JP7503584B2 - Photosensitive resin composition, photocured product of photosensitive resin composition, and printed wiring board having photocured film of photosensitive resin composition - Google Patents

Description

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.

A conductor circuit pattern such as copper foil is formed on the substrate of a 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 coating as a protective film. This prevents solder from adhering to unnecessary areas when electronic components are soldered to the printed wiring board, and also prevents the circuit conductors from being directly exposed to air and corroding due to oxidation or humidity.

Conventionally, inorganic ion exchangers have been used in photosensitive resin compositions, which are insulating coating materials, to improve the insulating reliability of insulating films. As a photosensitive resin composition in which an inorganic ion exchanger is blended to improve the insulating reliability, a photosensitive resin composition containing (A) an acid-modified vinyl group-containing epoxy resin, (B) a photopolymerization initiator, (C) an inorganic ion exchanger having at least one selected from the group consisting of Zr, Bi, Mg, and Al, and (D) a photopolymerizable compound has been proposed (Patent Document 1).

On the other hand, in recent years, with technological advances, there has been an ever-increasing demand for smaller and lighter products in the electronics field, and as a result, there is a demand for finer pitches and finer conductor circuit patterns on printed wiring boards in order to arrange smaller electronic components at higher densities. Accordingly, there is a demand for insulating coatings with higher performance in terms of finer pitches, resolution, and other characteristics. Furthermore, in recent years, there has also been a demand for insulating coatings that have excellent insulation reliability, particularly in the thickness direction of the insulating coating, even when another conductive material such as a shielding film is brought into contact with the insulating coating of a printed wiring board.

However, in Patent Document 1, where an inorganic ion exchanger is merely blended to improve insulation reliability, there is still room for improvement in insulation reliability in fine-pitched insulation coatings. Also, in insulation coatings that are in contact with another electrically conductive material, there is still room for improvement in insulation reliability, particularly in the insulation reliability in the thickness direction of the insulation coating.

In addition, to make printed wiring boards more versatile, the surface of the insulating coating formed on the printed wiring board may be subjected to a surface treatment such as gold plating. However, when gold plating is performed on the surface of an insulating coating that has been developed with an alkaline solution, the hardening property of the insulating coating and its adhesion to the substrate may decrease.

JP 2022-16491 A

In view of the above circumstances, the present invention aims to provide a photosensitive resin composition that can produce a cured product with excellent insulation reliability and gold plating resistance without impairing the storage stability of the photosensitive resin composition.

（式（１）中におけるＲ^１、Ｒ^２、Ｒ^３、Ｒ^４は、それぞれ、独立して、Ｈまたはアルキル基を示す。）で表される化合物を含む感光性樹脂組成物。
［２］前記一般式（１）中におけるＲ^１、Ｒ^２、Ｒ^３、Ｒ^４は、それぞれ、独立して、Ｃ_ｎＨ_２ｎ＋１であり、ｎは１～１０の整数である［１］に記載の感光性樹脂組成物。
［３］前記（Ｃ）光反応安定化剤が、４，４’－ビス（ジメチルアミノ）ベンゾフェノン及び４，４’－ビス（ジエチルアミノ）ベンゾフェノンからなる群から選択されたベンゾフェノン誘導体の少なくとも１種を含む［１］または［２］に記載の感光性樹脂組成物。
［４］前記（Ｃ）光反応安定化剤が、前記（Ａ）感光性樹脂１００質量部に対して、０．１０質量部以上１０質量部以下含まれる［１］乃至［３］のいずれか１つに記載の感光性樹脂組成物。
［５］前記（Ｃ）光反応安定化剤が、前記（Ａ）感光性樹脂１００質量部に対して、０．５０質量部以上５．０質量部以下含まれる［１］乃至［３］のいずれか１つに記載の感光性樹脂組成物。
［６］前記（Ｃ）光反応安定化剤が、前記（Ｂ）α－アミノアルキルフェノン系光重合開始剤１００質量部に対して、１５質量部以上２００質量部以下含まれる［１］乃至［５］のいずれか１つに記載の感光性樹脂組成物。
［７］前記（Ｅ）無機イオン交換体が、ジルコニア化合物、アルミニウム化合物とジルコニア化合物の混合物、ビスマス化合物、及びビスマス化合物とジルコニア化合物の混合物からなる群から選択された少なくとも１種を含む［１］乃至［６］のいずれか１つに記載の感光性樹脂組成物。
［８］前記（Ｅ）無機イオン交換体が、アルミニウム化合物とジルコニア化合物の混合物を含む［１］乃至［６］のいずれか１つに記載の感光性樹脂組成物。
［９］前記（Ｅ）無機イオン交換体が、前記（Ａ）感光性樹脂１００質量部に対して、３．０質量部以上３０質量部以下含まれる［１］乃至［８］のいずれか１つに記載の感光性樹脂組成物。
［１０］前記（Ｂ）α－アミノアルキルフェノン系光重合開始剤が、１－(４－モルホリノフェニル)－２－(ジメチルアミノ)－２－(４－メチルベンジル）－１－ブタノンを含む［１］乃至［９］のいずれか１つに記載の感光性樹脂組成物。
［１１］前記（Ｂ）α－アミノアルキルフェノン系光重合開始剤が、前記（Ａ）感光性樹脂１００質量部に対して、０．５０質量部以上１０質量部以下含まれる［１］乃至［１０］のいずれか１つに記載の感光性樹脂組成物。
［１２］さらに、オキシムエステル系光重合開始剤を含む［１］乃至［１１］のいずれか１つに記載の感光性樹脂組成物。
［１３］前記オキシムエステル系光重合開始剤が、（９－エチル－６－ニトロ－９Ｈ－カルバゾール－３－イル）（４－（（１－メトキシプロパン－２－イル）オキシ）－２－メチルフェニル）メタノン Ｏ－アセチルオキシムを含む［１２］に記載の感光性樹脂組成物。
［１４］［１］乃至［１３］のいずれか１つに記載の感光性樹脂組成物の光硬化物。
［１５］［１］乃至［１３］のいずれか１つに記載の感光性樹脂組成物の光硬化膜を有するプリント配線板。 The gist of the configuration of the present invention is as follows.
[1] A composition comprising: (A) a photosensitive resin; (B) an α-aminoalkylphenone-based photopolymerization initiator; (C) a photoreaction stabilizer; (D) an epoxy compound; (E) an inorganic ion exchanger; (F) a reactive diluent; and (G) a colorant;
The (C) photoreaction stabilizer is represented by the following general formula (1):

