JPS62292870A - Electrically conductive paint - Google Patents

Abstract

PURPOSE:To provide an electrically conductive paint having stable electrical conductivity, consisting of a specified 2-substd.-4,6-dithiol-sym-triazine derivative, ascorbic acid, copper powder, a synthetic resin and silica powder. CONSTITUTION:100pts.wt. copper powder having an average particle size of not larger than 100mu is blended with 0.01-5.0pts.wt. 2-substd.-4,6-dithiol-sym- triazine derivative of formula I (wherein R<1> is NHR<1>', NR<1>', R<1>'' or OR<1>''; R<1>' and R<1>'' are each H, a 1-18C alkyl, an alkylene, an aryl, an arylalkyl, an alkylaryl or an alkylene-aryl; M<1> and M<2> are each H, an alkali metal or 1/2 atom of an alkaline earth metal), 0.005-7.0pts.wt. ascorbic acid of formula II, 0.5-15pts.wt. silica powder and 2-20wt% (based on the amount of copper powder) synthetic resin (e.g., PS). The mixture is dissolved or dispersed in an org. solvent in which said resin is soluble.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a stable electrically conductive paint having a stable organic film formed on the surface of copper powder.

(Conventional technology) In recent years, technology in ICs, LSIs, etc. has made remarkable progress, and high density and high performance have become commonplace.
SI is used. However, since high-frequency pulses are generated from highly functional electronic devices, surrounding computers, televisions, radios, etc. are often affected by the high-frequency pulses, causing them to malfunction. This phenomenon is
Another factor is the shift to plastic housings for electronic equipment instead of metal housings to reduce weight.

Conventional metal housings have the function of shielding electromagnetic waves such as high-frequency pulses generated by the device itself, and also have the function of shielding electromagnetic waves that enter the device from the outside. As a result, plastic housing equipment, which has become lighter in size, is vulnerable to electromagnetic waves. In order to cope with the electromagnetic environment that is worsening year by year, laws in the United States, West Germany, and other countries have already made it mandatory for electronic devices to be shielded from electromagnetic waves. Similar legislation is being discussed in Japan as well. Under these circumstances, many useful techniques for shielding electromagnetic waves in the field of electronic equipment and materials have been developed.

As a method for shielding pulses generated from electronic equipment, it is necessary to combine components that generate as little noise as possible, and various ideas have been devised. In particular, methods for countermeasures at the circuit design stage are emphasized,
One way to take measures against cables and housings is to return plastic housings to conventional metal housings, but in reality, from the design and functional standpoints of the housings, it is difficult to replace them with metal housings. It is difficult to transition to manufacturing. Therefore, it has been established as one technique to provide a plastic housing with s z 711 capability to shield noise. Various methods have been used to do this, such as forming a conductive film by zinc spraying and plating, but it is relatively easy to coat the housing with nickel conductive paint in terms of productivity and cost. This method is becoming almost mainstream.

On the other hand, the method of kneading conductive filler into resin and molding the housing by injection molding is also progressing rapidly. Among these, in the field of conductive paints, strong efforts are being made to develop copper-based paints that have higher shielding properties and lower cost i than nickel-based paints.

However, since copper is a metal that easily oxidizes, stabilization treatment of copper has become an important technology. For example, Tokkosho,
There is a method of forming a plating film of silver or the like on the surface of copper powder, as disclosed in Japanese Patent No. 17-3019, but this method has the disadvantage of being expensive because it is difficult to coat. Also, U.S. Patent No. 43058
Although the method of forming a pyrophosphite-based ditanate film on a copper surface as in No. 47 is effective in a three-thermal environment, it is insufficient in a humid environment and a salt spray environment.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and uses relatively inexpensive copper powder to coat the surface of the copper powder. +! ! Forms a film and stabilizes iI! The purpose of this invention is to provide a coating material that is electrically conductive.

