Water-based inks for ink-jet printing

[0185] Twenty parts of methyl ethyl ketone and 0.03 part of a chain transfer agent (2-mercaptoethanol) together with 10% of 200 parts of a mixture of respective monomers shown in Table 1 below were charged into a reaction vessel and mixed with each other, and then the reaction vessel was fully purged with a nitrogen gas to thereby obtain a mixed solution.

[0186] Separately, remaining 90% of the monomer mixture shown in Table 1 was charged into a dropping funnel, and further 0.27 part of the chain transfer agent, 60 parts of methyl ethyl ketone and 1.2 parts of a radical polymerization initiator (2,2′-azobis(2,4-dimethyl valeronitrile)) were added thereto and mixed with each other, and the dropping funnel was fully purged with a nitrogen gas to thereby obtain a mixed solution.

[0187] The mixed solution in the reaction vessel was heated to 65° C. under stirring in a nitrogen atmosphere, and then the mixed solution in the dropping funnel was gradually dropped thereinto over 3 h. After the

[0192] The same procedure as in Synthesis Example 1 was repeated except for using a styrene monomer in place of (c) benzyl methacrylate shown in Table 1, thereby obtaining a polymer solution.

[0193] Twenty five parts of the polymer produced by drying the polymer solution obtained in Synthesis Example 1 under reduced pressure was dissolved in 70 parts of methyl ethyl ketone. Further, 4.1 parts of a neutralizing agent (a 5N sodium hydroxide aqueous solution) and 230 parts of ion-exchanged water were added to the resultant solution to neutralize a salt-forming group of the polymer (degree of neutralization: 75%), and then 75 parts of a quinacridone pigment (C.I. Pigment Violet 19 “Hostaperm Red E5B02” (tradename) available from Clariant Japan Co., Ltd.) was added into the reaction solution and mixed with each other at 20° C. for 1 h using disper blades. The thus obtained mixture was dispersed under a pressure of 200 MPa by passing through a dispersing apparatus “MICROFLUIDIZER” (tradename) available from Microfluidics Corp., 10 times.

[0194] The resultant dispersion was mixed with 250 parts of ion-exchanged water under stirring, and then methyl ethyl ketone was removed from th