Patent ID: 7049039

Claim:
A coloring agent which comprises coloring particles modified with a compound, wherein said compound is a compound represented by the following Formula (2): R 1a -A 1 -R 3 —N═N—R 4 -A 2 -R 2a (2) wherein R 1a is a long-chain aliphatic hydrocarbon group having 6 to 30 carbon atoms, or an aryl group having 6 to 12 carbon atoms which has an alkyl group having 1 to 20 carbon atoms (the former carbon atoms excluding those of the alkyl group moiety); R 2a is a carboxyl group, a carboxylic acid group, a sulfuric ester group, a sulfate, a sulfonic acid group, a sulfonic acid group having a salt structure, or an aliphatic hydrocarbon group having 1 to 20 carbon atoms which has as a substituent at least one of a carboxyl group, a carboxylic acid group, a carboxylic acid salt group, a sulfuric ester group, a sulfate, a sulfonic acid group or a sulfonic acid group having a salt structure or an aromatic hydrocarbon group having 6–20 carbon atoms which has as a substituent at least one of a carboxyl group, a carboxylic acid group, a carboxylic acid salt group, a sulfuric ester group, a sulfate, a sulfonic acid group or a sulfonic acid group having a salt structure; R 3 and R 4 may be the same or different and are alkylene groups having electron-attracting groups on the carbon atoms adjoining to the azo group; A 1 may be absent, or represents at least one of an ester linkage, an amide linkage, a urethane linkage or an ether linkage; and A 2 may be absent, or represents at least one of an ester linkage, an amide linkage, a urethane linkage or an ether linkage.