JPH0841428A - Polyimide precursor adhesive film, bonded laminate using the same and production of the laminate - Google Patents

Abstract

PURPOSE:To obtain a polyimide precursor adhesive film free from aprotic polar organic solvent, to obtain a laminate by bonding a laminating base material through a highly heat-resistant polylmide layer derived from cyclizing the polyimide precursor, and to provide a production method for the laminate. CONSTITUTION:The first aimed film for bonding a polyimide precursor, substantially containing no aprotic polar organic solvent, is composed of a polyimide precursor capable of forming a poly(4,4'-oxydiphenylene pyromellitimide) after cyclization and 1-30wt.% of a solvent not strongly solvating with the polyimide precursor. The second aimed laminate is obtained by bonding a base material through a polyimide adhesive layer obtained by cyclizing the above polyimide precursor. The third aimed production method is such that this laminate is obtained by hot pressing while cyclizing the precursor to effect bonding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for adhering a polyimide precursor, a laminate bonded with a polyimide layer obtained by ring-closing the polyimide precursor constituting the film, and a method for producing the same. .

[0002]

2. Description of the Related Art Polyimide has excellent heat resistance, mechanical properties, electrical properties, weather resistance and the like, and is known to be useful as a raw material for films and molded products. For example,
Non-thermoplastic poly (4,4 ′) prepared from 4,4′-diaminodiphenyl ether and pyromellitic dianhydride
From (oxydiphenylenepyromellitimide), films and molded products having excellent heat resistance can be obtained, and these are widely used for electrical insulation applications and the like.

Further, in the space and aviation fields, as a structural material of an airframe, a laminated plate in which a metal plate, a fiber reinforced plastic, a honeycomb core and the like are laminated is widely used. Furthermore, in the electronics field, a laminated board in which a substrate made of fiber reinforced plastic, film, etc. and a metal foil are bonded together is used as a circuit board, and with the advancement of technology, laminated boards with even better heat resistance than at present. However, it is said that the physical properties of the laminated plate largely depend on the physical properties of the adhesive, and it is particularly desired to improve the heat resistance of the adhesive.Adhesives made of polyimide have already been put into practical use. ing. However, all of these adhesives have solvent-soluble and / or thermoplastic polyimide as a main component, and these polyimides are inferior in heat resistance to non-thermoplastic polyimide.

Non-thermoplastic polyimide is insoluble and infusible,
In order to use it as an adhesive, it is necessary to perform a process in which the polyimide precursor is bonded and then closed. Further, conventionally, a polyimide precursor which becomes a non-thermoplastic polyimide upon ring closure has been produced by polymerization in an aprotic polar organic solvent. However, since the aprotic polar organic solvent is strongly solvated with the polyimide precursor, when used as an adhesive, a large amount of solvent remains even after drying, and a large amount of residual solvent gas is generated during thermocompression bonding. Further, there is also a safety problem that the solvent remains in the final product and the residual solvent decomposes at high temperature to generate carbon monoxide and the like. Due to these problems, non-thermoplastic polyimide adhesives have not been put to practical use.

[0005]

SUMMARY OF THE INVENTION In view of such a situation, an object of the present invention is to provide a polyimide precursor bonding film capable of solving the problems caused by aprotic polar organic solvent, and to construct the film. Another object of the present invention is to provide a laminate obtained by adhering a base material for lamination with a polyimide layer having excellent heat resistance obtained by ring-closing a polyimide precursor described above, and a method for producing the same.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when a ring is closed, poly (4,4'-oxydiphenylenepyromellitimide) is obtained.
A polyimide precursor for forming a film, a polyimide precursor adhesion film containing a specific amount of a solvent that is not strongly solvated with this polyimide precursor, and obtained by ring closure of the polyimide precursor constituting this using this. It was found that a laminate obtained by adhering a base material for lamination with such a polyimide layer solves the above problems, and has reached the present invention.

