an epoxy compound, and (E) a reactive diluent, wherein (C) the photo-radical polymerization initiator contains at least one selected from the group consisting of (C1) an α-aminoalkylphenone-based photopolymerization initiator and (C2) an oxime ester-based photopolymerization initiator.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photosensitive resin composition suitable as a coating material, for example, an insulating coating material for coating a conductor circuit pattern formed on a printed wiring board, a photocured product of the photosensitive resin composition, and a printed wiring board having a photocured film of the photosensitive resin composition. [Background technology]

[0002] A conductor circuit pattern such as copper foil is formed on the substrate of the printed wiring board, electronic components are mounted on the soldering lands of the conductor circuit pattern by soldering, and the conductor circuit portion excluding the soldering lands is covered with an insulating film (solder resist film) as a protective film. As the insulating film, a cured film of a photosensitive resin composition containing a carboxyl group-containing photosensitive resin and a photopolymerization initiator may be used. Therefore, the insulating film is required to have adhesion to the substrate of the printed wiring board, resolution, etc.

[0003] In view of this, a photosensitive resin composition of an alkali development type has been proposed that contains (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) a photosensitive monomer, and (D) a pigment as essential components, and contains (B-1) a phosphine oxide-based photoradical polymerization initiator and (B-2) a photocationic polymerization initiator as the photopolymerization initiator (B), and contains (C-1) a cationic curable monomer as the photosensitive monomer (C) (Patent Document 1). In Patent Document 1, by containing (B-2) a photocationic polymerization initiator and (C-1) a cationic curable monomer, cationic polymerization proceeds after development, resulting in an insulating coating that has excellent adhesion to the substrate.

[0004] On the other hand, in a mounting process in which electronic components are mounted on soldering lands of a conductor circuit pattern by soldering, the electronic components are placed on a printed wiring board on which an insulating coating has been formed, and the electronic components are soldered to the printed wiring board by a heat treatment in a reflow furnace. In the above mounting process, solder containing flux components may be used. When solder containing flux components is used, the flux components may seep out of the solder and permeate into the insulating coating from the surface of the insulating coating or the openings of the conductor circuit pattern.

[0005] If the flux components penetrate into the insulating coating, the insulating coating may peel off from the printed wiring board or blister, causing problems with the insulating coating. Therefore, the insulating coating may be required to have flux resistance that can prevent the insulating coating from peeling off or swelling from the printed wiring board even if the flux components seep out from the solder.

[0006] However, in the insulating coating formed from the photosensitive resin composition of Patent Document 1, when flux components seep out from the solder, the flux components permeate into the insulating coating, which can cause the insulating coating to peel off from the printed wiring board or swell, leaving room for improvement in flux resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2007-017458 A 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 capable of forming an insulating coating having excellent flux resistance without impairing the basic properties of insulation reliability, coating hardness, developability, and tackiness. [Means for solving the problem]

[0009] The gist of the configuration of the present invention is as follows. [1] A composition comprising: (A) a carboxyl group-containing photosensitive resin; (B) a cationic polymerization initiator; (C) a photoradical polymerization initiator; (D) an epoxy compound; and (E) a reactive diluent; The photosensitive resin composition, wherein the (C) photoradical polymerization initiator contains at least one member selected from the group consisting of (C1) an α-aminoalkylphenone-based photopolymerization initiator and (C2) an oxime ester-based photopolymerization initiator. [2] The photosensitive resin composition according to [1], wherein the anion moiety of the (B) cationic polymerization initiator is phosphorus-based or antimony-based. [3] The photosensitive resin composition according to [1], wherein the anion moiety of the (B) cationic polymerization initiator is phosphorus-based. [4] The photosensitive resin composition according to any one of [1] to [3], wherein the cationic moiety of the (B) cationic polymerization initiator is an aromatic compound having three or less aromatic rings in one molecule. [5] The photosensitive resin composition according to any one of [1] to [3], wherein the cationic moiety of the (B) cationic polymerization initiator is an aromatic compound having two or less aromatic rings in one molecule. [6] The photosensitive resin composition according to any one of [1] to [5], wherein the (C1) α-aminoalkylphenone-based photopolymerization initiator contains 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone. [7] The photosensitive resin composition according to any one of [1] to [6], wherein the (C2) oxime ester photopolymerization initiator contains (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime. [8] The photosensitive resin composition according to any one of [1] to [7], wherein the (D) epoxy compound contains at least one selected from the group consisting of cresol novolac epoxy resins, bisphenol A epoxy resins, biphenyl aralkyl epoxy resins, and triglycidyl isocyanurate. [9] The photosensitive resin composition according to any one of [1] to [7], wherein the (D) epoxy compound contains at least two kinds selected from the group consisting of cresol novolac epoxy resins, bisphenol A epoxy resins, biphenyl aralkyl epoxy resins, and triglycidyl isocyanurate.

[10] The photosensitive resin composition according to any one of [1] to [7], wherein the (D) epoxy compound contains a cresol novolac epoxy resin and triglycidyl isocyanurate.

[11] A photocured product of the photosensitive resin composition according to any one of [1] to

[10] .

[12] A printed wiring board having a photocured film of the photosensitive resin composition according to any one of [1] to

[10] . Effect of the Invention

[0010] According to an embodiment of the photosensitive resin composition of the present invention, the photosensitive resin composition contains (A) a carboxyl group-containing photosensitive resin, (B) a cationic polymerization initiator, (C) a photoradical polymerization initiator, (D) an epoxy compound, and (E) a reactive diluent, and the (C) photoradical polymerization initiator contains at least one selected from the group consisting of (C1) an α-aminoalkylphenone-based photopolymerization initiator and (C2) an oxime ester-based photopolymerization initiator. This improves the crosslink density of the (D) epoxy compound without impairing the basic properties of insulation reliability, coating hardness, developability, and tackiness, thereby making it possible to obtain a photosensitive resin composition that can form an insulating coating film with excellent flux resistance.

