JP2010150437A - Adhesive composition, and cover lay film and flexible copper-clad laminate, both prepared by using the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition which is excellent in adhesiveness to a flexible film such as a polyimide film and which, when applied to a cover lay film used for a flexible printed circuit board, gives excellent storage stability to the cover lay film. <P>SOLUTION: The adhesive composition includes a thermoplastic polyurethane resin, an epoxy resin, and an epoxy resin curing agent. The thermoplastic polyurethane resin has an acid value of less than 5 mgKOH/g and a weight average molecular weight of 80,000-800,000. Preferably, the epoxy resin has two or more epoxy groups per molecule. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adhesive composition, and more particularly to an adhesive composition that can be preferably used as an adhesive for a flexible printed wiring board (hereinafter also referred to as “FPC”). Adhesive film that has good adhesion to wiring boards, solder heat resistance and resin flowability during heat bonding required as an adhesive for FPC, and does not cause defects in product appearance such as warping of the substrate after bonding, and The present invention relates to an adhesive composition used for them, and belongs to the electronic material technology.

In recent years, with the diversification of electronic devices such as miniaturization and high density, demand for flexible circuit boards or flexible printed wiring boards is increasing. Under such circumstances, high integration and multilayering are also progressing in the manufacture of flexible printed circuit boards.
The flexible copper-clad laminate is a structure in which copper foil is bonded to one or both sides of a flexible insulating base film via an adhesive layer. -A highly reliable polyimide film is often used. Further, this flexible copper-clad laminate is an FPC in which a conductive circuit is formed on a copper foil through steps such as resist layer formation, exposure, development, etching, and resist layer peeling.
These FPCs have adhesives for bonding the insulating base film of the flexible copper clad laminate and the copper foil, coverlay adhesives, interlayer adhesives, etc. for the purpose of protecting and insulating the conductive circuit. Adhesives, semiconductor sealants and the like are widely used.
Conventionally, various adhesives containing an epoxy resin and a thermoplastic resin having high reactivity have been proposed as those used for bonding an insulating base film and a metal, insulating base films, and metals. For example, Patent Document 1 proposes a carboxyl group-containing acrylonitrile butadiene rubber / epoxy resin adhesive. Patent Document 2 proposes a glycidyl group-containing elastomer / epoxy resin adhesive. Patent Document 3 proposes a carboxyl group-containing ethylene acrylic elastomer / epoxy resin adhesive. In Patent Document 4, a nylon / epoxy resin adhesive is proposed. Patent Document 5 proposes a polyester polyurethane resin / epoxy resin adhesive having an acid value. Patent Document 6 proposes a polyesteramide resin / epoxy resin adhesive having an acid value. The methods shown in these patents generally use a reactivity between the carboxyl groups of rubber and elastomer components and an epoxy resin, thereby realizing a rapid curing reaction and excellent adhesion. Widely used in.
JP-A-6-49427 JP 2001-354936 A JP-A-7-235767 Japanese Patent No. 3718357 JP 2005-244139 A JP 2006-152015 A

  However, in the methods disclosed in Patent Documents 1 to 4, the adhesiveness between the constituent rubber or elastomer and the polyimide resin is insufficient, and peeling is likely to occur, resulting in a problem of insulation reliability. In addition, in the adhesive composition using a high acid value polyurethane resin or polyester amide resin shown in Patent Documents 5 and 6, an adhesive obtained by applying and drying an adhesive on an insulating film such as polyimide, although the adhesive strength is excellent. As a cover lay film, there is a problem in that the curing reaction of the adhesive proceeds due to the heat history during storage or transportation when performing storage or transportation. When the cover lay film having undergone the curing reaction is heated and bonded to the copper foil, the resin flow-out property is poor, so that the circuit groove cannot be embedded sufficiently and the circuit insulation cannot be maintained. Moreover, since adhesiveness with copper foil also worsens, there existed a problem that the peeling strength fell and the peeling of the contact bonding layer in the heating process in a solder reflow furnace occurred. This phenomenon is due to the fact that the carboxyl group, epoxy group, and amide group in the rubber and elastomer components constituting the adhesive proceed with the epoxy resin even at a relatively low temperature, and the melt viscosity during heat bonding is too high. It is because it became.

