JP6383525B2 - Pattern formation method, photosensitive thermosetting resin composition, dry film, and flexible printed wiring board - Google Patents

Description

  The present invention relates to a photosensitive thermosetting resin composition for a flexible printed wiring board, a dry film, and a flexible printed wiring board.

  In recent years, it has become necessary to reduce the space of circuit boards due to the small size and thinness of electronic devices due to the spread of smartphones and tablet terminals. Therefore, the use of the flexible printed wiring board which can be folded and accommodated is expanded, and the reliability with respect to such a flexible printed wiring board is required to be higher than ever.

  On the other hand, as an insulating film to ensure the insulation reliability of flexible printed wiring boards, a cover based on polyimide with excellent mechanical properties such as heat resistance and flexibility is used for the bent part (bent part). A lay is used (for example, refer to Patent Document 1), and a photosensitive resin composition that is excellent in electrical insulation and solder heat resistance and can be finely processed is used for a mounting portion (non-bent portion) (for example, a patent). Reference 2), the mixed loading process is widely adopted.

  That is, a polyimide-based coverlay having excellent mechanical properties such as heat resistance and flexibility is not suitable for fine wiring because it requires processing by die punching. Therefore, it is necessary to partially use an alkali developing type photosensitive resin composition (solder resist) that can be processed by photolithography in a chip mounting portion that requires fine wiring.

Japanese Patent Application Laid-Open No. Sho 62-263692 Japanese Unexamined Patent Publication No. 63-110224

  Thus, in the manufacturing process of a flexible printed wiring board, there was a problem that it was inferior in cost and workability because it was necessary to employ a mixed mounting process of a process of bonding a cover lay and a process of forming a solder resist.

  Conventionally, it has been proposed to apply an insulating film as a solder resist as a coverlay of a flexible printed wiring board for such a mixed mounting process. However, such a resin composition for a solder resist has insufficient reliability such as impact resistance and flexibility as a cover lay, and a process for collectively forming a bent portion (bent portion) and a mounting portion (non-bent portion). Has not yet been put to practical use. In addition, since the resin composition for solder resist is accompanied by curing shrinkage due to acrylic photopolymerization, there is a problem in dimensional stability such as warping of a flexible wiring board.

  On the other hand, as a photosensitive polyimide capable of achieving both alkali solubility and mechanical properties, a method of thermally ring-closing after patterning using a polyimide precursor has been proposed. However, problems remain in the workability of wiring board manufacture, such as requiring high-temperature treatment, and it has not yet been put into practical use. In addition, it is conceivable to apply an insulating film as a coverlay as a solder resist for a flexible printed wiring board. However, such a coverlay film requires a complicated process for pattern formation, and is not suitable for punching holes by punching. There is a problem that it is difficult to cope with the formation of a fine pattern due to low processing accuracy and oozing of the resin during thermocompression bonding.

  Accordingly, an object of the present invention is to provide an insulating film for a flexible printed wiring board, which has excellent reliability and processing accuracy such as impact resistance and flexibility, and excellent workability, particularly a bent portion (bent portion) and a mounting portion (non- An object of the present invention is to provide a photosensitive thermosetting resin composition for a flexible printed wiring board suitable for a batch forming process of bent portions. Furthermore, the object of the present invention is to provide a dry film having a resin layer made of the photosensitive thermosetting resin composition, and having the cured product as a protective film, for example, a cover lay or a solder resist, impact resistance, flexibility, etc. An object of the present invention is to provide a flexible printed wiring board having excellent reliability.

As a result of intensive research aimed at realizing the above object, the inventors have completed the present invention having the following contents.
That is, the photosensitive thermosetting resin composition for a flexible printed wiring board according to the present invention includes an alkali-soluble resin having an imide ring, a photobase generator, and a heat-reactive compound. .
Here, the photosensitive thermosetting resin composition for a flexible printed wiring board of the present invention is preferably used for at least one of a bent portion and a non-bent portion of the flexible printed wiring board. It is preferably used for forming at least one of a plate cover lay and a solder resist.

  It is preferable that the dry film of this invention has a resin layer which consists of a photosensitive thermosetting resin composition for the said flexible printed wiring boards.

  The flexible printed wiring board of this invention has the hardened | cured material which consists of the photosensitive thermosetting resin composition for the above-mentioned flexible printed wiring boards, or the resin layer of the above-mentioned dry film, It is characterized by the above-mentioned.

According to the present invention, an insulating film for a flexible printed wiring board having excellent reliability and processing accuracy such as impact resistance and flexibility, and excellent workability, particularly a bent portion (bending portion) and a mounting portion (non-bending portion). Part) can be provided. The photosensitive thermosetting resin composition for flexible printed wiring boards suitable for the batch forming process can be provided.
Furthermore, according to the present invention, a dry film having a resin layer made of a photosensitive thermosetting resin composition for flexible printed wiring boards, the cured product as a protective film, for example, a cover lay or a solder resist, It is possible to provide a flexible printed wiring board having excellent reliability such as flexibility and flexibility.

It is process drawing which shows typically an example of the manufacturing method of the flexible printed wiring board of this invention.

The photosensitive thermosetting resin composition for flexible printed wiring boards of the present invention (hereinafter sometimes abbreviated as “photosensitive thermosetting resin composition”) is an alkali-soluble resin having an imide ring, photobase generation. And a heat-reactive compound.
In the present invention, (1) using an alkali-soluble resin in which an imide ring is present in the molecule, and (2) adding an alkali-soluble resin and a thermosetting compound with a photobase generator to increase processing accuracy. An insulating film excellent in impact resistance and flex resistance, in particular, a cover lay and a solder resist can be formed at a time. Moreover, with the photosensitive thermosetting resin composition of the present invention, it is possible to obtain a coverlay and a solder resist that are excellent in low warpage and heat resistance.

