Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-11-22
2004-10-26
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...
C524S548000, C524S555000
Reexamination Certificate
active
06809128
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
Realization of images having good waterfastness and lightfastness and, at the same time, having no significant feathering or bleeding is important for printing of images using ink compositions.
In order to realize good waterfastness, as exemplified below, a combination of a cationic resin with an anionic dye has hitherto been used.
For example, Japanese Patent Laid-Open No. 119280/1987 discloses an ink comprising a hydroxyethylated polyethyleneimine polymer and a dye component. This publication describes that the combination of the hydroxyethylated polyethyleneimine polymer with the dye component can develop waterfastness. Japanese Patent Publication No. 91494/1995 discloses an ink comprising a hydroxyalkylated polyallylamine polymer and a dye. The claimed advantage of this ink is the development of waterfastness through the combination of the hydroxyalkylated polyallylamine polymer with the dye. In these two inks, howerver, since hydroxyalkyl groups having high hydrophilicity are contained in the polymer used, a further improvement is required to ensure satisfactory waterfastness of printed images.
Japanese Patent Laid-Open Nos. 255876/1990, 296878/1990, and 188174/1991 disclose ink compositions comprising a polyamine, with a molecular weight of not less than 300, having primary amino groups, an anionic dye, and a stability-imparting agent. These publications describe that the combination of the primary amino group with the anionic dye can develop waterfastness. Disadvantageously, however, the resins used in these publications strongly attack the dye. Specifically, according to studies conducted by the present inventors, for example, when this ink is allowed to stand at high temperatures, in some cases, the dye is decomposed or otherwise the photodecomposition of the print is accelerated to render the lightfastness lower than that of an ink containing only the dye. This tendency is significant in ink compositions containing some magenta dyes. In the case of ink compositions other than the magenta dye-containing ink compositions, the storage stability of ink compositions and the lightfastness and waterfastness of prints could be balanced by bringing the content of the primary amino group to not more than about 20% by mole based on the total content of the side chain group in the polymer. However, in the case of the ink compositions containing the specific magenta dye, this level of amount of the resin added is insufficient and cannot offer satisfactory waterfastness of printed images.
Japanese Patent Laid-Open No. 305011/1995 discloses a water-base ink comprising a basic water-soluble polymer, an anionic dye with the counter ion being a volatile base, and a buffering agent with the counter ion being a volatile base. This publication describes that, in the ink, the volatile base prevents the dissociation of the polymer and, after printing, the volatile base on paper is evaporated to allow a salt-forming reaction between the polymer and the dye to proceed, thereby developing waterfastness.
Japanese Patent Laid-Open No. 238783/1987 discloses an ink jet recording sheet comprising a homopolymer of an acid salt of diallylamine or an acid salt of monoallylamine or a copolymer of the acid salt of diallylamine with the acid salt of monoallylamine. The claimed advantage of this ink jet recording sheet is that an insolubilized reaction of the polymer with the dye takes place on the recording medium to develop waterfastness. In the recording method using the recording medium containing the cationic resin disclosed in this publication, since the ink per se does not have waterfastness, use of a recording medium other than described in the publication cannot develop the waterfastness in the printed image.
Further, the formation of images having no significant feathering or bleeding, especially the prevention of color-to-color bleeding involved in use of two or more color inks, is also important.
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 images having excellent waterfastness and lightfastness and, at the same time, having no significant feathering or bleeding. The present invention has been made based on such finding.
Accordingly, it is an object of the present invention to provide an ink composition which realize images having excellent waterfastness and lightfastness and, at the same time, having no significant feathering or bleeding, especially no significant color-to-color bleeding.
In particular, it is an object of the present invention to provide an ink composition which can be advantageously used 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,
said cationic water-soluble resin comprising repeating units (a) represented by formula (a) in formula (I) and repeating units (b1) represented by formula (b1) in formula (I) or repeating units (b2) represented by formula (b2) in formula (I):
wherein
R
1
and R
2
, which may be the same or different, each represent a C
1-5
alkyl group;
R
3
represents a hydrogen atom or a C
1-5
alkyl group; and
m and n are each 0, 1, or 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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. Particularly preferably, the ink composition according to the present invention is used in the ink jet recording method.
The ink composition according to the present invention basically comprises at least an alkali-soluble colorant, a water-soluble organic solvent, water, and a cationic water-soluble resin. In this case, the cationic water-soluble resin comprises repeating units (a) represented by formula (a) in formula (I) and repeating units (b1) represented by formula (b1) in formula (I) or repeating units (b2) represented by formula (b2) in formula (I).
The resin comprising units (a) and units (b1) will be hereinafter referred to as the “resin of the first embodiment,” and the resin comprising units (a) and units (b2) will be hereinafter referred to as the “resin of the second embodiment.”
Resin of First Embodiment
The ink composition comprising the resin of the first embodiment according to the present invention can realize images having no significant feathering or bleeding and, at the same time, having excellent waterfastness. Although the reason why this effect can be attained has not been fully elucidated yet, it is believed as follows. The cationic water-soluble resin of the first embodiment contained in the ink composition according to the present invention is stably in the state of dissolution in the ink composition. Upon the deposition of this ink onto a recording medium, the cationic water-soluble resin causes electrostatic interaction with the colorant. This resin also interacts with the recording medium and thus can be stably fixed onto the recording medium. The fixation of the resin onto the recording medium is considered to permit the colorant, together with the resin, to be fixed onto the recording medium, thereby imparting the waterfastness to printed images. In particular, even though the pH value of the recording medium is on alkaline side, good waterfastness can be realized. Further, it is considered that good fixation of the colorant onto the recording medium can realize images having no significant feathering or bleeding.
Further, the ink composition according to the present invention can realize images having excellent lightfastness. Although the reason why the ink composition can provid
Kitamura Kazuhiko
Ohta Hitoshi
Seiko Epson Corporation
Shosho Callie
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