Ink composition, inkjet recording ink and inkjet recording method

1. An ink composition comprising:

a colorant represented by the following formula (I);

water;

a guanidine-based compound; and

a colorless water-soluble planar compound having more than ten delocalized π-electrons within one molecule:

wherein,

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

k, l, m and n represent an integer of 0≦k≦8, an integer of0≦1≦8, an integer of 0≦m≦8and an integer of0≦n≦8, respectively, provided that k, l, m and n satisfy 4≦k+1+m+n≦8;

each of X 1 , X 2 , X 3 and X 4 represents a substituent selected from the group consisting of —SO—R 1 , —S0 2 —R 1 , —SO 2 NR 2 R 3 , —CONR 2 R 3 , —CO 2 —R 1 , —CO—R 1 , a sulfo group and a salt thereof, a carboxyl group and a salt thereof, and a phosphono group and a salt thereof, provided that at least one of X 1 , X 2 , X 3 and X 4 has an ionic hydrophilic group as a substituent;

R 1 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;

R 2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;

R 3 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; and

Pc represents a (k+l+m+n)-valent phthalocyanine nucleus represented by the following formula (II);

wherein

each of the four benzene rings A, B, C and D has at least one of X 1 , X 2 , X 3 and X 4 ; and

Y 1 , Y 2 , Y 3 , Y 4 , Y 5 , Y 6 , Y 7 and Y 8 each independently represents a hydrogen atom or a monovalent substituent which may further have a substituent.

2. The ink composition according to claim 1 , wherein

the phthalocyanine nucleus represented by the formula (II) is represented by the following formula (III):

3. The ink composition according to claim 1 , wherein

the colorant represented by the formula (I) is represented by the following formula (IV):

wherein

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

k and l represent an integer of 0<k<8 and an integer of 0<1<8, respectively, provided that k and 1 satisfy 4≦k+1≦8;

each of X 1 and X 2 represents a substituent selected from the group consisting of —SO—R 1 , —SO 2 —R 1 , —SO 2 NR 2 R 3 , a sulfo group and a salt thereof, provided that X 1 and X 2 are different from each other and at least one of X l and X 2 , has an ionic hydrophilic group as a substituent;

R 1 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;

R 2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;

R 3 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; and

Pc represents a (k+1)-valent phthalocyanine nucleus represented by the formula (III), wherein

each of the four benzene rings A, B, C and D has at least one of X 1 and X 2 .

4. The ink composition according to claim 1 , wherein

the water-soluble planar compound has at least two aromatic rings.

5. The ink composition according to claim 1 , wherein

the water-soluble planar compound has no fluorescence, and has 350 nm or less of λmax and 10,000 or less of molar absorption coefficient, wherein

λmax represents a wavelength of the absorption peak having the longest wavelength.

6. The ink composition according to claim 1 , wherein

the water-soluble planar compound has a sulfo group.

7. The ink composition according to claim 1 , wherein

the guanidine-based compound is represented by the following formula (1):

R 101 , R 102 , R 103 and R 104 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, or substituted or unsubstituted an amino group; and

R 105 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group.

8. The ink composition according to claim 1 , wherein

the guanidine-based compound is in an amount of 0.1 to 10 mass% based on the ink composition.

9. The ink composition according to claim 1 , further comprising:

a surfactant.

10. The ink composition according to claim 9 , wherein

the surfactant is in an amount of 0.05 to 50 g/liter based on the ink composition.

11. The ink composition according to claim 9 , wherein

the surfactant is a nonionic surfactant.

12. The ink composition according to claim 11 , wherein

the nonionic surfactant is an acetylene glycol-based surfactant.

13. The ink composition according to claim 1 , further comprising:

an antiseptic.

14. An inkjet recording ink prepared by utilizing the ink composition according to claim 1 .

15. An inkjet recording method utilizing the inkjet recording ink according to claim 14 .