That is, the gist of the present invention is, firstly, that a polyimide precursor which forms poly (4,4'-oxydiphenylenepyromellitimide) upon ring closure, and the polyimide precursor and solvent are strongly solvated. It is composed of a non-solvent, the content of this solvent is 1 to 30 wt%, a polyimide precursor adhesion film, characterized in that it contains substantially no aprotic polar organic solvent, second,
The base material for lamination is a laminate adhered with a polyimide layer obtained by ring-closing the polyimide precursor constituting the polyimide precursor adhesion film, and thirdly, between the base materials for lamination. The polyimide precursor bonding film is sandwiched, and hot pressing is performed at 150 to 300 ° C. to bond the lamination base material while ring-closing the polyimide precursor forming the polyimide precursor film. It is a method of manufacturing a laminate.

Hereinafter, the present invention will be described in detail. In the present invention, the polyimide precursor that forms poly (4,4′-oxydiphenylenepyromellitimide) when the ring is closed is
It can be obtained by polymerizing pyromellitic dianhydride and diaminodiphenyl ether. The solvent in which the polyimide precursor and the solvent are not strongly solvated refers to a solvent having a dipole moment of 3.0 debye or less, which is a unique property of the solvent, and has a solvation index of 0.35 between the solvent and the polyimide precursor. It is preferably less than 0.3, particularly preferably 0.3 or less.

The solvation means an essential interaction between the polyimide precursor which is a solute and the solvent in the solution of the polyimide precursor, and the strong solvation means that the solute and the solvent are strongly associated with each other. Means that The degree of solvation can be determined by, for example, the solvation index measured by the following method. That is, 5000 mg of a 6% by weight solution of a polyimide precursor is added to an inner diameter of 86 mm and a height of 1
Pour evenly onto a standard 8 mm glass dish,
If the weight of the polyimide precursor on the petri dish after the solvent is distilled off under the reduced pressure of 10 mmHg at 40 ° C. for 40 hours after being air-dried at room temperature is Amg,
The solvation index can be expressed by the following formula. Solvation index = (A-300) / 300

The content of this solvent in the polyimide precursor bonding film is 1 to 30% by weight. If the solvent content in the film is less than 1% by weight, the adhesive strength is weak and the film becomes brittle, which is a problem in work. If the solvent content exceeds 30% by weight, the amount of gas of the solvent and condensed water generated during thermocompression bonding increases. Specific examples of these solvents will be described later.

The thickness of the film is preferably 5 to 100 μm, more preferably 10 to 50 μm. If the thickness is less than 5 μm, it is difficult to obtain sufficient adhesive strength, and if the thickness exceeds 100 μm, the amount of gas generated due to the solvent and condensed water during thermocompression bonding increases, which is not preferable. In the present invention, the aprotic polar organic solvent means N, N-dimethylformamide, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N-methylcaprolactam, N-acetyl-2-pyrrolidone, dimethyl sulfoxide. , Hexamethylphosphoramide, and the like, and a solvent having a dipole moment, which is a property peculiar to the solvent, having a polarity larger than 3.0 Debye.

Conventionally, a solution of a polyimide precursor has been produced by polymerizing diamine and tetracarboxylic dianhydride in the aprotic polar organic solvent as described above. However, since these solvents are strongly solvated with the polyimide precursor, when formed into a film from this solution, a large amount of aprotic polar organic solvent remains in the polyimide precursor film, and further in the polyimide film. It was that.

The film for bonding a polyimide precursor of the present invention is obtained from a polyimide precursor solution comprising a polyimide precursor and a solvent in which the precursor and the solvent are not strongly solvated or a single solvent. Since the polar organic solvent polyimide precursor is not substantially contained, it is possible to avoid the adverse effect caused by using the aprotic polar organic solvent.

