JPH0830175B2 - Conductive adhesive and conductive adhesive sheet using this adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a conductive pressure-sensitive adhesive having a small decrease in conductivity over time and a conductive pressure-sensitive adhesive sheet suitable for electromagnetic wave shielding.

(Prior Art) In recent years, electromagnetic noise emitted from electronic devices such as computers and word processors adversely affects other electronic devices, which is causing an error.

As a member for shielding such electromagnetic noise,
For example, a conductive pressure sensitive adhesive sheet is known, and generally, a conductive pressure sensitive adhesive layer in which metal particles are dispersed in a pressure sensitive adhesive is provided on one surface of a metal sheet. The conductivity in this case may be expressed in the thickness direction of the pressure-sensitive adhesive layer and in the direction perpendicular to the thickness direction, or may be generated only in the thickness direction.

(Problems to be Solved by the Invention) However, while a conductive adhesive sheet for shielding electromagnetic noise is required to have good conductivity for a long period of time, conventional sheets do not sufficiently satisfy such required performance. It was That is, there is a problem in that even if the conductive adhesive sheet exhibits high conductivity immediately after its production, the conductivity gradually decreases with time.

It is an object of the present invention to provide a conductive pressure-sensitive adhesive and a conductive pressure-sensitive adhesive sheet that have extremely little decrease in conductivity with time.

(Means for Solving the Problem) According to the knowledge of the present inventor, the problem of the conductive pressure-sensitive adhesive sheet is that the surface of the metal particles and the metal sheet is oxidized with a metal having low conductivity due to the action of the pressure-sensitive adhesive or the like. It is presumed that it was caused by the formation of objects (rust). The present invention has been completed based on these findings.

That is, the conductive adhesive of the present invention is characterized by containing an acrylic adhesive, metal particles and a triazole compound, the conductive adhesive sheet of the present invention, the conductive adhesive on the surface of the metal sheet The above-mentioned object can be achieved by the provision of a conductive adhesive layer consisting of

As the acrylic pressure-sensitive adhesive in the invention, conventionally known ones are widely used. For example, acrylic acid ester (having 2 carbon atoms)
To 12) as a main component and copolymerized with acrylic acid, methacrylic acid, acrylamide, vinyl acetate, styrene and the like. The dispersant may be either water or a solvent.

As the metal particles for imparting conductivity, nickel, silver, copper, etc. are preferably used. Due to the need to balance conductivity and adhesiveness, particle size is generally 5-100μ
m, and the addition amount is usually 1 to 40 parts by weight with respect to 100 parts by weight of the solid content of the acrylic pressure-sensitive adhesive.

Examples of the triazole-based compound include benzotriazole, tolyltriazole and a potassium salt thereof, 3- (N
-Salicyloyl) amino-1,2,4 triazole, 2-
Benzotriazole compounds such as (2′-hydroxy-5methylphenyl) benzotriazole are mentioned as preferable examples, but the present invention is not limited thereto. If the amount used is too small, it is not possible to sufficiently prevent the decrease in conductivity of the metal particles and the metal sheet, which is thought to be due to the acrylic pressure-sensitive adhesive. It is generally 0.01 to 1.0 part by weight, preferably 0.05 to 0.5 part by weight, based on 100 parts by weight of the solid content of the adhesive.

The procedure for preparing the conductive adhesive of the present invention is not particularly limited. It is preferable to dissolve the triazole-based compound in a solvent such as methanol and then add the triazole-based compound to the pressure-sensitive adhesive composition while stirring. The metal particles may be added to the acrylic pressure-sensitive adhesive at the same time as the triazole compound, or may be added before or after that.

Copper, aluminum or the like is preferably used as the metal sheet constituting the conductive pressure-sensitive adhesive sheet, and the thickness is usually about 10 to 70 μm.

To prepare the conductive pressure-sensitive adhesive sheet, for example, the conductive pressure-sensitive adhesive may be applied on release paper, dried, and transferred to a metal sheet. Alternatively, the release paper may be wound as it is and stored as a wound body without being peeled off from the conductive pressure-sensitive adhesive layer.

(Examples) Hereinafter, "%" and "parts" mean "% by weight" and "parts by weight", respectively.

