JPH10120987A - Production of film-like adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress foaming in the varnish obtained by dissolving a composition containing a high-molecular weight epoxy polymer having film formability and an epoxy resin having more than two functions as essential components in a solvent to a film-like state and drying. SOLUTION: A composition containing a high-molecular weight epoxy polymer having film formability and an epoxy resin having more than two functions as essential components is dissolved in a solvent and the resultant varnish having 6-12Pa.s viscosity at 25 deg.C is made to a film-like state, then dried to B-stage. The viscosity of the varnish at 25 deg.C is made to 6-12Pa.s by using a film-formable high-molecular weight epoxy polymer having 350,000-550,000 weight-average molecular weight (reduced to a standard polystyrene by gel- permeation chromatography) as the film-formable high-molecular weight epoxy polymer, or heating the varnish.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a film adhesive.

[0002]

2. Description of the Related Art In response to a reduction in the thickness of a multilayer printed wiring board, a film-like thermosetting adhesive is used in place of a prepreg between the components of the multilayer printed wiring board, for example, copper foil for an outer layer. It has come to be integrated with the inner circuit board by bonding. As a film-like thermosetting adhesive, a film-like composition comprising a high-molecular-weight epoxy polymer having film-forming ability and a bifunctional or higher epoxy resin as essential components is known.

[0003] As a method of forming a composition containing a high molecular weight epoxy polymer having a film forming ability and a bifunctional or higher epoxy resin as essential components, a high molecular weight epoxy polymer having a film forming ability is used. A method is known in which a varnish obtained by dissolving a composition containing a functional or higher epoxy resin as an essential component in a solvent is applied to a base film or a smooth glass plate surface to form a film, and the solvent is removed by heating. Have been.

[0004]

However, in order to increase the efficiency of the solvent removing step, if the heating temperature is increased in a short time,
Bubbling sometimes occurred in the film due to evaporation of the solvent. The present invention relates to a varnish obtained by dissolving a composition containing a high molecular weight epoxy polymer having a film forming ability and a bifunctional or higher epoxy resin as an essential component in a solvent, forming a varnish into a film, and drying the varnish to the B stage. The purpose is to suppress foaming.

[0005]

As a result of various studies on means for suppressing foaming when removing the solvent of the varnish, the present inventor has found that the viscosity at 25 ° C. conventionally used is 2.5 to 3. By further increasing the varnish of 5 Pa · s, the foaming can be effectively suppressed, for example,
It has been found that foaming can be prevented even when the temperature is raised from room temperature to about 130 ° C. in about 2 minutes, and the present invention has been accomplished.

According to the present invention, a composition comprising, as essential components, a high molecular weight epoxy polymer having a film forming ability (hereinafter referred to as a high molecular weight epoxy polymer) and a bifunctional or higher epoxy resin is dissolved in a solvent; This is a method for producing a film-like adhesive, wherein a varnish having a viscosity at 6 ° C (hereinafter simply referred to as viscosity) of 6 to 12 Pa · s is formed into a film and further dried to a B stage. Here, having the ability to form a film means that, for example, when a solvent dissolved in a solvent is cast on a substrate and the solvent is removed, a film can be formed, and the formed film is transported, cut, laminated, and the like. It means that troubles such as cracks and dropouts are unlikely to occur during the step.

When a varnish is formed into a film and heated to remove the solvent, foaming that occurs when the solvent is vaporized due to its high viscosity is suppressed. The varnish has a viscosity of 6 Pa
When the varnish is less than s, the effect of suppressing foaming when the solvent is removed after the varnish is applied in the form of a film is small.
When the viscosity exceeds Pa · s, the leveling property when the varnish is formed into a film is insufficient, so that the thickness unevenness occurs, which is not preferable. From such a viewpoint, the viscosity of the varnish is 7
More preferably, it is 10 Pa · s to 10 Pa · s.

[0008] The viscosity of the varnish is determined by the molecular weight of the solute, the viscosity of the solvent, and the concentration of the solute. However, when a solvent having a high viscosity is used, workability such as dissolution is deteriorated. Further, there is a limitation in increasing the concentration of the solute due to limitations in solubility and the like.