[Structure 1 of the Invention (Means and Effects for Solving the Problems) As a result of extensive research to achieve the above object, the present inventor has discovered that copper powder is 2-substituted-4,6-dithiol-Sl. If ascorbic acid and its optical isomers or derivatives having reducing properties are used in combination with /l-triazine derivatives, it will effectively stabilize the copper powder surface without impairing the ♂′A conductivity of the copper powder. The present invention was completed based on the discovery that a suitable organic film could be formed. That is, the present invention provides (A) a 2-substituted-4,0-dithiol-sym-triazine derivative represented by the general formula (I), (wherein R1 is NHR'', NR'', R1'', O
R1' or SR'', where R1' or R1'' is a hydrogen atom or an alkyl group consisting of 1=18 carbon atoms;
Indicates an alkylene group, aryl group, arylalkyl group, alkylaryl group or alkylenearyl group,
Ml or M2 represents a hydrogen atom, an alkali metal atom, or 1/2 atom of an alkaline earth metal> (B) Ascorbic acid (C) Copper powder with an average particle size of 100 μm or less (D>Synthetic resin and (E) Silica powder It is an inductive paint characterized by containing.

(A) 2-U-substituted-4,6-dithiol used in the present invention
As the sym-triazine+6 body, for example, 2-methylamino-4,6-dithiol-sym-triazine, 2
-ethylamino-4,6-dithiol-sy+n-triazine, 2-amino-4,6-dithiol-sy+o-1-riazine, 2-butylamino-4,6-dithiol-sy
m-triazine, 2-butylamino-4,6-dithiol-Sl/m-triazine monosodium, 2-octylamino-4,6-dithiol-sym-
1 heliazine 1/2 calcium, 2-octadecyl-4,6-dithiol-sym-triazine, 2-diethylamino-4,6-dithiol-syn+
-triazine, 2-diethylamino -4,6-dithiol-Sy
Triazine monosodium, 2-didodecylamino-4,6-dithiol-sym
-triazine, 2-benzylamino-4,6-dithiol-sym-t
-Ryazine monocalcium, 2-7enylamino-4,6-dithio-3-2-diphenylamino-4,6-dithiol-sym-triazine.

2-naphthylamino-4,6-dithiol-5yIIl
-triazine, 2-naphthylamino -4,6-dithiol-sym-
triazine 7nona[-lium, 2-morpholino-4,6-dithiol-sy+++-
t-Ryazine, 2-cyclohexyl-4,6-dithiol-sym-triazine monosodium, 2-cyclohexylamino-4,6-dithiol-5
yIll-triazine monosodium, 2-(β-carboxyl)ethylamino-4,6-dithiol-sym-triazine, 2-(ρ-carboxyl)phenylamino-4.6-
Dithiol-S1 phthotriazine, 2-methoxy-4,6-dithiol-sym- triazine, 2-phenoxy-4,6-dithiol-sym-
l-Ryazine, 2-naphthoxy-4,6-dithiol-sym-triazine, 2-thiobenzyloxy-4
, 6-dithiol-sym triazine, 2-thiobutyl-4,6-dithiol-sym- 1-
Examples include riazine, which may be used alone or in combination of two or more silicones. The blending ratio of the 2-substituted-4,6-dithiol-sy+o triazine derivative is 1 part of the copper powder
It is preferable to mix 0.01 to 5.0 parts by weight with respect to 00 parts by weight. If it is less than 0.01 part by weight, a film that exhibits sufficient antirust ability will not be formed on the surface of the copper powder, and 5.
If the amount exceeds 0 parts by weight, the conductivity tends to be impaired, which is not preferable.

The ascorbic acid (B) used in the present invention is a strongly reducing compound represented by the following general formula (II) and has an enediol group represented by monoascorgonic acid, CH20f-1 -C-OH Its optical isomer erythorbic acid is a similar reducing compound. In addition, ascorbic acid derivatives that have lower reducing properties include ether derivatives such as 5-0-methylalcorbic acid, phosphoric acid esters such as ascorbic acid-6-phosphoric acid, ascorbic acid-6-sulfuric acid, etc. Organic acid esters such as sulfuric acid ester and 6-0-7 cetyl ascorbic acid can be mentioned.

Amine derivatives such as scorbamic acid are also effective.

Additionally, the natural copper enzyme ascorbate oxidase can also be used as an effective reducing agent. These ascorbic acids can be used alone or in combination of 2 or more.

The blending ratio of ascorbic acid is copper powder 1001 ffi
It is preferable to add 0.005 to 7.0 parts by weight. When the blending amount is 0,005ffl ω, the reducing action that brings out sufficient rust prevention power is small in the ungrooved area, and when the amount is 7,0ff
If it exceeds 1 part lff, the conductivity tends to be impaired, which is not preferable. The ascorbic acid treatment can be blended in combination with the above-mentioned 2-substituted-4,6-dithiol-5yl-triazine derivative during paint production. Further, it is preferable to process the copper powder by dissolving it in a mixed solvent such as alcohol/toluene in advance.

