JP2023143764A - Photosensitive resin composition, photocured product of photosensitive resin composition, and printed wiring board having photocured film of photosensitive resin composition - Google Patents

Abstract

To provide a photosensitive resin composition which enables formation of a protective film that is excellent in flux resistance, matte appearance and flexibility while having insulation reliability.SOLUTION: A photosensitive resin composition contains (A) a carboxyl group-containing photosensitive resin, (B) an inorganic filler, (C) a photopolymerization initiator, (D) a reactive diluent, and (E) an epoxy compound, wherein (B) the inorganic filler is a talc having a particle diameter D50 for 50 vol.% of a cumulative volume percentage of 0.7 μm or more and 5.5 μm or less, and (C) the photopolymerization 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

The present invention relates to a photosensitive resin composition suitable as a coating material, for example, an insulating coating material for coating a conductive circuit pattern formed on a printed wiring board having a rigid substrate or a flexible substrate, and The present invention relates to a photocured product and a printed wiring board having a photocured film of the photosensitive resin composition.

A conductive circuit pattern such as copper foil is formed on the printed wiring board board, and electronic components are mounted on the soldering lands of the conductive circuit pattern by soldering, and the parts of the conductive circuit other than the soldering lands are protected. It is covered with an insulating film (solder resist film). Particularly in the case of a printed wiring board having a flexible substrate, the protective film is required to have flexibility. Further, the protective film may be required to have a matte appearance.

Therefore, (A) a thermosetting resin, (B) a resin having an acidic functional group and an unsaturated double bond, (C) a resin having an acidic functional group and no unsaturated double bond, (D ) A thermosetting/photosensitive resin composition containing a compound having an unsaturated double bond, (E) a photopolymerization initiator, and (F) an organic filler has been proposed (Patent Document 1). In Patent Document 1, by using (F) an organic filler, particularly organic beads having urethane bonds, the protective film is given flexibility that can withstand repeated bending. Furthermore, by using organic beads, a matte appearance can be imparted to the protective film.

On the other hand, in the mounting process in which electronic components are mounted by soldering on the soldering lands of a conductive circuit pattern, electronic components are placed on a printed wiring board on which a protective film has been formed, and the printed wiring board is heated in a reflow oven. Solder the electronic components on top. In the above mounting process, solder containing a flux component may be used. When solder containing a flux component is used, the flux component oozes out from the solder, and the leaked flux component penetrates into the protective film through the surface of the insulation coating and the openings of the conductor circuit pattern. Something happened.

If the flux component penetrates into the protective film, the protective film may peel off from the printed wiring board or bulge, which may cause problems with the insulating film. Therefore, the protective film may be required to have flux resistance that can prevent the protective film from peeling off or blistering from the printed wiring board even if the flux component oozes out from the solder.

However, in the protective film formed using the photosensitive resin composition of Patent Document 1, since the organic filler has low heat resistance, when the flux component oozes out from the solder during heat treatment in a reflow oven, the flux component protects the film. It penetrates into the film, causing the protective film to peel or swell from the printed wiring board, leaving room for improvement in flux resistance.

In addition, by blending an inorganic filler into a photosensitive resin composition, the heat resistance of the protective film is improved, but flexibility cannot be obtained, and if the particle size of the inorganic filler is reduced in order to impart flexibility, However, there was a problem that a matte appearance could not be obtained.

Japanese Patent Application Publication No. 2022-017603

In view of the above circumstances, an object of the present invention is to provide a photosensitive resin composition capable of forming a protective film having excellent flux resistance, matte appearance, and flexibility while having insulation reliability.

The gist of the configuration of the present invention is as follows.
[1] Contains (A) a carboxyl group-containing photosensitive resin, (B) an inorganic filler, (C) a photopolymerization initiator, (D) a reactive diluent, and (E) an epoxy compound,
The inorganic filler (B) is talc with a cumulative volume percentage of 50 volume % and a particle diameter D50 of 0.7 μm or more and 5.5 μm or less,
A photosensitive resin in which the photopolymerization initiator (C) contains at least one selected from the group consisting of (C1) an α-aminoalkylphenone photopolymerization initiator and (C2) an oxime ester photopolymerization initiator. Composition.
[1] The photosensitive resin composition described in .
[3] The photosensitive resin composition according to [2], wherein the inorganic filler (B) is the untreated talc having a cumulative volume percentage of 50 volume % and a particle diameter D50 of 1.3 μm or more and 2.3 μm or less. .
[1] The photosensitive resin composition described in .
[5] The photosensitive resin composition according to [4], wherein the inorganic filler (B) is the surface-treated talc having a cumulative volume percentage of 50 volume % and a particle diameter D50 of 2.0 μm or more and 4.0 μm or less. .
[6] The photosensitive resin composition according to [4] or [5], wherein the organic compound is at least one selected from the group consisting of epoxysilane compounds and (meth)acrylic silane compounds.
[7] The photosensitive resin composition according to [1], which contains the talc in an amount of 8 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin (A).
[8] The photosensitive resin composition according to [1], which contains 30 parts by mass or more and 70 parts by mass or less of the talc based on 100 parts by mass of the carboxyl group-containing photosensitive resin (A).
[9] The photosensitive resin composition according to [1], which does not contain an organic filler.
[10] The photosensitive resin composition according to [1], further containing an organic filler.
[11] The photosensitive resin composition according to [1], wherein the carboxyl group-containing photosensitive resin (A) has a cresol novolac type epoxy resin skeleton.
[12] The α-aminoalkylphenone photopolymerization initiator (C1) contains 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone. The photosensitive resin composition according to [1].
[13] The oxime ester photoinitiator (C2) is (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)- The photosensitive resin composition according to [1], which contains 2-methylphenyl)methanone O-acetyloxime.
[14] A photocured product of the photosensitive resin composition according to [1].
[15] A printed wiring board having a photocured film of the photosensitive resin composition according to [1].

