JP2011017898A - Photosensitive cover lay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive cover lay capable of suppressing warpage of a laminate with a flexible printed board after curing.SOLUTION: The photosensitive cover lay comprises at least (A) an epoxy compound represented by general formula (1), (B) a soluble polyimide, (C) a photopolymerizable compound, and (D) a photopolymerization initiator, wherein X denotes a divalent linking group, and n and m each denote 1-10, provided that n+m≥4.

Description

  The present invention relates to a photosensitive coverlay.

  Conventionally, a coverlay film obtained by applying an adhesive to a molded body such as a polyimide film has been used as a protective film or an insulating film of a flexible printed circuit board. As a method for patterning a coverlay film, punching by punching has been generally used. However, in recent years, miniaturization of wiring and miniaturization of chip parts mounted on a flexible printed circuit board make it difficult to cope with the miniaturization by such processing. Therefore, in order to realize fine pattern processing, there is a demand for a photosensitive cover lay utilizing photographic technology.

  Acrylic resin is listed as a photosensitive material with excellent developability. However, heat resistance and insulation are insufficient, and electrical / electronics such as protective films and insulating films for semiconductor elements, flexible wiring boards, rigid boards, integrated circuits, etc. Not suitable for use. Therefore, a photosensitive cover lay using a polyimide resin having excellent electrical characteristics, chemical resistance, and heat resistance has been studied.

  As a photosensitive resin composition that can be developed with an alkaline aqueous solution, for example, a photosensitive polyimide resin obtained by reacting a polyimide resin containing a hydroxyl group with a compound having a carbon-carbon double bond, and a (meth) acrylic compound, , A photosensitive resin composition containing a photoreaction initiator and / or a sensitizer (see, for example, Patent Document 1), a photosensitive resin that cures after coating, drying, exposure, and alkali development on the surface of a printed wiring board In the composition, a photosensitive resin composition (see, for example, Patent Document 2) that can be developed with an aqueous sodium carbonate solution of 0.8% by weight or less in an alkali development step has been proposed. However, these photosensitive resin compositions have a problem of large warpage after curing.

  On the other hand, as an adhesive composition, an adhesive composition containing a thermoplastic resin having a carboxyl group and / or a hydroxyl group, a compound having an oxazoline group in the molecule and a thermosetting resin (see, for example, Patent Document 3), An adhesive composition containing a polyimide resin having a carboxyl group in the side chain, a photocurable resin, a photopolymerization initiator, and a polyfunctional epoxy compound (see, for example, Patent Document 4) has been proposed. However, the adhesive sheet obtained by curing these adhesive compositions also has a problem of large warpage.

JP 2004-325616 A JP 2008-197544 A JP 2008-260907 A JP 2008-274269 A

  This invention makes it a subject to provide the photosensitive coverlay which can reduce the curvature of a laminated body with the flexible printed circuit board after hardening.

  The present invention comprises at least (A) an epoxy compound represented by the following general formula (1), (B) a soluble polyimide, (C) a photopolymerizable compound, and (D) a photopolymerization initiator. It is a photosensitive coverlay.

  In the general formula (1), X represents a divalent linking group. n and m each represent a range of 1 to 10. However, n + m ≧ 4.

  By this invention, the photosensitive coverlay with a small curvature of the laminated body with the flexible printed circuit board after hardening can be obtained.

  The photosensitive coverlay of the present invention comprises (A) an epoxy compound represented by the general formula (1), (B) a soluble polyimide, (C) a photopolymerizable compound, and (D) a photopolymerization initiator. In addition, the coverlay in this invention points out the material which protects the wiring of a flexible printed circuit board, it hardens and is used as a protective film. The shape before curing is not limited, and examples thereof include a varnish shape and a film shape. The flexible printed circuit board is one in which conductor wiring is formed on an insulating resin film layer. For example, although the board | substrate with which the polyimide film and copper foil were laminated | stacked directly or via adhesives, such as an epoxy resin and a polyimide resin, and the copper foil was circuit-processed is mentioned, it is not limited to these.

The epoxy compound (A) represented by the following general formula (1) in the present invention is a compound having two epoxy groups and four or more propylene oxides (—C ₃ H ₆ O—) in the molecule. . As such an epoxy compound, “Adeka Resin (registered trademark)” EP-4003S (manufactured by Adeka Co., Ltd.), PG207GS (manufactured by Toto Kasei Co., Ltd.) and the like can be mentioned.

  In the general formula (1), X represents a divalent linking group. n and m each represent a range of 1 to 10. However, n + m ≧ 4.

By having an epoxy group, the solder heat resistance after curing of the photosensitive coverlay can be improved, and the adhesion to the flexible printed circuit board can be improved. Furthermore, by setting n + m ≧ 4, that is, by having four or more propylene oxide (—C ₃ H ₆ O—) skeletons, the elastic modulus after curing of the photosensitive coverlay is reduced, and The warpage of the laminate can be reduced. In the ethylene oxide (—C ₂ H ₄ O—) skeleton similar to the propylene oxide skeleton, such a warp reduction effect cannot be obtained. Further, even when the number of propylene oxide skeletons is less than 4, such a warp reduction effect cannot be obtained. The propylene group is preferably branched, and the value of n + m is preferably 5 or more. By containing such a compound, the curvature of the laminated body with the flexible printed circuit board after hardening can be reduced more, and the developability with respect to alkaline aqueous solution can be improved.

