Ribbon for smoothing print image and method for smoothing...

Coating processes – With post-treatment of coating or coating material – Solid treating member or material contacts coating

Reexamination Certificate

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Details

C427S375000, C428S195100, C428S212000, C428S409000, C428S447000, C428S913000, C428S914000

Reexamination Certificate

active

06180173

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a ribbon for smoothing a print image useful for smoothing a print image formed on a receptor by thermal transfer and a method for smoothing a print image using the ribbon.
Print images formed on a receptor such as a paper sheet by thermal transfer using a thermal transfer recording medium frequently have an uneven surface and are poor in gloss, resulting in poor quality. This tendency is outstanding in color images which are obtained by superimposing yellow, magenta and cyan inks and develop a color by virtue of subtractive color mixture.
In order to improve the gloss of print images obtained by thermal transfer, a method is used wherein heat and pressure are applied to the print images through a film ribbon subjected to a release treatment.
However, when a serial type thermal transfer printer which is a small-sized thermal transfer printer adopted in a word processor, a personal computer, and the like is used and the smoothing treatment is conducted by heating the print image under pressure by means of a thermal head while feeding such a release-treated film ribbon, the ribbon slips causing traveling failure and, hence, the smoothing treatment of the print image is not favorably performed.
In view of the forgoing, an object of the present invention is to provide a ribbon for smoothing a print image which does not slip causing no traveling failure, thereby enabling favorable smoothing treatment of the print image.
Another object of the present invention is to provide a method for smoothing a print image using the ribbon.
These and other objects of the present invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
In accordance with a first feature of the present invention, there is provided a ribbon for smoothing a print image for use in a method which comprises bringing the ribbon into contact with a print image formed on a receptor by thermal transfer and heating the print image from the opposite side of the ribbon with respect to the side contacting the print image under pressure by means of a thermal head, thereby smoothing the print image,
the ribbon having a kinetic friction coefficient, &mgr;
A
, on the side A thereof contacting the thermal head and a kinetic friction coefficient, &mgr;
B
, on the side B thereof contacting the print image, the values &mgr;
A
and &mgr;
B
satisfying the following equations:
&mgr;
B
>1.67 &mgr;
A
0.10<&mgr;
B
<0.25.
In accordance with a first embodiment of the first feature, the ribbon has on both sides A and B respective lubricating layers comprising the same resin as a main component, only the lubricating layer on the side B further containing particles.
In accordance with a second embodiment of the first feature, the ribbon has on the both sides A and B respective lubricating layers each comprising a silicone resin, the silicone resin of the lubricating layer on the side A containing a larger amount of a silicone chain than that of the silicone resin of the lubricating layer on the side B.
In the first embodiment of the first feature, preferably the resin of the lubricating layer on the side A and the resin of the lubricating layer on the side B each comprise a graft copolymer containing a silicone chain as a branch polymer.
In the second embodiment of the first feature, preferably the silicone resin of the lubricating layer on the side A and the silicone resin of the lubricating layer on the side B each comprise a graft copolymer containing a silicone chain as a branch polymer.
In the first embodiment of the first feature, preferably the particles have an average particle size of 0.05 to 0.5 &mgr;m.
In accordance with a second feature of the present invention, there is provided a method for smoothing a print image comprising:
bringing a ribbon for smoothing a print image into contact with a print image formed on a receptor by thermal transfer using a thermal transfer recording medium, and heating the print image from the opposite side of the ribbon with respect to the side contacting the print image under pressure by means of a thermal head, thereby smoothing the print image,
wherein the ribbon has a kinetic friction coefficient, &mgr;
A
, on the side A thereof contacting the thermal head and a kinetic friction coefficient, &mgr;
B
, on the side B thereof contacting the print image, the values &mgr;
A
and &mgr;
B
satisfying the following equations:
&mgr;
B
1.67 &mgr;
A
0.10<&mgr;
B
<0.25.
In accordance with an embodiment of the second feature, the ribbon has on both sides A and B respective lubricating layers each comprising the same resin as a main component as the main binder resin of the back layer of the thermal transfer recording medium.
DETAILED DESCRIPTION
The present inventors have intensively investigated the reason for the traveling failure of the conventional print-image-smoothing ribbon. The present inventors found that the conventional ribbon has the same degree of slipping property on both sides thereof and fails to provide a sufficient difference between the friction force between the ribbon and the thermal head and the friction force between the ribbon and the receptor, causing the traveling failure of the ribbon. The present inventors have further conducted investigations on the basis of this finding, leading to the completion of the present invention.
That is, it has been found that when the kinetic friction coefficient, &mgr;
A
, of the print-image-smoothing ribbon on the side A thereof contacting the thermal head and the kinetic friction coefficient, &mgr;
B
, of the ribbon on the side B thereof contacting the print image, the values &mgr;
A
and &mgr;
B
satisfy the following equations (I) and (II):
&mgr;
B
>1.67 &mgr;
A
  (I)
0.10<
B
<0.25  (II)
traveling failure of the ribbon can be prevented.
When the values &mgr;
A
and &mgr;
B
satisfy the relation expressed by equation (I), the friction force of the print-image-smoothing ribbon on the side B is greater than the friction force of the ribbon on the side A, whereby preventing the ribbon from traveling failure, provided that the value &mgr;
B
satisfies equation (II). When the value &mgr;
B
is not less than 0.25, the ribbon sticks to the print image. When the value &mgr;
B
is not more than 0.10, the traveling of the ribbon is not stable.
The print-image-smoothing ribbon of the present invention has a structure wherein a lubricating layer composed of a resin as a main component is provided on one or both sides thereof of the foundation and the values &mgr;
A
and &mgr;
B
of the ribbon on both sides satisfy the relations expressed equations (I) and (II). Preferably the lubricating layer is provided on both sides of the foundation because the respective values &mgr;
A
and &mgr;
B
of both sides can be readily adjusted.
In the case of the ribbon having a structure wherein the foundation has respective lubricating layers on both sides thereof, examples of means for allowing the values &mgr;
A
and &mgr;
B
of the ribbon to satisfy equations (I) and (II) include, for instance, a means wherein different resins are used for the lubricating layer on the side A contacting the thermal head (hereinafter referred to as “lubricating layer A”) and for the lubricating layer on the side B contacting the print image (hereinafter referred to as “lubricating layer B”), and a means wherein the same resin is used for both the lubricating layer A and the lubricating layer B, and a particulate substance is added to only one of the lubricating layers A and B or a particulate substance is added to both the lubricating layers A and B and the contents of the particulate substance in both layers are made different from each other.
In accordance with the first preferred embodiment of the first feature, the lubricating layers A and B are composed of the same resin as a main component and only the lubricating layer B further contains a particulate substance.
In accordance with the second preferred embodiment of the first feature, the lubricating la

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