HK1169135B - Thermosetting adhesive composition, thermosetting adhesive sheet, method for producing same, and reinforced flexible printed wiring board - Google Patents

Description

Thermosetting adhesive composition, thermosetting adhesive sheet, method for producing the same, and reinforced flexible printed wiring board

Technical Field

The present invention relates to a thermosetting adhesive composition containing an acrylic copolymer, an epoxy resin and a curing agent for the epoxy resin.

Background

The strength of a terminal portion of a flexible printed wiring board including a polyimide film is improved by lining the terminal portion with a polyimide film, a glass epoxy plate, or a metal plate. In this case, the reinforcing plate and the polyimide of the flexible printed wiring board are usually bonded to each other by curing the thermosetting adhesive layer sandwiched therebetween. As such a thermosetting adhesive layer, an epoxy resin adhesive mainly containing a liquid epoxy resin, a solid epoxy resin, and a curing agent thereof is widely used in the field of flexible printed wiring boards (patent document 1).

However, this epoxy resin adhesive has a problem that the curing reaction proceeds slowly during storage at room temperature due to a large mixing ratio of the epoxy resin and the curing agent, and has a problem in terms of storage characteristics at room temperature. Therefore, in order to improve the storage characteristics at room temperature, an acrylic thermosetting adhesive composition has been proposed in which the amount of epoxy resin added is suppressed and an acrylic polymer is used as a main component (patent document 2, particularly, example 2).

Patent document 1: japanese laid-open patent publication No. H04-370996

Patent document 2: japanese patent laid-open publication No. 2007-9058.

Disclosure of Invention

However, in the case of the acrylic thermosetting adhesive composition of patent document 2, although the room temperature storage property is improved as compared with the conventional epoxy resin adhesive of patent document 1, when the composition is stored at room temperature for several months and then used for bonding a flexible printed circuit board to a resin sheet, a metal reinforcing plate or a glass epoxy resin plate, there is a possibility that the adhesion (peel strength) and the reflow soldering heat resistance are lowered, and improvement thereof is required.

An object of the present invention is to solve the above-described problems of the conventional art and to provide an acrylic thermosetting adhesive composition for adhesion in the field of flexible printed boards and the like, which can satisfactorily adhere a resin substrate such as a polyimide film to a polyimide film, a metal reinforcing plate, or a glass epoxy resin substrate, and can exhibit satisfactory room-temperature storage characteristics even after a lapse of several months.

As a curing agent for epoxy resin for improving the ordinary temperature storage stability of an epoxy resin adhesive, the present inventors focused on an organic acid dihydrazide which is not easily dissolved in an organic solvent and is solid at ordinary temperature and thus does not react with an epoxy resin, and which is caused to react by heating and melt-mixing with an epoxy resin, and studied the blending of an epoxy resin with an acrylic copolymer and an organic acid dihydrazide as a curing agent for an epoxy resin. In general, as a method for producing a film-like adhesive sheet, a method of coating the film-like adhesive sheet by dissolving and dispersing the above-mentioned complex in an organic solvent such as methyl ethyl ketone is used, but there is a problem that although the organic acid dihydrazide is not easily dissolved in the organic solvent, the organic acid dihydrazide is slowly dissolved in the organic solvent, and the dissolved curing agent is also dissolved in the epoxy resin, and thus the reaction proceeds. From such a viewpoint, it has been found that the dissolution of the organic acid dihydrazide in an organic solvent and the rapid progress of a thermosetting reaction can be suppressed with good balance during storage at room temperature by controlling the average particle diameter of the organic acid dihydrazide to a specific particle diameter range, and that the above object can be achieved by using, as an acrylic copolymer, a copolymer of an epoxy group-free (meth) acrylate monomer, an acrylonitrile monomer and an epoxy group-containing (meth) acrylate monomer in amounts within a specific range, and the present invention has been completed.

