Ink set for ink-jet recording, and method for producing ink set for ink-jet recording

1. An ink set for ink-jet recording comprising:

an achromatic color ink containing potassium ion and at least one of lithium ion and sodium ion; and

a chromatic color ink containing at least one selected from the group consisting of: the potassium ion, the lithium ion and the sodium ion,

wherein the ink set satisfies the following conditions (X) and (Y):

K a /(Li a +Na a +K a )>0.7  Condition (X):

in the condition (X),

K a : concentration (ppm) of the potassium ion in the achromatic color ink,

Li a : concentration (ppm) of the lithium ion in the achromatic color ink,

Na a : concentration (ppm) of the sodium ion in the achromatic color ink; and

K c /(Li c +Na c +K c )<0.6  Condition (Y):

in the condition (Y),

K c : concentration (ppm) of the potassium ion in the chromatic color ink,

Li c : concentration (ppm) of the lithium ion in the chromatic color ink,

Na c : concentration (ppm) of the sodium ion in the chromatic color ink.

2. The ink set for ink-jet recording according to claim 1 , wherein the ink set satisfies the following conditions (X1) and (Y1):

K a /(Li a +Na a +K a )>0.8  Condition (X1):

in the condition (X1),

K a : the concentration (ppm) of the potassium ion in the achromatic color ink,

Li a : the concentration (ppm) of the lithium ion in the achromatic color ink,

Na a : the concentration (ppm) of the sodium ion in the achromatic color ink; and

K c /(Li c +Na c +K c )<0.5  Condition (Y1):

in the condition (Y1),

K c : the concentration (ppm) of the potassium ion in the chromatic color ink,

Li c : the concentration (ppm) of the lithium ion in the chromatic color ink,

Na c : the concentration (ppm) of the sodium ion in the chromatic color ink.

3. The ink set for ink-jet recording according to claim 1 , wherein the ink set satisfies the following condition (X2):

K a /(Li a +Na a +K a )>0.9  Condition (X2):

in the condition (X2),

K a : the concentration (ppm) of the potassium ion in the achromatic color ink,

Li a : the concentration (ppm) of the lithium ion in the achromatic color ink,

Na a : the concentration (ppm) of the sodium ion in the achromatic color ink.

4. The ink set for ink-jet recording according to claim 1 , wherein

the achromatic color ink is a black ink containing a black pigment and water; and

the chromatic color ink is at least one water-based chromatic color ink selected from the group consisting of:

a water-based yellow ink containing a yellow pigment and the water;

a water-based magenta ink containing a magenta pigment and the water; and

a water-based cyan ink containing a cyan pigment and the water.

5. The ink set for ink-jet recording according to claim 1 , wherein

the achromatic color ink is a water-based black ink containing a self-dispersible carbon black, a surfactant and water; and

the chromatic color ink is at least one water-based chromatic color ink selected from the group consisting of:

a water-based yellow ink containing a yellow pigment, a resin dispersant, a surfactant and the water;

a water-based magenta ink containing a magenta pigment, a resin dispersant, a surfactant and the water, and

a water-based cyan ink containing a cyan pigment, a resin dispersant, a surfactant and the water.

6. The ink set for ink-jet recording according to claim 1 , wherein the achromatic color ink is a water-based black ink containing a self-dispersible carbon black and water;

and the chromatic color ink is a water-based chromatic color ink containing a self-dispersible chromatic pigment and the water.

7. The ink set for ink-jet recording according to claim 6 , wherein the chromatic color ink is at least one water-based chromatic color ink selected from the group consisting of:

a water-based yellow ink containing a self-dispersible yellow pigment and the water;

a water-based magenta ink containing a self-dispersible magenta pigment and the water; and

a water-based cyan ink containing a self-dispersible cyan pigment and the water.

8. The ink set for ink-jet recording according to claim 4 , wherein

the yellow pigment includes an azo pigment;

the magenta pigment includes a quinacridone pigment; and

the cyan pigment includes a phthalocyanine pigment.

9. The ink set for ink-jet recording according to claim 8 , wherein

the yellow pigment includes at least one of C.I. pigment yellow 74 and C.I. pigment yellow 155;

the magenta pigment includes at least one selected from the group consisting of: C.I. pigment violet 19, C.I. pigment red 122, C.I. pigment red 202, and a solid solution containing at least two kinds of magenta pigments among three kinds of magenta pigments which are C.I. pigment violet 19, C.I. pigment red 122 and C.I. pigment red 202; and

the cyan pigment includes at least one of C.I. pigment blue 15:3 and C.I. pigment blue 15:4.

