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

each of X m (m=1, 2, 3, 4) represents a carbon atom or a nitrogen atom;

each of Y m (m=1, 2, 3, 4) represents a carbon atom or a nitrogen atom;

each of A m (m=1, 2, 3, 4) represents a group necessary for forming, together with X m and Y m , either an aromatic hydrocarbon ring which may further form a condensed ring with another ring or a hetero ring which may further form a condensed ring with another ring;

each of A m may have a substituent;

each of the substituents of A m may further have a substituent;

at least one of the substituents of A m and the substituents of the substituents of A m is ionic hydrophilic group; and

M represents a hydrogen atom, a metal element, a metal oxide, a metal hydroxide or a metal halide, provided that the following conditions are satisfied:

(i) at least one of the four rings, each of which comprises respective A m , X m and Y m , is a hetero ring;

(ii) when all of the four rings, each of which comprises respective A m , X m and Y m , are a pyridine ring, both of atoms adjacent to X m and Y m in each pyridine ring are a carbon atom; and

(iii) when all of the four rings, each of which comprises respective A m , X m and Y m , are a pyrazine ring, both of atoms adjacent to X m and Y m in each pyrazine ring are a carbon atom.

2. The ink composition according to claim 1 , wherein the colorant represented by the formula (I) is represented by the following formula (II):

wherein

each of Q m (m=1, 2, 3, 4) represents ═C(J 1 )- or —N═;

each of P m (m=1, 2, 3, 4) represents ═C(J 2 )- or —N═;

each of W m (m=1, 2, 3, 4) represents ═C(J 3 )- or —N═;

each of R m (m=1, 2, 3, 4) represents ═C(J 4 )- or —N═;

each of J n (n=1, 2, 3, 4) represents a hydrogen atom or a substituent, and when each of J n represents a substituent, each of J n may further have a substituent;

at least one of J n and the substituents of J n is an ionic hydrophilic group; and

M represents a hydrogen atom, a metal element, a metal oxide, a metal hydroxide or a metal halide,

provided that the following conditions are satisfied:

(i) at least one of the four rings (A), (B), (C) and (D), in which the ring (A) comprises Q 1 , P 1 , W 1 and R 1 , the ring (B) comprises Q 2 , P 2 , W 2 and R 2 , the ring (C) comprises Q 3 , P 3 , W 3 and R 3 , and the ring (D) comprises Q 4 , P 4 , W 4 and R 4 , is a hetero ring;

(ii) when all of the four rings (A), (B), (C) and (D) are a pyridine ring, both of Q m and R m in each pyridine ring are a carbon atom; and

(iii) at least one of the four rings (A), (B), (C) and (D) is not a pyrazine ring.

3. The ink composition according to claim 2 , wherein

at least one of the four rings (A), (B), (C) and (D) represents an aromatic hydro-carbon ring; and

at least one of the four rings (A), (B), (C) and (D) represents a pyridine ring or a pyrazine ring.

4. The ink composition according to claim 2 , wherein at least one of the four rings (A), (B), (C) and (D) represents an aromatic hydro-carbon ring represented by the following formula (IV):

wherein

* represents a position at which the ring is bonded to the 3- and 4-positions of the 5-membered nitrogen-containing ring to form the phthalocyanine structure;

the position closer to * in the aromatic hydrocarbon ring is called α-position;

the position farther from * in the aromatic hydrocarbon ring is called n-position;

the position to which G(s) is substituted is not specified as either the α-position or the β-position;

each of G(s) represents a substituent selected from the group consisting of —SO—Z, —SO 2 —Z, —SO 2 NV 1 V 2 , —CONV 1 V 2 , —CO 2 Z, —COZ, a sulfo group and a salt thereof, a carboxyl group and a salt thereof, and a phosphono group and a salt thereof;

t represents an integer of 1 to 4;