According to an aspect of the photosensitive resin composition of the present invention, (A) a carboxyl group-containing photosensitive resin, (B) an inorganic filler, (C) a photopolymerization initiator, (D) a reactive diluent, (E) an epoxy compound; (B) the inorganic filler is talc with a cumulative volume percentage of 50 volume % and a particle diameter D50 of 0.7 μm or more and 5.5 μm or less; The initiator has insulation reliability by containing at least one selected from the group consisting of (C1) an α-aminoalkylphenone photopolymerization initiator and (C2) an oxime ester photopolymerization initiator. At the same time, it is possible to obtain a photosensitive resin composition that can form a protective film with excellent flux resistance, matte appearance, and flexibility.

According to an aspect of the photosensitive resin composition of the present invention, the inorganic filler (B) is surface-treated with an organic compound having a particle diameter D50 of 1.3 μm or more and 2.3 μm or less at a cumulative volume percentage of 50 volume %. By using untreated talc, flux resistance, matte appearance, and flexibility can be improved in a well-balanced manner.

According to an aspect of the photosensitive resin composition of the present invention, the inorganic filler (B) is surface-treated with an organic compound having a particle diameter D50 of 0.7 μm or more and 5.5 μm or less at a cumulative volume percentage of 50 volume %. The surface treated talc ensures improved insulation reliability, matte appearance and flexibility.

According to an aspect of the photosensitive resin composition of the present invention, the inorganic filler (B) is surface-treated with an organic compound having a cumulative volume percentage of 50% by volume and a particle diameter D50 of 2.0 μm or more and 4.0 μm or less. The surface-treated talc ensures further improvements in insulation reliability, matte appearance, and flexibility.

According to an aspect of the photosensitive resin composition of the present invention, the organic compound is at least one selected from the group consisting of epoxysilane compounds and (meth)acrylic silane compounds, which improves insulation reliability and matteness. Appearance and flexibility are further improved.

According to an aspect of the photosensitive resin composition of the present invention, the talc is contained in 8 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin, thereby achieving flux resistance, A matte appearance and flexibility can be achieved more reliably.

According to an aspect of the photosensitive resin composition of the present invention, the talc is contained in 30 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin, thereby achieving flux resistance, The matte appearance and flexibility can be improved in a well-balanced manner.

According to the aspect of the photosensitive resin composition of the present invention, flux resistance is more reliably improved by not containing an organic filler.

According to an aspect of the photosensitive resin composition of the present invention, the carboxyl group-containing photosensitive resin (A) has a cresol novolac type epoxy resin skeleton, thereby more reliably improving insulation reliability and flux resistance. .

According to an embodiment of the photosensitive resin composition of the present invention, the (C1) α-aminoalkylphenone photopolymerization initiator is 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4 -Methylbenzyl)-1-butanone can contribute to further improvement of flux resistance.

According to an aspect of the photosensitive resin composition of the present invention, the oxime ester photoinitiator (C2) is (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1 -Methoxypropan-2-yl)oxy)-2-methylphenyl)methanone Containing O-acetyloxime can contribute to further improvement of flux resistance.

Next, the photosensitive resin composition of the present invention will be explained below. The photosensitive resin composition of the present invention comprises (A) a carboxyl group-containing photosensitive resin, (B) an inorganic filler, (C) a photopolymerization initiator, (D) a reactive diluent, and (E) an epoxy resin. The inorganic filler (B) is talc with a cumulative volume percentage of 50 volume % and a particle diameter D50 of 0.7 μm or more and 5.5 μm or less, and the photopolymerization initiator (C) is , (C1) an α-aminoalkylphenone photopolymerization initiator, and (C2) an oxime ester photopolymerization initiator. In the photosensitive resin composition of the present invention, talc having a cumulative volume percentage of 50 volume % and a particle diameter D50 of 0.7 μm or more and 5.5 μm or less is blended as the (B) inorganic filler. In the photosensitive resin composition of the present invention, the inorganic filler (B) is made of talc having a cumulative volume percentage of 50% by volume and a particle diameter D50 of 0.7 μm or more and 5.5 μm or less, barium sulfate, silica, mica, etc. Contains no other inorganic fillers. With the photosensitive resin composition of the present invention, it is possible to form a protective film that has insulation reliability and is excellent in flux resistance, matte appearance, and flexibility.

<(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 include resins having one or more photosensitive unsaturated double bonds and a free carboxyl group. As the carboxyl group-containing photosensitive resin, for example, a radically polymerizable unsaturated monocarboxylic acid is reacted with at least a portion of the epoxy groups of a polyfunctional epoxy resin having two or more epoxy groups in one molecule. Examples include polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resins having a structure obtained by obtaining a saturated monocarboxylated epoxy resin and reacting the generated hydroxyl groups with a polybasic acid and/or a polybasic acid anhydride. It will be done.

Polyfunctional epoxy resin A polyfunctional epoxy resin forms the skeleton of a carboxyl group-containing photosensitive resin. The epoxy equivalent of the polyfunctional epoxy resin is not particularly limited, and for example, the upper limit thereof is preferably 3000 g/eq, more preferably 2000 g/eq, even more 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, particularly preferably 200 g/eq. The chemical structure of the polyfunctional epoxy resin is not particularly limited, and includes, for example, biphenylaralkyl epoxy resin, phenylaralkyl epoxy resin, biphenyl epoxy resin, naphthalene epoxy resin, dicyclopentadiene epoxy resin, and silicone-modified epoxy resin. rubber modified epoxy resins such as 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, cycloaliphatic polyfunctional Examples include 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. These polyfunctional epoxy resins may be used alone or in combination of two or more.

Among these multifunctional epoxy resins, cresol novolak type epoxy resins are preferable because they more reliably improve insulation reliability and flux resistance. It is preferable to have.

