JPS62153371A - Adhesive composition for flexible printed circuit board - Google Patents

Abstract

PURPOSE:To provide the title compsn. having excellent bond strength, etc. after prolonged high-temperature exposure, by blending a copolymer of acrylonitrile, an hydroxyalkyl acrylate and N-methlolacrylammide, etc. with an epoxy compd. CONSTITUTION:80-99.5pts.wt. acrylonitrile or acrylic ester (A) is copolymerized with 0.1-5pts.wt. hydroxyalkyl (meth)acrylate and/or acrylamide (B) and 0.4-15 pts.wt. N-methylolacrylamide (C). 100pts.wt resulting aq. copolymer is blended with 20-60pts.wt. (on a solid basis) emulsion of a water-soluble epoxy compd. having epoxy groups (e.g., ethylene glycol diglycidyl ether) and/or a solid epoxy comd. to obtain the title adhesive compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an adhesive composition suitable for use in flexible printed circuit boards. Formation of metal foil-clad laminates made by bonding a non-woven sheet of a heat-resistant resin, a heat-resistant resin film, or a coverlay sheet made of a heat-resistant resin non-woven sheet, an adhesive, and a protective sheet with releasability. The present invention relates to an improved water-based acrylic adhesive for use.

BACKGROUND OF THE INVENTION In recent years, electronic devices have become smaller, lighter, and more dense, and demands for their performance have become increasingly sophisticated. As one of the countermeasures, flexible circuit boards, which enable electronic devices to be smaller, lighter, and more dense, have become rapidly popular.

A flexible printed circuit board is basically provided as a metal foil-clad laminate as described below. That is, using a film of a heat-resistant resin such as polyester resin, polyimide resin, polyamideimide resin, or polyparabanic acid resin as a base material, or a nonwoven sheet made of fibers of these resins,
A conductive metal foil such as copper or aluminum is laminated on the base material via an adhesive to provide a metal foil-clad laminate, which is then printed and wired in a predetermined pattern.

Also in this connection, cover lay sheets are used.

This is used in the final stage of the printing wiring processing process for the metal foil-clad laminates, and is used to prevent deterioration of the formed metal conductor wiring due to oxidation after the wiring pattern is formed by etching, etc. It is laminated on a flexible substrate for the purpose of This coverlay sheet is made by applying an adhesive to a heat-resistant resin film or non-woven sheet similar to that used as the base material for metal foil laminates, semi-curing, and then applying a polyolefin film or mold release treatment. It is provided with a protective sheet such as paper that has been pasted on it.

Adhesives for flexible metal foil-clad laminates and coverlay sheets (hereinafter collectively referred to as flexible substrates unless special distinction is required) have adhesive strength, heat resistance, flexibility, electrical insulation properties, etc. In addition to these characteristics, coverlay sheets are also required to have various other characteristics such as resin flow during lamination processing, so-called wiring part embedding ability, and shelf life in a semi-cured state.

Traditionally, adhesives that meet these requirements include acrylonitrile-butadiene rubber, butyral resin, and
Cross-linkable acrylic rubber system, nylon/epoxy system, acrylonitrile-butadiene/phenol resin system, carboxy-containing acrylonitrile-butadiene/epoxy resin system,
Various adhesives such as acrylic rubber/epoxy adhesives have been proposed. Among these adhesives, acrylonitrile-butadiene/phenol resin adhesives are widely used because they have a relatively well-balanced overall range of properties. Recently, acrylic rubber/epoxy adhesives have been attracting attention as they have been recognized for their excellent properties such as good electrical insulation, embeddability when used in coverlay sheets, and long shelf life. It became so.

However, since all of these adhesives are supplied as solutions of flammable organic solvents such as methyl ethyl ketone, toluene, acetone, and ethanol, they are difficult to bond with heat-resistant substrates and metal foils in the production of flexible circuit boards, and to maintain heat resistance. During processes such as applying the adhesive to the base material and semi-curing the adhesive, it is necessary to volatilize and remove these organic solvents. It was pointed out that this work was highly dangerous and required special consideration in terms of safety and occupational health.

From this perspective, a non-solvent emulsion polymerization type adhesive was finally developed, and its representative properties include basic performance such as adhesive strength, heat resistance, and flexibility, as well as the characteristics of acrylic. An emulsion polymerization type acrylic rubber/epoxy adhesive has been provided which has excellent electrical properties, embeddability when used in a coverlay sheet, and shelf life.