That is, the present invention provides a thermosetting adhesive composition comprising an acrylic copolymer (A), an epoxy resin (B) and a curing agent (C) for epoxy resin, wherein

The acrylic copolymer (A) is obtained by copolymerizing 65 to 75 mass% of an epoxy group-free (meth) acrylate monomer (a), 20 to 35 mass% of an acrylonitrile monomer (b), and 1 to 10 mass% of an epoxy group-containing (meth) acrylate monomer (c),

the curing agent for epoxy resin is organic acid dihydrazide particles having an average particle diameter of 0.5 to 15 μm. In the present specification, the term "(meth) acrylic acid" means "methacrylic acid" or "acrylic acid".

The present invention also provides a thermosetting adhesive sheet obtained by forming a thermosetting adhesive layer containing the thermosetting adhesive composition on a base film.

Further, the present invention provides a method for producing the thermosetting adhesive sheet, comprising:

a step of dispersing the curing agent (C) for epoxy resin in an organic solvent and dissolving the acrylic copolymer (A) and the epoxy resin (B) in an organic solvent to prepare a coating material for forming a thermosetting adhesive layer, and

and a step of applying the coating material for forming a thermosetting adhesive layer to a base film and drying the coating material to form a thermosetting adhesive layer.

The thermosetting adhesive composition of the present invention bonds a resin substrate such as a polyimide film to a metal plate such as a polyimide film, a glass epoxy resin, or stainless steel well (preferably 15N/cm or more), and exhibits good film storage characteristics at room temperature over a period of several months. Further, the solder paste exhibits a property of not swelling due to moisture absorption even after reflow soldering at 260 ℃ or higher.

Detailed Description

The thermosetting adhesive composition of the present invention contains an acrylic copolymer (A), an epoxy resin (B) and a curing agent (C) for epoxy resin.

In the present invention, the acrylic copolymer (a) is obtained by copolymerizing an epoxy group-free (meth) acrylate monomer (a), an acrylonitrile monomer (b), and an epoxy group-containing (meth) acrylate monomer (c) in order to provide film formability during film formation and to impart flexibility and toughness to a cured product.

The epoxy-free (meth) acrylate monomer (a) may be suitably selected from epoxy-free (meth) acrylate monomers used in conventional acrylic thermosetting adhesives suitable for the field of electronic devices, and examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, n-dodecyl methacrylate, and mixtures thereof, Isododecyl methacrylate, stearyl methacrylate, and the like. Among them, butyl acrylate and ethyl acrylate are preferably used.

The amount of the (meth) acrylate monomer (a) containing no epoxy group used in the preparation of the acrylic copolymer (a) is preferably 65 to 75% by mass, more preferably 65 to 70% by mass, because the basic properties are deteriorated when the amount is too small and the heat resistance tends to be deteriorated when the amount is too large.

The acrylonitrile monomer (b) is used to improve heat resistance.

Among all the monomers used for producing the acrylic copolymer (a), the amount of the acrylonitrile monomer (b) used is preferably 20 to 35% by mass, more preferably 25 to 30% by mass, because when it is too small, the heat resistance is lowered, and when it is too large, it tends to be difficult to dissolve in a solvent.

The epoxy group-containing (meth) acrylate monomer (c) is used to react with a curing agent for epoxy resin to form a three-dimensional crosslinked structure in a cured product of the thermosetting adhesive composition. When the three-dimensional crosslinked structure is formed, the moisture resistance and heat resistance of the cured product are improved, and for example, even when a reinforced flexible printed wiring board including a reinforcing resin sheet adhesively fixed to the flexible printed wiring board by a cured product of a thermosetting adhesive composition is subjected to a soldering treatment (for example, reflow soldering treatment) of 260 ℃ or higher, the expansion phenomenon due to moisture absorption can be prevented from occurring in the adhesive fixing portion. The epoxy group-containing (meth) acrylate monomer (c) may be suitably selected from monomers used in conventional acrylic thermosetting adhesives suitable for use in the field of electronic components, and examples thereof include Glycidyl Acrylate (GA) and Glycidyl Methacrylate (GMA). Among them, Glycidyl Methacrylate (GMA) is preferably used from the viewpoint of safety and easy availability to the market.

