JP2007133232A - Photosensitive thermosetting resin composition and flexible printed wiring board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkali developable photosensitive thermosetting resin composition capable of forming a flexible fine pattern, excellent in electric insulation, resistance to the heat of soldering and chemical resistance, and excellent further in reflow resistance, and a flexible printed wiring board using the same. <P>SOLUTION: The alkali developable photosensitive thermosetting resin composition contains (A) a bisphenol type epoxy acrylate resin having a (meth)acryloyl group and a carboxyl group in one molecule and soluble in a dilute alkali solution, (B) an epoxy compound having two or more epoxy groups in one molecule, (C) a photopolymerization initiator, (D) a reactive diluent and (E) a compound having an imidazole group and an alkoxysilyl group in one molecule. The flexible printed wiring board using the same is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photosensitive thermosetting resin composition having excellent flexibility and a flexible printed wiring board using the same.

  In order to protect the wiring pattern on the board from the external environment and to prevent the solder from adhering to unnecessary parts in the soldering process performed when surface mounting electronic components on the printed wiring board, the printed wiring board In some cases, the surface is covered with a protective film called a cover coat or a solder mask.

A photosensitive solder resist made of an acrylate resin modified with an epoxy resin can be used as the protective film. Since this resist is excellent in electrical insulation, solder heat resistance, and chemical resistance, It was used (for example, refer patent documents 1-3).
Japanese Patent No. 3281473 JP 2004-85738 A JP-A-2005-62450

  However, these photosensitive solder resists may not be satisfactory in terms of reflow resistance, and a photosensitive thermosetting resin composition having better reflow resistance while maintaining the above resist characteristics. It was sought after.

  Therefore, the present invention is rich in flexibility, can form a fine pattern, is excellent in electrical insulation, solder heat resistance, chemical resistance, etc., and further is an alkali development type photosensitive thermosetting type excellent in reflow resistance. It aims at providing a resin composition and a flexible printed wiring board using the same.

  As a result of intensive studies to solve the above-described problems, the present inventor has developed a predetermined resin and imidazole in one molecule in order to improve the reflow resistance of the alkali development type photosensitive thermosetting resin composition. The present invention was completed by finding that the above-mentioned problems can be solved by a combination of a group having a group having an alkoxysilyl group.

  That is, the alkali developing negative photosensitive thermosetting resin composition of the present invention has (A) a bisphenol type epoxy which has (meth) acryloyl group and carboxyl group in one molecule and is soluble in dilute alkali solution. An acrylate resin, (B) an epoxy compound having two or more epoxy groups in one molecule, (C) a photopolymerization initiator, (D) a reactive diluent, and (E) an imidazole group in one molecule. And at least one epoxy selected from bisphenol-type epoxy resins, biphenyl-type epoxy resins, and novolac-type epoxy resins as the epoxy compound (B). By using the compound, various properties including reflow resistance are excellent.

  The flexible printed wiring board of the present invention is characterized in that it has a protective film on the surface using the alkali development negative photosensitive thermosetting resin composition of the present invention.

  According to the photosensitive thermosetting resin composition of the present invention, the cured product is excellent in electrical insulation, solder heat resistance, chemical resistance, and reflow resistance. When used as a protective layer for a printed wiring board, a flexible printed wiring board that is stable in the external environment can be produced.

  Hereinafter, the present invention will be described in detail.

  The bisphenol type epoxy acrylate resin which is the component (A) used in the present invention has a main skeleton of bisphenol A or bisphenol F in one molecule, has a (meth) acryloyl group and a carboxyl group, and can be used in a dilute alkaline solution. It is a melting thing. In this component, (meth) acryloyl groups in the molecule are polymerized by radicals generated from the photopolymerization initiator (C) when irradiated with active energy rays such as ultraviolet rays, and as a result, the resin composition is insolubilized. It has a function.

  Examples of such an (A) epoxy acrylate resin include an epoxy acrylate oligomer obtained by esterifying acrylic acid or methacrylic acid to a bisphenol-type epoxy resin and then adding an acid anhydride. .

