JP2001119129A - Coverlay film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cover lay film which is excellent in adhesiveness and solder heat resistance, excellent in film laminating workability, so that productivity during production is good, and furthermore excellent in insulation and bending resistance. I do. SOLUTION: This is a coverlay film in which an adhesive layer is laminated on one surface of an insulating plastic film or a peelable film, wherein the adhesive layer is (a) an epoxy resin, and (b)
A coverlay film for printed circuit boards, comprising a curing agent and (c) a polyimide resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coverlay film which is used for protecting a printed circuit board, in particular, a printed circuit of a flexible printed circuit board, and which is excellent in adhesiveness, heat resistance, electric insulation and bonding workability.

[0002]

2. Description of the Related Art With the rapid spread of various electronic devices in recent years, flexible printed circuit boards used for these devices are required to have high reliability and performance. One that greatly affects the reliability and performance of the flexible substrate is a coverlay film laminated on the substrate. The coverlay film covers the surface of a circuit produced by etching a copper foil in order to secure electrical insulation of the circuit portion, prevent rust, protect the surface, and maintain flexibility. Therefore, the adhesive layer, which is a main component of the coverlay film, is required to have improved adhesiveness, heat resistance, and bending resistance. In addition, it is necessary to cope with a printed circuit which has been increased in density with an increase in the amount of information, and the electrical insulation between the miniaturized printed circuits after laminating a coverlay film is also an important required characteristic. Furthermore, with the recent increase in the importance of flexible printed circuit boards, there has been an increasing demand for improving productivity, and there has been a demand for improved workability in a process of bonding a printed circuit and a coverlay film. Specifically, it has become necessary to eliminate the problem that the adhesive exudes from the end face of the laminated body after bonding.

Conventionally, a coverlay film has been coated on one side of an insulating plastic film such as polyimide with an adhesive obtained by mixing a thermosetting resin such as an epoxy resin or a phenolic resin and an elastic component, and is applied to a semi-cured state (B). stage)
After heating and curing, a protective film with releasability is laminated. As the elastic component, an acrylonitrile-butadiene copolymer (hereinafter, referred to as NBR), a polyester resin, an acrylic resin, and modified products of these resins have been applied. Among them, a mixed adhesive of an epoxy resin and NBR has been suitably used from the viewpoint of adhesiveness and bending resistance. However, the coverlay film according to the prior art has a problem that it is difficult to bring the thermosetting resin into an appropriate semi-cured state. That is,
If a low-reactivity thermosetting adhesive is used to easily control the conditions of the semi-cured state in order to obtain an appropriate semi-cured state, not only the adhesive strength is insufficient, but also it is not possible to sufficiently cure under appropriate heat treatment conditions. However, there is a problem that the heat resistance is lowered, and that if the composition is sufficiently cured under heat treatment conditions, the production efficiency is lowered. On the other hand, if a highly reactive thermosetting adhesive is used,
The heat treatment conditions for the semi-cured state are narrowed, and not only the productivity is lowered due to the deterioration of the manufacturing conditions, but also the bending durability is liable to deteriorate, and the workability is deteriorated due to curling of the film. There was a problem to do.

Further, Japanese Patent Application Laid-Open No. 7-273434 discloses the use of an NBR containing a carboxyl group, an epoxy resin, a curing agent containing an aromatic polyamine having a specific reactivity index, and an adhesive containing a curing accelerator. A technique for solving the problem is disclosed in Japanese Patent Application Laid-Open No. 8-181418, which discloses the above-mentioned problem and the use of an adhesive containing a carboxyl group-containing NBR, an epoxy resin, a curing agent and a reactive copolymer. A technique has been disclosed in which the degree of hydrogenation is increased to 90% or more to improve the reliability under wet heat. However, even with the adhesive having the above-described configuration, the adhesive force is reduced when the bonding workability with the flexible printed circuit is improved, and the adhesive is protruded at the time of bonding with the circuit when the adhesive force is sufficiently increased. Had problems that occurred. Further, with the adhesive having the above-described structure, it has been difficult to satisfy the demand for high insulation properties corresponding to higher density, that is, finer circuit patterns.

[0005]

SUMMARY OF THE INVENTION As a result of intensive studies on the adhesive components to solve the above-mentioned problems, the present inventors have found that sufficient adhesive strength, high heat resistance, high bending durability, high electrical insulation, and high adhesion are obtained. The present inventors have found that a coverlay film excellent in laminating workability with no protruding agent can be obtained, and the present invention has been accomplished.

[0006]

The present invention is a coverlay film in which an adhesive layer is laminated on one surface of an insulating plastic film or a peelable film, wherein the adhesive layer comprises (a) an epoxy resin, (b) A) a curing agent and (c) a polyimide resin.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The coverlay film of the present invention has a structure in which an adhesive layer is laminated on an insulating plastic film or a peelable film, and the adhesive layer has a peelable protective film for protecting the layer as necessary. It is laminated. As the insulating plastic film constituting the present invention, any known plastic film having an insulating property can be used. Specifically, polyimides, polyesters such as polyethylene terephthalate, polyethylene, polyolefins such as polypropylene, polyphenylene sulfide, polyether sulfone, polyether ether ketone, aramid,
Polycarbonate, polyarylate and the like are preferable because they have insulating properties. More preferred are polyimide, polyester and polyolefin. The film preferably has a thickness of 10 to 200 μm, more preferably 15 to 2 μm.
00 μm. Film thickness less than 10 μm or 20
If the thickness exceeds 0 μm, a problem is likely to occur in handling. The film can be subjected to surface treatment such as hydrolysis, corona discharge, low-temperature plasma, physical surface roughening, and easy adhesion coating if necessary. The adhesive strength with the layer can be improved.