X in the general formula (1) represents a divalent linking group and may be a single bond. It preferably has an aromatic ring, and developability with an alkali solution, particularly 1 wt% sodium carbonate is improved. Two or more aromatic rings are represented by —CH ₂ —, —C (CH ₃ ) ₂ —, —O—, —CO—, —SO ₂ —, —S—, —NHCO—, —C (CF ₃ ) ₂ —. Or the thing connected by -COO- is more preferable, and it is more preferable that the epoxy compound represented by General formula (1) has a bisphenol A frame | skeleton. By containing such a compound, the elasticity modulus after hardening of a photosensitive coverlay can be reduced, and the curvature of a laminated body with a flexible printed circuit board can be reduced more. Moreover, the developability with respect to the 1 wt% sodium carbonate aqueous solution can be improved.

  The (B) soluble polyimide in the present invention is an amide solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, N-vinylpyrrolidone, N, N-diethylformamide, γ-butyrolactone, methyl monoglyme, methyl diglyme, methyl triglyme, ethyl monoglyme, ethyl diglyme, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol dimethyl ether, This refers to those that dissolve 1 g or more at 25 ° C. with respect to 100 g of any organic solvent such as ethylene glycol diethyl ether.

  (B) The soluble polyimide has an acid anhydride residue and a diamine residue. In the present invention, it is preferable that the pyromellitic dianhydride residue has 10 mol% or more of the total acid dianhydride residue. Thereby, the developability with respect to the 1 wt% sodium carbonate aqueous solution can be improved. 30 mol% or more is more preferable, and 50 mol% or more is more preferable.

  (B) The soluble polyimide may have other acid anhydride residues in addition to the pyromellitic dianhydride residue or in place of the pyromellitic dianhydride residue. Examples of acid anhydrides constituting other acid anhydride residues include 2,2′-hexafluoropropylidenediphthalic dianhydride, 4,4′-oxydiphthalic anhydride, 3,3 ′, 4. , 4′-benzophenonetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic anhydride, 1,4,5,8 Naphthalenetetracarboxylic dianhydride, 1,1-bis (2,3-dicarboxylphenyl) ethane dianhydride, 2,2-bis (2,3-dicarboxylphenyl) ethane dianhydride, 2,2 -Bis (3,3-carboxylphenyl) ethane dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 3,3 ', 4,4'-biphenyl Ether tetraca Boronic acid dianhydride, 2,3,3 ′, 4′-biphenyl ether tetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, pyromellitic dianhydride, 3, 4,9,10-perylenetetracarboxylic dianhydride, 2,3,3 ′, 4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, etc. Can be mentioned. Two or more of these may be used. Particularly preferred is 4,4'-oxydiphthalic anhydride.

  Although the diamine residue of (B) soluble polyimide in this invention is not specifically limited, The residue of the diamine represented by the following general formula (2) or (3) is preferable. You may have 2 or more types of these.

In said general formula (2), a shows the range of 3-10. In the general formula (3), Y represents —CH ₂ —, —C (CH ₃ ) ₂ —, —O—, —CO—, —SO ₂ —, —S—, —NHCO—, —C (CF ₃ ) _2- , -COO- or a single bond.

  The diamine (polyoxypropylene diamine) represented by the general formula (2) can improve developability with respect to a 1% by weight aqueous sodium carbonate solution. Moreover, the elasticity modulus after hardening of a photosensitive coverlay can be reduced more, and the curvature of a laminated body with a flexible printed circuit board can be reduced more. The diamine residue represented by the general formula (2) is preferably 5 mol% or more of all diamine residues, more preferably 20 mol% or more, and more preferably 30 mol% or more. Further, from the viewpoint of the accuracy of the development pattern, 60 mol% or less is preferable.

  Since the diamine represented by the general formula (3) has a carboxyl group, the developability with a 1 wt% aqueous sodium carbonate solution can be further improved. Moreover, since it has a reactive cross-linking point with the epoxy compound of component (A), it is possible to improve the folding resistance after curing. The diamine residue represented by the general formula (3) is preferably 10 mol% or more, more preferably 20 mol% or more of all diamine residues. On the other hand, 60 mol% or less is preferable from the viewpoint of reducing film loss during development.

  Examples of the diamine represented by the general formula (3) include 3,3′-diamino-4,4′-dicarboxybiphenyl, 4,4′-diamino-3,3′-dicarboxybiphenyl, and 4,4 ′. -Diamino-2,2'-dicarboxybiphenyl, 3,3'-diamino-4,4'-dicarboxydiphenylmethane, 3,3'-diamino-5,5'-dicarboxydiphenylmethane, 4,4'-diamino -2,2'-dicarboxydiphenylmethane, 4,4'-diamino-3,3'-dicarboxydiphenylmethane, 2,2-bis [3-amino-4-carboxyphenyl] propane, 2,2-bis [4 -Amino-3-carboxyphenyl] propane, 2,2-bis [3-amino-4-carboxyphenyl] hexafluoropropane, 3,3′-diamino-4,4 -Dicarboxydiphenyl ether, 4,4'-diamino-3,3'-dicarboxydiphenyl ether, 4,4'-diamino-2,2'-dicarboxydiphenyl ether, 3,3'-diamino-4,4'-di Examples thereof include carboxydiphenyl sulfone, 4,4′-diamino-3,3′-dicarboxydiphenyl sulfone, 4,4′-diamino-2,2′-dicarboxydiphenyl sulfone and the like.

  (B) The soluble polyimide may have a residue of diamine (siloxane diamine) represented by the following general formula (4) in addition to the above diamine residue or instead of the above diamine residue. Good. By having such a diamine residue, the elastic modulus after curing of the photosensitive coverlay can be further reduced, and the warpage of the laminate with the flexible printed board can be further reduced. The diamine residue represented by the general formula (4) is preferably 5 mol% or more, more preferably 10 mol% or more of all diamine residues. On the other hand, 30 mol% or less is preferable from the viewpoint of improving developability with a 1 wt% aqueous sodium carbonate solution.

