JP7324595B2 - Black photosensitive resin composition, cured product thereof, and rigid flexible printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a black photosensitive resin composition and its cured product, and more particularly to a black photosensitive resin composition suitably used as a black solder resist and its cured product. It also relates to a printed wiring board comprising a black solder resist layer made of the cured product.

2. Description of the Related Art Conventionally, printed wiring boards mounted with electronic elements having various functions have been used in electronic devices such as smartphones and personal computers. Printed wiring boards have been made using a material called a rigid substrate, but as electronic devices have become smaller and more multifunctional, the space available to accommodate printed wiring boards in electronic devices has become narrower. .

As a countermeasure, a flexible printed wiring board (FPC), which is a flexible 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 have become more sophisticated, it has become necessary to mount more electronic elements. Therefore, a rigid flexible printed wiring board (RFPC) has been devised as an FPC on which components can be mounted.

Moreover, since the printed wiring board undergoes processes such as solder reflow in order to mount components, it is necessary to form a solder resist (SR) to protect the printed wiring board from the heat and the like at that time. Conventional SR for rigid substrates has high heat resistance, but the rigid substrates themselves are rigid, so flexibility is not required. In addition, since the main purpose of the FPC is to connect rigid substrates, the SR for the 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 for black solder resists as described above (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 in which multiple colors of pigments other than black are mixed is also attracting attention (see, for example, Patent Document 2).

JP 2008-257045 A JP 2010-091876 A

The solder resist used for RFPC requires the heat resistance of solder resist for rigid boards and the flexibility of solder resist for FPC. was inferior in heat resistance. Furthermore, it has been difficult to develop a black photosensitive resin composition that has high sensitivity while giving a black cured coating film and that does not cause foreign substances such as discoloration and recrystallization at low temperatures. Therefore, development of 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 is desired.

In general, resin compositions such as solder resist ink contain resin components and powder components, and if colorants and fillers are not evenly dispersed in these components, leveling will be poor in screen printing. It is difficult because there is a possibility of surface defects of the cured coating film and the like. Furthermore, it is conceivable that the adhesiveness to the substrate deteriorates and the properties of the cured coating film cannot be obtained. Especially when a red colorant is used, this tendency is remarkable, and improvement has been desired in consideration of the surface state and coating properties of the subsequent coating film.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a black photosensitive resin composition which is excellent in dispersibility and hiding property of the resulting cured coating film. Another object of the present invention is to provide a black photosensitive resin composition which is excellent in low-temperature storage stability and developability, has a low optimum exposure dose, and gives a cured coating film which is excellent in surface condition, heat resistance and flexibility. Another object of the present invention is to provide a rigid flexible printed wiring board comprising a black solder resist layer composed of a cured product formed using the photosensitive resin composition.

The present inventors have found that in a photosensitive resin composition containing a carboxyl group-containing resin having a specific structure, a thermosetting resin, a photosensitive monomer, a colorant, and a photopolymerization initiator, at least a red colorant and The inventors have found that the above problem can be solved by using a blue colorant and a small amount of a black colorant. The present invention is based on such findings.

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 colorant, and a photopolymerization initiator, and the colorant is colored red. agent, a blue colorant, and a black colorant, and the amount of the black colorant, in terms of solid content, 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. It is characterized by being characterized by being.

Embodiments of the present invention are preferably substantially free of yellow colorants.

In the aspect of the present invention, the amount of the yellow colorant compounded is preferably 2 parts by mass or less with respect to 100 parts by mass of the carboxyl group-containing resin.

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

In the aspect of this invention, it is preferable that the said black photosensitive resin composition is used for black solder resist formation.

A cured product according to another aspect of the present invention is characterized by being 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 cured product.

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

The black photosensitive resin composition of the present invention is described below. It should be noted that, unless otherwise specified, in this specification, the numerical range represented by the symbol "~" is a range including the upper and lower numerical values (i.e., the lower limit or more, the upper limit or less range) 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 ingredients such as element-containing (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 described below.