The amount of the epoxy group-containing (meth) acrylate monomer (c) used in the preparation of the acrylic copolymer (a) is preferably 1 to 10% by mass, and more preferably 3 to 7% by mass, because when the amount is too small, the heat resistance is lowered, and when the amount is too large, the peel strength tends to be lowered.

The acrylic copolymer prepared from the epoxy group-free (meth) acrylate monomer (a), the acrylonitrile monomer (b), and the epoxy group-containing (meth) acrylate monomer (c) as described above can be prepared by applying a known copolymerization method.

The acrylic copolymer (a) used in the present invention preferably has a weight average molecular weight of 500000 to 700000, more preferably 550000 to 650000, because when it is too small, the peel strength and heat resistance are reduced, and when it is too large, the solution viscosity tends to increase and the coatability tends to deteriorate.

The epoxy resin (B) constituting the thermosetting adhesive composition of the present invention is used to form a three-dimensional network structure, and is excellent in heat resistance and adhesiveness.

The epoxy resin (B) may be suitably selected from liquid or solid epoxy resins used in conventional epoxy resin thermosetting adhesives suitable for the field of electronic devices, and examples thereof include bisphenol a type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, hydrogenated bisphenol a type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, polyalkylene polyols (such as neopentyl glycol) polyglycidyl ether, tetraglycidyl diaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, tetraglycidyl-m-xylylenediamine, diglycidyl phthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate, vinylcyclohexene dioxide, epoxy resins in the form of a liquid or solid, and the like, 3, 4-epoxycyclohexylmethyl (3, 4-epoxycyclohexane) carboxylate, bis (3, 4-epoxy-6-methylcyclohexylmethyl) adipate, and the like.

The amount of the epoxy resin (B) used in the thermosetting adhesive composition of the present invention is preferably 5 to 30 parts by mass, more preferably 10 to 20 parts by mass, based on 100 parts by mass of the acrylic copolymer (a), because the heat resistance tends to be lowered when the amount is too small, and the adhesiveness tends to be lowered when the amount is too large.

In the thermosetting adhesive composition of the present invention, organic acid dihydrazide particles having an average particle diameter of 0.5 to 15 μm, preferably 1 to 5 μm are used as the curing agent (C) for epoxy resin which reacts with an epoxy group derived from the epoxy resin (B) and the epoxy group-containing (meth) acrylate monomer used in the preparation of the acrylic copolymer (A). The reason why the organic acid dihydrazide is used is that it is solid at room temperature, and therefore, the room temperature storage characteristics of the thermosetting adhesive composition can be improved. The reason why the average particle diameter of the organic acid dihydrazide particles is 0.5 to 15 μm is that if the average particle diameter is less than 0.5 μm, the organic acid dihydrazide particles are likely to be dissolved when an organic solvent is used for coating the thermosetting adhesive composition, and the storage property at room temperature is likely to be lowered, whereas if the average particle diameter is more than 15 μm, the coating property of the thermosetting adhesive composition is likely to be lowered, and further, since the particle size is large, there is a possibility that the particles cannot be sufficiently mixed when they are melted with an acrylic polymer or an epoxy resin.

Such an organic acid dihydrazide may be suitably selected from organic acid dihydrazides conventionally used as curing agents for epoxy resins, and examples thereof include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, iminodiacetic acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecane dicarboxylic acid dihydrazide, hexadecane dicarboxylic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2, 6-naphthalene carboxylic acid dihydrazide, 4' -bis (benzenedihydrazide), 1, 4-naphthalene carboxylic acid dihydrazide, 1, 3-bis (hydrazinocarbonylethyl) -5-isopropylhydantoin (アミキュア H (trade name) ("VD78H), The family of the drugs include, for example, the family of the drugs named "kazisu" (kojiki), the family of the drugs named "7, 11-octadecadien-1, 18-dicarbonhydrazide (アミキュア UDH (trade name)), the family of the drugs named" kazisu "(kojiki), and the family of the drugs named" trionychia citriodoride ". One of them may be used alone or two or more of them may be used in combination. Among them, adipic acid dihydrazide and 7, 11-octadecadienyl-1, 18-dicarbonhydrazide are preferably used because of their low melting point, excellent balance of curability, and easy availability.