[0011] According to an embodiment of the photosensitive resin composition of the present invention, the anion moiety of the (B) cationic polymerization initiator is phosphorus-based or antimony-based, whereby the crosslink density of the (D) epoxy compound is reliably improved and excellent flux resistance can be reliably obtained.

[0012] According to an embodiment of the photosensitive resin composition of the present invention, the anion moiety of the (B) cationic polymerization initiator is phosphorus-based, whereby the crosslink density of the (D) epoxy compound is further improved, and further excellent coating hardness can be obtained.

[0013] According to an embodiment of the photosensitive resin composition of the present invention, the cationic moiety of the (B) cationic polymerization initiator is an aromatic compound having 3 or less aromatic rings in one molecule, whereby the crosslink density of the (D) epoxy compound is improved and excellent flux resistance can be reliably obtained.

[0014] According to an embodiment of the photosensitive resin composition of the present invention, the cationic moiety of the (B) cationic polymerization initiator is an aromatic compound having two or less aromatic rings in one molecule, whereby insulation reliability, coating hardness, developability, and tackiness are improved in a well-balanced manner, and the crosslink density of the (D) epoxy compound is further improved, thereby enabling further improvement in flux resistance.

[0015] According to an embodiment of the photosensitive resin composition of the present invention, the (C1) α-aminoalkylphenone photopolymerization initiator contains 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone, and this, together with the cationic polymerization activity of the (B) cationic polymerization initiator, ensures excellent flux resistance.

[0016] According to an embodiment of the photosensitive resin composition of the present invention, the (C2) oxime ester photopolymerization initiator contains (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime, and this, together with the cationic polymerization activity of the (B) cationic polymerization initiator, ensures excellent flux resistance.

[0017] According to an embodiment of the photosensitive resin composition of the present invention, the (D) epoxy compound contains at least one selected from the group consisting of cresol novolac epoxy resins, bisphenol A epoxy resins, biphenyl aralkyl epoxy resins, and triglycidyl isocyanurate, whereby the crosslink density of the (D) epoxy compound is reliably improved and excellent flux resistance can be reliably obtained.

[0018] According to an embodiment of the photosensitive resin composition of the present invention, the (D) epoxy compound contains at least two selected from the group consisting of cresol novolac epoxy resins, bisphenol A epoxy resins, biphenyl aralkyl epoxy resins, and triglycidyl isocyanurate, whereby the tackiness is further improved.

[0019] According to an embodiment of the photosensitive resin composition of the present invention, the (D) epoxy compound contains a cresol novolac epoxy resin and triglycidyl isocyanurate, so that all of the flux resistance, insulation reliability, and coating hardness are further improved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Next, the photosensitive resin composition of the present invention will be described below. The photosensitive resin composition of the present invention contains (A) a carboxyl group-containing photosensitive resin, (B) a cationic polymerization initiator, (C) a photoradical polymerization initiator, (D) an epoxy compound, and (E) a reactive diluent, and the (C) photoradical polymerization initiator contains at least one selected from the group consisting of (C1) an α-aminoalkylphenone-based photopolymerization initiator and (C2) an oxime ester-based photopolymerization initiator. In the photosensitive resin composition of the present invention, the (B) cationic polymerization initiator and the (C) photoradical polymerization initiator are blended as polymerization initiators. In the photosensitive resin composition of the present invention, the crosslink density of the (D) epoxy compound is improved without impairing the basic properties of insulation reliability, coating hardness, developability, and tackiness, and an insulating coating film with excellent flux resistance can be formed.

[0021] <(A) Carboxyl group-containing photosensitive resin> The carboxyl group-containing photosensitive resin, which is the component (A), is the base resin of the photosensitive resin composition. The structure of the carboxyl group-containing photosensitive resin is not particularly limited, and examples thereof include resins having one or more photosensitive unsaturated double bonds and free carboxyl groups. Examples of the carboxyl group-containing photosensitive resin include (A1) a polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin (A1 resin) having a structure obtained by reacting at least a part of the epoxy groups of a polyfunctional epoxy resin having two or more epoxy groups in one molecule with a radically polymerizable unsaturated monocarboxylic acid to obtain a radically polymerizable unsaturated monocarboxylated epoxy resin, and then reacting the resulting hydroxyl groups with a polybasic acid and / or a polybasic acid anhydride; (A2) a polybasic acid-modified radically polymerizable unsaturated monocarboxylic acid having a radically polymerizable unsaturated group further introduced therein; and (A3) an acid-modified urethane-modified unsaturated monocarboxylated epoxy resin (A3 resin) having a structure obtained by reacting at least a part of the epoxy groups of a multifunctional epoxy resin having two or more epoxy groups in one molecule with a radically polymerizable unsaturated monocarboxylic acid to obtain an unsaturated monocarboxylated epoxy resin, then subjecting the hydroxyl groups thus generated to an addition reaction with a polyisocyanate compound, and further subjecting the isocyanate groups of the addition-reacted polyisocyanate compound to an addition reaction with a compound having a hydroxyl group and a carboxyl group.

[0022] (A1) Polybasic acid modified radically polymerizable unsaturated monocarboxylated epoxy resin Multifunctional Epoxy Resin The epoxy equivalent of the multifunctional epoxy resin is not particularly limited, and for example, the upper limit is preferably 3000 g / eq, more preferably 2000 g / eq, further preferably 1000 g / eq, and particularly preferably 500 g / eq. On the other hand, the lower limit of the epoxy equivalent of the multifunctional epoxy resin is preferably 100 g / eq, and particularly preferably 200 g / eq. The polyfunctional epoxy resin is not particularly limited, and examples thereof include rubber-modified epoxy resins such as biphenylaralkyl type epoxy resins, phenylaralkyl type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, silicone-modified epoxy resins, etc., ε-caprolactone-modified epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, cresol novolac type epoxy resins such as ortho-cresol novolac type, bisphenol novolac type epoxy resins, cyclic aliphatic polyfunctional epoxy resins, glycidyl ester type polyfunctional epoxy resins, glycidyl amine type polyfunctional epoxy resins, heterocyclic polyfunctional epoxy resins, bisphenol-modified novolac type epoxy resins, polyfunctional modified novolac type epoxy resins, etc. These may be used alone or in combination of two or more.

