Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-08-03
2004-06-01
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031860
Reexamination Certificate
active
06743284
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a printing ink composition, more specifically relates to a water-based printing ink composition suitable for ink-jet printing.
2. Description of Related Art
Ink-jet printing has been conducted on various ink-jet systems. These system include an electric control system in which electrostatic suction is utilized to eject ink, a pressure pulse system in which mechanical vibration or displacement of ink caused by a piezoelectric element is utilized to eject ink, and a thermal ink-jet system in which pressure produced by bubbles formed and grown by heat is utilized to eject ink. Under these systems, drops of ink are generated, and then, the drops of ink in part or in entirety are attached to printing mediums so as to print images thereon.
In such ink-jet printing, water-based ink is commonly used. The water-based ink comprises a water-based solvent (such as water or a mixture of water and a water-soluble organic solvent) and a coloring material (such as a water-soluble dye or pigment) dissolved or dispersed in the water-based solvent. Ink-jet printing can be conducted with good quality in the long term by using the water-based ink, on the condition that the water-based ink has appropriate properties (such as viscosity, surface tension, conductivity and density), that the properties of the ink do not change by heating so as to not form a precipitate, which causes clogging of a nozzle or an orifice of an ink-jet printer, and that the ink has high water resistance and high light resistance.
Recently, there has been a growing need to perform ink-jet printing with water-based ink on plain paper rather than on printing sheets designed specifically for ink-jet printing. However, conventional water-based ink is prone to spread over the plain paper and causes bleeding of ink where ink of different colors are arranged adjacently (hereinafter referred to as “color bleeding”). A number of proposals have been made to provide water-based ink that does not cause color bleeding even on plain paper in ink-jet printing. However, the proposed inks fall short of satisfying required image quality.
SUMMARY OF THE INVENTION
The invention has been developed to overcome the above-mentioned and other problems. According to an aspect of the invention, there is provided an ink composition comprising water, a coloring agent and at least two types of polyalkylene glycol alkyl ethers, each having at least one oxyalkylene in its polyoxyalkylene group, wherein at least one of the polyalkylene glycol alkyl ethers is polypropylene glycol n-butyl ether having three or more oxypropylenes in the molecule. It becomes possible to inhibit color bleeding when ink-jet printing with the ink composition of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As used herein, the prefix “poly” is used to denote compounds having one or more oxyalkylenes. Thus, unless otherwise indicated, the polyalkylene glycol alkyl ethers described herein include monooxyalkylene glycol alkyl ethers, such as ethylene glycol n-butyl ether; dioxyalkylene glycol alkyl ethers, such as diethylene glycol n-butyl ether; and polyoxyalkylene glycols having three or more oxyalkylenes.
A printing ink composition of the invention comprises water, a coloring agent, and at least two types of polyalkylene glycol alkyl ethers, each having at least one oxyalkylene in a polyoxyalkylene group, where at least one of the polyalkylene glycol alkyl ethers is polypropylene glycol n-butyl ether having at least three oxypropylenes in the molecule. Hereinafter, for brevity, the polyalkylene glycol alkyl ether having at least one oxyalkylene in the polyoxyalkylene group is referred to as “polyalkylene glycol alkyl ether,” whereas the polypropylene glycol n-butyl ether having at least three oxypropylenes in the molecule is referred to as “polypropylene glycol n-butyl ether.”
The coloring agent is used in an amount of 0.1 to 20% by weight, preferably 0.3 to 15% by weight and more preferably 0.5 to 10% by weight, based on the total weight of the printing ink composition. As the coloring agent, any dyes and pigments can be used alone or in combination. In particular, it is preferable to use water-soluble dyes including direct dyes, acid dyes, basic dyes and reactive dyes, among the dyes. It is also preferable to use inorganic pigments and organic pigments.
Representative examples of water-soluble dyes useful in the invention are C.I. Direct Black 17, 19, 32, 51, 71, 108, 146, 154 and 168, C.I. Direct Blue 6, 22, 25, 71, 86, 90, 106 and 199, C.I. Direct Red 1, 4, 17, 28, 80, 83 and 227, C.I. Direct Yellow 12, 24, 26, 86, 98, 132 and 142, C.I. Direct Orange 34, 39, 44, 46 and 60, C.I. Direct Violet 47 and 48, C.I. Direct Brown 109, C.1. Direct Green 59, C.I. Acid Black 2, 7, 24, 26, 31, 52, 63, 112 and 118, C.I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 113, 117, 120, 167, 229 and 234, C.I. Acid Red 1, 6, 32, 37, 51, 52, 80, 85, 87, 92, 94, 115, 181, 256, 289, 315 and 317, C.I. Acid Yellow II, 17, 23, 25, 29, 42, 61 and 71, C.I. Acid Orange 7 and 19, C.I. Acid Violet 49, C.I. Basic Black 2, C.I. Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28 and 29, C.I. Basic Red 1, 2, 9, 12, 13, 14 and 37, C.I. Basic Violet 7, 14 and 27, and C.I. Food Black 1 and 2.
The above-mentioned dyes are suitable for ink-jet printing and offer good performance with great clarity, high water solubility, high stability and high light resistance. However, the dyes useful in the present invention are not limited to the above.
Representative examples of inorganic pigments useful in the invention are carbon black, titanium oxides, and iron oxides.
Representative examples of organic pigments are azo pigments (such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments), polycyclic pigments (such as phtalocyanine pigments, perylenes and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments), lake pigments (such as base dye lakes, and acid dye lakes), nitro pigments, nitroso pigments, and aniline black daylight fluorescent pigments.
It should also be noted that the pigment useful in the invention is not limited to the above. For example, it is possible to use any other pigment capable of being dispersed in a water phase, or to use pigments of which the surface has been treated with a surfactant or a polymeric dispersing agent (such as graphite carbon).
In the case of using pigments as the coloring agent, the printing ink composition may be provided by dispersing the pigment in a mixture of the purified water and the polyalkylene glycol alkyl ethers with a dispersing agent according to a conventional method, for example, disclosed in Japanese Laid-Open Patent Publication No. 62-101672, which is herein incorporated by reference. Generally, 0.01 to 20% by weight of the dispersing agent is added into the mixture, based on the total weight of the printing ink composition. Other additives may be added, if necessary.
Typical examples of dispersing agents are polymeric dispersing agents or surfactants as disclosed in Japanese Laid-Open Patent Publication No. 62-101672. Any combination of the polymeric dispersing agents and/or the surfactants as well as one of them alone can be used.
Representative examples of polymeric dispersing agents useful in the invention are gelatin, proteins (such as albumin), natural gum materials (such as gum arabic and gum tragacanth), glucosides (such as saponin), cellulose derivatives (such as methyl cellulose, carboxycellulose and hydroxymethyl cellulose), natural polymers (such as lignosulfonates and shellac), anionic polymers (such as polyacrylates, salts of styrene/acrylate copolymers, salts of vinylnapthalene/acrylate copolymers, salts of styrene/maleate copolymers, salts of vinylnapthalene/maleate copolymers, salts of b-napthalene sulfonic formalin condensates and phosphates), and non-ionic polymers (such as polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene gly
Fujioka Masaya
Norimatsu Takahiro
Taniguchi Akihiko
Brother Kogyo Kabushiki Kaisha
Faison Veronica F.
Wood Elizabeth D.
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