In the general formula ^(4), R 1 ~R 4 represents an alkyl group or an aryl group having 1 to 3 carbon atoms. i and j represent an integer of 1 to 6, and k represents an integer of 1 to 10. When k is 2 or more, the plurality of R ^{1 to} R ⁴ may be the same or different.

  As the diamine component constituting the diamine residue of the soluble polyimide (B) in the present invention, the diamine represented by the general formula (2) / the diamine represented by the general formula (3) / the general formula (4) The diamine combination represented is more preferred.

  (B) The soluble polyimide may have diamine residues other than the above general formulas (2) to (4). Examples of other diamines include 3,3′-diaminodiphenyl ether, 4,4′-diamino-3,3 ′, 5,5′-tetramethyldiphenylmethane, 4,4′-diamino-3,3′-diethyl. -5,5'-dimethyldiphenylmethane, 4,4'-diaminodiphenyl-2,2'-propane, 4,4'-diaminodiphenylmethane, 3,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diethyl-4,4′-diaminodiphenyl ether, 3,3′-diethoxy-4,4′-diaminodiphenylmethane, 3,3 ′ -Dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4, -diaminodiphenylpropane, 3,3′-diethyl-4,4′-diaminodiphenylpropane, 3,3′-dimethyl-5,5′-diethyl-4,4′-diaminodiphenylmethane, 3,3′-dimethoxy-4,4′-diamino Diphenyl ether, 3,3′-dimethoxy-4,4′-diaminodiphenylmethane, 3,3′-dimethoxy-4,4′-diaminodiphenyl sulfone, 3,3′-dimethoxy-4,4′-diaminodiphenylpropane, 3 , 3′-diethoxy-4,4′-diaminodiphenylpropane, 3,3 ′, 5,5′-tetramethyl-4,4′-diaminodiphenylmethane, 3,3 ′, 5,5′-tetraethyl-4, 4′-diaminodiphenylmethane, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biff Nyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis [3- ( Aminophenoxy) phenoxy] benzene, bis [4- (4-aminophenoxy) phenyl] ether, 2,2′-bis [4- (4-aminophenoxy) phenyl] propane, polypropylene glycol diamine, polyethylene glycol diamine, and the like. It is done. Among these, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis [3- (aminophenoxy) phenoxy] benzene, 4,4 ′ -Bis (3-aminophenoxy) biphenyl and the like are preferable. Two or more of these may be used.

  The soluble polyimide (B) in the present invention may be end-capped with a terminal capping agent. Examples of end-capping agents include aniline, o-toluidine, m-toluidine, p-toluidine, 2,3-xylidine, 2,6-xylidine, 3,4-xylidine, 3,5-xylidine, o-chloroaniline. , M-chloroaniline, p-chloroaniline, o-bromoaniline, m-bromoaniline, p-bromoaniline, o-nitroaniline, p-nitroaniline, m-nitroaniline, o-aminophenol, m-aminophenol P-aminophenol, o-anisidine, m-anisidine, p-anisidine, o-phenetidine, m-phenetidine, p-phenetidine, o-aminobenzaldehyde, p-aminobenzaldehyde, m-aminobenzaldehyde, o-aminobenzonitrile , P-aminobenzonitrile, m-aminobenzuni Ril, 2-aminobiphenyl, 3-aminobiphenyl, 4-aminobiphenyl, 2-aminophenylphenyl ether, 3-aminophenylphenyl ether, 4-aminophenylphenyl ether, 2-aminobenzophenone, 3-aminobenzophenone, 4- Aminobenzophenone, 2-aminophenyl phenyl sulfide, 3-aminophenyl phenyl sulfide, 4-aminophenyl phenyl sulfide, 2-aminophenyl phenyl sulfone, 3-aminophenyl phenyl sulfone, 4-aminophenyl phenyl sulfone, α-naphthylamine, β -Naphthylamine, 1-amino-2-naphthol, 5-amino-1-naphthol, 2-amino-1-naphthol, 4-amino-1-naphthol, 5-amino-2-naphthol, 7-a Roh-2-naphthol, 8-amino-1-naphthol, 8-amino-2-naphthol, 1-aminoanthracene, 2-aminoanthracene, and aromatic monoamines such as 9-amino-anthracene. Among these, m-aminophenol is preferable. Two or more of these may be used.

  The soluble polyimide (B) in the present invention preferably has a weight average molecular weight of 10,000 or more and 30,000 or less. By setting the weight average molecular weight to 10,000 or more, the folding resistance after curing can be improved. On the other hand, when the weight average molecular weight is 30,000 or less, the developability with a 1 wt% aqueous sodium carbonate solution can be improved. 20,000 or less is more preferable, and 15,000 or less is more preferable. Moreover, when 2 or more types of soluble polyimides are contained, at least 1 type of weight average molecular weight should just be the said range.

(B) The weight average molecular weight of the soluble polyimide can be determined by the following method. Using a polyimide solution having a solid concentration of 0.1% by weight in which soluble polyimide is dissolved in N-methylpyrrolidone (NMP), the weight average molecular weight in terms of polystyrene is calculated by GPC apparatus Waters 2690 (manufactured by Waters Co., Ltd.). GPC measurement conditions are such that the moving bed is NMP in which LiCl and phosphoric acid are dissolved at a concentration of 0.05 mol / L, and the development rate is 0.4 ml / min. As a GPC device to be used, for example,
Detector: Waters 996
System controller: Waters 2690
Column oven: Waters HTR-B
Thermo Controller: Waters TCM
Column: TOSOH grand comn
Column: THSOH TSK-GEL α-4000
Column: TOSOH TSK-GEL α-2500 and the like.

