Low-resistance conductive pigment and method of manufacturing same.

摘要

[OBJECT] An object of the present invention is to reduce resistance and improve color tone of a conductive pigment comprising indium oxide containing tin, having an Sn content within a range of from 1 to 15 mol% relative to the total amount of In + Sn. [CONSTRUCTION] (1) Immersing an ITO pigment in alcohol, ketone, ester or amine and heat-treating same at a temperature of up to 500 DEG C under a reduced pressure or in an inert gas, or heat-treating same at a temperature of up to 500 DEG C in an inert gas containing H2, NH3 or CO in an amount of 0.5 to 20 vol.% to reach a surface acidity of from 8 x 10<-><7> to 1 x 10<-><5> mol/m<2> permits achievement of a volume resistivity (50 kg/cm<2> green compact) of under 2 x 10<0> and at least 2 x 10<-><2> OMEGA .cm. (2) Heat-treating an ITO pigment or a precursor hydroxide thereof at 300 to 1,150 DEG C in an inert gas or under a reduced pressure, and introducing an oxygen vacancy of 0.05 to 0.35 mol into crystal grains permits achievement of a bluish pigment excellent in visibility having a color tone comprising an x-value of from 0.265 to 0.300 and a y-value of from 0.290 to 0.315 on the xy chromaticity scale and a volume resistivity of from 8 x 10<-><1> to 1 x 10<-><2> OMEGA .cm. (3) By conducting sequentially the steps (2) and (1) described above, or heat-treating same at 300 to 1,150 DEG C in an inert gas containing H2, NH3 or CO in an amount of up to 20 vol.%, there is available a low-resistance ITO pigment, comparable with a sputtering film, having a volume resistivity of from 8 x 10<-><2> to 9 x 10<-><5> OMEGA .cm, in addition to the bluish color tone as described above. [EFFECTS] When a pigment has an average primary particle size of up to 0.2 mu m it is possible to form a transparent conductive film which is useful as a transparent electrode and a heating element having a transparent surface.