The amount of the curing agent (C) for epoxy resin in the thermosetting adhesive composition of the present invention is preferably 4 to 20 parts by mass, more preferably 6 to 15 parts by mass, based on 100 parts by mass of the total of the acrylic copolymer (a) and the epoxy resin (B), because when the amount is too small, unreacted epoxy groups remain and crosslinking is insufficient, and thus heat resistance and adhesiveness are reduced, and when the amount is too large, excessive curing agent remains unreacted and thus heat resistance and adhesiveness tend to be reduced.

In the thermosetting adhesive composition of the present invention, in addition to the components described above, known additives such as a metal deactivator, an antifoaming agent, a rust preventive agent, and a dispersant which do not promote the dissolution of the organic acid dihydrazide may be blended as necessary within a range not impairing the effects of the present invention.

The thermosetting adhesive composition of the present invention can be prepared by uniformly mixing the acrylic copolymer (a), the epoxy resin (B), the curing agent (C) for epoxy resin, and other additives by a conventional method. The form of the polymer may be paste, film, dispersion, or the like. Among them, from the viewpoint of storage stability, handling properties when used, and the like, a thermosetting adhesive sheet is preferably used in which a thermosetting adhesive layer containing the thermosetting adhesive composition of the present invention is formed on a base film (release base) such as a polyethylene terephthalate film or a polyimide film in a thickness of 10 to 50 μm. The base film may be subjected to a peeling treatment with silicone or the like as necessary.

The method for producing a thermosetting adhesive sheet comprises the following steps of preparing a thermosetting adhesive layer-forming coating material and forming a thermosetting adhesive layer.

< preparation of coating Material for Forming thermosetting adhesive layer >

First, the thermosetting adhesive composition of the present invention is put into an organic solvent such as methyl ethyl ketone or toluene to have a viscosity suitable for a coating method, and the curing agent (C) for epoxy resin is dispersed in the organic solvent, while the acrylic copolymer (a) and the epoxy resin (B) are dissolved in the organic solvent, thereby preparing a coating material for forming a thermosetting adhesive layer. In this case, in order to improve the storage stability at room temperature of the thermosetting adhesive sheet, it is preferable that 70% by mass of all the organic acid dihydrazide particles be dispersed as solid particles in the thermosetting adhesive layer-forming coating material at room temperature.

< thermosetting adhesive layer Forming step >

Next, the thermosetting adhesive layer-forming coating material is applied to the base film by a bar coater, a roll coater or the like so as to have a dry thickness of 10 to 50 μm, and dried by a conventional method, thereby forming a thermosetting adhesive layer. Thus, a thermosetting adhesive sheet can be obtained.

The thermosetting adhesive composition and the thermosetting adhesive sheet described above can be preferably applied to the field of electronic components. In particular, the thermosetting adhesive sheet is preferably used for adhering and fixing a terminal portion of a flexible printed wiring board or the like to a reinforcing resin sheet having a thickness of 50 μm to 2mm such as polyethylene terephthalate, polyimide, glass epoxy resin, stainless steel, aluminum or the like for forming a liner of the flexible printed wiring board, and by applying the thermosetting adhesive sheet, a reinforced flexible printed wiring board in which the terminal portion of the flexible printed wiring board and the reinforcing resin sheet are adhered and fixed by the thermosetting material of the thermosetting adhesive layer of the present invention from which the base film of the thermosetting adhesive sheet is removed can be obtained.

