JPH0711214A - Adhesive composition - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a solvent-based adhesive composition having excellent peeling strength and solder heat resistance for a printed circuit board having a high circuit density, and having low viscosity and good coating workability. [Structure] An adhesive composition containing a polyvinyl acetoacetal resin having a degree of polymerization of less than 1000, particularly containing the polyvinyl acetoacetal resin having a low degree of polymerization, the polyvinyl acetal resin having a degree of polymerization of 1000 or more, and a thermosetting resin. Characteristic adhesive composition

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive composition suitable for adhering a phenolic resin-based copper clad laminate. More specifically, it relates to a low-viscosity adhesive composition for solution-type laminates, which contains a polyvinyl acetoacetal resin having a low degree of polymerization.

[0002]

2. Description of the Related Art Phenolic resin-based copper-clad laminates used in electronic equipment and the like are usually composed of copper foil, phenolic resin-impregnated paper, and an adhesive agent for adhering them to each other. A printed circuit board is manufactured. As an adhesive for laminating the copper-clad laminate, a solution-type adhesive composition composed of a polyvinyl acetal resin typified by a polyvinyl butyral resin and a thermosetting resin such as a phenol resin or an epoxy resin has been widely used. ing.

With respect to this printed circuit board, the trend toward higher circuit densities has become remarkable as the weight and size of various electric appliances have been reduced in recent years. As a result, further improvement in heat resistance and peeling strength of the copper foil is desired as an adhesive.

In order to improve the physical properties of the adhesive, there has been proposed a method in which the polyvinyl acetal resin to be used has a high molecular weight. However, this increases the viscosity of the adhesive, but it lowers the coating workability. On the other hand, if the amount of solvent is increased to reduce the viscosity, the product price and coating cost will rise.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of intensive studies conducted by the present inventors in order to solve the above-mentioned problems in a solvent-based adhesive composition containing a conventional polyvinyl acetal resin and a thermosetting resin, an adhesive composition was obtained. It has been found that by adding a polyvinyl acetoacetal resin having a low degree of polymerization to the product, it is possible to achieve a low viscosity without lowering the physical properties. The present invention has been made based on such findings, and an object thereof is to provide a solvent-type adhesive composition suitable for a printed circuit board having a low viscosity, good coating workability, and high circuit density.

[0006]

The adhesive composition according to the present invention is an adhesive composition containing a polyvinyl acetoacetal resin having a degree of polymerization of less than 1000, and in particular, the polyvinyl acetoacetal resin having a low degree of polymerization and the degree of polymerization of 1000. An adhesive composition containing the above polyvinyl acetal resins and a thermosetting resin.

Polyvinyl acetoacetal resin is obtained by acetalizing polyvinyl alcohol mainly or partially with acetaldehyde, and is one kind of polyvinyl acetal resin, which usually contains unreacted acetal groups in addition to unreacted groups. It has a hydroxyl group and a vinyl acetate group. Therefore, the polyvinyl acetoacetal resin is composed of a polyvinyl alcohol portion, a vinyl acetate portion and an acetal (form acetal, acetoacetal, butyl acetal etc. are collectively referred to as acetal) portion, and in the present invention, all the The proportion of the acetal portion means the proportion to ++.

To synthesize the polyvinyl acetoacetal resin used in the present invention, a polyvinyl alcohol having a degree of polymerization of less than 1000, preferably 300 to 800 is used, which is mainly or partially acetalized with acetaldehyde to obtain a degree of polymerization. A polyvinyl acetoacetal resin of less than 1000 is obtained. When the degree of polymerization is 1000 or more, the effect of lowering the viscosity becomes small, and when it is less than 300, the heat resistance and the adhesive strength are insufficient, which is not preferable.
The degree of polymerization is measured by the measuring method shown in JIS K6728.

Further, the ratio of the total acetalization portion in the polyvinyl acetoacetal resin, that is, the total acetalization degree is 6
It is preferably 5 mol% or more, particularly preferably 70 mol% or more. When the proportion of all acetalized portions is less than 65 mol%, the heat resistance and the peel strength between the obtained adhesive composition and the copper foil are insufficient. Further, the proportion of acetalized portion by acetaldehyde, that is, the degree of acetoacetalization is preferably 85 to 100 mol% of the total acetalized portion. If it is less than 85 mol%, heat resistance, particularly solder heat resistance, becomes insufficient.

The adhesive composition of the present invention comprises the polyvinyl acetoacetal resin having a low degree of polymerization as an essential component, and is prepared by dissolving it in an appropriate organic solvent together with other resin components. As other resin components, it is preferable to blend a polyvinyl acetal resin having a polymerization degree of 1000 or more, a thermosetting resin, and the like.

The kind of polyvinyl acetal resin having a degree of polymerization of 1000 or more used in combination is not limited at all, but preferably at least one selected from polyvinyl formal, polyvinyl acetoacetal having a degree of polymerization of 1000 or more, and polyvinyl butyral. Resin is used. The degree of polymerization is 1000 to 2500, especially 1
The range of 500-2200 is preferable. Degree of polymerization is 2500
If it exceeds 100, the effect of lowering the viscosity becomes small, and if it exceeds 100
When it is less than 0, heat resistance and adhesive strength are insufficient, which is not preferable.