[Carboxyl Group-Containing Resin Having Bisphenol A Structure]
As the carboxyl group-containing resin having a bisphenol A structure, conventionally known various resins having a bisphenol A structure and a carboxyl group in the molecule can be used. Flexibility and solder heat resistance are improved because the carboxyl group-containing resin has a bisphenol A structure. When the black photosensitive resin composition contains a resin having a carboxyl group, alkali 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 the molecule is preferable from the viewpoint of photocurability and development resistance. The ethylenically unsaturated double bonds are preferably 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 a photosensitive monomer described later. 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 (both oligomers and polymers).

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

(2) During the synthesis of the resin of (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 terminally (meth)acrylate. carboxyl group-containing photosensitive urethane resin.

(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 carboxyl group-containing photosensitive urethane resin with terminal (meth)acrylate.

(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 type epoxy resin A carboxyl obtained by reacting (meth)acrylic acid with a polyfunctional epoxy resin obtained by further epoxidizing the hydroxyl group of the epoxy resin with epichlorohydrin and adding a dibasic acid anhydride to the resulting hydroxyl group. Group-containing photosensitive resin.

(6) A carboxyl group-containing photosensitive resin obtained by further adding a compound having one epoxy group and one or more (meth)acryloyl groups in one molecule to the resins of (1) to (5).
In this specification, (meth)acrylate is a generic term for 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 40-150 mgKOH/g. By setting the acid value of the carboxyl group-containing resin having a bisphenol A structure to 40 mgKOH/g or more, the alkali development becomes good. Also, by setting the acid value to 150 mgKOH/g or less, it is possible to facilitate drawing of a good resist pattern. More preferably, it is 50 to 130 mgKOH/g.

Although the weight-average molecular weight of the carboxyl group-containing resin having a bisphenol A structure varies depending on the resin skeleton, it 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, the developability and storage stability can be improved. More preferably from 5,000 to 100,000.

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

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

[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 photosensitive monomers include commonly known polyester (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, carbonate (meth)acrylates, and epoxy (meth)acrylates. 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-dimethylaminopropyl acrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; hexanediol, trimethylolpropane, Polyhydric alcohols such as pentaerythritol, dipentaerythritol, tris-hydroxyethyl isocyanurate, or polyhydric acrylates such as their ethyloxide adducts, propylene oxide adducts, or ε-caprolactone adducts; Polyvalent acrylates such as acrylates and ethylene oxide adducts or propylene oxide adducts of these phenols; Polyvalent acrylates; not limited to the above, acrylates and melamine acrylates obtained by directly acrylated polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadiene, and polyester polyols, or urethane acrylated via diisocyanate, and the above acrylates can be appropriately selected from at least one of the methacrylates corresponding to the above. Such photosensitive monomers can also be used as reactive diluents.

Epoxy acrylate resin obtained by reacting acrylic acid with polyfunctional epoxy resin such as cresol novolac type epoxy resin, and half urethane of hydroxy acrylate such as pentaerythritol triacrylate and diisocyanate such as isophorone diisocyanate for the hydroxyl group of the epoxy acrylate resin. You may use the epoxy urethane acrylate compound etc. which reacted the compound as a photosensitive monomer. Such an epoxy acrylate resin can improve the photocurability without deteriorating the dryness to the touch.

The amount of the photosensitive monomer compounded in the black photosensitive resin composition is preferably 0.2 to 60 parts by mass, more preferably 0.2 to 60 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. 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. Also, by setting the blending amount to 60 parts by mass or less, the hardness of the cured coating film can be improved.

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

[Thermosetting resin]
Thermosetting resins used in the present invention include known and commonly used ones such as isocyanate compounds, blocked isocyanate compounds, amino resins, maleimide compounds, benzoxazine resins, carbodiimide resins, cyclocarbonate compounds, epoxy compounds, oxetane compounds, and episulfide resins. is mentioned. Preferred thermosetting resins among these are epoxy resins.