  Examples of the acid anhydride used here include phthalic anhydride, succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, itaconic anhydride. Methyl endomethylenetetrahydrophthalic anhydride can be used, and succinic anhydride or phthalic anhydride is particularly preferable.

  The component (A) used in the present invention preferably has an acid value of 50 to 200 mg KOH / g, and more preferably 90 to 150 mg KOH / g. If this acid value is less than 50 mg KOH / g, the alkali solubility is lowered and alkali development becomes difficult. On the other hand, if the acid value exceeds 200 mg KOH / g, it is used as an alkali development type photoresist. In this case, the film loss during development is large, and the resolution may be significantly reduced.

  Moreover, it is preferable to mix | blend the quantity used as (A) component contained in this invention in 20-70 mass% in a resin composition.

  The (B) epoxy compound used in the present invention is not particularly limited as long as it is an epoxy compound having two or more epoxy groups in one molecule. Biphenyl type epoxy resin, biphenyl novolak type epoxy resin, phenol novolak type epoxy resin, o-cresol novolak type epoxy resin, p-cresol novolak type epoxy resin, bisphenol A type tertiary fatty acid modified polyol epoxy resin; diglycidyl phthalate, Diglycidyl esters such as tetrahydrophthalic acid diglycidyl ester and dimer acid diglycidyl ester, diglycidyl aniline, diglycidyl toluidine, alicyclic epoxy resin, trishydroxyphenyl meta Type epoxy resins, diglycidyl amine such as tetraphenyl ethane type epoxy resins, bisphenol epoxy resins, biphenyl type epoxy resin is preferably a novolac-type epoxy resin. These may be used individually by 1 type, and may mix and use 2 or more types.

  The component (B) included in the present invention is preferably blended in the resin composition in an amount of 5 to 50% by mass.

  Moreover, since the epoxy compound (B) is used, it is preferable to use an epoxy resin curing agent in combination in order to further improve the properties such as adhesion, chemical resistance and heat resistance.

Specific examples of the epoxy resin curing agent, an imidazole derivative _{(e.g., 2MZ, 2E4MZ, C 11 Z} , C 17 Z, 2PZ, 1B2MZ, 2MZ-CN, 2E4MZ-CN, C 11 Z-CN, 2PZ-CN, 2PHZ-CN, 2MZ-CNS, 2E4MZ-CNS, 2PZ-CNS, 2MZ-AZINE, 2E4MZ-AZINE, C 11 Z-AZINE, 2MA-OK, 2P4MHZ, 2PHZ, 2P4BHZ ( manufactured by Shikoku Chemicals Co., Ltd.)) , Diaminodiphenylmethane, m-phenylenediamine, m-xylenediamine, diaminodiphenylsulfone, dicyandiamide, urea, urea derivatives, melamine, polybasic hydrazide and the like; their organic acid salts and / or epoxy adducts; boron trifluoride The amine Body; triazine derivatives such as ethyldiamino-S-triazine, 2,4-diamino-S-triazine, 2,4-diamino-6-xylyl-S-triazine, trimethylamine, triethanolamine, N, N-dimethyloctyl Tertiary amines such as amine, N-benzyldimethylamine, pyridine, N-methylmorpholine, hexa (N-methyl) melamine, 2,4,6-tris (dimethylaminophenol), tetramethylguanidine, m-aminophenol , Polyphenols such as polyvinylphenol, polyvinylphenol bromide, phenol novolak and alkylphenol novolak, organic phosphines such as tributylphosphine, triphenylphosphine and tris-2-cyanoethylphosphine, tri-n-butyl (2,5-di- Hydroxyphenyl) phosphonium bromide, phosphonium salts such as hexadecyltributylphosphonium chloride, quaternary ammonium salts such as benzyltrimethylammonium chloride, phenyltributylammonium chloride, polybasic acid anhydrides, diphenyliodonium tetrafluoroboroate, triphenylsulfonium Xafluoroantimonate, 2,4,6-triphenylthiopyrylium hexafluorophosphate, photocationic polymerization catalyst (eg, Irgacure-261 (Ciba Geigy), Optoma-SP-170 (Asahi Denka Co., Ltd.) )), Styrene-maleic anhydride resin, equimolar reaction product of phenyl isocyanate and dimethylamine, organic compounds such as tolylene diisocyanate and isophorone diisocyanate Curing agents and curing accelerators such conventionally known, such as equimolar reaction product of polyisocyanate and dimethylamine and the like, which may be used alone or in combination.

