Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-11-24
2002-10-22
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
Reexamination Certificate
active
06468634
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat transfer sheet used in an image forming process in which an image with a high resolution is formed by using a thermal head or a laser light.
2. Description of the Related Art
As an image recording process by heat-transfer, conventionally, a process in which a heat transfer sheet is directly pressed and heated by a thermal head is in widespread use. This process has some superior characteristics in that it is able to be performed at a low noise level using a simple device structure, maintenance is not necessary, and the process is a dry processing. Recently, the densification of the thermal head itself has been improved. In the above process, it is possible to obtain images whose resolution has been increased to a high level.
As an image recording process by heat-transfer which is able to record images with higher resolutions, a laser heat transfer recording process has been known in which a laser light is irradiated onto the heat transfer sheet, the laser light is converted into heat in the heat transfer sheet and thus recording is carried out by the heat. In the above described process, because laser light serving as an energy supply source can be condensed to a few microns, it is possible to improve resolutions significantly compared with the process using the thermal head.
As the heat transfer sheet used in a laser heat transfer recording process, a heat-fusing transfer sheet (described in Japanese Patent Application Laid-Open (JP-A) No. 5-58,045 and the like) is known, which comprises, on a substrate, a light-to-heat conversion layer which absorbs the laser light and generates heat, and an image forming layer in which pigment is dispersed in a component such as a heat-fusing wax, a binder or the like in that order. When the above-described heat-fusing transfer sheet is used, the image forming layer corresponding to a laser light illuminating region of the light-to-heat conversion layer is fused by heat generated in the laser light illuminating region, and is transferred to an image receiving sheet superimposed on the heat-fusing transfer sheet. As a result, a transferred images formed on the image receiving sheet.
JP-A No. 6-219,052 disclosed an image forming process in which a heat transfer sheet is used for forming highly detailed image on the image receiving sheet which is superimposed upon the heat transfer sheet In the heat transfer sheet, a light-to-heat conversion layer containing a heat-to-light conversion material, a very thin (0.03-0.31 &mgr;m) heat peeling layer and an image forming layer containing a color material are disposed in that order on a substrate, and the bonding strength between the image forming layer and the light-to-heat conversion layer bound together due to the heat peeling layer therebetween is weakened by the irradiation of laser light. In this image forming process, so called “abrasion” is utilized. Specifically, in a region illuminated with the laser light, the heat peeling layer is partially decomposed and vaporized. As a result, the adhesion between the image forming layer and the light-to-heat conversion layer is weakened so that the image forming layer in the illuminated region is transferred to the image receiving sheet superposed on the heat transfer sheet and the transferred image is formed on the image receiving sheet.
The image forming process utilizing laser light has advantages in that it is able to use printing paper provided with an image receiving layer (an adhesive layer) serving as the image receiving sheet, a multi-color image can be easily formed by transferring sequentially different color images onto the image receiving sheet and the like. In particular, the image forming process utilizing abrasion has an advantage in that highly detailed images can be easily formed.
In these image forming methods using heat transfer, because the adhesion between the heat transfer sheet and the image receiving sheet when the image is transferred affects considerably the resolution of the image, the key to obtaining an image with high resolution is enhancing the adhesion between the heat transfer sheet and the image receiving sheet
As a method for enhancing the adhesion between the heat transfer sheet and the image receiving sheet, there may be proposed a method in which the heat transfer sheet and the image receiving sheet are superimposed with each other, and are wound onto a cylindrical drum having a plurality of through holes. The pressure inside the cylindrical drum is then reduced such that the adhesion between the heat transfer sheet and the image receiving sheet is enhanced. However, in this process, air is accumulated between the heat transfer sheet and the image receiving sheet and the sheets becomes wavy. As a result, complete adhesion of the sheets may be rather inhibited. Therefore, in order to solve the problems such as air accumulation and the like, particulate material, having a particle size of several &mgr;m to several tens of &mgr;m, which is referred to as a matte agent, is added to surface layers of the heat transfer sheet and/or the image receiving sheet which face each other so that the surface of the heat transfer sheet and/or the image receiving sheet is made uneven. By this method, problems such as air accumulation are solved and vacuum adhesion uniformity between the sheets can be ensured.
However, when the matte agent is added to the surface layer of the heat transfer sheet, problems such as image voids may be generated and at the same time the hue of formed images may be affected so that images having good hues cannot be formed. On the other hand, when the matte agent is added to the surface layer of the image receiving sheet, there may be cases in which image voids are generated.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a heat transfer sheet which can ensure vacuum adhesion uniformity between the heat transfer sheet and an image receiving sheet at the time of heat-transfer and form images with high quality without using a matte agent which may affect the image quality in an ink layer.
In order to accomplish the above-described object, the present invention has the characteristics given below.
In accordance with a first aspect of the present invention, there is provided a heat transfer sheet which comprises a substrate, and an ink layer which is provided on the substrate and contains a pigment and an amorphous organic polymer, wherein the ink layer is structured such that, no particulate material having the function of forming unevenness of the surface of the ink layer is used in the ink layer, and the 10-point mean surface roughness (Rz) of the surface of the ink layer is 0.5~5.0 &mgr;m.
In accordance with a second aspect of the present invention, an intermediate layer, containing a particulate material having the function of forming unevenness on the surface of the ink layer, is provided between the substrate and the ink layer.
In accordance with a third aspect of the present invention, the thickness of the intermediate layer portions, where no particulate material which has the function of forming unevenness on the surface of the ink layer is present, is smaller than the number average particle diameter of the particulate material.
In accordance with a fourth aspect of the present invention, the number average particle diameter of the particulate material is 0.5 &mgr;m or more, and the ink layer contains a wax.
In accordance with a fifth aspect of the present invention, the weight ratio (W:P) of the content of the wax (W) to the content of the amorphous organic polymer (P) in the ink layer is 5:100~100:100.
In accordance with a sixth aspect of the present invention, the number average particle diameter of the particulate material is 0.6~4.0 &mgr;m.
In accordance with a seventh aspect of the present invention, the content of the particulate material in the intermediate layer is 5~100 mg/m
2
.
In accordance with an eighth aspect of the present invention, the particulate mat
Hatakeyama Akira
Miyake Kazuhito
Shimomura Akihiro
Fuji Photo Film Co. , Ltd.
Schwartz Pamela R.
Sughrue & Mion, PLLC
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