  (B) A soluble polyimide can be obtained by reacting an acid anhydride, a diamine, and optionally a terminal blocking agent, preferably in a solvent, to obtain a polyimide precursor, and ring-closing with heat or a suitable catalyst. it can. You may use the obtained reaction liquid as a polyimide varnish for preparation of a photosensitive coverlay as it is. Solvents used for polymerization of polyimide include N-methyl-2-pyrrolidone, N, N-diethylacetamide, N, N-diethylformamide, dimethylsulfoxide, tetramethylurea, hexanemethylphosphoric triamide, γ-butyrolactone, etc. Polar solvents, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate, diethyl oxalate, dimethyl carbonate, diethyl malonate, diethyl ether, isopropyl ether, ethylene glycol Examples include ethers such as dimethyl ether, diethylene glycol dimethyl ether, and tetrahydrofuran, and hydrocarbons such as hexane, heptane, octane, benzene, toluene, and xylene. Among these, N-methyl-2-pyrrolidone is preferable. Two or more of these may be used.

  In addition, the (B) soluble polyimide in this invention points out an imidation rate 90% or more. 99% or more is preferable, and 100% is more preferable.

  The photosensitive coverlay of the present invention contains (C) a photopolymerizable compound and (D) a photopolymerization initiator. (C) The photopolymerizable compound is preferably a compound having at least one unsaturated double bond in the molecule. For example, the compound which has a vinyl group and a (meth) acryloyl group is mentioned. Here, the (meth) acryloyl group is a generic name for an acryloyl group and a methacryloyl group.

  (C) As a photopolymerizable compound, for example, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (Meth) acrylate, 1,2-propylene glycol di (meth) acrylate, di (1,2-propylene glycol) di (meth) acrylate, tri (1,2-propylene glycol) di (meth) acrylate, tetra (1 , 2-propylene glycol) di (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate , Urethane (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol tri (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 1, 3- (meth) acryloyloxy-2-hydroxypropane, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tetramethylolpropane tetra (meth) acrylate, 2- Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, N-vinylpyrrolidone, 2-hydroxyethyl (meth) acryloyl phosphate, (meth) acrylamide, N-methylo Le (meth) acrylamide, N- methoxymethyl acrylamide, N- ethoxymethyl acrylamide, ethylene glycol monoacrylate, dipropylene glycol monoacrylate, N, etc. N- dimethylaminoethyl acrylate. Moreover, an epoxy-modified (meth) acrylic resin, a urethane-modified (meth) acrylic resin, a polyester-modified (meth) acrylic resin, and the like are also included. Two or more of these may be contained.

  Among these, polyethylene glycol diacrylate and urethane acrylate are preferable. Polyethylene glycol diacrylate can further improve developability with an aqueous sodium carbonate solution. Urethane acrylate can further reduce stress and elastic modulus after curing.

  Examples of the polyethylene glycol diacrylate include “Aronix (registered trademark)” M-245, M315, and M450 (above, trade name, manufactured by Toagosei Co., Ltd.). Examples of the urethane acrylate include CN981 and CN982E75. CN982P90, CN966J75, CN9001 (trade name, manufactured by Sakai Kogyo Co., Ltd.), and the like.

  (D) Examples of the photopolymerization initiator include Michler's ketone, 4,4′-bis (diethylamino) benzophenone, 4,4 ′, 4 ″ -tris (dimethylamino) triphenylmethane, 2,2′-bis (2 -Chlorophenyl) -4,4 ', 5,5'-tetraphenyl-1,2'-diimidazole, acetophenone, benzoin, 2-methylbenzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-t-butylanthraquinone, 1,2-benzo-9,10-anthraquinone, methylanthraquinone, thioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, diacetylbenzyl, Dildimethyl ketal, benzyl diethyl ketal, 2 (2′-furylethylidene) -4,6-bis (trichloromethyl) -S-triazine, 2 [2 ′ (5 ″ -methylfuryl) ethylidene] -4,6-bis (Trichloromethyl) -S-triazine, 2 (p-methoxyphenyl) -4,6-bis (trichloromethyl) -S-triazine, 2,6-di (p-azidobenzal) -4-methylcyclohexanone, 4,4 '-Diazidochalcone, di (tetraalkylammonium) -4,4'-diazidostilbene-2,2'-disulfonate, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy- Cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2 Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2- Benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2, 4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propane-1-ketone, bis (n5-2, 4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -fur Enyl) titanium, 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], iodonium, (4-methylphenyl) [4- (2-methylpropyl) phenyl] -Hexafluorophosphate (1-), ethyl-4-dimethylaminobenzoate, 2-ethylhexyl-4-dimethylaminobenzoate, ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole- 3-yl]-, 1- (O-acetyloxime) and the like. Two or more of these may be contained. Among these, OXE-02 (manufactured by Ciba Japan), “Optomer (registered trademark)” N1919, and NCI-831 (manufactured by Adeka Corporation) are preferable.

  In the photosensitive cover lay of the present invention, the content of the epoxy compound represented by (A) the general formula (1) is preferably 10 to 30 parts by weight with respect to 100 parts by weight of the (B) soluble polyimide. Further, the content of (C) the photopolymerizable compound is preferably 50 to 70 parts by weight with respect to 100 parts by weight of (B) the soluble polyimide, and the content of (D) the photopolymerization initiator is (B) the soluble polyimide. 1-10 weight part is preferable with respect to 100 weight part. By setting the contents of (C) the photopolymerizable compound and (D) the photopolymerization initiator within the above ranges, the photocuring reaction can be appropriately advanced efficiently.

