JPH01282275A - Conductive adhesive - Google Patents

Abstract

PURPOSE:To obtain the subject adhesive excellent in adhesive strength and electrical conductivity and useful for adhesion between respective electrical conductors requiring turning on electricity, adhesive-assembly of an antistatic housing, etc., by mixing a specified vapor phase grown carbon fiber having a specified amount of acidic functional groups in the adhesive. CONSTITUTION:An objective adhesive, containing a vapor phase grown carbon fiber [preferably 7.06-6.89 lattice constant in structure analysis by X-ray diffraction] with 0.01-2mum, preferably 0.01-0.5mum diameter and <=2, preferably 10-1000 aspect ratio and having 0.5-300mueq/g, preferably 1.5-150mueq/g acidic functional groups.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides adhesive strength and Related to adhesives with excellent conductivity.

Adhesives are usually electrically insulating, but in the electrical and electronic fields, they are used as adhesives to bond conductive or antistatic features and maintain conductivity, with excellent conductivity and high adhesive strength. It has been desired to develop an adhesive having the following properties.

(Prior Art) Conventionally, as a method of imparting conductivity to an adhesive, a method of blending a conductive substance has been taken. However, this property makes it extremely difficult to achieve both excellent conductivity and high adhesive strength as long as conventional conductive materials are used. For example, when using metal powder such as copper powder as a conductive substance, even though the metal powder itself has excellent conductivity,
It is easy to separate from the adhesive base resin in the adhesive, and the balance between conductivity and adhesive strength is easily lost, and the particle shape and size distribution are inappropriate, and the surface is coated with a non-conductive oxide film. It was difficult to obtain sufficient conductivity due to being covered.

In the case of carbon fibers, the fiber diameter is large, which tends to reduce the homogeneity of the adhesive surface and cause problems with adhesive strength, and when the amount of carbon fibers is small, problems such as lack of uniform conductivity occur.

In the case of carbon black, the particle size is small and there is no problem with homogeneity, but it does not have sufficient conductivity unless it maintains a secondary agglomerated state, and on the other hand, the agglomerated state must be broken in order to increase adhesive strength. There were other problems.

(Problems to be Solved by the Invention) In order to develop an adhesive that has excellent conductivity and excellent adhesion between materials as an adhesive, it is necessary to It is necessary to have good adhesive strength by uniformly dispersing the adhesive, and to be evenly distributed and filled even in the very narrow gaps between the adhered materials. In response, the present inventors have conducted research focusing on the use of vapor-grown carbon fiber as a conductive material, but due to modification of its shape and surface, homogeneous dispersion with the adhesive base material resin has been achieved. The present invention was achieved by discovering that it is possible to exhibit excellent conductivity and strong adhesive strength.

(Means for Solving the Problems) The present invention uses vapor grown carbon fibers having an acidic functional group of 0.5 to 300 μeq/g, a diameter of 0.01 to 2.0 μm, and an aspect ratio of 2 or more. It is a conductive adhesive containing.

In the present invention, the vapor-grown carbonaceous fiber is a whisker-like carbonaceous fiber produced by heating a carbon source such as a hydrocarbon in the presence of a catalyst and growing it in a vapor phase, or
This is a heat-treated carbonaceous material, and when observed with an electron microscope, it has a unique shape consisting of a core and a ring-like carbon layer surrounding it. It is a product that has undergone processing such as crushing, crushing, or cutting.

The vapor grown carbon fiber of the present invention has a diameter of 2.0 to 0.0
1 p m, preferably I It m ~ 0.01 μm,
In particular, it is 0.5 to 0.01 μm, and the aspect ratio (ratio of length to diameter: length/diameter) is 2 or more, preferably 5 or more, and most preferably 10 or more and 1000 or less.

In the present invention, the vapor grown carbonaceous fiber is also characterized in that it has acidic functional groups of 0.5 to 300 μeq/g, and the amount of acidic functional groups is preferably 1 to 200 μeq/g.
, especially in the range of 1.5 to 150 μeq/g.

When the amount of acidic functional groups is within this range, it has excellent affinity with the adhesive base polymer and is not only easy to work with when compounding, but also has excellent dispersibility, and exhibits conductivity and adhesive strength. It is also extremely effective.

Methods for producing vapor grown carbon fibers having acidic functional groups include oxidizing vapor grown carbon fibers with an oxidizing gas such as oxygen or ozone or an oxidizing agent such as nitric acid, electrolytic oxidation, and plasma. Treatment methods, grafting methods, etc. may be used.

