Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-03-25
2004-04-13
Shosho, Callie (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S555000
Reexamination Certificate
active
06720367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink composition suitable for ink jet recording.
2. Background Art
It is important that an image formed by an ink composition possesses good waterproofness and lightfastness and has no significant feathering or bleeding.
In order to realize good waterproofness, a combination of a cationic resin with an anionic dye has hitherto been used in the art.
For example, Japanese Patent Laid-Open No. 119280/1987 discloses an ink comprising a hydroxyethylated polyethylene-imine polymer and a dye component. This publication describes that the combination of the polyethylene-imine polymer with the dye component can develop waterproofness.
Japanese Patent Publication No. 91494/1995 discloses an ink composition comprising a hydroxyalkylated polyallylamine polymer and a dye. This publication describes that the combination of the primary amine with the dye can develop waterproofness.
For the above two inks, a further improvement in ensuring satisfactory waterproofness of the image is required because the polymer has been substituted by a highly hydrophilic hydroxyalkyl group.
Japanese Patent Laid-Open Nos. 255876/1990, 296876/1990, and 188174/1991 disclose an ink composition comprising a polyamine, having a primary amine group, with a molecular weight of not less than 300, an anionic dye, and a stabilizer. These publications describe that the combination of the primary amine with the anionic dye can develop waterproofness.
Japanese Patent Laid-Open No. 305011/1995 discloses a water-base ink comprising a basic, water-soluble polymer, an anionic dye with a volatile base as a counter ion, and a buffer with a volatile base as a counter ion. This publication describes that the volatile base inhibits the dissociation of the polymer in the ink and, on paper, the volatile base is evaporated to promote a salt formation reaction between the polymer and the dye, thereby developing waterproofness.
Japanese Patent Laid-Open No. 238783/1987 discloses an ink jet recording sheet containing a homopolymer of a diallylaminate and a monoallylaminate or a copolymer of the diallylaminate with the monoallylaminate. This publication describes that an insolubilizing reaction between the polymer and the dye is created on this recording medium to develop waterproofness.
For some of the above ink compositions, a further improvement in lightfastness is required. For example, in the case of ink compositions using polyethyleneimine, which is specifically described as the cationic resin in Japanese Patent Laid-Open Nos. 255876/1990, 296876/1990, and 188174/1991, this resin strongly attacks the dye, and, for example, when these inks are allowed to stand at a high temperature, this results in decomposition of the dye or accelerates the photodecomposition of the print to often render the lightfastness of the ink lower than that of the ink using the dye alone.
Japanese Patent Laid-Open No. 305011/1995 discloses a recording method using the recording medium containing a cationic resin. Since the ink composition disclosed in the publication is not waterproof, the waterproofness cannot be developed in an image when recording media other than the recording medium described in this publication are used.
For the printed image, what is further important is to prevent feathering or bleeding, especially color-to-color bleeding in the case there inks of two or more colors are used.
SUMMARY OF THE INVENTION
The present inventors have now found that an ink composition containing a cationic, water-soluble resin having a specific structure can realize an image possessing good waterproofness and lightfastness and having no significant feathering or bleeding. The present invention has been made based on such finding.
It is therefore an object of the present invention to provide an ink composition which can yield an image possessing good waterproofness and lightfastness and having no significant feathering or bleeding, especially no significant color-to-color bleeding.
Furthermore, it is an object of the present invention to provide an ink composition suitable for ink jet recording.
According to one aspect of the present invention, there is provided an ink composition comprising at least an alkali-soluble colorant, a water-soluble organic solvent, water, and a cationic, water-soluble resin,
the cationic, water-soluble resin comprising a repeating unit represented by the following formula (I):
wherein R
1
and R
2
which may be the same or different represent a hydrogen atom or a C
1-5
alkyl group, provided that R
1
and R
2
do not simultaneously represent a hydrogen atom: and
n is 0, 1, or 2.
DETAILED DESCRIPTION OF THE INVENTION
Ink Composition
The ink composition according to the present invention may 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 recording 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 contains basically alkali-soluble colorant, a water-soluble organic solvent, water, and a cationic, water-soluble resin, the cationic, water-soluble resin comprising a repeating unit represented by the formula (I).
According to the present invention, the cationic, water-soluble resin is stably dissolved in the ink composition. Once the ink composition deposits onto a recording medium, the cationic, water-soluble resin electrostatically interacts with a colorant, and, in addition, the resin also interacts with the recording medium. Therefore, the resin is stably fixed on the recording medium. It is believed that the fixation of the resin on the recording medium permits the colorant, together with the resin, to be fixed on the recording medium, thus imparting waterproofness to the printed image. It is also believed that an image having no significant feathering or bleeding is realized as a result of firm fixation of the colorant on the recording medium.
For the cationic, water-soluble resin used in the present invention, R
1
and R
2
in the formula (I) may be the same or different and represent a hydrogen atom or a C
1-5
alkyl group, preferably a methyl group. However, R
1
and R
2
do not simultaneously represent a hydrogen atom. Most preferably, R
1
and R
2
simultaneously represent a methyl group.
In the formula (I), n is 0, 1, or 2, preferably 1.
According to a preferred embodiment of the present invention, the average molecular weight of the cationic, water-soluble resin is preferably about 300 to 10,000, more preferably about 400 to 5,000, most preferably about 500 to 2,500.
According to a preferred embodiment of the present invention, the cationic, water-soluble resin may comprise units other than the repeating unit represented by the formula (I). This can improve properties of the cationic, water-soluble resin. Monomers for providing units which may be contained in the resin include ethylene, propylene, isobutylene, styrene, vinyl chloride, vinylidene chloride, vinyl alcohol, vinylamine, vinyl acetate, acrylic acid or acrylic esters (for example, lower alkyl esters), methacrylic acid or methacrylic esters (for example, lower alkyl esters), acrylonitrile, methyl vinyl ether, vinylpyrrolidone, allylamine, diallylamine, and sulfur dioxide. Although the amount of units, derived from these monomers, present in the cationic, water-soluble resin is not particularly limited, it is preferably not more than 70%, more preferably not more than 30%, in terms of the molar ratio. In the cationic, water-soluble resin, these units may be present in a block form or a random form.
According to a preferred embodiment of the present invention, the ink composition of the present invention may further comprise a water-soluble resin other than the cationic, water-soluble resin. The water-soluble resin other than the cationic, water-soluble resin is preferabl
Kitamura Kazuhiko
Ohta Hitoshi
Taniguchi Makoto
Seiko Epson Corporation
Shosho Callie
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