  The amount of the epoxy resin curing agent used is preferably 0.01 to 25 parts by mass and particularly preferably 0.1 to 15 parts by mass with respect to 100 parts by mass of the (B) epoxy compound.

  Examples of the (C) photopolymerization initiator used in the present invention include benzoins such as benzoin, benzoin methyl ether, and benzoin isopropyl ether, acetophenone, 2,2-dimethoxy-2-phenylacetophenone, and 2,2-diethoxy-2. -Phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, N, N-dimethyl Acetophenones such as aminoacetophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, anthraquinones such as 2-aminoanthraquinone, 2,4-dimethyl Thioxanthones such as thioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone, ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal, benzophenone, methylbenzophenone, 4,4′-dichlorobenzophenone, There are benzophenones such as 4,4'-bisdiethylaminobenzophenone, Michler's ketone, 4-benzoyl-4'-methyldiphenyl sulfide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc., which are used alone or in combination of two or more. be able to.

  Further, the (C) photopolymerization initiator includes three kinds such as N, N-dimethylaminobenzoic acid ethyl ester, N, N-dimethylaminobenzoic acid isoamyl ester, pentyl-4-dimethylaminobenzoate, triethylamine, and triethanolamine. Photosensitizers such as secondary amines can be used alone or in combination of two or more.

  A preferred combination of a photopolymerization initiator and a photosensitizer is 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (product name: Irgacure-, manufactured by Ciba-Geigy). 907) and 2,4-diethylthioxanthone (manufactured by Nippon Kayaku Co., Ltd., trade name: Kayacure-DETX), 2-isopropylthioxanthone or 4-benzoyl-4'-methyldiphenyl sulfide.

  The component (C) included in the present invention is preferably blended in an amount of 0.5 to 20% by mass in the resin composition.

  The (D) reaction diluent used in the present invention is a photopolymerizable monomer, which dilutes the component (A) to make it easy to apply and enhances photopolymerizability. Examples of the (D) reaction diluent include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, ethylene glycol, methoxytetraethylene glycol, polyethylene glycol and the like. Glycol (mono) or di (meth) acrylates, N, N-dimethyl (meth) acrylamide, (meth) acrylamides such as N-methylol (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, etc. Polyalkyl alcohols such as aminoalkyl (meth) acrylates, hexanediol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, tris-hydroxyethyl isocyanurate These are ethylene oxide or propylene oxide adducts such as polyvalent (meth) acrylates, phenoxyethyl (meth) acrylate, bisphenol A polyethoxydi (meth) acrylate and other phenolic ethylene oxide or propylene oxide adduct (meth) Acrylates, glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, glycidyl ether (meth) acrylates such as triglycidyl isocyanurate, ε-caprolactone modified (meth) acrylates such as caprolactone-modified tris (acryloxyethyl) isocyanurate And melamine (meth) acrylate can be used, and these can be used alone or as a mixture of two or more.

  It is preferable to mix | blend the quantity which becomes 5-80 mass% in this resin composition, and, as for the quantity of this (D) component, it is especially preferable that it is 10-70 mass%.

  (E) A compound having an imidazole group and an alkoxysilyl group in one molecule used in the present invention has various effects such as acceleration of resin curing by an imidazole group, improvement of rust prevention and adhesion by an alkoxysilyl group, and imparting moisture resistance. It is added for the purpose.