Further, as the peelable film constituting the present invention, a film having the same composition as the above-mentioned insulating plastic film and having peelability can be used. More preferred are polyimides, polyesters and polyolefins. In particular, a film subjected to a release treatment with silicone or the like is suitably used. The preferred thickness of the peelable film is the same as that of the insulating plastic film. The protective film preferably has the same composition, thickness and release treatment as the release film. The protective film is peeled off when using the coverlay film.

Next, the adhesive layer constituting the present invention will be described in detail. (A) Epoxy resin Epoxy resin is a resin having two or more epoxy groups in a molecule, for example, glycidyl ether, glycidyl ester, glycidylamine, linear aliphatic epoxide,
A resin having any structure such as an alicyclic epoxide may be used, and two or more resins may be used alone. In particular,
Bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, resol phenol diglycidyl ether, brominated bisphenol A diglycidyl ether, fluorinated bisphenol A diglycidyl ether, phenol novolak glycidyl ether, cresol novolac glycidyl ether, Glycidyl ethers such as brominated novolak glycidyl ether, glycidyl esters such as hexahydrophthalic acid diglycidyl ester, diglycidyl phthalate and dimer acid diglycidyl ester, triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane, tetraglycidyl methaxylene Glycidylamines such as diamine, epoxidized polybutadi And alicyclic epoxies such as 3,4-epoxy-6-methylcyclohexylmethyl carboxylate and 3,4-epoxycyclohexylmethyl carboxylate. . Of these, bisphenol-type epoxy resins are particularly preferred because they are inexpensive, and bisphenol A-type is particularly preferably used. The epoxy equivalent of the epoxy resin is preferably 4000 or less, more preferably 100 to 2000. If the epoxy equivalent is greater than 4000, the crosslink density of the cured product will be low, and the insulation will be reduced.

The epoxy resin suitably used in the present invention is specifically manufactured by Yuka Shell Epoxy Co., Ltd .: trade name; Epicoat 806, 828, 1001, manufactured by Asahi Denka Kogyo Co., Ltd .: trade name: EP-4100G, EP4400, EP -490
1. Nippon Kayaku Co., Ltd .: Trade name; EOCN102S, 103
S, 104S, 1020, EPPN501H, and the like. Use of a halogenated epoxy, particularly a brominated epoxy, is an effective means for imparting flame retardancy. Specific examples of brominated epoxies are available from Yuka Shell Epoxy Co., Ltd .: trade name; Epicoat 5045, 504
6, 5050, Nippon Kayaku: Brand name: BREN-S, B
REN-105, BREN-301 and the like.

(B) Curing agent A curing agent refers to a chemical substance which reacts with an epoxy resin to form a three-dimensional network structure. An aromatic polyamine, an aliphatic polyamine, a polyamide, an acid anhydride, a phenol derivative, a polymercaptan, Triamines, Lewis acid complexes and the like are used. Specifically, 4,4'-aminodiphenylmethane,
4,4′-diaminodiphenyl ether, diaminodiphenylsulfone, diaminodiphenylsulfide, m
-Phenylenediamine, 2,4-toluylenediamine,
m- or o-toluylenediamine, metaxylenediamine, metaaminobenzylamine, benzidine, 2,6-
Aromatic polyamines such as diaminopyridine, isophthalic dihydrazide, diethylenetriamine, dipropylenetriamine, diethylenetetramine, triethylenetetramine, dimethylaminopropylamine, diethylaminopropylamine, hexamethylenediamine, N-aminoethylpiperazine, bis-aminopropylpiperazine , Trimethylhexamethylenediamine, adipic dihydrazide, aliphatic polyamines such as dicyandiamide, dimer acid polyamide, maleic anhydride, dodecenylsuccinic anhydride, phthalic anhydride, pyromellitic anhydride,
Acid anhydrides such as trimellitic anhydride, cyclopentane / tetracarboxylic dianhydride, tetramethylene maleic anhydride, tetrahydrophthalic anhydride, methyl / tetrahydrophthalic anhydride, methylnadic anhydride, resole phenolic resin, novolac phenolic resin Phenol derivatives such as cresol novolak phenolic resin, resorcinol resin and xylene resin, polymercaptans such as 2,2-dimercaptodiethylether, 1,2-dimercaptopropane, bis (2-mercaptoethylsulfide), dimethylamino Methylphenol, 2,4
6-tri (dimethylaminomethyl) phenol, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1
-Benzyl-2-methylimidazole, 2-ethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1
-Cyanoethyl-2-isopropylimidazole, 1-
Cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole trimellitate, 2,
4-diamino-6- [2'-methylimidazolyl-
(1) ′]-ethyl-s-triazine, 1,3-dibenzyl-2-methylimidazolium chloride, 2-phenyl-4-methyl-5-hydroxymethylimidazole,
Tertiary amines such as 2-methylimidazole / triazine complex, 2-phenylimidazole / triazine complex and the like, boron trifluoride / monoethylamine complex compound, boron trifluoride / triethanolamine complex compound, trifluoride Lewis acid complexes such as boron / n-butyl ether complex compounds are exemplified. Among them, phenol derivatives are preferred because they have excellent reactivity and are excellent in wet heat resistance even in printed wiring board applications. It is preferable to use 0.5 to 500 parts by weight of a polymer-based curing agent such as a phenol derivative, polyamine, or polyamide based on 100 parts by weight of the epoxy resin, and 0.1 to 20 parts by weight of the other curing agents.