  The photosensitive coverlay of this invention may contain various additives, such as a flame retardant, an antifoamer, a filler, a leveling agent, a polymerization inhibitor, as needed.

  Examples of the filler include inorganic fillers such as silica, talc, barium sulfate, wollastonite, and calcium carbonate, and organic polymer fillers. Specifically, SOE2, SOE3 (above, trade names, manufactured by Admatechs Co., Ltd.), HE5 (trade names, manufactured by Takehara Chemical Industry Co., Ltd.), SG95, D-1000, D-800, D-600 ( As mentioned above, trade names, manufactured by Nippon Talc Co., Ltd., B-30, B-35, BF21, BF40 (above, trade names, manufactured by Sakai Chemical Industry Co., Ltd.) and the like can be mentioned. As for content of a filler, 20-40 weight part is preferable with respect to 100 weight part of (B) soluble polyimide.

  The photosensitive coverlay of the present invention preferably contains a solvent. Examples of the solvent include N-methylpyrrolidone (NMP), γ-butyrolactone (γ-BL), N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide and the like.

The photosensitive coverlay of the present invention is preferably developable with a 1% by weight aqueous sodium carbonate solution. Here, development with a 1% by weight aqueous sodium carbonate solution means that a photosensitive coverlay applied to a copper foil so as to have a film thickness of 20 μm is provided with a negative photomask and an i-line integrated exposure. When exposed to 100 mJ / cm ² in quantity measurement, developed with a 1 wt% sodium carbonate aqueous solution at a liquid temperature of 30 to 35 ° C. under a discharge pressure of 0.05 to 0.1 MPa, 1 wt% carbonic acid in the unexposed area The dissolution time in an aqueous sodium solution is 4 minutes or less, and there is no dissolution residue at the bottom of the φ50 μm via when observed with an optical microscope at 200 times magnification, and the unexposed area is completely dissolved. It means that the remaining film rate is 80% or more.

  The photosensitive coverlay of this invention can be obtained by mixing said (A)-(D) and another component as needed. Examples of the mixing method include a method of kneading with a general kneading device such as a three roll or bead mill device, and a method of stirring with a general stirring device.

  Next, a method for forming a cured film using the photosensitive cover lay of the present invention will be described.

  First, the photosensitive cover lay is applied to the substrate surface by screen printing, curtain roll, reverse roll, spray coating, spin coating using a spinner or the like, and dried. The thickness of the coating film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. As a drying method of a coating film, it is preferable to heat at the temperature of 120 degrees C or less, and it is more preferable to heat at the temperature of 50-100 degreeC. In addition, in order to dry quickly, it is preferable to blow hot air.

Next, exposure and alkali development are performed to form a pattern. For example, a negative photomask is placed on the dry coating film and irradiated with actinic rays such as ultraviolet rays, visible rays, electron beams, and laser beams. Exposure is preferably 50~1000mJ / cm ^2, more preferably 50~400mJ / cm ^2. The exposure may be performed under nitrogen and is preferably performed under reduced pressure. In addition, in order to harden a light irradiation part more, you may heat-process after exposure. Alkali development is to remove an uncured portion by bringing an alkaline solution into contact with the coating film after exposure by a method such as shower, paddle, immersion, or ultrasonic wave. It is preferable to remove unnecessary residues by rinsing the pattern formed by alkali development. Examples of the rinsing liquid include water and acidic aqueous solutions.

  As an alkaline solution, 0.01 to 3 weight% sodium carbonate aqueous solution is preferable, and 0.5 to 1 weight% sodium carbonate aqueous solution is more preferable. The photosensitive coverlay of the present invention has high alkali solubility, and a 50 μmφ via pattern can be easily formed with a 1 wt% aqueous sodium carbonate solution. The temperature of the alkaline solution is preferably 10 to 40 ° C, and more preferably 20 to 35 ° C. Further, the spray pressure of the etching solution is preferably 0.05 to 3.0 MPs, particularly preferably 0.1 to 2 MPs.

  Next, the formed pattern is cured by heat treatment. The temperature of the heat treatment is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint of more efficiently proceeding curing. On the other hand, when used as a protective film of a flexible printed circuit board, from the viewpoint of suppressing oxidative deterioration of the wiring, 250 ° C. or lower is preferable, and 200 ° C. or lower is more preferable. Further, the heat treatment may be performed in an inert gas atmosphere such as argon, nitrogen, helium, or the like, and oxidation deterioration due to oxygen can be suppressed.

  The cured film obtained from the photosensitive coverlay of this invention can be preferably used as a protective film of a flexible printed circuit board. As an example, a method of forming a protective film for flexible printed circuit board wiring using the photosensitive coverlay of the present invention will be described. First, a photosensitive coverlay is applied on a substrate and dried. Usually, a polyimide film on which a metal wiring pattern such as copper is formed is used as a base material of a flexible printed board. The coating method is preferably a screen printing method. The film thickness after drying of the photosensitive cover lay is generally not less than the thickness of the wiring pattern of the flexible printed board and not more than twice the wiring pattern. The thickness of the wiring pattern is usually 9 to 18 μm, and the thickness of the wiring protective film is preferably 10 to 20 μm.

