Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-08-10
2003-08-05
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031470, C106S031580, C106S031600, C106S031770, C106S031860, C106S031870
Reexamination Certificate
active
06602333
ABSTRACT:
TECHNICAL FIELD
The present invention relates to ink sets for ink jet recording comprising a plurality of ink compositions each containing at least a colorant, a water-soluble organic solvent and water; a preparation process of these ink sets; and image recording method and recorded matter by using them. Particularly, the invention pertains to ink sets for ink jet recording having flowing characteristics or dynamic viscoelasticity at 20° C. controlled within a specific range, whereby they can exhibit good jetting stability, suppress fluctuations, among different colors, of an ink jetting amount with high accuracy, and provide a high-quality image; preparation process of these ink sets; and image recording method and recorded matter by using them.
BACKGROUND ART
Ink jet recording is a method of carrying out printing by jetting droplets of an ink composition (which may hereinafter be called “ink” simply) and allowing them to adhere to a recording medium such as paper. Since this printing method permits high-speed and convenient printing of a high quality image with a high resolution, it has recently come to be an image forming method substitutable for photography particularly in color printing.
It is the common practice to use an ink containing a colorant, a wetting agent such as glycerin and water for this ink jet recording method.
As the colorant used for the ink of ink jet recording method, water soluble dyes have so far been employed from the viewpoints of high quality of the produced image in chroma, color reproduction and the like of the colorant, a variety of coloring materials usable for the colorant, water solubility, and reliability such as anti-clogging property.
The water-soluble dyes are sometimes inferior in water resistance or light fastness, which leads to inferiority in water resistance or light resistance of the printed matter printed by an ink containing the water-soluble dye. In recent years, for overcoming this problem, use of pigments excellent in fastness such as water resistance and light fastness or water-insoluble or water-sparingly-soluble dyes is under investigation. Such pigments or dyes, different from water-soluble dyes, lack solubility in water so that they must be dispersed stably in water. As means for preventing precipitation of pigment particles or water-insoluble or water-sparingly-soluble dyes, thereby preventing clogging, known is a method of dispersing them in an aqueous medium by using various surfactants or dispersants such as water-based resins.
Ink jet recording is a method of discharging ink droplets from a fine nozzle, thereby recording letters and graphics onto the surface of a recording medium. Examples of ink jet recording which has been developed and industrialized include a method of recording letters and graphics on the surface of a recording medium by converting electric signals to mechanical signals through electrostrictive elements and intermittently ejecting an ink reservoired in a nozzle head portion; and a method of recording letters and graphics on the surface of a recording medium by rapidly heating an ink, which has been reservoired in a nozzle head portion, in the very vicinity of the discharging portion, thereby creating a bubble and intermittently discharging the ink by making use of the volumetric expansion caused by the bubble.
Inks used for such inject recording methods are required to have a good jetting property, be free from disorders in print due to satellites, permit good printing on various recording media, and have driving frequency characteristics permitting stable ink ejection at the nozzle head which makes use of an electrostrictive element.
Particularly, an ink jet ink which contains a pigment or a water-insoluble or water-sparingly-soluble dye does not have sufficient jetting stability, so that such an ink but having improved jetting stability is desired.
An ink jet ink which contains a pigment or a water-insoluble or water-sparingly-soluble dye has sometimes suffered a problem in long-term stability due to precipitation of a colorant.
On the other hand, examples of a method of using a microcapsule for an ink jet ink include a method disclosed in JP-B-62-95366 which comprises using, for a recording liquid, a microcapsule having, encapsulated therein, a dye ink contained in polymer particles; a method disclosed in JP-B-1-170672 which comprises using, as a recording liquid, a micro-encapsulated colorant obtained by dissolving or dispersing a colorant in a substantially water-insoluble solvent, emulsifying and dispersing the solution or dispersion in water by using a surfactant and then micro-encapsulating the emulsion in a conventional manner; a method disclosed in JP-B-5-39447 which comprises using, as a recording liquid, a microcapsule having, encapsulated therein, a solution or dispersion of a sublimable disperse dye in at least one of water, a water-soluble solvent and a polyester resin; and an aqueous ink composition disclosed in JP-B-6-313141 which comprises colored emulsion polymer particles and various water-based materials.
The above-described techniques are effective for improving water resistance, light fastness and storage stability of ink, but is accompanied with the problem in jetting stability, more specifically, ink droplets do not always jet out straight upon continuous printing.
The ink used for ink jet recording should be free from feathering upon printing on paper which is a medium to be printed, be dried quickly, permit uniform printing on the surface of any recording medium, and upon multicolor printing, be free from color-to-color intermixing. Here, feathering upon use of paper as a medium to be printed is a particular problem to be solved.
Upon industrialization of conventional inks, particularly, many of the inks using a colorant as a pigment, investigation has been conducted to maintain their printing quality by suppressing their penetration, thereby suppressing wetting of the paper surface by them and retaining ink droplets near the surface of paper. Inks having reduced wetness to paper, however, differ largely in a feathering degree, depending on the kind of paper. Particularly in recycled paper comprising various fiber components, feathering appeared owing to a difference in wet properties of the ink to the components. Such inks are accompanied with further problems that they need much drying time, which inevitably causes intermixing of adjacent colors upon multicolor printing, and that the pigment used as a colorant remains on the surface of paper to deteriorate scratch resistance.
There is an attempt to improve penetration of an ink to paper with a view to overcoming the above-described problems. Under investigation are addition of diethylene glycol monobutyl ether as described in U.S. Pat. No. 5,156,675, addition of “Surfynol 465” (manufactured by Nisshin Chemical Industry Co., Ltd.) as an acetylene glycol surfactant as described in U.S. Pat. No. 5,183,502, addition of both diethylene glycol monobutyl ether and “Surfynol 465” as described in U.S. Pat. No. 5,196,056. Diethylene glycol mono-n-butyl ether is known as butyl carbitol and it is described, for example, in U.S. Pat. No. 3,291,580. Use of an ether such as diethylene glycol for an ink is investigated in U.S. Pat. No. 2,083,372.
Particularly in an ink using a pigment as a colorant, glycol ether is used in combination therewith. Examples include use of triethylene glycol monomethyl ether as described in JP-A-56-147861 and use of an ether such as ethylene glycol, diethylene glycol or triethylene glycol as described in JP-A-9-111165.
Particularly when a pigment is used as a colorant, however, the resulting ink tends to involve a problem in jetting stability, for example, ink droplets do not jet out straight.
An ink set obtained by using in combination the above-described inks different in color has been proposed.
It is not possible to assert that an ink set equipped with a plurality of inks different in color having pigment particles dispersed on an aqueous medium is sufficient in jetting stability (property of an ink
Klemanski Helene
Ladas & Parry
Seiko Epson Corporation
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