Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-08-29
2004-05-18
Egwim, Kelechi C. (Department: 1713)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031600, C106S031650, C106S031860, C106S031890, C106S031310, C524S376000, C524S377000, C524S378000
Reexamination Certificate
active
06736887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a water-based ink. More specifically, the present invention relates to a water-based ink which is less likely to cause nozzle clogging, thereby imparting high print quality.
2. Discussion of the Related Art
In general, when characters are written with an ink on paper or printed with a printer, high quality is required for the characters.
Causation for lowering the print character quality includes feathering which is caused by spreading the ink along with fibers constituting paper, blotting, lowering of the drop directionality in an inkjet recording process, and the like.
For the purposes of reducing feathering and blotting, there has been proposed a water-based ink containing an alkylene oxide adduct having a relatively high molecular weight. However, there is a defect in the water-based ink such that the drop directionality is poor, thereby leading to a defect of lowered print character quality. The accuracy for expelling an ink droplet to a desired portion means that fine ink droplets are accurately expelled from a nozzle to a desired portion, that is, the surface of a recording medium.
In general, since an ink for inkjet recording is poor in water resistance and scratch and rub resistance, there has been proposed to use an aqueous dispersion of fine polymer particles containing a colorant to improve these properties. However, since the aqueous dispersion of fine polymer particles containing a colorant has film-forming property upon drying, there arise some defects such that dried substances are generated on the periphery of the nozzles, whereby the drop directionality is lowered.
In addition, in order to improve the drop directionality in generally used water-based ink as well as the water-based ink comprising an aqueous dispersion mentioned above, there have been proposed a water-based ink containing a surfactant having a long alkyl chain and a large number of moles of an alkylene oxide added, and showing a specific cloud point, such as polyethylene glycol lauryl ether (Japanese Patent Laid-Open No. Sho 60-32866); a water-based ink comprising a surfactant having a specific HLB value, such as polyoxyethylene nonylphenyl ether (Japanese Patent Laid-Open No. Hei 4-239067), and the like. Also, there has been proposed a water-based ink containing an additive such as polyalkylene oxide alkyl ether having a short alkyl chain and a small number of moles of an alkylene oxide added (Japanese Patent Laid-Open No. Sho 56-32566).
However, there are some defects in these water-based inks comprising an aqueous dispersion of fine polymer particles containing a colorant, such that the ink is spread along the fibers constituting paper to cause feathering or blotting when the surfactant or the additive is contained in an amount necessary for improving the drop directionality, so that print character quality is lowered, and print density is lowered, since surface tension of the ink is lowered.
An object of the present invention is to provide a water-based ink which is excellent in print density and print durability, has high print character quality, and is excellent in dry resistance and makes a water-fast print.
Another object of the present invention is to provide a water-based ink for inkjet recording which has excellent jetting stability and drop directionality.
These and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
The present invention is directed to a water-based ink comprising an aqueous dispersion of fine polymer particles containing a colorant, and at least one polyalkylene oxide derivative selected from the group consisting of the compounds represented by the following formulae:
R
1
O—(CH
2
CH
2
O)
a
—H (I)
H—(OCH
2
CH
2
)
b
—O—R
2
—O—(CH
2
CH
2
O)
c
—H (II)
R
3
O—(CH
2
CH
2
O)
d
—(CH
2
CH(CH
3
)O)
c
—H (III)
H—(OCH
2
CH
2
)
f
—(OCH
2
CH(CH
3
))
g
—O—R
4
—O—(CH
2
CH(CH
3
)O)
h
—(CH
2
CH
2
O)
i
—H (IV)
wherein each of a and d is independently a number of 10 to 40; each of b and c is independently a number of 5 to 20; e is a number of 1 to 3; f is a number of 5 to 20; each of g and h is independently a number of 0 to 4, wherein g+h is a number satisfying 1 to 4; i is a number of 5 to 20; each of R
1
and R
3
is independently a monovalent aliphatic group having 2 to 6 carbon atoms, a monovalent alicyclic group having 3 to 6 carbon atoms, or a monovalent aromatic group having 6 to 12 carbon atoms; R
2
is a divalent aliphatic group having 3 to 6 carbon atoms, a divalent alicyclic group having 3 to 6 carbon atoms, or a divalent aromatic group having 6 to 12 carbon atoms; R
4
is a divalent aliphatic group having 2 to 6 carbon atoms, a divalent alicyclic group having 3 to 6 carbon atoms, or a divalent aromatic group having 6 to 12 carbon atoms; and the oxyethylene chain and the oxypropylene chain in the formulae (III) and (IV) may be added in random or block forms.
DETAILED DESCRIPTION OF THE INVENTION
Preferable aqueous dispersions of fine polymer particles containing a colorant include an aqueous dispersion of fine polymer particles containing a hydrophobic dye and an aqueous dispersion of fine polymer particles containing a pigment. Among them, the aqueous dispersion of fine polymer particles containing a pigment, especially an organic pigment or carbon black, is more preferable.
The polymer used in the aqueous dispersion of fine polymer particles containing a hydrophobic dye or pigment includes vinyl polymers, polyesters, polyurethanes, and the like. Among the polymers, the vinyl polymers are preferable.
A preferable vinyl polymer includes a polymer prepared by copolymerizing a monomer composition comprising (a) at least one vinyl monomer selected from the group consisting of acrylic acid esters, methacrylic acid esters and styrenic monomers; (b) a polymerizable unsaturated monomer having a salt-forming group; and (c) a monomer copolymerizable with the vinyl monomer and the polymerizable unsaturated monomer having a salt-forming group.
The vinyl monomer includes acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, n-octyl acrylate and dodecyl acrylate; methacrylic acid esters such as methyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate; and styrenic monomers such as styrene, vinyltoluene and 2-methylstyrene.
The unsaturated monomer having a salt-forming group includes cationic monomers having a salt-forming group and anionic monomers having a salt-forming group.
The cationic monomers having a salt-forming group include unsaturated tertiary amine-containing monomers, unsaturated ammonium salt-containing monomers, and the like. Among them, preferable examples include N,N-diethylaminoethyl acrylate, N-(N′,N′-dimethylaminoethyl) acrylamide, vinylpyridine, 2-methyl-5-vinylpyridine, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like.
The anionic monomers having a salt-forming group include unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, and the like. Among them, preferable examples include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and the like.
The monomer copolymerizable with the vinyl monomer and the polymerizable unsaturated monomer having a salt-forming group includes acrylamide monomers; methacrylamide monomers; hydroxyl group-containing monomers; macromers having a polymerizable functional group at one end such as silicone macromers, styrenic macromers, polyester macromers, polyurethane macromers, and poly(alkyl ether) macromers; and especially a macromer represented by the formula (V):
CH
2
═C(R
5
)COO(R
6
O)
p
R
7
(V)
wherein R
5
is hydrogen atom or a lower alkyl group; R
6
is a dival
Mizushima Ryuma
Tsutsumi Takehiro
Egwim Kelechi C.
Kao Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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