JP2023129708A - Black photosensitive resin composition, cured product of the same, and rigid flexible printed wiring board - Google Patents

Abstract

To provide a black photosensitive resin composition having excellent dispersibility and giving a cured coating film excellent in a concealing property, and to provide a black photosensitive resin composition having excellent low-temperature storage property and developability and a small optimal exposure light quantity and giving a cured coating film excellent in surface conditions, heat resistance and flexibility.SOLUTION: The black photosensitive resin composition in accordance with the present invention comprises a carboxyl group-containing resin having a bisphenol A structure, a thermosetting resin, a photosensitive monomer, a colorant and a photopolymerization initiator, in which the colorant comprises a red colorant, a blue colorant and a black colorant, and a compounding amount of the black colorant is 0.01 pts.mass or more and less than 1 pts.mass in terms of a solid content with respect to 100 pts.mass of the carboxyl group-containing resin.SELECTED DRAWING: None

Description

The present invention relates to a black photosensitive resin composition and a cured product thereof, and particularly to a black photosensitive resin composition and a cured product thereof that are suitably used as a black solder resist. The present invention also relates to a printed wiring board including a black solder resist layer made of the cured product.

Conventionally, electronic devices such as smartphones and personal computers have used printed wiring boards equipped with electronic elements having various functions. Printed wiring boards have been made using a material called rigid substrates, but as electronic devices become smaller and more functional, the space to store printed wiring boards in electronic devices has become narrower. .

As a countermeasure against this problem, a flexible printed wiring board (FPC), which is a printed wiring board that can be warped and bent, has been adopted. Conventional FPCs were mainly used for the purpose of connecting rigid substrates, but as electronic devices become more sophisticated, it has become necessary to mount more electronic elements. Therefore, a rigid-flexible printed wiring board (RFPC) was devised as an FPC on which components can be mounted.

Furthermore, in order to mount components, the printed wiring board undergoes a process such as solder reflow, so it is necessary to form a solder resist (SR) to protect the printed wiring board from the heat generated during that process. Conventional SR for rigid substrates has high heat resistance, but flexibility is not required because the rigid substrate itself is rigid. Furthermore, since the main purpose of FPC is to connect rigid boards to each other, SR for FPC requires flexibility but does not require high heat resistance. Furthermore, from the viewpoint of concealability and design, a black SR layer has been formed. Conventionally, carbon black has been used as a coloring agent in the above-mentioned black solder resist (see, for example, Patent Document 1). Furthermore, in recent years, there has been a demand for high resolution, and instead of carbon black, composite black, which is a mixture of pigments of multiple colors other than black, has been attracting attention (for example, see Patent Document 2).

Japanese Patent Application Publication No. 2008-257045 Japanese Patent Application Publication No. 2010-091876

Solder resists used for RFPCs are required to have the heat resistance of solder resists for rigid boards and the flexibility of solder resists for FPCs, but conventional SRs for rigid boards lack flexibility, while solder resists for FPCs had poor heat resistance. Furthermore, it has been difficult to develop a black photosensitive resin composition that has a black appearance as a cured coating, has high sensitivity, and does not generate foreign matter such as discoloration or recrystallization at low temperatures. Therefore, there is a strong desire to develop a black photosensitive resin composition that has both the heat resistance of a solder resist for rigid substrates and the flexibility of a solder resist for FPC.

In addition, resin compositions such as commonly used solder resist inks contain resin components and powder components, but if colorants and fillers are not uniformly dispersed, leveling will occur during screen printing. This is difficult because there is a possibility of surface defects in the cured coating. Furthermore, it is conceivable that the adhesion with the substrate may deteriorate and the characteristics of a cured coating film may not be obtained. This tendency is particularly noticeable when a red colorant is used, and improvement has been desired in consideration of the surface condition and properties of the subsequent coating film.

Therefore, an object of the present invention is to provide a black photosensitive resin composition that has excellent dispersibility and hiding properties of the obtained cured coating film. Another object of the present invention is to provide a black photosensitive resin composition that has excellent low-temperature storage stability and developability, has a small optimum exposure dose, and provides a cured coating film that is excellent in surface condition, heat resistance, and flexibility. Another object of the present invention is to provide a rigid-flexible printed wiring board including a black solder resist layer made of a cured product formed using the photosensitive resin composition.

The present inventors have proposed a photosensitive resin composition containing a carboxyl group-containing resin having a specific structure, a thermosetting resin, a photosensitive monomer, a coloring agent, and a photopolymerization initiator. It has been found that the above problems can be solved by using a blue colorant and a small amount of a black colorant. The present invention is based on this knowledge.

That is, the black photosensitive resin composition according to the present invention contains a carboxyl group-containing resin having a bisphenol A structure, a thermosetting resin, a photosensitive monomer, a coloring agent, and a photopolymerization initiator, and the coloring agent is red colored. a blue colorant, and a black colorant, the amount of the black colorant being 0.01 part by mass or more and less than 1 part by mass, based on 100 parts by mass of the carboxyl group-containing resin, in terms of solid content. It is characterized by a certain thing.

In embodiments of the present invention, it is preferred that the composition is substantially free of yellow colorant.

In the aspect of the present invention, it is preferable that the amount of the yellow coloring agent blended is 2 parts by mass or less with respect to 100 parts by mass of the carboxyl group-containing resin.

In the aspect of the present invention, it is preferable that the black photosensitive resin composition further contains a phosphorus element-containing (meth)acrylate oligomer.

In an aspect of the present invention, the black photosensitive resin composition is preferably used for forming a black solder resist.

A cured product according to another aspect of the present invention is characterized in that it is obtained by curing the above black photosensitive resin composition.

A rigid-flexible printed wiring board according to another aspect of the present invention is characterized by having the above-mentioned cured product.