(C) Polyimide resin A polyimide resin is obtained by polycondensing a siloxane compound and / or a diamine compound having an amino group at both terminals with a tetracarboxylic dianhydride and imidizing the resulting polyamic acid by ring closure. It can be used if obtained. The polyimide preferably has a siloxane structure in its skeleton. The siloxane content of the polyimide resin is preferably 5 to 40% by weight, more preferably 7 to 30% by weight, and most preferably 10 to 25% by weight. If the siloxane content is less than 5% by weight, the solvent solubility is low, and if it exceeds 40% by weight, the synthesis becomes difficult.
Further, the polyimide resin has a structure in which structural units represented by the following formulas (1) and (2) are arranged, and a structure in which structural units represented by the following formulas (1) and (3) are arranged. Or a polyimide resin in which structural units represented by the following formulas (1), (2) and (3) are arranged.

Embedded image [Wherein, W represents a direct bond, an alkylene group having 1 to 4 carbon atoms, —O—, —SO ₂ — or —CO—, and Ar ₁ represents ₂ represented by the following formula (4) or (5). Represents a valent aromatic group,

Embedded image (Wherein, X represents a direct bond, an alkylene group having 1 to 4 carbon atoms, —O—, —SO ₂ — or —CO—, Y represents an alkylene group having 1 to 4 carbon atoms, and Z ₁ And Z ₂ each represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms.), Ar ₂
Represents a divalent aromatic group having a hydroxyl group or a carboxyl group; R ₁ and R ₆ represent an alkylene group having 1 to 4 carbon atoms or a group represented by the following formula (6);

Embedded image (In the formula, Alk represents an alkylene group having 1 to 4 carbon atoms bonded to a silicon atom.), R _{2 to} R ₅ represent an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 32. . ]

In the present invention, a polyimide resin in which the structural units represented by the above formulas (1) and (2) are arranged, and a polyimide resin in which the structural units represented by the above formulas (1) and (3) are arranged. It is also a preferable embodiment that two or more kinds of the polyimide resin or the polyimide resin in which the structural units represented by the above formulas (1), (2) and (3) are arranged are used in combination. The polyimide resin is preferably contained in the total resin component in an amount of 5 to 80% by weight, more preferably 10 to 60% by weight. 5 polyimide content
If the amount is less than 80% by weight, the adhesive layer does not have flexibility.
If it exceeds, the adhesive strength decreases.

The tetracarboxylic dianhydride constituting the polyimide used in the present invention includes 2,3,3 ', 4'-
Biphenyltetracarboxylic dianhydride, 3,4,3 ',
4'-biphenyltetracarboxylic dianhydride, 2,3
2 ′, 3′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride,
Bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,3 ', 4'-Benzophenonetetracarboxylic dianhydride, 4,4'-biphthalic dianhydride and the like are preferred. Examples of the siloxane compound having an amino group at both terminals for providing a siloxane structure in the polyimide skeleton include 1,3-bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane. Siloxane,
α, ω-bis (3-aminopropyl) polydimethylsiloxane (eg, aminopropyl-terminated dimethylsiloxane tetramer to octamer), 1,3-bis (3-aminophenoxymethyl) -1,1,1 3,3-tetramethyldisiloxane, α, ω-bis (3-aminophenoxymethyl) polydimethylsiloxane, 1,3-bis (2-
(3-aminophenoxy) ethyl) -1,1,3,3-
Tetramethyldisiloxane, α, ω-bis (2- (3-
Aminophenoxy) ethyl) polydimethylsiloxane,
1,3-bis (3- (3-aminophenoxy) propyl) -1,1,3,3-tetramethyldisiloxane,
α, ω-bis (3- (3-aminophenoxy) propyl) polydimethylsiloxane and the like. Among the above siloxane compounds, those having a polymerization degree n of 1 to 32, preferably 1 to 16 are used in the case of polysiloxane.

