JPH056592B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an excellent copper-based conductive coating composition that exhibits little reduction in conductivity and little occurrence of patina even under various environmental conditions. [Prior art] Conductive paint is made by mixing conductive filler powder (for example, fine metal powder such as gold, silver, copper, nickel, molybdenum, tungsten, etc., fine carbon powder such as carbon black, graphite, etc.) with polyphenyl ether-based paint. It is dispersed in a solution of thermoplastic resin such as acrylic or cellulose, or thermosetting resin such as epoxy or phenol, and is used for circuit pastes, conductive adhesives, electromagnetic shielding agents, etc. Used for many purposes. Among the above-mentioned various conductive fillers, powders of noble metals such as gold and silver are expensive, so they are only used in conductive paints for special purposes. In addition, metal powders and carbon powders other than nickel powder have poor conductivity or long-lasting conductivity, so nickel powder is often used as a conductive filler for conductive paints, mainly for shielding. There is. In recent years, with the rapid spread of electronic devices, electromagnetic interference (EMI.
Interference) has become a problem, but
A technology has been developed that can solve this EMI by applying conductive paint, and it has come to be known as the so-called EMI shielding technology, and conductive paint has come to be used in large quantities in this field. [Problems with the prior art] Conductive paints containing copper powder from which the surface oxidation layer has been removed as a conductive filler have better initial film performance than conductive paints using nickel powder, but have poor heat resistance. It has not been put into practical use because it has poor properties and moisture resistance, and its conductivity rapidly decreases during use. Copper powder is cheaper than nickel powder, and copper has about 4 times higher electrical conductivity than nickel on a base metal basis, so if copper powder oxidation prevention technology is established, copper powder can be replaced with nickel powder. It should be possible to use a large amount of it as a conductive filler in conductive paints instead of. In other words, the surface of commercially available copper powder is already oxidized at the stage of purchase, and it does not show conductivity even if it is directly dispersed in a paint base material. When dispersed in a paint base material, it exhibits excellent conductivity as described above at the initial stage, but as oxidation progresses, the conductivity of the paint film gradually decreases, and in some cases, it loses its conductivity completely after a few days. I'll get lost. However, if technology for preventing oxidation of copper powder was established, it would be possible to advantageously supply conductive paints using copper powder as a conductive filler at low cost. Various proposals have already been made. Regarding anti-oxidation technology for copper powder in this type of conductive paint, for example, those using phosphorous acid and its derivatives, those using anthracene derivatives, those using formaldehyde resin, and those using hydroxyphenol derivatives (hydroquinone, catechol, etc.) Various proposals have been made, such as using an organic acid and a rosin-based substance together, using an organic titanate, and using an organic titanium compound and a phenol-based compound together. However, these proposals have little or no effect or
Even if they are somewhat effective, they are in no way comparable to paints using nickel powder or silver powder, and the common drawback in all cases is that, to varying degrees, the paint paste or its coating develops a patina. This is remarkable. [Problems to be Solved by the Invention] The present inventors have conducted intensive research to improve the above-mentioned drawback of generation of patina in conductive paints using copper powder as a conductive filler, and as a result, reduction weight loss has been achieved. Copper powder containing 0.2% or less, or copper powder treated with organic carboxylic acid to remove the surface oxidation layer, is dispersed in a paint binder resin together with a specific antioxidant.The paint has excellent storage stability, moisture resistance, We learned that it has excellent heat resistance and heat cycle resistance, and that there is very little patina on paints and coatings.As a result, the coatings exhibit excellent electrical conductivity for long periods of time under various environmental conditions, and we developed this book. The invention was achieved. [Specific means for solving the problems] The copper-based conductive coating composition of the present invention has (A) reduction weight loss.