Hereinafter, embodiments of the present invention will be described in detail.
The flexible printed wiring board which is the object of use of the photosensitive thermosetting resin composition of the present invention has a copper circuit formed on a flexible substrate.
The photosensitive thermosetting resin composition may be used for either one of the bent part and the non-bent part of the flexible printed wiring board, but is preferably used for both the bent part and the non-bent part. . The bent portion is a portion that is repeatedly bent and requires flexibility, and the non-bent portion is a portion that is not bent, such as a chip mounting portion.

[Alkali-soluble resin having an imide ring]
In the present invention, the alkali-soluble resin having an imide ring is one having an alkali-soluble group such as a carboxyl group or an acid anhydride group and an imide ring. For introducing the imide ring into the alkali-soluble resin, a known and usual method can be used. For example, the resin obtained by making a carboxylic anhydride component react with an amine component and / or an isocyanate component is mentioned. The imidization may be performed by thermal imidization or chemical imidization, and these can be used in combination.

  Here, examples of the carboxylic acid anhydride component include tetracarboxylic acid anhydrides and tricarboxylic acid anhydrides, but are not limited to these acid anhydrides, and acid anhydrides that react with amino groups or isocyanate groups. Any compound having a physical group and a carboxyl group can be used, including derivatives thereof. These carboxylic anhydride components may be used alone or in combination.