According to the present invention, the leveling property can be improved in screen printing due to excellent dispersibility, and the obtained cured coating film can provide a black photosensitive resin composition with excellent hiding properties.
In addition, according to the present invention, in terms of properties other than those mentioned above, it has excellent low-temperature storage stability and developability, has a small optimum exposure dose, and the resulting cured coating has a black color with excellent surface condition, heat resistance, and flexibility. A photosensitive resin composition can be provided. Furthermore, according to another embodiment of the present invention, it is possible to provide a printed wiring board including a black solder resist layer made of a cured product made of the black photosensitive resin composition.

The black photosensitive resin composition of the present invention will be explained below. In addition, unless otherwise specified, in this specification, a numerical range expressed using the symbol "~" is a range that includes the upper and lower numerical limits (i.e., a range that is greater than or equal to the lower limit and less than or equal to the upper limit). means.

[Black photosensitive resin composition]
The black photosensitive resin composition according to the present invention contains at least a carboxyl group-containing resin having a bisphenol A structure, a thermosetting resin, a photosensitive monomer (reactive diluent), a coloring agent, and a photopolymerization initiator. Other components such as elemental (meth)acrylate oligomers, curing catalysts, fillers, and flame retardants may also be included. By using a carboxyl group-containing resin and a thermosetting resin together, properties such as heat resistance and insulation reliability can be improved. Each component constituting the black photosensitive resin composition according to the present invention will be explained below.

[Carboxyl group-containing resin having bisphenol A structure]
As the carboxyl group-containing resin having a bisphenol A structure, various conventionally known resins having a bisphenol A structure and a carboxyl group in the molecule can be used. When the carboxyl group-containing resin has a bisphenol A structure, flexibility and soldering heat resistance are improved. When the black photosensitive resin composition contains a resin having a carboxyl group, alkaline developability can be imparted to the black photosensitive resin composition. In particular, a carboxyl group-containing photosensitive resin having an ethylenically unsaturated double bond in its molecule is preferred from the viewpoint of photocurability and development resistance. Preferably, the ethylenically unsaturated double bond is derived from acrylic acid or methacrylic acid or derivatives thereof. When only a carboxyl group-containing resin having no ethylenically unsaturated double bond is used, the composition is made photosensitive by using in combination with a photosensitive monomer described below. In the present invention, bisphenol A also includes hydrogenated bisphenol A. Specific examples of carboxyl group-containing resins having a bisphenol A structure include the following compounds (which may be either oligomers or polymers).

(1) A carboxyl group-containing photosensitive urethane resin produced by a polyaddition reaction between a diisocyanate, (meth)acrylate of bisphenol A type epoxy resin or its partially modified acid anhydride, a carboxyl group-containing dialcohol compound, and a diol compound.

(2) During the synthesis of the resin in (1) above, a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as hydroxyalkyl (meth)acrylate, is added to form a terminal (meth)acrylate. A photosensitive urethane resin containing carboxyl groups.

(3) During the synthesis of the resin in (1) above, a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule, such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate, is added. A photosensitive urethane resin containing carboxyl groups with terminal (meth)acrylation.

(4) Bisphenol A type epoxy resin A carboxyl group-containing photosensitive resin obtained by reacting an epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride to the hydroxyl group present in the side chain.

(5) Bisphenol A epoxy resin A carboxyl product obtained by reacting (meth)acrylic acid with a polyfunctional epoxy resin in which the hydroxyl groups of the epoxy resin are further epoxidized with epichlorohydrin, and adding a dibasic acid anhydride to the resulting hydroxyl groups. Group-containing photosensitive resin.

(6) A carboxyl group-containing photosensitive resin obtained by adding a compound having one epoxy group and one or more (meth)acryloyl groups in one molecule to the resins (1) to (5) above.
Note that in this specification, (meth)acrylate is a term that collectively refers to acrylate, methacrylate, and mixtures thereof, and the same applies to other similar expressions.

The acid value of the carboxyl group-containing resin having a bisphenol A structure is preferably 40 to 150 mgKOH/g. When the acid value of the carboxyl group-containing resin having a bisphenol A structure is 40 mgKOH/g or more, alkaline development becomes good. Further, by setting the acid value to 150 mgKOH/g or less, it is possible to easily draw a good resist pattern. More preferably, it is 50 to 130 mgKOH/g.

The weight average molecular weight of the carboxyl group-containing resin having a bisphenol A structure varies depending on the resin skeleton, but is generally preferably from 2,000 to 150,000. By setting the weight average molecular weight to 2,000 or more, tack-free performance and resolution can be improved. Further, by setting the weight average molecular weight to 150,000 or less, developability and storage stability can be improved. More preferably, it is 5,000 to 100,000.

The amount of the carboxyl group-containing resin having a bisphenol A structure in the black photosensitive resin composition is preferably 20 to 60% by mass in terms of solid content. By setting the content to 20% by mass or more, the strength of the cured coating film can be improved. Further, by setting the content to 60% by mass or less, the viscosity becomes appropriate and printability improves. More preferably, it is 30 to 50% by mass.

[Carboxyl group-containing resin having other structures]
The black photosensitive resin composition according to the present invention may further contain carboxyl group-containing resins having other structures as long as it contains one or more carboxyl group-containing resins having a bisphenol A structure. Other structures include a phenol novolak structure, a cresol novolak structure, and a bisphenol F structure.

[Photosensitive monomer]
The black photosensitive resin composition of the present invention contains a photosensitive monomer. A photosensitive monomer is a compound having an ethylenically unsaturated double bond. Examples of the photosensitive monomer include commonly known polyester (meth)acrylate, polyether (meth)acrylate, urethane (meth)acrylate, carbonate (meth)acrylate, and epoxy (meth)acrylate. Specifically, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; glycol diacrylates such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; N,N-dimethylacrylamide , N-methylol acrylamide, N,N-dimethylaminopropylacrylamide, and other acrylamides; N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropyl acrylate, and other aminoalkyl acrylates; hexanediol, trimethylolpropane, Polyhydric alcohols such as pentaerythritol, dipentaerythritol, tris-hydroxyethyl isocyanurate, or polyhydric acrylates such as their ethylene oxide adducts, propylene oxide adducts, or ε-caprolactone adducts; phenoxy acrylate, bisphenol A di Acrylates and polyhydric acrylates such as ethylene oxide adducts or propylene oxide adducts of these phenols; Polyhydric acrylates; not limited to the above, acrylates and melamine acrylates obtained by directly acrylating polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadienes, and polyester polyols, or converting them into urethane acrylates via diisocyanates, and the above-mentioned acrylates. At least one of the methacrylates corresponding to the above can be appropriately selected and used. Such photosensitive monomers can also be used as reactive diluents.

