Patent ID: 7465344

Claim:
An aqueous ink for ink jet recording, which comprises: at least one dye; and at least one of a compound having at least one phosphonic acid group and at least one carboxyl group and a compound having at least two phosphonic acid groups as a print density improver(s), wherein the at least one of a compound having at least one phosphonic acid group and at least one carboxyl group and a compound having at least two phosphonic acid groups is a compound represented by formula (1): Y m -Z-(PO 3 X 2 ) n (1) wherein Z represents a connecting group which may be substituted; Y represents —CO 2 X, —SO 3 X or other anionic hydrophilic substituent; X represents lithium; m represents an integer of 0 or more; and n represents an integer of 1 or more when m is 1 or more and Y contains —SO 3 X, and n represents an integer of 2 or more when m is 0 or when m is 1 or more but Y is free of —SO 3 X, with the proviso that when there are a plurality of Y's, they may be the same or different.