Examples

The present invention will be described in more detail with reference to examples.

Examples 1 to 10 and comparative examples 1 to 8

(1) Preparation of acrylic copolymer

Acrylic copolymers containing the monomers shown in tables 1 and 2 were prepared. The weight average molecular weights of these acrylic copolymers are shown in tables 1 and 2.

(2) Preparation of coating Material for Forming thermosetting adhesive layer

To the obtained acrylic copolymer solution, epoxy resin (B) and organic acid dihydrazide as curing agent (C) for epoxy resin were added in the mixing ratios shown in tables 1 and 2, and uniformly mixed to prepare a coating material for forming a thermosetting adhesive layer as a thermosetting adhesive composition. The viscosity of the obtained coating material was measured by a B-type viscometer and shown in tables 1 and 2.

(3) Production of thermosetting adhesive sheet

The obtained thermosetting adhesive layer-forming coating material was applied to a polyethylene terephthalate film subjected to a peeling treatment, and dried in a drying oven at 50 to 130 ℃ to form a thermosetting adhesive layer having a thickness of 35 μm, thereby producing a thermosetting adhesive sheet.

(4) Evaluation of coatability of coating Material for Forming thermosetting adhesive layer

In the production of the thermosetting adhesive sheet, the coatability of the thermosetting adhesive layer-forming coating material was evaluated according to the following criteria. The obtained evaluation results are shown in tables 1 and 2.

AA: the adhesive has uniform thickness, no texture is formed during coating, and no curing agent particles are observed in appearance

A: although no texture was formed in the coating, the case where the curing agent particles were observed on the film after drying

B: the coating texture and thickness are not uniform

C: the solution is in gel form and can not be applied

(5) Evaluation of peeling Strength

The thermosetting adhesive sheet obtained immediately after cutting into a rectangle (5 cm. times.10 cm) of a predetermined size was temporarily attached to a polyimide film (175AH, (Tokao) カネカ) having a thickness of 175 μm by a laminator set at 80 ℃, and then the thermosetting adhesive layer was exposed by removing the base film. The exposed thermosetting adhesive layer was laminated with a 50 μm-thick polyimide film (200H, デュポン Co.) having the same size from above, heated and pressurized at 170 ℃ and 2.0MPa for 60 seconds, and then held in an oven at 140 ℃ for 60 minutes.

Further, the thermosetting adhesive layer of the thermosetting adhesive sheet cut into a rectangular shape (5 cm. times.10 cm) was pressed against a SUS304 plate of 0.5mm or a glass epoxy plate of 1mm in thickness and temporarily adhered, and then the base film was removed to expose the thermosetting adhesive layer. The exposed thermosetting adhesive layer was laminated with a rectangular polyimide film (5 cm. times.10 cm) having a thickness of 50 μm from above, heated and pressurized at 170 ℃ and a pressure of 2.0MPa for 60 seconds, and then held in an oven at 140 ℃ for 60 minutes.

Then, for the polyimide film, a 90-degree peel test was performed at a peel speed of 50mm/min, and the force required for peeling was measured. The results obtained are shown in tables 1 and 2. The peel strength is practically desirably 10N/cm. Further, it is desirable that the difference between the peel strength after 6 months of storage at room temperature and the initial peel strength is less than-30%. Therefore, when the difference is less than 2N/cm, it is regarded as good at room temperature storage properties, and when it exceeds, it is regarded as bad.

The same peel strength was evaluated for a thermosetting adhesive sheet stored at 25 ℃ at room temperature for 6 months. The results obtained are shown in tables 1 and 2.

[ Table 1]

[ Table 2]

< examination of the results of Table 1 and Table 2 >

In the thermosetting adhesive sheets of examples 1 to 7, the acrylic copolymer (A) was obtained by copolymerizing 65 to 75 mass% of the epoxy group-free (meth) acrylate monomer (a), 20 to 35 mass% of the acrylonitrile monomer (b), and 1 to 10 mass% of the epoxy group-containing (meth) acrylate monomer (c), and the curing agent for epoxy resin was organic acid dihydrazide particles having an average particle diameter of 0.5 to 15 μm, and thus the coating property, the initial peel strength, and the room temperature storage property were satisfactory.