[0023] Radical polymerizable unsaturated monocarboxylic acid The carboxyl group of the radically polymerizable unsaturated monocarboxylic acid reacts with the epoxy group of the polyfunctional epoxy resin to form an ester bond, thereby introducing a photosensitive unsaturated double bond into the epoxy resin, and imparting photosensitivity to the skeleton of the polyfunctional epoxy resin. Examples of the radically polymerizable unsaturated monocarboxylic acid include acrylic acid, methacrylic acid (acrylic acid and / or methacrylic acid may be referred to as "(meth)acrylic acid"), crotonic acid, tiglic acid, angelic acid, and cinnamic acid. Among these, (meth)acrylic acid is preferred in terms of reactivity, availability, and handling. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

[0024] The method for reacting the polyfunctional epoxy resin with the radical polymerizable unsaturated monocarboxylic acid is not particularly limited, and examples thereof include a method in which the polyfunctional epoxy resin and the radical polymerizable unsaturated monocarboxylic acid are heated in an appropriate dispersion medium (e.g., an inert organic solvent).

[0025] Polybasic acids and / or polybasic acid anhydrides The polybasic acid and / or polybasic acid anhydride undergoes an addition reaction with the hydroxyl group of the unsaturated monocarboxylated epoxy resin, thereby introducing a free carboxyl group into the photosensitive resin. The polybasic acid and / or polybasic acid anhydride is not particularly limited, and either saturated or unsaturated may be used. Examples of polybasic acids include succinic acid, maleic acid, adipic acid, citric acid, phthalic acid, tetrahydrophthalic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, 3-ethyltetrahydrophthalic acid, 4-ethyltetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, and other tetrahydrophthalic acids, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid, 4-ethylhexahydrophthalic acid, and other hexahydrophthalic acids, difunctional carboxylic acids such as diglycolic acid, trifunctional carboxylic acids such as trimellitic acid, and tetrafunctional carboxylic acids such as pyromellitic acid. Examples of polybasic acid anhydrides include the anhydrides of the polybasic acids described above. These polybasic acids and polybasic acid anhydrides may be used alone or in combination of two or more.

[0026] The method for reacting the radically polymerizable unsaturated monocarboxylated epoxy resin with the polybasic acid and / or polybasic acid anhydride is not particularly limited, and examples thereof include a method in which the radically polymerizable unsaturated monocarboxylated epoxy resin and the polybasic acid and / or polybasic acid anhydride are heated in a suitable dispersion medium (e.g., an inert organic solvent).

[0027] (A2) Polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin further having a radically polymerizable unsaturated group introduced therein In addition, if necessary, a carboxyl group-containing photosensitive resin having a chemical structure in which a compound having one or more radically polymerizable unsaturated groups and an epoxy group (for example, a glycidyl compound) is further reacted with a part of the carboxyl group of the polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin may be used. The carboxyl group-containing photosensitive resin in which a compound having a radically polymerizable unsaturated group and an epoxy group is further reacted has a chemical structure in which a radically polymerizable unsaturated group is further introduced into the side chain of the polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin. Therefore, the carboxyl group-containing photosensitive resin having a chemical structure in which a compound having a radically polymerizable unsaturated group and an epoxy group is reacted has better photopolymerization reactivity and further improved photosensitive properties than the polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin.

[0028] Examples of compounds having a radically polymerizable unsaturated group and an epoxy group include glycidyl acrylate, glycidyl methacrylate (acrylate and / or methacrylate may be referred to as "(meth)acrylate"), allyl glycidyl ether, pentaerythritol tri(meth)acrylate monoglycidyl ether, etc. These compounds having a radically polymerizable unsaturated group and an epoxy group may be used alone or in combination of two or more kinds.

[0029] (A3) Acid-modified urethane-modified unsaturated monocarboxylated epoxy resin Multifunctional Epoxy Resin The polyfunctional epoxy resin is not particularly limited, but like the (A1) polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin, examples of the polyfunctional epoxy resin include rubber-modified epoxy resins such as biphenylaralkyl type epoxy resins, phenylaralkyl type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, silicone-modified epoxy resins, ε-caprolactone-modified epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, cresol novolac type epoxy resins such as ortho-cresol novolac type, bisphenol novolac type epoxy resins, cyclic aliphatic polyfunctional epoxy resins, glycidyl ester type polyfunctional epoxy resins, glycidyl amine type polyfunctional epoxy resins, heterocyclic polyfunctional epoxy resins, bisphenol-modified novolac type epoxy resins, polyfunctional modified novolac type epoxy resins, etc. These may be used alone or in combination of two or more.

[0030] Radical polymerizable unsaturated monocarboxylic acid The radical polymerizable unsaturated monocarboxylic acid is not particularly limited, but may be, for example, (meth)acrylic acid, crotonic acid, tiglic acid, angelic acid, cinnamic acid, etc., as in the (A1) polybasic acid-modified radical polymerizable unsaturated monocarboxylated epoxy resin. Among these, (meth)acrylic acid is preferred from the viewpoints of reactivity, availability, and handling. These radical polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

[0031] Polyisocyanate Compounds 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, toluene diisocyanate, 1,2-diphenylethane diisocyanate, 1,3-diphenylpropane diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethyl diisocyanate, etc. These polyisocyanate compounds may be used alone or in combination of two or more kinds.

[0032] Compounds containing hydroxyl and carboxyl groups 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 may be used alone or in combination of two or more kinds.

[0033] The above-mentioned A1 resin, A2 resin, and A3 resin may be used alone or in combination of two or more kinds.

