Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1997-07-10
2002-01-01
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S328000, C428S331000
Reexamination Certificate
active
06335085
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording sheet. More particularly, the present invention relates to an ink jet recording sheet which has excellent ink jet recording properties and has excellent gloss of the ink image-formed portions and the non-image-formed portions thereof.
2. Description of the Related Art
The recording by an ink jet printer is often utilized in many fields because printing noise is low, the recording can be affected at a high speed and full-colored images can be easily formed. As recording sheets for the ink jet printing system, wood-free paper sheets modified so as to enhance the ink absorption thereof, and coated paper sheets having a coating surface layer containing porous pigment particles are used. These conventional recording paper sheets mostly have a low surface gloss and a matted appearance. Currently, new types of ink jet recording sheets having a high surface gloss and good appearance are in demand.
Generally, as printing paper sheets having a high surface gloss, coated paper sheets having a high gloss and produced by coating a surface of a paper sheet substrate with a coating layer containing plate-crystalline pigment particles and optionally applying a calendering treatment to the coating layer and cast-coated paper sheet produced by coating a surface of a paper sheet substrate with a coating liquid, pressing the coating liquid layer against a mirror-finished surface of a heating drum and drying the coating liquid layer on the mirror-finished surface of the heating drum so as to transfer the mirror surface to the resultant coating layer, are used.
The cast-coated paper sheets are mostly used for high gloss printing, because they have higher surface gloss and surface smoothness than those of the usual calender-finished coated paper sheets, and thus render excellent printing effect. However, when the cast-coated paper sheets are used for the ink jet recording system, various difficulties occur.
A conventional cast-coated paper sheet is disclosed in U.S. Pat. No. 5,275,846. In this cast-coated paper sheet, a high gloss is obtained by transferring the mirror-finished drum surface of a cast-coater to a coating layer containing a pigment and a film-forming binder. This film-forming binder causes the resultant coating layer to be non-porous and thus to exhibit a significantly reduced ink absorption when the cast-coated paper sheet is used for the ink jet recording system. To enhance the ink absorption, it is necessary to make the coating layer porous, so that the resultant porous coating layer can easily absorb the ink. To enhance the porosity of the coating layer, it is necessary to reduce the film-forming property of the coating layer. When the content of the film-forming binder in the coating layer is reduced, the resultant cast-coated paper sheet exhibits a reduced gloss. Therefore, it is extremely difficult to obtain a cast-coated paper sheet having both a high gloss and a satisfactory applicability to the ink jet recording.
To solve the above-mentioned problem, Japanese Unexamined Patent Publication No. 7-89,220 discloses a cast-coated paper sheet, having both excellent gloss and superior ink absorption, usable for an ink jet recording system. The cast coated paper sheet is produced by undercoating a surface of a paper sheet substrate with a undercoat layer comprising, as principal components, a pigment and a binder, coating the undercoat layer surface with a coating liquid containing, as a principal component, a copolymeric resin produced by polymerizing at least two monomers having an ethylenically unsaturated bond and having a gloss-transition temperature of 40° C. or more, to form a cast-coating liquid layer, pressing the cast-coating liquid layer in wet condition, against a mirror-finished casting drum surface and drying the cast coating liquid layer on the casting drum surface to form a cast-coated layer.
Currently, due to the rapid speed of ink jet printers, the high precision of the printed images and the full colored images, the use of the ink jet printing system is spreading, and thus the ink jet recording sheets are required to have a high gloss and improved qualities of the received ink images, namely a high color density and clarity. For example, high gloss and image quality comparative with those of silver salt type photographic prints are required from the ink jet recording sheets. To meet with the requirements, the gloss and printing performance of the ink jet recording sheets must be further improved.
Japanese Unexamined Patent Publication No. 7-329,412 discloses an ink jet recording sheet in which a cationic compound is contained in a substrate and an ink-receiving layer. In this case, the cationic compound is used for the purpose of preventing migration or permeation of ink in the printed portions of the recording sheets. This publication is quite silent as to the gloss of the ink jet recording sheet.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ink jet recording sheet having excellent gloss of ink-image-formed portions and non image-formed portions, superior ink absorption and a satisfactory water resistance of images and capable of recording ink images with a high color density and clarity.
The above-mentioned object can be attained by the ink jet recording sheet of the present invention which comprises
a substrate sheet;
at least one ink receiving layer formed on at least one surface of the substrate sheet and comprising a pigment and a binder; and
at least one gloss layer formed on the ink receiving layer and comprising a polymer resin,
at least one cationic compound being impregnated in the substrate sheet or coated on at least one surface of the substrate sheet on which the ink receiving layer is formed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The ink jet recording sheet comprises a substrate sheet, at least one ink receiving layer formed on at least one surface of the substrate sheet and at least one gloss layer formed on the ink receiving layer.
There is no limitation to the type and dimensions of the substrate sheet. Usually, the substrate sheet is selected from paper sheets including acid paper sheets and neutralized paper sheets, synthetic paper sheets and air-permeable polymer films. Especially, the paper sheets are preferred for the substrate sheet.
In the ink jet recording sheet of the present invention, a cationic compound is impregnated in the substrate sheet or coated on a surface of the substrate sheet on which surface the ink receiving layer is arranged. The cationic compound usable for the present invention is not limited to a specific class of compounds as long as the compound molecule has a cationic moiety. To cause the cationic compound to be retained in or on the substrate sheet with a high efficiency, however, the cationic compound is preferably selected from cationic oligomers and polymers having a high molecular weight of, for example, 1000 or more. There is no specific upper limit to the molecular weight. To stop the cationic compound-containing coating solution having too high a viscosity, the upper limit of the molecular weight is preferably 1,000,000 or less.
The cationic compounds usable for the present invention include cationic resins (cationic polymeric compounds) and low molecular weight cationic compounds (cationic monomeric compounds), for example, cationic surface active compounds. To retain the cationic compounds on the substrate sheet such as paper sheet with a high efficiency, the cationic compounds are preferably selected from the cationic resins which may be practically used in the form of an aqueous solution or an aqueous emulsion. There is no limitation to the molecular weight of the cationic resins. In view of the ease of handling, coating and impregnating, however, the molecular weight of the cationic resins is preferably about 1000 to about 1,000,000.
Also, the cationic resin may be used in the form of cationic organic pigment particles which have been prepared by insolubilizing
Asano Shin-ichi
Kouro Takaaki
Mukoyoshi Shun-ichiro
Armstrong Westerman Hattori McLeland & Naughton LLP
Oji Paper Co. Ltd.
Schwartz Pamela R.
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