Aqueous ink, ink cartridge and ink jet recording method
The invention provides an aqueous ink containing a self-dispersible pigment having a carboxylic acid group bonded directly or through another atomic group to a particle surface of a pigment and a lactone group bonded to the particle surface of the pigment, wherein, as determined by a selective neutralization method, an introduced amount of the carboxylic acid group is 0.60 mmol/g or more and a ratio of an introduced amount (mmol/g) of the lactone group to the introduced amount (mmol/g) of the carboxylic acid group is 0.20 time or less.
1. An aqueous ink comprising a self-dispersible pigment having (i) a carboxylic acid group bonded directly or through another atomic group to a particle surface of a pigment and (ii) a lactone group bonded to the particle surface of the pigment,
wherein, as determined by a selective neutralization method, an introduced amount of the carboxylic acid group is 0.60 mmol/g or more and a ratio of an introduced amount (mmol/g) of the lactone group to the introduced amount (mmol/g) of the carboxylic acid group is 0.20 times or less.
2. The aqueous ink according to claim 1 , wherein the DBP oil absorption of the pigment is 120 ml/100 g or more.
3. The aqueous ink according to claim 1 , wherein the self-dispersible pigment has 2 or more carboxylic acid groups bonded to the particle surface of the pigment through another atomic group.
4. The aqueous ink according to claim 1 , wherein said another atomic group is an arylene group.
5. The aqueous ink according to claim 1 , wherein the pigment is carbon black.
6. The aqueous ink according to claim 1 , wherein the self-dispersible pigment is produced by a process comprising a step of bonding a group R 1 in the general formula (1) to a particle surface of a pigment by a radical addition reaction induced by removal of a hydrogen atom from a compound represented by the general formula (1):
HN═N—R 1 (1)
wherein R 1 is a group having at least one of an aliphatic group and an aromatic group and being substituted with a carboxylic acid group.
7. An ink cartridge comprising an ink and an ink storage portion storing the ink, wherein the ink comprises the ink according to claim 1 .
8. An ink jet recording method comprising ejecting an ink from a recording head of an ink jet system to record an image on a recording medium, wherein the ink comprises the ink according to claim 1 .
9. The aqueous ink according to claim 1 , wherein the introduced amount of the carboxylic acid group is 1.50 mmol/g or less.
10. The aqueous ink according to claim 1 , wherein the DBP oil absorption of the pigment is 170 ml/100 g or less.
11. The aqueous ink according to claim 1 , wherein the introduced amount of the lactone group is 0.18 mmol/g or less.
12. The aqueous ink according to claim 6 , wherein the step is conducted in a liquid medium.
13. The aqueous ink according to claim 6 , wherein the step is conducted in the presence of an oxidizing agent.
14. The aqueous ink according to claim 6 , wherein the step is conducted at a pH of 1 or more to 13 or less.