A photosensitive resin composition comprising a compound represented by formula (1): (in which R ¹ , R ² , R ³ and R ⁴ each independently represent H or an alkyl group).
[2] The photosensitive resin composition according to [1], wherein R ¹ , R ² , R ³ , and R ⁴ in the general formula (1) are each independently C _n H _2n+1 , where n is an integer of 1 to 10.
[3] The photosensitive resin composition according to [1] or [2], wherein the (C) photoreaction stabilizer contains at least one benzophenone derivative selected from the group consisting of 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone.
[4] The photosensitive resin composition according to any one of [1] to [3], wherein the (C) photoreaction stabilizer is contained in an amount of 0.10 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the (A) photosensitive resin.
[5] The photosensitive resin composition according to any one of [1] to [3], wherein the (C) photoreaction stabilizer is contained in an amount of 0.50 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the (A) photosensitive resin.
[6] The photosensitive resin composition according to any one of [1] to [5], wherein the (C) photoreaction stabilizer is contained in an amount of 15 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the (B) α-aminoalkylphenone-based photopolymerization initiator.
[7] The photosensitive resin composition according to any one of [1] to [6], wherein the (E) inorganic ion exchanger contains at least one selected from the group consisting of a zirconia compound, a mixture of an aluminum compound and a zirconia compound, a bismuth compound, and a mixture of a bismuth compound and a zirconia compound.
[8] The photosensitive resin composition according to any one of [1] to [6], wherein the inorganic ion exchanger (E) contains a mixture of an aluminum compound and a zirconia compound.
[9] The photosensitive resin composition according to any one of [1] to [8], wherein the (E) inorganic ion exchanger is contained in an amount of 3.0 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the (A) photosensitive resin.
[10] The photosensitive resin composition according to any one of [1] to [9], wherein the (B) α-aminoalkylphenone-based photopolymerization initiator contains 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone.
[11] The photosensitive resin composition according to any one of [1] to [10], wherein the (B) α-aminoalkylphenone-based photopolymerization initiator is contained in an amount of 0.50 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the (A) photosensitive resin.
[12] The photosensitive resin composition according to any one of [1] to [11], further comprising an oxime ester-based photopolymerization initiator.
[13] The photosensitive resin composition according to [12], wherein the oxime ester photopolymerization initiator contains (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime.
[14] A photocured product of the photosensitive resin composition according to any one of [1] to [13].
[15] A printed wiring board having a photocured film of the photosensitive resin composition according to any one of [1] to [13].

According to an embodiment of the photosensitive resin composition of the present invention, by containing (B) an α-aminoalkylphenone-based photopolymerization initiator, (C) a photoreaction stabilizer represented by the above general formula (1), and (E) an inorganic ion exchanger, a cured product having excellent insulation reliability and gold plating resistance can be obtained without impairing the storage stability of the photosensitive resin composition. In this way, the photosensitive resin composition of the present invention can provide excellent insulation reliability, and therefore, even in the case of a fine-pitched insulating coating or an insulating coating in contact with another material having electrical conductivity, excellent insulation reliability can be obtained, including insulation reliability in the thickness direction of the insulating coating.

According to an embodiment of the photosensitive resin composition of the present invention, R ¹ , R ² , R ³ , and R ⁴ in the above general formula (1) are each independently C _n H _2n+1 , where n is an integer from 1 to 10, so that a cured product having excellent insulation reliability and gold plating resistance can be more reliably obtained.

According to an embodiment of the photosensitive resin composition of the present invention, the (C) photoreaction stabilizer contains at least one benzophenone derivative selected from the group consisting of 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone, which makes it possible to more reliably obtain excellent insulation reliability and gold plating resistance.

According to an embodiment of the photosensitive resin composition of the present invention, the (C) photoreaction stabilizer is contained in an amount of 0.10 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the (A) photosensitive resin, thereby ensuring excellent insulation reliability.

According to an embodiment of the photosensitive resin composition of the present invention, the (C) photoreaction stabilizer is contained in an amount of 15 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the (B) α-aminoalkylphenone-based photopolymerization initiator, so that excellent insulation reliability and gold plating resistance can be obtained more reliably.

According to an embodiment of the photosensitive resin composition of the present invention, the inorganic ion exchanger (E) contains at least one selected from the group consisting of a zirconia compound, a mixture of an aluminum compound and a zirconia compound, a bismuth compound, and a mixture of a bismuth compound and a zirconia compound, thereby making it possible to more reliably obtain excellent insulation reliability and gold plating resistance.

According to an embodiment of the photosensitive resin composition of the present invention, the (E) inorganic ion exchanger contains a mixture of an aluminum compound and a zirconia compound, which further improves the insulation reliability.

According to an embodiment of the photosensitive resin composition of the present invention, the (E) inorganic ion exchanger is contained in an amount of 3.0 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the (A) photosensitive resin, so that excellent insulation reliability and gold plating resistance can be obtained more reliably.

According to an embodiment of the photosensitive resin composition of the present invention, the (B) α-aminoalkylphenone-based photopolymerization initiator contains 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone, which further improves the storage stability of the photosensitive resin composition.

（式（１）中におけるＲ^１、Ｒ^２、Ｒ^３、Ｒ^４は、それぞれ、独立して、Ｈまたはアルキル基を示す。）で表される化合物を含む。本発明の感光性樹脂組成物では、感光性樹脂組成物の貯蔵安定性を損なうことなく、優れた絶縁信頼性と耐金めっき性を有する硬化物を得ることができる。このように、本発明の感光性樹脂組成物では、優れた絶縁信頼性が得られるので、ファインピッチ化された絶縁被膜、導電性を有する別材料を接触させた絶縁被膜であっても、絶縁被膜の厚さ方向の絶縁信頼性を含めて優れた絶縁信頼性を得ることができる。 Next, the photosensitive resin composition of the present invention will be described below. The photosensitive resin composition of the present invention contains (A) a photosensitive resin, (B) an α-aminoalkylphenone-based photopolymerization initiator, (C) a photoreaction stabilizer, (D) an epoxy compound, (E) an inorganic ion exchanger, (F) a reactive diluent, and (G) a colorant, and the (C) photoreaction stabilizer is represented by the following general formula (1):

(In formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent H or an alkyl group.) With the photosensitive resin composition of the present invention, a cured product having excellent insulation reliability and gold plating resistance can be obtained without impairing the storage stability of the photosensitive resin composition. In this way, with the photosensitive resin composition of the present invention, excellent insulation reliability can be obtained, including insulation reliability in the thickness direction of the insulating coating, even in the case of an insulating coating with a fine pitch or an insulating coating in contact with another material having electrical conductivity.