The diamine compounds constituting the polyimide having the structure represented by the above formula (2) include 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 1,3-
Bis [1- (3-aminophenyl) -1-methylethyl] benzene, 1,3-bis [1- (4-aminophenyl) -1-methylethyl] benzene, 1,4-bis [1
-(3-aminophenyl) -1-methylethyl] benzene, 1,4-bis [1- (4-aminophenyl) -1-
Methylethyl] benzene, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis ( 4-aminophenoxy)
Benzene, 3,3′-bis (3-aminophenoxy) diphenyl ether, 3,3′-bis (4-aminophenoxy) diphenyl ether, 3,4′-bis (3-aminophenoxy) diphenyl ether, 3,4′-bis (4-aminophenoxy) diphenyl ether, 4,
4'-bis (3-aminophenoxy) diphenyl ether, 4,4'-bis (4-aminophenoxy) diphenyl ether, 3,3'-bis (3-aminophenoxy)
Biphenyl, 3,3'-bis (4-aminophenoxy)
Biphenyl, 3,4'-bis (3-aminophenoxy)
Biphenyl, 3,4'-bis (4-aminophenoxy)
Biphenyl, 4,4'-bis (3-aminophenoxy)
Biphenyl, 4,4'-bis (4-aminophenoxy)
Biphenyl, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy)
Phenyl] sulfone, 2,2-bis [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] hexa Fluoropropane, 2, 2
-Bis [3- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (3-aminophenoxy) phenyl] hexafluoropropane, 2,
2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 9,9-bis (3-aminophenyl) fluorene, 9,9-bis (4-aminophenyl) fluorene, 3,3′-diamino −2, 2 ', 4,
4'-tetramethyldiphenylmethane, 3,3'-diamino-2,2 ', 4,4'-tetraethyldiphenylmethane, 3,3'-diamino-2,2', 4,4'-tetrapropyldiphenylmethane, 3, 3'-diamino-
2,2 ′, 4,4′-tetraisopropyldiphenylmethane, 3,3′-diamino-2,2 ′, 4,4′-tetrabutyldiphenylmethane, 3,4′-diamino-2,
3 ′, 4,5′-tetramethyldiphenylmethane, 3,
4′-diamino-2,3 ′, 4,5′-tetraethyldiphenylmethane, 3,4′-diamino-2,3 ′, 4
5'-tetrapropyldiphenylmethane, 3,4'-diamino-2,3 ', 4,5'-tetraisopropyldiphenylmethane, 3,4'-diamino-2,3', 4
5′-tetrabutyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetramethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4, 4'-diamino-3,
3 ′, 5,5′-tetrapropyldiphenylmethane,
4,4′-diamino-3,3 ′, 5,5′-tetraisopropyldiphenylmethane, 4,4′-diamino-3,
3 ′, 5,5′-tetrabutyldiphenylmethane, 4,
4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3 '
-Dimethyldiphenylmethane, 4,4'-diamino-
3,3′-diethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetramethoxydiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraethoxydiphenylmethane, 4,4'-diamino-
3,3 ′, 5,5′-tetrapropoxydiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraisopropoxydiphenylmethane, 4,4′-diamino-3,3 ′, 5 5'-tetrabutoxydiphenylmethane, 4,4'-diamino-3,3'-dimethoxydiphenylmethane, 4,4'-diamino-3,3'-diethoxydiphenylmethane and the like.

The diamine compounds constituting the polyimide represented by the above formula (3) include 2,5-dihydroxy-p-phenylenediamine, 3,3'-dihydroxy-4,4'-diaminodiphenyl ether, 3 '
-Dihydroxy-3,4'-diaminodiphenyl ether, 3,3'-dihydroxy-4,4'-diaminobenzophenone, 3,3'-dihydroxy-4,4'-diaminodiphenylmethane, 3,3'-dihydroxy-4,
4'-diaminodiphenyl sulfone, 2,2'-bis [3-hydroxy-4- (4-aminophenoxy) phenyl] propane, bis [3-hydroxy-4- (4-aminophenoxy) phenyl] methane, 3, 3′-dicarboxy-4,4′-diaminodiphenyl ether, 4,
3'-dicarboxy-3,4'-diaminodiphenyl ether, 3,3'-dicarboxy-4,4'-diaminobenzophenone, 3,3'-dicarboxy-4,4'-
Diaminodiphenylmethane, 3,3'-dicarboxy-
4,4′-diaminodiphenyl sulfone, 4,4′-dicarboxy-3,3′-diaminodiphenyl sulfone,
3,3'-dicarboxybenzidine, 2,2'-bis [3-carboxy-4- (4-aminophenoxy) phenyl] propane, bis [3-carboxy-4- (4-aminophenoxy) phenyl] methane and the like Is mentioned. The diamine compound constituting the above formulas (2) and (3) is 2
More than one species may be used in combination.

The polyimide used in the present invention can be produced, for example, as follows. When the tetracarboxylic dianhydride and the diamine compound are used as raw materials, they may be used in an organic solvent, if necessary, in the presence of a catalyst such as tributylamine, triethylamine, triphenyl phosphite (20 parts by weight of the reaction product). Below), a method of heating directly to 100 ° C. or higher, preferably 180 ° C. or higher to obtain a polyimide directly, and reacting tetracarboxylic dianhydride and a diamine compound in an organic solvent at 100 ° C. or lower to obtain a polyimide precursor. After obtaining the polyamic acid, p
A method of adding a dehydration catalyst such as toluenesulfonic acid (1 to 5 times the molar amount of tetracarboxylic dianhydride) and performing imidization by heating to obtain a polyimide, or a method of converting this polyamic acid to acetic anhydride or propionic anhydride , An anhydride such as benzoic anhydride, a dehydration ring closure agent such as a carbodiimide compound such as dicyclohexylcarbodiimide and, if necessary, a ring closure catalyst such as pyridine, isoquinoline, imidazole and triethylamine. (2 to 10 times the molar amount of the anhydride) and then chemically ring-closed at a relatively low temperature (from room temperature to about 100 ° C.).