In the present invention, the polyimide precursor solution contains, for example, pyromellitic dianhydride and diaminodiphenyl ether in a solvent consisting of a mixed solvent of a solvent in which the polyimide precursor and the solvent are not strongly solvated or a single solvent.
It is preferably obtained by a polymerization reaction at 20 to 50 ° C. Further, the polyimide precursor solution may be manufactured by dissolving a polyimide precursor manufactured by another method in these solvents. The concentration of the polyimide precursor in the polyimide precursor solution for forming the polyimide precursor film is 1
-50% by weight is preferable, and 5-25% by weight is more preferable.

As the mixed solvent of the polyimide precursor and the solvent which is not strongly solvated, a combination of two or more solvents selected from water-soluble ether compounds, water-soluble alcohol compounds, water-soluble ketone compounds and water is used. The solvent used is a water-soluble compound having an ether group and an alcoholic hydroxyl group in the same molecule. As a combination of mixed solvents, a combination of a water-soluble ether compound and water, a water-soluble ether compound and a water-soluble alcohol compound, and a combination of a water-soluble ketone compound and water are particularly preferable.

The mixing ratio of the solvent in the mixed solvent is, by weight, 9 in the case of water-soluble ether compound and water.
6: 4 to 79:21, 90:10 to 56:44 for water-soluble ether compounds and water-soluble alcohol compounds,
In the case of water-soluble ketone compound and water, 90:10 to 65:
35 is preferred.

Examples of the water-soluble ether compound include tetrahydrofuran (THF), dioxane, trioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and the like, with THF being particularly preferable. Examples of water-soluble alcohol compounds include methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-. Butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-
2,4-pentanediol, glycerin, 2-ethyl-
2- (hydroxymethyl) -1,3-propanediol, 1,2,6-hexatriol and the like can be mentioned, with particular preference given to methanol, ethanol and ethylene glycol. Examples of water-soluble ketone compounds include acetone and methyl ethyl ketone, with acetone being particularly preferred.

Examples of water-soluble compounds having an ether group and an alcoholic hydroxyl group in the same molecule include 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethoxyethanol, 2-isopropoxyethanol, 2-Butoxyethanol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monoethyl ether, tetraethylene glycol, 1-methoxy-2-propanol, 1- Ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoe Ether, tripropylene glycol monomethyl ether, polyethylene glycol, polypropylene glycol and the like, particularly preferably 2-methoxyethanol, diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol. Further, a water-soluble compound having an ether group and an alcoholic hydroxyl group in the same molecule and a poor solvent may be used in combination.

The polyimide precursor film can be formed from the above polyimide precursor solution by a conventional method. For example, in the casting method, the polyimide precursor solution is cast on a substrate and dried. Then, the solvent content is adjusted to 1 to 30% by weight, and then the polyimide precursor film is peeled off from the substrate. Thus, in the present invention, since the polyimide precursor and the solvent is a solvent that is not strongly solvated in the film forming solution, a polyimide precursor film that does not substantially contain an aprotic polar organic solvent as in the conventional case. Obtained, the solvent can be easily removed and the solvent content can be easily adjusted.

In the laminate of the present invention, the base material for lamination is adhered by a polyimide layer obtained by ring-closing the polyimide precursor constituting the film for adhering a polyimide precursor obtained as described above. It is a laminate and is composed of two or more layers excluding a polyimide layer for adhesion.

The types of substrates for bonding include metal plates, metal foils, films, plastics, woven fabrics, non-woven fabrics,
Examples include paper, and at least one of the substrates is a woven fabric, a non-woven fabric, a porous body such as paper, at the time of thermocompression bonding,
It is preferable because the gas resulting from the residual solvent and condensed water is easily removed. Furthermore, it is more preferable that at least one of the base materials is paper containing 10% by weight or more of the polyimide precursor fibrids from the viewpoint of adhesion strength. Similarly, for a multi-layered laminate having three or more base materials, it is preferable that either one of the two adjacent base materials is a porous body and further paper containing 10% by weight or more of the polyimide precursor fibrids. .