  Examples of the tetracarboxylic acid anhydride include pyromellitic dianhydride, 3-fluoropyromellitic dianhydride, 3,6-difluoropyromellitic dianhydride, 3,6-bis (trifluoromethyl) pyro Merit acid dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic acid Anhydride, 2,2′-difluoro-3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 5,5′-difluoro-3,3 ′, 4,4′-biphenyltetracarboxylic acid Anhydride, 6,6′-difluoro-3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 5,5 ′, 6,6′-hexafluoro-3,3 ′ , 4,4'-biphenyltet Carboxylic dianhydride, 2,2′-bis (trifluoromethyl) -3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 5,5′-bis (trifluoromethyl) -3, 3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 6,6′-bis (trifluoromethyl) -3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′ , 5,5′-tetrakis (trifluoromethyl) -3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 6,6′-tetrakis (trifluoromethyl) -3, 3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 5,5 ′, 6,6′-tetrakis (trifluoromethyl) -3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride , And 2,2 ', 5,5', 6,6 -Hexakis (trifluoromethyl) -3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3 ", 4,4 "-Terphenyltetracarboxylic dianhydride, 3,3 '", 4,4' "-quaterphenyltetracarboxylic dianhydride, 3,3" ", 4,4" "-kinkphenyltetracarboxylic acid Dianhydride, methylene-4,4′-diphthalic dianhydride, 1,1-ethynylidene-4,4′-diphthalic dianhydride, 2,2-propylidene-4,4′-diphthalic dianhydride 1,2-ethylene-4,4′-diphthalic dianhydride, 1,3-trimethylene-4,4′-diphthalic dianhydride, 1,4-tetramethylene-4,4′-diphthalic acid Anhydride, 1,5-pentamethylene-4,4'-diph Talic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, difluoromethylene-4,4′-diphthal Acid dianhydride, 1,1,2,2-tetrafluoro-1,2-ethylene-4,4′-diphthalic dianhydride, 1,1,2,2,3,3-hexafluoro-1, 3-trimethylene-4,4′-diphthalic dianhydride, 1,1,2,2,3,3,4,4-octafluoro-1,4-tetramethylene-4,4′-diphthalic dianhydride 1,1,2,2,3,3,4,4,5,5-decafluoro-1,5-pentamethylene-4,4′-diphthalic dianhydride, thio-4,4′- Diphthalic dianhydride, sulfonyl-4,4′-diphthalic dianhydride, 1,3-bis (3,4-dicarboxyphene) ) -1,1,3,3-tetramethylsiloxane dianhydride, 1,3-bis (3,4-dicarboxyphenyl) benzene dianhydride, 1,4-bis (3,4-dicarboxyphenyl) ) Benzene dianhydride, 1,3-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,3-bis [ 2- (3,4-Dicarboxyphenyl) -2-propyl] benzene dianhydride, 1,4-bis [2- (3,4-dicarboxyphenyl) -2-propyl] benzene dianhydride, bis [ 3- (3,4-dicarboxyphenoxy) phenyl] methane dianhydride, bis [4- (3,4-dicarboxyphenoxy) phenyl] methane dianhydride, 2,2-bis [3- (3,4- Dicarboxyphenoxy Phenyl] propane dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 2,2-bis [3- (3,4-dicarboxyphenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride, bis (3,4- Dicarboxyphenoxy) dimethylsilane dianhydride, 1,3-bis (3,4-dicarboxyphenoxy) -1,1,3,3-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalene Tetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic Acid dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid Anhydride, cyclopentanetetracarboxylic dianhydride, cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, 3,3 ′ , 4,4′-bicyclohexyltetracarboxylic dianhydride, carbonyl-4,4′-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, methylene-4,4′-bis (cyclohexane-1, 2-dicarboxylic acid) dianhydride, 1,2-ethylene-4,4′-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,1-ethynylidene-4,4′-bis (cyclohexane) San-1,2-dicarboxylic acid) dianhydride, 2,2-propylidene-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,1,1,3,3,3 -Hexafluoro-2,2-propylidene-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride Thio-4,4′-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, sulfonyl-4,4′-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, 3,3 ′ -Difluorooxy-4,4'-diphthalic dianhydride, 5,5'-difluorooxy-4,4'-diphthalic dianhydride, 6,6'-difluorooxy-4,4'-diphthalic acid Anhydride, 3, 3 ', 5, 5', 6 6′-hexafluorooxy-4,4′-diphthalic dianhydride, 3,3′-bis (trifluoromethyl) oxy-4,4′-diphthalic dianhydride, 5,5′-bis (tri Fluoromethyl) oxy-4,4′-diphthalic dianhydride, 6,6′-bis (trifluoromethyl) oxy-4,4′-diphthalic dianhydride, 3,3 ′, 5,5′- Tetrakis (trifluoromethyl) oxy-4,4′-diphthalic dianhydride, 3,3 ′, 6,6′-tetrakis (trifluoromethyl) oxy-4,4′-diphthalic dianhydride, 5, 5 ', 6,6'-tetrakis (trifluoromethyl) oxy-4,4'-diphthalic dianhydride, 3,3', 5,5 ', 6,6'-hexakis (trifluoromethyl) oxy- 4,4'-diphthalic dianhydride, 3,3'-diflu Orosulfonyl-4,4′-diphthalic dianhydride, 5,5′-difluorosulfonyl-4,4′-diphthalic dianhydride, 6,6′-difluorosulfonyl-4,4′-diphthalic dianhydride 3,3 ′, 5,5 ′, 6,6′-hexafluorosulfonyl-4,4′-diphthalic dianhydride, 3,3′-bis (trifluoromethyl) sulfonyl-4,4′- Diphthalic dianhydride, 5,5′-bis (trifluoromethyl) sulfonyl-4,4′-diphthalic dianhydride, 6,6′-bis (trifluoromethyl) sulfonyl-4,4′-diphthalic acid Dianhydride, 3,3 ′, 5,5′-tetrakis (trifluoromethyl) sulfonyl-4,4′-diphthalic dianhydride, 3,3 ′, 6,6′-tetrakis (trifluoromethyl) sulfonyl -4,4'-diphthalate Dianhydride, 5,5 ′, 6,6′-tetrakis (trifluoromethyl) sulfonyl-4,4′-diphthalic dianhydride, 3,3 ′, 5,5 ′, 6,6′-hexakis ( Trifluoromethyl) sulfonyl-4,4′-diphthalic dianhydride, 3,3′-difluoro-2,2-perfluoropropylidene-4,4′-diphthalic dianhydride, 5,5′-difluoro -2,2-perfluoropropylidene-4,4'-diphthalic dianhydride, 6,6'-difluoro-2,2-perfluoropropylidene-4,4'-diphthalic dianhydride, 3, 3 ′, 5,5 ′, 6,6′-hexafluoro-2,2-perfluoropropylidene-4,4′-diphthalic dianhydride, 3,3′-bis (trifluoromethyl) -2, 2-perfluoropropylidene-4,4'-diphthalate Acid dianhydride, 5,5′-bis (trifluoromethyl) -2,2-perfluoropropylidene-4,4′-diphthalic dianhydride, 6,6′-difluoro-2,2-perfluoro Propylidene-4,4′-diphthalic dianhydride, 3,3 ′, 5,5′-tetrakis (trifluoromethyl) -2,2-perfluoropropylidene-4,4′-diphthalic dianhydride 3,3 ′, 6,6′-tetrakis (trifluoromethyl) -2,2-perfluoropropylidene-4,4′-diphthalic dianhydride, 5,5 ′, 6,6′-tetrakis ( Trifluoromethyl) -2,2-perfluoropropylidene-4,4′-diphthalic dianhydride, 3,3 ′, 5,5 ′, 6,6′-hexakis (trifluoromethyl) -2,2 -Perfluoropropylidene-4,4'-diph Talic dianhydride, 9-phenyl-9- (trifluoromethyl) xanthene-2,3,6,7-tetracarboxylic dianhydride, 9,9-bis (trifluoromethyl) xanthene-2,3 6,7-tetracarboxylic dianhydride, bicyclo [2,2,2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 9,9-bis [4- (3 , 4-Dicarboxy) phenyl] fluorene dianhydride, 9,9-bis [4- (2,3-dicarboxy) phenyl] fluorene dianhydride, ethylene glycol bistrimellitic dianhydride, 1,2- ( Ethylene) bis (trimellitic anhydride), 1,3- (trimethylene) bis (trimellitic anhydride), 1,4- (tetramethylene) bis (trimellitic anhydride), 1,5- (pentamethylene) bis (trimetic anhydride) Retate anhydride), 1,6- (hexamethylene) bis (trimellitic anhydride), 1,7- (heptamethylene) bis (trimellitate anhydride), 1,8- (octamethylene) bis (trimellitic anhydride), 1,9- (nonamethylene) bis (trimellitic anhydride), 1,10- (decamethylene) bis (trimellitic anhydride), 1,12- (dodecamethylene) bis (trimellitic anhydride), 1,16- (hexadeca) Methylene) bis (trimellitate anhydride), 1,18- (octadecamethylene) bis (trimellitate anhydride), and the like.

  Examples of the tricarboxylic acid anhydride include trimellitic acid anhydride and nuclear hydrogenated trimellitic acid anhydride.

  Examples of the amine component include diamines such as aliphatic diamines and aromatic diamines, and polyvalent amines such as aliphatic polyether amines, but are not limited to these amines. These amine components may be used alone or in combination.