[0034] The acid value of the carboxyl group-containing photosensitive resin is not particularly limited, and for example, the lower limit is preferably 30 mgKOH / g and particularly preferably 40 mgKOH / g from the viewpoint of reliably imparting alkaline developability, while the upper limit of the acid value of the carboxyl group-containing photosensitive resin is preferably 200 mgKOH / g from the viewpoint of reliably preventing dissolution of the exposed portion (photocured portion) by an alkaline developer, and particularly preferably 150 mgKOH / g from the viewpoint of reliably improving the insulation reliability of the photocured product.

[0035] The mass average molecular weight of the carboxyl group-containing photosensitive resin is not particularly limited and can be appropriately selected depending on the conditions of use, etc. For example, the lower limit is preferably 6000, more preferably 7000, and particularly preferably 8000, from the viewpoint of contributing to improving the toughness and tackiness of the photocured product. On the other hand, the upper limit of the mass average molecular weight of the carboxyl group-containing photosensitive resin is preferably 200000, more preferably 100000, and particularly preferably 50000, from the viewpoint of contributing to improving the alkali developability. The above-mentioned "mass average molecular weight" means a mass average molecular weight measured at room temperature using gel permeation chromatography (GPC) and calculated in terms of polystyrene.

[0036] The carboxyl group-containing photosensitive resin may be prepared by the above-mentioned reaction process using each of the above-mentioned components, or a commercially available carboxyl group-containing photosensitive resin may be used. Examples of commercially available carboxyl group-containing photosensitive resins include "Lipoxy SP-4621", "Lipoxy SP-4785L" (both from Showa Denko K.K.), "ZAR-2000", "ZFR-1122", "ZFR-1887", "FLX-2089", "ZCR-1569H", "ZCR-1601H" (both from Nippon Kayaku Co., Ltd.), and "Cyclomer P(ACA)Z-250" (Daicel Corporation).

[0037] <(B) Cationic Polymerization Initiator> The incorporation of the cationic polymerization initiator, component (B), improves the cationic polymerization activity, thereby improving the crosslink density of the epoxy compound (D). Combined with the radical polymerization activity of the photoradical polymerization initiator (C), which will be described later, this inhibits the penetration of flux components into the insulating coating, enabling the formation of an insulating coating with excellent flux resistance.

[0038] As the cationic polymerization initiator, for example, the anion portion is PF6 - Phosphorus-based compounds such as SbF6 - Antimony series, BF4 - , [BX4] -(X represents a functional group in which two or more hydrogen atoms of a phenyl group are substituted with a fluorine atom or a trifluoromethyl group), and the cationic portion is composed of an aromatic sulfonium, aromatic iodonium, aromatic diazonium, aromatic ammonium, thioxanthonium, etc.

[0039] As the anion portion of the cationic polymerization initiator, phosphorus-based and antimony-based initiators are preferred since the crosslink density of the epoxy compound (D) is reliably improved and excellent flux resistance can be reliably obtained, and phosphorus-based initiators are particularly preferred since the crosslink density of the epoxy compound (D) is further improved and even better coating hardness can be obtained.

[0040] As the cationic portion of the cationic polymerization initiator, aromatic sulfonium, aromatic iodonium, aromatic diazonium, and aromatic ammonium, which are compounds having aromatic rings, are preferred, and aromatic sulfonium is particularly preferred from the viewpoint of reliably obtaining flux resistance. As the compound having an aromatic ring, which is the cationic portion of the cationic polymerization initiator, an aromatic compound having 3 or less aromatic rings in one molecule is preferred from the viewpoint of improving the crosslink density of the (D) epoxy compound and reliably obtaining excellent flux resistance, and an aromatic compound having 2 or less aromatic rings in one molecule is particularly preferred from the viewpoint of improving insulation reliability, coating hardness, developability, and tackiness in a well-balanced manner, and further improving the crosslink density of the (D) epoxy compound and further improving flux resistance.

[0041] Examples of aromatic sulfonium salts include benzyl(4-hydroxyphenyl)methylsulfonium hexafluorophosphate, benzyl(4-hydroxyphenyl)methylsulfonium hexafluoroantimonate, dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroantimonate, dimethyl-p-acetoxyphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium tetrafluoroborate, benzyl(4-acetoxyphenyl)methylsulfonium hexafluorophosphate, benzyl(4-acetoxyphenyl)methylsulfonium hexafluoroantimonate, dimethyl-4-hydroxyphenylsulfonium hexafluoroantimonate, dimethyl-4-hydroxyphenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, and diphenyl-4-(phenylthio)phenylsulfonium. tetrafluoroborate and the like.

[0042] Examples of aromatic iodonium salts include diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, and 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate.

[0043] Examples of aromatic diazonium salts include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, and phenyldiazonium tetrafluoroborate.

[0044] Examples of aromatic ammonium salts include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, and 1-benzyl-2-cyanopyridinium tetrafluoroborate.

[0045] Examples of cationic polymerization initiators on the market include "SAN-AID SI-60L", "SAN-AID SI-80L", "SAN-AID SI-100L", "SAN-AID SI-110L", "SAN-AID SI-150L", "SAN-AID SI-180L", "SAN-AID SI-80", "SAN-AID SI-100", "SAN-AID SI-110", "SAN-AID SI-145", "SAN-AID SI-150", "SAN-AID SI-160", "SAN-AID SI-180", "SAN-AID SI-300", and "SAN-AID SI-360" (all from Sanshin Chemical Industry Co., Ltd.), "ADEKA OPTOMER SP-150", "ADEKA OPTOMER SP-170", and "ADEKA OPTOMER SP-172" (all from ADEKA Corporation).

[0046] These cationic polymerization initiators may be used alone or in combination of two or more kinds.

[0047] The amount of the cationic polymerization initiator is not particularly limited, but the lower limit is preferably 0.50 parts by mass, more preferably 1.0 parts by mass, and particularly preferably 1.5 parts by mass, relative to 100 parts by mass of the carboxyl group-containing photosensitive resin (A), from the viewpoint of reliably improving the crosslink density of the epoxy compound (D) and reliably obtaining excellent flux resistance. On the other hand, the upper limit of the amount of the cationic polymerization initiator is preferably 10 parts by mass, more preferably 8.0 parts by mass, and particularly preferably 6.0 parts by mass, relative to 100 parts by mass of the carboxyl group-containing photosensitive resin (A), from the viewpoint of preventing a decrease in developability.