<(A) Photosensitive resin>
The photosensitive resin, which is the component (A), is the base resin of the photosensitive resin composition. The structure of the photosensitive resin, which is the component (A), is not particularly limited, and may be, for example, a carboxyl group-containing photosensitive resin. The carboxyl group-containing photosensitive resin may be a resin having one or more photosensitive unsaturated double bonds and a free carboxyl group. The carboxyl group-containing photosensitive resin may be, for example, a polybasic acid-modified unsaturated monocarboxylated epoxy 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 radical polymerizable unsaturated monocarboxylic acid to obtain an unsaturated monocarboxylated epoxy resin, and reacting the resulting hydroxyl group with a polybasic acid and/or a polybasic acid anhydride.

Polyfunctional epoxy resin The epoxy equivalent of the polyfunctional 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 polyfunctional 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 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 A 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.

Radically polymerizable unsaturated monocarboxylic acid Examples of radically polymerizable unsaturated monocarboxylic acids include acrylic acid, methacrylic acid (hereinafter, acrylic acid and/or methacrylic acid may be referred to as "(meth)acrylic acid"), crotonic acid, tiglic acid, angelic acid, and cinnamic acid. Of these, (meth)acrylic acid is preferred because of its ease of handling. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

Polybasic acid and/or polybasic acid anhydride 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, trimellitic acid, pyromellitic acid, diglycolic acid, and the like. Examples of polybasic acid anhydrides include the anhydrides of the above-mentioned polybasic acids. These polybasic acids and polybasic acid anhydrides may be used alone or in combination of two or more.

Polybasic acid-modified unsaturated monocarboxylated epoxy resins can also be used as carboxyl group-containing photosensitive resins, but polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resins having a chemical structure obtained by adding a compound having one or more radically polymerizable unsaturated groups and an epoxy group to a portion of the carboxyl groups of the polybasic acid-modified unsaturated monocarboxylated epoxy resins may also be used, which further introduce radically polymerizable unsaturated groups. The polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resins having further introduced radically polymerizable unsaturated groups have a chemical structure in which a radically polymerizable unsaturated group is further introduced into the side chain of the polybasic acid-modified unsaturated monocarboxylated epoxy resin, and therefore have properties with improved photosensitivity compared to polybasic acid-modified unsaturated monocarboxylated epoxy resins.

An example of a compound having one or more radically polymerizable unsaturated groups and an epoxy group is a glycidyl compound. Examples of glycidyl compounds include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, pentaerythritol triacrylate monoglycidyl ether, and pentaerythritol trimethacrylate monoglycidyl ether. A glycidyl compound may have one or more glycidyl groups in one molecule. The above-mentioned compounds having one or more radically polymerizable unsaturated groups and an epoxy group may be used alone or in combination of two or more kinds.

As the carboxyl group-containing photosensitive resin, for example, a polybasic acid-modified unsaturated monocarboxylated epoxy resin having a long-chain hydrocarbon structure may be used, which has a chemical structure obtained by adding a polybasic acid and/or a polybasic acid anhydride to an unsaturated carboxylated epoxy resin, which is a reaction product of a multifunctional epoxy resin having two or more epoxy groups in one molecule, at least one linear or branched aliphatic carboxylic acid having 8 or more carbon atoms per carboxyl group, and a radically polymerizable unsaturated monocarboxylic acid.

The above-mentioned polyfunctional epoxy resins can be cited as examples of polyfunctional epoxy resins that are polybasic acid-modified unsaturated monocarboxylated epoxy resins having a long-chain hydrocarbon structure.

A linear or branched aliphatic carboxylic acid having 8 or more carbon atoms per carboxyl group reacts with the epoxy group of a multifunctional epoxy resin, thereby introducing a long-chain hydrocarbon structure derived from the aliphatic carboxylic acid into the multifunctional epoxy resin. By introducing a long-chain hydrocarbon structure derived from the aliphatic carboxylic acid into the multifunctional epoxy resin, excellent foldability can be further imparted to the cured product of the photosensitive resin composition containing the photosensitive resin. The linear or branched aliphatic carboxylic acid having 8 or more carbon atoms per carboxyl group is not particularly limited, and either saturated or unsaturated can be used. Examples of the aliphatic carboxylic acid include monobasic acids having 8 or more carbon atoms and dibasic acids having 16 or more carbon atoms. From the viewpoint of obtaining foldability and dryness to the touch, the monobasic acid and dibasic acid are preferably linear or branched having 2 or less side chains with 2 or less carbon atoms.

The linear or branched aliphatic carboxylic acid having 8 or more carbon atoms per carboxyl group is not particularly limited, and examples of monobasic acids include caprylic acid (C8), capric acid (decanoic acid: C10), undecylic acid (C11), lauric acid (dodecanoic acid: C12), tridecylic acid (C13), myristic acid (C14), pentadecylic acid (C15), palmitic acid (hexadecanoic acid: C16), margaric acid (heptadecanoic acid: C17), stearic acid (C18), tuberculinostearic acid (C19), arachidic acid (C20), behenic acid (C22), tricosylic acid (C23), tetracosanoic acid (C24), hexacosanoic acid (C26), octacosanoic acid (C28), and triacontanoic acid (C30).

Examples of dibasic acids include C36 dimer acids obtained by dimerization of unsaturated fatty acids such as hexadecanedioic acid (C16), eicosane diacid (C20), ethyloctadecanedioic acid (C20), eicosadienedioic acid (C20), vinyloctadecanedioic acid (C20), dimethyleicosadienedioic acid (C22), dimethyleicosane diacid (C22), diphenylhexadecanedioic acid (C28), and oleic acid (C18). The linear or branched aliphatic carboxylic acids having 8 or more carbon atoms per carboxyl group may be used alone or in combination of two or more. If necessary, a linear or branched aliphatic carboxylic acid having 8 or more carbon atoms per carboxyl group may be used in combination with a linear or branched aliphatic carboxylic acid having 7 or less carbon atoms per carboxyl group.