  Examples of the diamine include p-phenylenediamine (PPD), 1,3-diaminobenzene, 2,4-toluenediamine, 2,5-toluenediamine, 2,6-toluenediamine, 3,5-diaminobenzoic acid, One diamine nucleus diamine such as 2,5-diaminobenzoic acid and 3,4-diaminobenzoic acid, diaminodiphenyl ether such as 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, and 3,4′-diaminodiphenyl ether 4,4′-diaminodiphenylmethane, 3,3′-dimethyl-4,4′-diaminobiphenyl, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-bis (trifluoromethyl ) -4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiph Nilmethane, 3,3′-dicarboxy-4,4′-diaminodiphenylmethane, 3,3 ′, 5,5′-tetramethyl-4,4′-diaminodiphenylmethane, bis (4-aminophenyl) sulfide, 4, 4'-diaminobenzanilide, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine (o-tolidine), 2,2'-dimethylbenzidine (m-tolidine), 3,3'-dimethoxybenzidine, 2 , 2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4 , 4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyls Hong, 3,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 3,3′-diamino-4,4′-dichlorobenzophenone, 3,3′-diamino- 4,4′-dimethoxybenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 2,2-bis (3-aminophenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-bis (4-aminophenyl) -1, 1,1,3,3,3-hexafluoropropane, 3,3′-diaminodiphenyl sulfoxide, 3,4′-diaminodiphenyl sulfone Xoxide, 4,4′-diaminodiphenyl sulfoxide, 3,3′-dicarboxy-4,4′-diaminodiphenylmethane, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 3,3 ′ -Two diamine diamines such as diamino-4,4'-dihydroxydiphenylsulfone, 1,3-bis (3-aminophenyl) benzene, 1,3-bis (4-aminophenyl) benzene, 1,4-bis (3-aminophenyl) benzene, 1,4-bis (4-aminophenyl) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4 -Bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) -4-trifluoromethylbenzene, 3,3 ' -Diamino-4- (4-phenyl) phenoxybenzophenone, 3,3'-diamino-4,4'-di (4-phenylphenoxy) benzophenone, 1,3-bis (3-aminophenyl sulfide) benzene, 1, 3-bis (4-aminophenyl sulfide) benzene, 1,4-bis (4-aminophenyl sulfide) benzene, 1,3-bis (3-aminophenylsulfone) benzene, 1,3-bis (4-aminophenyl) Sulfone) benzene, 1,4-bis (4-aminophenylsulfone) benzene, 1,3-bis [2- (4-aminophenyl) isopropyl] benzene, 1,4-bis [2- (3-aminophenyl) Isopropyl] benzene, 1,4-bis [2- (4-aminophenyl) isopropyl] benzene, 1,3-bis (4-amino-3-hydroxy) Ciphenoxy) benzene nucleus three diamines such as benzene, 3,3′-bis (3-aminophenoxy) biphenyl, 3,3′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-amino Phenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [3- (3-aminophenoxy) phenyl] ether, bis [3- (4-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, bis [3- (3-aminophenoxy) phenyl] ketone, bis [3- (4-aminophenoxy) phenyl] Ketone, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl ] Ketone, bis [3- (3-aminophenoxy) phenyl] sulfide, bis [3- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- ( 4-aminophenoxy) phenyl] sulfide, bis [3- (3-aminophenoxy) phenyl] sulfone, bis [3- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone Bis [4- (4-aminophenoxy) phenyl] sulfone, bis [3- (3-aminophenoxy) phenyl] methane, bis [3- (4-aminophenoxy) phenyl] methane, bis [4- (3- Aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] methane, 2,2- [3- (3-aminophenoxy) phenyl] propane, 2,2-bis [3- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane 2,2-bis [3- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, etc. Four benzene nuclei Aromatic diamines such as diamine, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1 Aliphatic diamines such as 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, and the like. Examples of the polyether amine include ethylene glycol and / or propylene glycol-based polyvalent amine.

Diisocyanates such as aromatic diisocyanates and isomers and multimers, aliphatic diisocyanates, alicyclic diisocyanates and isomers thereof, and other general-purpose diisocyanates can be used as the isocyanate component. It is not limited. These isocyanate components may be used alone or in combination.
Examples of diisocyanates include aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, biphenyl diisocyanate, diphenyl sulfone diisocyanate, diphenyl ether diisocyanate, and isomers, multimers, hexamethylene diisocyanate, isophorone. Examples thereof include aliphatic diisocyanates such as diisocyanate, dicyclohexylmethane diisocyanate, and xylylene diisocyanate, alicyclic diisocyanates and isomers obtained by hydrogenation of the aromatic diisocyanate, and other general-purpose diisocyanates.

  The alkali-soluble resin having an imide ring as described above may have an amide bond. This may be an amide bond obtained by reacting an isocyanate and a carboxylic acid, or may be caused by other reaction. Furthermore, you may have the coupling | bonding which consists of another addition and condensation.

  In addition, for the introduction of the imide ring into the alkali-soluble resin, a known and commonly used alkali-soluble polymer, oligomer or monomer having a carboxyl group and / or an acid anhydride group may be used. It may be a resin obtained by reacting an alkali-soluble resin alone or in combination with the above carboxylic anhydride component and reacting with the above amine / isocyanate.