Epoxy acrylate resins are made by reacting acrylic acid with multifunctional epoxy resins such as cresol novolac type epoxy resins, and half urethanes are made of hydroxy acrylates such as pentaerythritol triacrylate and diisocyanates such as isophorone diisocyanate. An epoxyurethane acrylate compound or the like obtained by reacting a compound may be used as the photosensitive monomer. Such an epoxy acrylate resin can improve photocurability without reducing dryness to the touch.

The amount of the photosensitive monomer to be blended in the black photosensitive resin composition is preferably 0.2 to 60 parts by weight, more preferably 0.2 to 60 parts by weight, based on 100 parts by weight of the carboxyl group-containing resin having a bisphenol A structure, in terms of solid content. The amount is 0.2 to 50 parts by mass. By setting the blending amount of the photosensitive monomer to 0.2 parts by mass or more, the photocurability of the black photosensitive resin composition is improved. Moreover, by setting the blending amount to 60 parts by mass or less, the hardness of the cured coating film can be improved.

Especially when using a carboxyl group-containing non-photosensitive resin that does not have ethylenically unsaturated double bonds, it is necessary to use a photosensitive monomer in combination to make the composition photocurable. It is valid.

[Thermosetting resin]
The thermosetting resin used in the present invention includes known and commonly used resins such as isocyanate compounds, blocked isocyanate compounds, amino resins, maleimide compounds, benzoxazine resins, carbodiimide resins, cyclocarbonate compounds, epoxy compounds, oxetane compounds, and episulfide resins. can be mentioned. Among these, a preferable thermosetting resin is an epoxy resin.

Epoxy resins that can be used include, for example, bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, brominated bisphenol A epoxy resin, bisphenol S epoxy resin, and phenol novolac epoxy. resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, and the like. These epoxy resins may be used alone or in combination of two or more.

Commercially available epoxy resins include, for example, jER 828, 806, 807, YX8000, 8034, 834 manufactured by Mitsubishi Chemical Corporation, YD-128, YDF-170, ZX-1059 manufactured by Nippon Steel Chemical & Materials Corporation, ST-3000, EPICLON 830, 835, 840, 850, N730A, N695 manufactured by DIC Corporation, and RE-306 manufactured by Nippon Kayaku Corporation.

The equivalent weight of the epoxy group of the epoxy resin in the black photosensitive resin composition should be 0.3 to 3.0 per equivalent weight of the carboxyl group of the carboxyl group-containing resin having a bisphenol A structure in terms of solid content. is preferred. By setting the amount to 0.3 equivalent or more, it is possible to prevent carboxyl groups from remaining in the cured film and obtain good heat resistance, alkali resistance, electrical insulation, etc. On the other hand, by setting the above blending amount to 3.0 equivalents or less, it is possible to prevent the low molecular weight cyclic (thio)ether group from remaining in the dried coating film and ensure good strength etc. of the cured film. can.

[Thermosetting catalyst]
A thermosetting catalyst can be blended into the black photosensitive resin composition of the present invention. Examples of the thermosetting catalyst include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1- Imidazole derivatives such as (2-cyanoethyl)-2-ethyl-4-methylimidazole; dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzyl Examples include amines, amine compounds such as 4-methyl-N,N-dimethylbenzylamine, hydrazine compounds such as adipic acid dihydrazide and sebacic acid dihydrazide; and phosphorus compounds such as triphenylphosphine. Also, guanamine, acetoguanamine, benzoguanamine, melamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino S-triazine derivatives such as -S-triazine/isocyanuric acid adduct and 2,4-diamino-6-methacryloyloxyethyl-S-triazine/isocyanuric acid adduct can also be used.

When the composition contains a thermosetting component having a cyclic (thio)ether group in the molecule, such as an epoxy resin, the blending amount of the thermosetting catalyst is determined based on the solid content. The amount is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15.0 parts by weight, based on 100 parts by weight of the thermosetting component.

[Colorant]
The black photosensitive resin composition of the present invention contains at least a red colorant, a blue colorant, and a black colorant as colorants, and the amount of the black colorant has a bisphenol A structure in terms of solid content. It is characterized in that the amount is 0.01 part by mass or more and less than 1 part by mass with respect to 100 parts by mass of the carboxyl group-containing resin. As the coloring agent, any of pigments, dyes, and pigments can be used. However, it is preferable not to contain halogen from the viewpoint of reducing environmental load and affecting the human body.

As the red colorant in the black photosensitive resin composition of the present invention, known and commonly used colorants can be used. For example, there are monoazo series, disazo series, azo lake series, benzimidazolone series, perylene series, diketopyrrolopyrrole series, condensed azo series, anthraquinone series, quinacridone series, etc. Specifically, the color index ( C.I.; published by The Society of Dyers and Colorists). Examples of monoazo red colorants include Pigment Red 1, 2, 3, 4, 5, 6, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 112, 114, 146, 147, 151, 170, 184, 187, 188, 193, 210, 245, 253, 258, 266, 267, 268, 269 and the like. Further, examples of the disazo red coloring agent include Pigment Red 37, 38, and 41. In addition, as monoazo lake red colorants, Pigment Red 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 50:1, 52:1, 52:2, 53: Examples include 1,53:2, 57:1, 58:4, 63:1, 63:2, 64:1, 68, and the like. Further, examples of the benzimidazolone red colorant include Pigment Red 171, 175, 176, 185, and 208. Examples of perylene-based red colorants include Solvent Red 135, 179, Pigment Red 123, 149, 166, 178, 179, 190, 194, 224, and the like. Further, examples of the diketopyrrolopyrrole red colorant include Pigment Red 254, 255, 264, 270, 272, and the like. Further, examples of condensed azo red colorants include Pigment Red 220, 144, 166, 214, 220, 221, 242, and the like. Further, examples of the anthraquinone red colorant include Pigment Red 168, 177, 216, Solvent Red 149, 150, 52, 207, and the like. In addition, examples of the quinacridone-based red colorant include Pigment Red 122, 202, 206, 207, and 209.