Radically 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, resulting in the formation of a radically polymerizable unsaturated monocarboxylic acid in the epoxy resin. Photosensitive unsaturated double bonds derived from acids are introduced to impart photosensitivity to the skeleton of the polyfunctional epoxy resin. Examples of radically polymerizable unsaturated monocarboxylic acids include acrylic acid, methacrylic acid (acrylic acid and/or methacrylic acid is sometimes referred to as "(meth)acrylic acid"), crotonic acid, tiglic acid, angelic acid, Examples include cinnamic acid. Among these, (meth)acrylic acid is preferred in terms of reactivity, ease of availability, and ease of handling. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

The method of reaction between the polyfunctional epoxy resin and the radically polymerizable unsaturated monocarboxylic acid is not particularly limited. An example is a method of heating in an organic solvent).

Polybasic acid and/or polybasic acid anhydride Polybasic acid and/or polybasic acid anhydride reacts with the hydroxyl group of the unsaturated monocarboxylated epoxy resin to form an ester bond, thereby releasing it into the photosensitive resin. carboxyl group is introduced. The polybasic acid and/or polybasic acid anhydride is not particularly limited, and either saturated or unsaturated polybasic acids can 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, and 4-methyltetrahydrophthalic acid. Tetrahydrophthalic acids such as ethyltetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid acids, hexahydrophthalic acids such as 4-ethylhexahydrophthalic acid, bifunctional carboxylic acids such as diglycolic acid, trifunctional carboxylic acids such as trimellitic acid, tetrafunctional carboxylic acids such as pyromellitic acid, etc. Can be mentioned. Examples of the polybasic acid anhydride 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.

The method of reacting the radically polymerizable unsaturated monocarboxylated epoxy resin with the polybasic acid and/or polybasic acid anhydride is not particularly limited. A method of heating the polybasic acid anhydride and/or polybasic acid anhydride in an appropriate solvent (for example, an inert organic solvent) can be mentioned.

In addition, in place of the polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin, if necessary, some of the carboxyl groups of the polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin may be further added. A carboxyl group-containing photosensitive resin having a chemical structure obtained by reacting a compound (for example, a glycidyl compound) having one or more radically polymerizable unsaturated groups and an epoxy group may be used. In the carboxyl group-containing photosensitive resin obtained by further reacting a compound having a radically polymerizable unsaturated group and an epoxy group, a radically polymerizable unsaturated group is added to the side chain of the polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin. It has a chemical structure that has been further introduced. Therefore, a carboxyl group-containing photosensitive resin having a chemical structure obtained by reacting a compound having a radically polymerizable unsaturated group with an epoxy group is more photopolymerizable than a polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin. It has excellent reactivity and further improves photosensitive characteristics.

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

The reaction method of the polybasic acid-modified radically polymerizable unsaturated monocarboxylated epoxy resin and the compound having a radically polymerizable unsaturated group and an epoxy group is not particularly limited. Examples include a method of heating an oxidized epoxy resin and a compound having a radically polymerizable unsaturated group and an epoxy group in an appropriate solvent (for example, an inert organic solvent).

The acid value of the carboxyl group-containing photosensitive resin is not particularly limited, and for example, the lower limit thereof is preferably 30 mgKOH/g, 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 reliably preventing dissolution of the exposed area (photocured area) by an alkaline developer, which further ensures insulation reliability. 150 mgKOH/g is particularly preferable from the viewpoint of improving.

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 as a protective film. In terms of contribution, 6000 is preferred, 7000 is more preferred, and 8000 is particularly preferred. On the other hand, the upper limit of the mass average molecular weight of the carboxyl group-containing photosensitive resin is preferably 200,000, more preferably 100,000, and particularly preferably 50,000, from the viewpoint of contributing to improving alkali developability. In addition, 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.

The carboxyl group-containing photosensitive resin may be prepared in the reaction step using the above 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-4785", "Lipoxy SP-4785L" (all manufactured by Showa Denko K.K.), "ZAR-2000", and "Lipoxy SP-4785L". ZFR-1122”, “ZFR-1887”, “FLX-2089”, “ZCR-1569H”, “ZCR-1601H” (Nippon Kayaku Co., Ltd.), “Cyclomer P (ACA) Z-250” ( Daicel Corporation), etc. These carboxyl group-containing photosensitive resins may be used alone or in combination of two or more.

<(B) Inorganic filler>
The inorganic filler as component (B) is talc with a cumulative volume percentage of 50% by volume and a particle diameter D50 (hereinafter sometimes simply referred to as "D50") of 0.7 μm or more and 5.5 μm or less. In the photosensitive resin composition of the present invention, the inorganic filler (B) consists of particulate talc with a D50 of 0.7 μm or more and 5.5 μm or less, and contains other inorganic fillers such as barium sulfate, silica, mica, etc. Not yet. (B) Since the inorganic filler is talc with a D50 of 0.7 μm or more and 5.5 μm or less, it forms a protective film with excellent flux resistance, matte appearance, and flexibility while maintaining insulation reliability. A photosensitive resin composition can be obtained.

Examples of talc include untreated talc whose surface has not been treated with an organic compound (hereinafter simply referred to as "untreated talc"), and surface-treated talc whose surface has been treated with an organic compound (hereinafter simply referred to as "surface treated talc"). (Sometimes referred to as "treated talc.").

As long as D50 is 0.7 μm or more and 5.5 μm or less, the particle size and particle size distribution of talc are not particularly limited, regardless of whether it is untreated talc or surface-treated talc. In the case of untreated talc, the lower limit of D50 is preferably 0.9 μm, more preferably 1.1 μm, even more preferably 1.3 μm, and even more preferably 1.5 μm from the viewpoint of further improving flux resistance and matte appearance. Particularly preferred. On the other hand, the upper limit of D50 is preferably 5.0 μm, more preferably 4.0 μm, even more preferably 2.3 μm, and particularly preferably 2.1 μm, from the viewpoint of further improving flexibility. From the above, when the D50 of the untreated talc is within the range of the preferable upper limit and lower limit, flux resistance, matte appearance, and flexibility can be improved in a well-balanced manner.