The organic solvent used in the above reaction is N
-Methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, sulfolane, hexamethylphosphoric triamide,
Aprotic polar solvents such as 1,3-dimethyl-2-imidazolidone, phenol, cresol, xylenol,
Phenol solvents such as p-chlorophenol are exemplified. If necessary, benzene, toluene, xylene, methyl ethyl ketone, acetone, tetrahydrofuran, dioxane, monoglyme, diglyme, methyl cellosolve, cellosolve acetate, methanol, ethanol, isopropanol, methylene chloride, chloroform, trichlene, nitrobenzene, etc. Can also be used as a mixture. A diamine compound having a siloxane structure in its skeleton can be obtained by replacing the diamine compound with the siloxane compound having an amino group at both ends.

The weight average molecular weight of the polyimide thus obtained is preferably in the range of 5,000 to 500,000, more preferably 40,000 to 200,000. If the weight average molecular weight is less than 5,000, the film-forming properties are poor, and if it exceeds 500,000, the solvent solubility is reduced and the processability is poor. The weight average molecular weight is based on the GPC method, using tetrahydrofuran as an eluent,
Shodex 80M × 2 (manufactured by Showa Denko KK) as a column
And using polystyrene as a standard substance. Further, the glass transition point is preferably in the range of 50 to 250 ° C, more preferably 80 to 230 ° C. The glass transition point was measured by a differential thermal analysis in a nitrogen atmosphere at a heating rate of 10 ° C./min. If the glass transition point is lower than 50 ° C., the heat resistance of the adhesive layer is insufficient. If the glass transition point is higher than 250 ° C., workability such as requiring a high temperature when attaching a film to a circuit deteriorates.

The adhesive layer may contain an inorganic or organic filler, if necessary. For example, silica, alumina, silicon nitride, boron nitride, titanium oxide,
Insulating calcium carbonate, silicone, fluorine resin, etc.
It can be added for the purpose of adjusting thermal conductivity, dielectric properties, viscoelasticity and the like. The preferred average diameter is 0.01 to 10 μm, more preferably 0.01 to 1 μm. The preferable addition amount is 1 to 70% by weight of the total resin solids.

The first embodiment of the coverlay film of the present invention can be obtained by applying an adhesive paint to the release film and drying. The second embodiment is obtained by laminating an adhesive layer containing the above-mentioned components on the insulating plastic film. The lamination is performed by (1) directly applying an adhesive paint to the insulating plastic film and drying. And (2) a method in which the adhesive layer formed on the peelable film is bonded to an insulating plastic film. Since the cover lay film of the present invention is adhered to a printed circuit board by bonding, it is necessary to control the heating conditions during heating during drying so that the adhesive layer can be maintained in a semi-cured state (B stage). It is. The adhesive layer paint is (a)
It is prepared by dissolving the components (b) and (c) in an organic solvent.
N-methyl-2-pyrrolidone, N, N
Amide solvents such as -dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide;
Examples thereof include sulfur solvents such as dimethyl sulfoxide and dimethyl sulfone; phenol solvents such as phenol, cresol and xylenol; acetone, tetrahydrofuran and pyridine. The thickness of the adhesive layer formed as described above after drying is preferably from 3 to 80 μm, and more preferably from 10 to 50 μm.

The cover lay film thus obtained is used by sticking it on a circuit surface such as a flexible printed circuit board. In particular, when a releasable film is used, it can be used after being adhered to the circuit surface, peeling the releasable film, and then adhering to the circuit surface of another flexible printed circuit board. This is a preferred embodiment for use as a coverlay film for a multilayer flexible printed circuit board.

[0023]

The present invention will be described below with reference to examples. Synthesis Example 1 In a flask equipped with a stirrer, 10.33 g (52 mmol) of 3,4′-diaminodiphenyl ether and 1,3-
Bis (aminophenoxymethyl) -1,1,3,3,-
18.23 g (48 mmol) of tetramethyldisiloxane, 32.22 g (100 mmol) of 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride and N
-Methyl-2-pyrrolidone (NMP) (300 ml) was introduced under ice temperature, and stirring was continued for 1 hour. Next, this solution was reacted at room temperature for 3 hours to synthesize a polyamic acid. 50 ml of toluene and 1.0 g of p-toluenesulfonic acid are added to the obtained polyamic acid, and the mixture is heated to 160 ° C. The imidization reaction is performed while separating water azeotropic with toluene.
Time went. Toluene is distilled off, the obtained polyimide varnish is poured into methanol, and the obtained precipitate is separated, crushed, washed, and dried, thereby obtaining a compound represented by the formula (1) or (2). 54.3 g (yield 95%) of the resulting polyimide resin was obtained. When the infrared absorption spectrum was measured, typical imide absorptions were observed at 1718 and 1783 cm ^-1 . Table 1 shows the measurement results of the molecular weight and the glass transition point.