The amount of the red colorant to be blended in the black photosensitive resin composition is preferably 0.1 to 10 parts by mass based on 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure, in terms of solid content, and more preferably The amount is preferably 0.5 to 7 parts by weight, more preferably 1 to 5 parts by weight.

As the blue colorant in the black photosensitive resin composition of the present invention, known and commonly used colorants can be used. For example, there are phthalocyanine-based and anthraquinone-based compounds, and pigment-based compounds include compounds classified as pigments. For example, Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 60. As the dye system, Solvent Blue 35, 63, 68, 70, 83, 87, 94, 97, 122, 136, 67, 70, etc. can be used. In addition to the above, metal-substituted or unsubstituted phthalocyanine compounds can also be used.

The amount of the blue colorant to be blended in the black photosensitive resin composition is preferably 0.1 to 10 parts by mass based on 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure, in terms of solid content, and more preferably The amount is preferably 0.5 to 7 parts by weight, more preferably 2 to 6 parts by weight.

The black photosensitive resin composition in the present invention contains a black colorant, and the amount of the black colorant is, in terms of solid content, relative to 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure. The resin composition is characterized in that it is contained in an amount of 0.01 part by mass or more and less than 1 part by mass, in terms of solid content, per 100 parts by mass of the carboxyl group-containing resin. Further, it is preferably 0.05 to 0.7 parts by mass. As a result of intensive research, the present inventor has found that even if a colorant with poor dispersibility, such as a red colorant, is used, the dispersibility can be significantly improved by adding a small amount of a black colorant within the above range. I found out what to do. Although the reason is not clear, it is assumed as follows. That is, a certain degree of fluidity is required in order for the dye, which is the material of the colorant, to be absorbed into the resin composition, and a black colorant with low viscosity and fine particles is suitable. However, this is still in the realm of speculation and nothing more can be done.
Examples of the black colorant include inorganic pigments such as carbon black, triiron tetroxide, black titanium oxide, copper manganese black, copper chromium black, and cobalt black, and organic pigments such as cyanine black and aniline black. Among these, it is preferable to use carbon black due to its handling safety and stability.

Examples of the yellow coloring agent in the black photosensitive resin composition of the present invention include monoazo, disazo, condensed azo, benzimidazolone, isoindolinone, and anthraquinone. For example, examples of the anthraquinone yellow coloring agent include Solvent Yellow 163, Pigment Yellow 24, 108, 193, 147, 199, and 202. Examples of the isoindolinone yellow colorant include Pigment Yellow 110, 109, 139, 179, 185, and the like. Examples of condensed azo yellow colorants include Pigment Yellow 93, 94, 95, 128, 155, 166, 180, and the like. Examples of the benzimidazolone yellow colorant include Pigment Yellow 120, 151, 154, 156, 175, 181, and the like. In addition, as the monoazo yellow colorant, Pigment Yellow 1, 2, 3, 4, 5, 6, 9, 10, 12, 61, 62, 62:1, 65, 73, 74, 75, 97, 100, 104, 105, 111, 116, 167, 168, 169, 182, 183 and the like. In addition, examples of the disazo yellow colorant include Pigment Yellow 12, 13, 14, 16, 17, 55, 63, 81, 83, 87, 126, 127, 152, 170, 172, 174, 176, 188, 198, etc. can be mentioned.

It is preferable that the black photosensitive resin composition of the present invention does not substantially contain a yellow colorant. In the present specification, "substantially not contained" means that the blended amount is 2 parts by mass per 100 parts by mass of carboxyl group-containing resin having a bisphenol A structure in terms of solid content in the black photosensitive resin composition. It means below 100%. The yellow coloring agent tends to crystallize, creating a yellow spot pattern on the black solder resist layer, which may affect the appearance and cause the product to be judged as a foreign substance or a defective product. Therefore, by reducing the blending amount of the yellow colorant in the black photosensitive resin composition, adverse effects on the appearance can be suppressed. The content of the yellow colorant is preferably 1 part by mass or less, more preferably 0.1 part by mass or less.

In addition, coloring agents such as purple, orange, brown, and white may be added. Specifically, Pigment Black 1, 6, 7, 8, 9, 10, 11, 12, 13, 18, 20, 25, 26, 28, 29, 30, 31, 32, Pigment Violet 19, 23, 29 , 32, 36, 38, 42, Solvent Violet 13, 36, C. I. Pigment Orange 1, 5, 13, 14, 16, 17, 24, 34, 36, 38, 40, 43, 46, 49, 51, 61, 63, 64, 71, 73, Pigment Brown 23, 25, titanium oxide, etc. can be mentioned.

[Photopolymerization initiator]
In the present invention, known photopolymerization initiators can be used to photopolymerize the black photosensitive resin composition described above, such as oxime ester photopolymerization initiators having an oxime ester group. Examples thereof include titanocene photopolymerization initiators, α-aminoacetophenone photopolymerization initiators, and acylphosphine oxide photopolymerization initiators. Among these, titanocene photopolymerization initiators, α-aminoacetophenone photopolymerization initiators, and acylphosphine oxide photopolymerization initiators are preferred, and combinations of titanocene photopolymerization initiators and α-aminoacetophenone photopolymerization initiators are preferred. is more preferable. One type of photopolymerization initiator may be used alone, or two or more types may be used in combination.

Specifically, the titanocene photopolymerization initiator is bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl). Examples thereof include titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyl-1-yl)ethyl)phenyl]titanium, and the like. Commercially available products include JMT784 manufactured by Yueyang Jin Maotai Technology Co., Ltd.