Since the talc is surface-treated talc, insulation reliability, matte appearance, and flexibility are reliably improved. In the case of surface-treated talc, the lower limit of D50 is preferably 1.0 μm, more preferably 1.5 μm, particularly preferably 2.0 μm, from the viewpoint of further improving insulation reliability, matte appearance, and flexibility. . On the other hand, the upper limit of D50 is preferably 5.0 μm, particularly preferably 4.0 μm, from the viewpoint of further improving flexibility.

Examples of organic compounds used for surface treatment of talc include silane compounds. Examples of the silane compound include epoxy-functional silane compounds, (meth)acrylic silane compounds, and phenylsilane compounds. Among these, (meth)acrylic silane compounds are preferred, and acrylic silane compounds are particularly preferred, from the viewpoint of further improving flux resistance.

The amount of talc with a D50 of 0.7 μm or more and 5.5 μm or less is not particularly limited, but the lower limit is (A) relative to 100 parts by mass (solid content, the same hereinafter) of the carboxyl group-containing photosensitive resin. From the viewpoint of more reliably obtaining flux resistance and matte appearance, 8 parts by mass is preferable, from the viewpoint of further improving flux resistance and matte appearance, 30 parts by mass is more preferable, and particularly preferably 35 parts by weight. On the other hand, the upper limit of the content of talc with a D50 of 0.7 μm or more and 5.5 μm or less is set based on 100 parts by mass of (A) carboxyl group-containing photosensitive resin, from the viewpoint of more reliably obtaining flexibility. It is preferably 80 parts by mass, more preferably 70 parts by mass, and particularly preferably 60 parts by mass in terms of further improving flexibility. From the above, by containing talc having a D50 of 0.7 μm or more and 5.5 μm or less in the range of 8 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin (A), flux resistance is improved. 30 parts by mass or more of talc having a D50 of 0.7 μm or more and 5.5 μm or less per 100 parts by mass of (A) carboxyl group-containing photosensitive resin. By containing 70 parts by mass or less, flux resistance, matte appearance, and flexibility can be improved in a well-balanced manner.

<(C) Photopolymerization initiator>
By incorporating the photopolymerization initiator (component (C)), the curing properties of the cured coating film are improved, the penetration of flux components into the protective film is suppressed, and a protective film with excellent flux resistance can be formed. .

In the photosensitive resin composition of the present invention, the photopolymerization initiator is at least one selected from the group consisting of (C1) an α-aminoalkylphenone photopolymerization initiator and (C2) an oxime ester photopolymerization initiator. Contains.

（式（１）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。これらのうち、保護膜の硬化性が確実に向上して耐フラックス性のさらなる向上に寄与できる点から、α－アミノアルキルフェノン系光重合開始剤として、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（１）中におけるＲがメチル基）が好ましい。これらのα－アミノアルキルフェノン系光重合開始剤は、単独で使用してもよく、２種以上を併用してもよい。 As the α-aminoalkylphenone photopolymerization initiator that is the component (C1), for example, the following general formula (1) is used.

Examples include compounds represented by (R in formula (1) represents hydrogen or an alkyl group having 1 to 5 carbon atoms). Among these, 1-(4-morpholinophenyl)-2- (Dimethylamino)-2-(4-methylbenzyl)-1-butanone (R in formula (1) is a methyl group) is preferred. These α-aminoalkylphenone photopolymerization initiators may be used alone or in combination of two or more.

As the oxime ester photopolymerization initiator which is the component (C2), for example, (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy) )-2-methylphenyl)methanone O-acetyloxime, 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone 1-[9-ethyl-6-( 2-Methylbenzoyl)-9H-carbazol-3-yl]-1-(0-acetyloxime), 2-(acetyloxyiminomethyl)thioxanthene-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- Examples include ethylhexyl)-6-nitro-9H-carbazol-3-yl]-,1,8-bis(O-acetyloxime). Among these, (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-(( 1-Methoxypropan-2-yl)oxy)-2-methylphenyl)methanone O-acetyloxime is preferred. These oxime ester photopolymerization initiators may be used alone or in combination of two or more.

The amount of at least one photopolymerization initiator selected from the group consisting of α-aminoalkylphenone photopolymerization initiators and oxime ester photopolymerization initiators is not particularly limited, but the lower limit is From the viewpoint of reliably improving the curability of the film and reliably obtaining excellent flux resistance, it is preferably 0.50 parts by mass, and 1 0 parts by weight is more preferred, and 1.5 parts by weight is particularly preferred. On the other hand, the upper limit of the amount of at least one photopolymerization initiator selected from the group consisting of α-aminoalkylphenone photopolymerization initiators and oxime ester photopolymerization initiators is set to prevent deterioration of developability and halation. From the viewpoint of preventing this, the amount is preferably 8.0 parts by weight, more preferably 6.0 parts by weight, and particularly preferably 4.0 parts by weight based on 100 parts by weight of the carboxyl group-containing photosensitive resin (A).

<(D) Reactive diluent>
The reactive diluent which is component (D) is, for example, a photopolymerizable monomer, and is a compound having at least one polymerizable double bond per molecule, preferably two or more per molecule. The reactive diluent contributes to reinforcing photocuring of the photosensitive resin composition and imparting sufficient strength, heat resistance, acid resistance, alkali resistance, etc. to the cured coating film of the photosensitive resin composition.

