JPS60202166A - Electrically conductive paint - Google Patents

Abstract

PURPOSE:To provide an electrically conductive paint which retains excellent electrical conductivity consistently over a long period of time, neither causes precipitation of copper powder nor forms hard cake when diluted with a solvent, containing a synthetic resin binder, a copper powder, silica powder and a suspending agent as main components. CONSTITUTION:An electrically conductive paint contains a synthetic resin binder (A) (e.g. acrylic or polyester resin), copper powder (B), silica powder (C) and a suspending agent (D) (e.g. polyaminoamide acetate, aminosilane or an alkylamine salt of a polycarboxylic acid) as main components. The powder B is used in a quantity of 90-70pts.wt. per 10-30pts.wt. binde A. The powder C is used in a quantity of 0.5-15pts.wt. per 100pts.wt. powder B and the agent D is used in a quantity of 0.2-10pts.wt. per 100pts.wt. powder B. The paint does not cause precipitation of the copper powder and hence it has good workability and shelf stability and an excellent electromagnetic wave shielding effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a conductive coating material which has good workability and storage stability due to no precipitation of copper-based powder, and has an excellent electromagnetic shielding effect.

[Technical background of the invention and its problems] In recent years, digital communication circuits have become common not only in electronic devices and computers, but also in audio equipment, home appliances, office machines, communication devices, and even game devices. Parts are becoming smaller. Although these digital communications are accurate and have high processing power, they always generate a small amount of noise, and this noise becomes electromagnetic waves and causes interference with other digital devices.

Currently, the main countermeasure against this problem is shielding electromagnetic waves using electromagnetic shielding paint. Ni-based conductive paint is often used as the NvA wave shielding paint, but its electromagnetic shielding effect in the low frequency range is poor, so copper-based conductive paint has recently attracted attention as a solution to this drawback.

However, copper-based paints are more easily oxidized than N1-based paints, and their shielding effectiveness deteriorates over time.
It has drawbacks such as easy sedimentation, poor workability, and tendency to form a hard cake during long-term storage.

[Object of the Invention] The present invention was made in view of the above-mentioned drawbacks, and has excellent electrical conductivity and stability over time, and the copper-based powder does not settle, and even when diluted with a solvent, the settling rate of the copper-based powder is low. The purpose of the present invention is to provide a conductive paint that has excellent workability and storage stability, such as slow build-up and no hard cake formation.

[Summary of the Invention] As a result of extensive research to achieve the above object, the present invention has discovered that the above object can be achieved by using silica powder and an anti-settling agent in combination. .

That is, the present invention is a conductive paint characterized by containing (Δ) a synthetic resin binder, (B) a copper-based powder, (C) a silica powder, and <D> an antisedimentation agent as main components.

-C is characterized in that one type or a mixed system of two or more selected from polyaminoamide acid salts, polycarboxylic acid alkylamine salts, and aminosilanes is used as the sedimentation prevention agent.

Examples of the synthetic resin binder used in the present invention (A>
Acridic A-195 manufactured by Dainippon Ink Chemical Industries, Ltd.
A-196゜AL-216, LR-5 manufactured by Mitsubishi Rayon Co., Ltd.
74゜LR-1065, manufactured by Mitsui Toatsu Chemical Co., Ltd. 1-1044
, L-1020 (all of the above are product names).

As a polyester resin, Bylon 2O- manufactured by Toyobo Co., Ltd.
8S, 2008, and the urethane resin is 81623 manufactured by Mitsui Toatsu Chemical Co., Ltd. L2284, special modified epoxy resins such as Epokey 813.810ST and 811, and examples of styrene-unsaturated alkyd resins include Styresol 4250 (all trade names) manufactured by Dainippon Ink and Chemicals.

(B) copper-based powder as the conductive powder used in the present invention is:
Examples include copper powder, copper alloy powder, and powder having a copper layer on the surface by plating or other methods.

(13) The blending ratio of the copper-based powder is 70 to 90 parts by weight per 10 to 30 parts by weight of the synthetic resin binder (A). If the amount is less than 70 parts by weight, preferred conductivity cannot be obtained, and if it exceeds 90 parts by weight, adhesion is poor and workability is poor, both of which are not preferred.

The (C) silica powder used in the present invention has an average particle size of 3
Silica powder with a diameter of 0 μm or less can be used, preferably 10 μm or less. If the average particle size exceeds 30 μm, however, the appearance of the conductive paint after application will be impaired, and the paint spraying gun will be more likely to become clogged, which is undesirable.