Epoxy resins that can be used include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin. resins, cresol novolak-type epoxy resins, bisphenol A novolac-type epoxy resins, biphenyl-type epoxy resins, naphthalene-type epoxy resins, dicyclopentadiene-type epoxy resins, triphenylmethane-type epoxy resins, and the like. These epoxy resins may be used individually by 1 type, and may be used in combination of 2 or more type.

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

The epoxy group equivalent weight of the epoxy resin in the black photosensitive resin composition is 0.3 to 3.0 per 1 carboxyl group equivalent weight 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, and the like. On the other hand, by setting the above compounding 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 to ensure good strength, etc. of the cured coating film. can.

[Thermal curing catalyst]
A thermosetting catalyst can be added to the black photosensitive resin composition of the present invention. Examples of thermosetting catalysts 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 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 adducts and 2,4-diamino-6-methacryloyloxyethyl-S-triazine/isocyanuric acid adducts can also be used.

If the composition contains a thermosetting component having a cyclic (thio)ether group in the molecule, such as an epoxy resin, the amount of the thermosetting catalyst should be such that the cyclic (thio)ether group in the molecule is converted to solid content. It is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15.0 parts by mass, based on 100 parts by mass of the thermosetting component.

[Coloring agent]
The black photosensitive resin composition of the present invention contains, as colorants, at least a red colorant, a blue colorant and a black colorant, and the amount of the black colorant contained in terms of solid content has a bisphenol A structure. It is characterized by being 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. Any of pigments, dyes, and dyes can be used as the coloring agent. However, it is preferable not to contain a halogen from the viewpoint of environmental load reduction and influence on 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. Examples include monoazo, disazo, azo lake, benzimidazolone, perylene, diketopyrrolopyrrole, condensed azo, anthraquinone, and quinacridone types. C.I.; published by The Society of Dyers and Colorists) numbered. Monoazo red coloring agents 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. Disazo-based red colorants include Pigment Red 37, 38, 41 and the like. Further, as a monoazo lake-based red colorant, Pigment Red 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 50:1, 52:1, 52:2, 53: 1, 53:2, 57:1, 58:4, 63:1, 63:2, 64:1, 68 and the like. Examples of benzimidazolone-based red colorants include Pigment Red 171, 175, 176, 185, 208 and the like. Perylene-based red colorants include Solvent Red 135, 179, Pigment Red 123, 149, 166, 178, 179, 190, 194, 224 and the like. Examples of diketopyrrolopyrrole-based red colorants include Pigment Red 254, 255, 264, 270, 272 and the like. Examples of condensed azo red colorants include Pigment Red 220, 144, 166, 214, 220, 221, 242 and the like. Examples of anthraquinone-based red colorants include Pigment Red 168, 177, 216 and Solvent Red 149, 150, 52, 207. Examples of quinacridone-based red colorants include Pigment Red 122, 202, 206, 207, and 209.

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

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

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

The black photosensitive resin composition in the present invention contains a black coloring agent, and the blending amount of the black coloring agent is black photosensitive with respect to 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure in terms of solid content. It is characterized in that it is 0.01 part by mass or more and less than 1 part by mass in terms of solid content in the resin composition with respect to 100 parts by mass of the carboxyl group-containing resin. Also, it is preferably 0.05 to 0.7 parts by mass. As a result of intensive research by the present inventors, even if a coloring agent with poor dispersibility such as a red coloring agent is used, the dispersibility is remarkably improved by blending a small amount of a black coloring agent within the above range. found to do. Although the reason is not clear, it is presumed as follows. That is, although a certain degree of fluidity is required in order for the dye, which is the material of the colorant, to blend into the resin composition, a black colorant with a low viscosity and fine particles is suitable. However, this is only a speculation and should not be exceeded.
Black colorants 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 them, it is preferable to use carbon black because of its safety and stability in handling.

