Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-03-14
2002-08-13
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S079000, C522S071000, C522S083000, C522S084000, C522S090000, C522S096000, C522S182000, C522S122000, C523S160000, C106S031130, C106S031600, C106S031650
Reexamination Certificate
active
06433038
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink composition for ink jet recording, and an ink jet recording method using the same.
2. Background Art
Ink jet recording is a printing method wherein droplets of an ink composition are ejected and deposited onto a recording medium, such as paper, to conduct printing. This ink jet recording method has a feature that images having high resolution and high quality can be printed at a high speed. In general, the ink composition used in the ink jet recording comprises an aqueous solvent as again component and, added thereto, a colorant component and a wetting agent, such as glycerin, for preventing clogging.
A component, capable of stably fixing a colorant onto a recording media, into the ink composition is required for printing of the water-base ink composition on papers, cloths and other recording media which are less likely to be penetrable by the ink composition, and plates, films and other recording media produced from metals, plastics and other materials, which are not penetrable by the ink composition, for example, phenol, melamine, vinyl chloride, acryl, and polycarbonate resins. In particular, in the case of printing, for example, on printed wiring boards, rapid drying and good chemical resistance are required of the ink composition.
In order to meet this requirement, an ink composition has been proposed which contains a component of which the molecular weight is increased upon ultraviolet irradiation (for example, Japanese Patent Laid-Open No. 216379/1991). An ultraviolet-curable ink composition comprising a colorant, an ultraviolet-curable curable material, a photopolymerization initiator and the like has also been proposed (for example, U.S. Pat. No. 5,623,001). The claimed advantage of these ink compositions and ink jet recording methods using the same is to yield images having improved quality through the prevention of feathering or bleeding of the ink composition on recording media.
In an ink jet recording method using the ink composition containing a component, of which the molecular weight is increased upon ultraviolet irradiation, the ink composition is deposited on a recording medium followed by ultraviolet irradiation. Upon ultraviolet irradiation, the photopolymerization initiator contained in the ink composition produces radicals or the like which induce polymerization of an oligomer and a monomer contained in the ink composition. This results in curing of the ink composition, permitting the colorant contained in the ink composition to be fixed onto the recording medium. The fixation of the colorant is considered to realize prints which have high coating strength, solvent resistance, and color density and, at the same time, have no significant feathering or bleeding and unevenness. This type of ink composition for ink jet recording is sometimes called a “photocurable ink composition for ink jet recording.”
Further, the prevention of a dye as a colorant from being separated, the improvement of scratch/rubbing resistance and printing reliability, the prevention of fathering or bleeding after printing, the enhancement of drying properties of the ink and other purposes, disclosed are an ink for ink jet recording, comprising two liquids, an ink composition containing a colorant and a reaction solution containing a polymerization initiator, and an ink jet recording method wherein printing is carried out using these two liquids on recording media (for example, Japanese Patent Laid-Open Nos. 186725/1993 and 218018/1996).
According to the ink for ink jet recording, comprising two liquids, one of the ink composition and the reaction solution contains a photopolymerization initiator or a photocurable resin. The claimed advantage of using two divided liquids, that is, the ink composition and the reaction solution, is to suppress a dark reaction to enable the storage of the ink composition and the reaction solution for a long period of time and, in addition, to realize prints having excellent lightfastness and heat resistance.
On the other hand, ink jet recording, which involves the formation of a white print on a recording medium, uses an ink composition containing a white pigment as a colorant component. White pigments used in this method include white inorganic pigments, such as oxides, sulfides, sulfates, carbonates and the like of zinc, lead, barium, titanium, and antimony. Titanium oxide is known as a white pigment possessing excellent covering power, coloring power, and chemical resistance.
Further, a nonaqueous white pigment ink composition containing a colorant having a specific particle diameter has been proposed (for example, Japanese Patent Publication No. 45663/1990). The claimed advantage of this ink composition is to realize good dispersibility of the ink composition and good printing stability and to prevent clogging of the recording head in the ink jet recording apparatus, by virtue of the specific particle diameter of the white pigment.
SUMMARY OF THE INVENTION
The present inventors have now found that, in a photocurable ink composition for ink jet recording, the use of a urethane oligomer and a monomer having a tri- or higher functional reactive group can significantly improve coating strength, chemical resistance, dispersion stability, and printing stability. The present inventors have further found that, in the white ink composition for ink jet recording, anatase titanium dioxide, when used as the colorant, can improve the dispersion stability and printing stability of the ink composition. The present inventors have further found that the use of anatase titanium dioxide, a photopolymerization initiator, an oligomer, and a monomer in the photocurable ink composition for ink jet recording can significantly improve, in addition to dispersion stability and printing stability, polymerization efficiency and coating strength. The present invention has been made based on such finding.
Accordingly, it is an object of the present invention to provide an ink composition for ink jet recording, capable of realizing good ink jet recording and good images, and to provide an ink jet recording method using this ink composition.
According to a first aspect of the present invention, there is provided a photocurable ink composition for ink jet recording, comprising at least a colorant, a urethane oligomer, a monomer having a tri- or higher functional reactive group, a photopolymerization initiator, and an aqueous solvent.
According to a second aspect of the present invention, there is provided a white ink composition for ink jet recording, comprising at least anatase titanium dioxide and an aqueous solvent.
According to a third aspect of the present, invention, there is provided a photocurable white ink composition for ink jet recording, comprising at least anatase titanium dioxide, a photopolymerization initiator, an oligomer, a monomer, and an aqueous solvent.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Ink Competition According to First Aspect of Invention
The photocurable ink composition for ink jet recording according to the first aspect of the present invention comprises at least a colorant, a urethane oligomer, a monomer: having a tri- or higher functional reactive group, a photopolymerization initiator, and an aqueous solvent. The ink composition according to the first aspect of the present invention has high storage stability, can realize stable printing in ink jet recording, and can yield images having excellent coating strength and chemical resistance. The reason why this advantage can be obtained has not been fully elucidated yet, the reason is believed to reside, in that the urethane oligomer has high compatibility with the monomer having a tri- or higher functional reactive group and can stably dissolve or disperse other ingredients constituting the ink composition.
Urethane oligomer
The ink composition according to the first aspect of the present invention contains a urethane oligomer. The urethane oligomer according to the present invention refers to an oligomer havin
Takemoto Kiyohiko
Tanabe Seiichi
Ladas & Parry
McClendon Sanza L.
Seidleck James J.
Seiko Epson Corporation
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