JPH02133487A - Adhesive resin composition - Google Patents

Abstract

PURPOSE:To provide an adhesive resin composition which enables bonding at low temperature in a short time with excellent initial bond strength, resistance to soldering heat, etc., by mixing a saturated copolyester resin with a monomer and/or oligomer each having a plurality of unsaturated bonds in the molecule. CONSTITUTION:A saturated copolyester resin (A) (e.g., polyethylene terephthalate adipate) is mixed with a component (B) comprising a monomer and/or oligomer each having a plurality of unsaturated bonds in the molecule, thereby giving an adhesive resin composition. Examples of the component B include ethylene glycol diacrylate, triallyl isocyanurate, and an acrylic-modified bisphenol derivative. The adhesive resin composition thus obtained is suitably used to bond a polyimide film to a copper foil particularly when a flexible printed circuit board is prepared from a polyimide base film.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an adhesive resin composition comprising a saturated copolymerized polyester resin and a crosslinkable monomer and/or oligomer, and more particularly relates to an adhesive resin composition comprising a polyimide base film. The present invention relates to an adhesive resin composition particularly suitable for adhesion between a copper foil and a polyimide film in a flexible printed board, or for adhesion between the board and an overlay film.

[Conventional technology]

In recent years, as electronic devices have become lighter, smaller, and more sophisticated,
Instead of ordinary insulated wires, circuit boards with metal foil wiring formed on the board are used in consumer electronic equipment such as television receivers and audio equipment, electronic equipment such as measuring instruments and computers, automobiles, etc. It has come to be widely used in various wiring parts such as in aircraft.

As a circuit board used for such purposes, a so-called flexible printed circuit board, which has flexibility and is composed of a film made of a polymer material and a copper foil, is often used. A wiring pattern is formed on the substrate by means such as chemical etching on the surface of the copper foil, leaving only the necessary portions.

Currently, this flexible printed circuit board is produced by laminating copper foil and a flexible insulating film such as polyethylene terephthalate film or polyimide film using a film adhesive, or by bonding the copper foil or flexible insulating film onto the copper foil or flexible insulating film. They are manufactured by applying an agent and heat bonding under pressure, or by heat bonding an epoxy resin-impregnated glass cloth (prepreg) to copper foil under pressure.

By the way, in recent years, electronic components such as printed wiring boards,
High performance is required in terms of heat resistance, heat aging resistance, electrical insulation, chemical resistance, tear strength, etc. Especially when mounting these, automatic soldering often requires a process. Regarding heat resistance properties such as solder heat resistance, not only the heat resistance of the flexible insulating film (but also the adhesive layer with the copper foil is required to have a high degree of heat resistance.

Regarding the heat resistance of flexible insulating films, polyethylene terephthalate film is inexpensive but has poor heat resistance, and problems such as softening, blistering, and peeling of the film from the copper foil may occur during the soldering process. In addition, epoxy resin-impregnated glass cloth has switching points such as discoloration during the soldering process, difficulty in manufacturing extremely thin and flexible products, and high cost.

On the other hand, polyimide films have excellent heat resistance, electrical properties, chemical resistance, etc., and are therefore frequently used as base films for flexible printed circuit boards.

However, polyimide films have poor adhesion properties, making it difficult to obtain sufficient peel strength, and peeling of the copper foil during soldering processes and repeated bending is particularly problematic.

Therefore, various adhesives have been developed to improve adhesive properties. To bond the copper foil and polyimide film of a flexible printed circuit board or the flexible printed circuit board and an overlay film, an adhesive that adheres to both the copper foil and the polyimide film is required. Conventionally, as such adhesive, hexafluoropropylene-tetrafluoroethylene copolymer ("Teflon" FEP manufactured by DuPont) has been used.
etc.), epoxy-novolac resins (DOW Chemical Co., Ltd. DEN438, etc.), silicone resins (Dow Corning Co., Ltd. DC282, etc.), nitrile-phenolic resins CB, F, Gutsu: 2 Rich Co., Ltd. Plastilock 605, etc.), polyester-based product Bostic 7151+ B manufactured by USM
oscodur 1, etc.), acrylic resins (B, F,
Gutdrich Hycar 2679X6, Rohm
& Haas Phoplex LC40, UCC
Dear 370 manufactured by Kogyo Corporation, etc.) are known (Industrial Materials, vol. 2+, No., IO, p. 28, 1981).

