Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
2001-03-07
2002-05-14
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S216000, C428S334000, C428S336000, C428S511000, C428S512000, C428S513000
Reexamination Certificate
active
06387478
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to image receiving materials used for outputting color images with electrophotographic printers including laser printers.
BACKGROUND OF THE INVENTION
Color electrophotographic process is widely used in copy machines or computer printers because of its advantages such as dry processing, a high output speed and the capability with which the process can provide final images on general-purpose paper such as plain paper or quality paper.
When, however the process is applied to the reproduction of pictorial images such as portrait or landscape, general-purpose paper cannot behave desirably mainly as it produces prints with a poor surface gloss. In electrophotographic image formation, toner particles are fixed onto an image-receiving paper with the simultaneous application of heat and pressure during image fixing. In order to achieve a flat and smooth print surface with a sufficient level of gloss, toner particles must be embedded well into an image-receiving layer. JP-A-63-92965 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a method of providing a polymer layer to facilitate toner embedding on the surface of image-receiving materials. Further, JP-A-4-212168 describes a method of providing a polymer layer having a flow beginning temperature lying in a defined range.
However, those techniques have proved not to give a perfect solution to the present problems as the texture or structure of the base paper still tends to appear in the print surface, thus failing in realizing a flat and smooth surface similar to that of conventional photographic prints. Moreover, changes in the surrounding temperature and/or humidity often cause the sheet-formed image receiving material to curl, and sometimes cause toner images to crack.
As a countermeasure for such curl, U.S. Pat. No. 5,691,039 discloses a technique of providing a curl-balancing layer having a melting point note lower than 115° C. on the surface of a base paper opposite to the one on which a toner image receiving layer is formed. This technique can prevent the material from curling, but when the material is placed in highly humid atmospheres, then the base paper elongates by moisture absorption, leading sometimes toner images thereon, which cannot follow such dimensional change, to crack.
Such toner image cracking will be prevented by suppressing the dimensional change of the base material (substrate) due to changes in the surrounding atmospheric condition. The silver halide photographic industry has long been preventing the moisture absorption of paper by laminating polyethylene layers on the both surfaces of base paper. When such type of laminated material is applied simply to electrophotographic image formation, it has been confirmed that toner image tends to migrate onto the fixing means surface during thermal fixing. (Such phenomenon is often called toner offset.) To solve the toner offset problem, one can provide a toner image-receiving layer on such laminated material. JP-A-8-21645, for example, discloses image-receiving materials comprising a base paper both surfaces of which are provided with a thermoplastic resin layer, and a toner image-receiving layer superimposed on such resin layer Such structures have a drawback that a sufficiently high electrostatic field cannot be formed in the toner transfer gap at the toner transfer step, resulting in a poor image transfer. Moreover, at the subsequent fixing step, it is difficult to supply an ample amount of heat to the image-receiving layer as well as the toner image. As a result, the finished print lacks in a high surface gloss equivalent to that of conventional photographic prints.
SUMMARY OF THE INVENTION
This invention has been made by taking into consideration all the above-cited problems; the invention aims to provide color electrophotographic image receiving materials that exhibits a desirable toner transfer feature and that can make prints equivalent to conventional photographic prints as for color reproducibility and surface gloss. The invention also aims to provide color electrophotographic image receiving materials that are highly resistant to environmental changes and thus are free from curling and toner image cracking even when the surrounding atmospheric temperature and humidity change.
The above-cited problems have been solved by a color electrophotographic image receiving material comprising a substrate and a toner image receiving layer provided on at least one surface of said substrate, wherein said substrate comprises a base paper and a 5 to 30 &mgr;m thick resin layer having a water vapor permeability not higher than 30 g/(m
2
·24 hr) provided on the both surfaces of said base paper, said image receiving layer has a thickness of 3 to 50 &mgr;m, and the flow beginning temperature of said image receiving layer T
FR
and that of said toner T
FT
satisfy the following relationship:
T
FR
≦T
FT
+5
° C.
(1)
In the color electrophotographic image receiving material of the invention, the flow beginning temperature of said image receiving layer should preferably be lower than the melting point of said resin layer. And, said resin layers should preferably contain polyethylene with a density between 0.94 and 0.97 g/cm
3
and have a thickness between 5 and 20 &mgr;m. Further, it is preferred to provide, between said resin layer and said image receiving layer, an intermediate layer that can adhere to both of said resin layer and said image receiving layer.
DETAILED DESCRIPTION OF THE INVENTION
A more detailed description on the color electrophotographic image receiving material of the invention will follow.
The color electrophotographic image receiving material of the invention has a toner image receiving layer on at least one surface of a substrate. The characteristics of the material lie in that said substrate consists of a base paper and a resin layer provided on both surfaces of said base paper, said resin layer having a thickness between 5 and 30 &mgr;m and having a water vapor permeability not higher than 30 g/(m
2
·24 hr) wherein the flow beginning temperature of said image receiving layer T
FR
and that of said toner T
FT
satisfy the above-cited formula (1).
The base paper used for the color electrophotographic image receiving material of the invention may consist of any type of paper provided that it can stand the fixing temperature and has practically acceptable levels of smoothness, whiteness, slipping and frictional property, anti-static property and surface deformation after fixing. Generally speaking, papers and synthetic polymer films used for photographic substrates described in pp. 223 to 240 of
Fundamentals of Photographic Engineering—Silver Halide Photography
, edited by the Society of Photographic Science and Technology of Japan and published by Corona Publishing Co., Ltd. in 1979, are applicable. Practical examples include synthetic paper based on polyolefins or polystyrene, quality paper (wood free paper), art paper, coated paper, cast coated paper, those comprising natural pulp mixed with synthetic polymer fibers made of polyethylene, Yankee paper, baryta paper, wallpaper, backing paper, papers impregnated with synthetic resins or emulsions, synthetic rubber-impregnated paper, synthetic polymer-incorporated paper, cardboards and cellulose fiber paper. In order to achieve a favorable feel as photographic prints, the thickness of such base paper is preferably from 100 to 200 &mgr;m with a density between 0.9 and 1.2 g/cm
3
.
In the invention, the substrate comprising a base paper provided on each of its front and back surfaces with a resin layer In the case, where an image receiving layer is formed directly on the surface of the base paper, the texture or the rough structure of the base paper appears on the surface of the image receiving layer, which acts to lower the gloss of the toner image. According to the invention in which a resin layer is formed between the base paper and the image receiving layer, the outermost surface
Fuji Photo Film Co. , Ltd.
Nakarani D. S.
Sughrue & Mion, PLLC
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