  In the synthesis of such an alkali-soluble resin having an alkali-soluble group and an imide ring, a known and commonly used organic solvent can be used. Such an organic solvent is not particularly limited as long as it is a solvent that does not react with the carboxylic acid anhydrides, amines, and isocyanates that are raw materials and that dissolves these raw materials, and the structure is not particularly limited. Specifically, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone , Cyclic ester solvents such as α-methyl-γ-butyrolactone, carbonate solvents such as ethylene carbonate and propylene carbonate, lactam solvents such as caprolactam, ether solvents such as dioxane, glycol solvents such as triethylene glycol, m-cresol, Phenolic solvents such as p-cresol, 3-chlorophenol, 4-chlorophenol, 4-methoxyphenol, 2,6-dimethylphenol, acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl Sulfo Sid, such as tetramethylurea. Furthermore, other common organic solvents such as phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran , Dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, terpene, mineral spirit, petroleum naphtha solvents, etc. Can also be used. Of these, aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and γ-butyrolactone are preferred because of the high solubility of the raw materials.

  The alkali-soluble resin having an alkali-soluble group such as a carboxyl group or an acid anhydride group and an imide ring as described above has an acid value of 20 to 200 mgKOH / g in order to cope with the photolithography process. Is more preferable, and 60 to 150 mgKOH / g is more preferable. When the acid value is 20 mgKOH / g or more, the solubility in alkali increases, the developability becomes good, and further, the degree of crosslinking with the thermosetting component after light irradiation becomes high, so that sufficient development contrast is obtained. be able to. When the acid value is 200 mgKOH / g or less, so-called heat fogging in a PEB (POST EXPOSURE BAKE) step after light irradiation described later can be suppressed, and the process margin is increased.

The molecular weight of the alkali-soluble resin is preferably from 1,000 to 100,000, more preferably from 2,000 to 50,000, considering developability and cured coating properties.
When the molecular weight is 1,000 or more, sufficient development resistance and cured properties can be obtained after exposure and PEB. On the other hand, when the molecular weight is 100,000 or less, alkali solubility increases and developability improves.

(Photobase generator)
In the present invention, the photobase generator can function as a catalyst for the polymerization reaction of a thermoreactive compound, which will be described later, when the molecular structure is changed by light irradiation such as ultraviolet light or visible light, or when the molecule is cleaved. It is a compound that produces more than one kind of basic substance. Examples of basic substances include secondary amines and tertiary amines.
Examples of photobase generators include α-aminoacetophenone compounds, oxime ester compounds, acyloxyimino groups, N-formylated aromatic amino groups, N-acylated aromatic amino groups, nitrobenzyl carbamate groups, and alkoxyoxybenzyl carbamates. And compounds having a substituent such as a group. Of these, oxime ester compounds and α-aminoacetophenone compounds are preferred. As the α-aminoacetophenone compound, those having two or more nitrogen atoms are particularly preferable.

  Other photobase generators include WPBG-018 (trade name: 9-anthrylmethylN, N'-diethylcarbamate), WPBG-027 (trade name: (E) -1- [3- (2-hydroxyphenyl) -2-propenoyl ] piperidine), WPBG-082 (trade name: guanidinium2- (3-benzoylphenyl) propionate), WPBG-140 (trade name: 1- (anthraquinon-2-yl) ethyl imidazolecarboxylate), and the like can also be used.

  The α-aminoacetophenone compound has a benzoin ether bond in the molecule, and when irradiated with light, cleavage occurs in the molecule to produce a basic substance (amine) that exhibits a curing catalytic action. Specific examples of the α-aminoacetophenone compound include (4-morpholinobenzoyl) -1-benzyl-1-dimethylaminopropane (Irgacure 369, trade name, manufactured by BASF Japan Ltd.) and 4- (methylthiobenzoyl) -1-methyl. -1-morpholinoethane (Irgacure 907, trade name, manufactured by BASF Japan Ltd.), 2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl]- A commercially available compound such as 1-butanone (Irgacure 379, trade name, manufactured by BASF Japan Ltd.) or a solution thereof can be used.

  Any oxime ester compound can be used as long as it is a compound that generates a basic substance by light irradiation. Examples of such oxime ester compounds include CGI-325, Irgacure OXE01, Irgacure OXE02 manufactured by BASF Japan, N-1919, and NCI-831 manufactured by Adeka. Moreover, the compound which has two oxime ester groups in the molecule | numerator described in the patent 4344400 gazette can also be used suitably.

  In addition, JP-A-2004-359639, JP-A-2005-097141, JP-A-2005-220097, JP-A-2006-160634, JP-A-2008-094770, JP-A-2008-509967, Specific examples include carbazole oxime ester compounds described in JP2009-040762A and JP2011-80036A.

  Such a photobase generator may be used individually by 1 type, and may be used in combination of 2 or more type. The compounding amount of the photobase generator in the thermosetting resin composition is preferably 0.1 to 40 parts by mass, more preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the thermoreactive compound. It is. In the case of 0.1 part by mass or more, the development resistance contrast of the light irradiated part / non-irradiated part can be obtained satisfactorily. Moreover, in 40 mass parts or less, hardened | cured material characteristic improves.

(Thermo-reactive compound)
In the present invention, the heat-reactive compound has a functional group capable of undergoing a curing reaction with the alkali-soluble group of the alkali-soluble resin by heat. As the thermally reactive compound, for example, a compound having a cyclic (thio) ether group is preferable, and examples thereof include an epoxy resin and a polyfunctional oxetane compound.

  The epoxy resin is a resin having an epoxy group, and any known one can be used. Examples thereof include a bifunctional epoxy resin having two epoxy groups in the molecule, and a polyfunctional epoxy resin having many epoxy groups in the molecule. In addition, a hydrogenated bifunctional epoxy compound may be used.