10% by weight of polyimide precursor fibrids
The polyimide precursor fibrids in the paper containing the above preferably comprises the same polyimide precursor as the adhesive film, and refers to fibrous or film-like particles, and two of these three dimensions are about micron size. Is. Such a polyimide precursor fibrid can be produced by injecting a polyimide precursor solution similar to the above-mentioned film forming solution into a coagulating bath under shearing action to cause precipitation. A polyimide precursor paper can be obtained by papermaking and drying these from a dispersion liquid obtained by dispersing 10% by weight or more of the polyimide precursor fibrids obtained as described above and short fibers in an aqueous medium. .

As the short fiber, glass fiber, carbon fiber,
Examples of the fibers include organic fibers and ceramic fibers, and short fibers having good dispersibility in an aqueous medium can be used. Of these, para-aramid short fibers produced from paraphenylenediamine and terephthalic acid chloride, meta-aramid short fibers produced from metaphenylenediamine and isophthalic acid chloride, or copolymerized aramid short fibers thereof are preferable. The above-mentioned polyimide precursor fibrid was used as 10
When a paper containing more than 10% by weight is used as a substrate, the polyimide precursor constituting the polyimide precursor fibrides is closed by heating similarly to the adhesive film, and a polyimide paper containing more than 10% by weight of polyimide fibrids. It becomes a laminated material using as a base material.

The laminate of the present invention can be produced by sandwiching an adhesive film made of a polyimide precursor between two substrates and performing hot pressing. The temperature of the heating press is the temperature at which the ring-closing reaction of the polyimide precursor proceeds.
That is, it is performed at 150 to 300 ° C. At this time, it is more preferable to raise the temperature stepwise in order to prevent generation of voids, foaming, and cracking due to rapid progress of the ring-closing reaction. Pressing pressure is 1-1000 kg / cm ² , pressing time is 1-
It may be 60 minutes, but condensed water is generated during the ring-closing reaction of the polyimide precursor and a gas is generated by the residual solvent in the adhesive film. . In addition, 300 after pressing
Heat treatment at ˜500 ° C. for 1 to 60 minutes to complete the ring closure reaction.

When a multi-layer laminate having three or more substrates is manufactured, the substrates and the adhesive film may be alternately laminated and hot-pressed at once, or several times for each layer. The heating press may be performed separately. Thus, the polyimide precursor adhesive film of the present invention, the substrate can be bonded by sandwiching between the substrates and performing hot pressing,
The polyimide adhesive layer obtained by ring closure is composed of a specific heat-resistant polyimide layer. Further, since the solvent contained during the hot pressing is removed from the adhesive layer, a strong adhesive layer is formed.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 (1) Adhesive film 4.00 g of diaminodiphenyl ether was added to 59.
Dissolve in a mixed solvent of 6 g and 15.9 g of methanol, and 3.
It was kept at 8 ° C. Pyromellitic dianhydride was added to this solution.
40 g was added all at once and stirring was continued for 1 hour to obtain a polyimide precursor solution having a polyimide precursor [η] of 1.0. At this time, the solvation index of the polyimide precursor and the mixed solvent was 0.30. 300 parts of this solution on a glass substrate using an automatic film applicator.
After uniformly casting to a thickness of μm and drying at room temperature for 2 hours,
The adhesive film was peeled off from the glass substrate. The thickness of the film was 28 μm, and the solvent content was 15% by weight.

(2) Polyimide Precursor Paper The above-mentioned polyimide precursor solution was diluted with THF / methanol (weight ratio 4/1) so that the solid concentration was 7.5%. The rotational viscosity of the diluted solution was 74 cps.
24 ml / min of the above-mentioned polyimide precursor solution and 960 ml / min of water were placed in a continuous homomixer (capacity 500 ml, turbine speed 8500 rpm) equipped with a coagulant / stock solution supply port and a fibrid slurry discharge port. Was simultaneously supplied, and the fibrid slurry was continuously taken out from the discharge port. The generated polyimide precursor fibrid was filtered off, 1 liter of water was added, and the mixture was stirred and filtered three times. 3 g of polyimide precursor fibrids and 3 g of para-aramid short fibers (1.5 d, 6 mm) are dispersed in 3 liters of water, paper is made into a size of 15 × 15 cm, and 10 kg / cm
^It was squeezed and dehydrated under a pressure of ² and dried at 60 ° C. for 1 hour to obtain a polyimide precursor paper.

