JPH02274783A - Self-adhesive composition and self-adhesive tape or sheet - Google Patents

Abstract

PURPOSE:To form an adhesive composition having good adhesiveness to a rugged surface and useful for the manufacture of a masking tape, etc., used in plating the terminal area of a printed board, etc., by incorporating thermally expansive microcapsules into a silicone self-adhesive or its mixture with an acrylic self-adhesive. CONSTITUTION:The subject composition comprises a silicone self-adhesive or its mixture with an acrylic self-adhesive, and thermally expansive microcapsules. The content of the microcapsules is usually about 1 to 30wt.% based on the solids of the self-adhesive. The thermally expansive microcapsules comprise, e.g. microcapsules containing gas, such as butane or propane, and have particle diameters preferably ranging from 10 to 20mum. Thermoplastics are suitably used to form the shell of the microcapsule.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an adhesive composition that can be used in the production of masking tapes used for plating terminals of printed circuit boards and flexible circuit boards, and the adhesive composition. (hereinafter, the adhesive tape or sheet may be simply referred to as an adhesive tape) using the adhesive tape or sheet.

[Prior Art/Problems to be Solved by the Invention] When plating the terminal portions of printed circuit boards, it is common to mask the unplated portions using masking tape.

However, the mask portion of the substrate is not a smooth surface because the previously formed solder layer, plating layer, etc. are finely distributed. When adhesive tape is applied to such a surface, the adhesion is not sufficient. In particular, in recent years, the content of circuits has become more and more integrated and microscopic, as well as becoming multi-layered and their surfaces becoming finer and higher in height, making it increasingly difficult for adhesive tape to adhere to the masking surface. .

However, if the adhesion of the tape to the mask surface deteriorates, the plating liquid will penetrate into the boundary area, impairing the precision of the plating finish and causing malfunctions.

By the way, the adhesive tapes generally used for the above purposes are:
It is designed to use a silicone adhesive to prevent the infiltration of Menki liquid due to surface tension, and to increase the thickness of the adhesive layer so that it adheres as closely as possible to the unevenness of the surface.

In addition, an acrylic adhesive was added to an expensive silicone adhesive to obtain the same effect as above.
57355).

Therefore, the unevenness on the masking surface of the substrate was 0.050 m.
It has been found that the thickness of the adhesive layer is required to be 0.075 mm or more when the adhesive layer is 0.075 mm or more. ,
This tends to result in insufficient drying and insufficient crosslinking, resulting in lower production speed and increased costs due to the use of a large amount of adhesive, making it expensive.

In addition, when the adhesive layer thickness is 0.075 mm or more,
When the tape is wound around a core to form a tape, the adhesive tends to ooze out to the side of the tape, which causes the tape to break during unwinding, resulting in poor parting lines and making it difficult to obtain a satisfactory masking effect. There is.

Therefore, it has been proposed to use a so-called chemical foaming agent that is dispersed in the adhesive by heating, or to foam the adhesive layer by adding a high boiling point solvent. This tends to cause the bubbles to collapse and become integrated, resulting in a substantially bubble-free adhesive, and when wound up into a tape, the portion near the core tends to be in a nearly unfoamed state.

In addition, it has been proposed to add hollow glass beads or glass balloons to fix air bubbles, but the dispersibility is poor because the specific gravity of the beads and balloons is significantly different.
In addition, during the drying process after applying the adhesive solution to the base material, pieces and balloons move to the surface layer, resulting in a decrease in the adhesiveness of the adhesive tape, and the roughening of the surface, which actually encourages penetration of the plating liquid. becomes.

Therefore, an object of the present invention is to provide an adhesive tape or a seal that solves the problems of the prior art as described above, and a further object is to provide an adhesive composition that can be used for the adhesive tape. It is about providing something.

[Means to solve the problem]

The present invention provides (1) an adhesive composition comprising a silicone adhesive, or a silicone adhesive and an acrylic adhesive, and thermally expandable microcapsules, and (2) at least one side of a base material. and an adhesive tape or sheet provided with an adhesive layer formed by thermally expanding the thermally expandable microcapsules in the adhesive composition described in (1) above.

In the present invention, heat-expandable microcapsules are made of a material that expands by heat, for example, by heating to 100-150°C, the heat-expandable microcapsules are expanded by 20-70 times, preferably 25-45 times.
It is a thermally expandable microcapsule containing a gaseous substance such as butane gas or propane gas, which expands twice as much. The shell of the microcapsule is preferably made of a thermoplastic plastic (for example, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-methyl methacrylate copolymer, etc.).The heat-expandable microcapsule usually has a particle size of 1 ~50 microns, preferably 10-20
They are micron-sized spherules. Examples of such thermally expandable microcapsules include "Matsumoto Microspheres" manufactured by Matsumoto Yushi Seiyaku (■) and "Isox Pancell J (manufactured by Nihon Philite ■)."

The amount of thermally expandable microcapsules added to the adhesive composition is usually 1 to 30% by weight, preferably 2 to 10% by weight.

The silicone-based adhesive in the adhesive layer of the present invention is preferably an adhesive that uses silicone rubber as an elastomer, and is composed of silicone rubber, silicone resin, cross-curing agent, and the like. More specifically, Shinetsu Silicone KR-120, KR130, Toshi Silicone 5H-42
80 grade is used. Further, as the acrylic adhesive, acrylic acid ester polymers of alcohols having 4 to 14 carbon atoms or copolymers thereof are preferably used, and more specifically, butyl acrylate and octyl acrylate are used. Ru. When using silicone adhesive and acrylic adhesive together, the mixing ratio of each component is 10010 to 100/
400, preferably 100150 to 100/250.

