Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-05-23
2004-01-13
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031860
Reexamination Certificate
active
06676736
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a water-based ink composition, and more specifically to a water-based ink composition which can be used for a water-based ink for inkjet recording.
2. Discussion of the Related Art
Inkjet printing is carried out by directly jetting ink droplets from very fine nozzles, and depositing the ink droplets on a recording medium, to form characters or images. The inkjet printing is advantageous in that its printing device produces noise at a low level. Also, the inkjet printing is excellent in operability, facilitates coloration and enables to use plain paper as a recording medium. Therefore, the inkjet printing has been widely used in these years.
The inks used for inkjet printers include water-based ink, oil-based ink and solid ink. The water-based ink, constituting the majority of inks, contains water as a main component, and a colorant such as a dye or pigment dispersion, a moisturizing agent and a surfactant as an auxiliary for discharging ability and image quality. Japanese Patent Laid-Open No. Sho 60-32866 and Hei 4-239067 propose surfactants such as polyethylene glycol lauryl ether and polyoxyethylene nonylphenyl ether as an agent for improving drop directionality.
However, when the surfactant is added to the water-based ink in an amount sufficient for improving drop directionality, there arise some defects in that the water-based ink is spread along with fibers constituting paper, thereby resulting in lowering of printed quality and printed density.
An object of the present invention is to provide a water-based ink composition showing excellent water resistance and high-lighter fastness and high printed density, and more specifically a water-based ink composition having excellent discharging ability when the composition is used in a water-based ink for inkjet recording.
These and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a water-based ink composition comprising:
(A) an aqueous medium;
(B) at least one colorant selected from the group consisting of (i) polymer particles comprising a dye or pigment and a water-insoluble polymer, and (ii) a self-dispersible pigment; and
(C) at least one compound A selected from the group consisting of a compound represented by the formula (I):
wherein each of R
1
, R
2
, R
4
, R
6
and R
7
is independently hydrogen atom, —C
n
H
2n+1
, or —C
n
H
2n
O(CH
2
CHYO)
m
H, wherein Y is hydrogen atom or methyl group, m is a number of 0 to 20, and n is an integer of 1 to 6; each of R
3
and R
5
is independently a hetero atom, —C
n
H
2n
—, wherein n is as defined above, or a divalent hydrocarbon group which may have a hetero atom; each of a, e and i is independently 0 or 1; each of b, f and j is independently a number of 0 to 30; each of c, g and k is independently an integer of 1 to 5; and each of d and h is independently 0 or 1, with proviso that the total number of —CH
2
CHYO— units per molecule is 1 to 100;
a compound represented by the formula (II):
wherein R
8
is —(CH
2
CHYO)
k
—, wherein Y is as defined as above, and k is a number of 0 to 25; X is hydrogen atom, hydroxyl group, —CH
2
O(CH
2
CHYO)
k
H, —O(CH
2
CHYO)
k
H, or —OM, wherein Y and k are as defined as above, and M is an alkali metal atom; and p is an integer of 2 to 7, with proviso that the total number of —CH
2
CHYO— units per molecule is 1 to 100; and
a compound represented by the formula (III):
wherein R
9
is hydrogen atom or —C
q
H
2q+1
, wherein q is an integer of 0 to 4; Y is as defined above; each of r, s, t and u is independently a number of 0 to 30, with proviso that the total number of —CH
2
CHYO— units per molecule is 1 to 100.
DETAILED DESCRIPTION OF THE INVENTION
The aqueous medium comprises water, or a mixture of water and a water-soluble organic solvent excluding the above polyalkoxyalkylene derivative. As water, deionized water is usually employed. As the water-soluble organic solvent, there can be used ethylene glycol, propylene glycol, glycerol, and the like as disclosed in U.S. Pat. No. 5,085,698. A preferable mixture of water and the water-soluble organic solvent can be determined in accordance with surface tension, viscosity and printed quality required. Examples of the mixture of water and the water-soluble organic solvent include a mixture of an alkylene glycol having 2 to 6 carbon atoms and deionized water.
At least one compound A selected from the group consisting of a compound represented by the formula (I), a compound represented by the formula (II), and a compound represented by the formula (III) improves discharging ability and shows high printed density. In the compound represented by the formula (I), the hetero atom includes nitrogen atom, sulfur atom, oxygen atom, phosphorus atom, and the like.
Examples of the compound represented by the formula (I) include glycerol, diglycerol, triglycerol, tetraglycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, 1,2,6-hexanetriol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, 2-methyl-2-(hydroxymethyl)-1,3-propanediol, pentaerythritol, erythritol, D-threitol, L-threitol, DL-threitol, adonitol, D-arabitol, L-arabitol, xylitol, dulcitol, L-iditol, D-mannitol, D-sorbitol, their adducts with an alkylene oxide such as ethylene oxide and/or propylene oxide, and the like.
Examples of commercially available ones include Liponic REG-1 and Liponic RSO-20 commercially available from Lipo Chemicals Co.; Paterson, N.J., U.S.A.; Photonol RPHO-7149 and Photonol PHO-7155 commercially available from Henkel Corporation, Ambler; Pa., U.S.A.; Voronal R230-660 and Voronal R234-630 commercially available from Dow Chemical Co.; Midland, Mich., U.S.A.; Formred RT-315, Fomrez RET-190 and Fomrez RET-250 commercially available from Witco Corporation, Organics Division; New York, N.Y., U.S.A.; and the like.
Examples of the compound represented by the formula (II) include aldoses, ketoses, aldonic acids, soluble metal aldonates, polyalkoxyalkylene derivatives thereof, and the like. Specific examples thereof include D-erythrose, L-erythrose, threose, arabinose, ribose, lyxose, xylose, glucose, mannose, altrose, talose, galactose, idose, gulose, and corresponding aldonic acids, namely D-gluconic acid, D-mannonic acid, D-altronic acid, D-alloic acid; soluble metal aldonates such as potassium gluconate; their adducts with the alkylene oxide such as ethylene oxide and/or propylene oxide; and the like.
Examples of the compound represented by the formula (III) include alkylene oxide such as ethylene oxide and/or propylene oxide adducts of glucose, &agr;-methylglucoside, and &bgr;-methyl-D-alloside.
Each of the compounds represented by the formulas (I) to (III) can be used alone or in admixture.
The total number of —CH
2
CHYO— units in the compound A is 1 to 100. The total number of —CH
2
CHYO— units is preferably 6 to 80, more preferably 10 to 40, from the viewpoints of discharging ability and printed density. It is preferable that the total number of —CH
2
CHYO— units is not less than 1, from the viewpoints of obtaining excellent discharging ability and high printed density, which are characteristics in the present invention, and that the total number of —CH
2
CHYO— units is not more than 100, from the viewpoint of giving a water-based ink composition appropriate viscosity.
In order to improve the discharging ability of the water-based ink composition, it is desired to use a compound A, the surface tension of which is 40 to 70 mN/m, preferably 50 to 70 mN/m in a 10% by weight aqueous solution.
The content of the compound A in the water-based ink composition is not limited to specified ones. It is desired that the content is 0.1 to 50% by weight, preferably 0.5 to 25% by weight, more preferably 1 to 10% by weight. It is preferable that the content of the compound A is not less than 0.1% by weight, from the viewpoint of giving a water-based ink composition a good balance of viscosity, discharging abilit
Nagashima Shigeki
Nakano Yukihiro
Bell Mark L.
Birch & Stewart Kolasch & Birch, LLP
Faison Veronica F.
Kao Corporation
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