（式中、Ｒ^１は、水素原子、ビニル基又は炭素数１〜５のアルキル基であり、Ｒ^２は、水素原子又は炭素数１〜２０のアルキル基であり、Ｒ^３〜Ｒ^４は、それぞれ炭素数１〜１０のアルキレン基又は水酸基含有アルキレン基であり、Ｒ^５〜Ｒ^６は、それぞれ炭素数１〜３のアルキル基であり、ＸはＯ、ＣＯ_２、Ｓ及びＳＯ_２から選ばれる基であり、ｍは１〜３の整数である。）で表される。 (E) A compound having an imidazole group and an alkoxysilyl group in one molecule has the following general formula:

(In the formula, R ¹ is a hydrogen atom, a vinyl group or an alkyl group having 1 to 5 carbon atoms, R ² is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and R ^{3 to} R ⁴ are Each is an alkylene group having 1 to 10 carbon atoms or a hydroxyl group-containing alkylene group, R ^{5 to} R ⁶ are each an alkyl group having 1 to 3 carbon atoms, and X is selected from O, CO ₂ , S and SO _2. And m is an integer of 1 to 3).

  Examples of the component (E) include an imidazole silane having an alkoxysilyl group such as trialkoxysilyl group, dialkoxysilyl group, secondary hydroxyl group-containing trialkoxysilyl group, secondary hydroxyl group-containing dialkoxysilyl group, and imidazole group. The general formulas are as follows (in the formulas, R is an alkyl group having 1 to 3 carbon atoms).

  The component (E) has an imidazole group and an alkoxysilyl group in one molecule, and can be reacted with an organic acid such as acetic acid, palmitic acid or phthalic acid to form an organic salt, or a solvent such as alcohol. It can also be used after diluted.

  The amount used is preferably in the range of 0.01 to 5% by mass in the resin composition of the present invention, particularly preferably 0.1 to 1% by mass.

  In the present invention, an organic solvent can be used for the purpose of further improving printability. Typical organic solvents include ketones such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene, methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, and propylene glycol. Glucol ethers such as monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, triethylene glycol monoethyl ether, esters such as ethyl acetate, butyl acetate, butyl cellosolve acetate, carbitol acetate, ethanol, propanol, Alcohols such as ethylene glycol and propylene glycol, aliphatic hydrocarbons such as octane and decane, petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, It may be mentioned petroleum-based solvents such as Bentonafusa.

  Further, for the purpose of further improving the properties such as adhesion, heat resistance, hardness and the like, barium sulfate, barium titanate, silicon oxide powder, finely divided silicon oxide, amorphous silica, talc, clay, magnesium carbonate, Known and commonly used inorganic fillers such as calcium carbonate, aluminum oxide, aluminum hydroxide, and mica powder can be blended.

  Further, if necessary, known and commonly used colorants such as phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, crystal violet, titanium oxide, carbon black, naphthalene black, hydroquinone, hydroquinone monomethyl ether, tert- Known and conventional polymerization inhibitors such as butylcatechol, pyrogallol and phenothiazine, known and conventional thickeners such as asbestos, olben, benton and montmorillonite, antifoaming agents such as silicones, fluorines and polymers, and / In addition, known and commonly used additives such as leveling agents, imidazole-based, thiazole-based, triazole-based, and adhesion-imparting agents such as silane coupling agents can be used.

  In addition, copolymers of ethylenically unsaturated compounds such as acrylic acid esters, known and conventional binder resins such as polyester resins synthesized from polyhydric alcohols and polybasic acid compounds, and polyester (meth) acrylates, Photopolymerizable oligomers such as polyurethane (meth) acrylate and epoxy (meth) acrylate can also be used as long as they do not affect various properties as a solder resist.

  In addition to the essential components (A) to (E), the photosensitive thermosetting resin composition of the present invention is added and blended with other components as necessary, and then uniformly with a three-roll mill or the like. It can be manufactured by mixing. The photosensitive thermosetting resin composition of the present invention is adjusted to a viscosity suitable for the coating method as necessary, and this is applied to, for example, a screen printed method, curtain coating method, spray coating on a printed wiring board formed with a circuit. A tack-free coating film can be formed by applying an organic solvent contained in the resin composition in a temperature range of 60 to 100 ° C. it can.