Examples of the yellow colorant in the black photosensitive resin composition of the present invention include monoazo-based, disazo-based, condensed azo-based, benzimidazolone-based, isoindolinone-based, and anthraquinone-based coloring agents. For example, anthraquinone-based yellow coloring agents include Solvent Yellow 163, Pigment Yellow 24, 108, 193, 147, 199, 202 and the like. Examples of isoindolinone-based yellow colorants 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 benzimidazolone yellow colorants include Pigment Yellow 120, 151, 154, 156, 175, 181 and the like. Further, as a monoazo yellow coloring agent, 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. Disazo yellow coloring agents include Pigment Yellow 12, 13, 14, 16, 17, 55, 63, 81, 83, 87, 126, 127, 152, 170, 172, 174, 176, 188, 198, etc. is mentioned.

Preferably, the black photosensitive resin composition of the present invention does not substantially contain a yellow colorant. In the present specification, the term "substantially free" means that the blending amount in the black photosensitive resin composition, in terms of solid content, is 2 parts by mass with respect to 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure. It means that it is below the division. A yellow colorant is likely to crystallize, resulting in a pattern of yellow spots on the black solder resist layer, which affects the appearance and may be judged as a foreign matter 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 amount of the yellow colorant compounded 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. 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. is mentioned.

[Photoinitiator]
In the present invention, as the photopolymerization initiator used for photopolymerizing the above-described black photosensitive resin composition, a known one can be used. agents, titanocene-based photopolymerization initiators, α-aminoacetophenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and the like. Among them, titanocene-based photopolymerization initiators, α-aminoacetophenone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators are preferred, and combinations of titanocene-based photopolymerization initiators and α-aminoacetophenone-based photopolymerization initiators are preferred. is more preferred. A photoinitiator may be used individually by 1 type, and may be used in combination of 2 or more types.

Specific examples of titanocene-based photopolymerization initiators include bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl) titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium and the like. Commercially available products include JMT784 manufactured by Yueyang Jin Maotai Technology Co., Ltd. and the like.

Specific examples of α-aminoacetophenone-based photopolymerization initiators include 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, 907 manufactured by IGM Resins.

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

The amount of the photopolymerization initiator compounded in the photosensitive resin composition is preferably 0.5 to 10 parts by mass in terms of solid content with respect to 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure. When the content is 0.5 parts by mass or more, the photocurability of the resin composition is improved, the film is less likely to peel off, and film properties such as chemical resistance are improved. On the other hand, when the content is 10 parts by mass or less, the effect of reducing outgassing is obtained, the light absorption on the surface of the solder resist coating film is improved, and the deep-part curability is less likely to deteriorate. More preferably, it is 1 to 8 parts by mass.

A photoinitiation assistant or a sensitizer may be used in combination with the photopolymerization initiator described above. Photoinitiation aids or sensitizers include benzoin compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, xanthone compounds, and the like. Thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone are particularly preferred. Inclusion of a thioxanthone compound can improve deep-part curability. These compounds can be used as a photopolymerization initiator in some cases, but are preferably used in combination with the photopolymerization initiator. Also, the photoinitiation aids or sensitizers may be used singly or in combination of two or more.

In addition, since these photoinitiators, photoinitiator aids, and sensitizers absorb specific wavelengths, the sensitivity may be lowered in some cases, and they may function as ultraviolet absorbers. However, these are not used only for the purpose of improving the sensitivity of the composition. It absorbs light of a specific wavelength as needed to increase the photoreactivity of the surface, change the line shape and opening of the resist to vertical, tapered, and reverse tapered shapes, and improve the accuracy of the line width and opening diameter. can be improved.

[Phosphorus element-containing (meth)acrylate oligomer]
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. The phosphorus element-containing (meth)acrylate oligomer is a compound containing one or more (meth)acrylates in the molecule 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 anhydrides thereof include, for example, compounds obtained by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with itaconic acid and their and anhydrides.

