Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-12-16
2001-04-03
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...
C347S100000, C106S031430, C106S031750
Reexamination Certificate
active
06211265
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink set preferably used for ink jet recording.
2. Background Art
In ink jet recording, ink droplets are generated and ejected by static electricity-driven ejection, air pressure-driven ejection, piezoelectric device deformation-driven ejection, thermal bubble formation-driven ejection or the like and deposited onto recording paper. The water-base ink used in this method is prepared by dissolving or dispersing various dyes in water or an organic solvent.
In recent years, waterfastness on plain paper is required of the ink jet recording. In order to obtain a water-base ink that can yield an image having good waterfastness, various studies have been made on the addition of polyamines, including polyethyleneimine and modified polyethyleneimines, in combination with dyes to the ink.
For example, Japanese Patent Laid-Open No. 119280/1987 and Japanese Patent Publication No. 91495/1995 disclose, as a waterfast composition for ink jet recording, an ink containing a hydroxyethylated or hydroxypropylated polyethyleneimine and a dye component. As far as the present inventors know, however, the hydrophilicity of the polymer is so large that satisfactory waterfastness cannot be attained depending on degree of hydroxyethylation or hydroxypropylation of the polymer. This is because in the polymer of these documents about 50 to 95% by mole of the side chain is accounted for by a hydroxyethyl group or a hydroxypropyl group.
Japanese Patent Laid-Open Nos. 255876/1990, 26876/1990, and 188174/1991 disclose, as a waterfast water-base ink composition, a composition containing a polyamine, with a primary amino group, having a molecular weight of not less than 300, an anionic dye, a stability imparting agent, and a wetting agent.
Japanese Patent Laid-Open No. 305011/1995 discloses a method for imparting waterfastness to a water-base ink containing: a basic water-soluble polymer; an anion dye using a volatile base as a counter ion; and a buffer using a volatile base as a counter ion, wherein the dissociation constant of each base is regulated. In the water-base ink, when the ink is in the state of an ink liquid, the dissociation of a cationic polymer is suppressed. On the other hand, on paper, the volatile base is evaporated to allow a salt-forming reaction between the polymer and the dye to proceed, thereby imparting the waterfastness to the ink.
Japanese Patent Laid-Open No. 113743/1996 discloses, as a waterfast ink, a water-base ink containing an anion dye having an azo group, and an amino acid type polyamine or polyethyleneimine.
Further, Japanese Patent Laid-Open Nos. 167374/1989, 80470/1990, and 292275/1995 and Japanese Patent Publication Nos. 30268/1995 and 68462/1995 disclose an ink having improved waterfastness attained by using a polyamine dye prepared by combining a polyamine, such as polyethyleneimine, polyvinylamine, or polyallylamine, with an azo dye having a reactive functional group.
As far as the present inventors know, the above conventional inks can ensure given waterfastness, but on the other hand, the lightfastness is poor. In particular, in a full-color image formed using a plurality of inks, the presence of only one color having poor lightfastness results in a change in hue, which leads to extremely deteriorated quality of the color image. Thus, a higher level of lightfastness is required of the inks for a full-color image. For example, in the ink disclosed in Japanese Patent Laid-Open No. 113743/1996, utilization of a dye having a specific structure is indispensable. For this reason, the range of dyes which can be selected is so narrow that it is difficult to prepare inks having desired properties (for example, hue and density). In the inks for realizing a full-color image, it would be desirable that a wide variety of colorants could be used.
SUMMARY OF THE INVENTION
The present inventors have made studies on causes of a deterioration in lightfastness of the conventional inks. As a result, they have found that the primary amino group of the water-soluble cationic polymer contained in the ink has high reactivity, attacks the azo bond in azo dyes, and decomposes azo dyes. They have also found that the attack of the primary amino group deteriorates the storage stability of the ink.
Furthermore, the present inventors have now found that colorants having a certain structure, even when added, to the ink, in combination with a highly reactive water-soluble cationic polymer having a primary amino group, can realize an image having good lightfastness with maintaining high waterfastness derived from the addition of the polyallylamine. They have also found that these colorants are not decomposed upon being attacked by the primary amino group of the polyallylamine and has excellent storage stability. The present invention has been made based on such finding.
Accordingly, an object of the present invention is to provide an ink set that can realize a full-color image having both good waterfastness and lightfastness.
Another object of the present invention is to provide an ink set that suffers from neither discoloration nor decomposition of dyes and has good storage stability.
According to one aspect of the present invention, there is provided an ink set comprising at least a black ink, a yellow ink, a magenta ink, and a cyan ink, each of the inks comprising at least a colorant, a water-soluble cationic polymer having a primary amino group in its molecule, and water, the colorant consisting of a coloring materials) classified into categories of anthraquinone, indigoid, phthalocyanine, carbonium, quinoneimine, methine, quinoline, nitro, nitroso, benzoquinone, naphthoquinone, naphthalimide, and perinone coloring materials.
DETAILED DESCRIPTION OF THE INVENTION
Definition
As used herein, the terms “lower alkyl group” and “lower alkoxy group” refer to alkyl having 1 to 4 carbon atoms and alkoxy having 1 to 4 carbon atoms.
Ink set
The ink set according to the present invention basically comprises at least a black ink, a yellow ink, a magenta ink, and a cyan ink.
The inks of the ink set each comprise at least a colorant, a water-soluble cationic polymer having a primary amino group in its molecule, and water, the colorant consisting of a coloring material(s) classified into categories of anthraquinone, indigoid, phthalocyanine, carbonium, quinoneimine, methine, quinoline, nitro, nitroso, benzoquinone, naphthoquinone, naphthalimide, and perinone coloring materials.
The ink set 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. Particularly preferably, the ink composition according to the present invention is used in ink jet recording, especially ink jet recording for forming a full-color image.
(1) Colorants
Colorants contained in the inks of the ink set according to the present invention each should fall within the above categories. Further, the colorants are in the state of dissolution or dispersion in the inks and, after printing on a recording medium, give the print on the recording medium a black color or a chromatic color. According to the present invention, any colorant (coloring material) may be utilized so far as it has the above properties. This offers an advantage that the range of selectable colorants is very broad.
Colorants falling within the above categories do not have an azo bond in their molecule and, even when added, to an ink, together with a water-soluble cationic polymer having a primary amino group in its molecule cause neither discoloration of the ink nor the decomposition of the colorants during the storage of the ink. Further, the ink containing both the colorant falling within any one of the above categories and the water-soluble cationic polymer having a primary amino group in its molecule has a great advantage that an image can be realized which possesses e
Kitamura Kazuhiko
Ohta Hitoshi
Jagannathan Vasu
Ladas & Parry
Seiko Epson Corporation
Shosho Callie E.
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