Synthesis Example 2 16.10 g (39 mmol) of 2,2-bis [4- (aminophenoxy) phenyl] propane and 3,3'-dicarboxy-4,4'-diaminodiphenylmethane 1.2
5 g (5 mmol), 1,3-bis (aminophenoxymethyl) -1,1,3,3-tetramethyldisiloxane 21.25 g (56 mmol) and 3,3 ′, 4,4 ′
-Benzophenonetetracarboxylic dianhydride 32.22
g (100 mmol) and 300 ml of N-methyl-2-pyrrolidone (NMP) in the same manner as in Synthesis Example 1 to obtain a polyimide comprising the structural units of the formulas (1), (2) and (3). 62.5 g of resin (93% yield) was obtained.
When the infrared absorption spectrum was measured, 1718, 17
A typical imide absorption was observed at 83 cm ^-1 . Table 1 shows the measurement results of the molecular weight and the glass transition point.
It was shown to.

Synthesis Example 3 33.65 g (82 mmol) of 2,2-bis [4- (aminophenoxy) phenyl] propane, 13.84 g (18 mmol) of an aminopropyl-terminated dimethylsiloxane octamer and 2,3 ′, 29.42 g (100 mmol) of 3,4'-biphenyltetracarboxylic dianhydride and N-
Using 300 ml of methyl-2-pyrrolidone (NMP), 67.4 g of a polyimide resin comprising the structural units of the above formulas (1) and (2) in the same manner as in Synthesis Example 1 (yield: 92).
%). When the infrared absorption spectrum was measured,
Typical imide absorptions were observed at 718 and 1783 cm ^-1 . Table 1 shows the measurement results of the molecular weight and the glass transition point.

Synthesis Example 4 30.38 g (74 mmol) of 2,2-bis [4- (aminophenoxy) phenyl] propane and 2.33,3'-dicarboxy-4,4'-diaminodiphenylmethane 2.3
5 g (8 mmol) and 13.64 g (18 mmol) of an aminopropyl-terminated dimethylsiloxane octamer and 2,
29.42 g (100 mmol) of 3 ', 3,4'-biphenyltetracarboxylic dianhydride and N-methyl-2-
Synthesis example 1 using 300 ml of pyrrolidone (NMP)
67.8 g (yield 94) of a polyimide resin comprising the structural units of the above formulas (1), (2) and (3)
%). When the infrared absorption spectrum was measured,
Typical imide absorptions were observed at 718 and 1783 cm ^-1 . The molecular weight and glass transition point were measured, and the results are shown in Table 1.

Synthesis Example 5 31.98 g (78 mmol) of 2,2-bis [4- (aminophenoxy) phenyl] propane, 16.95 g (22 mmol) of an octameric aminopropyl-terminated dimethylsiloxane and 3,3 ′, 35.83 g (100 mmol) of 4,4'-diphenylsulfonetetracarboxylic dianhydride
And N-methyl-2-pyrrolidone (NMP) 300 ml
And 78.7 g of a polyimide resin comprising the structural units of the above formulas (1) and (2) in the same manner as in Synthesis Example 1.
(97% yield). When the infrared absorption spectrum was measured, typical imide absorptions were observed at 1718 and 1783 cm ^-1 . Table 1 shows the measurement results of the molecular weight and the glass transition point.

Synthesis Example 6 30.44 g (74 mmol) of 2,2-bis [4- (aminophenoxy) phenyl] propane and 3,3'-dicarboxy-4,4'-diaminodiphenylmethane 1.1
2 g (4 mmol), 16.85 g (22 mmol) of an aminopropyl-terminated dimethylsiloxane octamer,
Using 35.83 g (100 mmol) of 3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride and 300 ml of N-methyl-2-pyrrolidone (NMP),
75.0 g of a polyimide resin comprising the structural units of the formulas (1), (2) and (3) in the same manner as in Synthesis Example 1.
(93% yield). When the infrared absorption spectrum was measured, typical imide absorptions were observed at 1718 and 1783 cm ^-1 . Table 1 shows the measurement results of the molecular weight and the glass transition point.

Synthesis Example 7 1,3-bis (3-aminophenoxy) benzene
13 g (89 mmol), 8.14 g (11 mmol) of an aminopropyl-terminated dimethylsiloxane octamer and 3,
Using 20.02 g (100 mmol) of 3 ′, 4,4′-diphenylethertetracarboxylic dianhydride and 300 ml of N-methyl-2-pyrrolidone (NMP),
47.1 g (93% yield) of a polyimide resin comprising the structural units of the above formulas (1) and (2) in the same manner as in Synthesis Example 1.
I got When the infrared absorption spectrum was measured, 171
At 8,1783 cm ^-1 typical imide absorption was observed. Table 1 shows the measurement results of the molecular weight and the glass transition point.

Synthesis Example 8 1,3-bis (3-aminophenoxy) benzene
55 g (81 mmol) and 3,3′-dihydroxy-
2.06 g (9 mmol) of 4,4′-diaminodiphenylmethane, 8.05 g (10 mmol) of an aminopropyl-terminated dimethylsiloxane octamer and 3,3 ′, 4,4′-
Diphenyl ether tetracarboxylic dianhydride 20.0
Using 2 g (100 mmol) and 300 ml of N-methyl-2-pyrrolidone (NMP), a polyimide comprising the structural units of the formulas (1), (2) and (3) in the same manner as in Synthesis Example 1. 45.6 g of resin (91% yield) was obtained. When the infrared absorption spectrum was measured, 1718,
A typical imide absorption was observed at 1783 cm ^-1 .
Table 1 shows the measurement results of the molecular weight and the glass transition point.