However, flexible substrates using this emulsion polymerization adhesive have problems such as insufficient solder heat resistance, which is thought to be due to hygroscopicity, problems with surface tanks, and insufficient solder heat resistance under high humidity conditions. . Regarding these problems, we have proposed patent application No. 126917-1983,
As proposed in No. 225419 and Japanese Patent Application No. 60-44700, it has become possible to reduce solder heat resistance and surface tack under high humidity conditions to a level that causes no practical problems.

Problems to be Solved by the Invention The electronic equipment industry has developed rapidly in recent years, and the performance requirements for flexible circuit boards are gradually becoming higher.

The uses of flexible circuit boards are wide-ranging, and deterioration of performance such as adhesive strength in applications where flexible circuit boards are exposed to high temperatures has become a problem. However, neither adhesives using organic solvents nor emulsion polymerization adhesives have satisfactory performance after long-term exposure to high temperatures.

As a result of intensive studies to solve the above problems, we have come to invent an adhesive composition for flexible printed circuit boards that has excellent adhesive strength after long-term exposure to high temperatures.Disclosure of the InventionFlexible printed circuits of the present invention The adhesive composition for substrates is
80-99.5 parts by weight of monomer group (A) consisting of acrylonitrile and acrylic esters and optionally added styrene, hydroquine alkyl (meth)acrylic esters and/or acrylamide (B)
) and 0.5-15 parts by weight of N-methylol acrylamide (C) are prepared. The water-soluble epoxy compound (E) having an epoxy group and/or the emulsion (F) of a solid epoxy compound having two or more epoxy groups in one molecule is added to the solid content of the copolymer ( D) A total of 20 to 60 parts by weight of (E) and (F') is blended to 100 parts by weight.

By using acrylonitrile as a compositional component of the first group of Nanatsuma (A), it imparts adhesive strength and resistance to organic chemicals used in printed circuit processing of flexible substrates, such as acetone, methylene chloride, and trichlene, to adhesives. and for that purpose preferably 10
-60 parts by weight may be used as necessary.

A part of this acrylonitrile component can be replaced with styrene if desired in order to impart further rigidity to the skeleton of the copolymer (D) which mainly functions as an adhesive. It can be used in place of % or less.

The composition of these acrylonitrile and styrene components can be changed as desired to make the entire adhesive composition glassy, in contrast to the flexible properties of acrylic esters, which are other components constituting the main components of the copolymer (D). Properties such as transition temperature can be adjusted.

As the acrylic esters which are other components of the Nanatsuma group (A) of the present invention, one or more of general acrylic esters such as ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate are used. be able to. This acrylic ester is a component that mainly provides adhesive strength to the adhesive and also provides flexibility, which is one of the other important performance requirements. The acrylic esters were added at 40% by weight per 100 parts by weight of the solid content of the aqueous copolymer (D).
It is preferable to use it within a range of 80 parts by weight.

These monomer group (A) constitutes the main component of the adhesive,
Although combinations can be made as appropriate within the above-mentioned preferred ranges, according to extensive practice by the present inventors, the adhesive composition as a whole including monomer components (B) and (C), etc. described below, It is desirable to select a transition point within the range of -30°C to 0°C that satisfies the above-mentioned performance requirements such as flexibility and chemical resistance. The composition of copolymer (D) based on 100 parts by weight of solid content is selected from the range of 80-99.5 parts by weight.

Furthermore, N-methylol acrylamide (C) is used as a component of the aqueous copolymer (D) of the adhesive composition of the present invention. The amount of N-methylol acrylamide (C) to be used with respect to 100 parts by weight of the solid content (D) of the aqueous copolymer is in the range of 0.4-15 parts by weight, preferably 0.
．． It is in the range of 5-10 parts by weight. If it is less than 0.4 parts by weight, there will be no effect on long-term heat resistance, and if it exceeds 15 parts by weight, moisture resistance and insulation resistance will decrease.

Next, in the present invention, hydroxyalkyl (meth)acrylic acid esters and/or acrylamides are further used as the (B) composition. These seven bastards
is a hydrophilic heptad, and a group of heptads in the present invention (
This is because these components together with A) and (B) become essential acids for stable copolymerization in water. These hydroxyalkyl (meth)acrylic esters include:
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3
-Hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, etc. can be used, and one or more of these can be used as a mixture.