  The present invention solves the above-described problems, and an object thereof is to improve the adhesive strength to a flexible film such as a polyimide film. Moreover, when used for FPC, the adhesive composition which is excellent in the storage stability of a coverlay film is provided.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a thermoplastic polyurethane resin and an epoxy resin having substantially no acid value and having a weight average molecular weight in a specific range. The present inventors have found that high adhesiveness to polyimide is expressed and the storage stability of the coverlay film is further improved. When the adhesive composition of the present invention was used for FPC, it was found that the resin composition was excellent in adhesiveness and resin flowability during heat bonding, and the present invention was completed.

  That is, the adhesive composition according to the present invention is an adhesive composition containing a thermoplastic polyurethane resin, an epoxy resin, and an epoxy resin curing agent, and the acid value of the thermoplastic polyurethane resin is 5 mgKOH / g. And a weight average molecular weight of 80,000 to 80,000.

  The epoxy resin preferably has two or more epoxy groups in one molecule.

  It is preferable that content of the said epoxy resin is 50-300 mass parts with respect to 100 mass parts of said thermoplastic polyurethane resins.

  A coverlay film, wherein the adhesive composition according to any one of the above is applied to one side of a polyimide film.

  A flexible copper-clad laminate comprising the adhesive composition according to any one of the above, wherein a copper foil is bonded to at least one surface of a polyimide film.

  As described above, the adhesive composition according to the present invention comprises a thermoplastic polyurethane resin, an epoxy resin, and an epoxy resin curing agent that have substantially no acid value and a weight average molecular weight within a specific range. contains. Therefore, high adhesiveness is expressed with respect to a polyimide film. Moreover, it is excellent in the storage stability in the state of the coverlay film apply | coated to the insulating film by controlling the reactivity of a thermoplastic polyurethane resin and an epoxy resin. Further, when used for FPC, it has high adhesiveness and excellent resin flow-out at the time of heat bonding.

  An embodiment of the present invention will be described as follows, but the present invention is not limited to this.

-Adhesive composition The adhesive composition according to the present invention has substantially no acid value and has a weight average molecular weight of 80,000 to 800,000, a thermoplastic polyurethane resin, an epoxy resin and an epoxy resin. Each of the resins is as follows.

  Details of the thermoplastic polyurethane resin used in the present invention will be described. The thermoplastic polyurethane resin used in the present invention plays a role of increasing the adhesive strength between an insulating film such as polyimide and a copper foil. The thermoplastic polyurethane resin used in the present invention is composed of various polyols and polyisocyanates, has an acid value of less than 5 mgKOH / g, and a weight average molecular weight of 80,000 to 80,000. It is.

  Any known compound can be used as the polyol component constituting the thermoplastic polyurethane resin used in the present invention. For example, polyether diol, polyester diol, polycaprolactone diol, polycarbonate diol, castor oil, acrylic polyol, polybutadiene diol and the like can be mentioned. Polyether diols and polyester diols are preferred.

  Examples of the polyether diol include polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol. The polyester diol is produced by a condensation reaction of a polyol and a polybasic acid. Examples of the polyol component include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl. Glycol, 3-methylpentanediol, and the like can be used. As the polybasic acid component, adipic acid, azelaic acid, sebacic acid, isophthalic acid, terephthalic acid and the like can be used.

  As the polyisocyanate component constituting the thermoplastic polyurethane resin used in the present invention, any known compound can be used. For example, aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,4-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone disissocyanate, tetramethylxylylene diene Aliphatic polyisocyanates such as isocyanate are exemplified. Aromatic polyisocyanates are preferred.

  The acid value of the thermoplastic polyurethane resin used in the present invention is less than 5 mgKOH / g, and the polyurethane resin is characterized by substantially low reactivity with an epoxy resin due to a carboxyl group. That is, even after the adhesive composition of the present invention has been heat-cured and the reaction has been sufficiently completed and the entire adhesive has formed a crosslinked structure, cross-linking by carboxyl groups in the thermoplastic polyurethane resin used in the present invention. It means that no structure is formed. As an index of reactivity with the epoxy resin, the acid value is less than 5 mgKOH / g. Preferably it is less than 3 mgKOH / g, and it is especially preferable that it is 0.1-1 mgKOH / g. When a thermoplastic polyurethane resin having an acid value of 5 mgKOH / g or more is used, the reaction between the thermoplastic polyurethane resin and the epoxy resin is likely to occur at a relatively low temperature. The crosslinking reaction proceeds according to the history. For this reason, since the melt viscosity of the resin becomes too high at the time of heat bonding in the copper foil laminating step of the coverlay, the resin is not sufficiently embedded in the circuit groove and the circuit insulation cannot be maintained. Moreover, since adhesiveness with copper foil also worsens, adhesive strength falls.