Copper powder of 0.2% or less or copper powder treated with organic carboxylic acid to remove the surface oxidation layer, (B) Binder resin for paint, and (C) General formula () [In the formula, Y is a hydroxyl group, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a halogen atom, and a is 1 to
The number is 3. ] It is made by containing the triazoles shown below as an antioxidant. The copper powder with a reduction loss of 0.2% or less (JSPM standard 3-63) used in the present invention and the copper powder used as the raw material for organic carboxylic acid treatment have no particular restrictions on their manufacturing method, and may be obtained by electrolysis, Those obtained by a spraying method, those obtained by a grinding method, those obtained by a reduction method, etc. can all be used. and,
The particle size of the copper powder is preferably 100μ or less. especially,
From the viewpoint of paintability, etc., it is preferable to use resin in which particles of 325 mesh or less account for 80% or more. It is also possible to use a combination of two or more types of copper powder obtained by different manufacturing methods. In the present invention, the copper powder treated with organic carboxylic acid has a reduction loss of 0.2
% or more of copper powder. Examples of organic carboxylic acids used to remove the surface oxidation layer of copper powder in the present invention include acetic acid,
Monocarboxylic acids such as propionic acid, succinic acid,
Polycarboxylic acids without substituents such as tricarballylic acid, lactic acid, tartaric acid, glyceric acid, malic acid,
citric acid, gluconic acid, tropic acid, benzylic acid,
Examples include hydroxycarboxylic acids such as mandelic acid, atrolactic acid, and glycolic acid. Particularly preferred among these organic carboxylic acids are hydroxycarboxylic acids. The surface oxidation layer of the copper powder can be easily removed by adding the copper powder to a solution of these organic carboxylic acids in a suitable solvent, immersing it for a certain period of time, and leaving it to stand or stirring it. Examples of the solvent for dissolving the organic carboxylic acid include water and various organic solvents, but water and alcohols such as methanol, ethanol, and propanol are preferred from the standpoint of their ability to solvate copper ions.
The copper powder treated with the organic carboxylic acid is filtered, washed with water or alcohol, and dried. The thus obtained copper powder treated with an organic carboxylic acid to remove the surface oxidation layer (hereinafter sometimes referred to as "organic carboxylic acid treated copper powder") or the copper powder with a reduction loss of 0.2% or less is used in the present invention. It is blended into the conductive paint composition, but the blending ratio is 10% to the paint composition.
~90% by weight, preferably 30-70% by weight. Note that instead of the organic carboxylic acid treatment of the present invention,
When copper powder is treated with an aqueous mineral acid solution to remove the oxidized layer, the treated copper powder can be used in combination with the same antioxidant as in the present invention to make a conductive paint, and the resulting paint has initial conductivity. The anti-oxidation properties are significantly inferior to those that do not express or are treated with an organic carboxylic acid. Next, an antioxidant (C) is blended into the conductive coating composition of the present invention, and the antioxidant is a triazole represented by the above formula (). Such triazoles include those in which Y is a hydrogen atom [3-(N-salicyloyl)amino-1,
2,4-triazole] was produced by Adeka Argus Chemical Co., Ltd. as MARK CDA-1 and MARK CDA.
Since it is commercially available under the trade name -1M, such a commercial product can be used as appropriate. The blending ratio of the antioxidant in the copper-based conductive coating composition of the present invention varies depending on the type of antioxidant and the application of the coating composition, but the reduction loss is 0.2
% or less of copper powder or organic carboxylic acid treated copper powder, usually 0.01 to 5% by weight, preferably 0.1 to 2%
Within the range of % by weight. The coating composition of the present invention can be obtained by mixing and dispersing the above-mentioned copper powder having a reduction loss of 0.2% or less or organic carboxylic acid-treated copper powder and an antioxidant in a predetermined ratio in a suitable coating binder resin. but,
As the paint binder resin, all common paint binder resins can be used. For example, thermoplastic resins such as acrylic, vinyl, cellulose, and vinyl chloride/vinyl acetate copolymer systems; thermosetting resins such as epoxy, urethane, thermosetting acrylic, phenolic, melamine, and alkyd systems. Compatible resins can be used. These binder resins can also be used in combination of two or more types, if necessary. A suitable organic solvent is usually used in combination with these paint binder resins, especially when the viscosity of the resin itself is high. The organic solvent varies depending on the type of binder resin, but examples of organic solvents include aromatic hydrocarbons such as toluene and xylene; alcohols such as isopropanol and butanol; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. esters such as ethyl acetate and butyl acetate; and cellosolves such as ethyl cellosolve and butyl cellosolve. Depending on the type of binder resin, one type of organic solvent may be used alone, or two or more types may be used in combination as appropriate. If the object to be coated is plastic or the like, consideration must be given to selecting a solvent that will not dissolve the object to be coated. Types of the conductive coating composition of the present invention include:
For example, a one-component quick-drying type using thermoplastic acrylic resin or the like as a binder resin, or a two-component type using urethane resin or epoxy resin, etc. may be used as appropriate depending on the situation. can. The blending ratio of each component in the preparation of the conductive coating composition of the present invention is desirably selected so that the electrical conductivity of the coating film is maximized and the electrical conductivity is maintained for a long period of time. For example, typical blending ratio ranges for conductive paints used for spray painting and brush painting are as follows. Binder resin 5-20% by weight Copper powder with reduction loss of 0.2% or less or copper powder treated with organic carboxylic acid 40-60% by weight Antioxidant 0.01-5% by weight Solvent 20-55 In the conductive coating composition of the present invention In addition to the above-mentioned components, various additives can be added as necessary. Especially to prevent settling of copper powder.