Various types of acrylamide can be used, such as acrylamide and methacrylamide, and one or more types of these may also be used.

These hydrophilic monomers such as hydroxyalkyl acrylates and acrylamides may be used alone or in combination, and the amount thereof is selected from the range of 0.1 to 5 parts by weight. If this amount is less than o, i parts by weight, the hydrophilicity of the monomer in the aqueous polymerization system will be insufficient, making it impossible to ensure a stable monomer dispersion state during the polymerization operation, and in such a state, forcibly When polymerized,
Since the composition of the copolymer becomes non-uniform and the dispersion of the copolymer in the polymerization solution is unstable, it cannot be put to practical use as an adhesive for flexible substrates. On the other hand, if the amount of the hydrophilic monomer exceeds 5 parts by weight, the originally excellent properties of the composition of the present invention such as adhesiveness, heat resistance, flexibility, etc. will be impaired, and especially the solderability will be impaired. There is a significant decrease in heat resistance.

Copolymer (D) of the present invention comprising the above monomer group
The aqueous copolymerization solution can be produced by the following method. That is, a predetermined amount of potassium persulfate as a polymerization initiator is dissolved in distilled water at 70°C,
A mixed solution of separately prepared Nanatsuma groups (A), (B) and (C) of the present invention and distilled water is dropwise polymerized while stirring for about 3 to 4 hours, and the polymerization is completed over a further 6 to 4 hours. After that, the mixture is cooled to room temperature, excessive particles are filtered using a suitable furnace material, and the pH is adjusted to 7-9 using aqueous ammonia or the like. At this time, the solid content of the resin component in the aqueous copolymerization liquid is adjusted to 30 to 70 parts by weight of the entire reaction system, that is, within a range in which the copolymerization reaction can be carried out satisfactorily.

In the present invention, the adhesive composition of the present invention can be obtained by directly blending and dissolving an emulsion of a water-soluble epoxy resin and/or a solid epoxy compound in the thus prepared reaction solution.

In addition, in the copolymerization operation of the polymer, a chain transfer agent or the like may be added according to a conventional method, or a dispersant may be added as long as it does not impair the characteristics of the resulting adhesive composition for use in flexible substrates. It can also be used supplementarily depending on the situation.

Another component of the adhesive composition of the present invention is a water-soluble epoxy compound (E) having two or more epoxy groups in one molecule.
and/or an emulsion (F) of a solid epoxy compound having two or more epoxy groups in one molecule.

Examples of the water-soluble epoxy compound (E) include epoxy compounds having a hydrophilic ether bond in the main chain of the molecule, such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether having 9 or less carbon atoms in the main chain: glycerol polycricidyl ether,
One or more types of polyepoxy compounds having an ether bond and an alcoholic hydroxyl group in the molecule, such as dicrycerol polyglycidyl ether and sorbitol polyglycidyl ether, are used.

Moreover, the emulsion (F) of a solid epoxy compound is an emulsion of novolac type epoxy, an emulsion of cresol type epoxy,
One or more types of emulsions such as polyhydric phenol epoxy compounds having a phenol skeleton in the molecule, such as bisphenol doll epoxy emulsions and bisphenol F type epoxy emulsions, are used.

This water-soluble epoxy compound (E) and/or.

The blending ratio of the solid epoxy compound emulsion (F) is appropriately blended depending on the required degree of adhesive surface tackiness, but the preferred range is this water-soluble epoxy compound (E).
The amount of the total epoxy compound including the solid content of the emulsion (F) of the solid epoxy compound is 100% of the aqueous copolymer (D).
It ranges from 20 to 60 parts by weight. When the amount is less than this range, it is difficult to obtain sufficient heat resistance and chemical resistance in the adhesive composition, and when it exceeds this range, not only the chemical resistance decreases but also the bending durability becomes insufficient.

The adhesive composition of the present invention obtained as described above is generally an aqueous adhesive having a pH of 7-9 and a viscosity of 50 to 4000 centipoise. This adhesive is applied onto a heat-resistant resin film or non-woven sheet base material to a film thickness of usually 10 to 80 μm (dry base), and then dried and the resin is cured to obtain the desired flexible substrate. .

