Ink composition and inkjet recording method

1. An ink composition comprising:

a coloring agent having an oxidation potential of more electropositive than 1.0V (vs SCE) and being a dye represented by formula (2):

wherein X 11 , X 12 , X 13 and X 14 each independently represents —SO-Z, —SO 2 -Z, —SO 2 NR 11 R 12 , a sulfo group, —CONR 11 R 12 or —CO 2 R 11 ;

Z's each independently represent an alkyl group, an alkenyl group, an aralkyl group, an aryl group or a heterocyclic group, which may be further substituted by a substituent;

R 11 and R 12 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group or a heterocyclic group, which may be further substituted by a substituent;

Y 11 , Y 12 , Y 13 , Y 14 , Y 15 , Y 16 , Y 17 and Y 18 each independently represents a hydrogen atom or a monovalent substituent;

a 11 to a 14 respectively stand for the numbers of substituents in X 11 to X 14 and each independently represents an integer of 1 or 2; and

M represents a hydrogen atom, or a metal atom or an oxide, a hydroxide or a halide of the metal atom;

a water;

a guanidine compound selected from one of the following compounds:

 and

a surfactant.

2. The ink composition according to claim 1 ,

wherein a content of the guanidine compound in the ink composition is from 0.1 to 10% by mass.

3. The ink composition according to claim 1 , wherein a content of the surfactant in the ink composition is from 0.05 to 50 g/l.

4. The ink composition according to claim 1 , wherein the surfactant is a nonionic surfactant.

5. The ink composition according to claim 4 , wherein the nonionic surfactant is an acetylene glycol-base surfactant.

6. The ink composition according to claim 1 , wherein at least one of X 11 to X 14 represents a water-soluble group, and at least one of X 11 to X 14 other than the at least one of X 11 to X 14 representing the water-soluble group represents a hydrogen bond group.

7. The ink composition according to claim 6 , wherein a group number ratio of the water-soluble group (x)/the hydrogen bond group (y) is (0<x<3)/(1<y<4).

8. The ink composition according to claim 6 , wherein the water-soluble group is SO 2 (CH 2 ) 3 SO 3 Li and the hydrogen bond group is SO 2 (CH 2 ) 3 SO 2 NHCH 2 CH(CH 3 )OH.

9. The ink composition according to claim 1 , which is utilized in inkjet recording.

10. An inkjet recording method which comprises jetting an ink composition according to claim 1 .

11. The ink composition according to claim 4 , wherein the nonionic surfactant is a compound represented by formula (I), (II) or (III):

R 21 O CH 2 CH 2 O m 1 H  Formula (I)

wherein R 21 represents an alkyl group having from 5 to 40 carbon atoms; and m 1 stands for the average number of ethylene oxide moles added which ranges from 2 to 40;

R 24 COO CH 2 CH 2 O m 2 H  Formula (II)

wherein R 24 represents an alkyl group having from 5 to 40 carbon atoms; and m 2 stands for the average number of ethylene oxide moles added which ranges from 2 to 40;

wherein R 31 and R 32 each independently represents an alkyl group having from 1 to 18 carbon atoms;

R 33 represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms;

X represents a hydrogen atom, or

wherein R 34 and R 35 each independently represents an alkyl group having from 1 to 18 carbon atoms;

R 36 represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms or a phenyl group; and

m 3 and m 4 each independently represents an average number of ethylene oxide moles added, provided that m 3 +m 4 ranges from 0 to 100, and provided that when m 3 is 0, R 33 represents a hydrogen atom, when m 4 is 0, R 36 represents a hydrogen atom and when X is a hydrogen atom, m 3 is from 1 to 100.