When the above adhesives are used, the initial adhesive strength between polyimide film and copper foil is 1.0 kg/cm or more, except for systems using silicone resin adhesives, and for example λ Even when immersed in a 290°C solder bath for 10 seconds, no bulging or peeling of the polyimide film or copper foil was observed, and it also has excellent soldering heat resistance.

However, many of the above adhesives require high temperatures and long periods of time to complete adhesion (for example, epoxy
In the case of novolak resin, it is necessary to carry out thermocompression bonding at a high temperature of 180° C. to 200° C. for 30 to 60 minutes in order to complete the curing reaction of the adhesive. For this reason, bonding polyimide film and copper foil is basically a batch process, and when trying to continuously produce flexible printed circuit boards, the bonding process becomes the rate-limiting step.
While there is a limit to productivity improvement, when using a hexafluoropropylene-tetrafluoroethylene copolymer as an adhesive, it is necessary to Sandwich the polymer film and heat at 290°C to 320'C.
Bonding can be done simply by thermocompression, making it suitable for the continuous production of flexible printed circuit boards. However, because the bonding process temperature is higher, there are problems such as partial oxidation of the copper foil. I'm holding it.

Recently, it has been proposed to bond copper foil to a polyimide film via a thermoplastic polyimide film (Larc-TPI manufactured by Mitsui Toatsu Co., Ltd.) (Functional Materials, 1985).
Since the fusing temperature of thermoplastic polyimide is as high as 350° C., problems such as oxidative deterioration of the copper foil and curling due to differences in coefficient of thermal expansion are expected.

Other adhesives for polyimide film and copper foil include epoxy fat-polyamine adhesives and polyol-based adhesives.
Various polyurethane-based adhesives such as isocyanate-based adhesives are being considered, but as above, it requires high temperatures and long periods of time, or even at temperatures around room temperature, to complete the curing reaction of the adhesives. , the adhesion process must be a batch process.

It is also known to shorten the curing time by adding catalysts, etc. However, if curing is completed in a short time, curing distortion remains in the adhesive layer, resulting in problems such as curling of the flexible printed circuit board. Problems may occur.

On the other hand, hot melt adhesives are generally known as adhesives that can bond objects together at relatively low temperatures and in a short time.

Known types of hot melt adhesives include ethylene pomopolymers and copolymers, styrene block copolymers (thermoplastic elastomers), boramid adhesives, nylon adhesives, polyester adhesives, and butyl rubber adhesives.
Viscosifying agents include rosin and its ester derivatives, hydrogenated rosin and its ester derivatives, petroleum-based hydrocarbon resins, additives include paraffin waxes, and antioxidants include hindered phenols and phosphorus. Acid salts are used.

It is conceivable to apply this hot melt adhesive to bonding polyimide film and copper foil. For example, ethylene-
Vinyl acetate copolymer hot melt adhesives and ethylene
Copper foil and polyimide film can be bonded by applying a melted ethyl acrylate hot-melt adhesive to a thickness of about 30 μm on a polyimide film and pressing it against a copper foil at 100°C to 170°C for 1 minute. In this case, it is possible to easily form a material having an initial adhesive strength of 1.0 kg/cm or more.

However, the polyimide film copper foil laminate formed using the above hot melt adhesive has a problem in that the polyimide film and the copper foil peel off when placed in a solder bath at 280° C. for 5 seconds, for example.