  Next, it exposes through the mask of a predetermined pattern. An ultrahigh pressure mercury lamp is preferably used for exposure. Further, development and curing are performed to obtain a wiring protective film.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In addition, the detail of the raw material shown by the abbreviation in each Example is shown below.
<Polyimide synthetic raw material>
PMDA: pyromellitic anhydride (manufactured by Daicel Chemical Industries)
OPDA: 4,4′-oxydiphthalic dianhydride (manac)
SiDA: Bis (3-aminopropyl) tetramethyldisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.)
MBAA: [Bis (4-amino-3-carboxy) phenyl] methane (manufactured by Wakayama Seika Kogyo Co., Ltd.)
D-400: polyoxypropylene diamine (manufactured by BASF, trade name “D-400” a = 5.6 in the general formula (2))
3Ap: 3-aminophenol (manufactured by Tokyo Chemical Industry Co., Ltd.)
<Photopolymerizable compound>
CN981: Urethane acrylate oligomer (manufactured by Sartomer Japan, Inc.)
M-245: Polyethylene glycol diacrylate (trade name “Aronix (registered trademark)” M-245, manufactured by Toagosei Co., Ltd.)
<Photopolymerization initiator>
N1919: Photoradical polymerization initiator (trade name “Optomer (registered trademark)” N1919, manufactured by Adeka Co., Ltd.)
NCI-831; photoradical polymerization initiator (manufactured by Adeka Co., Ltd., trade name "Adeka Arcles (registered trademark)" NCI-831)
<Epoxy compound>
850-S: Bis (bisphenol) type A epoxy resin (manufactured by DIC Corporation, trade name “EPICLON (registered trademark) 850-S)
EP-4000S: Propylene oxide modified BisA type epoxy resin (manufactured by Adeka Co., Ltd., trade name “Adeka Resin (registered trademark)” EP-4000S, n + m = 2 in the following general formula (5))
EP-4003S: Propylene oxide modified BisA type epoxy resin (manufactured by Adeka Co., Ltd., trade name “Adeka Resin (registered trademark)” EP-4003S, n + m = 5-6 in the following general formula (5))

PG207GS: Propylene oxide modified epoxy resin (manufactured by Toto Kasei Co., Ltd.), l = 4 to 6 in the following general formula (6)

BEO-60E: Ethylene oxide modified BisA type epoxy resin (manufactured by Shin Nippon Rika Co., Ltd., trade name Rikaresin BEO-60E))
<Thermal polymerization inhibitor>
HQME: Hydroquinone monomethyl ether <Inorganic filler>
SG-95: Talc fine particles Average particle size 2.5 μm (Nippon Talc Co., Ltd.)
<Surfactant>
L1983: "Disparon (registered trademark)" L1983 (manufactured by Enomoto Kasei Co., Ltd.)
<Colorant>
PB4920: Blue pigment <solvent>
NMP: N-methylpyrrolidone γ-BL: γ-butyrolactone.

  The evaluation method in each example and comparative example is shown below.

(1) Measurement of weight average molecular weight Using a solution having a solid content concentration of 0.1% by weight obtained by dissolving polyimide in NMP, a weight average molecular weight in terms of polystyrene is calculated by a GPC apparatus Waters 2690 (manufactured by Waters Co., Ltd.) having the configuration shown below. did. GPC measurement conditions were such that the moving bed was NMP in which LiCl and phosphoric acid were each dissolved at a concentration of 0.05 mol / L, and the development rate was 0.4 ml / min.
Detector: Waters 996
System controller: Waters 2690
Column oven: Waters HTR-B
Thermo Controller: Waters TCM
Column: TOSOH grand comn
Column: THSOH TSK-GEL α-4000
Column: TOSOH TSK-GEL α-2500.

(2) Imidization rate measurement A solution having a solid concentration of 40 to 25% by weight obtained by dissolving polyimide in γ-BL was prepared and applied to a silicon wafer with a spinner so as to have a film thickness of 3 to 5 μm. Heat treated for minutes. Half of this was heat-treated at 280 ° C. for 5 minutes using a hot plate to completely close the imide group. About each of what heat-processed at 120 degreeC and 280 degreeC, the FT-IR (FT-720 made from HORIBA) analysis was performed, and the imidation ratio was computed by the difference of the peak of 1366cm < ^-1 > in which absorption derived from an imide group appears.

(3) Solubility evaluation 1 g of polyimide was added to 100 g of NMP at 25 ° C. and stirred, and the dissolved one was judged to be soluble.

(4) Preparation of cured film Screen printing machine MEC-2400 (manufactured by Mitani Electronics Co., Ltd.), SUS 200 mesh, emulsion thickness 20 μm, 50 mm × 50 mm screen plate, 15 μm thick copper foil (NA- A photosensitive cover lay was applied on the VLP (made by Mitsui Kinzoku) so that the film thickness after drying was 20 μm. Subsequently, heat treatment was performed at 100 ° C. for 30 minutes using a hot air oven INH-21CD (manufactured by Koyo Thermo System Co., Ltd.). Then, a negative photomask in which vias of 50 to 100 μm were arranged at a pitch of 100 μm with an area of 50 × 50 mm was exposed, and 100 mJ / cm ² exposure was performed with an integrated exposure dose measurement value of i-line. Then, using a developing device AD-1200 (manufactured by Mikasa), development is performed with a 1 wt% sodium carbonate aqueous solution at a liquid temperature of 30 ° C. as a developing solution at a discharge pressure of 0.1 MPa for 4 minutes every minute for 30 seconds with water. It was. Subsequently, using a hot air oven INH-21CD (manufactured by Koyo Thermo System Co., Ltd.), heat treatment was performed at 180 ° C. for 60 minutes to completely cure the photosensitive coverlay to obtain a cured film.