It is desirable to incorporate various anti-settling agents, such as thickeners or thixotropic agents, within a range that does not interfere with conductivity. Such anti-settling agents include:
For example, hydrogenated castor-free, metal soap, aluminum chelate, organic bentonite, colloidal silica, oxidized polyethylene wax, long-chain polyaminoamide, polycarboxylic acid alkylamine, etc. are used alone. It is also possible to use two or more types in combination. Particularly preferred antisettling agents have the general formula RCONH ₂
or (RCONH) ₂ A (in each formula, R has 5 to 21 carbon atoms
In the alkyl group, A is an alkylene group having 1 to 6 carbon atoms. ) and composites of such aliphatic amides and waxes.
Specific examples of the aliphatic amides include monoamides such as oleic acid amide, caproic acid amide, linoleic acid amide, and behenic acid amide, N,N'-methylenebisstearic acid amide, and N,N'-ethylenebisstearic acid amide. Bisamides such as In addition, as a compound of aliphatic amides and wax, the above bisamides and molecular weight
Examples include composites obtained by co-pulverization with polyolefin waxes of 1,000 to 9,000 (Japanese Patent Application Laid-open No.
-Refer to Publication No. 65056). The conductive coating composition of the present invention may further contain a leveling agent (eg, silicone, high-boiling ketone, etc.), a surfactant, a flame retardant, and the like, if necessary. In addition, antioxidants disclosed in Japanese Patent Application No. 107518/1983, such as phosphoric acid esters,
Phosphathiazine derivatives, alkylimidazoles, organic carboxylic acid salts of alkylimidazoles, nitrogen-based silane coupling agents, sulfur-based silane coupling agents, phenothiazine, thionine, stearylpropylenediamine, etc. are represented by the preceding formula (). It may be used in combination with triazoles. The conductive coating composition of the present invention is prepared by appropriately mixing the above-mentioned binder resin, organic carboxylic acid-treated copper powder, antioxidant, solvent, and various additives blended as necessary. It may be made into a paint using a dispersing device (for example, a disper, a ball mill, a sand mill, a three-roll mill, a Huber muller, etc.) used in the preparation. The electrically conductive composition of the present invention obtained in this way has extremely high electrical conductivity when coated or printed on an object by an appropriate method such as spraying, brushing, dipping, offset printing, or screen printing. Moreover, even under various environmental conditions, an excellent conductive coating film with little decrease in conductivity or occurrence of patina can be obtained. The following is a more detailed explanation of Examples and Comparative Examples. "Parts" in these examples means parts by weight, and "%" means % by weight. Moreover, the volume resistivity described in these examples was measured by the following method. That is, as shown in the attached drawing, a plastic board (glass fiber reinforced epoxy resin laminate) 1
Etch and remove the copper foil in the center part 4 of a copper-clad laminate with a width of 5 cm x length of 10 cm, and leave copper foil parts 2 and 2 with a width of 1.5 cm at both ends of the plastic board 1. board A (both copper foil parts 2 and 2 of board A)
The distance between them is 7cm. ), and on this board A,
After applying the conductive paint to a width of 1 cm and leaving the resulting coating film 3 under various environmental conditions for a predetermined period of time, the thickness of the coating film was measured using a digital micrometer (Digimatic Indicator 543 manufactured by Mitoyo Seisakusho Co., Ltd.). Further, the electrical resistance was measured with a Wheatstone bridge (type 2755 manufactured by Yokogawa Electric Corporation), and the volume resistivity was calculated using the following formula. Volume resistivity (Ω cm) = Measured resistance value (Ω) x Thickness (cm
) × Width (cm) / Length (cm) = Measured resistance value × Thickness / 7 Example 1 Commercially available industrial electrolytic copper powder (325 mesh passing 90%
400 parts of a 10% citric acid aqueous solution was added to 100 parts (reduction loss 0.23%), and after stirring with a stirrer for 15 hours, the copper powder was separated by filtration, thoroughly washed with water, and dried. For 100 parts of the obtained copper powder, 1 part of 3-(N-salicyloyl)amino-1,2,4-triazole (MARK CDA-1 manufactured by Adeka Argus Chemical Co., Ltd.)