Therefore, in the present invention, one of the preferable methods for adjusting the viscosity of the varnish to 6 to 12 Pa · s is to use a high molecular weight epoxy polymer as a weight average molecular weight (hereinafter simply referred to as molecular weight) in terms of standard polystyrene by gel permeation chromatography. 350,000-550,00
0 high molecular weight epoxy polymer. In this case, if the molecular weight is less than 350,000, a varnish having a viscosity within a predetermined range cannot be obtained.
If it exceeds 0, it becomes easy to gel. From such a viewpoint, the molecular weight of the high molecular weight epoxy polymer is from 400,000 to
More preferably, it is 500,000.

Further, the varnish may be heated and a crosslinking reaction may be advanced to such an extent that the subsequent coating step is not hindered, so that the varnish has a viscosity of 6 to 12 Pa · s.

As the high molecular weight epoxy polymer used in the present invention, a bifunctional epoxy resin and a bifunctional phenol are used in a ratio of 0.9 to 1.1 equivalents of phenolic hydroxyl group to 1 equivalent of epoxy group. Polymerization is preferable because the resulting high molecular weight epoxy polymer becomes substantially linear and a film having excellent properties such as strength can be obtained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The high-molecular-weight epoxy polymer may be any one obtained by polymerizing a low-molecular-weight bifunctional epoxy resin having a molecular weight of about 50,000 or more in a substantially linear manner. Absent. Examples of such a compound include a bifunctional epoxy resin and a bifunctional phenol in a ratio of 0.9 to 1.1 equivalents of a phenolic hydroxyl group to one equivalent of an epoxy group in an amide solvent in an alkali metal hydroxide. And a linear epoxy polymer obtained by polymerizing in the presence of a catalyst selected from alkali metal alcoholates and alkali metal phenolates at a solid content concentration of 50% by weight or less during the polymerization reaction. Japanese Patent Publication No. Hei 7-59619). As the bifunctional epoxy resin used here,
Bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, alicyclic epoxy resin, aliphatic chain type epoxy resin, glycidyl ether compound of bifunctional phenol, glycidyl ether compound of bifunctional alcohol, etc. Halides of
These hydrogenated products are exemplified. Further, as bifunctional phenols, hydroquinone, resorcinol,
Examples include catechol, bisphenol A, bisphenol F, halides thereof, and alkyl-substituted products thereof. The amide solvent used for the reaction may be any solvent that can dissolve the reaction components and has little volatilization at the reaction temperature. Formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N
-Methylacetamide, N, N-dimethylacetamide, N, N, N ', N'-tetramethylurea, 2-pyrrolidone, N-methylpyrrolidone, carbamic acid esters and the like. A ketone-based solvent can be used instead of the amide-based solvent. The polymerization reaction conditions are 60 to 150
C. is preferred. If the temperature is lower than 60 ° C., the reaction is slow, and if it is higher than 150 ° C., there are many side reactions, and the molecular weight may not be increased linearly. In this reaction, the molecular weight can be controlled by adjusting the mixing ratio of the bifunctional epoxy resin and the bifunctional phenol. When the blending ratio of the bifunctional epoxy resin and the bifunctional phenol is close to 1, the molecular weight can be increased.

The bifunctional or higher functional epoxy resin used in the present invention acts as an adhesive component. Therefore, the blending amount is preferably 10 to 200 parts by weight of a bifunctional or more epoxy resin per 100 parts by weight of the high molecular weight epoxy polymer. As the bifunctional or higher epoxy resin, any compound having two or more epoxy groups in a molecule may be used. For example, a phenol novolak epoxy resin, a cresol novolak epoxy resin, a resol epoxy resin Epoxy resins (phenolic epoxy resins) which are glycidyl ethers of phenols, such as bisphenol type epoxy resins, alicyclic epoxy resins, epoxidized polybutadiene, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, isocyanurate type Epoxy resins, flexible epoxy resins, and the like are included. Above all, a phenolic epoxy resin or a mixture of a phenolic epoxy resin and a polyfunctional epoxy resin is preferable because the solder heat resistance and the peel strength are not reduced. In order to cure a bifunctional or higher epoxy resin, a curing agent and a curing accelerator for the epoxy resin can be blended. As a curing agent and a curing accelerator of the epoxy resin, novolak type phenol resin,
Dicyandiamide, acid anhydrides, amines, imidazoles, phosphines and the like can be mentioned, and these are used alone or in combination.