Specifically, the α-aminoacetophenone photopolymerization initiator includes 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1, 2-benzyl-2-dimethylamino-1 -(4-morpholinophenyl)-butan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, Examples include N,N-dimethylaminoacetophenone. Commercially available products include Omnirad 369, 369E, 379, and 907 manufactured by IGM Resins.

Examples of acylphosphine oxide photopolymerization initiators include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2, Examples include 6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide. Commercially available products include Omnirad TPO and 819 manufactured by IGM Resins.

The amount of the photopolymerization initiator in the photosensitive resin composition is preferably 0.5 to 10 parts by mass, in terms of solid content, per 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure. If the amount is 0.5 parts by mass or more, the photocurability of the resin composition will be good, the coating will be difficult to peel off, and the coating properties such as chemical resistance will also be good. On the other hand, when the amount is 10 parts by mass or less, an effect of reducing outgas is obtained, and furthermore, light absorption on the surface of the solder resist coating film becomes good, and deep curability is less likely to deteriorate. More preferably, it is 1 to 8 parts by mass.

A photoinitiation aid or sensitizer may be used in combination with the photopolymerization initiator described above. Examples of the photoinitiation aid or sensitizer include benzoin compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and xanthone compounds. In particular, it is preferable to use thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone. By including the thioxanthone compound, deep curability can be improved. Although these compounds can be used as a photopolymerization initiator in some cases, it is preferable to use them in combination with a photopolymerization initiator. Moreover, one type of photoinitiation aid or sensitizer may be used alone, or two or more types may be used in combination.

Note that these photopolymerization initiators, photoinitiation aids, and sensitizers absorb specific wavelengths, and therefore may have low sensitivity and function as ultraviolet absorbers in some cases. However, these are not used solely for the purpose of improving the sensitivity of the composition. If necessary, it absorbs light of a specific wavelength to increase the photoreactivity of the surface, change the line shape and aperture of the resist into vertical, tapered, and reverse tapered shapes, and improve the accuracy of line width and aperture diameter. can be improved.

[(meth)acrylate oligomer containing phosphorus element]
The black photosensitive resin composition of the present invention preferably contains a phosphorus element-containing (meth)acrylate oligomer in order to further improve flame retardancy. A phosphorus element-containing (meth)acrylate oligomer is a compound containing one or more (meth)acrylates in the molecule, which is obtained by reacting at least one phosphorus element-containing dicarboxylic acid and its anhydride with an acrylate compound. be.

Examples of phosphorus element-containing dicarboxylic acids and their anhydrides include, for example, compounds obtained by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with itaconic acid; Examples include anhydrides.

As an example of the acrylate compound, an acrylate compound having a carboxyl group or a functional group that reacts with the carboxylic acid anhydride of the dicarboxylic acid or its anhydride is preferable. Acrylate residues can be added by such reactions. Such an acrylate compound may be a monofunctional acrylate containing one (meth)acrylate group in the molecule, or a polyfunctional acrylate containing two or more (meth)acrylate groups in the molecule. Examples of the functional groups include epoxy groups, hydroxyl groups, amino groups, and the like. Examples of the acrylate compound having an epoxy group include glycidyl (meth)acrylate, 2-methyl-2,3-epoxypropyl (meth)acrylate, and the like. Examples of the acrylate compound having a hydroxyl group include 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate. Examples of the acrylate compound having an amino group include diethylaminoethyl acrylate and the like. Among the above functional groups, epoxy groups and hydroxyl groups are more preferred. A conventionally known reaction method can be used as the reaction method for addition with the above-mentioned functional group.

The weight average molecular weight of the phosphorus element-containing (meth)acrylate oligomer is preferably 1,500 to 4,500, more preferably 2,000 to 4,000. If the weight average molecular weight of the phosphorus element-containing (meth)acrylate oligomer is within the above range, tackiness and developability can be improved.

The blending amount of the phosphorus element-containing (meth)acrylate oligomer is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, based on 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure, in terms of solid content. Parts by weight, more preferably 30 to 70 parts by weight. When the amount of the phosphorus element-containing (meth)acrylate oligomer is within the above range, heat resistance and flame retardance can be improved.

[Flame retardants]
In order to further improve the flame retardance of the black photosensitive resin composition of the present invention, a flame retardant can be used in addition to the phosphorus element-containing (meth)acrylate oligomer. Examples of the flame retardant include aluminum hydroxide. The blending amount of the flame retardant is preferably 20 to 40 parts by mass, in terms of solid content, per 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure.

[Other ingredients]
If necessary, an inorganic filler can be further added to the black photosensitive resin composition for the purpose of improving properties such as adhesiveness, mechanical strength, and coefficient of linear expansion of the cured product. For example, known and commonly used inorganic fillers such as barium sulfate, barium titanate, silicon oxide powder, finely powdered silicon oxide, amorphous silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, and mica powder can be used.

The black photosensitive resin composition may further contain components such as an adhesion promoter, an antioxidant, an ultraviolet absorber, and a dispersant, if necessary. As these materials, those known in the field of electronic materials can be used. In addition, at least one of silicone-based, fluorine-based, polymer-based antifoaming agents and leveling agents, imidazole-based, thiazole-based, triazole-based silane coupling agents, rust preventive agents, optical brighteners, etc. At least one kind of known and commonly used additives such as the following may be blended.

In the present invention, an organic solvent can be used to prepare the black photosensitive resin composition and adjust the viscosity. Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum solvents, and the like. More specifically, for example, ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene Glycol ethers such as glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, triethylene glycol monoethyl ether; ethyl acetate, butyl acetate, dipropylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl Esters such as ether acetate, propylene glycol butyl ether acetate, diethylene glycol monoethyl ether acetate (carbitol acetate), diethylene glycol monobutyl ether acetate; alcohols such as ethanol, propanol, ethylene glycol, propylene glycol; aliphatic carbonization such as octane, decane, etc. Hydrogen: petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. Such organic solvents may be used alone or as a mixture of two or more.

