Record receiver having plural interactive leaves or a colorless – Having plural interactive leaves
Reexamination Certificate
1998-12-23
2001-05-15
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having plural interactive leaves
C428S304400, C428S321500, C428S913000, C428S914000
Reexamination Certificate
active
06232268
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thermal transfer image-receiving sheet. More particularly, it relates to a thermal transfer image-receiving sheet having a dye-receptive layer of which the texture is similar to that of a so-called “plain papers.”
A thermal transfer sheet comprising a substrate sheet and a dye layer provided on one surface of the substrate sheet has hitherto been used in an output printer for computers and word processors by a thermal sublimation dye transfer system. This thermal transfer sheet comprises a beat-resisting substrate sheet and a dye layer formed by coating an ink comprising a mixture of a binder with a sublimable dye on the substrate sheet and drying the resultant coating. Heat is applied to the thermal transfer sheet from the back surface thereof to transfer a number of color dots of three or four colors to a material on which an image is to be transferred, thereby forming a full color image. Since the colorant used is a dye, the image thus formed has excellent sharpness and transparency and high reproduction and gradation of intermediate colors, which enables a high-quality image comparable to a conventional full color photographic image to be formed.
Such a high-quality image, however, cannot be formed on a transfer material undyable with a dye, such as plain paper, in order to solve this problem, a thermal transfer image-receiving sheet comprising a substrate sheet and a dye-receptive layer previously formed on the substrate sheet has been used in the art.
Conventional thermal transfer image-receiving sheets are generally thick and have a dye-receptive layer of which the surface has a texture close to the so-called “photographic paper” rich in gloss, so that in some sense they can be said to give an impression of high grade.
However, in the so-called “applications in office,” the gloss of the surface of the dye-receptive layer and the bard texture of the sheet per so give-a poor image to users. In order to overcome this problem, a thermal transfer image-receiving sheet, particularly one which has a surface having a texture close to plain paper and can be handled like copying paper, has been desired in the art.
DISCLOSURE OF THE INVENTION
The present invention has been made under these circumstances, and an object of the present invention is to provide a thermal transfer image-receiving sheet, particularly one which particularly has a surface having a texture close to plain paper and can be handled like copying paper.
In order to attain the above object, the first invention provides a the thermal transfer image-receiving sheet comprising a substrate sheet and a dye-receptive layer provided directly or through an intermediate layer on one surface of said substrate sheet, said dye-receptive layer having a surface roughness of center line average height Ra=1.0-4.0 &mgr;m, maximum height R
max
=15.0-37.0 &mgr;m and 10-point average height Rz=10.0-30.0 &mgr;m.
Since the dye-receptive layer constituting the thermal transfer image-receiving sheet has a surface roughness falling within a particular range, the sheet has a surface having a texture close to plain paper and can be handled like copying paper and fits the needs of use in offices.
An image-receiving sheet using a conventional paper substrate sheet with an image being formed thereon is comparable to a print obtained by the conventional printing in texture, such as surface gloss and thickness, and, unlike an image-receiving sheet using the conventional synthetic paper as the substrate sheet, can be bent, and a plurality of sheets thereof may be put on top of one another for bookbinding or filing, which renders the thermal transfer image-receiving sheet using paper as the substrate sheet suitable for various applications. Further, since plain paper is more inexpensive than synthetic paper, the image-receiving sheet can be produced at a lower cost. In such an image-receiving sheet, in order to compensate for the cushioning property of the substrate sheet, it is generally preferred to provide as an interposing layer a layer having a high cushioning property, for example, an expanded layer (foamed layer) comprising a resin and an expanding agent (foaming agent).
However, when an expandable layer to be converted to an expanded layer is formed directly on plain paper by coating, the coating solution is unfavorably penetrated into the plain paper as the substrate sheet. This renders the resultant expandable layer so thin that the expansion of an expanding agent contained in the expandable layer provides only a low expansion ratio, which makes it difficult to impart a desired cushioning property.
Further, when an expandable layer is formed on plain paper by coating an aqueous coating solution, the paper absorbs water, resulting in the occurrence of wrinkle and waviness on the paper.
Accordingly, an object of the present invention is to provide such a thermal-transfer image-receiving sheet that neither wrinkle nor waviness occurs at the time of forming an expandable layer, the expandable layer is highly expandable and the resultant expanded layer has a high cushion property.
Another object of the present invention is to provide a thermal transfer image-receiving sheet having excellent print quality, printing sensitivity and other properties and texture such as gloss and surface geometry comparable to paper.
In order to solve the above problems, the second invention provides a thermal transfer image-receiving sheet comprising paper as a substrate sheet and, provided on said substrate sheet in the following order, an expanded layer and a receptive layer, an undercoat layer being provided between said substrate sheet and said expanded layer.
In the thermal transfer image-receiving sheet of the present invention an undercoat layer is first formed on a substrate sheet, and an expandable layer to be converted to an expanded layer is formed thereon by coating. By virtue of this constitution, the coating solution for an expanded layer does not penetrate into the substrate sheet and can be easily expanded, so that an expanded layer having a high cushioning property can be formed. Further, since the penetration of the coating solution for an expanded layer into paper can be prevented, it is possible to prevent the occurrence of wrinkle and waviness on the substrate sheet.
Further, the provision of an intermediate layer between the expanded layer and the receptive layer is preferred for preventing the expanded layer from being collapsed by beating at the time of printing.
According to the finding of the present inventors however, when the intermediate layer is formed by coating a resin coating solution using an organic solvent, the coating solution for an intermediate layer collapses cells and voids of the expanded layer, so that a desired cushioning property cannot be attained. If an image is formed on such an image-receiving sheet, dropout or lack of uniformity in density occurs, so that no sharp image can be provided.
An image is formed by the migration of a dye held in the dye layer of the thermal transfer sheet to the image-receiving sheet by heating. In this case, the collapse of the expanded layer lowers the heat insulating properties of the expanded layer, which causes the heat necessary for the transfer of the dye to be diffused towards the back surface of the image-receiving sheet. This results in a lowering in printing sensitivity.
Particularly when the expandable layer is expanded with an expanding agent, such as a microsphere, the organic solvent In the intermediate layer dissolves a thermoplastic resin serving as the wall of the microsphere and consequently breaks the hollow of the microsphere, thus rendering the above phenomenon significant.
Accordingly, an object of the third invention is to provide a thermal transfer image-receiving sheet which has texture such as gloss and surface geometry comparable to paper, high printing sensitivity and causes neither dropout nor uneven density.
In order to solve the above problems, the third invention provid
Imoto Kazunobu
Kamikubo Yoshinori
Narita Satoshi
Ueno Takeshi
Dai Nippon Printing Co. Ltd.
Hess Bruce H.
Parkhurst & Wendel LLP
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