Stock material or miscellaneous articles – Composite – Of carbohydrate
Reexamination Certificate
1999-03-03
2001-05-29
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of carbohydrate
C428S195100, C428S211100, C428S412000, C428S481000, C428S507000, C428S509000, C428S522000, C428S535000
Reexamination Certificate
active
06238804
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording medium having a coating for absorbing aqueous dye-based inks. The coating comprises a blend of cellulose ether(s) and stilbene optical brightener(s).
2. Brief Description of the Related Art
The present invention relates to coated ink jet recording media, such as papers and films, which can be color imaged with aqueous dye-based inks from ink jet printers. By “aqueous dye-based inks’ as used herein, it is meant ink compositions containing a water-soluble dye, wherein the solvent or carrier liquid is primarily water. In addition to water and dyes, the ink may contain pigments, organic solvents, humectants, detergents, thickeners, preservatives, and the like. The ink jet recording media of this invention are coated with an ink absorbent composition. By an “ink absorbent composition or coating” as used herein, it is meant a composition or coating which absorbs aqueous-dye based inks.
In order to provide high quality color images, ink jet recording media are typically coated with an ink absorbent composition. During imaging or printing with ink jet printers, the ink absorbent coating absorbs the aqueous dye-based ink quickly so that the ink can dry quickly. Ink absorbent (or ink receptive) coatings are known in the art and typically comprise a hydrophilic polymeric material that is soluble in water and swells upon exposure to water. Suitable hydrophilic polymeric materials include, for example, poly(vinyl alcohol), cellulose ethers, cellulose esters, poly(vinyl pyrrolidone), gelatins, poly(vinyl acetate), starch, poly(acrylic acids), poly(ethylene oxide), proteins, hydroxypropyl cyclodextrin, poly(2-ethyl-2-oxazoline), alginates, water-soluble gums, and the like.
It is sometimes desirable to add certain optical brighteners to certain polymeric coatings on ink jet recording media in order to brighten the coatings.
For example, Nikoloff, U.S. Pat. No. 5,660,622 discloses a coating composition for ink jet recording sheets. The composition contains a mixture of hydrated amorphous synthetic silica, synthetic binder, cationic agent, leveling-flow modifier, dispersing agent, optical brightener, and water. In addition, the patent states that the coating may also include titanium dioxide pigment and/or a viscosity modifier. The patent discloses that the water-dispersible synthetic binder may be an acrylic prepolymer or polyvinyl alcohol (PVA), and the viscosity modifier may be alginates, carboxyl methyl cellulose, hydroxyl methyl cellulose, or polyacrylates. The patent states that the preferred optical brightener material includes a stilbene yellow base and is preferably in the coating composition at a weight percent range of 0.2 to 2%.
Cahill et al., U.S. Pat. No. 5,766,398 and Brault et al., U.S. Pat. No. 5,795,425 disclose processes for making protected, distortion-free, full-color ink jet images for use on large format posters, billboards, and the like. The patents disclose that the ink receptive layer on the receptor element may be prepared from a variety of hydrophilic aqueous ink absorptive coating materials. In addition to the polymeric or resin components, the patents disclose that the ink receptive layer typically contains other added components such as a dye mordant, a surfactant, particulate material, a colorant, ultraviolet absorbing materials, organic acids, an optical brightener, and the like. The patent discloses that optical brighteners which may be used to enhance the visual appearance of the imaged layer may be any conventional, compatible optical brightener, e.g., optical brighteners marketed by Ciba-Geigy under the trademark of Tinopal®.
One particular problem with ink jet recording media coated with compositions containing cellulose ethers is that the media exhibit undesirable color shifts after the media have been imaged with a color image. By “color shifts”, it is meant that the color of the image changes over time. These color shifts are most noticeable on ink jet recording media having a magenta-colored image. When magenta ink is used to form the image, the image is initially a magenta (deep purplish red) color, but it often fades and appears hot pinkish over a relatively short period of time. It would be desirable to have ink jet recording media, where such magenta color shifts are minimized or eliminated. The present invention provides such ink jet recording media.
SUMMARY OF THE INVENTION
The present invention provides an ink jet recording medium comprising a substrate coated with an ink absorbent composition, comprising a blend of at least one cellulose ether and stilbene optical brightener, wherein no acrylic resin or polyvinyl alcohol is present in the composition. The coating comprises about 1% to about 10%, and more preferably 1 to 5%, by weight stilbene optical brightener. Transparent, translucent, matte and opaque plastic films, and papers can be used as substrates. Preferably, the plastic film comprises polyester, cellulose ester, polystyrene, polypropylene, polyvinyl acetate, polycarbonate, or mixtures thereof Preferably, the paper is a polyethylene-coated or clay-coated paper.
The ink jet recording medium of this invention is further characterized by having a &Dgr;E value of no greater than about 5, as measured according to CIE 1976 (L*a*b*) uniform color scale method, after the medium has been imaged with a magenta color-image. Further, the ink jet recording medium preferably has a whiteness value of at least about 95.
DETAILED DESCRIPTION OF THE INVENTION
The following Detailed Description (including the Examples set forth) is provided as an aid to those desiring to practice the present invention. It is not to be construed as being unduly limiting to the present inventive discovery, since those of ordinary skill in the art will readily recognize that the embodiments of the Inventors' discovery disclosed herein may be modified using standard techniques and materials known in the art without departing from the spirit or scope of the present inventive discovery.
The present invention relates to an ink jet recording medium having an ink absorbent coating which absorbs aqueous dye-based inks. The coating comprises a blend of at least one cellulose ether and stilbene optical brightener. Suitable cellulose ethers for use in this invention include, for example, methylcellulose, hydroxymethylcellulose, ethylcellulose, and hydroxyethylcellulose.
A variety of conventional optical brighteners are used to brighten textiles, paper, detergents, and plastics. Examples of optical brighteners include stilbene derivatives, styryl derivatives of benzene and biphenyl, bic(benzazol-2-yl) derivatives, coumarins, carbostyrils, naphthalamides, derivatives of dibenzothiophene-5,5-dioxide, pyrene derivatives, and pyridotriazoles.
However, for ink jet recording media coated with an ink absorbent composition comprising cellulose ether(s), it has been surprisingly found that not all optical brighteners are effective in substantially eliminating magenta color shifts. The present inventors have discovered that ink absorbent coatings comprising a blend of cellulose ether and stilbene optical brightener possess good color fidelity, and ink jet media coated with such ink absorbent coatings are substantially free from magenta color shifts after magenta color- imaging. Conventional printers, such as the Encad Novajet Pro ink jet, can be used to form the magenta-colored image on the media. By “stilbene optical brighteners”, it is meant stilbenes and their derivatives. The stilbene optical brighteners suitable for use in this invention are commercially available and Tinopal® SFP and SCP, available from Ciba-Geigy, are particularly preferred. These stilbene optical brighteners stabilize magenta ink dye and fluoresce, providing the media with a whiter and brighter appearance. As illustrated in the following examples, if another optical brightener is used in place of the stilbene optical brightener, significant magenta color shifts occur on the imaged medium.
The ink absorbent co
Atherton David
Glass Odette
Arkwright Incorporated
Birch & Stewart Kolasch & Birch, LLP
Schwartz Pamela R.
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