When the high molecular weight epoxy polymer is appropriately made three-dimensional using a crosslinking agent, heat resistance, solvent resistance, water absorption and insulation reliability are improved. Examples of the cross-linking agent include block-type polyisocyanates in which isocyanate groups are blocked using a polyisocyanate and a compound having active hydrogen as a masking agent, silanol compounds, metal oxides, acid anhydrides, and the like. Especially, it is desirable to use a block type polyisocyanate. This is because the reactivity of the crosslinking agent can be easily controlled and the storage stability of the adhesive varnish can be easily ensured, and the film adhesive and the multilayer printed wiring board using the same do not deteriorate. Examples of the block type polyisocyanate include tolylene diisocyanate (TDI) and isophorone diisocyanate (IP) blocked with a phenol-based, oxime-based, alcohol-based masking agent, and the like.
DI), diphenylmethane diisocyanate (MD
I), hexamethylene diisocyanate (HDI) and the like. In order to improve the heat resistance of the multilayer printed wiring board, TDI and IPDI blocked with a phenol novolak-based masking agent are preferred. Further, these masking agents and isocyanates may be used in combination. These blending amounts are based on the high molecular weight epoxy polymer 10
The amount is preferably 5 to 100 parts by weight with respect to 0 parts by weight.

It is preferable to use an amide-based or ketone-based solvent as a varnish solvent. This is because the solvent used when synthesizing the high molecular weight epoxy polymer can be used as it is. Examples of the amide solvent include formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide,
N, N-dimethylacetamide, N, N, N ', N'-
Examples include tetramethylurea, 2-pyrrolidone, N-methylpyrrolidone, carbamic acid esters and the like. Also,
As the ketone solvent, methyl isobutyl ketone, 2-
Heptanone, 4-heptanone, 2-octanone, cyclohexanone, acetylacetone, 2,3-butanedione and the like are mentioned. These can be used in combination, or may be used in combination with other solvents such as ethers. The amount of the solvent to be used with respect to the solid component is appropriately determined so that the viscosity of the varnish becomes a predetermined value.

When the molecular weight of the high molecular weight epoxy polymer is low, the viscosity of the varnish can be adjusted to 6 to 12 Pa · s by heating at 35 to 45 ° C. for 6 to 24 hours.

Examples of the method for forming the varnish into a film include a method of casting on a smooth plate such as a glass plate and a method of applying the varnish on a base film. Examples of the base film include a polypropylene film, a polyethylene terephthalate film, aluminum foil, and copper foil. It is convenient to use copper foil as the base film because the base film can be used as a constituent material of the printed wiring board as it is. The thickness of the base film used is 12.5 to 125 μm, and the thickness of the adhesive layer is appropriately selected from 10 to 50 μm depending on the application. In order to form an electric insulating layer, it is said that the thickness of the adhesive layer is preferably 50 μm.
Examples of a method for applying the varnish on the base film include a method using a pipe doctor coater.

[0018]

【Example】

Example 1 Synthesis of high molecular weight epoxy polymer 205.6 g of a bisphenol A type epoxy resin having an epoxy equivalent of 171.3 as a bifunctional epoxy resin, 139.5 g of bisphenol A having a hydroxyl equivalent of 114.0 g as a bifunctional phenol, and water as a catalyst Lithium oxide 0.9
3 g was dissolved in 1384.1 g of N, N-dimethylacetamide, which is an amide solvent, to give a solid concentration of 30% by weight in the reaction system. While mechanically stirring this, 14
Keep the temperature of the reaction system at 120 ° C in a 0 ° C oil bath,
The mixture was stirred for 10 hours. As a result, the viscosity becomes 6,40.
The reaction was completed by saturation at 0 mPa · s, and a solution of 30% by weight of a high molecular weight epoxy polymer was obtained. The molecular weight of the high molecular weight epoxy polymer dissolved in this solution is 45
It was 0000.