The proportion (feeding proportion) of linear or branched aliphatic carboxylic acid having 8 or more carbon atoms per carboxyl group in the carboxyl group-containing photosensitive resin is not particularly limited, but the lower limit is preferably 15% by mass, and particularly preferably 18% by mass, from the viewpoint of further improving the bending property while adjusting the amount of polybasic acid and/or polybasic acid anhydride introduced to adjust the solid acid value. On the other hand, the upper limit of the proportion of linear or branched aliphatic carboxylic acid having 8 or more carbon atoms per carboxyl group is preferably 25% by mass, and particularly preferably 20% by mass, from the viewpoint of adjusting the amount of polybasic acid and/or polybasic acid anhydride introduced to adjust the solid acid value while maintaining the amount of radically polymerizable unsaturated monocarboxylic acid introduced (i.e., photosensitivity).

The radically polymerizable unsaturated monocarboxylic acid of the polybasic acid-modified unsaturated monocarboxylated epoxy resin having a long-chain hydrocarbon structure can be exemplified by the radically polymerizable unsaturated monocarboxylic acid described above. The ratio (feed ratio) of the radically polymerizable unsaturated monocarboxylic acid is not particularly limited, but the lower limit is preferably 2.0% by mass, and more preferably 3.0% by mass, from the viewpoint of adjusting the amount of polybasic acid and/or polybasic acid anhydride introduced and the solid acid value while reliably obtaining sensitivity. On the other hand, the upper limit of the ratio of the radically polymerizable unsaturated monocarboxylic acid is preferably 10% by mass, and more preferably 5.0% by mass, from the viewpoint of adjusting the amount of polybasic acid and/or polybasic acid anhydride introduced while maintaining the amount of linear or branched aliphatic carboxylic acid introduced having 8 or more carbon atoms per carboxyl group and adjusting the solid acid value.

The polybasic acid and/or polybasic acid anhydride of the polybasic acid-modified unsaturated monocarboxylated epoxy resin having a long-chain hydrocarbon structure can be the polybasic acid and/or polybasic acid anhydride described above. The proportion (feeding proportion) of the polybasic acid and/or polybasic acid anhydride in the carboxyl group-containing photosensitive resin is not particularly limited, but the lower limit is preferably 7.0% by mass, and more preferably 9.0% by mass, from the viewpoint of good alkaline developability and adjustment of the solid acid value. On the other hand, the upper limit of the proportion of the polybasic acid and/or polybasic acid anhydride is preferably 16% by mass, and more preferably 14% by mass, from the viewpoint of more reliably maintaining excellent insulation reliability and adjusting the solid acid value.

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. On the other hand, the upper limit of the acid value of the carboxyl group-containing photosensitive resin is preferably 200 mgKOH/g from the viewpoint of preventing dissolution of the exposed portion (photocured portion) by the alkaline developer, and particularly preferably 150 mgKOH/g from the viewpoint of reliably improving the insulation reliability of the photocured product.

The mass average molecular weight of the 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 6,000, more preferably 7,000, and particularly preferably 8,000, in order to reliably improve the toughness and dryness to the touch of the photocured product. On the other hand, the upper limit of the mass average molecular weight of the photosensitive resin is preferably 200,000, more preferably 100,000, and particularly preferably 50,000. The above "mass average molecular weight" refers to the mass average molecular weight measured at room temperature using gel permeation chromatography (GPC) and calculated in terms of polystyrene.

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

<(B) α-Aminoalkylphenone-based photopolymerization initiator>
The inclusion of an α-aminoalkylphenone-based photopolymerization initiator, which is component (B), as a photopolymerization initiator, in combination with a photoreaction stabilizer (C) represented by the following general formula (1) and an inorganic ion exchanger (E), which will be described later, contributes to obtaining a cured product having excellent insulation reliability and gold plating resistance without impairing storage stability.

（式（２）中におけるＲは、水素または炭素数１～５個のアルキル基を表す。）で表される化合物を挙げることができる。このうち、貯蔵安定性を損なうことなく、優れた絶縁信頼性と耐金めっき性を有する硬化物を得ることに確実に寄与する点から、１－(４－モルホリノフェニル)－２－(ジメチルアミノ)－２－ベンジル－１－ブタノン（式（２）中におけるＲが水素）、１－(４－モルホリノフェニル)－２－(ジメチルアミノ)－２－(４－メチルベンジル）－１－ブタノン（式（２）中におけるＲがメチル基）が好ましく、感光性樹脂組成物の貯蔵安定性がさらに向上する点から、１－(４－モルホリノフェニル)－２－(ジメチルアミノ)－２－(４－メチルベンジル）－１－ブタノンが特に好ましい。 Examples of the α-aminoalkylphenone-based photopolymerization initiator include those represented by the following general formula (2):

(In formula (2), R represents hydrogen or an alkyl group having 1 to 5 carbon atoms.) Among these, 1-(4-morpholinophenyl)-2-(dimethylamino)-2-benzyl-1-butanone (R in formula (2) is hydrogen) and 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone (R in formula (2) is methyl) are preferred from the viewpoint of reliably contributing to obtaining a cured product having excellent insulation reliability and gold plating resistance without impairing storage stability, and 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone is particularly preferred from the viewpoint of further improving the storage stability of the photosensitive resin composition.

The amount of the α-aminoalkylphenone photopolymerization 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, per 100 parts by mass of photosensitive resin (solid content; the same applies below), in order to ensure that the cured product has excellent insulation reliability and gold plating resistance. On the other hand, the upper limit of the amount of the α-aminoalkylphenone photopolymerization initiator is preferably 10 parts by mass, more preferably 7.0 parts by mass, and particularly preferably 5.0 parts by mass, in order to ensure that the cured coating film of the photosensitive resin composition has excellent heat resistance, per 100 parts by mass of photosensitive resin.