[0048] <(C) Photoradical polymerization initiator> The incorporation of the photoradical polymerization initiator, component (C), in combination with the cationic polymerization activity of the cationic polymerization initiator improves the hardening of the insulating coating and inhibits the penetration of flux components into the insulating coating, resulting in the formation of an insulating coating with excellent flux resistance.

[0049] The photosensitive resin composition of the present invention contains, as a photoradical polymerization initiator, at least one selected from the group consisting of (C1) an α-aminoalkylphenone-based photopolymerization initiator and (C2) an oxime ester-based photopolymerization initiator.

[0050] The α-aminoalkylphenone-based photopolymerization initiator, which is the component (C1), is, for example, a compound represented by the following general formula (1): [ka] (in formula (1), R represents hydrogen or an alkyl group having 1 to 5 carbon atoms). Among these, 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone (in formula (1), R represents a methyl group) is preferred as the α-aminoalkylphenone photopolymerization initiator, since it reliably improves the curability of the insulating coating and reliably provides excellent flux resistance. These α-aminoalkylphenone photopolymerization initiators may be used alone or in combination of two or more kinds.

[0051] The oxime ester photopolymerization initiator (C2) is, for example, (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone. Examples of such oxime include O-acetyloxime, 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), and the like. Among these, (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime is preferred, since it reliably improves the curing property of the insulating coating and reliably obtains excellent flux resistance. These oxime ester photopolymerization initiators may be used alone, or two or more of them may be used in combination.

[0052] The amount of at least one photoradical polymerization initiator selected from the group consisting of α-aminoalkylphenone-based photopolymerization initiators and oxime ester-based photopolymerization initiators is not particularly limited, but the lower limit is preferably 0.50 parts by mass, more preferably 1.0 parts by mass, and particularly preferably 1.5 parts by mass relative to 100 parts by mass of (A) carboxyl group-containing photosensitive resin, from the viewpoint of reliably improving the curability of the insulating coating and reliably obtaining excellent flux resistance. On the other hand, the upper limit of the amount of at least one photoradical polymerization initiator selected from the group consisting of α-aminoalkylphenone-based photopolymerization initiators and oxime ester-based photopolymerization initiators relative to 100 parts by mass of (A) carboxyl group-containing photosensitive resin, from the viewpoint of preventing a decrease in developability and halation, is preferably 8.0 parts by mass, more preferably 6.0 parts by mass, and particularly preferably 4.0 parts by mass.

[0053] <(D) Epoxy compound> The epoxy compound, component (D), is intended to increase the crosslink density of the photocured product of the photosensitive resin composition to impart sufficient hardness to the photocured product. The increased crosslink density of the epoxy compound inhibits the flux component from penetrating into the insulating coating, thereby contributing to the formation of an insulating coating with excellent flux resistance.

[0054] Examples of the epoxy compound include epoxy resins. Examples of the epoxy resin include the same epoxy resins as the polyfunctional epoxy resins that can be used to prepare the above-mentioned carboxyl group-containing photosensitive resin. Specifically, examples of the epoxy resin include rubber-modified epoxy resins such as biphenylaralkyl-type epoxy resins, phenylaralkyl-type epoxy resins, biphenyl-type epoxy resins, naphthalene-type epoxy resins, dicyclopentadiene-type epoxy resins, and silicone-modified epoxy resins, ε-caprolactone-modified epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, cresol novolac-type epoxy resins such as ortho-cresol novolac-type epoxy resins, bisphenol novolac-type epoxy resins, cyclic aliphatic polyfunctional epoxy resins, glycidyl ester-type polyfunctional epoxy resins, glycidyl amine-type polyfunctional epoxy resins, heterocyclic polyfunctional epoxy resins, bisphenol-modified novolac-type epoxy resins, and polyfunctional modified novolac-type epoxy resins. Examples of the epoxy compound other than the epoxy resin include triglycidyl isocyanurate. These epoxy compounds may be used alone or in combination of two or more kinds.

[0055] Among these epoxy compounds, it is preferable to contain at least one selected from the group consisting of cresol novolac type epoxy resins, bisphenol A type epoxy resins, biphenyl aralkyl type epoxy resins, and triglycidyl isocyanurate, since the crosslink density of the epoxy compound is reliably improved and excellent flux resistance can be reliably obtained. It is more preferable to contain at least two selected from the group consisting of cresol novolac type epoxy resins, bisphenol A type epoxy resins, biphenyl aralkyl type epoxy resins, and triglycidyl isocyanurate, since tackiness is further improved. It is particularly preferable to contain cresol novolac type epoxy resins and triglycidyl isocyanurate, since all of flux resistance, insulation reliability, and coating hardness are further improved.

[0056] The amount of the epoxy compound is not particularly limited, but the lower limit is preferably 5.0 parts by mass, more preferably 10 parts by mass, and particularly preferably 15 parts by mass, relative to 100 parts by mass of the carboxyl group-containing photosensitive resin (A) from the viewpoint of obtaining an insulating coating having sufficient hardness after photocuring of the photosensitive resin composition. On the other hand, the upper limit of the amount of the epoxy compound is preferably 50 parts by mass, more preferably 40 parts by mass, and particularly preferably 30 parts by mass, relative to 100 parts by mass of the carboxyl group-containing photosensitive resin (A) from the viewpoint of preventing a decrease in developability.

[0057] <(E) Reactive Diluent> The reactive diluent, which is the component (E), is, for example, a photopolymerizable monomer, and 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 imparting sufficient strength, heat resistance, acid resistance, alkali resistance, etc. to the cured coating film of the photosensitive resin composition.