  The weight average molecular weight of the thermoplastic polyurethane resin used in the present invention is 80,000-80,0000. The weight average molecular weight is preferably 85,000 to 500,000, and more preferably 90,000 to 250,000. When the weight average molecular weight is less than 80,000, the melt viscosity of the adhesive composition at the time of heat bonding in the copper foil laminating process of the coverlay becomes low, and the resin flowability at the time of heat bonding becomes too high. Since the resin is covered on the connection contact portion, the energization becomes insufficient. When the weight average molecular weight exceeds 80,0000, the melt viscosity of the resin at the time of heat bonding in the copper foil laminating step is too high, so that the circuit embedding property is deteriorated and the insulation reliability is lowered. Furthermore, the peel strength decreases. The weight average molecular weight of the present invention is a value measured by gel permeation chromatography (hereinafter abbreviated as “GPC”). Usually, in the case of GPC measurement, a polystyrene gel column or the like was used with chloroform or tetrahydrofuran as a mobile phase, and the molecular weight value was determined by a polystyrene conversion value or the like.

Next, the epoxy resin used in the present invention will be described.
The epoxy resin used in the present invention plays a role for developing the heat resistance and high adhesive strength of the cured adhesive.
Examples of epoxy resins include bisphenol A diglycidyl ether and oligomers thereof, orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester Glycidyl esters such as succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, trimellitic acid triglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol di Glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol Lug glycidyl ether, tetraphenyl glycidyl ether ethane, triphenyl glycidyl ether ethane, polyglycidyl ethers of sorbitol, but glycidyl ethers such as polyglycidyl ethers of polyglycerol include, without being limited thereto. In addition, a novolac type epoxy resin such as a phenol novolac epoxy resin, an o-cresol novolac epoxy resin, or a bisphenol A novolac epoxy resin can be used.

Examples of epoxy resins include brominated bisphenol A type epoxy resins with flame retardancy, phosphorus containing epoxy resins, dicyclopentadiene skeleton containing epoxy resins, naphthalene skeleton containing epoxy resins, anthracene type epoxy resins, tertiary butyl catechol type An epoxy resin, a triphenylmethane type epoxy resin, a tetraphenylethane type epoxy resin, a biphenyl type epoxy resin, a bisphenol S type epoxy resin, or the like can be used.

  In the adhesive composition according to the present invention, the epoxy resin has two or more epoxy groups in one molecule in order to form a cross-linked structure by reaction with the epoxy resin curing agent and to develop high heat resistance. It is preferable to use one. When an epoxy resin having one epoxy group is used, sufficient solder heat resistance may not be obtained due to a low degree of crosslinking with the epoxy resin curing agent.

  The blending ratio of the thermoplastic polyurethane resin and the epoxy resin in the adhesive composition of the present invention is preferably such that the epoxy resin is contained in the range of 50 to 300 parts by mass with respect to 100 parts by mass of the thermoplastic polyurethane resin. More preferably, the epoxy resin is in the range of 60 to 250 parts by mass. Good performance is exhibited when the blending ratio is within this range. When the blending ratio of the epoxy resin is less than 50 parts by mass, the elastic modulus of the adhesive after the curing treatment is lowered, and thus sufficient heat resistance characteristics cannot be obtained. On the other hand, when the blending ratio of the epoxy resin exceeds 300 parts by mass, the blending ratio of the thermoplastic polyurethane resin is decreased, so that the adhesive strength with an insulating film or a copper foil is lowered.

Next, the epoxy resin curing agent used in the present invention will be described.
Since the epoxy resin curing agent used in the present invention forms a crosslinked structure by reaction with the epoxy resin, it has an effect of improving the heat resistance of the adhesive. In addition, it plays a role of improving adhesion with copper.