As explained above, many adhesives have been proposed and used for adhering copper foil and polyimide film with the aim of improving adhesive strength and solder heat resistance. However,
Many thermosetting adhesives require high temperatures and long periods of time to cure, so the bonding process is a batch process, resulting in poor productivity.
Thermoplastic adhesives also require pressure bonding at high temperatures and have problems such as oxidation of the copper foil and curling of the substrate.

On the other hand, hot melt adhesives can be bonded at a relatively low temperature and in a short time, and have good initial adhesive strength, but have extremely poor soldering heat resistance.

As described above, there has been no known adhesive that can be bonded in a short time, has a strong initial adhesive strength (and also has good soldering heat resistance).

[Problems to be Solved by the Invention] An object of the present invention is to provide an adhesive resin composition that can be bonded at a relatively low temperature and in a short time, has a large initial adhesive strength, and has excellent soldering heat resistance. It's about doing.

A further object of the present invention is to provide an adhesive resin composition suitable for adhesion between a copper foil and a polyimide film of a flexible printed board having a polyimide base film, or between the board and an overlay film.

As a result of intensive research to solve the problems of the above-mentioned conventional technology, the present inventors have discovered a resin in which a monomer and/or oligomer having multiple unsaturated bonds in the molecule is added to a saturated copolymerized polyester resin. It has been found that the composition can be used as an adhesive for polyimide film and copper foil to bond at relatively low temperatures and in a short time, has excellent initial adhesive strength, and has excellent solder heat resistance. The present invention has been completed based on these findings.

[Means for Solving the Problems] That is, the gist of the present invention is to provide an adhesive resin composition obtained by adding a monomer and/or oligomer having a plurality of unsaturated bonds in the molecule to a saturated copolymerized polyester resin. It is in.

Hereinafter, the configuration of the present invention will be explained in detail.

(Saturated copolymerized polyester resin) The saturated copolymerized polyester resin used in the present invention is synthesized by a polycondensation reaction of a polycarboxylic acid and a polyhydric alcohol, and specifically includes terephthalic acid, isophthalic acid, The monomer components are polycarboxylic acids such as adipic acid, azelaic acid, and sebacic acid, and polyhydric alcohols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and polyethylene glycol. It is a copolymer obtained by polycondensing a combination of

Typical of these saturated copolymerized polyester resins are those in which some of the components of saturated homopolyesters such as polyethylene terephthalate and polybutylene terephthalate are replaced with other components and randomly copolymerized, such as polyethylene terephthalate.・Sevakate,
Examples include polyethylene terephthalate/adipate, polyethylene terephthalate/isophthalate, and polybutylene terephthalate/isophthalate.

In the present invention, commercially available saturated copolyester resins can be used. Furthermore, two or more types of resins may be used in combination.

(Monomers and oligomers having multiple unsaturated bonds in the molecule) Monomers having multiple unsaturated bonds in the molecule used in the present invention include, for example, ethylene glycol diacrylate, 1,4-butanediol dimethacrylate, , trimethylolpropane triacrylate, polyethylene glycol dimethacrylate, cyanuric acid triacrylate, acrylic ester or methacrylic ester monomers such as triacrylic formal, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diethylene glycol diallyl ether Examples include allyl compounds such as.

Further, examples of oligomers having multiple unsaturated bonds in the molecule used in the present invention include acrylic-modified bisphenol derivatives, acrylic-modified novolac resin derivatives,
Examples include acrylic modified ester oligomers, arylidene pentaerythritol derivatives, diarylidene pentaerythritol derivatives, and acrylic modified diarylidene pentaerythritol derivatives.

These monomers and oligomers can be used alone or in combination.

