Ink compositions for inkjet recording

Details Ink compositions for inkjet recording Ink compositions for inkjet recording

2002-07-03

2004-12-28

Klemanski, Helene (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Marking

C106S031500, C106S031580, C106S031590

Reexamination Certificate

active

06835240

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an ink composition for inkjet recording (which may hereinafter be called “inkjet recording ink composition”) capable of providing high-quality recorded images, excellent in discharge stability and also excellent in shelf life of the images thus formed.
BACKGROUND OF THE INVENTION
With recent widespread use of computers, inkjet printers have come to be used not only at offices but also at home for printing images on paper, film or cloth.
Inkjet recording is conducted by the following method, for example, a method of discharging ink droplets by making use of a piezoelectric element to apply pressure to them; a method of discharging ink droplets by heating an ink to generate air bubbles therein; a method making use of ultrasonic wave; or a method of making use of static power for suction and discharge of ink droplets. Inks for such inkjet recording methods, aqueous inks, oil-based inks or solid (molten) inks are used. Of these, aqueous inks are most popularly employed in consideration of manufacturing ease, handling ease, odor and safety.
Colorants used for such inkjet recording inks are required to have high solubility in a solvent, permit high-density recording, provide good hue, have excellent fastness to light, heat, air, water and chemicals, have good fixing property to an image receiving material without cause bleeding easily, have excellent storage stability as an ink, have no toxicity, have high purity and be available at a low cost. It is however very difficult to find a colorant capable of satisfying the above-described requirements without lowering their levels. Particularly, there is a strong demand for a colorant having a good magenta hue and excellent light fastness.
A variety of dyes and pigments have already been proposed for use in inkjet recording and they are practically used. Colorants satisfying all of the above-described requirements have however not yet been found. It is difficult to attain satisfactory color hue and light fastness simultaneously by using conventionally well known dyes or pigments having a color index number assigned thereto.
In Japanese Patents Laid-Open Nos. 74761/1983 and 92369/1985, proposed is an ink comprising a dye, glycerin, and diethylene glycol or an ethylene-oxide adduct of an alcohol, while use of an ethylene-oxide adduct of a long-chain linear alcohol is proposed in Japanese Patent Laid-Open No. 265098/2000. These proposals are however accompanied with the drawback that the quality of an image formed using the above-described ink deteriorates during storage.
In Japanese Patents Laid-Open Nos. 88048/1994, 333532/1996 and 333533/1996, and U.S. Pat. Nos. 5,837,043 and 5,626,655, proposed are inks comprising an ethylene-oxide adduct of a higher alcohol and capable of lessening bleeding of a recorded image, but these inks also involve problems such as tendency to cause clogging and a change in color tone due to poor shelf life of an image after printing.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide an inkjet recording ink composition having high discharge stability and being free from defects in hue, weather resistance, water resistance and image quality.
(1) An ink composition for inkjet recording obtained by dissolving or dispersing, in an aqueous medium, an azo dye having an aromatic nitrogen-containing 6-membered heterocycle as a coupling component, said composition further comprising a surfactant.
(2) An ink composition for inkjet recording as described above in (1), wherein the azo dye is represented by the following formula (A-1):
wherein,
A represents a residue of a 5-membered heterocyclic diazo component A-NH
2
,
B
1
and B
2
represent ═CR
1
— and —CR
2
═, respectively, or either one represents a nitrogen atom and the other one represents ═CR
1
— or —CR
2
═,
R
5
and R
6
each independently represents a hydrogen atom, an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an alkoxycarbonyl group, aryloxycarbonyl group, a carbamoyl group, an alkyl- or aryl-sulfonyl group or a sulfamoyl group, which may each have a substituent, and
G, R
1
, and R
2
each independently represents a hydrogen atom, a halogen atom, an aliphatic group, an aromatic group, a heterocyclic group, a cyano group, a carboxyl group, a carbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heterocyclic oxycarbonyl group, an acyl group, a hydroxyl group, an alkoxy group, an aryloxy group, a silyloxy group, an acyloxy group a carbamoyloxy group, a heterocyclic oxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group, an acylamino group, an ureido group, a sulfamoylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, an alkyl- or aryl-sulfonylamino group, a heterocyclic sulfonylamino group, a nitro group, an alkyl- or aryl-thio group, an alkyl- or aryl-sulfonyl group, a heterocyclic sulfonyl group, an alkyl- or aryl-sulfinyl group, a heterocyclic sulfinyl group, a sulfamoyl group, a sulfo group, or a heterocyclic thio group, which may each have a substituent, or
a pair R
1
and R
5
, or a pair R
5
and R
6
may be coupled to form a 5- or 6-membered ring.
(3) An ink composition for inkjet recording as described above in (1) or (2), wherein the surfactant is a nonionic surfactant.
(4) An ink composition for inkjet recording as described above in any one of (1) to (3), wherein the surfactant is represented by the formula (I) or (II):
R
1
O—(CH
2
CH
2
O)
m
1
—H  (I)
wherein, R
1
represents a C
5-40
alkyl group and m
1
represents an average mole of ethylene oxide added, specifically, 2 to 40.
R
2
COO—(CH
2
CH
2
O)
m
2
—H  (II)
wherein, R
2
represents a C
5-40
alkyl group and m
2
represents an average mole of ethylene oxide added, specifically 2 to 40.
(5) An inkjet recording method, which comprises using an ink composition for inkjet recording as described above in any one (1) to (4).
(6) An inkjet recording method, which comprises discharging, according to a recording signal, ink droplets onto an image receiving material having, on a substrate thereof, an image receiving layer containing white inorganic pigment particles and recording an image onto the image receiving material, wherein the ink droplets are made of an ink composition for inkjet recording as described above in any one of (1) to (4).
DETAILED DESCRIPTION OF THE INVENTION
The invention will hereinafter be described more specifically.
A dye to be used for the inkjet recording ink composition of the invention is an azo dye having as a coupling component an aromatic nitrogen-containing 6-membered heterocycle, of which that represented by the following formula (A-1) is preferred.
In the formula (A-1), A represents the residue of a 5-membered heterocyclic diazo component A-NH
2
. Examples of the hetero atom of the heterocycle include N, O and S. Preferred is a nitrogen-containing 5-membered heterocycle and the heterocycle may be condensed with an aliphatic ring, an aromatic ring or another heterocycle. Preferred examples of the heterocycle as A include pyrazole ring, imidazole ring, thiazole ring, isothiazole ring, thiadiazole ring, benzothiazole ring, benzoxazole ring and benzoisothiazole ring. Each of these heterocyclic groups may have a substituent further. Of these, the pyrazole ring, imidazole ring, isothiazole ring, thiadiazole ring and benzothiazole ring represented by the below-described formulas (a) to (f) are preferred.
In the above-described formulas (a) to (f), R
7
to R
20
represents substituents similar to those described in G, R
1
and R
2
.
Of the formulas (a) to (f), preferred are pyrazole and isothiazole rings represented by the formulas (a) and (b), with the pyrazole ring of the formula (a) being most preferred.
B
1
and B
2
represent ═CR
1
— and —CR
2
═, respectively, or one of them represents a nitrogen atom and the other one represents ═CR
1
— or —CR
2
═, of which the former case is preferred.
R
5
and R
6
each independently represents

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