[Application]
The black photosensitive resin composition according to the present invention is suitably used to form a cured product, particularly a cured coating film, in a printed wiring board. For example, it can be suitably used as a filling material for forming solder resists, interlayer insulation materials, marking inks, coverlays, solder dams, and filling holes in through holes and via holes of printed wiring boards and recesses. . Among these, it can be suitably used for forming a black solder resist, and particularly for forming a black solder resist layer of a rigid-flexible wiring board. Further, the black photosensitive resin composition according to the present invention may be one-component or two-component or more.

[Printed wiring board]
The printed wiring board of the present invention includes a black solder resist layer made of a cured product of the above black photosensitive resin composition. Since the black solder resist layer has flexibility, it can be suitably used as a rigid-flexible printed wiring board (RFPC).

The method for producing a printed wiring board of the present invention includes applying the above black photosensitive resin composition onto a substrate and curing it with at least one of light and heat to form a solder resist layer made of the cured product. It is something. An example of a method for forming a solder resist layer will be described below.

Black solder resist is produced by adjusting the viscosity of a black photosensitive resin composition to suit the coating method and applying it onto the circuit-formed circuit board by dip coating, flow coating, roll coating, bar coater, screen printing, etc. A tack-free dry coating film can be formed by coating the entire surface by a method such as a curtain coating method and drying (temporary drying) by volatilizing the organic solvent contained in the composition at a temperature of about 60 to 100°C. The film thickness after drying is preferably 30 to 50 μm. Thereafter, by contact method (or non-contact method), the exposed areas are selectively exposed to active energy rays through a patterned photomask, and the unexposed areas are exposed to dilute alkaline aqueous solution (for example, 0.3 to 3 mass% sodium carbonate aqueous solution). A resist pattern is formed by development. Furthermore, by heating to a temperature of about 140 to 180° C. for thermosetting, a cured coating film with excellent properties such as heat resistance, chemical resistance, moisture absorption resistance, adhesion, and electrical properties can be formed. I can do it.

The base materials used for the circuit-formed circuit board include paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth/nonwoven epoxy, glass cloth/paper epoxy, synthetic fiber epoxy, fluorine/polyethylene/PPO. - Copper-clad laminates of all grades (FR-4, etc.) using materials such as copper-clad laminates for high-frequency circuits using cyanate ester, etc., other polyimide films, PET films, glass substrates, ceramic substrates, Examples include wafer plates.

Further, as the irradiation light source used for active energy ray irradiation, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a metal halide lamp, etc. are suitable. In addition, laser beams can also be used as active energy rays.

The developing method may be a dipping method, a shower method, a spray method, a brush method, etc., and the developing solution may include potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, etc. Dilute alkaline aqueous solutions such as ammonia and amines can be used.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Synthesis example 1)
<Synthesis of carboxyl group-containing resin varnish 1>
371 parts of bisphenol A type epoxy resin (epoxy equivalent: 650 g/eq, softening point: 81.1°C) having the following general formula (I) where X is C(CH ₃ ) ₂ and the average degree of polymerization n is 3.3, and epichlorohydrin. After dissolving 925 parts in 462.5 parts of dimethyl sulfoxide, 52.8 parts of 98.5% NaOH was added over 100 minutes at 70°C with stirring. After the addition, the reaction was further carried out at 70°C for 3 hours. After the reaction was completed, 250 parts of water was added to wash with water. After oil and water separation, most of the dimethyl sulfoxide and excess unreacted epichlorohydrin were distilled and recovered from the oil layer under reduced pressure, and the reaction product containing the remaining by-product salt and dimethyl sulfoxide was dissolved in 750 parts of methyl isobutyl ketone, and further dissolved in 30% NaOH10. of the mixture was added, and the mixture was reacted at 70°C for 1 hour. After the reaction was completed, washing was performed twice with 200 parts of water. After oil and water separation, methyl isobutyl ketone was distilled and recovered from the oil layer to obtain an epoxy resin (a) having an epoxy equivalent of 287 g/eq and a softening point of 64.2°C. In the obtained epoxy resin (a), about 3.1 out of 3.3 alcoholic hydroxyl groups in the bisphenol A type epoxy resin as the starting material were epoxidized, as calculated from the epoxy equivalent. 310 parts of this epoxy resin (a) and 282 parts of carbitol acetate were placed in a flask, heated to 90°C and stirred to dissolve. The obtained solution was once cooled to 60°C, 72 parts (1 mol) of acrylic acid, 0.5 part of methylhydroquinone, and 2 parts of triphenylphosphine were added, heated to 100°C, and reacted for about 60 hours to remove the acid. A reactant having a value of 0.2 mgKOH/g was obtained. 140 parts (0.92 mol) of tetrahydrophthalic anhydride was added thereto, and the mixture was heated to 90°C to carry out a reaction to obtain carboxyl group-containing resin varnish 2. The solid content concentration of the obtained carboxyl group-containing resin varnish 1 was 62% by mass, and the solid content acid value (mgKOH/g) was 100.

(Synthesis example 2)
<Synthesis of carboxyl group-containing resin varnish 2>
380 parts of a bisphenol F type epoxy resin (epoxy equivalent: 950 g/eq, softening point: 85° C.) in the following general formula (I) where X is CH ₂ and the average degree of polymerization n is 6.2 and 925 parts of epichlorohydrin are added to 462 parts of dimethyl sulfoxide. After dissolving the solution in 0.5 parts, 60.9 parts of 98.5% NaOH was added over 100 minutes at 70° C. while stirring. After the addition, the reaction was further carried out at 70°C for 3 hours. After the reaction was completed, 250 parts of water was added to wash with water. After oil and water separation, most of the dimethyl sulfoxide and excess unreacted epichlorohydrin were distilled and recovered from the oil layer under reduced pressure, and the reaction product containing the remaining by-product salt and dimethyl sulfoxide was dissolved in 750 parts of methyl isobutyl ketone, and further dissolved in 30% NaOH10. of the mixture was added, and the mixture was reacted at 70°C for 1 hour. After the reaction was completed, washing was performed twice with 200 parts of water. After oil and water separation, methyl isobutyl ketone was distilled and recovered from the oil layer to obtain an epoxy resin (a) having an epoxy equivalent of 310 g/eq and a softening point of 69°C. In the obtained epoxy resin (a), as calculated from the epoxy equivalent, about 5 out of 6.2 alcoholic hydroxyl groups in the starting bisphenol F type epoxy resin were epoxidized. 310 parts of this epoxy resin (a) and 282 parts of carbitol acetate were placed in a flask, heated to 90°C and stirred to dissolve. The obtained solution was once cooled to 60°C, 72 parts (1 mol) of acrylic acid, 0.5 part of methylhydroquinone, and 2 parts of triphenylphosphine were added, heated to 100°C, and reacted for about 60 hours to remove the acid. A reactant having a value of 0.2 mgKOH/g was obtained. 140 parts (0.92 mol) of tetrahydrophthalic anhydride was added thereto, and the mixture was heated to 90°C to react, thereby obtaining carboxyl group-containing resin varnish 1. The solid content concentration of the obtained carboxyl group-containing resin varnish 2 was 62% by mass, and the solid content acid value (mgKOH/g) was 100.