[0058] Examples of reactive diluents include monomers of monofunctional or polyfunctional (meth)acrylate compounds, such as monofunctional (meth)acrylate compounds, difunctional (meth)acrylate compounds, trifunctional (meth)acrylate compounds, and tetrafunctional or higher (meth)acrylate compounds. Examples of the (meth)acrylate compound monomer include monofunctional (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, diethylene glycol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl (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, ethylene oxide-modified phosphate di(meth)acrylate, and allylated cyclohexyl acrylate. Examples of the acrylate include bifunctional (meth)acrylate compounds such as xyl 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 (meth)acrylate compounds such as ditrimethylolpropane tetra(meth)acrylate, propionic acid modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone modified dipentaerythritol hexa(meth)acrylate. These may be used alone or in combination of two or more.

[0059] The amount of the reactive diluent is not particularly limited, but is preferably from 5.0 to 70 parts by mass, and particularly preferably from 15 to 40 parts by mass, per 100 parts by mass of the carboxyl group-containing photosensitive resin (A).

[0060] In addition to the above-described components (A) to (E), the photosensitive resin composition of the present invention may further contain, as an optional component, a photoradical polymerization initiator other than the α-aminoalkylphenone-based photopolymerization initiator and the oxime ester-based photopolymerization initiator, if necessary. Other photoradical polymerization initiators include, for example, benzoin-based initiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, and benzoin isobutyl ether; acetophenone-based initiators such as acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and 2,2-diethoxy-2-phenylacetophenone; benzophenone-based initiators such as benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, and dichlorobenzophenone; anthraquinone-based initiators such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, and 2-aminoanthraquinone; 2-methylthioxanthone, 2-ethylthioxanthone, 2-chloroanthraquinone, and Thioxanthone-based compounds such as oxanthone, 2,4-dimethylthioxanthone, and 2,4-diethylthioxanthone; benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ethyl ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone. These other photoradical polymerization initiators may be used alone or in combination of two or more.

[0061] The photosensitive resin composition of the present invention may further contain other optional components, such as inorganic fillers, colorants, additives, antifoaming agents, flame retardants, non-reactive diluents, etc., as required.

[0062] Examples of the inorganic filler include aluminum hydroxide, barium sulfate, mica, talc, and silica.

[0063] The colorant is not particularly limited to pigments, dyes, etc., and any colorant can be used depending on the desired color, such as white colorants, black colorants, blue colorants, green colorants, yellow colorants, purple colorants, orange colorants, red colorants, etc. Examples of the colorant include inorganic colorants such as titanium dioxide, which is a white colorant, acetylene black, carbon black, which are black colorants, and organic colorants such as phthalocyanine-based colorants such as phthalocyanine green, which is a green colorant, phthalocyanine blue, lyonol blue, which are blue colorants, and diketopyrrolopyrrole-based colorants such as chromophthalic orange, which is an orange colorant. These colorants may be used alone or in combination of two or more.

[0064] Examples of additives include latent curing agents such as mercaptobenzoxazal and its derivatives, 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, aminimide (AI), and polyamine, and heat curing catalysts such as aliphatic dimethylurea.

[0065] Examples of the defoaming agent include silicone-based polymers, hydrocarbon-based polymers, and acrylic polymers.

[0066] The flame retardant is intended to impart flame retardancy to the insulating coating of the photosensitive resin composition. Examples of the flame retardant include phosphorus-based flame retardants, and organic phosphate-based flame retardants are preferred. Examples of the phosphorus-based flame retardant include halogen-containing phosphate esters 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; trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, and tributyl phosphate; non-halogenated aliphatic phosphate esters such as toxyethyl phosphate; non-halogenated aromatic phosphate esters such as triphenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, tricresyl phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, tris(isopropylphenyl)phosphate, isopropylphenyl diphenyl phosphate, diisopropylphenyl phosphate, tris(trimethylphenyl)phosphate, tris(t-butylphenyl)phosphate, hydroxyphenyl diphenyl phosphate, and octyl diphenyl phosphate;Examples of the metal salts of phosphinic acid include 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; HCA-modified compounds such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter referred to as HCA), addition reaction products of HCA and acrylic acid esters, addition reaction products of HCA and epoxy resins, and addition reaction products of HCA and hydroquinone; and phosphine oxide compounds such as diphenylvinylphosphine oxide, triphenylphosphine oxide, trialkylphosphine oxide, and tris(hydroxyalkyl)phosphine oxide.

[0067] The non-reactive diluent is a component for adjusting the viscosity, coatability and drying property of the photosensitive resin composition. Examples of the non-reactive diluent include organic solvents that are inactive to each component blended in the photosensitive resin composition. Examples of the organic solvent include ketones such as methyl ethyl ketone, aromatic hydrocarbons such as benzene, toluene, and xylene, alcohols such as methanol, ethanol, n-propanol, isopropanol, and cyclohexanol, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, petroleum solvents such as petroleum ether and petroleum naphtha, cellosolves such as cellosolve and butyl cellosolve, carbitols such as carbitol and butyl carbitol, esters such as ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, ethylene glycol acetate, and diethylene glycol monoethyl ether acetate. These may be used alone or in combination of two or more.

[0068] The method for producing the photosensitive resin composition of the present invention is not limited to a specific method, and can be produced, for example, by blending the above-mentioned components in a predetermined ratio, and then kneading or mixing the blended components 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, a kneader, or a stirring or mixing means such as a super mixer, a planetary mixer, a trimix, etc. Furthermore, prior to the kneading or mixing, pre-kneading or pre-mixing may be carried out as necessary.

[0069] Next, an example of a method for using the photosensitive resin composition of the present invention will be described. Here, a method for forming an insulating film (e.g., a solder resist film, etc.) by applying the photosensitive resin composition of the present invention to a printed wiring board will be described.