10. The ink set for ink-jet recording according to claim 4 , wherein

a total sum of the concentration of the potassium ion, the concentration of the lithium ion and the concentration of the sodium ion in the water-based black ink is in a range of 50 ppm to 2000 ppm;

a total sum of the concentration of the potassium ion, the concentration of the lithium ion and the concentration of the sodium ion in the water-based yellow ink is in a range of 50 ppm to 2000 ppm;

a total sum of the concentration of the potassium ion, the concentration of the lithium ion and the concentration of the sodium ion in the water-based magenta ink is in a range of 50 ppm to 2000 ppm; and

a total sum of the concentration of the potassium ion, the concentration of the lithium ion and the concentration of the sodium ion in the water-based cyan ink is in a range of 50 ppm to 2000 ppm.

11. The ink set for ink-jet recording according to claim 1 , satisfying the following condition (A):

Ra/Rc> 1.2  Condition (A):

wherein the Ra and the Rc in the condition (A) are represented by the following formulae (1) and (2):

Ra =K a /(Li a +Na a +K a )  formula (1):

in the formula (1),

K a : the concentration (ppm) of the potassium ion in the achromatic color ink,

Li a : the concentration (ppm) of the lithium ion in the achromatic color ink,

Na a : the concentration (ppm) of the sodium ion in the achromatic color ink; and

Rc =K c /(Li c +Na c +K c )  formula (2):

in the formula (2),

K c : the concentration (ppm) of the potassium ion in the chromatic color ink,

Li c : the concentration (ppm) of the lithium ion in the chromatic color ink,

Na c : the concentration (ppm) of the sodium ion in the chromatic color ink.

12. The ink set for ink-jet recording according to claim 1 , satisfying the following condition (A1):

Ra/Rc> 2.0  Condition (A1):

wherein the Ra and the Rc in the condition (A1) are represented by the following formulae (1) and (2):

Ra =K a /(Li a +Na a +K a )  formula (1):

in the formula (1),

K a : the concentration (ppm) of the potassium ion in the achromatic color ink,

Li a : the concentration (ppm) of the lithium ion in the achromatic color ink,

Na a : the concentration (ppm) of the sodium ion in the achromatic color ink; and

Rc =K c /(Li c +Na c +K c )  formula (2):

in the formula (2),

K c : the concentration (ppm) of the potassium ion in the chromatic color ink,

Li c : the concentration (ppm) of the lithium ion in the chromatic color ink,

Na c : the concentration (ppm) of the sodium ion in the chromatic color ink.

13. The ink set for ink-jet recording according to claim 1 , comprising the chromatic color ink as a plurality of chromatic color inks, wherein all the plurality of chromatic color inks satisfy the condition (Y).

14. An ink set for ink-jet recording comprising:

an achromatic color ink containing potassium ion and at least one of lithium ion and sodium ion; and

two or more chromatic color inks each of which containing at least one selected from the group consisting of: the potassium ion, the lithium ion and the sodium ion,

wherein the ink set satisfies the following conditions (X) and (Z):

K a /(Li a +Na a +K a )>0.7  Condition (X):

in the condition (X),

K a : concentration (ppm) of the potassium ion in the achromatic color ink,

Li a : concentration (ppm) of the lithium ion in the achromatic color ink,

Na a : concentration (ppm) of the sodium ion in the achromatic color ink; and

K ct /(Li ct +Na ct +K ct )<0.6  Condition (Z):

in the condition (Z),

K ct : a total sum of concentrations (ppm) of the potassium ion in the two or more chromatic color inks;

Li ct : a total sum of concentrations (ppm) of the lithium ion in the two or more chromatic color inks;

Na ct : a total sum of concentrations (ppm) of the sodium ion in the two or more chromatic color inks.

15. A method for producing the ink set for ink-jet recording as defined in claim 1 , the method comprising:

preparing an achromatic color ink so as to satisfy the condition (X);

measuring concentrations of potassium ion, lithium ion and sodium ion, respectively, in the prepared achromatic color ink;

preparing a chromatic color ink so as to satisfy the condition (Y);

measuring concentrations of the potassium ion, the lithium ion and the sodium ion, respectively, in the prepared chromatic color ink; and

combining the achromatic color ink and the chromatic color ink.