  The epoxy resin curing agent used in the present invention is an amine curing agent such as aliphatic diamine, aliphatic polyamine, cycloaliphatic diamine and aromatic diamine, polyamidoamine curing agent, aliphatic polycarboxylic acid, alicyclic ring. Formula polycarboxylic acids, aromatic polycarboxylic acids and acid curing agents such as acid anhydrides thereof, basic active hydrogen curing agents such as dicyandiamide and organic acid dihydrazide, tertiary amine curing agents, imidazole Examples thereof include a curing agent, a polymercaptan curing agent, a novolac resin curing agent, a urea resin curing agent, and a melamine resin curing agent. Among these epoxy resin curing agents, one kind or a mixture of two or more kinds can be used.

  Examples of aliphatic diamine curing agents include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, polymethylenediamine, polyetherdiamine, 2,5-dimethylhexamethylenediamine, trimethylhexamethylene Examples include diamines.

  Examples of aliphatic polyamine curing agents include diethylenetriamine, iminobis (hexamethylene) triamine, trihexatetramine, tetraethylenepentamine, aminoethylethanolamine, tri (methylamino) hexane, dimethylaminopropylamine, diethylaminopropylamine, methyl And iminobispropylamine.

  Examples of cycloaliphatic diamine curing agents include mensendiamine, isophoronediamine, bis (4-amino-3-methyldicyclohexyl) methane, diaminodicyclohexylmethane, bis (aminomethyl) cyclohexane, N-ethylaminopiperazine, 3 , 9-bis (3-aminopropyl) 2,4,8,10-tetraoxaspiro (5,5) undecane, hydrogenated metaxylylenediamine, and the like.

  Examples of the aromatic diamine-based curing agent include metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diaminodiethyldiphenylmethane, and metaxylylenediamine.

  Examples of aliphatic polycarboxylic acid curing agents and acid anhydride curing agents include succinic acid, adipic acid, dodecenyl succinic anhydride, polyadipic acid anhydride, polyazelinic acid anhydride, polysebacic acid anhydride, and the like. .

  Examples of aliphatic polycarboxylic acid curing agents and acid anhydride curing agents include methyltetrahydrophthalic acid, methylhexahydrophthalic acid, methylheimic acid, hexahydrophthalic acid, tetrahydrophthalic acid, and trialkyltetrahydrophthalic acid. Methylcyclodicarboxylic acid and acid anhydrides thereof.

  Examples of aromatic polycarboxylic acid curing agents and acid anhydride curing agents include phthalic acid, trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, ethylene glycol glycol bistrimellitic acid, glycerol tristrimellitic acid and These acid anhydrides are mentioned.

  Examples of tertiary amine curing agents include benzyldimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol, tetramethylguanidine, triethanolamine, N, N'- Examples include dimethylpiperazine, triethylenediamine, and 1,8-diazabicyclo (5,4,0) undecane.

  Examples of imidazole compounds include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, and 2-phenyl-4. -Methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2 , 4-Diamino-6- [2'-undecylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1' )]-Ethyl-s-triazine, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-tria Diisocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5? And hydroxymethylimidazole.

  Examples of the polymercaptan-based curing agent include mercapto epoxy resins and mercaptopropionic acid esters.

  Examples of novolak curing agents include phenol novolac curing agents and cresol novolac curing agents.

  Among these curing agents, imidazole compounds, aromatic polycarboxylic acid curing agents, and novolak resin curing agents are preferable. More preferably, it is a melamine structure and guanamine structure-containing novolak resin-based curing agent, and generally available as trade names “Phenolite LA-7052”, “Phenolite LA-7054”, “ Phenolite LA-7551 "," Phenolite LA-1356 "," Phenolite LA-1398 "," Phenolite LA-3018 ", etc. are mentioned. Moreover, the brand name "YLH-969" by Japan Epoxy Resin Co., etc. are mentioned.

  The blending ratio of the epoxy resin curing agent according to the present invention is preferably such that the functional group equivalent of the epoxy resin curing agent is in the range of 0.2 to 2.5 with respect to the epoxy equivalent of 1 of the epoxy resin, 0.4 More preferably, it is in the range of -2.0. When the functional group equivalent of the epoxy resin curing agent is in the range of 0.2 to 2.5, the adhesive is sufficiently cured, and good adhesive strength and heat resistance can be obtained.