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

The 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 mass, more preferably 30 to 70 parts by mass. If the content of the phosphorus element-containing (meth)acrylate oligomer is within the above range, heat resistance and flame retardancy can be improved.

[Flame retardants]
In order to further improve the flame retardancy 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. Aluminum hydroxide etc. are mentioned as a flame retardant. The amount of the flame retardant compounded is preferably 20 to 40 parts by mass in terms of solid content with respect to 100 parts by mass of the carboxyl group-containing resin having a bisphenol A structure.

[Other ingredients]
The black photosensitive resin composition may optionally contain an inorganic filler for the purpose of improving properties such as adhesion, mechanical strength and linear expansion coefficient of the cured product. For example, known and commonly used inorganic fillers such as barium sulfate, barium titanate, silicon oxide powder, fine silicon oxide powder, amorphous silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide and mica powder can be used.

Components such as an adhesion promoter, an antioxidant, an ultraviolet absorber, and a dispersant can be added to the black photosensitive resin composition, if necessary. As these, those known in the field of electronic materials can be used. In addition, at least one of silicone-based, fluorine-based, polymer-based defoaming agents and leveling agents, imidazole-based, thiazole-based, triazole-based silane coupling agents, rust inhibitors, fluorescent brighteners, etc. At least one of known and commonly used additives such as

In the present invention, an organic solvent can be used for preparation and viscosity adjustment of the black photosensitive resin composition. Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum solvents. 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 and propylene glycol; aliphatic carbonization such as octane and decane Hydrogen: Petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, solvent naphtha, and the like. Such organic solvents may be used singly or as a mixture of two or more.

[Use]
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 filler for forming solder resists, interlayer insulating materials, marking inks, coverlays, solder dams, through-holes and via-holes of printed wiring boards, and filling of recessed portions. . Among them, it can be suitably used for forming a black solder resist, and particularly suitable for forming a black solder resist layer of a rigid flexible wiring board. Also, 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 comprises a black solder resist layer comprising 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 circuit board (RFPC).

In the printed wiring board manufacturing method of the present invention, the black photosensitive resin composition is applied onto a substrate and cured by at least one of light and heat to form a solder resist layer composed of the cured product. It is. An example of the method for forming the solder resist layer will be described below.

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

Base materials used for the circuit-formed substrate include paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth/non-woven cloth 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, Wafer plates and the like can be mentioned.

Suitable irradiation light sources for active energy ray irradiation include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps and metal halide lamps. In addition, a laser beam or the like can also be used as an active energy ray.

Examples of the developing method include a dipping method, a shower method, a spray method, a brush method, and the like. Dilute alkaline aqueous solutions such as ammonia and amines can be used.

EXAMPLES Next, the present invention will be described 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 a bisphenol A type epoxy resin (epoxy equivalent: 650 g/eq, softening point: 81.1°C) in which X is C(CH ₃ ) ₂ and the average polymerization degree n is 3.3 in the following general formula (I), and epichlorohydrin After dissolving 925 parts in 462.5 parts of dimethyl sulfoxide, 52.8 parts of 98.5% NaOH was added at 70° C. over 100 minutes while stirring. After the addition, the reaction was further carried out at 70°C for 3 hours. After completion of the reaction, 250 parts of water was added and washed with water. After the oil-water separation, most of the dimethylsulfoxide and excess unreacted epichlorohydrin were recovered from the oil layer by distillation under reduced pressure. were added and reacted at 70° C. for 1 hour. After completion of the reaction, it was washed twice with 200 parts of water. After the oil-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 starting bisphenol A epoxy resin 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 resulting solution is once cooled to 60° C., 72 parts (1 mol) of acrylic acid, 0.5 part of methylhydroquinone, and 2 parts of triphenylphosphine are added, heated to 100° C., reacted for about 60 hours, and acidified. A reactant with a value of 0.2 mg KOH/g was obtained. To this, 140 parts (0.92 mol) of tetrahydrophthalic anhydride was added, and the mixture was heated to 90° C. for reaction to obtain a carboxyl group-containing resin varnish 2. The obtained carboxyl group-containing resin varnish 1 had a solid content concentration of 62% by mass and a solid content acid value (mgKOH/g) of 100.