  Then, it is selectively exposed with actinic light through a photomask having a predetermined exposure pattern, and the unexposed portion is diluted with an alkaline aqueous solution such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, Examples include aqueous solutions of sodium silicate, ammonia, amines and the like.

  In addition, low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, xenon lamp, metal halide lamp, etc. can be used as the irradiation light source for photocuring, and laser beams etc. are also used as exposure active energy rays can do.

  In addition, the flexible printed wiring board of the present invention is a flexible printed wiring in which the photosensitive thermosetting resin composition of the present invention in the form of a varnish is bonded to one surface or both surfaces with a hot roll, for example, a polyimide film and a copper foil. A flexible copper-clad laminate is manufactured by the usual method of coating on the plate and then heat-curing, drilling if necessary, through-hole plating, or overlaying a coverlay with holes in place. It can be produced by the usual method of heat-press molding.

  Therefore, as a specific configuration of the flexible printed wiring board of the present invention, for example, the photosensitive layer of the present invention is formed on the surface of a flexible printed wiring board composed of a polyimide layer and a copper layer or a polyimide layer, an adhesive layer and a copper layer. Having a protective layer formed of a heat-curable thermosetting resin composition.

  Furthermore, a flexible printed wiring board with a reinforcing plate can be manufactured by a normal method of superposing a reinforcing plate on the flexible printed wiring board via a thermosetting resin composition and then heat-press molding, or this flexible printed wiring board. A conventional method in which a flexible copper-clad laminate or the like is superimposed on a thermosetting resin composition, heated and pressed, formed through holes, plated through holes, and then a predetermined circuit is formed. Thus, a multilayer printed wiring board can be obtained.

  The present invention will be described in detail based on the following examples. All parts are parts by mass.

Example 1
Bisphenol F type epoxy acrylate resin KAYARAD ZFR1122 (Nippon Kayaku Co., Ltd., trade name) 80 parts by mass, photopolymerizable monomer KAYARAD DPHA (Nippon Kayaku Co., Ltd., trade name) 20 parts by mass, photopolymerization initiator IRUGACURE
907 (manufactured by Ciba Geigy Co., Ltd., product name) 8 parts by mass, photosensitizer KAYACURE DETX-S (manufactured by Nippon Kayaku Co., Ltd., product name) 2 parts by mass, biphenyl type epoxy resin YX4000 (manufactured by Japan Epoxy Resin Co., Ltd., product) Name) 20 parts by mass, imidazole-based curing agent C17Z (trade name, manufactured by Shikoku Kasei Kogyo Co., Ltd.) 1 part by mass, dicyandiamide-based curing agent Epicure DICY (trade name, manufactured by Japan Epoxy Resin Co., Ltd.) 3 parts by mass, barium sulfate B -30 (manufactured by Sakai Chemical Industry Co., Ltd., trade name) 10 parts by weight, pigment FASTOGEN BLUE5380 (manufactured by Dainippon Ink & Chemicals, trade name) 1 part by weight, fine silica R972 (trade name, manufactured by Nippon Aerosil Co., Ltd.) 5 parts by mass, imidazole silane IS1000 (manufactured by Nikko Materials Corporation, Name) 1 part by mass, to produce an alkali development negative photosensitive thermosetting resin composition was uniformly mixed by kneading with a three-roll mill.

  A copper-clad polyimide film substrate (copper thickness: 18 μm / polyimide film thickness: 25 μm) patterned to have a thickness of 20 to 30 μm using a 150 mesh polyester screen with a screen printer. The whole surface is applied to the film, and the coating film is dried for 30 minutes by a hot air dryer at 80 ° C.