  The adhesive composition of the present invention is generally dissolved in a solvent and used as a solution-type adhesive, and the solvent is preferably one that dissolves a thermoplastic polyurethane resin, an epoxy resin, and an epoxy resin curing agent.

  Specific examples of the solvent include methanol, ethanol, i-propyl alcohol, n-propyl alcohol, i-butyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol methyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, Alcohol solvents such as diacetone alcohol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, aromatic solvents such as toluene, xylene, ethylbenzene, mesitylene, methyl acetate, ethyl acetate, ethylene glycol Ester solvents such as monomethyl ether acetate and 3-methoxybutyl acetate, chloroform, carbon tetrachloride, dichloromethane, trichloroethylene It is mentioned of chlorinated solvents. In addition, water, phenol, formic acid, acetic acid and the like added to improve the solubility of the nylon resin can be used.

In addition to the thermoplastic polyurethane resin, epoxy resin, and epoxy resin curing agent, the adhesive composition of the present invention may be optionally added within a range that does not impair the purpose of the present invention for various purposes such as improved adhesion and improved solution properties. It is possible to mix an agent. For example, resin components such as thermoplastic resins, thermoplastic elastomers and rubbers, polyurethane resin curing agents, coupling agents, antioxidants, UV absorbers, leveling agents, antifoaming agents, thickeners, flame retardants, fillers , Dyes, curing accelerators and the like. It is also possible to add and disperse filler components such as titanium oxide, zinc oxide, talc, calcium carbonate, aluminum hydroxide, carbon black and silica. Such additives can be added during or after dissolution of the raw material in the solvent.

  Examples of the resin component include acrylonitrile butadiene rubber, acrylic rubber, acrylic ethylene rubber, isoprene rubber, ethylene propylene rubber, ethylene propylene diene rubber, ethylene propylene α olefin rubber, ethylene vinyl acetate elastomer, polyester urethane elastomer, polyether urethane elastomer. , Polycarbonate urethane elastomer, styrene butadiene styrene elastomer, styrene isoprene styrene elastomer, styrene ethylene butylene styrene elastomer, styrene ethylene propylene styrene elastomer, polyester elastomer, polyethylene, polypropylene, polyacrylonitrile styrene, polymethyl methacrylate, polystyrene, polyvinyl alcohol, poly vinegar Vinyl, polyvinyl butyral, polycarbonate, polyacetal, fluorine resin, polyvinyl chloride, phenoxy resins, melamine resins, urea resins. Moreover, what modified | denatured these resin and gave the carboxyl group, the epoxy group, the isocyanate group, the hydroxyl group, the thiol group, etc. is mentioned.

  Examples of the curing agent for the polyurethane resin include polyisocyanate compounds, polyvalent carboxylic acid compounds, acid anhydrides thereof, and methylolated melamine compounds.

  Examples of coupling agents include vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N- 2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, Examples thereof include silane coupling agents such as imidazole silane compounds, titanate coupling agents, aluminate coupling agents, and zirconium coupling agents.

  Examples of antioxidants include 2,6-di-o-butyl-4-methylphenol, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate, Phenol antioxidants such as tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, dilarlyl-3,3′-thiodipropionate, dimyristyl-3,3 Examples include sulfur-based antioxidants such as' -dithiopropionate, phosphorus-based antioxidants such as trisnonylphenyl phosphite and tris (2,4-di-t-butylphenyl) phosphite.

  Examples of UV absorbers include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2-[(2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl Benzotriazole ultraviolet absorbers such as benzotriazole, benzophenone ultraviolet absorbers such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone and 2-hydroxy-4-n-octylbenzophenone, phenyl salicylate, etc. Salicylate UV absorbers, cyanoacrylate UV absorbers such as ethyl-2-cyano-3,3-diphenyl acrylate, oxalic anilide UV rays such as 2-ethoxy-2'-ethyl oxalic acid bisanilide Absorber, bis- [2,2,6,6-tetra And hindered amine ultraviolet absorbers such as methyl-4-piperidinyl] sebacate and bis- [N-methyl-2,2,6,6-tetramethyl-4-piperidinyl] sebacate.