The blending ratio of the polyvinyl acetoacetal resin having a degree of polymerization of less than 1000 and the polyvinyl acetal resin having a degree of polymerization of 1000 or more is preferably in the range of 9: 1 to 2: 1 by weight, particularly 5: 1 to 3: 1. Ranges are preferred. If the blending ratio exceeds 9: 1, the heat resistance and the adhesive strength will be insufficient, and if it is less than 2: 1, the viscosity reducing effect will be small, such being undesirable.

Phenol resins, epoxy resins, melamine resins and the like are preferably used as the thermosetting resin. The blending amount of these thermosetting resins in the adhesive composition is the total amount of the polyvinyl acetoacetal resin having a degree of polymerization of less than 1000 and the polyvinyl acetal resin having a degree of polymerization of 1000 or more:
The solid content weight ratio of the thermosetting resin is preferably in the range of 2: 1 to 1: 3, and particularly preferably in the range of 1: 1 to 2: 3.
If this weight ratio exceeds 2: 1, that is, if the amount of the thermosetting resin compounded is small, the heat resistance is insufficient, whereas if it is less than 1: 3, the adhesive strength decreases.

[0014]

【Example】

[Example 1] (Preparation of adhesive composition and preparation of copper-clad laminate) Polyvinyl acetoacetal resin (Eslek KS-1, manufactured by Sekisui Chemical Co., Ltd., polymerization degree 500, total acetalization degree 70.
0 mol%, acetoacetalization degree 100 mol%) 104
g, polyvinyl butyral resin (Sekisui Chemical Co., Ltd., S-REC BX-2, degree of polymerization: 1700) 22 g, phenol resin (Sumitomo Dures Co., Ltd. PR51406) 19
1 g and epoxy resin (Epototo Y manufactured by Tohto Kasei Co., Ltd.)
64 g of DCN704) was dissolved in 619 g of a mixed solvent of toluene / methanol / acetone (weight ratio 3/1/1) to prepare an adhesive composition according to the present invention. This adhesive composition has a solid content concentration of 30.4 wt% and a viscosity of 25 ° C.
Was 870 cps.

Next, this adhesive composition was applied to a copper foil for printed boards having a thickness of 35 μm and dried at 150 ° C. for 4 minutes to obtain a copper foil with an adhesive having a thickness of 30 μm. This adhesive-coated copper foil and phenol-impregnated paper are heated at 150 ° C for 70 minutes,
Pressure molding was performed at kg / cm ² to obtain a copper clad laminate.

[Comparative Example 1] (Preparation of adhesive composition and preparation of copper clad laminate) Polyvinyl butyral resin (S-REC B manufactured by Sekisui Chemical Co., Ltd.)
X-2, degree of polymerization 1700) 87.5 g, phenol resin (PR51406 manufactured by Sumitomo Dures Co., Ltd.) 87.5 g, and epoxy resin (Epototo YDCN manufactured by Toto Kasei Co., Ltd.)
704) 35 g was dissolved in toluene / methanol / acetone (weight ratio 3/1/1) mixed solvent 790 g to prepare an adhesive composition. The solid concentration of this adhesive composition is 1
At 7.5 wt%, the viscosity was 1000 cps at 25 ° C. Using this adhesive composition, a copper clad laminate was obtained in the same manner as in Example 1.

(Physical Properties of Adhesive Composition and Copper Clad Laminate) With respect to each of the laminates obtained in Example 1 and Comparative Example 1, the peel strength in the normal state and the solder heat resistance at 260 ° C. were measured. The results are shown in Table 1. Moreover, the viscosity at 25 ° C. was measured while changing the mixed solvent amount in each adhesive composition, and the relationship between the solid content concentration and the viscosity was investigated. The results are shown in FIGS. 1 and 2.

As compared with the adhesive composition of Comparative Example 1 which does not contain a low molecular weight polyvinyl acetoacetal resin, the adhesive composition of the present invention has a low viscosity in spite of a high solid content and a heat resistance and It is clear that the balance of adhesive strength is also excellent.

[0019]

[Table 1] * All are compliant with JIS C6481

[0020]

According to the present invention, by containing a polyvinyl acetoacetal resin having a degree of polymerization of less than 1000 as an essential component, an adhesive composition having a low viscosity and an excellent balance of properties can be obtained. That is, according to the adhesive composition of the present invention, when the solid content concentration is the same as that of the conventional adhesive composition, the viscosity can be made lower, and thus the coating workability is excellent. Further, even if the solid content concentration is increased as compared with the conventional adhesive composition, the same viscosity can be obtained, so that the coating workability is good and it is useful as an adhesive for copper-clad laminates.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a solid content and a viscosity of an adhesive composition of Example 1.

FIG. 2 is a diagram showing the relationship between the solid content and the viscosity of the adhesive composition of Comparative Example 1.

Claims (2)

[Claims] 1. An adhesive composition comprising a polyvinyl acetoacetal resin having a degree of polymerization of less than 1000. 2. The adhesive composition according to claim 1, which contains a polyvinyl acetoacetal resin having a degree of polymerization of less than 1000, a polyvinyl acetal resin having a degree of polymerization of 1000 or more, and a thermosetting resin.