Examples of the reactive diluent include monofunctional (meth)acrylate compounds such as monofunctional (meth)acrylate compounds, bifunctional (meth)acrylate compounds, trifunctional (meth)acrylate compounds, and tetrafunctional or higher (meth)acrylate compounds. Alternatively, monomers of polyfunctional (meth)acrylate compounds can be mentioned. Examples of monomers of (meth)acrylate compounds include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, diethylene glycol mono(meth)acrylate, 2-hydroxy-3- Monofunctional (meth)acrylate compounds such as 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 phosphoric acid di(meth)acrylate, Allyl Bifunctional (meth)acrylate compounds such as cyclohexyl di(meth)acrylate, isocyanurate di(meth)acrylate; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate , trifunctional (meth)acrylate compounds such as propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate; ditrimethylolpropane tetra(meth)acrylate, propionic acid-modified dipentaerythritol penta(meth) Examples include tetrafunctional or higher functional (meth)acrylate compounds such as 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 the reactive diluent is not particularly limited, but is preferably 5.0 parts by mass or more and 70 parts by mass or less, and 15 parts by mass or more and 40 parts by mass, based on 100 parts by mass of the (A) carboxyl group-containing photosensitive resin. The following are particularly preferred.

<(E) Epoxy compound>
The epoxy compound as component (E) is used to increase the crosslinking density of the cured product of the photosensitive resin composition and impart sufficient hardness to the cured product. The improved crosslinking density of the epoxy compound suppresses penetration of flux components into the protective film, contributing to the formation of a protective film with excellent flux resistance.

Examples of epoxy compounds 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 carboxyl group-containing photosensitive resin described above. Specifically, for example, 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, and ε-caprolactone. Modified epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, cresol novolac type epoxy resin such as ortho-cresol novolac type, bisphenol novolac type epoxy resin, cycloaliphatic polyfunctional epoxy resin, glycidyl ester type polyfunctional epoxy resin , glycidylamine type polyfunctional epoxy resin, heterocyclic polyfunctional epoxy resin, bisphenol modified novolak type epoxy resin, polyfunctional modified novolak type epoxy resin and the like. Furthermore, examples of epoxy compounds other than epoxy resins include triglycidyl isocyanurate and the like. These epoxy compounds may be used alone or in combination of two or more. As the epoxy compound, the same type of epoxy resin as the polyfunctional epoxy resin used for preparing the carboxyl group-containing photosensitive resin described above can be used.

The amount of the epoxy compound is not particularly limited, but is preferably 5.0 parts by mass or more and 60 parts by mass or less, and 10 parts by mass or more and 40 parts by mass or less, based on 100 parts by mass of the carboxyl group-containing photosensitive resin (A). Particularly preferred.

In the photosensitive resin composition of the present invention, talc with a D50 of 0.7 μm or more and 5.5 μm or less is blended as the (B) inorganic filler, thereby creating a protective film with an excellent matte appearance and flexibility. Since it can be formed, it is not necessary to contain an organic filler. By not containing an organic filler, flux resistance is more reliably improved. On the other hand, if necessary, it may further contain an organic filler as an optional component. By containing an organic filler, the flux resistance is slightly lowered, but the flexibility is improved, compared to the case where the organic filler is not contained.

Examples of organic fillers include polymers such as urethane resins (polymer of isocyanate and polyol), acrylic resins, polyethylene, copolymers of styrene and butadiene such as styrene-butadiene rubber, and silicone resins such as silicone rubber. be able to. These organic fillers may be used alone or in combination of two or more. The shape of the organic filler is not particularly limited, but is preferably particulate.

The average particle diameter of the particulate organic filler is not particularly limited, but its lower limit is preferably 0.1 μm, particularly preferably 0.5 μm, from the viewpoint of improving the matte appearance. On the other hand, the upper limit of the average particle diameter of the particulate organic filler is preferably 20 μm, particularly preferably 10 μm, from the viewpoint of imparting excellent flexibility.

The upper limit of the blending amount of the organic filler is preferably 20 parts by weight, particularly preferably 15 parts by weight, based on 100 parts by weight of the carboxyl group-containing photosensitive resin (A), from the viewpoint of obtaining flux resistance. On the other hand, in the case of blending an organic filler, the lower limit of the blending amount of the organic filler is 1.0 parts by mass based on 100 parts by mass of (A) carboxyl group-containing photosensitive resin, from the viewpoint of further improving flexibility. is preferred, and 5.0 parts by mass is particularly preferred.

In the photosensitive resin composition of the present invention, in addition to the above-mentioned components (A) to (E), optional components include (C1) an α-aminoalkylphenone photopolymerization initiator and ( C2) Photopolymerization initiators other than the oxime ester photopolymerization initiator may be blended. Examples of other photopolymerization initiators include benzoin series such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, and benzoin isobutyl ether; acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy Acetophenone types such as -2-phenylacetophenone and 2,2-diethoxy-2-phenylacetophenone; Benzophenone types such as benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, and dichlorobenzophenone; 2-methylanthraquinone, 2 - Anthraquinones such as ethyl anthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone; 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, etc. Thioxanthone series; 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-phenylpropane-1- 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 photosensitive resin composition of the present invention may further contain other optional components, such as colorants, additives, antifoaming agents, flame retardants, non-reactive diluents, etc., as necessary. .

Colorants include pigments, dyes, etc., but are not particularly limited, and include white colorants, black colorants, blue colorants, green colorants, yellow colorants, purple colorants, orange colorants, red colorants, etc. Any colorant can be used depending on the desired color. Furthermore, by containing a colorant, hiding power can be imparted to the protective film. Colorants include, for example, inorganic colorants such as titanium dioxide which is a white colorant, acetylene black and carbon black which are black colorants, phthalocyanine green which is a green colorant, and phthalocyanine blue and Rio which are blue colorants. Examples include organic colorants such as phthalocyanine-based colorants such as Nord Blue, and diketopyrrolopyrrole-based colorants such as chromophthalorange, which is an orange colorant. These colorants may be used alone or in combination of two or more.

Examples of additives 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, Examples include guanamine and its derivatives, amine imide (AI), latent curing agents such as polyamines, and thermosetting catalysts such as aliphatic dimethylurea.

Examples of antifoaming agents include silicone polymers, hydrocarbon polymers, and acrylic polymers.