（式（１）中におけるＲ^１、Ｒ^２、Ｒ^３、Ｒ^４は、それぞれ、独立して、Ｈまたはアルキル基を示す。）で表されるベンゾフェノン誘導体を含む。上記ベンゾフェノン誘導体は、（Ｂ）α－アミノアルキルフェノン系光重合開始剤及び（Ｅ）無機イオン交換体とあいまって、貯蔵安定性を損なうことなく、優れた絶縁信頼性と耐金めっき性を有する硬化物を得ることに寄与する。（Ｃ）成分である光反応安定化剤は、（Ｂ）α－アミノアルキルフェノン系光重合開始剤及び（Ｅ）無機イオン交換体とあいまって、優れた絶縁信頼性を有する硬化物を得ることができるので、ファインピッチ化された絶縁被膜、導電性を有する別材料を接触させた絶縁被膜であっても、絶縁被膜の厚さ方向の絶縁信頼性を含めて優れた絶縁信頼性を得ることに寄与する。 <(C) Photoreaction stabilizer>
In the present invention, the photoreaction stabilizer (C) is represented by the following general formula (1):

(In formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent H or an alkyl group.) The benzophenone derivative, in combination with (B) an α-aminoalkylphenone-based photopolymerization initiator and (E) an inorganic ion exchanger, contributes to obtaining a cured product having excellent insulation reliability and gold plating resistance without impairing storage stability. The light reaction stabilizer, which is component (C), in combination with (B) an α-aminoalkylphenone-based photopolymerization initiator and (E) an inorganic ion exchanger, can obtain a cured product having excellent insulation reliability, and therefore contributes to obtaining excellent insulation reliability, including insulation reliability in the thickness direction of the insulating coating, even in the case of a fine-pitched insulating coating or an insulating coating in contact with another material having electrical conductivity.

Examples of the light reaction stabilizer of the component (C) include at least one benzophenone derivative selected from the group consisting of diaminobenzophenone and bis(dialkylamino)benzophenone. The number of carbon atoms in the alkyl group of the bis(dialkylamino)benzophenone is not particularly limited, but from the viewpoint of more reliably obtaining a cured product having excellent insulation reliability and gold plating resistance, a benzophenone derivative having an alkyl group having 1 to 10 carbon atoms (i.e., R ¹ , R ² , R ³ , and R ⁴ in general formula (1) are each independently C _n H _2n+1 , n is an integer of 1 to 10) is preferred, a benzophenone derivative having an alkyl group having 1 to 5 carbon atoms (R ¹ , R ² , R ³ , and R ⁴ in general formula (1) are each independently C _n H _2n+1 , n is an integer of 1 to 5) is more preferred, and a benzophenone derivative having an alkyl group having 1 to 3 carbon atoms (R ¹ , R ² , R ³ , and R ⁴ in general formula (1) are each independently C _n H _2n+1 , n is an integer of 1 to 3) is particularly preferred. These benzophenone derivatives may be used alone or in combination of two or more kinds.

Of these, the photoreaction stabilizer of component (C) preferably contains at least one benzophenone derivative selected from the group consisting of 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone, since this allows for more reliable achievement of excellent insulation reliability and gold plating resistance.

The amount of the photoreaction stabilizer (C) is not particularly limited, but the lower limit is preferably 0.10 parts by mass, more preferably 0.30 parts by mass, and even more preferably 0.50 parts by mass, per 100 parts by mass of photosensitive resin, from the viewpoint of reliably obtaining excellent insulation reliability, and 1.0 part by mass is particularly preferred from the viewpoint of further improving insulation reliability. On the other hand, the upper limit of the amount of the photoreaction stabilizer (C) is preferably 10 parts by mass, more preferably 5.0 parts by mass, and especially preferred from the viewpoint of reliably obtaining excellent resolution.

The blending ratio of the photoreaction stabilizer (C) and the α-aminoalkylphenone photopolymerization initiator (B) is not particularly limited, but in order to more reliably obtain excellent insulation reliability and gold plating resistance, it is preferable that the photoreaction stabilizer (C) is contained in a range of 15 parts by mass to 200 parts by mass, and particularly preferable that it is contained in a range of 20 parts by mass to 150 parts by mass, per 100 parts by mass of the α-aminoalkylphenone photopolymerization initiator (B).

<(D) Epoxy Compound>
The epoxy compound, which is the component (D), is intended to increase the crosslink density of the photocured product of the photosensitive resin composition and impart sufficient strength to the photocured product. Examples of the epoxy compound include epoxy resins. Examples of the epoxy resin include the same epoxy resins as the polyfunctional epoxy resins used in the preparation of the carboxyl group-containing photosensitive resin described above. Specific examples include 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 A 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, and the like. These may be used alone or in combination of two or more.

The amount of epoxy compound is not particularly limited, but in order to obtain a coating film with sufficient strength after photocuring of the photosensitive resin composition, it is preferably from 10 to 100 parts by weight, and more preferably from 20 to 70 parts by weight, per 100 parts by weight of the photosensitive resin.

<(E) Inorganic ion exchanger>
The inorganic ion exchanger of component (E) is an ion trapping agent, which, in combination with the α-aminoalkylphenone photopolymerization initiator (B) and the light reaction stabilizer (C), contributes to obtaining a cured product having excellent insulation reliability and gold plating resistance without impairing storage stability. The inorganic ion exchanger of component (E), in combination with the α-aminoalkylphenone photopolymerization initiator (B) and the light reaction stabilizer (C), can obtain a cured product having excellent insulation reliability, and therefore contributes to obtaining excellent insulation reliability, including insulation reliability in the thickness direction of the insulating coating, even in the case of a fine-pitched insulating coating or an insulating coating in contact with another conductive material.

The inorganic ion exchanger may be at least one selected from the group consisting of cation exchangers (cation exchange type), anion exchangers (anion exchange type), and amphoteric ion exchangers (amphoteric ion exchange type).