(5) Preparation of single film film Using a bar coater of # 24 to 28, a 12 μm thick copper foil (NA-DFF: made by Mitsui Kinzoku) was coated so that the film thickness after drying was 20 μm. Then, heat treatment was performed at 100 ° C. for 30 minutes using a hot air oven INH-21CD (manufactured by Koyo Thermo System Co., Ltd.). Then, 100 mJ / cm < ² > whole surface exposure was carried out by the integrated exposure amount measured value of i line | wire. Subsequently, using a hot air oven INH-21CD (manufactured by Koyo Thermo System Co., Ltd.), heat treatment was performed at 180 ° C. for 60 minutes to completely cure the photosensitive coverlay to obtain a cured film. The cured film with copper was immersed in a copper etching solution (ferric chloride aqueous solution), and the copper foil was completely dissolved and washed with water to obtain a single film film of a photosensitive coverlay.

(6) Evaluation of developability The surface of each cured film having a development time of 1 minute to 4 minutes obtained by the method described in (4) above was observed 200 times with an optical microscope, and evaluated according to the following criteria.
○: A via having a photosensitive pattern of 50 μmφ is surely vacant and there is no dissolved residue at the bottom of the via.
Δ: A via having a photosensitive pattern of 50 μmφ is vacant, but a dissolved residue is slightly seen at the bottom of the via.
X: 50 μmφ photosensitive pattern with no vias at all.
-: A photosensitive pattern of 50 μmφ is distorted and peeled off.

Moreover, the residual film rate of the cured film obtained by the method of said (4) description was measured. The film thickness of the unexposed part and the exposed part was measured by AMBiOS XP-1 (manufactured by Tech Science Co., Ltd.), and the remaining film ratio represented by the following formula was calculated. In addition, what was evaluated as (circle) in the surface observation of the said cured film was used for the measurement of the remaining film rate. When there were a plurality of samples evaluated as “good”, the film thicknesses of all of them were measured, and the number average value was calculated.
Residual film ratio = ((unexposed part film thickness−exposed part film thickness) / unexposed part film thickness) × 100%
When the evaluation result on the surface of the cured film becomes ◯ within a development time of 4 minutes and the remaining film ratio is 80% or more, it is determined that development is possible.

(7) Folding resistance evaluation A polyimide film “Kapton (registered trademark)” 100EN (manufactured by Toray DuPont Co., Ltd.) having a thickness of 25 μm is cut into a size of 50 mm × 50 mm, and the photosensitive resin composition is dried on this. The film was applied to a thickness of 20 μm and dried at 100 ° C. for 30 minutes. Subsequently, 100 mJ / cm < ² > exposure was carried out with the ultrahigh pressure mercury lamp, and it heat-processed for 60 minutes at 180 degreeC using hot air oven, and obtained the laminated body of the cured film and the polyimide film. The obtained laminate was cut into a strip having a width of 10 mm and a length of 50 mm, bent 10 times at 180 ° at a length of 25 mm, and visually observed for cracks. When cracks did not occur even after bending 10 times, it was evaluated as ◯, and when cracks were observed, the number of bendings at that time was regarded as folding resistance.

(8) Warpage evaluation In order to modelly evaluate the warpage of the laminate of the cured cover layer and the flexible printed board, the warpage of the laminate of the cured cover layer and the polyimide film was evaluated. The laminate of the cured film and the polyimide film obtained by the method described in (7) above was placed on a flat place so that the top was convex, and the height of the convex portion was measured. When the height of the convex portion is 10 mm or less, it can be evaluated that the warpage is small.

(9) Solder heat resistance evaluation After the cured film obtained by the method described in (4) above is allowed to stand for 24 hours in an atmosphere at a temperature of 23 ° C. and a humidity of 50% RH, the solder completely dissolved at 300 ° C. Immerse in the bath for 10 seconds. Thereafter, the sample pulled up was visually observed. The case where cracks, peeling and swelling occurred was evaluated as x, and the case where none occurred was evaluated as o.

(10) Measurement of film physical properties (strength measurement)
A single film of a photosensitive coverlay obtained by the method described in (5) above was cut into a 1 cm × 15 cm strip shape with a single blade, and a sample was prepared so that the number of test pieces was 5 or more.
Tensilon to be used: Orientec Tensilon RTA-100
Range (100kgN): 10-20%
Pulling speed (mm / min): 300 mm / min Measuring length (mm): 50 (mm)
Film physical property tests were performed under the above conditions, and the elongation (%), stress (MPa), and elastic modulus (MPa) of the photosensitive coverlay were measured.

Synthesis Example 1 Synthesis of Polyimide 12.1 g (31.2 mol) of MBAA, 29.4 g (50.0 mol) of D-400, 6.30 g of SiDA (18. 8mol), 85.1g of NMP was charged, stirred in an oil bath at 60 ° C, and 3.27g of 3Ap was added and dissolved as an end-capping agent. When the solution became uniform, 29.4 g (90.0 mol) of PMDA and 4.65 g (10.0 mol) of ODPA were added and reacted for 1 hour. Thereafter, the temperature of the oil bath was raised to 170 to 180 ° C., and the reaction was carried out for 2 hours while removing distilled water. Thereafter, it was allowed to cool to room temperature to obtain a polyimide solution A having a solid content of 50% by weight. The obtained polyimide was soluble, the weight average molecular weight was 14732, and the imidation ratio was 100%.

Synthesis Example 2 Synthesis of Polyimide Same as Synthesis Example 1 except that NMP was changed from 85.1 g to 88.7 g, PMDA was changed from 29.4 g to 0 g, and ODPA was changed from 4.65 g to 46.5 g (100 mol). A polyimide solution B having a solid content of 50% by weight was obtained. The obtained polyimide was soluble, the weight average molecular weight was 15225, and the imidation ratio was 100%.