(Synthesis example 2)
<Synthesis of carboxyl group-containing resin varnish 2>
In the following general formula (I), X is CH ₂ and 380 parts of a bisphenol F type epoxy resin (epoxy equivalent: 950 g/eq, softening point: 85°C) having an average degree of polymerization of 6.2 and 925 parts of epichlorohydrin are combined with 462 parts of dimethyl sulfoxide. 0.5 part, 60.9 parts of 98.5% NaOH was added at 70° C. over 100 minutes while stirring. After the addition, the reaction was further carried out at 70°C for 3 hours. After completion of the reaction, 250 parts of water was added and washed with water. After the oil-water separation, most of the dimethylsulfoxide and excess unreacted epichlorohydrin were recovered from the oil layer by distillation under reduced pressure. were added and reacted at 70° C. for 1 hour. After completion of the reaction, it was washed twice with 200 parts of water. After oil-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), when 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 resulting solution is once cooled to 60° C., 72 parts (1 mol) of acrylic acid, 0.5 part of methylhydroquinone, and 2 parts of triphenylphosphine are added, heated to 100° C., reacted for about 60 hours, and acidified. A reactant with a value of 0.2 mg KOH/g was obtained. To this, 140 parts (0.92 mol) of tetrahydrophthalic anhydride was added and the mixture was heated to 90° C. for reaction to obtain a carboxyl group-containing resin varnish 1. The obtained carboxyl group-containing resin varnish 2 had a solid content concentration of 62% by mass and a solid content acid value (mgKOH/g) of 100.

（式中、ＸはＣＨ_２またはＣ（ＣＨ_３）_２を表し、ｎは１～１２である。）

(Wherein, X represents CH ₂ or C(CH ₃ ) ₂ and n is 1-12.)

<Preparation of black photosensitive resin composition>
[Example 1]
A carboxyl group-containing resin, a thermosetting resin, a photosensitive monomer (reactive diluent), a phosphorus element-containing (meth)acrylate oligomer, a colorant, a photopolymerization initiator, and a flame retardant are shown in Table 1. The black photosensitive resin composition 1 was prepared by blending in the indicated proportions (parts by mass), pre-mixing with a stirrer, and then kneading with a three-roll mill. In addition, the value of the compounding amount in a table|surface shows the mass part of solid content, unless there is particular notice.

[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 type methacrylate (bifunctional, manufactured by Shin-Nakamura Chemical Co., Ltd., NK Ester BPE-900)
*8: Phosphorus element-containing photosensitive acrylate oligomer (weight average molecular weight: 3,000, bifunctional, manufactured by Daicel-Cytec Co., Ltd., 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-based photopolymerization initiator (OMNIRAD 369E, manufactured by IGM Resins)
* 14: Titanocene-based photopolymerization initiator (manufactured by Yueyang Jin Maotai Technology Co., Ltd., JMT784)
*15: Aluminum hydroxide

<Production of circuit board>
The black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were applied to the entire substrate by screen printing so that the film thickness after drying was 20 μm. After that, it was dried at 80° C. for 30 minutes in a hot air circulating drying oven, and allowed to cool to room temperature. Using a direct exposure apparatus (DiIMPACT Mms60) manufactured by ORC equipped with an ultra-high pressure mercury lamp, this substrate is exposed in a solid manner at an optimum exposure amount, and sprayed with 1% by mass Na ₂ CO ₃ at 30° C. under conditions of a spray pressure of 0.2 MPa. was developed for 60 seconds. This substrate was cured at 150° C. for 60 minutes in a hot air circulating drying oven. The following evaluations were performed on the obtained circuit board.