The inorganic ion exchanger captures and fixes ionic impurities such as sodium ions and chloride ions remaining in the photosensitive resin composition of the present invention by taking in ions of the opposite charge and performing ion exchange, and also captures and fixes metal ions that become ions and move when a voltage is applied. The inorganic ion exchanger captures and fixes ionic impurities and metal ions, thereby contributing to improved insulation reliability. In addition, after the photosensitive resin composition is applied to a substrate, when the coating of the photosensitive resin composition is developed with an alkaline solution such as sodium carbonate, the carboxyl group (-COOH) of the photosensitive resin, which is the base resin, becomes a sodium salt (-COONa). On the other hand, it is thought that the inorganic ion exchanger captures the sodium ions applied to the coating of the photosensitive resin composition in the development process, thereby suppressing the carboxyl group (-COOH) from becoming a sodium salt (-COONa). By preventing the carboxyl group (-COOH) from becoming a sodium salt (-COONa), it is possible to prevent the adhesion of the coating of the photosensitive resin composition to the substrate from decreasing after gold plating, which is believed to contribute to obtaining excellent gold plating resistance. Furthermore, it is also believed that the inorganic ion exchanger is oriented at the cross section of the opening of the coating of the photosensitive resin composition, thereby capturing sodium ions and potassium ions in the gold plating solution that cause the coating to corrode during gold plating, thereby contributing to improved gold plating resistance.

Examples of inorganic ion exchangers include Zr (zirconium), Sb (antimony), Bi (bismuth), Zr-Al (zirconium-aluminum), Sb-Bi (antimony-bismuth), Mg-Al (magnesium-aluminum), Zr-Bi (zirconium-bismuth), and Zr-Mg-Al (zirconium-magnesium-aluminum). Among these, zirconia compounds, mixtures of aluminum compounds and zirconia compounds, bismuth compounds, and mixtures of bismuth compounds and zirconia compounds are preferred because they can more reliably obtain excellent insulation reliability and gold plating resistance, and mixtures of aluminum compounds and zirconia compounds are particularly preferred because they further improve insulation reliability. These inorganic ion exchangers may be used alone or in combination of two or more types.

Examples of inorganic ion exchangers include cation exchangers such as "IXE-100" and "IXE-300" manufactured by Toagosei Co., Ltd., anion exchangers such as "IXE-550" manufactured by Toagosei Co., Ltd., and both ion exchangers such as "IXE-600", "IXE-633", "IXE-6107", "IXE-6136", "IXEPLAS-A1", "IXEPLAS-A2", and "IXEPLAS-B1" manufactured by Toagosei Co., Ltd. These inorganic ion exchangers may be used alone or in combination of two or more kinds.

The amount of inorganic ion exchanger is not particularly limited, but the lower limit is preferably 3.0 parts by mass, more preferably 5.0 parts by mass, and particularly preferably 7.0 parts by mass, per 100 parts by mass of photosensitive resin, in order to more reliably obtain excellent insulation reliability and gold plating resistance. On the other hand, the upper limit of the amount of inorganic ion exchanger is preferably 30 parts by mass, in order to reliably obtain excellent coating hardness and excellent gold plating resistance, and more preferably 20 parts by mass, and particularly preferably 15 parts by mass, in order to reliably improve adhesion with the base material and reliably obtain excellent gold plating resistance.

<(F) 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 imparting sufficient heat resistance, acid resistance, alkali resistance, etc. to the cured coating film of the photosensitive resin composition.

Examples of reactive diluents include (meth)acrylate compound monomers such as monofunctional acrylate and/or methacrylate (acrylate and/or methacrylate are sometimes referred to as "(meth)acrylate") compounds, difunctional (meth)acrylate compounds, trifunctional (meth)acrylate compounds, and tetrafunctional or higher (meth)acrylate compounds. Examples of the (meth)acrylate 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 acrylates 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.

The amount of reactive diluent is not particularly limited, but is preferably 5.0 parts by weight or more and 80 parts by weight or less, and particularly preferably 10 parts by weight or more and 40 parts by weight or less, per 100 parts by weight of photosensitive resin.

<(G) Colorant>
The colorant is blended to impart a desired color to the photocured product of the photosensitive resin composition of the present invention. The colorant can impart a hiding power to the photocured product of the photosensitive resin composition of the present invention. The colorant is not particularly limited to pigments, dyes, etc., and any colorant can be used depending on the desired color, such as white colorant, black colorant, blue colorant, green colorant, yellow colorant, purple colorant, orange colorant, red colorant, etc. Examples of the colorant include inorganic colorants such as titanium dioxide as a white colorant, acetylene black as a black colorant, carbon black as a black colorant, phthalocyanine-based colorants such as phthalocyanine green as a green colorant, phthalocyanine blue as a blue colorant, and diketopyrrolopyrrole-based colorants such as chromophthalic orange as an orange colorant. These colorants may be used alone or in combination of two or more.

The amount of colorant to be added is not particularly limited, but is preferably 0.5 parts by weight or more and 30 parts by weight or less, and particularly preferably 2.0 parts by weight or more and 10 parts by weight or less, per 100 parts by weight of photosensitive resin.

<Optional ingredients>
In addition to the above-mentioned components (A) to (G), the photosensitive resin composition of the present invention may further contain, as an optional component, a photopolymerization initiator other than the α-aminoalkylphenone-based photopolymerization initiator, if necessary. Examples of the other photopolymerization initiator include an oxime ester-based photopolymerization initiator. The oxime ester-based photopolymerization initiator contributes to improving the photosensitivity of the photosensitive resin composition.

Examples of oxime ester photopolymerization initiators 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- Examples include 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), (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime, etc.

Other photopolymerization initiators include photopolymerization initiators other than oxime ester photopolymerization initiators. Examples of other photopolymerization initiators include 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-tertiary butylanthraquinone, and 2-aminoanthraquinone; 2-methylthioxanthone, 2-ethylthioxanthone, and 2-chlorothioxanthone; Examples of the photopolymerization initiator include thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and the like; 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, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, and the like. These other photopolymerization initiators may be used alone or in combination of two or more.

The amount of the other photopolymerization initiator is not particularly limited, but is preferably 0.10 parts by weight or more and 5.0 parts by weight or less, and particularly preferably 0.20 parts by weight or more and 2.0 parts by weight or less, per 100 parts by weight of the photosensitive resin.

The photosensitive resin composition of the present invention can further contain other optional components, such as fillers, curing accelerators, additives, non-reactive diluents, flame retardants, etc., as necessary.

The strength of the photocured product of the photosensitive resin composition can be improved by adding a filler. Examples of fillers include inorganic fillers such as talc, barium sulfate, silica, alumina, aluminum hydroxide, aluminum phosphinate, and mica, and organic fillers such as urethane beads.