(In the formula, X represents CH ₂ or C(CH ₃ ) ₂ , and n is 1 to 12.)

<Preparation of black photosensitive resin composition>
[Example 1]
Carboxyl group-containing resin, thermosetting resin, photosensitive monomer (reactive diluent), phosphorus element-containing (meth)acrylate oligomer, coloring agent, photopolymerization initiator, and flame retardant are shown in Table 1. Black photosensitive resin composition 1 was prepared by blending in the proportions shown (parts by mass), premixing with a stirrer, and then kneading with a three-roll mill. Note that the blending amount values in the table indicate parts by mass of solid content unless otherwise specified.

[Examples 2 to 5]
Black photosensitive resin compositions 2 to 5 were prepared in the same manner as in Example 1, except that the formulation of each component was changed as shown in Table 1.

[Comparative Examples 1 to 3]
Black photosensitive resin compositions 6 to 8 were prepared in the same manner as in Example 1, except that the formulation of each component was changed as shown in Table 1.

Details of each component in Table 1 are as follows.
*1: Carboxyl group-containing resin varnish 1
*2: Carboxyl group-containing resin varnish 2
*3: Carboxyl group-containing resin varnish 3 (modified cresol novolac type epoxy acrylate, manufactured by DIC Corporation, UE-9210, solid content concentration 60% by mass)
*4: Biphenyl epoxy resin (manufactured by Nippon Kayaku Co., Ltd., NC-3000H, solid content concentration 75% by mass)
*5: Phenol novolac type epoxy resin (manufactured by DIC Corporation, N-770, solid content concentration 75% by mass)
*6: Trimethylolpropane EO modified triacrylate (manufactured by Toagosei Co., Ltd., Aronix M350)
*7: Ethoxylated bisphenol A methacrylate (bifunctional, manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester BPE-900)
*8: Photosensitive acrylate oligomer containing phosphorus element (weight average molecular weight: 3,000, bifunctional, manufactured by Daicel Cytec Corporation, RAYLOCK1722)
*9: Red colorant (Pigment Red 149)
*10: Blue colorant (Pigment Blue 15)
*11: Yellow colorant (Pigment Yellow 147)
*12: Black colorant (carbon black)
*13: α-Aminoacetophenone photopolymerization initiator (manufactured by IGM Resins, Omnirad 369E)
*14: Titanocene photopolymerization initiator (manufactured by Yueyang Jin Maotai Technology Co., Ltd., JMT784)
*15: Aluminum hydroxide

<Preparation of circuit board>
The black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were coated on the entire surface of the substrate by screen printing so that the film thickness after drying was 20 μm. Thereafter, it was dried at 80° C. for 30 minutes in a hot air circulation drying oven and allowed to cool to room temperature. Using a direct exposure device (DiIMPACT Mms60) manufactured by ORC equipped with an ultra-high-pressure mercury lamp, this substrate was exposed solidly at the optimum exposure dose, and 1 mass % Na ₂ CO ₃ was sprayed at 30° C. under conditions of a spray pressure of 0.2 MPa. Developing was performed for 60 seconds. This substrate was cured in a hot air circulation drying oven at 150° C. for 60 minutes. The obtained circuit board was evaluated as follows.

<Surface condition evaluation>
Regarding the cured coating film of the circuit board obtained in the above <Preparation of circuit board>, surface conditions such as discoloration and foreign matter were observed using an optical microscope.
The surface condition was evaluated based on the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
○: There was no discoloration or foreign matter at all.
△: There were some discoloration and foreign substances, but there were no practical problems.
×: There were many discolorations and foreign substances.

<Low temperature storage evaluation>
Black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were stored at low temperature at 5° C. for 7 days. Thereafter, using the black photosensitive resin compositions 1 to 8 stored at low temperature, a circuit board was obtained in the same manner as in the production of the circuit board described above. The cured coating film of the obtained circuit board was observed for surface conditions such as discoloration and foreign matter using an optical microscope.
The surface condition was evaluated based on the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
○: No discoloration or foreign matter was observed.
×: Discoloration, foreign matter, etc. were observed.

<Optimal exposure amount>
A copper solid substrate with a copper thickness of 18 μm was buff rolled, washed with water, and dried. Subsequently, black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were coated on the entire surface of the dried substrate by screen printing so that the coating film after drying would be 20 μm, and heated at 80°C. It was dried for 30 minutes in a hot air circulation type drying oven. Next, using a direct exposure device (DiIMPACT Mms60) manufactured by Oak Seisakusho Co., Ltd. equipped with an ultra-high pressure mercury lamp, exposure was carried out through a Stouffer 41 step tablet, and 1 mass% Na was exposed at a spray pressure of 0.2 MPa and a liquid temperature of 30°C. The exposure amount that resulted in a pattern of 16 remaining step tablets after 60 seconds of development with a ₂ CO ₃ aqueous solution was defined as the optimum exposure amount (mJ/cm ² ). The optimum exposure amount is shown in Table 2. It is preferable that the optimum exposure amount is smaller.