  Polyfunctional epoxy compounds include bisphenol A type epoxy resin, brominated epoxy resin, novolac type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, alicyclic ring Epoxy resin, trihydroxyphenylmethane type epoxy resin, bixylenol type or biphenol type epoxy resin or a mixture thereof; bisphenol S type epoxy resin, bisphenol A novolak type epoxy resin, tetraphenylolethane type epoxy resin, heterocyclic epoxy Resin, diglycidyl phthalate resin, tetraglycidyl xylenoyl ethane resin, naphthalene group-containing epoxy resin, epoxy resin having dicyclopentadiene skeleton, glycidyl meta Acrylate copolymer epoxy resins, copolymerized epoxy resins of cyclohexylmaleimide and glycidyl methacrylate, and a CTBN modified epoxy resin.

  Other liquid bifunctional epoxy resins include vinylcyclohexene diepoxide, (3 ′, 4′-epoxycyclohexylmethyl) -3,4-epoxycyclohexanecarboxylate, and (3 ′, 4′-epoxy-6′-methyl). And alicyclic epoxy resins such as (cyclohexylmethyl) -3,4-epoxy-6-methylcyclohexanecarboxylate. These epoxy resins may be used individually by 1 type, and may use 2 or more types together.

  In addition, you may mix | blend well-known and usual compounds, such as a maleimide compound, a block isocyanate compound, an amino resin, a benzoxazine resin, a carbodiimide resin, a cyclocarbonate compound, an episulfide resin, as a heat-reactive compound.

  As a compounding quantity of the said thermoreactive compound, equivalent ratio (alkali-soluble groups, such as a carboxyl group: thermal-reactive groups, such as an epoxy group) with alkali-soluble resin is 1: 0.1 to 1:10. It is preferable. By setting the blending ratio in such a range, development becomes favorable and a fine pattern can be easily formed. The equivalent ratio is more preferably 1: 0.2 to 1: 5.

(Polymer resin)
The photosensitive thermosetting resin composition of the present invention can be blended with conventionally known polymer resins for the purpose of improving the flexibility and dryness of the touch of the resulting cured product. Examples of the polymer resin include cellulose, polyester, phenoxy resin, polyvinyl acetal, polyvinyl butyral, polyamide, polyamideimide binder polymer, block copolymer, elastomer and the like. The above polymer resins may be used alone or in combination of two or more.

(Inorganic filler)
An inorganic filler can be blended in the photosensitive thermosetting resin composition of the present invention. An inorganic filler is used in order to suppress the curing shrinkage of the cured product of the photosensitive thermosetting resin composition and to improve properties such as adhesion and hardness. Examples of the inorganic filler include barium sulfate, amorphous silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, boron nitride, and Neuburg Examples include rich earth. The said inorganic filler may be used individually by 1 type, and may use 2 or more types together.

(Coloring agent)
Furthermore, a coloring agent can be mix | blended with the photosensitive thermosetting resin composition of this invention. As the colorant, conventionally known colorants such as red, blue, green, yellow, white, and black can be used, and any of pigments, dyes, and pigments may be used.

(Organic solvent)
In the photosensitive thermosetting resin composition of the present invention, an organic solvent can be used for preparing the resin composition and adjusting the viscosity for application to a substrate or a carrier film.
Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum solvents, and the like. Such an organic solvent may be used individually by 1 type, and may be used as a 2 or more types of mixture.

(Other optional ingredients)
The photosensitive thermosetting resin composition of the present invention may further contain components such as a photopolymerizable monomer, a mercapto compound, an adhesion promoter, an antioxidant, and an ultraviolet absorber as necessary. As these, those known in the field of electronic materials can be used. The photosensitive thermosetting resin composition includes a known and commonly used thickener such as finely divided silica, hydrotalcite, organic bentonite, and montmorillonite, an antifoaming agent such as silicone, fluorine, and polymer. // Known additives such as a leveling agent, a silane coupling agent, and a rust preventive agent can be blended.
In addition, the compounding amount of the photopolymerizable monomer is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and 0 parts by mass (included) with respect to 100 parts by mass of the alkali-soluble resin. Most preferred).

[Dry film]
The dry film of the present invention has a resin layer made of the photosensitive thermosetting resin composition of the present invention.
In forming a dry film, for example, the photosensitive thermosetting resin composition of the present invention is diluted with an organic solvent to adjust to an appropriate viscosity, and a uniform thickness is formed on the carrier film by a known method such as a comma coater. Apply. Thereafter, drying is usually performed at a temperature of 50 to 130 ° C. for 1 to 30 minutes to form a resin layer on the carrier film.

  A plastic film is used as the carrier film. Although there is no restriction | limiting in particular about the thickness of a carrier film, Generally, it selects suitably in the range of 10-150 micrometers. After forming the resin layer on the carrier film, a peelable cover film may be further laminated on the surface of the resin layer.

[Flexible printed wiring board and manufacturing method thereof]
The flexible printed wiring board of the present invention is characterized by having a cured product composed of a photosensitive thermosetting resin composition or a resin layer of a dry film.
The method for producing a flexible printed wiring board of the present invention includes a step of forming a resin layer made of a photosensitive thermosetting resin composition on a flexible printed wiring board, a step of irradiating the resin layer with light in a pattern, and a resin layer. A step of heating, and a step of alkali-developing the resin layer to form at least one of a coverlay and a solder resist.

[Resin layer forming step]
In this step, at least one resin layer made of a photosensitive thermosetting resin composition is formed on the flexible printed wiring board.
Examples of the method for forming the resin layer include a coating method and a laminating method.
In the case of the application method, the photosensitive thermosetting resin composition is applied onto the flexible printed wiring board by a method such as screen printing and dried to form a resin layer.
In the case of the laminating method, first, the photosensitive thermosetting resin composition is diluted with an organic solvent to adjust to an appropriate viscosity, and coated on a carrier film and dried to prepare a dry film having a resin layer. Next, after bonding together so that a resin layer may contact a flexible printed wiring board with a laminator etc., a carrier film is peeled.