The drying and curing conditions for the adhesive are, for example, a temperature of 80'C to IS for the coverlay sheet.

The resin is dried and semi-cured using hot air at 0.5°C and a residence time of 0.5 to 2°C, and a releasable polyolefin film or release paper is attached to the semi-cured resin surface to produce a product.

This coverlay sheet is laminated onto a board on which wiring has been formed on the user's side, and then the temperature is 160℃ to 180℃.
, pressure is 10ky/cd to 60 kg/c! .

By hot pressing for 30 to 90 minutes, the adhesive is completely cured and the bonding between the wiring board and the coverlay sheet is completed.

On the other hand, in the production of metal foil-clad laminates, after the adhesive has been semi-cured in the same manner as in the case of the coverlay sheet described above, rolled copper foil with a thickness of 5 μm to 80 μm, electrolytic copper foil, etc. After laminating foil, rolled aluminum foil, etc., heat at 100°C.
Or, while in contact with a metal roll heated to 100℃, apply a linear pressure of 3-50 k with a heat-resistant rubber roll or cotton roll.
Pressure bonding is carried out at about g/c1n, and the lamination is cured. Thereafter, post-curing is usually performed for 3 to 48 hours in an atmosphere of 80° C. to 200° C. to completely cure the product, thereby obtaining a metal foil-clad laminate.

However, the usage conditions shown here are just examples, and it is natural that the manufacturing conditions will vary depending on the coating machine used, the structure and specifications of the pressure roll, etc., and the optimal conditions should be determined at the time of manufacturing. In any case, as long as the adhesive of the present invention is used, unlike solvent-based adhesives, organic solvents will not volatilize during the manufacturing process, and manufacturing workers will be free from inhalation of volatilized solvents and the risk of fire. Ru.

In addition, the flexible printed circuit board using the adhesive of the present invention has excellent soldering heat resistance, insulation resistance, folding durability, adhesive strength, and chemical resistance, and has excellent adhesive strength especially after long-term heat resistance tests. The adhesive of the invention exhibits extremely useful effects industrially.

Examples and supplements Supplementary explanation will be added below while showing examples.

The characteristics of the printed circuit boards shown in Examples and Comparative Examples were evaluated according to the following method.

a. Peel strength The adhesive strength between the copper foil and the base heat-resistant film was measured based on IPC-FC-241A. In embodiments of the invention:
The temperature of the copper conductor wiring surface on which the printed circuit is formed and the normal state is 20
It means the test after being left for 48 hours at 65 degrees Celsius relative humidity.

b. Solder heat resistance The wiring surface (coverlay sheet laminated side) was brought into contact with solder and floated in a solder bath at 260° C. for 60 seconds, and then the appearance was observed. Here, the term "after moisture resistance" is used as a guideline for water resistance and moisture resistance, and the circuit board is heated to 40℃ and 95%
After being left for 1 hour at RH, it was taken out, and after wiping off moisture with gauze etc., it was floated in a solder bath as described above, and its appearance was observed.

C1 chemical resistance Based on JIS-C-6481, the test piece was
After immersing it in acetone and methylene chloride for 15 minutes at room temperature, it was taken out and its appearance was observed.

d. Folding strength Using an MIT type repeated bending tester, the test piece was so
The number of times the conductor was bent until the conductor stopped conducting was measured under a load of 0.5 oz.

e. Insulation resistance In accordance with JIS-C-6481, the volume resistivity under normal conditions (after being left at a temperature of 2°C and a relative humidity of 65% for 96 hours) was measured.

f. Long-term heat resistance The test piece was heat-treated at 150° C. for 240 hours, and then the peel strength described in item a0 was measured.

Example 1 30 parts by weight of acrylonitrile, 10 parts by weight of ethyl acrylate
Parts by weight of butyl acrylate Ss Mfjr, 3 parts by weight of 2-hydroxyethyl methacrylate, and 21 parts by weight of N-methylolacrylamide were mixed in distilled water to prepare a monomer group mixture.

Next, a predetermined amount of potassium persulfate as a polymerization initiator was added at 70%
3. Prepare an aqueous solution dissolved in distilled water at ℃, and add the previously prepared monomer group mixture to this aqueous solution while stirring.
The mixture was added dropwise over a period of 5 hours, and after the completion of the addition, polymerization was continued for 4.5 hours to complete the reaction.

