Compositions: coating or plastic – Coating or plastic compositions – Marking
Patent
1996-09-18
1997-12-30
Klemanski, Helene
Compositions: coating or plastic
Coating or plastic compositions
Marking
106 3186, 106 3189, 106 3182, C09D 1102
Patent
active
057025100
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an aqueous ink of a pigment type, and more particularly to an aqueous ink of a pigment type capable of accomplishing the stability of jetting in ink jet printers and accomplishing printing without causing clogging, and to an ink jet recording method which uses the same.
BACKGROUND ART
For inks for printing and writing utensils, aqueous inks are used in many cases because of the easiness of their production and handleability. For example, due to the development and spread of computers of late years, printing apparatuses are also spread and aqueous inks are used popularly for such printing apparatuses. The ink jet recording technique that is one of typical recording techniques for printing apparatuses is a recording technique wherein ink droplets are expelled from a very small nozzle directly onto a recording medium to allow the ink droplets to impact to the recording medium thereby obtaining images including characters. Of late years, this technique is widely used because this technique has not only an advantage that the apparatus used is low in noise and good in operability but also an advantage that images can be colored easily and plain paper can be used as a recording medium. As techniques for jetting an ink, the piezo-electric technique which uses a piezo-electric element for a printing head and the thermal jet technique which uses a heater of a heating resistor element for a printing head are widely used for personal printers.
As inks used for the above-mentioned ink jet recording, inks of a dye type and pigment type are conventionally used. However, on the one hand the inks of a dye type are poor in water resistance and light resistance, and on the other hand the inks of a pigment type are poor in stability of jetting to cause a nozzle to be clogged, which are problems.
To solve the problem that causes a nozzle to be clogged with an ink, in the inks used for ink jet printers, generally a water-soluble dye that can be dissolved in water is used. However, by using a water-soluble dye, while the ink hardly clogs a nozzle, there are problems that the ink is poor in water resistance and light resistance and that, particularly in the case of a thermal jet technique, the dye is oxidized by excess heat at a printing head to cause the ink to be scorched easily onto the printing head.
Further, for the inks of a pigment type, in order to prevent the ink from clogging a nozzle, there have been proposed a method wherein a combination of a dispersant and a carbon black having a pH of 7 or over is used (Japanese Patent Application Laid-Open 4-189876), a method wherein a pigment is emulsified with a core material (Japanese Patent Application Laid-Open 5-9421), and a method wherein a pigment and insoluble resin particles are bonded with an organic silane coupling agent (Japanese Patent Application Laid-Open 5-65443), but they are not still satisfactory.
Therefore, an object of the present invention is to provide an aqueous ink of a pigment type capable of accomplishing the stability of jetting in ink jet printers as well as capable of accomplishing printing without causing clogging and excellent in water resistance and light resistance, and an ink jet recording method which uses the same.
DISCLOSURE OF INVENTION
The present inventors have made intensive research and have found that the above object can be attained by using a sulfite in an aqueous ink of a pigment type, leading to the completion of the invention.
That is, the present invention provides an aqueous ink of a pigment type comprising a pigment, water, a water-soluble solvent and a sulfite. The aqueous ink of a pigment type of the present invention is particularly suitable for use as an ink for an ink jet recording.
Further, the present invention provides an ink jet recording method in which the aqueous ink of a pigment type of the present invention is used, the method comprising jetting to a recording medium the aqueous ink of a pigment type of the present invention in a droplet form from a nozzle by
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Nawa Masayoshi
Sakai Kouichi
Yanagi Hideki
Yoshida Satoshi
Kao Corporation
Klemanski Helene
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