As the copper powder (C) having an average particle size of 100 μm or less used in the present invention, a wide variety of commercially available copper powders can be used as long as the average particle size is 100 μm or less. If the average particle size exceeds 100 μm, the surface of the coating film will be rough and a dense coating structure will not be obtained when mixed into a paint, which is not preferable. Preferably, copper powder has an average particle size of 3 to 40 μm.

The synthetic resin (D) used in the present invention includes a wide range of thermoplastic and thermosetting synthetic resins, and these are used as binders. Thermoplastic synthetic resins include acrylic resins, styrene resins, vinyl resins, alkyd resins, hydrocarbon resins, polyester resins, etc., and thermosetting synthetic resins include epoxy resins, urethane resins,
Examples include alkyd resins and unsaturated polyester resins, and these can be used alone or in combination of two or more. These resins are preferably liquid substances, and if they are solid themselves, they are used after being dissolved in an appropriate organic solvent.

As the silica powder (E) used in the present invention, commercially available silica powder is used. Usually, during storage of paint, copper powder settles and forms a hard cake, which solidifies over a long period of time and may not be usable as paint. Silica powder is added to float the copper powder and prevent this hard cake from forming. The blending ratio of silica powder is preferably 0.5 to 15 parts by weight per 100 parts by weight of copper powder. If the proportion m is less than 0.5 parts by weight, it is impossible to prevent the copper powder from settling, and if it exceeds 15 parts by weight, the viscosity of the coating material increases significantly, resulting in poor workability, which is not preferable.

In the present invention, an organic solvent capable of dissolving the synthetic resin used as a binder is selected and used. This solvent is used to adjust the viscosity of the paint and improve workability. Examples of the solvent include aromatic hydrocarbons, fatty acid hydrocarbons, ketones, esters, alcohols, etc., and these may be used alone or in combination of two or more.

The conductive paint of the present invention comprises (A) 2-substituted-4,6-dithiol-sym-i-lyazine derivative, (B) ascorbic acid, (C) copper powder, <D) synthetic resin, (E) silica It can be easily produced by mixing and stirring a powder and an organic solvent using a known method. In addition, other components may be added and blended as necessary, as long as they do not contradict the purpose of the present invention.

The conductive paint thus produced is used by coating the housing of an electronic device or the like.

(Examples) Next, the present invention will be explained by examples, but the present invention is not limited to the following examples.

In the following examples and comparative examples, "part" means "medium part"
means.

Example 1 2-butylamino-4,6-dithiol-sym-1
- Electrolytic copper powder 1 with an average particle size of 7 μm is added to a solution of 0.35 parts of riazine and 0.07 parts of ascorbic acid dissolved in a mixed solvent of ethyl alcohol/isopropyl alcohol.
00 parts were added with stirring and stirred for 30 minutes, and then the mixed preparation was removed and treated under reduced pressure to obtain copper powder. To this copper powder, 40 parts of polymethylnuclear acrylate/butyl methacrylate copolymer, acryloid B-66 (manufactured by Rohm and Haas, trade name) and 225 parts of toluene were added, stirred and mixed uniformly, and silica powder Aerosil was added. #
Add 5 parts of 300 (manufactured by Nippon Aerosil Co., Ltd., trade name) and 1
A conductive paint was prepared by stirring and mixing for hours. This paint was applied to an ABS base material in an amount of 40 parts m (dry film thickness).
Determine the volume resistivity of the conductive coating film over time;
After conducting a 24-hour hot water spray test under the conditions of No. 15-Z-2371, the coating film appearance and volume resistivity were evaluated and the results are shown in Table 1, confirming the effects of the present invention.

Example 2 Polymethyl methacrylate, 35 parts of acryloid A-11 (manufactured by Rohm and Haas, trade name) and cellulose acetate butyrate CAB381-0.5 (gose 1-
Manufactured by Mankodatsu 9, product name) 5 copies! - 0.5 part of 2-octylamino-4,6-dithiol-sym-triazine, 0.1 part of L-ascorbic acid, and 0.002 parts of ascorbic acid oxidase are dissolved in 200 parts of toluene and 10 parts of ethanol and stirred. 1 part was dissolved in 5 parts of a mixed solvent of toluene/isopropyl alcohol/ethanol, and then 100 parts of electrolytic copper powder with an average particle size of 10 μm was added.
Stir and mix for hours.