[0031]

[Table 1]

Next, a coverlay film of the present invention was prepared as follows. The weights shown below are solid component weights. (Example 1) 20 parts by weight of bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., trade name: Epicoat 828), 20 parts by weight of bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., trade name: Epicoat 1001) 20 parts by weight of a cresol novolak type phenol resin (trade name: CRG951, manufactured by Showa Polymer Co., Ltd.), 0.5 parts by weight of 2-ethyl-4-methylimidazole, Synthesis Example 1 above
Was dissolved in tetrahydrofuran (hereinafter abbreviated as “THF”) to prepare an adhesive having a resin solid content of 43% by weight. This has a thickness of 25μ
m was coated on a polyimide film (product name: Upilex 25S, manufactured by Ube Industries, Ltd.) so that the thickness after drying was 50 μm, and dried at 130 ° C. for 3 minutes to prepare a coverlay film of the present invention.

Example 2 A coverlay film of the present invention was produced in the same manner as in Example 1 except that the polyimide resin obtained in Synthesis Example 1 was replaced with the polyimide resin obtained in Synthesis Example 2. Example 3 A coverlay film of the present invention was produced in the same manner as in Example 1 except that the polyimide resin obtained in Synthesis Example 1 was replaced with the one obtained in Synthesis Example 3 above. (Example 4) A coverlay film of the present invention was produced in the same manner as in Example 1 except that the polyimide resin obtained in Synthesis Example 1 was replaced with the polyimide resin obtained in Synthesis Example 4.

Example 5 A coverlay film of the present invention was produced in the same manner as in Example 1 except that the polyimide resin obtained in Synthesis Example 1 was replaced with the polyimide resin obtained in Synthesis Example 5. (Example 6) A coverlay film of the present invention was produced in the same manner as in Example 1, except that the polyimide resin obtained in Synthesis Example 1 was replaced with the polyimide resin obtained in Synthesis Example 6.

Example 7 A coverlay film of the present invention was produced in the same manner as in Example 1 except that the polyimide resin obtained in Synthesis Example 1 was replaced with the polyimide resin obtained in Synthesis Example 7. Example 8 A coverlay film of the present invention was produced in the same manner as in Example 1 except that the polyimide resin obtained in Synthesis Example 1 was replaced with the polyimide resin obtained in Synthesis Example 8 above.

Example 9 The procedure of Example 1 was repeated except that 50 parts by weight of the polyimide resin obtained in Synthesis Example 1 was replaced with 50 parts by weight of the polyimide resin of Synthesis Example 1 and 50 parts by weight of the polyimide resin of Synthesis Example 2. Similarly, a coverlay film of the present invention was produced. Example 10 Polyimide resin 50 obtained in Synthesis Example 1
A coverlay film of the present invention was produced in the same manner as in Example 1 except that the parts by weight were changed to 50 parts by weight of the polyimide resin of Synthesis Example 1 and 50 parts by weight of the polyimide resin of Synthesis Example 3.

(Comparative Example 1) Bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., trade name: Epicoat 8)
28) 20 parts by weight, bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., trade name: Epicoat 100)
1) 20 parts by weight, 20 parts by weight of a cresol novolac type phenol resin (manufactured by Showa Polymer Co., Ltd., trade name: CRG951), 0.5 parts by weight of 2-ethyl-4-methylimidazole, NBR (manufactured by Zeon Corporation, trade name) : Nippol 10
01) was dissolved in 50 parts by weight of THF to obtain a resin solid content of 4%.
A 3% by weight adhesive was prepared. This was coated on a 25 μm thick polyimide film (trade name: Upilex 25S, manufactured by Ube Industries, Ltd.) so that the thickness after drying was 50 μm, and dried at 130 ° C. for 3 minutes, and a coverlay film for comparison was used. Was prepared.

(Comparative Example 2) Bisphenol A type epoxy resin (trade name: Epicoat 8 manufactured by Yuka Shell Epoxy Co., Ltd.)
28) 20 parts by weight, bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., trade name: Epicoat 100)
1) 20 parts by weight, 1 part by weight of 4,4'-diaminodiphenylsulfone, 2-ethyl-4-methylimidazole 0.1 part by weight.
5 parts by weight, 80 parts by weight of a carboxyl group-containing nitrile rubber (manufactured by Zeon Corporation, trade name: Nippol 1072),
10 parts by weight of a hydrogenated maleic acid-modified styrene-ethylene-styrene block copolymer (manufactured by Asahi Kasei Corporation, trade name: Tuftec MX-073) was dissolved in THF to prepare an adhesive having a resin solid content of 43% by weight. did. This is thickness 25
A polyimide film (product name: UPILEX 25S, manufactured by Ube Industries, Ltd.) having a thickness of 50 μm after drying was applied to a μm polyimide film, and dried at 130 ° C. for 3 minutes to prepare a coverlay film for comparison.