In the thermosetting adhesive sheet of example 8, the weight average molecular weight of the acrylic copolymer (a) was 30 ten thousand, which is lower than that of the thermosetting adhesive sheets of examples 1 to 7, and therefore, the peel strength and heat resistance of the whole sheet were lowered although the room temperature storage property was good.

In the thermosetting adhesive sheet of example 9, since the weight average molecular weight of the acrylic copolymer (a) was 90 ten thousand and higher than that of the thermosetting adhesive sheets of examples 1 to 7, the coating texture was present on the surface of the adhesive sheet, and the thickness was not uniform, but the room temperature storage property was good.

In the case of the thermosetting adhesive sheet of example 10, the organic acid dihydrazide had a larger average particle size than the thermosetting adhesive sheets of examples 1 to 7, and therefore, the coating property was slightly lowered, and the room-temperature storage property was good, but the peel strength was lowered as a whole. In addition, since the hydrazide particles are too large, the reactivity is lowered, and the peel strength and heat resistance are insufficient.

In contrast, in the thermosetting adhesive sheet of comparative example 1, since the component (a) is too small and the component (b) is too large in the acrylic copolymer, the component (a) cannot be sufficiently dissolved in the organic solvent, and gelation occurs.

In the thermosetting adhesive sheet of comparative example 2, since the component (a) is too much and the component (b) is too little in the acrylic copolymer, the initial peel strength is not a practically suitable low level although the room temperature storage characteristics are good.

In the thermosetting adhesive sheet of comparative example 3, the amount of component (c) in the acrylic copolymer was too small, and thus the initial peel strength was not at a practically low level although the room temperature storage characteristics were good.

In the thermosetting adhesive sheet of comparative example 4, since the component (c) in the acrylic copolymer was too much, the initial peel strength was not at a practically low level although the room temperature storage property was good.

In the thermosetting adhesive sheet of comparative example 5, the average particle size of the organic acid dihydrazide was too large, and therefore the initial peel strength was at a low level not suitable for practical use.

In the thermosetting adhesive sheets of comparative examples 6 to 8, the acrylic copolymer had a hydroxyl group or a carboxyl group, and thus the room temperature storage characteristics were poor.

Example 11

Using the thermosetting adhesive sheets of examples 1 to 10 and comparative examples 2 to 8, a reinforced flexible printed wiring board was produced as follows.

< moisture absorption reflow soldering Heat resistance test >

The thermosetting adhesive layer of the thermosetting adhesive sheet cut into a rectangular shape (2 cm. times.2 cm) was temporarily stuck to a polyimide film (アピカル 175AH (Tokao) カネカ) having a thickness of 175 μm in a laminator set at 80 ℃, and then the release substrate was removed to expose the thermosetting adhesive layer. The exposed thermosetting adhesive layer was laminated with a 50 μm-thick polyimide film (カプトン 200H, デュポン) having the same size from above, heated and pressurized at 170 ℃ and 2.0MPa for 60 seconds, and then held in an oven at 140 ℃ for 60 minutes. Then, the test piece subjected to heat curing was placed in a moist-heat oven at 40 ℃ and 90% RH for 96 hours.

The test piece immediately after the wet heat treatment was passed through a reflow furnace set to a maximum temperature of 260 ℃ for 30 seconds, and the presence or absence of appearance abnormality such as swelling or peeling of the test piece after passing was visually observed, and the case where no abnormality at all was found in the appearance was evaluated as "a", the case where the test piece was observed to have slight swelling but no practical problem was evaluated as "B", and the case where the test piece was observed to have swelling due to foaming was evaluated as "C". The results obtained are shown in tables 3 and 4.