The reaction solution was then cooled to room temperature and filtered to remove excessive particles to obtain an aqueous copolymer solution containing 50% by weight of the resin component.

°The obtained aqueous copolymerization liquid has a pH of 16 and a viscosity of 105.
centiboise, and separately the glass transition point of the resin component is D.
The temperature was -10°C as measured by SC method. Diethylene glycol diglycidyl ether (trade name: Denacol EX-851) was added to 100 parts by weight of this aqueous copolymer D.
, manufactured by Nagase Sangyo Co., Ltd.) was mixed and dissolved in an aqueous copolymerization liquid, and further, an emulsion of bisphenol A type epoxy (trade name: Epolge W 7 EA-3, NV = 5) was mixed and dissolved in an aqueous copolymerization liquid.
0%.

(manufactured by Kanebo NSC Co., Ltd.) was mixed and dissolved to obtain an adhesive composition of the present invention.

This adhesive composition liquid was applied to a polyimide film (manufactured by E.I. Dapon Co., Ltd., trade name, Kapton) to a thickness of approximately 25 μm (dry base) using a reverse coater, dried, and semi-cured (temperature After heating at 120°C for 5 minutes, electrolytic copper foil with a thickness of 65μ (manufactured by Fukuda Metal Co., Ltd.) was applied.
(trade name T8) was laminated and pressed under the conditions of a linear pressure of 5 kg/cm and a roll temperature of 140°C, and then post-cured at 160°C for 2 hours to obtain a flexible copper-clad laminate.

Further, the adhesive composition of the present invention obtained in this example was coated on a 50 μm thick polyimide film (E.I. DuPont product: trade name, Kapton) using a reverse roll coater.
The coating was applied to a thickness of approximately 50 μm (dry base), dried and semi-cured (temperature: 120° C., residence time: 5 minutes), and a 25 μm thick polyester film was laminated thereon to prepare a coverlay sheet.

Using this and the previously prepared flexible steel clad laminate, a test pattern printed circuit was processed using the subtract method to obtain a flexible printed circuit board. The characteristics of this circuit board were evaluated for each of the above items.

The press conditions for Naori Barley sheet are press pressure 30
kg/i, temperature was 160° C., and pressing time was 30 minutes.

As a result of the evaluation, the peel strength was 1.8 kg/a under normal conditions.
n. After a long-term heat resistance test, it was 1.2 kg/cm, which was very excellent. In addition, the solder heat resistance was good both under normal conditions and after moisture absorption treatment, and no abnormality was observed even after immersion in chemicals.

The folding test was also carried out an average of 160 times, and the insulation resistance was 1014Ω.

Example 2 15 parts by weight of acrylonitrile, 15 parts by weight of styrene, 615 parts by weight of butyl acrylate, 11 parts by weight of 2-hydroxypropyl methacrylate, 1 part by weight of acrylamide, and 0.5 parts by weight of N-methylol acrylamide were mixed in distilled water. A mixed solution of one group of Nanatsuma was prepared.

Copolymerization was carried out in the same manner as in Example 1, and the resin component was 40%.
A % by weight aqueous copolymer solution was obtained. The obtained aqueous copolymerization liquid had a pH of 8.1, a viscosity of 180 centipoise, and a glass transition point of -22°C as measured by DSC method.

To 100 parts by weight of this aqueous copolymerization liquid, 10 parts by weight of sorbitol tetraglycidyl ether (manufactured by Nagase Sangyo Co., Ltd., trade name: Denacol Eχ-6l1) was mixed and dissolved, and further an orthocresol novolac type epoxy resin emulsion was added. (Manufactured by Nagase Sangyo Co., Ltd.: Product name Denacol EM-
125Nv=25%) were mixed and dissolved to obtain an adhesive composition liquid of the present invention.

This adhesive composition liquid is applied to a 50μ thick polyamide-imide film (a film made of a polymer obtained by the method described in Japanese Patent Publication No. 56-44891) to a thickness of about 40μ (dry base) using a reverse roll coater. After drying and semi-curing at a temperature of 140°C and a residence time of 2 minutes, rolled copper foil with a thickness of 30 μm (manufactured by Nikko Gould Co., Ltd.) was dried and semi-cured.
(trade name: AN-02) were laminated, pressed under the conditions of a linear pressure of 10 Y/f and a roll temperature of 11 o C, and then post-cured at 130 C for 16 hours to obtain a flexible steel-clad laminate.