(Comparative Example 3) Bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., trade name: Epicoat 8)
28) 20 parts by weight, bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., trade name: Epicoat 100)
1) 20 parts by weight, 20 parts by weight of a cresol novolac type phenol resin (manufactured by Showa Polymer Co., Ltd., trade name: CRG951), 0.5 parts by weight of 2-ethyl-4-methylimidazole, nitrile rubber having a carboxyl group (Nihon Zeon Co., Ltd.) Manufactured by Nippol 1072) and 50 parts by weight of TH
F to prepare an adhesive having a resin solid content of 43% by weight. This was coated on a 25 μm thick polyimide film (trade name: Upilex 25S, manufactured by Ube Industries, Ltd.) so that the thickness after drying was 50 μm, and dried at 130 ° C. for 3 minutes, and a coverlay film for comparison was used. Was prepared.

(Preparation of Test Specimen for Evaluation) The coverlay film obtained above was placed on a glossy surface of a 35 μm-thick electrolytic copper foil (manufactured by Nikko Grade Foil, trade name: JTC foil) at 160 ° C. and 30 kg. The test pieces for evaluation of peel strength and solder heat resistance were prepared by laminating under press conditions of 30 cm / cm ² and 30 minutes. A test piece for evaluating the amount of exudation was prepared in the same manner as the test piece for evaluating the peel strength and the solder heat resistance, except that a hole having a diameter of 6 mm was formed in the coverlay film. 50mm between lines on 35μm thick electrolytic copper foil
A test specimen for an insulation test was prepared in the same manner as the test specimen for peel strength and solder heat resistance, except that a comb electrode of μm was formed and this copper foil was used.

(Evaluation of Test Specimens and Evaluation Results) The results of the evaluation of the test specimens according to the following evaluation methods are shown in Table 2. (1) Peel strength Peel strength was measured using the above-mentioned test specimen in accordance with JIS-C6481 (peeling strength). (2) Solder heat resistance According to JIS-C6481 (solder heat resistance), 25 m
The above m-square specimen was placed in an atmosphere of 22 ° C. and 90% RH for 2 hours.
After humidity control for 4 hours, the sample was immediately floated on a solder bath for 30 seconds, and the maximum temperature at which blistering and peeling did not occur was measured.

(3) Exudation Amount A 6 mm-diameter hole section of the above-mentioned test piece was inserted into a universal projector V-1.
Type 6 (manufactured by Nippon Kogaku Co., Ltd.) and Linear Scale AT-
Observation was performed using 11-FN200 (manufactured by Mitutoyo Corporation), and the amount of the adhesive leaking into the hole cross section was measured. (4) Insulation test The above test specimen was subjected to 100 at 156 ° C./85% RH.
After applying V for 1000 hours, the presence or absence of copper migration was observed using a microscope.

[0043]

[Table 2]

From the above results, the cover lay film of the present invention has a sufficient peel strength and a solder heat resistance temperature of 310 to 310.
As high as 350 ° C, the amount of adhesive exudation during hot pressing is small,
The occurrence of copper migration was not recognized, and all of the required characteristics required for the cover film for printed circuit boards were satisfied. On the other hand, in Comparative Example 1, the solder heat resistance temperature was as low as 250 ° C., the amount of bleeding was large, and copper migration occurred. In Comparative Example 2, the peel strength was weak, and copper migration occurred. In Comparative Example 3, the solder heat resistance temperature was as low as 290 ° C., and copper migration occurred.
None of the coverlay films of Comparative Examples simultaneously satisfied all of the required characteristics.

[0045]

The coverlay film of the present invention has adhesiveness,
It satisfies all of the practical characteristics of solder heat resistance and the small amount of bleeding generated at the time of heat and pressure, and thus has excellent bonding workability. At the same time, it has excellent insulation properties because no copper migration occurs. By using the cover lay film of the present invention, it is possible to improve the electrical reliability of the flexible printed circuit board and the like and the productivity at the time of manufacturing.
In particular, its application value is extremely high when applied to a circuit pattern with high density.

Claims (4)

[Claims] 1. A coverlay film in which an adhesive layer is laminated on one surface of an insulating plastic film or a peelable film, wherein the adhesive layer is (a) an epoxy resin, and (b)
A coverlay film for printed circuit boards, comprising a curing agent and (c) a polyimide resin. 2. The coverlay film according to claim 1, wherein the polyimide resin has a siloxane structure. 3. The coverlay film according to claim 1, wherein the siloxane content of the polyimide resin is 5 to 40% by weight. 4. The polyimide resin, wherein the structural units represented by the following formulas (1) and (2) are arranged, and the structural units represented by the following formulas (1) and (3): The cover according to claim 1, wherein the cover is a polyimide resin in which the structural units represented by the following formulas (1), (2) and (3) are arranged. Ray film. Embedded image [Wherein, W represents a direct bond, an alkylene group having 1 to 4 carbon atoms, —O—, —SO ₂ — or —CO—, and Ar ₁ represents ₂ represented by the following formula (4) or (5). A valent aromatic group, (Wherein, X represents a direct bond, an alkylene group having 1 to 4 carbon atoms, —O—, —SO ₂ — or —CO—, Y represents an alkylene group having 1 to 4 carbon atoms, and Z ₁ And Z ₂ each represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms.), Ar ₂
Represents a divalent aromatic group having a hydroxyl group or a carboxyl group; R ₁ and R ₆ represent an alkylene group having 1 to 4 carbon atoms or a group represented by the following formula (6); (In the formula, Alk represents an alkylene group having 1 to 4 carbon atoms bonded to a silicon atom.), R _{2 to} R ₅ represent an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 32. . ]