<Surface condition evaluation>
The cured coating film of the circuit board obtained in the above <Preparation of circuit board> was observed with an optical microscope for surface conditions such as discoloration and foreign matter.
The surface condition was evaluated according to the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
◯: There was no discoloration or foreign matter at all.
Δ: Some discoloration, foreign substances, etc. were found, but there was no practical problem.
x: There were many discolorations, foreign substances, and the like.

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

<Optimal Exposure>
A copper solid substrate having a copper thickness of 18 μm was buffed with a buff roll, washed with water, and dried. Subsequently, the black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were applied to the entire surface of the substrate after drying by screen printing so that the coating film after drying was 20 μm, and the temperature was 80 ° C. was dried for 30 minutes in a hot air circulating drying oven. Then, using a direct exposure device (DiIMPACT Mms60) manufactured by Oak Manufacturing Co., Ltd. equipped with an ultra-high pressure mercury lamp, exposure was performed through a Stouffer 41-stage step tablet, and 1 mass% Na at a spray pressure of 0.2 MPa and a liquid temperature of 30 ° C. The optimum exposure dose (mJ/cm ² ) was defined as the exposure dose at which the step tablet pattern remained at 16 when the film was developed with an aqueous solution of ₂ CO ₃ for 60 seconds. Table 2 shows the optimum exposure dose. The smaller the optimum exposure amount, the better.

<Developability evaluation>
A circuit pattern substrate having a copper thickness of 18 μm was buffed with a buff roll, washed with water, and dried. Subsequently, the black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were applied to the entire surface of the substrate after drying by screen printing so that the coating film after drying was 20 μm, and the temperature was 80 ° C. 40 minutes, 50 minutes, and 60 minutes in a hot air circulating drying oven. Next, development was performed for 60 seconds with a 1% by mass Na ₂ CO ₃ aqueous solution having a spray pressure of 0.2 MPa and a liquid temperature of 30° C., followed by drying.
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 dry coating film was completely removed by development.
Δ: A small amount of dried coating remained after development, but there was no practical problem.
x: A dry coating film remained clearly after development.

<Solder heat resistance evaluation>
A rosin-based flux was applied to the cured coating film of the circuit board regarding the black photosensitive resin compositions 1 to 8 obtained in <Preparation of circuit board> above, and immersed in a solder bath previously set at 260 ° C. for 10 seconds. . The flux was then washed with denatured alcohol.
Blistering and peeling of the cured coating film were visually evaluated according to the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
⊚: No blistering or peeling of the cured coating film.
◯: Slight swelling or peeling of the cured coating film was observed, but there was no practical problem.
x: Blistering and peeling were clearly observed in the cured coating film.

<Flexibility evaluation>
Black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples were applied to the entire surface of a 25 μm-thick polyimide film (Kapton 100H manufactured by Toray DuPont Co., Ltd.) by screen printing and dried at 80° C. for 30 minutes. was allowed to cool to room temperature. The resulting substrate was subjected to solid exposure at an optimum exposure amount using a direct exposure apparatus (DiIMPACT Mms60) manufactured by Oak Manufacturing 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 0.5. Development was performed for 60 seconds under the condition of 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 at 180° by seam folding, and the state of crack generation in the coating film at that time was observed visually and with a 200-fold optical microscope, and the bending was performed until cracks occurred. measured the number of times.
Flexibility was evaluated according to the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
A: The number of times of bending was 6 or more.
◯: The number of times of bending was 4 times or more and 5 times or less.
x: The number of times of bending was 3 times or less.

<Appearance evaluation>
The appearance (color) of the cured coating film of the circuit board obtained in <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.