Z(s) may be the same as or different from each other, and each of Z(s) represents a substituted or unsubstituted alkyl group having a total carbon number of 1 to 20, a substituted or unsubstituted cycloalkyl group having a total carbon number of 3 to 20, a substituted or unsubstituted alkenyl group having a total carbon number of 2 to 20, a substituted or unsubstituted alkynyl group having a total carbon number of 2 to 12, a substituted or unsubstituted aryl group having a total carbon number of 6 to 20, or a substituted or unsubstituted heterocyclic group having a total carbon number of 4 to 20;

V 1 (s) may be the same as or different from each other, and each of V 1 (s) represents a hydrogen atom, a substituted or unsubstituted alkyl group having a total carbon number of 1 to 20, a substituted or unsubstituted cycloalkyl group having a total carbon number of 3 to 20, a substituted or unsubstituted alkenyl group having a total carbon number of 2 to 20, a substituted or unsubstituted alkynyl group having a total carbon number of 2 to 12, a substituted or unsubstituted aralkyl group having a total carbon number of 7 to 20, a substituted or unsubstituted aryl group having a total carbon number of 6 to 20, or a substituted or unsubstituted heterocyclic group having a total carbon number of 4 to 20; and

V 2 (s) may be the same as or different from each other, and each of V 2 (s) represents a hydrogen atom, a substituted or unsubstituted alkyl group having a total carbon number of 1 to 20, a substituted or unsubstituted cycloalkyl group having a total carbon number of 3 to 20, a substituted or unsubstituted alkenyl group having a total carbon number of 2 to 20, a substituted or unsubstituted alkynyl group having a total carbon number of 2 to 12, a substituted or unsubstituted aralkyl group having a total carbon number of 7 to 20, a substituted or unsubstituted aryl group having a total carbon number of 6 to 20, or a substituted or unsubstituted heterocyclic group having a total carbon number of 4 to 20.

5. The ink composition according to claim 3 , wherein at least one of the four rings (A), (B), (C) and (D) represents an aromatic hydro-carbon ring represented by the following formula (V):

wherein

G(s) has the same meaning as in the formula (IV);

t represents an integer of 0 to 2; and

* represents a position at which the ring is bonded to the 3- and 4-positions of the 5-membered nitrogen-containing ring to form the phthalocyanine structure.

6. The ink composition according to claim 5 , wherein at least one of the four rings (A), (B), (C) and (D) represents an aromatic hydro-carbon ring represented by the formula (V); and

at least one of the four rings (A), (B), (C) and (D) represents a pyridine ring.

7. The ink composition according to claim 6 , wherein at least one of the four rings (A), (B), (C) and (D) represents an aromatic hydro-carbon ring represented by the formula (V); and

at least one of the four rings (A), (B), (C) and (D) represents a pyridine ring represented by formula (VI):

wherein

* represents a position at which the ring is bonded to the 3- and 4-positions of the 5-membered nitrogen-containing ring to form the phthalocyanine structure.

8. The ink composition according to claim 7 , wherein at least one of the four rings (A), (B), (C) and (D) represents an aromatic hydro-carbon ring represented by the following formula (VII); and

at least one of the four rings (A), (B), (C) and (D) represents a pyridine ring represented by the formula (VI):

wherein

G(s) has the same meaning as in the formula (IV);

t represents an integer of 0 to 2; and

* represents a position at which the ring is bonded to the 3- and 4-positions of the 5-membered nitrogen-containing ring to form the phthalocyanine structure.

9. The ink composition according to claim 1 , wherein the water-soluble planar compound has at least two aromatic rings.

10. 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.

11. The ink composition according to claim 1 , wherein the water-soluble planar compound has a sulfo group.

12. The ink composition according to claim 1 , wherein the guanidine-based compound is represented by the following formula (1):

wherein

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.

13. 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.

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

a surfactant.

15. The ink composition according to claim 14 , wherein the surfactant is in an amount of 0.05 to 50 g/liter based on the ink composition.

16. The ink composition according to claim 14 , wherein the surfactant is a nonionic surfactant.

17. The ink composition according to claim 16 , wherein the nonionic surfactant is an acetylene glycol-based surfactant.

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

an antiseptic.

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

20. An inkjet recording method utilizing the inkjet recording ink according to claim 19 .