Method for producing metal particle dispersion, conductive ink using metal particle dispersion produced by such method, and conductive coating film

Abstract

Disclosed is a method for producing a metal particle dispersion wherein a metal compound is reduced by using carbodihydrazide represented by the formula (1) below or a polybasic acid polyhydrazide represented by the formula (2) below (wherein R represents an n-valent polybasic acid residue) in a liquid medium. By reducing the metal compound in the presence of a compound having a function preventing discoloration of the metal, there can be obtained a metal particle dispersion having excellent discoloration preventing properties. Metal particles produced by such methods have a uniform particle diameter and are excellent in dispersion stability. By using a conductive resin composition or conductive ink containing a metal particle dispersion obtained by such production methods, there can be formed a conductive coating film, such as a conductive circuit or an electromagnetic shielding layer, having good characteristics.

Description

technical field [0001] The present invention relates to a method for producing a metal particle dispersion useful as a raw material for conductive ink, a conductive ink containing the metal particle dispersion produced by the method, a conductive resin composition, and a conductive resin composition using the conductive ink. Conductive film formed with conductive ink or conductive resin composition. Background technique [0002] Conventionally, conductive pastes (conductive resin compositions such as conductive inks, conductive paints, and conductive adhesives) have been widely used to form electrodes and conductive circuit patterns on substrates of printed wiring boards. Recently, a conductive paste is used to form not only a printed circuit board but also an IC tag, a circuit pattern for electromagnetic wave shielding, and the like. The conductive paste is a material in which conductive powder or metal particles are dispersed in a resin component, an organic solvent, or t...

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Problems solved by technology

[0007] For example, there is a method of using a high-molecular-weight pigment dispersant as a protective agent, mixing a non-aqueous solvent with water, reducing it with an amine, and then extracting the metal into the non-aqueous solvent to obtain fine metal particles (for example, refer to Citation 3). , but in this method, due to the use of high molecular weight pigment dispersants with high pyrolysis temperature, it is difficult to sinter at low temperature

Therefore, there is also a method of lowering the pyrolysis temperature of the protective agent by adding an amine compound such as octylamine as a protective agent and coexisting an acidic decomposing agent in the synthesis by the gas phase method, but even this method requires It is difficult to form a circuit on the plastic film by heating for a long time above 200°C

Moreover, since the gas phase method is used, there is a problem of disadvantageous cost

[0008] Furthermore, in recent years, it has also been reported that a metal compound of a fatty acid with a short carbon number or a metal complex of an amine is added as a protective agent for metal fine particles, and a method of forming a circuit is sintered at a low temperature (for example, refer to cited document 4), but due to Metal compounds of fatty acids or metal complexes of amines are easily reduced due to their high reactivity. Therefore, during long-term storage, the reduction reaction will be caused by sunlight or heat, resulting in the growth of metal particles or the formation of aggregates, which will easily damage the stability of the dispersion. sexual problems

In addition, the reducing agent used in this method is a very strong reducing agent such as tert-butylamine borane, sodium borohydride, hydrogen, etc., so the reaction speed is fast and it is difficult to control the particle growth

Therefore, especially for fatty acids with less than 10 carbon atoms, many aggregates are generated and good dispersions cannot be obtained

[0009] In addition, it is known that 10 -6 It has a volume resistance value in the order of Ω·cm (for example, refer to Cited Document 5), but there is a problem that sufficient electrical conductivity cannot be exhibited unless fired at a high temperature of 200°C or higher in order to develop this resistance value.

In addition, silver is easily absorbed by SO present in the air 2 Sulfur atoms such as gases are sulfided. Because the surface of the circuit pattern is exposed to the atmosphere, a sulfide film will be formed, discoloration or conductivity will decrease, or there will be problems such as deterioration of communication characteristics when used as an antenna circuit. Therefore, it is necessary to prevent metal sulfide.

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