Patent ID: 7370952

Claim:
A water-based ink, comprising: a surface treated pigment as a coloring material; a water-soluble organic solvent for dispersing the pigment; water for dispersing the pigment; an organic pH buffer selected from Good's buffers; and a compound selected from the group of aminopropanediol derivatives consisting of 1-amino-2,3-propanediol, 1-methylamino-2,3-propanediol, 2-amino-2-methyl-1,3-propanediol, and 2-amino-2-ethyl-1,3-propanediol, wherein the organic pH buffer selected from Good's buffers is selected from the group consisting of N-cyclohexyl-3-aminopropanesulfonic acid, N-cyclohexyl-2-hydroxy-3-aminopropanesulfonic acid, N-cyclohexyl-2-amino-ethanesulfonic acid, N-tris (hydroxymethyl)methyl-3-aminopropanesulfonic acid, N,N-bis (2-hydroxyethyl)glycine, and N-tris (hydroxymethyl)methylglycine.