<Combustibility test>
The black photosensitive resin compositions 1 to 8 obtained in Examples were applied to a 25 μm thick polyimide film (Toray polyimide film (manufactured by Toray DuPont Co., Ltd., Kapton 100H (25 μm)) by screen printing, and the temperature was 80° C. The substrate was dried for 30 minutes at room temperature and cooled to room temperature. Using a direct exposure apparatus (DiIMPACT Mms60) manufactured by Oak Manufacturing Co., Ltd. equipped with an ultra-high pressure mercury lamp, the entire surface of the solder resist is exposed to light with an optimum exposure amount, and a 1% by mass Na ₂ CO ₃ aqueous solution at 30° C. is sprayed at a pressure of 2 kg/. C. cm ² for 60 seconds, followed by thermal curing for 60 minutes at 150° C. to obtain an evaluation sample, which was subjected to a thin material vertical burning test in accordance with 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>
Each of the black photosensitive resin compositions 1 to 8 obtained in Examples and Comparative Examples was applied to a polyimide substrate on which a circuit pattern having a copper thickness of 18 μm was formed, and cured under the above-described substrate preparation conditions. The L/S=100/100 μm portion was cross-sectioned to measure the length difference between the top portion of the coating film and the bottom portion of the coating film.
Evaluation was performed according to the following criteria, and the evaluation results are shown in Table 2.
[Evaluation criteria]
◯: The difference in length between the top portion of the coating film and the bottom portion of the coating film was 0 μm or more and 10 μm or less.
x: The length difference between the top portion of the coating film and the bottom portion of the coating film was more than 10 μm.

<Dispersibility evaluation>
About 1 gram of each composition is placed on a metal grind gauge (25-50 μm groove depth) and a metal scraper is drawn across the surface of the gauge at an even speed to the minimum depth of the groove over 1-2 seconds. Observation was made 3 seconds after the end of drawing, and the point at which conspicuous speckles began to appear was read, and grooves with 5 or more particles were evaluated.
◯: 25 μm or less.
×: greater 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 property of the resulting cured coating film. In addition, it has been found that the cured coating film obtained is excellent in low-temperature storage stability and developability, has a low optimum exposure dose, and is excellent in surface condition, heat resistance and flexibility. Furthermore, it was found from the result of the flammability test that the flame retardancy was further improved when the phosphorus element-containing (meth)acrylate oligomer was included. In addition, the black photosensitive resin compositions 1 to 5 used in Examples 1 to 5, which had good dispersibility results, were applied to the entire surface of the substrate so that the film thickness after drying was 20 μm by screen printing. As a result, it was found that all of them exhibited excellent leveling properties.

Claims (7)

A carboxyl group-containing resin having a bisphenol A structure, a thermosetting resin, a photosensitive monomer, a coloring agent, and a photopolymerization initiator, wherein the coloring agent includes a red coloring agent, a blue coloring agent and a black coloring agent, The blending amount of the black coloring agent is 0.01 parts by mass or more and less than 1 part by mass with respect to 100 parts by mass of the carboxyl group-containing resin in terms of solid content , and the blending amount of the yellow coloring agent is the carboxyl A black photosensitive resin composition containing 1 part by mass or less (excluding 1 part by mass) with respect to 100 parts by mass of the group-containing resin. 2. The black photosensitive resin composition according to claim 1 , wherein the amount of said yellow colorant compounded is 0.1 parts by mass or less with respect to 100 parts by mass of said carboxyl group-containing resin. 3. The black photosensitive resin composition according to claim 1 , further comprising a phosphorus element-containing (meth)acrylate oligomer. The black photosensitive resin composition according to any one of claims 1 to 3 , wherein the photopolymerization initiator comprises a titanocene-based photopolymerization initiator and an α-aminoacetophenone-based photopolymerization initiator. The black photosensitive resin composition according to any one of claims 1 to 4 , which is used for forming a black solder resist. A cured product obtained by curing the black photosensitive resin composition according to any one of claims 1 to 5 . A rigid flexible printed wiring board comprising the cured product according to claim 6 .