Furthermore, the adhesive composition of the present invention obtained in this example was coated on a polyamide-imide film similar to that used for the above-mentioned copper-clad laminate using a reverse roll coater to a thickness of 70 mm.
Apply to μ (dry base), temperature 130℃
After drying and semi-curing under conditions of a residence time of 7 minutes, a release paper (manufactured by Fujimori Industries Co., Ltd., trade name: Vinasheet) was attached to obtain a coverlay sheet.

Using this and the previously prepared flexible steel clad laminate, a test pattern printed circuit was processed using the subtract method to obtain a flexible printed circuit board.

The press conditions for the coverlay sheet are a press pressure of 50
kg/i, the temperature was 170°C, and the pressing time was 40 minutes. The evaluation results show that the peel strength is 1.6 kg/cI under normal conditions.
n, 0.9 kg/ca after long-term heat resistance test. Solder heat resistance was good both under normal conditions and after humidity resistance, and no abnormality was observed even after immersion in chemicals. - Average bending strength is 170 times.
The insulation resistance was 10'3Ω.

Comparative Example 1 30 parts by weight of acrylonitrile, 10 parts by weight of ethyl acrylate
Heavy parts, butyl acrylate 55 parts by weight, 2-hydroxyethyl methacrylate 3 parts by weight, acrylamide 1
．． 8 parts by weight and 0.2 N-methylol acrylamide
Parts by weight were mixed in distilled water to prepare a monomer group mixture. This monomer group mixture was copolymerized in the same manner as in Example 1 to obtain an aqueous copolymer solution containing 50% by weight of the resin component. The resulting aqueous copolymer solution had a pH of Z99, a viscosity of 110 centipoise, and a glass transition point of -10°C as measured by DSC. This aqueous copolymer solution was blended, coated, and processed in exactly the same manner as in Example 1 to obtain a flexible printed circuit board. As a result of evaluating the characteristics of this circuit board for each of the above items, it was found that when the amount of N-methylacrylamide added is low, the peel strength is normally i, 2
kl/cm, 0.2'Kg/cm after long-term heat resistance test
It was low. In addition, although the solder heat resistance was good under normal conditions, blistering occurred after absorbing moisture. Folding durability is 1 on average
The insulation resistance after 30 cycles was 1014Ω.

Comparative Example 2 9 parts by weight of acrylonitrile, 5 parts by weight of styrene, 67 parts by weight of butyl acrylate, 1 part by weight of 2-hydroxypropyl methacrylate, 1 part by weight of acrylamide, and N
- 17 parts by weight of methylol acrylamide was mixed in distilled water to prepare a monomer group mixture. This monomer group mixture was copolymerized in the same manner as in Example 1, and the resin component was 4
A 0% by weight aqueous copolymer solution was obtained. The resulting aqueous copolymer solution had a pH of 8.2, a viscosity of 300 centipoise, and a glass transition point of -21°C as measured by DSC. This aqueous copolymer solution was blended, coated, and processed in exactly the same manner as in Example 2 to obtain a flexible printed circuit board. As a result of evaluating the characteristics of this circuit board for each of the above items, it was found that if the amount of N-methylolacrylamide added was too large, the peel strength under normal conditions was 0.9 #/am.
, 0.1kl after long-term heat resistance test? /α or less, which was so bad that it was almost unusable. In addition, the solder heat resistance caused blisters both under normal conditions and after moisture absorption. The average folding resistance was 1011Ω after 100 folds.

Claims (1)

[Claims] (1) Monomer group consisting of acrylonitrile and acrylic esters and optionally added styrene (
80-99.5 parts by weight of A); 0.1-5 parts by weight of hydroxyalkyl (meth)acrylates and/or acrylamides (B); and 0.1 parts by weight of N-methylol acrylamide (C). Prepare an aqueous copolymer (D) consisting of 4 to 15 parts by weight, and add to it a water-soluble epoxy compound (E) having two or more epoxy groups in one molecule and/or two or more in one molecule. The emulsion (F) of the solid epoxy compound having the above epoxy group is mixed with (E) and (
An adhesive composition for a flexible printed circuit board, comprising 20 to 60 parts by weight of F) in total.