(Blending ratio) The blending ratio of the saturated copolymerized polyester resin and the monomer and/or oligomer having multiple unsaturated bonds in the molecule is not particularly limited, but from the viewpoint of initial adhesive strength and soldering heat resistance, the saturated copolymerized polyester resin Polyester resin 99-5
The blending ratio is preferably 1 to 50 parts by weight of the monomer and/or oligomer to 0 parts by weight, and more preferably 5 to 30 parts by weight of the monomer and/or oligomer to 95 to 7 parts by weight of the saturated copolymerized polyester resin. This is the blending ratio of

In addition, the adhesive resin composition of the present invention may include, if necessary,
Additives such as plasticizers and antioxidants can be added as appropriate.

Furthermore, as described later, an organic peroxide such as dicumyl peroxide or a photopolymerization initiator such as benzophenone can be added.

(Method of Use) In order to use the adhesive resin composition of the present invention as an adhesive for flexible printed circuit boards using polyimide as a base film, the resin composition is heated and melted and applied onto a polyimide film, or A resin composition layer is formed by applying and drying a solution of a resin composition in an organic solvent, and then a copper foil is thermally pressed onto the resin composition layer by a method such as a hot press. The conditions for thermocompression bonding depend on the softening point or melting point of the saturated copolymer polyester used, but are preferably 100 to 210'C1.
180°C1, more preferably at a temperature of 100 to 160°C, preferably for 1 to 20 minutes, even more preferably for 5 to 15 minutes.
It can be crimped in minutes.

The adhesive resin composition of the present invention can complete adhesion only by the above-mentioned thermocompression bonding method, and in this case, radical polymerization of organic peroxides, etc., which generate active species such as free radicals by heating, can be completed. It is desirable to add an effective amount of the agent to the adhesive resin composition in advance.

Further, by irradiating ionizing radiation from the surface of the polyimide film after thermocompression bonding using the adhesive resin composition of the present invention, a polyimide film copper foil laminate with even better initial adhesive strength and soldering heat resistance can be obtained. Can be done.

Ionizing radiation includes α rays, β rays (electron beams), γ rays, and
Rays, ultraviolet rays, etc. can be used, but from the standpoint of industrial use, it is desirable to use β rays (electron beams) and ultraviolet rays. When ultraviolet rays are used, it is preferable to add an effective amount of a photopolymerization initiation catalyst such as benzophenone, benzophenone derivatives, acetophenone, and acetophenone derivatives that generate free radicals upon irradiation with ultraviolet rays.

Furthermore, the adhesive resin composition of the present invention can be applied not only to polyimide film copper foil laminates but also to fields where bonding by thermocompression bonding or the like is possible.

[Function] When the composition of the saturated copolymerized polyester of the present invention and a monomer and/or oligomer having a plurality of unsaturated bonds in the molecule is used as an adhesive between a polyimide film and a copper foil, the initial adhesion strength as well as the solder A polyimide film copper foil laminate (flexible printed circuit board) with excellent heat resistance is obtained. Since the thermocompression bonding conditions are relatively low temperature and short time, there are no problems such as oxidation deterioration of the copper foil or curling of the substrate.

When only saturated copolymerized polyester resin is used as an adhesive between polyimide film and copper foil, although it has excellent initial adhesion strength, it does not have good soldering heat resistance. If only a monomer and/or oligomer having a plurality of unsaturated bonds is used as an adhesive between a polyimide film and a bamboo tube, a polyimide film copper foil laminate with deteriorated initial adhesiveness cannot be obtained.

In this way, a unique effect is produced by combining both components.

According to the present invention, it is possible to significantly shorten the time required for the bonding process, which has been a problem with conventional adhesives. For example, when completing the bonding by electron beam irradiation,
Even including the thermocompression bonding process, it is 1/2 to 1/10 of the conventional price.
The bonding process can be completed in a short time. Moreover,
Since the temperature of thermocompression bonding can be lowered, for example, it is possible to carry out the roll lamination process (thermocompression bonding process) and the electron beam irradiation process in a continuous line, improving productivity and workability. can.