The flame retardant is used to impart flame retardancy to the cured coating film 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 phosphorus flame retardants include tris(chloroethyl)phosphate, tris(2,3-dichloropropyl)phosphate, tris(2-chloropropyl)phosphate, tris(2,3-bromopropyl)phosphate, and tris(bromochloropropyl)phosphate. Halogen-containing phosphate esters such as propyl) phosphate, 2,3-dibromopropyl-2,3-chloropropyl phosphate, tris(tribromophenyl) phosphate, tris(dibromophenyl) phosphate, and tris(tribromoneopentyl) phosphate Non-halogenated aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate; Triphenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, tricresyl phosphate, trixylenyl Phosphate, xylenyl diphenyl phosphate, tris (isopropylphenyl) phosphate, isopropylphenyl diphenyl phosphate, diisopropylphenyl phenyl phosphate, tris (trimethylphenyl) phosphate, tris (t-butylphenyl) phosphate, hydroxyphenyl diphenyl phosphate, octyldiphenyl phosphate, etc. Non-halogenated aromatic phosphoric acid ester; aluminum tris-diethyl phosphinate, aluminum tris-methylethyl phosphinate, aluminum tris-diphenyl phosphinate, zinc bis-diethyl phosphinate, zinc bismethylethyl phosphinate, zinc bis-diphenyl phosphinate, bis-diethyl phosphine. Metal salts of phosphinic acids such as titanyl tetrakis diethyl phosphinate, titanium tetrakis diethyl phosphinate, titanyl bismethylethyl phosphinate, titanium tetrakis methyl ethyl phosphinate, titanium bis diphenyl phosphinate, titanium tetrakis diphenyl phosphinate, 9,10-dihydro-9- HCA modified types such as oxa-10-phosphaphenanthrene-10-oxide (hereinafter referred to as HCA), addition reaction products of HCA and acrylic acid ester, addition reaction products of HCA and epoxy resin, addition reaction products of HCA and hydroquinone, etc. and phosphine oxide compounds such as diphenylvinylphosphine oxide, triphenylphosphine oxide, trialkylphosphine oxide, and tris(hydroxyalkyl)phosphine oxide.

The non-reactive diluent is a component for adjusting the viscosity, coating properties, and drying properties of the photosensitive resin composition. Examples of non-reactive diluents include organic solvents that are inert to each component contained 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, and cyclohexane and methylcyclohexane. Alicyclic hydrocarbons, petroleum solvents such as petroleum ether and petroleum naphtha, cellosolves, cellosolves such as butyl cellosolve, carbitol, carbitols such as butyl carbitol, ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, Examples include esters such as carbitol acetate, butyl carbitol acetate, ethylene glycol acetate, ethylene diglycol acetate, and diethylene glycol monoethyl ether acetate. These may be used alone or in combination of two or more.

Further, the photosensitive resin composition of the present invention may contain an extender pigment such as aluminum hydroxide as a flame retardant.

Next, a method for producing the photosensitive resin composition of the present invention will be explained. The method for producing the photosensitive resin composition of the present invention is not limited to a specific method, and for example, after blending each of the above components in a predetermined ratio, at room temperature (e.g., 25°C), using a three-roll mill, a ball mill, or a sand mill. It can be produced by kneading or mixing the blended components using a kneading means such as a bead mill, a kneader, or a stirring or mixing means such as a super mixer, a planetary mixer, or a trimix. Further, before kneading or mixing, preliminary kneading or preliminary mixing may be performed as necessary.

Next, an example of how to use the photosensitive resin composition of the present invention will be explained. Here, a method of coating a printed wiring board with the photosensitive resin composition of the present invention to form an insulating protective film (for example, a solder resist film, etc.) will be described.

The photosensitive resin composition obtained as described above is screen-printed, for example, on a printed wiring board (printed wiring board having a rigid board or a flexible board) having a circuit pattern formed by etching copper foil. The coating is applied to a desired thickness using a known coating method such as a spray coater, bar coater, applicator, blade coater, knife coater, roll coater, or gravure coater. Next, the applied photosensitive resin composition is subjected to an exposure treatment in which active energy rays (e.g., laser light) are directly irradiated in a desired pattern using a direct drawing device, and the photosensitive resin composition is applied in the pattern. Photocure the film. The exposure amount is, for example, 50 mJ/cm ² to 2000 mJ/cm ² . The coating is then developed by removing the unexposed areas with a dilute aqueous alkaline solution. The above-mentioned developing method includes, for example, a spray method, a shower method, etc., and the dilute alkali aqueous solution includes, for example, a 0.5 to 5% by mass aqueous sodium carbonate solution. Next, the developed coating film is thermally cured by performing post-curing (thermal curing treatment) for 20 to 80 minutes in a hot air circulation dryer at 130 to 170°C, and is photocured to form the desired pattern. A film (photocured material) can be formed on a printed wiring board.

In addition, instead of the above-mentioned exposure treatment in which active energy rays are directly irradiated according to a desired pattern using a direct drawing device, after coating the photosensitive resin composition, a temperature of about 60 to 100 ° C. A negative film (photomask) having a pattern in which areas other than the lands of the circuit pattern are made translucent is adhered to the tack-free coating film that has been pre-dried by heating for about 60 minutes, and active energy rays (e.g. , ultraviolet rays having a wavelength of 300 to 400 nm) may be applied to photocure the coating film.

Examples 1 to 12, Comparative Examples 1 to 5
The components shown in Table 1 below were blended in the proportions shown in Table 1 below, and mixed at room temperature using a three-roll roll to produce photosensitive resins used in Examples 1 to 12 and Comparative Examples 1 to 5. A composition was prepared. Thereafter, the prepared photosensitive resin composition was applied to a substrate as follows to prepare a test body. The blending amount of each component shown in Table 1 below indicates parts by mass unless otherwise specified. In addition, the blank space of the blending amount in Table 1 below means that it is not blended.