Example 1 100 parts of an acrylic emulsion pressure-sensitive adhesive (Sekisui Chemical Co., Ltd., Esdyne, solid content 55%), Ni powder (INCO, type 25)
5) 10 parts, dispersant (Daiichi Kogyo Seiyaku, Neogen P) 0.1
Parts, 0.1 part of a defoaming agent (SN Nopco, SN deformer) and 0.3 part of a 33% acetone solution of benzotriazole were mixed to prepare a conductive adhesive. This adhesive is applied on a release paper with a Baker type applicator at a gap of about 0.08 mm, dried at 80 ° C for 5 minutes, and then transferred to a rolled copper foil having a thickness of 35 µm to form conductive adhesive sheets A, B and C. Created. As shown in FIG. 1, the sheets A, B and C are respectively a conductive adhesive layer 2 and a copper foil 1.
have.

After that, A and C were lined up and pressed on the epoxy resin-impregnated glass plate 3, the tape B was adhered so as to straddle both, and the electric resistance of the sheet was measured by the tester 4, and the result of visually observing the appearance was the first. It was as shown in the table.

Example 2 A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that tolyltriazole was used instead of benzotriazole in Example 1, and the electrical resistance of the sheet was measured. The results are shown in Table 1. It was

Example 3 A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that 0.1 part of the potassium salt of tolyltriazole was used in place of the benzotriazole of Example 1, and the electric resistance of the sheet was measured. It was as shown in the table.

Example 4 100 parts of an acrylic solution type adhesive (Soken Chemical's 1604-S, solid content 40%), Cu powder (Fukuda Metal Foil & Powder Co., CE-1)
5) 10 parts and 33% acetone solution of benzotriazole 0.3
Parts were added and mixed to prepare an adhesive, and a conductive adhesive tape was prepared in the same manner as in Example 1. The electric resistance and the like of the tape are shown in Table 1.

Example 5 A conductive adhesive sheet was prepared by using 3- (N-salicyloyl) amino-1,24-triazole instead of benzotriazole in Example 4.

Comparative Example 1 A conductive tape containing no benzotriazole in Example 1 was prepared to prepare a pressure-sensitive adhesive tape. The electric resistance of the sheet was as shown in Table 1.

Comparative Example 2 An electrically conductive adhesive containing no benzotriazole in Example 4 was prepared to prepare an adhesive tape. The electric resistance of the sheet was as shown in Table 1.

As is clear from Table 1, although the conductive adhesive sheet obtained from the conductive adhesive agent of the present invention showed a slight increase in the electrical resistance immediately after the sheet was formed in the atmosphere of high temperature and high humidity for 6 months, As compared with the conductive sheet of the comparative example having an adhesive layer containing no triazole compound, the decrease in conductivity with time was extremely small.

Furthermore, in the comparative example, the surface of the copper foil on the side in contact with the pressure-sensitive adhesive layer turned black over time, whereas the sheet of the present invention did not cause such a change.

Separately from the above examples, the adhesive of the present invention was applied to polyethylene terephthalate with ITO and the conductivity of the adhesive layer was confirmed. The decrease with time was extremely small.

(Effects of the Invention) The conductive pressure-sensitive adhesive of the present invention has an extremely small decrease in conductivity over time. Therefore, it can be suitably used as a conductive pressure-sensitive adhesive sheet for shielding electromagnetic waves.

The conductive pressure-sensitive adhesive sheet of the present invention does not cause discoloration of the metal sheet over time, and the decrease in conductivity is extremely small.

Therefore, it has a high practical value when used for shielding electromagnetic waves.

[Brief description of drawings]

FIG. 1 is a view for explaining the method for measuring the conductivity of the conductive pressure-sensitive adhesive and the conductive pressure-sensitive adhesive sheet of the present invention, where (A) is a plan view and (B) is a sectional view. 1 ... Copper foil, 2 ... Conductive adhesive layer, A, B, C ... Conductive adhesive sheet

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C09J 9/02 JAX 133/04 PGB PGC

Claims (2)

[Claims] 1. A conductive adhesive comprising an acrylic adhesive, metal particles and a triazole compound. 2. A conductive pressure-sensitive adhesive sheet, characterized in that a conductive pressure-sensitive adhesive layer comprising the conductive pressure-sensitive adhesive according to claim 1 is provided on the surface of a metal sheet.