Next, 3 parts of silica powder Aerosil #200 (manufactured by Nippon Aerosil Co., Ltd., trade name) was added and mixed with stirring for 1 hour to prepare a conductive paint. A conductive coating film was formed on this paint in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1, and the effects of the present invention were observed.

Example 3 Bisphenol A liquid epoxy resin Epicoat 828
(manufactured by Yuka Shell Epoxy Co., Ltd., trade name) 45 parts, 2.3 parts of dicyandiamide, imidasol, 1 body, 2 parts of curesol
1.1 parts of E4MZ (manufactured by Shikoku Kasei Co., Ltd., trade name) and 50 parts of methyl edyl ketone were added and stirred uniformly. Then 2-hexylamino-4,6-dithiol-sym-
1.5 parts of triazine and 2.0 parts of ascorbin Fi were mixed together, stirred thoroughly, and then 100 parts of electrolytic copper powder with an average particle size of 5 μm was added and stirred uniformly. , product name) 1
．． After adding 0 parts, the mixture was passed through a triple roll twice and mixed to prepare a conductive paint. This paint was applied to an unsaturated polyester resin base material and dried at 85°C for 150 minutes to a dry film thickness of 4.
A conductive coating film of 0 μm was obtained. The evaluation of coating density was carried out in the same manner as in Example 1, and the results are shown in Table 1, and the effects of the present invention were confirmed.

Comparative Example 1 All the procedures were the same as in Example 1 except that 2-butylamino-4,6-dithiol-Sytodriazine and L-7 scorbic acid were removed and untreated electrolytic copper powder was used. We created conductive paint and conducted the same evaluation.
The results are shown in Table 1.

Comparative Example 2 Same as Example 1 except that 0.001 part of L-ascorbic acid was added, and conductive property r1
The same evaluation was carried out and the results are shown in Table 1.

Comparative Example 3 A conductive paint was prepared in the same manner as in Example 1 except that 0.001 part of 2-butylamino-4,6-dithiol-sym-triazine was added, and the same evaluation was conducted. The results are shown in Table 1.

[Effects of the Invention] As is clear from the above explanation and Table 1, the conductive paint of the present invention has 2-substituted-4,6-dithyA-Rusy+
By using n-triazine derivatives and ascorbic acid, a stable structured film is formed on the surface of copper powder, which is an electrically conductive material, and this paint provides stable electrical conductivity and electromagnetic shielding effect, preventing electromagnetic waves from electronic devices, etc. It is suitable for shielding.

Claims (1)

[Claims] 1(A) A 2-substituted-4,6-dithiol-sym-triazine derivative represented by the general formula (I), ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) ( However, in the formula, R^1 is NHR^1', NR^1', R^
1″, represents OR^1’ or SR^1’, where R^
1' or R^1'' represents a hydrogen atom or an alkyl group, alkylene group, aryl group, arylalkyl group, alkylaryl group or alkylenearyl group consisting of a hydrogen atom or carbon atoms of 1 to 18, and M^1 or M^2 is 1/2 atom of hydrogen atom, alkali metal atom or alkaline earth metal) (B) ascorbic acid (C) copper powder with an average particle size of 100 μm or less (D) synthetic resin and (E) silica powder. Characteristic conductive paint. 2-Substituted-4,6-dithiol-sym-triazine derivative of 2(A) is added in an amount of 0.01 to 5.0 parts by weight per 100 parts by weight of copper powder of (C). The conductive paint according to claim 1, which is blended in the ratio of 0.005 to 7.0 parts by weight of ascorbic acid (3) (B) to 100 parts by weight of the copper powder (C). The conductive paint according to claim 1 or 2 to be blended.The blending ratio of the copper powder of 4(C) and the synthetic resin of (D) [(C
)/(D)] is 2 to 20 (weight ratio), the conductive paint according to any one of claims 1 to 3. The conductivity according to any one of claims 1 to 4, wherein the silica powder (E) is blended in a proportion of 0.5 to 15 parts by weight per 100 parts by weight of the copper powder (C). paint.