Patent ID: 7432315

Claim:
An ink composition comprising: water; a colorant containing a pigment; a nonionic surfactant, the content of the nonionic surfactant being at a critical micelle concentration or more; and a polyester resin containing a polybasic carboxylic acid ingredient and a polyhydric alcohol ingredient, the polybasic carboxylic acid ingredient containing three or more dicarboxylic acids which include at least sodium 5-sulfoisophthalate and aromatic dicarboxylic acid not having a metal sulfonate group, wherein a ratio of the aromatic dicarboxylic acid having a metal sulfonate group contained in the polybasic carboxylic acid ingredient is 0.5 mol % or more and 3.5 mol % or less, and wherein the polyester resin has a number average molecular weight within a range of from 5,000 to 50,000, and the polyester resin has a glass transition point Tg within a range of from −20° C. to 70° C.