Next, the negative film of the resist pattern was brought into contact with the coating film and irradiated with ultraviolet rays using an ultraviolet irradiation exposure apparatus (exposure amount 400 mJ / cm ² ). Thereafter, development was performed with a 1% sodium carbonate aqueous solution at 1 kgf / cm ² for 1 minute by spraying, and unexposed portions were dissolved and removed. Further, the test pieces obtained by thermosetting at 150 ° C. for 30 minutes were subjected to pencil hardness, resolution, solder heat resistance, chemical resistance, and reflow resistance test, and the results are shown in Table 2.
(Examples 2 to 6, Comparative Examples 1 and 2)

  According to the composition of Table 1, a photosensitive thermosetting resin composition and a flexible printed wiring board were produced by the same operation as in Example 1. Specifically, in Examples 2 and 3, instead of the biphenyl type epoxy resin of Example 1 as an epoxy resin, a cresol novolak type epoxy resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: EPICLONE N-670) was used. ), Bisphenol A type epoxy resin (manufactured by Dainippon Ink Co., Ltd., trade name: EPICLONE 1050), Examples 4 to 6 are bisphenol A type instead of bisphenol F type epoxy acrylate resins of Examples 1 to 3. An epoxy acrylate resin (Nippon Kayaku Co., Ltd., trade name: KAYARAD ZAR1035) is used.

  Comparative Example 1 uses a silane coupling agent (trade name: KBM573, manufactured by Shin-Etsu Chemical Co., Ltd.) instead of the imidazole silane of Example 1, and Comparative Example 2 uses the bisphenol F-type epoxy of Example 1. Instead of acrylate resin, urethane acrylate resin (Nippon Kayaku Co., Ltd., trade name: KAYARAD FLX2018) is used, and alicyclic epoxy resin (Nippon Kayaku Co., Ltd., trade name: AK601) is used as the epoxy resin. It is.

* 1: Pencil hardness was measured according to JIS K 5400.
* 2: The opening state was confirmed with an electron microscope.
* 3: A test piece was floated on a solder bath at 260 ° C. for 1 minute, and the presence or absence of swelling was observed and evaluated according to the following criteria.
○: No blistering or peeling, × ... Bulking or peeling * 4: Immerse the test piece in 10% sulfuric acid, 10% sodium hydroxide solution, isopropyl alcohol, methanol, methyl ethyl ketone at room temperature for 30 minutes, and visually check the appearance. .
○… Without swelling and peeling, ×… With swelling and peeling * 5: Preheating temperature 180 ± 5 ° C, peak temperature 240 ± 2 ° C, reflow temperature 230 ° C, preheating time 100 ± 20 seconds, reflow time 35 ± 5 seconds A reflow test was conducted under the conditions.
* 6: The appearance after the reflow test was visually confirmed.
○: Good (no change), ×: Conductor circuit turns brown * 7: After reflow test, in accordance with JIS D 0202, cross-cut to 100 mm, and the values adhered and held with cellophane tape were examined. .

  From these results, the present invention is a photosensitive thermosetting resin composition that is superior in reflow resistance while maintaining the same performance in terms of resolution, solder heat resistance, and chemical resistance as compared with the conventional one. It was confirmed to be a thing.

Claims (3)

(A) a bisphenol-type epoxy acrylate resin having a (meth) acryloyl group and a carboxyl group in one molecule and soluble in a dilute alkaline solution;
(B) an epoxy compound having two or more epoxy groups in one molecule;
(C) a photopolymerization initiator;
(D) a reactive diluent;
(E) a compound having an imidazole group and an alkoxysilyl group in one molecule;
An alkali developing negative photosensitive thermosetting resin composition characterized by comprising:   2. The alkali developing negative photosensitive heat according to claim 1, wherein the epoxy compound as the component (B) comprises at least one selected from a bisphenol type epoxy resin, a biphenyl type epoxy resin, and a novolac type epoxy resin. A curable resin composition.   A flexible printed wiring board comprising a protective film using the alkali development negative photosensitive thermosetting resin composition according to claim 1 on the surface.