Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-03-27
2001-08-07
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S161000, C523S201000, C526S306000
Reexamination Certificate
active
06271285
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink composition suitable for ink jet recording, and a fine particle of a polymer suitable for the ink composition for ink jet recording.
2. Background Art
Ink jet recording is a printing method wherein droplets of an ink are ejected and deposited onto a recording medium such as paper. The ink for the ink jet recording generally contains a water-soluble dye in water or a combination of water with an organic solvent. It is generally pointed out that an image obtained by the ink containing a water-soluble dye has poor waterfastness and lightfastness.
On the other hand, an ink prepared by dispersing a pigment in an aqueous medium has excellent waterfastness and lightfastness. In an image obtained by the ink containing a pigment as the colorant, however, the colorant is likely to be left near the surface of the recording medium. Therefore, unsatisfactory fixation of the colorant on the surface of the recording medium results in the formation of a print which, when the image is rubbed with, for example, a finger, causes the recording medium to be smeared with the pigment. Furthermore, when printed letters are marked with a highlight pen, this causes the printed image area to be smeared. Therefore, a print having a good touch and rubbing/scratch resistance cannot be provided. Addition of a resin to the ink composition has been proposed in order to improve the fixation of the colorant to the recording medium. This resin is considered to function as a binder to strongly fix the colorant onto the recording medium.
Conventional resin-containing ink compositions include, for example, an ink comprising a pigment and a resin emulsion dispersed in water (Japanese Patent Publication No. 1426/1987), a dispersion of a pigment in a water-insoluble, resin emulsion dispersion (Japanese Patent Laid-Open No. 157668/1980), an ink using an emulsion having a specific film-forming temperature (Japanese Patent Laid-Open No. 217088/1989), and an ink using a resin emulsion (Japanese Patent Laid-Open Nos. 60068/1991 and 18462/1992). Further, Japanese Patent Laid-Open Nos. 147859/1981 and 147860/1981 and Japanese Patent Publication No. 5703/1992 propose an aqueous dispersion type pigment ink using a polymeric dispersant and a water-soluble organic solvent.
Further, use of a core/shell resin particle comprising a core and a shell surrounding the core in an ink for ink jet recording has also been studied in the art. For example, Japanese Patent Laid-Open No. 299234/1991 proposes an ink comprising a fine particle of a polymer having a two-layer structure and having an average particle diameter of not more than 0.1 &mgr;m. The particle comprising a core polymer prepared by homopolymerization or copolymerization of a (meth)acrylic ester compound, a vinyl ester compound, a styrene compound, or an olefin compound and a shell polymer comprising a fluoropolymer. Japanese Patent Laid-Open No. 259869/1996 proposes use of an organic fine particle comprising a core of a polymer, having a high degree of crosslinking, such as a styrene/divinylbenzene polymer, and a shell having a surface-modifying property.
Japanese Patent Laid-Open No. 278479/1995 proposes use of a fine particle prepared by polymerization of a monomer containing not less than 5% by weight of a crosslinking monomer having in one molecule two or more groups having a polymerizable double bond and not less than 2% by weight of a hydrophilic monomer having a hydrophilic group.
However, some of the ink compositions containing the above resins have a viscosity rendering the ink composition unsuitable for ink jet recording. In addition, a head for ink jet recording, has a nozzle plate which is treated so as to be rendered water-repellent, permitting ink droplets to be easily ejected through nozzles. Some of the resin-containing ink compositions are likely to attach to the nozzle plate and to well wet the plate. This causes an ink droplet trajectory directionality problem or a failure of the nozzle to eject the ink. Further, due to the water-soluble property of the resin, the printed image has often poor waterfastness. Furthermore, evaporation of water in the ink increases the viscosity of the ink, leading to clogging of nozzles.
In addition, the fine particle of the polymer disclosed in Japanese Patent Laid-Open No. 278479/1995 contains not less than 5% by weight of a crosslinkable monomer, causing a high degree of crosslinking. This makes it impossible to provide a satisfactory film-forming property, resulting in unsatisfactory fixation of a printed image onto the recording medium. Therefore, the printed image has poor rubbing/scratch resistance.
SUMMARY OF THE INVENTION
The present inventors have now found that addition of a fine particle of a polymer having high reactivity with a salt of a divalent metal can provide an ink composition having excellent properties, especially an ink composition which can realize an image having excellent rubbing/scratch resistance and water resistance, is free from a nozzle clogging problem, and enables stable printing. The present invention has been made based on such finding.
Accordingly, an object of the present invention is to provide an ink composition which can realize an image having excellent rubbing/scratch resistance and waterfastness, is free from a clogged nozzle problem, and enables stable printing.
According to one aspect of the present invention, there is provided an ink composition comprising at least a colorant, a fine particle of a polymer, a water-soluble organic solvent, and water,
the fine particle of the polymer having a film-forming property, a carboxyl group on its surface, and a reactivity with a divalent metal salt such that, when three volumes of 0.1% by weight of an aqueous emulsion of the fine particle of the polymer is brought into contact with one volume of an aqueous divalent metal salt solution having a concentration of 1 mol/liter, the time for the transmission of light at a wavelength of 700 nm to be decreased to 50% of the initial transmission is not more than 1×10
4
sec.
DETAILED DESCRIPTION OF THE INVENTION
Ink Composition
The ink composition according to the present invention can be used in recording methods using an ink composition. Recording methods using an ink composition include, for example, an ink jet recording method, a recording method using writing utensils, such as pens, and other various printing methods. In particular, the ink composition according to the present invention is preferably used in the ink jet recording method.
The ink composition according to the present invention comprises at least a colorant, a fine particle of a polymer, a water-soluble organic solvent, and water.
Fine Particle of Polymer
The fine particle of a polymer used in the present invention has a film-forming property and high reactivity with a divalent metal salt.
The term “film-forming property” means that, when a fine particle of a polymer is dispersed in water to prepare an aqueous emulsion and the water component in the aqueous emulsion is then evaporated, a resin film is formed. As with the aqueous emulsion, the ink composition with the fine particle of a polymer added thereto, when the solvent component is evaporated, forms a resin film. The resin film serves to strongly fix the colorant component in the ink composition onto the surface of a recording medium. It is believed that, by virtue of this, an image having excellent rubbing/scratch resistance and waterfastness can be realized.
Furthermore, the fine particle of a polymer used in the present invention has a carboxyl group on its surface and high reactivity with a divalent metal salt. The fine particle of a polymer has a reactivity with a divalent metal salt such that, when three volumes of 0.1% by weight of an aqueous emulsion of the fins particle of the polymer is brought into contact with one volume of an aqueous divalent metal salt solution having a concentration of 1 mol/liter, the time for the transmission of light at a wavelength of 700 n
Hoshino Futoshi
Kaneko Masatoshi
Miyabayashi Toshiyuki
Takamatsu Yasushi
Yoshimura Toshihiro
Jagannathan Vasu
Ladas & Parry
Seiko Epson Corporation
Shosho Callie E
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