The adhesive composition of the present invention further includes a curing agent (for example,
Peroxides such as silver oxide, cumene hydroperoxide, etc.), platinum catalysts, organotin catalysts, etc. may also be blended.

The adhesive tape of the present invention is such that the adhesive layer is layered on the adhesive layer and thermally expandable microcapsule particles are thermally expanded.
It is something that has been established.

Such an adhesive tape for boat fishing is manufactured as follows. That is, it is manufactured by applying the pressure-sensitive adhesive composition to a base material and then thermally expanding the thermally expandable microcapsule particles in the pressure-sensitive adhesive composition to form a bubble-like pressure-sensitive adhesive layer containing air.

The thickness of the adhesive layer in the adhesive tape of the present invention is usually 30 to 2001 nm, preferably 75 to 150 μm.

In order to produce a pressure-sensitive adhesive tape with such a pressure-sensitive adhesive layer thickness, the pressure-sensitive adhesive composition is usually deposited on the substrate at a rate of 30 to 700 g/nf (wet), preferably 100 to 400 g/nf (wet). It is preferable to apply.

The amount is the amount when the thermally expandable microcapsule is in a foamed state, and the amount is 100% when the thermally expandable microcapsule is in an unfoamed state.
It is preferable that the pressure-sensitive adhesive composition is applied in an amount of ~1000 g/wet. Note that this amount is based on an adhesive solid content of 20%.

In the present invention, by heating the adhesive composition mixed with thermally expandable capsules, the capsules expand within the adhesive composition, and when the adhesive composition is then cooled, the inside of the adhesive composition becomes a bubble containing air. As a result, an air-containing foam adhesive layer is formed.

In the adhesive tape of the present invention, at least one adhesive layer may be further provided on the adhesive layer. In this way, the smoothness of the surface and the improved adhesion to the surface of the adherend result in good adhesion to uneven surfaces and the effect of preventing penetration of the plating solution. The adhesives used here include the aforementioned adhesives that do not contain thermally expandable microcapsules, such as silicone adhesives, acrylic adhesives, and mixtures thereof, such as Shin-Etsu Silicone KR-120, Toshiba Silicone 5H-4280, etc., polybutyl acrylate, polyoctyl acrylate, etc. are used alone or in a mixed system, and the thickness is 2 to 50 μm, preferably 5 to 2 μm.
It is 0 μm.

In the present invention, the base material may be any material commonly used in the field, such as paper, plastic nut film, etc., and particularly preferably, a water-resistant base material is used.

〔Example〕

Example 1 A curing agent (
5 parts by weight of Matsumoto Microsphere F-50D (hereinafter referred to as F50D)
Parts by weight were added and mixed with stirring, applied to one side of a 25 μm polyester film at a concentration of 40 g/n (dry), and heated and cured at 150'C for 5 minutes to prepare a tape. A sample without the addition of Matsumoto Microspheres-F-50D was prepared.

Example 2 50 parts by weight of the above KR-120 and a curing agent (BPO) were added to 100 parts by weight of butyl acrylate-acrylic acid copolymer.
An adhesive tape was obtained in the same manner by adding 5 parts by weight of l'-50D to 1.5 parts by weight.

Examples 3 to 8, Comparative Examples 1 to 2, Experimental Example 1 In Examples 1 and 2, the amount of microcapsule particles added was 1 to 1.
Samples were prepared in which the concentration was varied by 10% by weight, and the test results of the samples are shown in Table 1.

(Test method) ・Glue residue test Each pressure-sensitive adhesive tape was pressed onto a glass epoxy printed circuit board (copper terminal 30 μ thick product) at a speed of 1 m/min with a heated rubber roller at 70°C, and aqueous H2S Oa solution (p) was applied. I-1) at 60°C for 30 minutes, then washed with water and dried. Thereafter, it is peeled off under normal conditions and visually evaluated.

○: No abnormality △: Partial adhesive residue/plating liquid immersion test Nigarasu epoxy printed circuit boards with copper terminal thickness varied from 30 to 150 μm were used to attach tape, and immersed using the method of the adhesive residue test described above. death,
Evaluate visually and microscopically.

(The following is a blank space) [Effect of the invention] The adhesive tape having a bubble-containing adhesive layer manufactured using the adhesive composition of the present invention has no air bubbles even when the same amount of the adhesive composition is used. Compared to an adhesive tape with an adhesive-free layer, the finished thickness of the adhesive layer is 1.2
It is possible to obtain an air-containing foam-like adhesive layer that is approximately 3 times as large and does not break even under pressure.

This improves the adhesion of the adhesive layer to the object to be adhered to, improves the adhesion to highly uneven surfaces, and improves the effectiveness of the masking tape by inhibiting the penetration of plating liquid and the like. Furthermore, since the amount of adhesive applied can be reduced, the material cost can be reduced without drying the solvent bone or reducing the crosslinking reaction.

Claims (4)

[Claims] (1) An adhesive composition comprising a silicone adhesive, a silicone adhesive, an acrylic adhesive, and thermally expandable microcapsules. (2) An adhesive composition in which the content of thermally expandable microcapsules is 1 to 30% by weight based on the solid content of the adhesive. (3) An adhesive tape or sheet comprising an adhesive layer formed from the adhesive composition according to claim 1, which is formed by thermally expanding thermally expandable microcapsules, on at least one side of a base material. (4) An adhesive tape or sheet comprising at least one adhesive layer further provided on the adhesive layer of the adhesive tape or sheet according to claim 3.