Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1996-04-19
2001-01-16
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C347S105000, C428S195100, C428S522000, C428S532000, C428S500000, C428S478200, C428S331000
Reexamination Certificate
active
06174611
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording medium and a recording method which can realize an image having excellent storage stability. More particularly, the present invention relates to an ink jet recording method which can realize an image having excellent storage stability and a recording medium suitable for the ink jet recording method.
2. Background Art
In an ink jet recording process, small droplets of an ink are ejected through various mechanisms and deposited on a recording medium to form ink dots. The ink jet recording process has advantages such as emission of no significant noise, high-speed printing, and ease of full color printing.
The storage stability of prints is an important property also for the ink jet recording method. A dye which is an organic material is generally used as a colorant in an ink composition for the ink jet recording method. Therefore, exposure of the dye to ultraviolet light or a highly active gas causes a possibility that the dye is decomposed resulting in a change in color tone. On the other hand, a recording medium carrying silica is used in the ink jet recording method. The silica has high specific surface area with a catalytic activity which may catalyze the oxidation of the dye.
Several methods for improving the storage stability of an image have been proposed. For example, Japanese Patent Laid-Open No. 87989/1982 discloses that the addition of a metal oxide, a metal chloride, or tannic acid to a recording layer results in improved light fastness in storage. Further, the addition of materials considered to be an antioxidant to a recording layer has been proposed. For example, Japanese Patent Laid-Open No. 61887/1986 discloses the addition of a polyallylamine derivative, Japanese Patent Laid-Open No. 146591/1986 discloses the addition of a hindered amine compound, Japanese Patent Laid-Open No. 154989/1986 discloses the addition of a hydrazide compound, and Japanese Patent Laid-Open No. 163886/1986 discloses the addition of a thiourea derivative, a thiosemicarbazide derivative, and a thiocarbohydrazide derivative.
On the other hand, some dyes have poor storage stability. In particular, dyes which, even when placed in an environment not directly exposed to light, undergo discoloration with the elapse of time are known in the art. Such dyes are considered to be decomposed by an oxidizing gas present in the air, for example, ozone.
SUMMARY OF THE INVENTION
We have now found that a combination of a recording medium having a specific composition with a dye which has been said to have poor storage stability can offer improved storage stability of an image.
Accordingly, an object of the present invention is to provide a recording medium, especially an ink jet recording medium, which can realize excellent storage stability of an image.
Another object of the present invention is to provide a recording method, especially an ink jet recording method, which can realize excellent storage stability of an image.
One aspect of the present invention provides a recording medium having a layer comprising silica and a binder, wherein the binder comprises a polymer component, 5 to 55% by weight of a polymer component of the binder is a styrene/butadiene latex, and 20 to 45% by weight of the styrene/butadiene latex is derived from a butadiene monomer.
Another aspect of the present invention provides a ink recording method comprising the step of carrying out recording on the above recording medium using an ink composition comprising a colorant of at least one dye selected from the group consisting of a stilbene azo dye, a triphenylmethane dye, and a xanthene dye.
A further aspect of the present invention provides an ink jet recording method comprising the step of ejecting droplets of an ink composition onto a recording medium to form ink dots on the recording medium,
wherein the ink composition comprising a colorant of at least one dye is selected from the group consisting of a stilbene azo dye, a triphenylmethane dye, and a xanthene dye,
wherein the recording medium is the above recording medium of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The recording medium according to the present invention has, preferably as a surface layer, a recording layer comprising silica and a binder. In the present invention, 5 to 55% by weight of a polymer component of the binder is a styrene/butadiene latex, and 20 to 45% by weight of the styrene/butadiene latex is derived from a butadiene monomer. Although components are primarily charged according to these proportions as a binder composition in the preparation method described below, they coincide with the proportions in % by weight of components constituting the polymer component of the binder in the dried recording layer in a final recording medium.
In the present invention, the presence of the specific styrene/butadiene latex as part of the binder in the recording layer can improve the storage stability of an image. In particular, a combination of the specific styrene/butadiene latex with a specific dye described below can realize marked improvement in storage stability of an image. While there is no intention of being bound by any particular theory, it is believed that the improvement in storage stability of an image is derived from the interaction between the dye in the ink composition and the binder in the recording layer. In particular, when the butadiene component content is high, two or more butadiene components are adjacent to each other or one another after polymerization and a plurality of aliphatic double bonds having a relatively high reactivity are possessed contributing to an deterioration in storage stability of an image.
Preferably, a water-soluble polymer is added as a component other than the styrene/butadiene latex of the binder. Preferred examples thereof include starches such as oxidized starch and esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; polyvinyl alcohol and derivatives thereof; polyvinyl pyrrolidone; casein; and gelatin. Among them, polyvinyl alcohol is particularly preferred.
Further, other components commonly used in binders may be added to the binder of the present invention. Specific examples of such components include aqueous resins such as a (meth)acrylate emulsion, a styrene/(meth)acrylate emulsion, and a vinyl acetate emulsion.
Silica as a pigment is incorporated into the recording layer of the recording medium according to the present invention. The silica is preferably synthetic silica, and examples thereof include synthetic silica such as noncrystalline silica and amorphous silica. In addition, silica gel, white carbon, and anhydrous silica described in Kagaku Binran: Ohyo Kagaku Hen (published on Oct. 15, 1986 by Maruzen Co., Ltd., edited by The Chemical Society of Japan), infra p. 256 may be preferably used. Among them, white carbon is particularly preferred.
While the ratio of the binder to the silica may be suitably determined, the ratio of the binder to the silica in the recording layer is preferably about 0.1 to 1, more preferably about 0.2 to 0.8.
The recording medium according to the present invention can be prepared by preparing a coating composition comprising the silica and the binder and coating the coating composition onto a substrate for a recording medium, for example, paper. The coating composition may be prepared by mixing the silica, the binder, and water together while stirring. The amounts of the silica and the binder may be determined depending on the composition of the final recording layer. In this context, consideration is preferably given to satisfactorily binding the silica to the substrate and, at the same time, preventing the destruction of a porous structure necessary for ink absorption. In addition, if necessary, pigment dispersants, water retaining agents, thickeners, antifoaming agents, preservatives, colorants, hydration preventives, wetting agents, fluorescent dyes, ultraviolet absorbers, cationic polymer electrolytes and
Iida Jun-ichi
Kobayashi Yukio
Kuroyama Yoshihiro
Midorikawa Hiroki
Onishi Hiroyuki
Ladas & Parry
Schwartz Pamela R.
Seiko Epson Corporation
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