Compositions – Electrically conductive or emissive compositions – Free metal containing
Patent
1995-04-21
1996-10-22
McGinty, Douglas J.
Compositions
Electrically conductive or emissive compositions
Free metal containing
252512, H01B 116
Patent
active
055673570
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a conductive paint having a good adhesion to a molding of metallic oxide.
BACKGROUND ART
Moldings of metallic oxide, such as ITO (indium tin oxide) and IO (indium oxide), are widely used as transparent conductive films for electrodes in liquid crystal displays and solar batteries. In order to attach a lead to such a molding of metallic oxide, silver paste (paint in a paste form containing silver powder as main component) is generally used as a soldering electrode.
On the other hand, silver paste is not only expensive but usually contains epoxy resin as a binder in order to attain high adhesion to the molding of metallic oxide. Thus, good solderability and adhesion are achievable only if hardening conditions for the paste are controlled with high precision.
An object of this invention is to provide a conductive paint which satisfies the following requirements: conditions.
DISCLOSURE OF THE INVENTION
In order to achieve the above object, according to the present invention, there is provided a conductive paint having a good adhesion to a molding of metallic oxide, the conductive paint comprising 100 parts by weight of silver-plated copper powder containing silver plating in the amount of not more than 30 wt %; 13.6-6.0 parts by weight of phenolic resin (solid content); 0.2-0.7 part by weight of one selected from saturated fatty acids, unsaturated fatty acids, metallic salts thereof and coupling agents containing saturated fatty acids or unsaturated fatty acids; 1.0-4.0 parts by weight of triethanolamine; and 0.1-1.0 part by weight of dihydroxybenzene, following relations: substitution product, 2, 4-di substitution product, 2, 4, 6- tri substitution product, methylol group,
The aforementioned conductive paint is made by adding an appropriate amount of antifoamer and a solvent comprising butylcarbitol and acetylacetone in the weight ratio of 9.5/0.5-8.0/2.0 and kneaded together.
The conductive paint according to the present invention satisfies all of the above-noted requirements.
If the amount of the silver plating in the silver-plated copper powder exceeds 30 wt %, silver in the paint will migrate into or be taken or eaten by the solder because silver quickly diffuses into the solder during soldering.
If the content of the phenolic resin as a binder exceeds 13.6 wt %, the solderability will not be good. On the other hand, if it is less than 6.0 wt %, the silver-plated copper powder will not bind satisfactorily and the adhesion will worsen. With the ratio of silver-plated copper powder to binder, as the amount of the binder decreases, the adhesion to molding of metallic oxide will increase for a moment. This is considered to be due to the fact that the heat history during the heat hardening process is released by the increase in the ratio of the silver-plated copper powder. As for the transmittances of the phenolic resin defined in (A) to (D), see Unexamined Japanese Patent Publication No. 2-16172.
Saturated fatty acid may be palmitic acid, stearic acid or arachic acid having a carbon number of 16-20; unsaturated fatty acid may be palmitoleic acid, oleic acid or linolenic acid having a carbon number of 16-18; metallic salt thereof may be salts combined with metal such as sodium, potassium, copper, aluminum or zinc. Coupling agents containing saturated fatty acid or unsaturated fatty acid may be isopropyl tristearoyl titanate, isopropyl trioctanol titanate or isopropyl dimethacryl isostearoyl titanate.
These dispersants are added for better dispersion of the silver-plated copper powder. But if it exceeds the upper limit, the adhesion of paint to ITO or IO will be poor. On the other hand, if it is below the lower limit, the dispersion will worsen, thereby lowering the solderability.
Triethanolamine is added to improve the adhesion of molding of metallic oxide to ITO or IO. Considering the solderability, 2.5 parts by weight of triethanolamine will be most appropriate. If its content exceeds the upper limit, the solderability will decrease. If it is below the lower l
REFERENCES:
patent: 4387115 (1983-06-01), Kitamura et al.
patent: 5242511 (1993-09-01), Yokoyama et al.
patent: 5372749 (1994-12-01), Li et al.
McGinty Douglas J.
Tatsuta Electric Wire & Cable Co., Ltd.
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