<Developability evaluation>
A circuit pattern board with a copper thickness of 18 μm was buff rolled, washed with water, and dried. Subsequently, black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were coated on the entire surface of the dried substrate by screen printing so that the coating film after drying was 20 μm, and heated at 80°C. It was dried in a hot air circulation type drying oven for 40 minutes, 50 minutes, and 60 minutes. Next, development was performed for 60 seconds with a 1% by mass Na ₂ CO ₃ aqueous solution at a spray pressure of 0.2 MPa and a liquid temperature of 30° C., and then dried.
The developability of the dried coating film was visually evaluated according to the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
○: The dried coating film was completely removed by development.
Δ: A slight amount of the dried coating film remained after development, but there was no practical problem.
×: A dried coating film clearly remained even after development.

<Solder heat resistance evaluation>
A rosin-based flux was applied to the cured coating film of the circuit board related to black photosensitive resin compositions 1 to 8 obtained in the above <Preparation of circuit board>, and the mixture was immersed in a solder bath preset at 260°C for 10 seconds. . Next, the flux was washed with denatured alcohol.
The blistering and peeling of the cured coating film was visually evaluated according to the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
◎: There was no blistering or peeling in the cured coating film.
○: There was slight swelling or peeling in the cured coating film, but there was no practical problem.
×: There was obvious blistering and peeling in the cured coating film.

<Flexibility evaluation>
The black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were coated on the entire surface of a 25 μm thick polyimide film (Kapton 100H manufactured by DuPont-Toray Co., Ltd.) by screen printing, and dried at 80 ° C. for 30 minutes. , and allowed to cool to room temperature. The obtained substrate was subjected to solid exposure at an optimum exposure amount using a direct exposure device (DiIMPACT Mms60) manufactured by Oak Seisakusho Co., Ltd. equipped with an ultra-high pressure mercury lamp, and a 1 mass % Na ₂ CO ₃ aqueous solution at 30° C. was sprayed at a pressure of 0. Development was performed for 60 seconds at 2 MPa to obtain a test substrate. This substrate was cured by heating at 150° C. for 60 minutes.
The obtained substrate was repeatedly bent 180° several times by half-folding, and the occurrence of cracks in the coating film at that time was observed visually and with an optical microscope at 200x magnification. The number of times was measured.
Flexibility was evaluated based on the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
◎: The number of times of bending was 6 or more.
Good: The number of times of bending was 4 or more and 5 or less.
×: The number of times of bending was 3 or less.

<Appearance evaluation>
The appearance (color) of the cured coating film of the circuit board obtained in the above <Preparation of circuit board> was visually evaluated, and the evaluation results are shown in Table 2. If the cured coating film is black, it has excellent hiding properties.

<Flammability test>
The black photosensitive resin compositions 1 to 8 obtained in Examples were coated on the entire surface of a 25 μm thick polyimide film (Toray Polyimide Film (manufactured by DuPont-Toray Co., Ltd., Kapton 100H (25 μm)) by screen printing, and heated at 80°C. The film was dried for 30 minutes at 80°C and allowed to cool to room temperature.Furthermore, the entire back side was coated by screen printing in the same manner, dried at 80°C for 30 minutes, and allowed to cool to room temperature to obtain a double-sided coated substrate. Using a direct exposure device (DiIMPACT Mms60) manufactured by Oak Seisakusho Co., Ltd. equipped with an ultra-high-pressure mercury lamp, the entire solder resist was exposed solidly at the optimum exposure dose, and a 1 mass % Na ₂ CO ₃ aqueous solution at 30°C was sprayed at a pressure of 2 kg/ cm ² for 60 seconds, and heat-cured at 150° C. for 60 minutes to obtain an evaluation sample. This flammability test sample was subjected to a thin material vertical combustion test in accordance with the UL94 standard (UL94VTM).
Flammability (VTM-0, VTM-1) was evaluated based on the above test results, and the evaluation results are shown in Table 2.

<Cross section>
The black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were applied to a polyimide base material on which a circuit pattern with a copper thickness of 18 μm was formed, and cured under the above substrate manufacturing conditions. The L/S=100/100 μm section was cross-sectioned, and the difference in length between the top part of the coating film and the bottom part of the coating film was measured.
It was evaluated based on the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
Good: The difference in length between the top part of the coating film and the bottom part of the coating film was 0 μm or more and 10 μm or less.
×: The difference in length between the top part of the coating film and the bottom part of the coating film was more than 10 μm.

<Dispersibility evaluation>
Approximately 1 gram of each composition is placed on a metal grind gauge (groove depth 25-50 μm) and a metal scraper is pulled across the surface of the gauge at an even speed for 1-2 seconds to the lowest depth of the groove. Observation was made 3 seconds after the drawing was completed, the point at which noticeable speckles started to appear was read, and grooves containing 5 or more particles were evaluated.
○: It was 25 μm or less.
×: More than 25 μm.

As is clear from the above experimental results, the black photosensitive resin composition according to the present invention was found to be excellent in dispersibility and hiding properties of the obtained cured coating film. It was also found that the cured coating film has excellent low-temperature storage stability and developability, has a small optimum exposure dose, and has excellent surface condition, heat resistance, and flexibility. Furthermore, it was found from the flammability test results that flame retardancy is further improved when a phosphorus element-containing (meth)acrylate oligomer is included. In addition, the black photosensitive resin compositions 1 to 5 used in Examples 1 to 5, which had good dispersibility results, were coated on the entire surface of the substrate by screen printing so that the film thickness after drying was 20 μm. As a result, it was found that all of them exhibited excellent leveling properties.

Claims (1)

A carboxyl group-containing resin having a bisphenol A structure, a thermosetting resin, a photosensitive monomer, a colorant, and a photopolymerization initiator, the colorant including a red colorant, a blue colorant, and a black colorant, A black photosensitive resin composition, wherein the amount of the black colorant is 0.01 part by mass or more and less than 1 part by mass, based on 100 parts by mass of the carboxyl group-containing resin, in terms of solid content. .