  Examples of flame retardants include brominated flame retardants such as tetrabromobisphenol A, hexabromobenzene, decabromodiphenyl ether, hexabromocyclododecane, bis (pentabromophenyl) ethane, bis (tetrabromophthalimide) ethane, triphenyl phosphate , Aromatic phosphate ester flame retardants such as 2-ethylhexyl diphenyl phosphate, cresyl diphenyl phosphate, 1,3-phenylene bis (diphenyl phosphate), 1,3-phenylene bis (dixylenyl) phosphate, bisphenol A bis (diphenyl phosphate) ) Aromatic condensed phosphate esters such as tris (dichloropropyl) phosphate, halogen-containing phosphate ester flame retardants, red phosphorus flame retardants such as red phosphorus, aluminum hydroxide, water Magnesium, inorganic flame retardants such as antimony trioxide, silicon-based flame retardant, such as boron-based flame retardants and the like.

  Examples of curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-ethyl-4methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, Imidazole compounds such as 1-benzyl-2-methylimidazole, N, N-dimethylbenzylamine, N, N-diethylbenzylamine, piperidine, 1,8-diazabicyclo [5,4,0] undecene-7,1, Strong base compounds such as 5-diazabicyclo [4,3,0] nonene-5 and salts of these curing accelerators can be used. For example, phenol salts, octylates, oleates, formates, p-toluenesulfonates and the like can be mentioned.

  In the present invention, an adhesive composition containing a thermoplastic polyurethane resin, an epoxy resin, and an epoxy resin curing agent as essential components, together with the above-mentioned optional additives, is usually dissolved in the solvent as a solution-type adhesive. Used. The resin concentration when used as a solution-type adhesive is preferably 5 to 50% by mass, more preferably 10 to 40% by mass. If the resin concentration is within this range, the solution viscosity of the prepared adhesive is appropriate, and a uniform coating film can be formed when applied to a flexible film.

The FPC in which the adhesive composition of the present invention is used is formed by laminating the following cover lay film and a flexible copper-clad laminate.
Cover Lay Film Examples of the cover lay film include a polyimide film, a polyester film, a polyether ether ketone film, a polyphenylene sulfide film, and an aramid film. A film preferable for the present invention has a film thickness of 12 to 75 μm, and one having a surface treatment such as a corona discharge treatment, a low temperature plasma treatment or a sand blast treatment on one side or both sides of the film can also be used.

○ Flexible copper-clad laminate Flexible copper-clad laminate is a flexible film similar to the above-mentioned coverlay film and copper foil, bonded together by a method such as roll crimping or hot pressing using an adhesive, A copper foil layer is etched into a desired circuit pattern.

Examples of the method for bonding the flexible film and the copper foil using the adhesive composition include the following methods.
1) An adhesive solution is applied to a flexible film, dried to form an adhesive layer, and a copper foil is laminated thereon and heated to cure the adhesive layer between both substrates.
2) The adhesive solution is applied to a copper foil, dried to form an adhesive layer, and a flexible film is laminated thereon and heated to cure the adhesive layer between both substrates.
3) An adhesive solution is applied to a release film and dried to form an adhesive layer. Next, the adhesive layer and the flexible film are bonded together, the release film is peeled off, the exposed adhesive layer and the copper foil are bonded together, and then the adhesive layer between the two substrates is heated. Is cured.
4) The adhesive solution is applied to a release film and dried to form an adhesive layer. Next, the adhesive layer and the copper foil are bonded together, the release film is peeled off, the exposed adhesive layer and the flexible film are bonded together, and then the adhesive layer is heated between the two substrates by heating. Is cured.

  Examples of the release film include PET film, polyethylene film, polypropylene film, silicone release treated paper, polyolefin resin-coated paper, TPX film, and fluorine resin film that have been subjected to a release treatment.