(3) Laminated plate An adhesive film was sandwiched between an aluminum plate having a thickness of 0.1 mm and a polyimide precursor paper, and the temperature was 5 kg at 180 ° C. and 10 kg / cm ² .
Min, 50kg / cm ² for 10 minutes, and 300 ℃ for 50 minutes
Hot pressing was performed at 5 kg / cm ² for 5 minutes and 100 kg / cm ² for 10 minutes, and finally heat treatment was performed at 300 ° C. for 1 hour to terminate the ring-closing reaction. The adhesion between the base materials of the obtained laminate was strong, and the paper broke the base material when trying to peel it off.

Example 2 4.00 g of diaminodiphenyl ether was added to 50.0 g of 2-methoxyethanol to form a uniform slurry.
It was kept at 0 ° C. Here, pyromellitic dianhydride 4.45
When g was added all at once and stirring was continued for 4 hours, a polyimide precursor solution having a polyimide precursor [η] of 0.8 was obtained. At this time, the solvation index of the polyimide precursor and 2-methoxyethanol was 0.30. This solution was uniformly cast on a glass substrate to a thickness of 200 μm using an automatic film applicator,
After drying at room temperature for 1 hour and 60 ° C. for 2 hours, the adhesive film was peeled off from the glass substrate. The thickness of the film was 26 μm, and the solvent content was 12% by weight. Example 1
An adhesive film was sandwiched between the same base materials as above, and hot pressing and heat treatment were performed under the same conditions. The adhesion between the base materials of the obtained laminate was strong, and the paper broke the base material when trying to peel it off.

Comparative Example 1 A solution of a polyimide precursor containing NMP as a main component as a solvent (Pyre ML manufactured by Du Pont Co., polyimide precursor and NMP).
Of which the solvation index is 0.66) is evenly cast on a glass substrate to a thickness of 200 μm using an automatic film applicator, dried at 80 ° C. for 3 hours, and then peeled off from the glass substrate. And dried for 2 hours to give an adhesive film. The thickness of the film was 32 μm, and the solvent content was 31% by weight. The adhesive film was sandwiched between the same base materials as in Example 1, and hot pressing and heat treatment were performed under the same conditions. Generation of vapor due to a large amount of residual solvent was observed during hot pressing. When trying to peel between the base materials of the obtained laminated plate, it was possible to easily peel between the adhesive film and the aluminum plate.

[0031]

As described above, when the polyimide precursor film for adhesion of the present invention is sandwiched between the substrates and hot-pressed, it forms a strong polyimide adhesive layer having heat resistance. can do. Further, since the polyimide precursor film for adhesion of the present invention does not contain an aprotic polar organic solvent, various problems caused by the residual solvent can be solved. Therefore, a laminate obtained by adhering a base material using this polyimide precursor film for adhesion has heat resistance and excellent adhesive force between layers. Further, such a laminate can be easily produced by the method for producing a laminate of the present invention.

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Claims (3)

[Claims] 1. A method comprising: a polyimide precursor which forms poly (4,4′-oxydiphenylenepyromellitimide) upon ring closure; and a solvent which does not strongly solvate the polyimide precursor and the solvent. A film for bonding a polyimide precursor, which has a ratio of 1 to 30% by weight and contains substantially no aprotic polar organic solvent. 2. A laminate in which a substrate for lamination is adhered by a polyimide layer obtained by ring-closing the polyimide precursor constituting the film for adhering a polyimide precursor according to claim 1. 3. A polyimide precursor bonding film according to claim 1 is sandwiched between lamination base materials, and the temperature is 150 to 300 ° C.
The method for producing a laminate according to claim 2, wherein the base material for lamination is adhered while the polyimide precursor constituting the polyimide precursor film is ring-closed by hot pressing.