Examples of curing accelerators include 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), polyamines, etc. Examples of additives include antifoaming agents such as silicone polymers, hydrocarbon polymers, and acrylic polymers.

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 the components 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, aliphatic 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 ethyl diglycol acetate. These organic solvents may be used alone or in combination of two or more.

The flame retardant is used to impart flame retardancy to the photocured product of the photosensitive resin composition. Examples of flame retardants include phosphorus-containing flame retardants such as organic phosphates.

<Method for producing photosensitive resin composition>
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 mixing 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, 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 treatment, pre-kneading or pre-mixing may be carried out as necessary.

<Method of using the photosensitive resin composition>
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 protective film (e.g., a solder resist film or the like) by applying the photosensitive resin composition of the present invention to a printed wiring board will be described.

The photosensitive resin composition of the present invention obtained as described above is applied to a desired thickness on a printed wiring board having a circuit pattern formed by etching a copper foil, for example, by 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, when a non-reactive diluent is blended in the photosensitive resin composition, a tack-free coating film is formed by pre-drying at a temperature of about 60 to 100°C for about 10 to 50 minutes in order to volatilize the non-reactive diluent in the photosensitive resin composition. Next, an exposure process is performed in which active energy rays (for example, laser light) are directly irradiated onto the photosensitive resin composition in a desired pattern using a direct imaging device, and the coating film is photocured in the pattern. The exposure amount can be, for example, 50 mJ/cm ² to 2000 mJ/cm ^2. Next, the coating film is developed by removing the non-exposed area with a dilute alkaline aqueous solution. Examples of the developing method include a spray method and a shower method, and examples of the dilute alkaline aqueous solution include a 0.5 to 5 mass % aqueous sodium carbonate solution. Next, the developed coating film is post-cured (thermal curing treatment) for 20 to 80 minutes in a hot air circulation dryer at 130 to 170°C, whereby a photocured film (photocured product) having a desired pattern can be formed on the printed wiring board. Examples of the substrate for the printed wiring board include a flexible substrate and a rigid substrate.

In addition, instead of the exposure process in which active energy rays are directly irradiated according to a desired pattern using the direct imaging device described above, an exposure process may be performed in which a negative film (photomask) having a pattern in which the circuit pattern lands are made translucent is attached to the coating film that has been pre-dried and made tack-free, and active energy rays (e.g., ultraviolet rays with a wavelength of 300 to 400 nm) are irradiated from above to photocure the coating film.

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 deviate from the spirit of the invention.

Examples 1 to 8, Comparative Examples 1 to 2
The components shown in Table 1 below were blended 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 8 and Comparative Examples 1 and 2. The prepared photosensitive resin compositions were then applied to substrates as described below to prepare test specimens. The blending amount of each component shown in Table 1 below is shown in parts by mass unless otherwise specified. Note that blank spaces in the blending amounts in Table 1 below mean that no blending was performed.

Details of each component in Table 1 below are as follows.
(A) Photosensitive resin ZFR-1887: polybasic acid modified unsaturated monocarboxylated epoxy resin, solid content (resin content) 65% by mass, diethylene glycol monoethyl ether acetate 35% by mass, Nippon Kayaku Co., Ltd.

(B) α-Aminoalkylphenone-based photopolymerization initiator: Omnirad 379: IGM Resins B.V.; Omnirad 369: IGM Resins B.V.

(C) Photoreaction stabilizer Chivacure EMK: 4,4'-bis(diethylamino)benzophenone, Chitec

(D) Epoxy compound EPICLON 860: DIC Corporation

(E) Inorganic ion exchanger IXE-100: Zr-based cation exchanger, Toagosei Co., Ltd. IXEPLAS-A1: Zr-Al-based amphoteric ion exchanger, Toagosei Co., Ltd. IXEPLAS-A2: Zr-Al-based amphoteric ion exchanger, Toagosei Co., Ltd. IXE-550: Bi-based anion exchanger, Toagosei Co., Ltd. IXEPLAS-B1: Zr-Bi-based amphoteric ion exchanger, Toagosei Co., Ltd.

(F) Reactive diluent DPCA-120: Nippon Kayaku Co., Ltd.

(G) Coloring agent: Denka Black: Denki Kagaku Kogyo Co., Ltd.; LIONOL BLUE FG-7351: Toyo Color Co., Ltd.

Other photopolymerization initiators: (9-ethyl-6-nitro-9H-carbazol-3-yl) (4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime

Filler: RHC-730: Dainichiseika Chemicals Co., Ltd.; OP935: Clariant Japan Co., Ltd. Curing accelerator: DICY-7: Mitsubishi Chemical Corporation; Melamine: Nissan Chemical Industries, Ltd. Additive: X-50-1095C: Defoamer, Shin-Etsu Chemical Co., Ltd. Non-reactive diluent: EDGAC: Sanyo Chemical Industries, Ltd.

Test piece preparation process A printed wiring board using a flexible substrate (polyimide film, Panasonic Corporation, film thickness 25 μm, conductor (Cu foil) thickness 12.5 μm) was surface-treated with a 5% by mass aqueous sulfuric acid solution, and then the photosensitive resin compositions of the examples and comparative examples prepared as described above were applied by screen printing to form a coating film on the substrate. After the coating film was formed, it was pre-dried in a BOX furnace at 80 ° C. for 20 minutes. After pre-drying, the coating film was exposed to light at an exposure dose of 400 mJ / cm ² (exposure device: direct imaging (DI) exposure device "Nuvoggo1000R" (light source: laser) manufactured by Orbotech) to perform a photocuring treatment of the coating film. After exposure, the coating film was developed using a 1% by mass aqueous sodium carbonate solution at a development temperature of 30 ° C. and a development pressure of 0.2 MPa at a spray pressure. After development, a post-cure was performed in a BOX furnace at 150 ° C. for 60 minutes to form a dry cured coating film with a thickness of 20 μm on the substrate.

(1) Gold plating resistance The test specimens obtained in the above test specimen preparation process were plated using commercially available electroless nickel plating baths and electroless gold plating baths under the conditions of nickel 3 μm to 5 μm and gold 0.05 μm. The presence or absence of peeling of the cured coating film and the presence or absence of plating penetration were visually evaluated, and then the presence or absence of peeling of the cured coating film was evaluated by a tape peeling test. The evaluation criteria were as follows, and an ○ rating was judged to be a pass.
◯: After the tape peeling test, no peeling was observed at all for any film thickness.
Δ: After the tape peeling test, slight peeling was observed in the cured coating film.
×: After the tape peeling test, significant peeling was observed in the cured coating film.