  Moreover, another layer can be interposed between the resin layer and the flexible printed wiring board. The other layer is preferably made of an alkali development type photosensitive resin composition. As an alkali development type photosensitive resin composition, a well-known composition can be used, For example, the well-known composition for coverlays or a soldering resist can be used. Thus, by setting it as the laminated structure including another layer, the hardened | cured material which was further excellent in impact resistance and flexibility can be obtained.

[Light irradiation process]
This step activates the photobase generator contained in the resin layer by light irradiation in a negative pattern to cure the light irradiation part. In this step, the photobase generator is destabilized by the base generated in the light irradiation part, and the base is chemically proliferated, whereby the resin layer can be sufficiently cured to the deep part.

As the light irradiator, a direct writer, a light irradiator equipped with a metal halide lamp, or the like can be used. The patterned light irradiation mask is a negative mask.
As the active energy ray used for light irradiation, it is preferable to use laser light or scattered light having a maximum wavelength in the range of 350 to 450 nm. By setting the maximum wavelength within this range, the photobase generator can be activated efficiently. If a laser beam in this range is used, either a gas laser or a solid laser may be used. Moreover, although the light irradiation amount changes with film thicknesses etc., it can generally be set as 100-1500 mJ / cm < ² >.

[Heating process]
In this step, after the light irradiation, the light irradiation part is cured by heating the resin layer. By this process, it is possible to cure to a deep part by the base generated in the light irradiation process. The heating temperature is, for example, 80 to 140 ° C. The heating time is, for example, 10 to 100 minutes.
Since the curing of the photosensitive thermosetting resin composition in the present invention is, for example, a ring-opening reaction of an epoxy resin by a thermal reaction, it can suppress distortion and curing shrinkage compared to the case where curing proceeds by a photoradical reaction. it can.

[Development process]
In the development step, the unirradiated portion is removed by alkali development to form a negative patterned insulating film, particularly a coverlay and a solder resist.
The developing method can be a known method such as dipping. Moreover, as a developing solution, alkaline water solution, such as potassium hydroxide, amines, tetramethylammonium hydroxide aqueous solution (TMAH), or these liquid mixture can be used.
Note that the insulating film may be further irradiated with light after the development step. For example, you may heat at 150 degreeC or more.

  Next, an example of a method for producing the flexible printed wiring board of the present invention from the photosensitive thermosetting resin composition of the present invention will be described based on the process diagram of FIG. FIG. 1 shows a case where the resin layer has a laminated structure, but it may be composed of only one layer.

In the laminating process of FIG. 1, a laminated structure composed of the resin layer 3 and the resin layer 4 is formed on the flexible printed wiring substrate 1 on which the copper circuit 2 is formed.
The resin layer 3 is made of an alkali development type photosensitive resin composition containing a carboxyl group-containing resin or the like.
The resin layer 4 is formed on the resin layer 3 and includes an alkali-soluble resin having one or more imide rings and one or more carboxyl groups in one molecule, a photobase generator, and a thermally reactive compound. It consists of a photosensitive thermosetting resin composition.

  The light irradiation process of FIG. 1 activates the photobase generator contained in the photosensitive thermosetting resin composition by disposing a mask 5 on the resin layer 4 and irradiating light in a negative pattern. This is a step of curing the light irradiation part. The heating process of FIG. 1 is a process of curing the light irradiation part by heating the resin layer after the light irradiation process. The development process in FIG. 1 is a process in which an unirradiated portion is removed by developing with an alkaline aqueous solution, and a negative pattern layer is formed.

  In addition, the 2nd light irradiation process of FIG. 1 is a process for activating the remaining photobase generator as needed, and generating a base, and a thermosetting process is a pattern layer as needed. This is a process for sufficient heat curing.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited by these Examples and a comparative example.

(Examples 1-4, Comparative Example 1)
<Synthesis example of an alkali-soluble resin having an imide ring>
In a separable three-necked flask equipped with a stirrer, nitrogen inlet tube, fractional ring, and cooling ring, 12.5 g of 3,5-diaminobenzoic acid, 2,2′-bis [4- (4-aminophenoxy) Phenyl] propane (8.2 g), NMP (30 g), γ-butyrolactone (30 g), 4,4′-oxydiphthalic anhydride (27.9 g) and trimellitic anhydride (3.8 g) were added at room temperature under a nitrogen atmosphere at 100 rpm. Stir for 4 hours. Next, 20 g of toluene was added and stirred for 4 hours while distilling off toluene and water at a silicon bath temperature of 180 ° C. and 150 rpm to obtain an alkali-soluble resin solution having an imide ring.

<Preparation of photosensitive thermosetting resin composition>
In accordance with the formulation shown in Table 1 below, the materials described in the examples were respectively mixed, preliminarily mixed with a stirrer, and then kneaded with a three-roll mill to prepare a photosensitive thermosetting resin composition. The values in the table are parts by mass unless otherwise specified.

<Lower layer formation process>
A flexible printed wiring substrate in which a circuit was formed with a copper thickness of 18 μm was prepared, and pre-treatment was performed using MEC CZ-8100. Thereafter, the photosensitive thermosetting resin compositions of Examples 1 and 2 and Comparative Example 1 were each dried to 20 μm after drying by the coating method shown in Table 1 on the pre-treated flexible printed wiring board. Coating was performed. Then, it dried at 90 degreeC / 30 minutes with the hot-air circulation type drying furnace, and formed the lower layer. In Examples 3 and 4, the lower layer was not formed.