Synthesis Example 3 Synthesis of polyimide NMP from 85.1 g to 73.5 g, MBAA from 12.1 g to 19.3 g (50 mol), D-400 from 29.4 g to 0 g, and SiDA from 6.30 g to 16. A polyimide solution C having a solid content of 50% by weight was obtained in the same manner as in Synthesis Example 1 except that the amount was changed to 7 g (50.0 mol). The obtained polyimide was soluble, the weight average molecular weight was 13521, and the imidization ratio was 100%.

Synthesis Example 4 Synthesis of polyimide NMP from 85.1 g to 85.0 g, MBAA from 12.1 g to 1.93 g (5.0 mol), and D-400 from 29.4 g to 32.3 g (55.0 mol). A polyimide solution D having a solid content of 50% by weight was obtained in the same manner as in Synthesis Example 1 except that SiDA was changed from 6.30 g to 13.4 g (40.0 mol). The obtained polyimide was soluble, the weight average molecular weight was 12423, and the imidization ratio was 100%.

Synthesis Example 5 Synthesis of polyimide NMP from 85.1 g to 73.6 g, MBAA from 12.1 g to 4.77 g (11.1 mol), and D-400 from 29.4 g to 7.24 g (11.1 mol). A polyimide solution E having a solid content of 50% by weight was obtained in the same manner as in Synthesis Example 1 except that SiDA was changed from 6.30 g to 29.0 g (77.8 mol). The obtained polyimide was soluble, the weight average molecular weight was 12041, and the imidation ratio was 100%.

Example 1
To the soluble polyimide solution A8 g obtained by the method described in Synthesis Example 1, 1.9 g of CN981, 0.6 g of M-245, 0.15 g of NCI-831, 0.8 g of EP4003S, and 0.83 of L1983. 08 g, 0.02 g of HQME, 1.4 g of SG-95, and 0.02 g of PB4920 were added, mixed and stirred, and passed through 3 rolls 5 times to obtain photosensitive coverlay A which was a viscous liquid.

Example 2
A photosensitive coverlay B, which is a viscous liquid, was obtained in the same manner as in Example 1 except that 0.8 g of PG207GS was added instead of 0.8 g of EP-4003S.

Example 3
A photosensitive coverlay C, which is a viscous liquid, was obtained in the same manner as in Example 1 except that the soluble polyimide solution B obtained by the method described in Synthesis Example 2 was used instead of the soluble polyimide solution A.

Example 4
A photosensitive coverlay D, which is a viscous liquid, was obtained in the same manner as in Example 1 except that the soluble polyimide solution C obtained by the method described in Synthesis Example 3 was used instead of the soluble polyimide solution A.

Example 5
A photosensitive coverlay E, which is a viscous liquid, was obtained in the same manner as in Example 1 except that the soluble polyimide solution D obtained by the method described in Synthesis Example 4 was used instead of the soluble polyimide solution A.

Comparative Example 1
A photosensitive coverlay F, which is a viscous liquid, was obtained in the same manner as in Example 1 except that 0.8 g of EP-4000S was used instead of 0.8 g of EP-4003.

Comparative Example 2
A photosensitive coverlay G, which is a viscous liquid, was obtained in the same manner as in Example 1 except that 0.8g of 850-S was used instead of 0.8g of EP-4003S.

Comparative Example 3
A photosensitive coverlay H, which is a viscous liquid, was obtained in the same manner as in Example 1 except that 0.8 g of BEO-60E was used instead of 0.8 g of EP-4003S.

Comparative Example 4
To soluble polyimide solution E8g obtained by the method described in Synthesis Example 5, CN981 1.9g, M-245 0.6g, NCI-831 0.15g, L1983 0.08g, HQME 0.02g, SG-95 (1.4 g) and PB4920 (0.02 g) were added, and after mixing and stirring, the mixture was passed through 3 rolls 5 times to obtain photosensitive coverlay I as a viscous liquid.

  Table 1 shows the composition of the photosensitive coverlay obtained in each Example and Comparative Example, and Table 2 shows the evaluation results.

Claims (6)

A photosensitive cover lay comprising at least (A) an epoxy compound represented by the following general formula (1), (B) a soluble polyimide, (C) a photopolymerizable compound, and (D) a photopolymerization initiator. .

(In the general formula (1), X represents a divalent linking group. N and m each represent a range of 1 to 10, provided that n + m ≧ 4.) The soluble polyimide (B) has an acid dianhydride residue and a diamine residue, and has pyromellitic dianhydride residue of 10 mol% or more in the total acid dianhydride residue. The photosensitive coverlay as described. The (B) soluble polyimide has an acid dianhydride residue and a diamine residue, and has a diamine residue represented by the following general formula (2) in an amount of 5 mol% to 60 mol% in all diamine residues. The photosensitive cover lay according to claim 1 or 2.

(In the general formula (2), a represents a range of 3 to 10.) The (B) soluble polyimide has an acid dianhydride residue and a diamine residue, and has a diamine residue represented by the following general formula (3) in a range of 10 mol% to 60 mol% in all diamine residues. The photosensitive coverlay according to any one of claims 1 to 3.

(In the general formula (3), Y represents —CH ₂ —, —C (CH ₃ ) ₂ —, —O—, —CO—, —SO ₂ —, —S—, —NHCO—, —C (CF ₃ ) _2- , -COO- or a single bond is shown.) The photosensitive coverlay according to any one of claims 1 to 4, which can be developed with a 1 wt% aqueous sodium carbonate solution. The laminated body which has a protective film formed by hardening | curing the photosensitive coverlay in any one of Claims 1-5 on a flexible printed circuit board.