Preparation of Varnish A A bisphenol A type epoxy resin having an epoxy equivalent of 171.5 was added to an equivalent of 100 parts (parts by weight, hereinafter the same) of a solid content of a high molecular weight epoxy polymer having a molecular weight of 450,000 in the obtained solution. 24 parts and 15 parts of isocyanate were dissolved to obtain Varnish A. Varnish A has a viscosity of 8.8 Pa
s.

Example 2 Synthesis of high molecular weight epoxy polymer 205.6 g of bisphenol A type epoxy resin having an epoxy equivalent of 171.3 as a bifunctional epoxy resin, 145.0 g of bisphenol A having a hydroxyl equivalent of 114.0 as bifunctional phenols, Sodium hydroxide 0.
93 g of N, N-dimethylacetamide as an amide solvent was dissolved in 1384.1 g, and the solid concentration in the reaction system was adjusted to 30% by weight. While mechanically stirring this, 1
The temperature of the reaction system was maintained at 120 ° C. in an oil bath at 40 ° C., and the reaction was continued until the viscosity became 2,400 mPa · s. As a result, a 30% by weight solution of a high molecular weight epoxy polymer was obtained. The molecular weight of the high molecular weight epoxy polymer dissolved in this solution was 250,000.

Preparation of Varnish B An epoxy equivalent of 1 was added to the obtained solution in an amount equivalent to 100 parts by weight of a solid content of a high molecular weight epoxy polymer having a molecular weight of 250,000.
24 parts of 71.5 bisphenol A type epoxy resin and 15 parts of isocyanate were dissolved and then heated at 40 ° C. for 12 hours to obtain Varnish B. Varnish B has a viscosity of
It was 8.8 Pa · s.

Comparative Example Preparation of Varnish C A varnish C was obtained in the same manner as the varnish B except that heating was not performed at 40 ° C. for 12 hours. Varnish C has a viscosity of 3.1 Pa ·
s.

Preparation of Film Adhesive Part 1 Varnish A, Varnish B and Varnish C were each 50 μm thick.
m of a polyethylene terephthalate film having a thickness of 50 μm after drying.
C. for 3 minutes and 150.degree. C. for 3 minutes to obtain a film adhesive. Visual inspection of the adhesive surface of the resulting film adhesive revealed that no foaming was observed. In addition, the amount of volatile components determined from the loss on heating when heated at 200 ° C. for 5 minutes was 3.5% by weight in each case.

Preparation of Film Adhesive Part 2 The heating and drying conditions were changed to 100 ° C. for 1.2 minutes and 175 ° C. for 1.2 minutes, except that film adhesive was prepared in the same manner as in Preparation of Film Adhesive Part 1. I got Foaming was not observed in the film adhesive obtained using the varnishes A and B, but foaming was observed in the film adhesive obtained using the varnish C. In addition, the amount of volatile components determined from the loss on heating when heated at 200 ° C. for 5 minutes was 3.5% by weight in each case.

[0025]

According to the present invention, since foaming can be suppressed even when the drying temperature is increased in the drying process for producing the film adhesive, the production speed can be increased, and The target value is great.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takahiro Tanabe 1500 Ogawa Oji, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd.

Claims (4)

[Claims] 1. A varnish having a composition containing a high molecular weight epoxy polymer having film-forming ability and a bifunctional or higher epoxy resin as essential components dissolved in a solvent and having a viscosity at 25 ° C. of 6 to 12 Pa · s. Is formed into a film and further dried to a B stage. 2. A high-molecular-weight epoxy polymer having a film-forming ability has a weight average molecular weight of 350,000 to 5 in terms of standard polystyrene by gel permeation chromatography.
The method for producing a film adhesive according to claim 1, wherein the molecular weight is 50,000. 3. The varnish is obtained by dissolving a composition containing a high molecular weight epoxy polymer having a film-forming ability and a bifunctional or higher epoxy resin as an essential component in a solvent and heating the mixture. 2. The method for producing a film adhesive according to item 1. 4. A high-molecular-weight epoxy polymer having a film-forming ability, comprising a bifunctional epoxy resin and a bifunctional phenol in a ratio of 0.9 to 1.1 equivalents of phenolic hydroxyl group to 1 equivalent of epoxy group. 4. The method for producing a film adhesive according to claim 1, wherein the adhesive is a high molecular weight epoxy polymer obtained by polymerization.