(2) Insulation Reliability According to the above test specimen preparation process, a test specimen was prepared using comb electrodes (line/space = 165 μm/165 μm) of an IPC-SM840B B-25 test coupon of IPC-TM-650, and the insulation resistance after humidification for 200 hours at 85°C and 85% R.H. was measured by applying DC 50 V. The evaluation criteria are as follows, and a rating of △ or higher was determined to be a pass.
⊚: The insulation resistance value is 5.0×10 ¹³ Ω or more.
⊚: The insulation resistance value is 1.0×10 ¹³ Ω or more and less than 5.0×10 ¹³ Ω.
◯: The insulation resistance value is 1.0×10 ¹² Ω or more and less than 1.0×10 ¹³ Ω.
Δ: The insulation resistance value is 1.0×10 ¹⁰ Ω or more and less than 1.0×10 ¹² Ω.
×: The insulation resistance value is less than 1.0×10 ¹⁰ Ω.

(3) Storage stability The photosensitive resin compositions of the Examples and Comparative Examples were stored in a refrigerator at 5 to 10° C. for one month, and the presence or absence of crystallization of the photosensitive resin compositions after storage was evaluated using a grind gauge. The evaluation criteria were as follows, and a rating of △ or higher was determined to be acceptable.
◯: No crystals of 10 μm or more △: Crystals of 10 μm to 15 μm present ×: Crystals of more than 15 μm present

The evaluation results are shown in Table 1 below.

As shown in Table 1 above, the photosensitive resin compositions of Examples 1 to 8, which use (B) an α-aminoalkylphenone-based photopolymerization initiator as the photopolymerization initiator and (C) a photoreaction stabilizer of a compound represented by general formula (1) and (E) an inorganic ion exchanger, were able to obtain cured products with excellent insulation reliability and gold plating resistance without impairing the storage stability of the photosensitive resin composition. As such, the photosensitive resin compositions of Examples 1 to 8 were able to obtain excellent insulation reliability, including insulation reliability in the thickness direction of the insulating coating, even for fine-pitched insulating coatings and insulating coatings in contact with another conductive material.

In particular, Examples 2 and 4, in which the light reaction stabilizer (C) was contained at about 2.0 parts by mass per 100 parts by mass of the photosensitive resin (A), showed improved insulation reliability compared to Examples in which the light reaction stabilizer (C) was contained at about 0.5 parts by mass per 100 parts by mass of the photosensitive resin (A). Also, Examples 3 to 5, in which a mixture of an aluminum compound and a zirconia compound was used as the inorganic ion exchanger (E), showed improved insulation reliability. Also, Examples 1 to 7, in which 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone was used as the α-aminoalkylphenone-based photopolymerization initiator (B), showed improved storage stability of the photosensitive resin composition compared to Example 8, in which 1-(4-morpholinophenyl)-2-(dimethylamino)-2-benzyl-1-butanone was used.

On the other hand, in Comparative Example 1, which did not contain the light reaction stabilizer (C), and Comparative Example 2, which did not contain the inorganic ion exchanger (E), it was not possible to obtain insulation reliability and gold plating resistance.

The photosensitive resin composition of the present invention can give a cured product having excellent insulation reliability and gold plating resistance, and is therefore particularly useful in the fields of printed wiring boards having a fine-pitched insulating coating, printed wiring boards having an insulating coating in contact with another conductive material, and printed wiring boards requiring versatility.

Claims (14)

(A) a photosensitive resin, (B) an α-aminoalkylphenone-based photopolymerization initiator, (C) a photoreaction stabilizer, (D) an epoxy compound, (E) an inorganic ion exchanger, (F) a reactive diluent, and (G) a colorant;
The (C) photoreaction stabilizer is represented by the following general formula (1):

(In formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent H or an alkyl group) ,
The photosensitive resin composition contains the (C) photoreaction stabilizer in an amount of 1.0 part by mass or more and 10 parts by mass or less per 100 parts by mass of the (A) photosensitive resin . 2. The photosensitive resin composition according to claim 1, wherein R ¹ , R ² , R ³ and R ⁴ in the general formula (1) are each independently C _n H _2n+1 , where n is an integer of 1 to 10. The photosensitive resin composition according to claim 1 or 2, wherein the (C) photoreaction stabilizer contains at least one benzophenone derivative selected from the group consisting of 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone. The photosensitive resin composition according to claim 1 , wherein the photoreaction stabilizer (C) is contained in an amount of 1.0 part by mass or more and 5.0 parts by mass or less per 100 parts by mass of the photosensitive resin (A). 5. The photosensitive resin composition according to claim 1 , wherein the (C) photoreaction stabilizer is contained in an amount of 15 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the (B) α-aminoalkylphenone-based photopolymerization initiator. 6. The photosensitive resin composition according to claim 1, wherein the inorganic ion exchanger (E) comprises at least one selected from the group consisting of a zirconia compound, a mixture of an aluminum compound and a zirconia compound, a bismuth compound, and a mixture of a bismuth compound and a zirconia compound. 6. The photosensitive resin composition according to claim 1, wherein the inorganic ion exchanger (E) comprises a mixture of an aluminum compound and a zirconia compound. 8. The photosensitive resin composition according to claim 1, wherein the inorganic ion exchanger (E) is contained in an amount of 3.0 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the photosensitive resin (A). The photosensitive resin composition according to any one of claims 1 to 8 , wherein the (B) α-aminoalkylphenone-based photopolymerization initiator comprises 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone. The photosensitive resin composition according to any one of claims 1 to 9 , wherein the (B) α-aminoalkylphenone-based photopolymerization initiator is contained in an amount of 0.50 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the (A) photosensitive resin. The photosensitive resin composition according to claim 1 , further comprising an oxime ester-based photopolymerization initiator. The photosensitive resin composition according to claim 11 , wherein the oxime ester photopolymerization initiator comprises (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime. A photocured product of the photosensitive resin composition according to any one of claims 1 to 12 . A printed wiring board having a photocured film of the photosensitive resin composition according to any one of claims 1 to 12 .