[0070] The photosensitive resin composition of the present invention obtained as described above is applied to a desired thickness, for example, on a printed wiring board having a circuit pattern formed by etching a copper foil, 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, a gravure coater, etc. Next, an exposure process is performed in which active energy rays (e.g., laser light) are directly irradiated onto the applied photosensitive resin composition according to a desired pattern using a direct imaging device, and the coating film is photocured in the pattern. The exposure dose is, for example, 50 mJ / cm. 2 ~2000mJ / cm 2 Next, the coating film is developed by removing the non-exposed region with a dilute alkaline aqueous solution. For example, the spray method, shower method, etc. are used as the developing method, and for example, a 0.5 to 5 mass % aqueous sodium carbonate solution is used as the dilute alkaline aqueous solution. Next, the developed coating film is thermally cured by performing post-cure (thermal curing treatment) for 20 to 80 minutes in a hot air circulation dryer at 130 to 170°C, etc., to form a photocured film (photocured product) having a desired pattern on the printed wiring board.

[0071] In addition, instead of the exposure treatment in which active energy rays are directly irradiated according to a desired pattern using the above-mentioned direct imaging device, an exposure treatment may be performed in which a coating film made tack-free by pre-drying the coating film by heating at a temperature of about 60 to 100°C for about 15 to 60 minutes after application of the photosensitive resin composition of the present invention is adhered to a negative film (photomask) having a pattern in which areas other than the lands of the circuit pattern are transparent, and active energy rays (e.g., ultraviolet rays having a wavelength of 300 to 400 nm) are irradiated from above to photocure the coating film. EXAMPLES

[0072] Examples 1 to 19, Comparative Example 1 The components shown in Table 1 below were mixed in the ratios shown in Table 1 below and mixed at room temperature using a three-roll mill to prepare photosensitive resin compositions used in Examples 1 to 19 and Comparative Example 1. The prepared photosensitive resin compositions were then applied to substrates as described below to prepare test specimens. The amount of each component shown in Table 1 below is in parts by mass unless otherwise specified. Note that blank spaces in the amounts in Table 1 below mean that no component was mixed.

[0073] Details of each component in Table 1 below are as follows. (A) Carboxyl group-containing photosensitive resin Lipoxy SP-4785: Polybasic acid modified unsaturated monocarboxylated epoxy resin with glycidyl methacrylate modified cresol novolac structure, solid content (resin content) 65% by mass, diethylene glycol monoethyl ether acetate 35% by mass, Showa Denko K.K. ZCR-1601H: Polybasic acid modified unsaturated monocarboxylated epoxy resin with bisphenol novolac structure, solid content (resin content) 65% by mass, diethylene glycol monoethyl ether acetate 35% by mass, Nippon Kayaku Co., Ltd. FLX-2089: Acid-modified urethane unsaturated monocarboxylated epoxy resin, solids (resin content) 65% by mass, diethylene glycol monoethyl ether acetate 35% by mass, Nippon Kayaku Co., Ltd.

[0074] (B) Cationic polymerization initiator San-Aid SI-110: Benzyl (4-hydroxyphenyl) methylsulfonium hexafluorophosphate (aromatic ring number 2), Sanshin Chemical Industry Co., Ltd. San-Aid SI-150L: Dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate (number of aromatic rings: 1), Sanshin Chemical Industry Co., Ltd. San-Aid SI-100L: Benzyl (4-hydroxyphenyl) methylsulfonium hexafluoroantimonate (number of aromatic rings: 2), Sanshin Chemical Industry Co., Ltd. ADEKA Optomer SP170: Triphenylsulfonium hexafluoroantimonate (aromatic ring number 3), ADEKA Corporation

[0075] (C) Photoradical polymerization initiator Omnirad379: IGM Resins BV

[0076] (D) Epoxy compounds N-695: Cresol novolac epoxy resin, DIC Corporation TEPIC: Triglycidyl isocyanurate, Nissan Chemical Industries, Ltd. NC-3000: Biphenyl aralkyl type epoxy resin, Nippon Kayaku Co., Ltd. EPICLON860: Bisphenol A epoxy resin, DIC Corporation ·VG3101L: High heat-resistant trifunctional epoxy resin, Printec Co., Ltd.

[0077] (E) Reactive diluent ·KAYARAD DPCA-20: Nippon Kayaku Co., Ltd.

[0078] Inorganic Filler ·EF-013: Nippon Light Metal Co., Ltd. Coloring agent Carbon black: Toyo Ink Mfg. Co., Ltd. Additives DICY-7: Mitsubishi Chemical Corporation ·U-CAT 3513N: San-Apro Co., Ltd. Melamine: Nissan Chemical Industries, Ltd. Defoamer ·AC-2300C: Shin-Etsu Chemical Co., Ltd. Flame retardants · Exolit OP-935: Clariant Japan Co., Ltd. Non-reactive diluents ·EDGAC: Sanyo Chemical Industries, Ltd.

[0079] Test specimen production process The photosensitive resin compositions of the Examples and Comparative Examples prepared as described above were applied onto a substrate to prepare test specimens having a cured coating film on the substrate, as described below. Substrate: 2-layer FCCL (flexible copper clad laminate) (Cu foil: thickness 12.5 μm, polyimide film thickness: 25 μm) Surface treatment: Soft etching treatment Coating method: Screen printing Pre-drying: 80℃ in oven for 20 minutes Dry film thickness (20±5μm) Exposure: 100mJ / cm on coating 2 Exposure device: Orbotech's direct imaging (DI) exposure device "Nuvogo1000R" (light source: laser) Development: 1% by weight sodium carbonate aqueous solution, development temperature 30°C, spray pressure 0.2MPa Post cure (thermal hardening): 150℃ in oven for 60 minutes

[0080] (1) Flux resistance A frame with polyimide tape laminated (150μm thick) was placed on the open pattern of the cured coating on the Cu foil, and the inside of the frame was filled with rosin-based flux. The lid was then placed on the frame, and reflow was performed using a reflow furnace (product name: TNP-538EM, Tamura Corporation) under the following conditions: preheat temperature 150-180°C, 80 seconds, peak temperature 240°C, 40 seconds. After reflow, the lid was removed, and the condition of the cured coating was visually observed and rated as follows. A rating of △ or higher was judged to be acceptable. ⊚: The cured coating film is free of peeling or blistering, and there is no abnormality on the surface of the cured coating film. ◯: There is no peeling or swelling in the cured coating film, but there are traces of penetration on the surface of the cured coating film. △: The cured coating film has some peeling or swelling. ×: The cured coating film exhibits significant peeling or blistering.