In the present invention, the vapor grown carbonaceous fiber also has high carbon purity, preferably 97.5% or more, particularly 98%
or more, most preferably 98.5% or more.

In addition, the vapor grown carbon fiber of the present invention is an easily graphitizable carbonaceous material, and among them, in the structural analysis by X-ray analysis, the lattice constant is in the range of 7.1 to 6.88. Preferably, a range of 7.06 to 6.89 is particularly preferable.

The conductive adhesive of the present invention is made by mixing and dispersing the above-mentioned vapor-grown carbon fibers with an adhesive base polymer, and if necessary, using a solvent or dispersant such as an organic solvent or water, or using other stabilizing agents. Additives and drugs such as fluid control agents and flow regulators may be added.

The blending amount of the vapor grown carbon fiber can be appropriately set depending on the performance required of the adhesive.

- For boat fishing, increasing the amount of vapor grown carbon fiber in the adhesive-based polymer increases conductivity, which is preferable, but there is a limit in terms of adhesive strength and workability. and preferably 1 to 80% in the final adhesive component,
Particularly preferably 2 to 60%, most preferably 3 to 40%
is within the range of

In the present invention, the polymer serving as the adhesive base can be selected from organic polymers and inorganic polymers, and is not particularly limited. Examples of organic polymers include polyvinyl alcohol, EVA, polyvinyl acetate, polyvinyl chloride, polybutadiene rubber, styrene-butadiene rubber, isoprene rubber, various rubbers such as acrylic rubber, polyacrylic ester, polyacrylic acid, Inorganic polymers such as unsaturated polyester, alkyd resin, addition cured imide, polyamic acid ester, modified nylon, urea resin, melamine resin, epoxy resin, silicone resin, phenol resin, polyurethane, modified cellulose, and casein, water glass , metal salt-modified water glass, aluminates, polyphosphates, etc.

Other additives and chemicals include inorganic powders, crosslinking agents, surfactants for emulsification and dispersion, heat and antioxidants, and the like.

(Example) Example 1 Epoxy adhesive (Bond Quick 5 manufactured by Konishi Co., Ltd.)
2g, a small amount of vapor-grown carbon fiber (trisacetylacetonate iron and benzene were introduced into a heating space at 1300°C and synthesized in a suspended state. Carbon content 98.8% or more, lattice constant 7.01) When crushed and observed under an electron microscope, the diameter was 0.
05 to 0.1 μm, fibers with a length of substantially 5 μm or more are oxidized with oxygen-containing gas, and the amount of acidic functional groups is 35 μeq/g.
After blending the fibers in a predetermined amount (wt%) and thoroughly dispersing and mixing them, the adhesive area was 1 cm x 1 cm, and the distance between the adhesive surfaces was 1 cm.
After bonding two aluminum plates together at a thickness of 0.00 μm, the electrical conductivity (resistance) between the aluminum plates was measured.

For comparison, acetylene blanks, pitch-based carbon fibers (crushed material with a diameter of 14 μm), and vapor-grown carbon fibers without acidic functional groups (shown without acidic functional groups) were mixed as conductive materials, and similar results were obtained. The test was conducted.

The results are shown in Table 1. Clearly, the adhesive of the invention exhibits low resistance and good conductivity.

Example 2 The conductive adhesive of Example 1 was used to butt and adhere the end faces of stainless steel cylinders, and a tensile fracture test was conducted to compare the adhesive strengths. The results are shown in Table 2.

Example 3 A predetermined conductive adhesive was prepared in the same manner as in Example 1, using the vapor grown carbon fiber of Example 1 oxidized to an acidic functional group content of 80 μeq/g and changing the adhesive. Example 2
Conductivity (resistance) and adhesion were evaluated in the same manner as above. The results are shown in Tables 3 and 4, respectively.

For comparison, vapor grown fibers without acidic functional groups (shown without acidic functional groups) and acetylene black were also evaluated.

(Effects of the Invention) The conductive adhesive of the present invention can be uniformly applied to the adhesive surface and exhibit excellent conductivity without impairing adhesive strength, so it has excellent adhesion and antistatic properties between conductors that require electricity to flow. It is useful in industrial applications such as adhesive assembly of housings. In particular, it is extremely effective when the bonding distance between the bonded materials is small and the bonding strength and conductivity are to be developed.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] It has an acidic functional group of 0.5 to 300 μeq/g and a diameter of 0.5 μeq/g.
Conductive adhesive containing vapor grown carbon fibers having a diameter of 01 to 2.0 μm and an aspect ratio of 2 or more