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 having a glycidyl methacrylate-modified cresol novolak structure, solid content (resin content) 65% by mass, Showa Denko K.K.・ZCR-1601H: Polybasic acid-modified unsaturated monocarboxylic oxidized epoxy resin with bisphenol novolak structure, solid content (resin content) 65% by mass, Nippon Kayaku Co., Ltd. ・ZFR-1887: Polybasic acid-modified unsaturated monocarboxylic acid epoxy resin Oxidized epoxy resin, solid content (resin content) 65% by mass, Nippon Kayaku Co., Ltd.

(B) Inorganic filler・FG-20: Untreated talc, D50 is 2.0 μm, Nippon Talc Co., Ltd.・FG-15: Untreated talc, D50 is 1.5 μm, Nippon Talc Co., Ltd.・SG-95: Untreated Talc, D50 is 2.1 μm, Nippon Talc Co., Ltd. SG-2000: Untreated talc, D50 is 0.9 μm, Nippon Talc Co., Ltd. FH-105: Untreated talc, D50 is 5.0 μm, Fuji Talc Kogyo Co., Ltd. Surface treated product with 3% epoxy silane from Nippon Talc Co., Ltd., FG-20: Surface treated talc surface treated to contain 3% by mass of epoxy functional silane compound, D50 is 2.5 μm, Nippon Talc Co., Ltd., FG-20. 5% acrylic silane surface treated product: Surface treated talc surface treated to contain 5% by mass of acrylic silane compound, D50 is 3.0 μm, Nippon Talc Co., Ltd.

(C) Photopolymerization initiator/Omnirad379: IGM Resins B. V. company

(D) Reactive diluent/KAYARAD DPCA-20: Nippon Kayaku Co., Ltd.

(E) Epoxy compound ・YX-4000: Biphenyl type epoxy resin, Mitsubishi Chemical Corporation ・N-695: Cresol novolac type epoxy resin, DIC Corporation

Colorant/carbon black: Toyo Ink Mfg. Co., Ltd. Additive/DICY-7: Mitsubishi Chemical Co., Ltd./U-CAT 3513N: Sun-Apro Co., Ltd./Melamine: Nissan Chemical Industries, Ltd. Antifoaming agent/AC-2300C: Shin-Etsu Chemical Co., Ltd. Co., Ltd. Flame retardant/Exorit OP-935: Aluminum tris-diethylphosphinate, Clariant Japan Co., Ltd./Aluminum hydroxide non-reactive diluent/EDGAC: Sanyo Kasei Co., Ltd.

Inorganic filler other than talc - B-30: Barium sulfate, D50 is 0.1 to 0.2 μm, Sakai Chemical Industry Co., Ltd. SO-C2: Silica, D50 is 0.5 μm, Admatex Co., Ltd. Minucil 5 micron: D50 is 5 μm, Air Brown Co., Ltd. Organic filler/urethane beads: D50 is 3.5 μm, Dainichiseika Co., Ltd.

Test Body Preparation Step The photosensitive resin compositions of Examples and Comparative Examples prepared as described above were applied onto a substrate in the following manner to produce a test body having a cured coating film on the substrate.
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: Oven at 80℃ for 20 minutes DRY film thickness (20±3μm)
Exposure: 100 mJ/cm ² on the coating film, exposure device: Direct writing (DI) exposure device “Nuvogo1000R” manufactured by Orbotech (light source: laser)
Post cure (thermal curing treatment): 150℃ in oven for 60 minutes

Evaluation items (1) Flux resistance A frame made of polyimide tape laminated (thickness 150 μm) was installed in a pattern with openings in the cured coating film on Cu foil, the inside of the frame was filled with rosin-based flux, and the lid was closed. Then, reflow was performed using a reflow oven (product name: TNP-538EM, manufactured by Tamura Seisakusho Co., Ltd.) under the conditions of a preheat temperature of 150° C. to 180° C. for 80 seconds and a peak temperature of 240° C. for 40 seconds. After reflow, the lid was removed, and the condition of the cured coating film was visually observed and evaluated as follows. A rating of △ or above was judged as passing.
◎: There is no peeling or blistering in the cured coating film, and there is no abnormality on the surface of the cured coating film.
○: There is no peeling or blistering in the cured coating, but there are stains on the surface of the cured coating.
△: There is some peeling and blistering in the cured coating film.
×: Significant peeling and blistering in the cured coating film.

(2) Gloss value (matte appearance)
The 60 degree specular reflectance (%) of the cured coating surface of the test piece was measured using a gloss meter VG-2000 (Nippon Denshoku Industries Co., Ltd.). A gloss value of 30% or less was considered to have a matte appearance and was judged to be acceptable.

(3) Flexibility The test specimen on which the cured coating film was formed was bent by a mandrel test, and the occurrence of cracks in the cured coating film at that time was observed visually and with a ×200 optical microscope to determine whether or not cracks had occurred. evaluated. A rating of △ or above was judged as passing.
◎: No cracks occurred even after bending 10 times with a diameter of 2 mm.
○: No cracks occur even after bending once with a diameter of 2 mm, and cracks occur after bending 10 times.
△: Cracks occurred when bending once with φ2 mm, and no cracks occurred when bending once with φ3 mm.
×: Cracks occurred when bent once with a diameter of 3 mm.

(4) Insulation reliability According to the above test body manufacturing process, a test body was manufactured using interdigitated electrodes (line width/space = 30 μm/30 μm) instead of the two-layer FCCL substrate, and using a HAST device, 110°C, 85%R. H. The insulation resistance after humidifying for 24 hours was measured by applying DC 32V. The criteria for evaluation are as follows, and a rating of △ or higher was determined to be a pass.
◎: Insulation resistance value is 1.0×10 ⁹ Ω or more.
○: Insulation resistance value is 1.0×10 ⁸ Ω or more and less than 1.0×10 ⁹ Ω.
Δ: Insulation resistance value is 1.0×10 ⁷ Ω or more and less than 1.0×10 ⁸ Ω.
×: Insulation resistance value is less than 1.0×10 ⁷ Ω.