[0081] (2) Insulation reliability Following the above test specimen preparation process, a test specimen was prepared using comb electrodes (line width / space = 30μm / 30μm) instead of a two-layer FCCL substrate, and the insulation resistance was measured by applying DC32V using a HAST device after humidifying at 110℃ and 85% RH for 24 hours. The evaluation criteria are as follows, and a rating of △ or higher was judged to be a pass. ◎: Insulation resistance is 1.0×10 9 More than Ω. ○: Insulation resistance is 1.0×10 8 Ω or more 1.0×10 9 It is less than Ω. △: Insulation resistance is 1.0×10 7 Ω or more 1.0×10 8 It is less than Ω. ×: Insulation resistance is 1.0×10 7 It is less than Ω.

[0082] (3) Paint film hardness The pencil hardness of the cured coating on the copper foil of the two-layer FCCL substrate was evaluated according to the test method of JIS K-5600-5-4.

[0083] (4) Developability After development, the test specimens were visually inspected for the presence or absence of residues on the copper foil and polyimide film, and rated on the following three-level scale. A rating of △ or higher was deemed to be acceptable. ◯: No residue was found on either the copper foil or the polyimide film. △: No residue was found on the copper foil, but some residue was found on the polyimide film. ×: Residues were found on both the copper foil and the polyimide film.

[0084] (5) Tackiness In the test specimen preparation process, after preliminary drying at 80°C for 20 minutes, a negative film was placed on the coating and exposed to light. The adhesion was visually observed and rated on the following three-point scale. A rating of △ or higher was deemed to be a pass. ○: No sticking. △: Sticking marks remain on the coating. ×: After the negative film was peeled off, the coating film was found to be stuck to the negative film.

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

[0086] [Table 1]

[0087] As shown in Table 1 above, in Examples 1 to 19 in which an α-aminoalkylphenone-based photopolymerization initiator and an oxime ester-based photopolymerization initiator were blended as the photoradical polymerization initiator, and further a cationic polymerization initiator was blended, an insulating coating excellent in insulation reliability, coating hardness, developability, and tackiness, and further having excellent flux resistance, could be formed.

[0088] In particular, Example 1, which used a phosphorus-based photoradical polymerization initiator, showed improved coating hardness compared to Examples 5, 9, and 19, which used antimony-based photoradical polymerization initiators. Also, Examples 1 to 18, in which the cationic moiety of the cationic polymerization initiator is an aromatic compound having one or two aromatic rings in one molecule, showed well-balanced improvements in insulation reliability, coating hardness, developability, and tackiness, and further improved flux resistance, compared to Example 19, in which the cationic moiety is an aromatic compound having three aromatic rings.

[0089] Moreover, Examples 1 to 12, which contain two epoxy compounds selected from the group consisting of cresol novolac epoxy resin, bisphenol A epoxy resin, biphenyl aralkyl epoxy resin, and triglycidyl isocyanurate, have further improved tackiness compared to Examples 14 to 17, which contain one epoxy compound selected from the group consisting of cresol novolac epoxy resin, bisphenol A epoxy resin, biphenyl aralkyl epoxy resin, and triglycidyl isocyanurate. Moreover, Example 1, which contains cresol novolac epoxy resin and triglycidyl isocyanurate as epoxy compounds, has further improved flux resistance, insulation reliability, and coating hardness.

[0090] On the other hand, in Comparative Example 1 in which no cationic polymerization initiator was added, flux resistance could not be obtained. [Industrial Applicability]

[0091] INDUSTRIAL APPLICABILITY The photosensitive resin composition of the present invention is capable of forming an insulating coating having excellent flux resistance without impairing basic properties such as insulation reliability, coating hardness, developability, and tackiness, and is therefore highly useful in the field of insulating protective films provided on printed wiring boards using flexible or rigid substrates.

Claims

1. (A) a carboxyl group-containing photosensitive resin, (B) a cationic polymerization initiator, (C) a photoradical polymerization initiator, (D) an epoxy compound, and (E) a reactive diluent; the (C) photoradical polymerization initiator contains (C1) an α-aminoalkylphenone-based photopolymerization initiator and (C2) an oxime ester-based photopolymerization initiator, The cationic moiety of the cationic polymerization initiator (B) is an aromatic sulfonium. The photosensitive resin composition according to claim 1, wherein the epoxy compound (D) contains at least two kinds selected from the group consisting of cresol novolac type epoxy resins, bisphenol A type epoxy resins, biphenyl aralkyl type epoxy resins, and triglycidyl isocyanurate.

2. 2. The photosensitive resin composition according to claim 1, wherein the anion moiety of the cationic polymerization initiator (B) is a phosphorus-based or antimony-based anion moiety.

3. 2. The photosensitive resin composition according to claim 1, wherein the anion moiety of the cationic polymerization initiator (B) is a phosphorus-based anion moiety.

4. 4. The photosensitive resin composition according to claim 1, wherein the cationic moiety of the cationic polymerization initiator (B) is an aromatic compound having three or less aromatic rings in one molecule.

5. 4. The photosensitive resin composition according to claim 1, wherein the cationic moiety of the cationic polymerization initiator (B) is an aromatic compound having two or less aromatic rings in one molecule.

6. The photosensitive resin composition according to any one of claims 1 to 5, wherein the (C1) α-aminoalkylphenone-based photopolymerization initiator contains 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone.

7. 7. Any one of claims 1 to 6, wherein the oxime ester photopolymerization initiator (C2) contains (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime.

2. The photosensitive resin composition according to claim 1.

8. A photocured product of the photosensitive resin composition according to any one of claims 1 to 7.

9. A printed wiring board having a photocured film of the photosensitive resin composition according to any one of claims 1 to 7.

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