[ Table 3]

[ Table 4]

As a result of the moisture absorption reflow soldering heat resistance test, no abnormality was observed in the appearance of the reinforced flexible printed wiring board using the thermosetting adhesive sheet of examples 1 to 10, or a slight expansion of the test piece was observed but no problem was found in practical use. In particular, the acrylic copolymer-epoxy resin-hydrazide crosslinked structure of the reinforced flexible printed wiring board using the thermosetting adhesive sheet of examples 1 to 7 was well balanced, and almost no unreacted raw material remained, so that no appearance abnormality was observed at all.

On the other hand, in the case of comparative examples 2 to 8, in addition to comparative example 4, the test piece was observed to expand due to foaming after 25 ℃/6 months. In comparative example 4, the heat resistance of the moisture absorption reflow soldering was good because of the good crosslinked structure, but the initial peel strength was not a practically low level as described above.

Industrial applicability

The thermosetting adhesive composition and the thermosetting adhesive sheet of the present invention can satisfactorily adhere a resin substrate such as a polyimide film to a polyimide film, a stainless steel plate or a glass epoxy resin substrate, and exhibit good room temperature storage characteristics over a period of several months. Further, even if the reflow soldering treatment at 260 ℃ is performed, swelling due to moisture absorption does not occur. Therefore, the polyimide resin is useful as an adhesive in the field of electronic components in which polyimide materials are frequently used.

Claims (7)

1. A process for producing a thermosetting adhesive sheet comprising a thermosetting adhesive layer containing a thermosetting adhesive composition formed on a base film,

a thermosetting adhesive composition containing an acrylic copolymer (A), an epoxy resin (B) and a curing agent (C) for epoxy resin is used as the thermosetting adhesive composition,

the acrylic copolymer (A) is obtained by copolymerizing 65 to 75 mass% of an epoxy group-free (meth) acrylate monomer (a), 20 to 35 mass% of an acrylonitrile monomer (b), and 1 to 10 mass% of an epoxy group-containing (meth) acrylate monomer (c),

the curing agent for epoxy resin is organic acid dihydrazide particles having an average particle diameter of 0.5 to 15 μm,

the manufacturing method comprises the following steps:

a step of dispersing the curing agent (C) for epoxy resin in an organic solvent, and dissolving the acrylic copolymer (A) and the epoxy resin (B) in an organic solvent to prepare a coating material for forming a thermosetting adhesive layer, and

and a step of applying the coating material for forming a thermosetting adhesive layer to a base film and drying the coating material to form a thermosetting adhesive layer.

2. The process according to claim 1, wherein the curing agent for epoxy resin is organic acid dihydrazide particles having an average particle diameter of 1 to 5 μm.

3. The production process according to claim 1 or 2, wherein the organic acid dihydrazide is adipic acid dihydrazide or 7, 11-octadecadienyl-1, 18-dicarbonhydrazide.

4. The production process according to claim 1 or 2, wherein the epoxy resin (B) is contained in an amount of 5 to 30 parts by mass per 100 parts by mass of the acrylic copolymer (A), and the curing agent for epoxy resin is contained in an amount of 4 to 20 parts by mass per 100 parts by mass of the total of the acrylic copolymer (A) and the epoxy resin (B).

5. The production process according to claim 1 or 2, wherein the weight-average molecular weight of the acrylic copolymer (A) is 500000 to 700000.

6. The production process according to claim 1 or 2, wherein the epoxy-free (meth) acrylate monomer (a) and the epoxy-containing (meth) acrylate monomer (c) are both monomers not containing a hydroxyl group and a free carboxyl group.

7. A reinforced flexible printed wiring board in which a reinforcing resin sheet for terminal portion of a flexible printed wiring board is lined, wherein the terminal portion and a thermosetting adhesive layer of the reinforcing resin sheet obtained by removing a base material film of the thermosetting adhesive sheet obtained by the production method according to any one of claims 1 to 6 are adhesively fixed to each other by thermosetting.