The evaluation results are shown in Table 1 below.

As shown in Table 1 above, Examples 1 to 12 in which the inorganic filler is talc with a D50 of 0.7 μm or more and 5.5 μm or less have insulation reliability, flux resistance, matte appearance, and flexibility. A protective film with excellent properties was formed.

In particular, Examples 1, 4, and 5 in which the inorganic filler is talc with a D50 of 1.3 μm or more and 2.3 μm or less, Example 6 in which the inorganic filler is talc with a D50 of 0.9 μm and 5.0 μm, Compared to No. 7, flux resistance, matte appearance, and flexibility could be improved in a well-balanced manner. Further, in Example 1, in which about 50 parts by mass of talc with a D50 of 0.7 μm or more and 5.5 μm or less is blended with 100 parts by mass of the carboxyl group-containing photosensitive resin, talc with a D50 of 0.7 μm or more and 5.5 μm or less is used. The flux resistance and matte appearance were further improved compared to Example 2, in which approximately 20 parts by mass of the following were blended. In addition, Example 1 in which the carboxyl group-containing photosensitive resin has a cresol novolak type epoxy resin skeleton has higher insulation reliability than Examples 8 and 9 in which the carboxyl group-containing photosensitive resin does not have a cresol novolac type epoxy resin skeleton. and flux resistance has been further improved.

In Example 3, in which urethane beads were further blended as an organic filler, the flux resistance was slightly lower than in Example 1, but the flexibility was further improved. Furthermore, in Examples 10 and 11 in which surface-treated talc was used, insulation reliability, matte appearance, and flexibility were definitely improved, and especially in Example 11, in which surface-treated talc was surface-treated with an acrylic silane compound. , excellent flux resistance was obtained. Further, in Example 12, in which surface-treated talc was used and urethane beads were further blended as an organic filler, flexibility was improved while maintaining flux resistance, matte appearance, and insulation reliability.

On the other hand, in Comparative Example 1 in which the inorganic filler was barium sulfate with a D50 of 0.1 to 0.2 μm, flexibility and matte appearance could not be obtained. In Comparative Example 2, in which the inorganic filler was silica with a D50 of 0.5 μm, a matte appearance was not obtained. In Comparative Example 3, in which the inorganic filler was silica rather than talc even though D50 was 5 μm, flexibility and insulation reliability could not be obtained. Even though the D50 was 3.5 μm, in Comparative Example 4 in which urethane beads, which are organic fillers instead of inorganic fillers, were blended, flux resistance and insulation reliability could not be obtained. In Comparative Example 5, in which neither inorganic filler nor organic filler was blended, a matte appearance was not obtained.

The photosensitive resin composition of the present invention can form a protective film with excellent insulation reliability, flux resistance, matte appearance, and flexibility, so it can be used in the field of insulation protective films provided on printed wiring boards using flexible substrates. Highly useful.

Claims (15)

(A) a carboxyl group-containing photosensitive resin, (B) an inorganic filler, (C) a photopolymerization initiator, (D) a reactive diluent, and (E) an epoxy compound,
The inorganic filler (B) is talc with a cumulative volume percentage of 50 volume % and a particle diameter D50 of 0.7 μm or more and 5.5 μm or less,
A photosensitive resin in which the photopolymerization initiator (C) contains at least one selected from the group consisting of (C1) an α-aminoalkylphenone photopolymerization initiator and (C2) an oxime ester photopolymerization initiator. Composition. 2. The inorganic filler (B) is untreated talc that is not surface-treated with an organic compound and has a particle diameter D50 of 0.7 μm or more and 5.5 μm or less at a cumulative volume percentage of 50 volume %. Photosensitive resin composition. The photosensitive resin composition according to claim 2, wherein the inorganic filler (B) is the untreated talc having a cumulative volume percentage of 50% by volume and a particle diameter D50 of 1.3 μm or more and 2.3 μm or less. 2. The inorganic filler (B) is surface-treated talc that has been surface-treated with an organic compound and has a particle diameter D50 of 0.7 μm or more and 5.5 μm or less at a cumulative volume percentage of 50 volume %. Photosensitive resin composition. The photosensitive resin composition according to claim 4, wherein the inorganic filler (B) is the surface-treated talc having a cumulative volume percentage of 50% by volume and a particle diameter D50 of 2.0 μm or more and 4.0 μm or less. The photosensitive resin composition according to claim 4 or 5, wherein the organic compound is at least one selected from the group consisting of epoxysilane compounds and (meth)acrylic silane compounds. The photosensitive resin composition according to claim 1, wherein the talc is contained in an amount of 8 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin (A). The photosensitive resin composition according to claim 1, wherein the talc is contained in a range of 30 parts by mass to 70 parts by mass, based on 100 parts by mass of the carboxyl group-containing photosensitive resin (A). The photosensitive resin composition according to claim 1, which does not contain an organic filler. The photosensitive resin composition according to claim 1, further comprising an organic filler. The photosensitive resin composition according to claim 1, wherein the carboxyl group-containing photosensitive resin (A) has a cresol novolac type epoxy resin skeleton. Claim 1 wherein the (C1) α-aminoalkylphenone photopolymerization initiator contains 1-(4-morpholinophenyl)-2-(dimethylamino)-2-(4-methylbenzyl)-1-butanone. The photosensitive resin composition described in . The oxime ester photopolymerization initiator (C2) is (9-ethyl-6-nitro-9H-carbazol-3-yl)(4-((1-methoxypropan-2-yl)oxy)-2-methyl The photosensitive resin composition according to claim 1, containing O-acetyloxime (phenyl)methanone. A photocured product of the photosensitive resin composition according to claim 1. A printed wiring board comprising a photocured film of the photosensitive resin composition according to claim 1.