<Resin layer formation process>
The photosensitive thermosetting resin compositions of Examples 1 and 2 were coated on the lower layer by the coating method shown in Table 1 so as to be 10 μm after drying. Then, it dried at 90 degreeC / 30 minutes with the hot-air circulation type drying furnace, and formed the resin layer. In Examples 3 and 4, a resin layer was formed on the flexible printed wiring board after the surface treatment in the same manner as in Example 1. In Comparative Example 1, no resin layer was formed.

<Developability (patterning) and evaluation of curing characteristics>
In Examples 1 and 2, with respect to the flexible printed wiring board provided with the lower layer and the resin layer obtained as described above, a negative pattern with an exposure amount shown in Table 1 by ORC HMW680GW (metal halide lamp, scattered light). Was irradiated with light. Next, heat treatment was performed at 90 ° C. for 60 minutes. Thereafter, the substrate was immersed in a 1% by mass sodium carbonate aqueous solution at 30 ° C. and developed for 3 minutes to evaluate the developability. In Examples 3 and 4, the possibility of developability was evaluated in the same manner as in Example 1 for the flexible printed wiring board including the resin layer obtained above. In Comparative Example 1, the possibility of developability was evaluated in the same manner as in Example 1 for the flexible printed wiring board provided with the lower layer obtained above. The obtained results are shown in Table 1.

  Next, heat treatment was performed at 150 ° C./60 minutes using a hot air circulation drying oven to obtain a patterned cured coating film. An MIT test (R = 0.38 mm / upilex 12.5 μm base material manufactured by Ube Industries, Ltd.) and a surface hardness test (pencil hardness test) were conducted on the obtained cured coating film, and the flexibility and surface Hardness (impact resistance) was evaluated. The obtained results are shown in Table 1 below.

＊１酸価８６ｍｇＫＯＨ／ｇ Ｍｗ：１００００
＊２ビスフェノールＡ型エポキシ樹脂(分子量：３８０）（三菱化学(株)製）
＊３オキシム型光重合開始剤（ＢＡＳＦ社製）
＊４ビスフェノールＦ型エポキシアクリレート（日本化薬(株)製）
＊５トリメチロールプロパンＥＯ 変性トリアクリレート（東亞合成(株)製）
＊６ビスフェノールＡ型エポキシ樹脂(分子量：９００）（三菱化学(株)製）
＊７ビスフェノールＡ型エポキシ樹脂(分子量：５００）（三菱化学(株)製）
＊８アシルフォスフィンオキサイド系光重合開始剤 (ＢＡＳＦ社製)

* 1 Acid value 86 mg KOH / g Mw: 10,000
* 2 Bisphenol A type epoxy resin (Molecular weight: 380) (Mitsubishi Chemical Corporation)
* 3 Oxime-type photopolymerization initiator (BASF)
* 4 Bisphenol F epoxy acrylate (manufactured by Nippon Kayaku Co., Ltd.)
* 5 Trimethylolpropane EO modified triacrylate (manufactured by Toagosei Co., Ltd.)
* 6 Bisphenol A epoxy resin (Molecular weight: 900) (Mitsubishi Chemical Corporation)
* 7 Bisphenol A type epoxy resin (Molecular weight: 500) (Mitsubishi Chemical Corporation)
* 8 Acylphosphine oxide photopolymerization initiator (BASF)

  From the evaluation results shown in Table 1, the flexible printed wiring boards of Examples 1 to 4 can form fine patterns in the same manner as the flexible printed wiring board of Comparative Example 1, and have flexibility and impact resistance (surface hardness). Can be seen to be significantly better.

DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board 2 Copper circuit 3 Resin layer 4 Resin layer 5 Mask

Claims (6)

Pattern forming method for insulating film of flexible printed wiring board using photosensitive thermosetting resin composition containing alkali-soluble resin having imide ring, photobase generator, and thermoreactive compound, and not containing photopolymerizable monomer Because
The alkali-soluble resin having an imide ring comprises a reaction product of a tetracarboxylic acid anhydride or a tricarboxylic acid anhydride and a diamine, a polyvalent amine and / or an isocyanate component,
The thermoreactive compound has a functional group capable of thermosetting reaction with an alkali-soluble group of the alkali-soluble resin,
The photobase generator is activated by light irradiation, the basic substance generated in the light irradiation part is used as a catalyst, and the alkali-soluble resin and the heat-reactive compound are subjected to an addition reaction by heating to form a light irradiation part. A pattern forming method comprising removing an unirradiated portion by alkali development after curing.   The pattern formation method of Claim 1 used for formation of the insulating film of at least any one of the bending part of a flexible printed wiring board, and a non-bending part.   The pattern formation method of Claim 1 or 2 used in order to form at least any one of the coverlay and soldering resist of a flexible printed wiring board.   A composition containing an alkali-soluble resin having an imide ring, a photobase generator, and a heat-reactive compound, which is used in the pattern formation method according to claim 1, and does not contain a photopolymerizable monomer. The alkali-soluble resin having an imide ring is a reaction product of a tetracarboxylic acid anhydride or tricarboxylic acid anhydride and a diamine, a polyvalent amine and / or an isocyanate component, and the thermally reactive compound is A photosensitive thermosetting resin composition having a functional group capable of thermosetting reaction with an alkali-soluble group of the alkali-soluble resin.   A dry film comprising a resin layer comprising the photosensitive thermosetting resin composition according to claim 4. A flexible printed wiring board comprising the photosensitive thermosetting resin composition according to claim 4 or a cured product comprising the resin layer of the dry film according to claim 5.

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