40% toluene solution of commercially available polymethyl methacrylate (reagent manufactured by Wako Pure Chemical Industries, molecular weight approximately 100,000)
100 parts and 60 parts of methyl ethyl ketone were added, and high-speed dispersion was performed to obtain a conductive paint. This paint was applied on the substrate A shown in the attached drawing as described above, and after being left at 23°C and 50% RH for 24 hours, the volume resistivity was measured.
It was 7.4×10 ^-4 Ω・cm. In addition, this coating film is 85
When the volume resistivity was measured after being left in heated air at ℃ for 1000 hours, it was 7.8×10 ^-4 Ω·cm.
In addition, as a result of examining the development of patina after leaving the paint film of this paint and the paint solution itself in the air at room temperature for 1000 hours, as shown in Table 1, no patina was observed in both the paint film and the paint. Nakatsuta. Also, 23
After storage in a sealed container at 50 RH% for 1000 hours, a similar resistance measurement was performed on the sample prepared on substrate A, and as shown in Table 1, almost no change was observed. Example 2 3-(N-salicyloyl)amino-
1 part of 1,2,4-triazole (Adeka Argus Chemical product name: MARK CDA-1M), acrylic resin (product name of Mitsubishi Rayon Co., Ltd., Product Dianal BR-)
100 parts of a 40% toluene solution of 102), 60 parts of methyl ethyl ketone, and 2 parts of Ceridust 9615A (trade name of amide-modified wax manufactured by Hoechst) were added and dispersed at high speed to obtain a conductive paint. This paint was applied in the same manner as in Example 1, and the volume resistivity after being left for 24 hours was 8.1×10 ^-4 Ω・cm,
After being left for 1000 hours, the resistance was 8.6×10 ^-4 Ω・cm. Table 1 shows the development of patina after the paint film and paint solution of this paint were left for 1000 hours in the same manner as in Example 1, and the resistance value after being stored in a sealed container at 23°C and 50% RH for 1000 hours. It was as shown. Comparative Examples 1-2 3-(N-salicyloyl)amino-1,2,4-triazole (MARK
A conductive paint was produced in the same manner as in Example 1 except that CDA-1) was not blended at all (Comparative Example 1). In addition, instead of the citric acid-treated copper powder in Example 1, the industrial electrolytic copper powder used in Example 1 was used as it was, and 3-(N-salicyloyl)amino-1,2,4-triazole was not used at all. without blending,
A conductive paint was otherwise produced in the same manner as in Example 1 (Comparative Example 2). Each of the obtained paints was tested for volume resistivity, development of patina, and storage stability in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 3 100 parts of a 5% hydrochloric acid aqueous solution was added to 100 parts of the same commercially available industrial electrolytic copper powder used in Example 1, and the mixture was stirred for 15 hours using a stirrer. After washing with water, it was centrifuged and dried. Instead of the citric acid-treated copper powder in Example 1,
This hydrochloric acid-treated copper powder was used, and the rest was Example 1.
A conductive paint was obtained in the same manner as in . The initial volume resistivity of this paint film is 2.5×10 ^-3 Ω・
cm, but after being left in air at 85°C for 1000 hours, its resistivity became 1.7×10 ^-2 Ω・cm, about 10 times higher, and as shown in Table 1, the coating film and paint solution There was a significant amount of patina inside, and the storage stability was also poor. Example 3 A conductive paint was obtained in the same manner as in Example 1 except that the succinic acid aqueous solution treatment was performed instead of the citric acid aqueous solution treatment. The obtained paint was subjected to the same test as in Example 1, and the results were as shown in Table 1. Example 4 A conductive paint was prepared in the same manner as in Example 1, except that acetic acid aqueous solution treatment was performed instead of citric acid aqueous solution treatment. The obtained paint was subjected to the same test as in Example 1, and the results were as shown in Table 1.

[Table] As is clear from the comparison between the Examples and Comparative Examples above, the paints of each Example have excellent conductivity, and even under various environmental conditions, there is little decrease in conductivity and little occurrence of patina.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a partially copper-clad laminated board A used for measuring the volume resistivity of a paint film, where 1 shows the plastic substrate, 2 shows the copper foil portion, and 3 shows the paint film.

Claims (1)

[Scope of Claims] 1 (A) Copper powder with reduction loss of 0.2% or less or copper powder treated with organic carboxylic acid to remove the surface oxidation layer, (B) Binder resin for paint, and (C) General formula [In the formula, Y is a hydroxyl group, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a halogen atom, and a is 1 to
3] A copper-based conductive coating composition containing a triazole represented by the following. 2. The copper-based conductive coating composition according to claim 1, wherein the component (C) is 3-(N-salicyloyl)amino-1,2,4-triazole.