(C) The blending ratio of silica powder is (B) copper-based powder 100%
0.5 to 15 parts by weight, preferably 2 to 8 parts by weight
Parts by weight. If the amount is less than 0.5 parts by weight, it will not be possible to prevent the copper-based powder from settling, and if it exceeds 15 parts by weight, the electromagnetic shielding effect after applying the conductive paint will not only decrease, but also the viscosity of the paint will increase. This is undesirable because the workability of spraying deteriorates.

The anti-settling agent (D) used in the present invention is selected from acid salts of polyaminoamides, alkylamine salts of polycarboxylic acids, and aminosilanes.

A system consisting of one type or a mixture of two or more types, e.g.

A nti (crra P) manufactured by Babic Mallinckrodt
.

D 1sper byk, [) 1sper by
k i Q 1, Higashishi Silico-6026, 8H-602
0,B:il,=iii'#))j)5Z manufactured by John Co., Ltd.
-6050. S7-6023, 5t-1A-1100,
A-1120, Chisso APS-E, AAS-M (
All of the above are product names). These (D
) The blending ratio of the anti-settling agent is -(0.2 to 10 parts by weight, preferably 0.5 to 10 parts by weight, per 100 parts by weight of the (B) copper-based powder)
It is necessary to mix 6 parts by weight. The blending amount is 0.2
If it is less than 10 parts by weight, it will not be possible to prevent the settling of the copper-based powder, and if it exceeds 10 parts by weight, the conductivity after application of the conductive paint will be impaired, and the electromagnetic shielding effect will be reduced, and the viscosity of the paint will also increase, making it difficult to spray. is undesirable because it impairs workability.

The conductive paint of the present invention mainly contains a synthetic resin binder, copper-based powder, silica powder, and anti-settling agent, but if necessary, other additives may be added to the extent that the gist of the present invention is not impaired. You can also add This conductive paint is used in computers, electronic equipment, office machines, audio equipment, communication equipment,
It can be used for electromagnetic shielding of home appliances, V-game devices, etc.

[Effects of the invention] The conductive paint of the present invention has excellent electrical conductivity stability over time, and there is no sedimentation of copper-based powder (1), and even when the paint is diluted with a solvent, the sedimentation rate of copper-based powder is slow; A conductive paint with excellent workability and storage stability, such as not becoming a hard cake, could be obtained.

[Examples of the Invention] Next, Examples of the present invention will be described, but the present invention is not limited to these Examples.

Examples 1 to 4 The compositions shown in Table 1 were blended and mixed in a high shear mixer to produce conductive paints (■). Obtained paint (■)
Paint made by diluting 70 parts by weight with 30 parts by weight of toluene (■)
into a round color with a depth of 20cm and a diameter of 15cm.
The copper-based powder was poured to +n and left to measure the sedimentation property of the copper-based powder.
Further, this paint was spray coated onto a polyphenylene oxide resin plate having a thickness of 3 mm, and was dried at room temperature for 12 hours to form a coating film having a thickness of 50 μm. Regarding the conductivity of this coating film, the normal surface resistance and the temperature at -40℃ for 2 hours and 85℃
The surface resistance was tested after 10 cycles, with each cycle being 2 hours.

Furthermore, adhesion was tested by peeling off the base tape. These results are shown in Table 1, and it was recognized that the conductivity 1 of the present invention was excellent in all tests.

Comparative Examples 1 to 3 Conductive paints were produced by blending and mixing the compositions shown in Table 1 in the same manner as in Examples 1 to 4. Using this paint, sedimentation properties, conductivity, and adhesion were tested in the same manner as in the examples. The results are shown in Table 1 together with Examples.

Claims (1)

[Claims] 1 (A) synthetic resin binder, (B) copper-based powder, (C
1.) A conductive paint characterized by containing silica powder and (D) an anti-settling agent as main components. 2 (B) copper-based powder, (A) synthetic resin binder 10
The conductive paint according to claim 1, wherein the amount is 70 to 90 parts by weight relative to 30 parts by weight. 3 (C) silica powder, (B) copper-based powder 100 Shigehiro 7
The conductive paint according to claim 1 or 2, characterized in that the amount is 0.5 to 15 parts by weight. 4 (D) Claims characterized in that the anti-sedimentation agent is one or a mixture of two or more selected from acid salts of polyaminoamides, alkylamine salts of polycarboxylic acids, and aminosilanes. The conductive paint according to any one of items 1 to 3. 5. Claim #fJ Items 1 to 4, characterized in that (D) the anti-settling agent is present in an amount of 0.2 to 10 parts by weight per 100 parts by weight of the (B) copper-based powder. Any of the conductive paints described.