[Examples] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Examples 1 to 6] As the polyimide film, Kapton 100H (trade name) manufactured by DuPont Azuma ((1)) with a thickness of 25 μm was used, and as the copper foil, an electrolytic copper foil with a thickness of 35 μm was used.

After mixing the saturated copolymerized polyester shown in Table 1 with a monomer or oligomer having multiple unsaturated bonds in the molecule using a roll mixer, the resulting resin composition is placed on the polyimide film. Using a hot applicator, apply to a thickness of 35 μm and allow to cool.
An adhesive layer was formed. A resin composition to which an organic peroxide was added was similarly prepared to form an adhesive layer.

The copper foil was brought into close contact with this adhesive layer, and was pressed with a hot press at 150°C. Furthermore, for those in which the adhesion was completed by irradiation with electricity or radiation, an electron beam with an acceleration voltage of 400 kV was irradiated from the surface of the polyimide film onto the laminate that had been pressure-bonded using a heat press. The conditions are shown in Table 1.

Physical properties of the laminate after bonding were evaluated by peeling test (reinforcing plate type) and observation of the sample after being immersed in a solder bath (solder bath temperature: 28° C., immersion time: 30 seconds). The results are summarized in Table 1.

[Comparative Examples 1 to 7] For comparison, saturated copolymerized polyester resins shown in Table 2 or monomers or oligomers having multiple unsaturated bonds in the molecule were used alone, and the conditions shown in the same table were used. A polyimide film copper foil laminate was obtained.

These laminates were also subjected to a peel test and a solder bath immersion test in the same manner as in the examples. The results are summarized in Table 2.

The saturated copolymerized polyesters used in Examples and Comparative Examples are as follows.

A: Saturated copolymer polyester resin with a softening point of 115°C, a glass transition point of 9°C, and a melt viscosity of 2800 voids (200°C) (manufactured by Higashishioki Co., Ltd., trade name: Chemit), H2: Softening point of 145°C, Saturated copolymerized polyester resin with a glass transition point of 47°C and an intrinsic viscosity of 0.5 dl/g (
Toyobo (manufactured by... company, product name Byron) A3: Softening point 113°C, glass transition point 23°C, @
Saturated copolymerized polyester resin with a melt viscosity of 2300 voices (2oo'c), a softening point of 145°C, and a glass transition point of 25°C.
1 A mixture of 75/254i ratio of saturated copolymerized polyester resin with a melt viscosity of 1600 voids (200°C) (Toshi ■
A4: Saturated copolymer polyester resin (manufactured by Toyobo (1), product name Vylon) with a softening point of 115°C, a glass transition point of 24°C, and an intrinsic viscosity of 0.3 dl/g (manufactured by Toyobo Co., Ltd. (1), product name Vylon) (blank below) As is clear from Table 1, the polyimide film copper foil laminate using the adhesive resin composition of the present invention has good initial adhesive strength and excellent soldering heat resistance. On the other hand, when a saturated copolymer (1") polyester resin was used alone, as shown in Table 2, the initial adhesion was good, but the soldering heat resistance was poor.
Even if monomers or oligomers having multiple unsaturated bonds were used alone, they could not be bonded.

[Effect of the invention] The adhesive resin composition of the present invention can be interposed between objects to be adhered,
Bonding can be done at relatively low temperatures and in a short time using thermocompression bonding, etc., and the initial adhesive strength is strong (and it has excellent solder heat resistance).

This adhesive resin composition is particularly suitable for bonding the copper foil and polyimide film of a flexible printed circuit board with a polyimide base film, or the substrate and an overlay film, and significantly reduces the time required for the bonding process. Moreover, since the temperature of thermocompression bonding can be lowered, it is possible to improve productivity and workability. Further, problems such as oxidative deterioration of the copper foil and curling of the substrate can be solved.

Claims (1)

[Claims] (1) An adhesive resin composition obtained by adding a monomer and/or oligomer having a plurality of unsaturated bonds in the molecule to a saturated copolymerized polyester resin.