  The adhesive solution is applied by a method such as brush coating, dip coating, spray coating, comma coating, knife coating, die coating, lip coating, roll coater coating, or curtain coating. The dry film thickness after coating is preferably 1 to 100 μm, more preferably 10 to 50 μm. The adhesive solution applied to the substrate is preferably dried by heating at a temperature of 40 to 250 ° C., more preferably 70 to 170 ° C., through a furnace such as hot air drying, far infrared heating, high frequency induction heating or the like. As a method for curing the adhesive layer in which the two substrates are overlapped, a method of heating through a furnace such as hot air drying, far-infrared heating, high-frequency induction heating or the like at a temperature of 80 to 250 ° C. is used. Among them, the heating method under pressure by a heating press is preferable for obtaining high adhesiveness.

Below, it demonstrates based on an Example.
Example 1
Thermoplastic polyurethane resin (trade name “Pandex T-5265H” manufactured by DIC Corporation) 100 parts by mass, bisphenol A type epoxy resin (trade name “Epicoat EP-1009” manufactured by Japan Epoxy Resin Co., Ltd.) 72 parts by mass, cured epoxy resin As an agent, 28 parts by mass of diaminodiphenylsulfone was dissolved in 800 parts by mass of methyl ethyl ketone as a solvent. Next, an adhesive laminate was prepared by the following method, and various tests were performed by the following methods. The results are shown in Table 1.

The abbreviations in Table 1 indicate the following.
・ Polyurethane resin A-1: Product name “Pandex T-5102M” (polyester polyurethane, weight average molecular weight 96,000, acid value 0.5 mgKOH / g) manufactured by DIC Bayer
-Polyurethane resin A-2: Product name "Pandex T-8157N" (polyether-based polyurethane, weight average molecular weight 160,000, acid value 0.1 mgKOH / g or less) manufactured by DIC Bayer
-Polyurethane resin A-3: DIC Corporation product name "Pandex T-5265H" (polyester polyurethane, weight average molecular weight 240,000, acid value 0.8 mgKOH / g)
・ Phenoxy resin: Product name “PKHH” manufactured by Sakai Kogyo Co., Ltd.
-Epoxy resin B-1: Product name "Epiclon N-685-EXP-S" (o-cresol novolak type epoxy resin, epoxy equivalent 207 g / equivalent) manufactured by DIC Corporation
-Epoxy resin B-2: Product name "Epicoat EP-1009" manufactured by Japan Epoxy Resin Co., Ltd. (bisphenol A type epoxy resin, epoxy equivalent 2850 g / equivalent)
Epoxy resin curing agent C-1: 4,4′-diaminodiphenyl sulfone (amine equivalent 124 g / equivalent)
-Epoxy resin curing agent C-2: Product name "Phenolite LA-1356" manufactured by Japan Epoxy Resin Co., Ltd. (melamine structure-containing novolac resin, hydroxyl group equivalent: 146 g / equivalent, nitrogen content: 19% by mass)

○ Measurement of weight average molecular weight Polyurethane resin was dissolved in tetrahydrofuran and measured with a gel permeation chromatograph equipped with a light scattering detector.
Apparatus: HLC-8120 (manufactured by Tosoh Corporation)
Column: 4 TSKgel SuperMultipore HZ-M (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran 0.35ml / min
Detector: RI
The molecular weight measured by GPC was converted based on the molecular weight of polystyrene.

○ Measurement of Acid Value 1 g of polyurethane resin was dissolved in 40 ml of methyl ethyl ketone, and an automatic titration device “AT-510” manufactured by Kyoto Denshi Kogyo Co., Ltd. was connected to “APB-510-20B” manufactured by the same as a burette. Potentiometric titration was performed using a 0.01 mol / L benzyl alcoholic KOH solution as a titration reagent, and the number of mg of KOH per 1 g of resin was calculated.

(Examples 2 to 7)
Adhesive compositions were obtained in the same manner as in Example 1 using the compositions described in Examples 2 to 7 in Table 1. Next, an adhesive laminate was prepared in the same manner as in Example 1, and various tests were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Examples 1-8)
Adhesive compositions were obtained from the compositions described in Comparative Examples 1 to 8 in Table 2 in the same manner as in Example 1. Next, an adhesive laminate was prepared in the same manner as in Example 1, and various tests were performed in the same manner as in Example 1. The results are shown in Table 2.

