A first pigment made of a coloring pigment having a primary average particle diameter of 200 nm or smaller or, or made of carbon black having an average particle diameter of a structure of 100 nm or smaller, and a second pigment made of barium sulfate having a primary average particle diameter of 55 nm or smaller are combined so that a value of (acid amount-base amount) of one pigment becomes positive, and a value of (acid amount-base amount) of other pigment becomes negative, and the combined first and second pigments are dispersed in a medium in the presence of a pigment dispersant.