Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1997-08-28
2001-08-14
Morris, Terrel (Department: 1771)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S056000, C524S058000, C524S522000, C524S523000, C106S031600, C106S031470, C260SDIG031
Reexamination Certificate
active
06274646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink composition containing a specific resin. More particularly, the present invention relates to an ink composition suitable for ink jet recording.
2. Background Art
Sure fixation of recording print onto a recording medium is an important property required of the ink composition. In recent years, coated papers and the like have been used as a recording medium. The surface of the recording medium has been rendered very smooth for imparting a feel of high grade. There is a demand for an ink composition which can yield a print having satisfactory abrasion resistance even on a recording medium having such a smooth surface.
Further, in recent years, ink jet recording has become used widely. In the method, droplets of an ink composition are ejected and deposited onto a recording medium such as paper. The ink jet recording method can realize high speed printing of an image having a high resolution and a high quality by means of a relatively inexpensive apparatus. The coated papers with a smoothed surface are extensively used as a recording medium from the viewpoint of adding a further value to the record. Therefore, for ink compositions for ink jet recording, realizing print with good fixation on such a recording medium is an important property to be required.
SUMMARY OF THE INVENTION
The present inventors have now found that addition of a specific resin to an ink composition can improve the fixation of print onto a recording medium. The present invention has been made based on such finding.
Thus, according to one aspect of the present invention, there is provided an ink composition comprising at least a pigment, a resin, an organic solvent, and water, wherein the resin is a copolymer comprising- units represented by the following formulae (I), (II), and (III):
DETAILED DESCRIPTION OF THE INVENTION
The ink composition of the present invention is used for recording methods using an ink composition. The recording methods using an ink composition include, for example, ink jet recording, recording using writing implements, such as pens, and other various printing methods. In particular, the ink composition of the present invention is preferably used for ink jet recording.
The ink composition of the present invention can yield print with good fixation onto a recording medium. In particular, it can realize print with high fixation onto recording media with a very smooth layer provided on the surface thereof, such as coated papers.
An ink composition to be used in an ink jet recording method wherein the ink composition is ejected through very fine nozzles should meet property requirements including that it does not clog the fine nozzles and no precipitate is created around the nozzle. The ink composition of the present invention, even when used in ink jet recording, can offer an advantage that it is less likely to cause clogging and does not create any precipitate around the nozzles.
The ink composition of the present invention basically comprises a pigment, a resin, an organic solvent, and water. The resin contained in the ink composition of the present invention is a copolymer comprising units represented by the formulae (I), (II), and (III). In the formula (I), the butyl group located in the side chain is preferably n-butyl. This resin has an acid value of 50 to 100, preferably 50 to 70, and a molecular weight of 10,000 to 20,000, preferably 12,000 to 16,000. According to a preferred embodiment of the present invention, in this copolymer, the ratio of the unit represented by the formula (I) to the unit represented by the formula (II) to the unit represented by the formula (III) is preferably (15 to 30) (55 to 85): (5 to 15), more preferably (20 to 25): (60 to 75): (5 to 10). The acid value and the molecular weight are in the above respective ranges realize better fixation. Further, the ink composition containing the resin having an acid value and a molecular weight falling within the above respective ranges effectively prevent the clogging and the creation of a precipitate in ink jet recording. According to a preferred embodiment of the present invention, the copolymer is a random copolymer.
The copolymer may be produced, for example, by providing butyl acrylate, methyl methacrylate, and acrylic acid as monomers and copolymerizing the monomers by conventional suspension polymerization, continuous bulk polymerization, solution polymerization or other methods. More specifically, dissolution of the monomers in a solvent followed by heat polymerization in the presence of a polymerization initiator, such as azoisobutyronitrile, that is, radical polymerization, permits a contemplated product to be surely and simply produced.
Regarding the pigment added to the ink composition of the present invention, inorganic and organic pigments are usable without any particular limitation. Examples of the inorganic pigment include, in addition to titanium oxide and iron oxide, carbon blacks produced by known processes, such as contact, furnace, and thermal processes. Examples of the organic pigment include azo pigments (including azo lake, insoluble azo pigment, condensed azo pigment, and chelate azo pigment), polycyclic pigments (for example, phthalocyanine, perylene, perinone, anthraquinone, quinacridone, dioxazine, thioindigo, isoindolinone, and quinophthalone pigments), dye chelates (for example, basic dye chelates and acid dye chelates), nitro pigments, nitroso pigments, and aniline black.
The amount of the pigment added to the ink is preferably about 0.5 to 25% by weight, more preferably about 2 to 15% by weight.
According to a preferred embodiment of the present invention, preferably, the pigment is added, to the ink, in the form of a pigment dispersion prepared by dispersing the pigment in an aqueous medium with the aid of a dispersant or a surfactant. Preferred dispersants usable herein include dispersants commonly used in the preparation of pigment dispersions, for example, polymeric dispersants.
Preferred examples of dispersant or surfactants usable herein include polyacrylic acid, polymethacrylic acid, acrylic acid/acrylonitrile copolymer, vinyl acetate/acrylic ester copolymer, acrylic acid/alkyl acrylate copolymer, styrene/acrylic acid copolymer, styrene/methacrylic acid copolymer, styrene/acrylic acid/alkyl acrylate copolymer, styrene/methacrylic acid/alkyl acrylate copolymer, styrene/&agr;-methylstyrene/acrylic acid copolymer, styrene/&agr;-methylstyrene/acrylic acid/alkyl acrylate copolymer, styrene/maleic acid copolymer, vinylnaphthalene/maleic acid copolymer, vinyl acetate/ethylene copolymer, vinyl acetate/fatty acid vinylethylene copolymer, vinyl acetate/maleic ester copolymer, vinyl acetate/crotonic acid copolymer, and vinyl acetate/acrylic acid copolymer.
According to a preferred embodiment of the present invention, the weight-average molecular weight of the copolymer is preferably about 3,000 to 50,000, more preferably about 5,000 to 30,000, most preferably about 7,000 to 15,000.
The amount of the dispersant added may be such that the pigment can be stably dispersed without sacrificing the other effects of the present invention. According to a preferred embodiment of the present invention, the amount of the dispersant added is preferably about 1:0.06 to 1:3, more preferably about 1:0.125 to 1:3, in terms of pigment to dispersant ratio.
Specific examples of organic solvents added to the ink composition of the present invention include high-boiling organic solvents. The high-boiling organic solvent serves to prevent the ink composition from being concentrated due to evaporation, thus preventing clogging of a recording head. Preferred examples of high-boiling organic solvents include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, and trimethylolpropane; alkyl ethers of polyhydric alcohols, such as ethylene gly
Adachi Kazumi
Okamoto Naoki
Takemoto Kiyohiko
Tanaka Naoki
Waki Minoru
Guarriello John J.
Ladas & Parry
Mikuni Color Ltd.
Morris Terrel
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