The abbreviations in Table 2 indicate the following.
Nitrile rubber 1: Product name “Nipol 1072J” manufactured by Zeon (carboxyl group-containing nitrile rubber acid value 39 mgKOH / g)
Nitrile rubber 2: Product name “Nipol DN225” (non-functional nitrile rubber) manufactured by Zeon
-Ethylene acrylic rubber 1: Product name “VacacG” (carboxyl group-containing ethylene acrylic rubber, acid value: 45 mgKOH / g) manufactured by Mitsui DuPont Polychemical Co., Ltd.
-Ethylene acrylic rubber 2: Made by Mitsui DuPont Polychemical Co., Ltd. Trade name "VamaDP" (non-functional ethylene acrylic rubber)
・ Polyurethane resin A-4: manufactured by Dainichi Seika Kogyo Co., Ltd. Trade name “Diferamine MAU-5022” (carbosil group-containing polyurethane, weight average molecular weight 65,000, acid value 9.0 mgKOH / g)

○ Preparation of Adhesive Sample Film thickness after drying on a polyimide film of 25 μm thickness (trade name “Kapton 100H” manufactured by Toray Industries, Inc.) using the adhesive solutions obtained in Examples 1 to 7 and Comparative Examples 1 to 8. Was applied at a temperature of 20 μm, dried at 40 ° C. for 2 minutes, then further dried at 140 ° C. for 2 minutes, and then a 35 μm-thick rolled copper foil was bonded to each other at 80 ° C., 0.3 MPa, 1 m / min. Laminated under conditions. Further, this polyimide film / adhesive layer / copper foil laminate was thermocompression bonded at 150 ° C. and 3 MPa for 2 minutes. Further, heat treatment was performed at 160 ° C. for 4 hours.

○ Measurement of peel adhesion strength The adhesion sample produced by the above method was cut into a width of 10 mm, and the peel adhesion strength when peeling the copper foil from the polyimide film was measured with a tensile tester under a temperature condition of 23 ° C. (Unit: N / mm). At this time, the tensile speed was 50 mm / min.

○ Resin flowability (initial)
Using the adhesive solutions obtained in Examples 1 to 7 and Comparative Examples 1 to 8, a polyimide film having a thickness of 25 μm (trade name “Kapton 100H” manufactured by Toray Industries, Inc.) so that the film thickness after drying becomes 20 μm. And then dried at 50 ° C. for 2 minutes and further dried at 150 ° C. for 5 minutes. Further, a 6 mmφ punch hole was made in the polyimide film coated with the adhesive, and then a rolled copper foil having a thickness of 35 μm was bonded and laminated under the conditions of 80 ° C., 0.3 MPa, and 1 m / min. Further, this polyimide film / adhesive layer / copper foil laminate was thermocompression bonded at 150 ° C. and 3 MPa for 2 minutes. The maximum outflow length (unit: mm) of the adhesive layer from the polyimide hole at this time was measured. It is determined that the outflow length is in the range of 0.20 to 0.05 mm.

○ Stability of resin flow (resin flow after storage of coverlay film)
After leaving the polyimide film coated with the adhesive in the same manner as above in an environment of 40 ° C. and 80% humidity for 20 days, a 6 mmφ punch hole was opened, and a laminate was produced in the same manner as the resin flow-out property, evaluated. Compared with the initial value, it is determined that the change is small and the outflow length is in the range of 0.20 to 0.05 mm.

  The adhesive composition of the present invention can be used for bonding resin films such as polyimide films and PET films, and metal foils such as copper and aluminum. In particular, it is useful for bonding an FPC or a flexible flat cable.

Claims (5)

  An adhesive composition containing a thermoplastic polyurethane resin, an epoxy resin, and an epoxy resin curing agent, wherein the thermoplastic polyurethane resin has an acid value of less than 5 mgKOH / g and a weight average molecular weight of 80, 000-80,0000 Adhesive composition characterized by the above-mentioned.   The adhesive composition according to claim 1, wherein the epoxy resin has two or more epoxy groups in one molecule.   3. The adhesive composition according to claim 1, wherein the content of the epoxy resin is 50 to 300 parts by mass with respect to 100 parts by mass of the thermoplastic polyurethane resin.   The coverlay film characterized by the adhesive composition of any one of Claims 1-3 being apply | coated to the single side | surface of a polyimide film.   A flexible copper-clad laminate comprising the adhesive composition according to any one of claims 1 to 3, wherein a copper foil is bonded to at least one surface of a polyimide film.