Method for transferring hot-melt ink to a recording medium

The present invention discloses a method for thermally transferring an ink pattern to a recording medium, comprising the steps of preparing an ink sheet provided with a hot-melt and/or hot-sublimable ink layer and a transparent material sheet provided with a transparent hot-melt material layer, thermally producing an ink pattern on the transparent material layer of the transparent material sheet by heating the ink sheet with thermal head, and thermally transferring the ink pattern to the recording medium together with the transparent hot-melt material layer. And an another method comprising the steps of preparing an ink sheet having a transparent hot-melt material frame layer and a hot-melt and/or hot-sublimable ink frame layer, thermally transferring the transparent hot-melt material frame layer onto a surface of a platen roller, thermally producing an ink pattern on the transparent hot-melt material frame layer on the platen roller by heating the hot-melt and/or hot-sublimable ink frame layer with a thermal head, and thermally transferring the ink pattern together with the transparent hot-melt material frame layer onto a recording medium.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to improvements of a thermal transferring 
printing method, and it particularly relates to a thermal transferring 
printing method suitable to a recording medium of which a surface has 
unevenness to print thereon. 
2. Description of the Related Art 
As is well known, a thermal transferring printing apparatus is used to 
print an ink pattern such as a picture or letters on a recording medium by 
thermally transferring hot-melt or hot-sublimable ink coated on an ink 
sheet to the recording medium by heating the ink sheet with a thermal 
head. However, it poses a problem that a recording medium having surface 
unevenness (rough surface) can not be employed in the apparatus because of 
degradation of printing quality due to an insufficient contact of the ink 
with the recessed portions of the unevenness of the recording medium. 
As countermeasure of the insufficient contact, a hot-melt ink having high 
fluidity or a dot plate formed in accordance with the printing contents is 
employed as well as applying a large contact force with the thermal head. 
However, an acceptable result is not obtained yet. 
In order to eliminate the above problem, there is proposed a thermal 
transferring printing method in "Japan Hardcopy '92", as shown in FIG. 1. 
FIG. 1 is a side view showing a general construction and an operation of a 
thermal transfer printer in a prior art. 
Referring to FIG. 1, after thermally transferring an ink pattern 101 onto a 
surface of a soft platen roller 103 from an ink sheet 100 with a thermal 
head 102, the ink pattern 101 on the platen roller 103 is printed by 
pressing the platen roller 103 onto a surface of a recording medium 104 
having an uneven surface to be printed. 
In the above method, however, when using high fluidity ink, there are 
problems that the ink is liable to flow out from the printed ink pattern 
on the recording medium when the recording medium has a smooth surface in 
particular, and it is difficult to superpose many colors of ink on the 
recording medium at the same time. In addition, a printing of a picture 
having gradation is also difficult. 
SUMMARY OF THE INVENTION 
Accordingly, a general object of the present invention is to provide 
methods for transferring hot-melt ink to a recording medium in which the 
above disadvantages have been eliminated. 
A specific object of the present invention is to provide a method for 
thermally transferring an ink pattern to a recording medium, comprising 
the steps of, preparing an ink sheet provided with a hot-melt and/or 
hot-sublimable ink layer thereon and a transparent material sheet provided 
with transparent hot-melt material layer thereon, thermally producing an 
ink pattern on the transparent hot-melt material layer of the transparent 
material sheet by heating the hot-melt and/or hot-sublimate ink layer with 
a thermal head, and thermally transferring the ink pattern produced on the 
transparent hot-melt material layer to the recording medium together with 
the transparent hot-melt material layer. 
An another specific object of the present invention is to provide a method 
for thermally transferring hot-melt and/or hot-sublimable ink to a 
recording medium, comprising the steps of, preparing an ink sheet having 
at least a transparent hot-melt material frame layer and a hot-melt and/or 
hot-sublimable ink frame layer thereon, thermally transferring the 
transparent hot-melt material frame layer onto a surface of a platen 
roller, thermally producing an ink pattern ont he transferred transparent 
hot-melt frame layer on the platen roller by heating the transparent 
hot-melt and/or hot-sublimable ink frame layer with a thermal head, and 
thermally transferring the ink pattern produced on the transparent 
hot-melt material layer to the recording medium together with the 
transparent hot-melt frame layer. 
Other objects and further features of the present invention will be 
apparent from the following detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Description will be given to an embodiment according to the present 
invention accompanying drawings. 
FIG. 2 is a side view showing a general construction and an operation of a 
thermal transfer printer of an embodiment according to the present 
invention. 
Referring to FIG. 2, a thermal transfer printer of the present invention 
generally comprises a thermal head 1, a first supply reel 2, a first 
take-up reel 3, an ink sheet 4 extendedly provided between the first 
supply and take-up reels 2, 3 through a guide roller (not shown), a second 
supply reel 5, a second take-up reel 6, a transparent material sheet 8 
extendedly provided between the second supply and take-up reels 5, 6 
through a guide roller 7, a supporting stage 9 for supporting the 
transparent material sheet 8, a third supply reel 12 for supplying a 
recording medium 10 through a guide roller 11, a heating roller 13 
provided in an opposite relation with the guide roller 11. 
FIG. 3 is a plan view showing an ink sheet used in the present invention. 
As shown in FIG. 3, the ink sheet 4 is provided with ink frame layers made 
of hot-melt and/or sublimable ink of at least one or more colors, for 
instance, yellow (Y), magenta (M) and cyan (C) at a predetermined pitch on 
a base sheet. 
FIG. 4 and FIG. 5 are sectional views showing the printing processes of the 
printer shown in FIG. 2. 
The transparent material sheet 8 is made by coating a hot-melt transparent 
material 8b on a base film 8a, for instance, made of polyester resin, as 
shown in FIG. 4. 
For the material of the hot-melt transparent material 8b, such material as 
wax, for instance, paraffin wax, microcrystalline wax or carnauba wax is 
used as a major component and a small amount of oil, for instance, linseed 
oil or mineral oil is used as an additive. In order to have hot-sublimable 
material, cellulose-acetate-propionate resin and polyester resin may 
further be added to the above listed wax based material and used as the 
hot-melt transparent material 8b as well. 
Next, the description is given to the method for transferring the hot-melt 
ink to the recording medium 10 in above thermal transferring printing 
apparatus referring to FIG. 4 and FIG. 5. 
At first, the transparent material sheet 8 is placed stationary on the 
supporting stage 9 in such a manner that the layer of the transparent 
material 8b thereof faces upward, and the ink sheet 4 is superposed on the 
transparent material sheet 8 in such a manner that an ink frame 4a closely 
touches the transparent material 8b. Then, both of them are pressed by the 
thermal head 1 being heated as they are transported from an end of the 
supporting stage 9 to another end thereof, so that an ink pattern 4a is 
transferred to the transparent material 8a as shown in FIG. 4. 
In order to obtain a color printing, the same operation is repeatedly 
performed with other color ink frames of the ink sheet 4 after taking-up 
the used one color ink frame of the ink sheet 4 by the first take-up reel 
3 and returning the thermal head 1 to the initial position. 
After a full color image is printed on the transparent material sheet 8, 
the transparent material sheet 8 carrying the full color image 4a is 
forwarded in the direction of arrow to the heating roller 13 by the second 
taking-up roller 6, during this movement, the transparent material sheet 8 
and the recording medium 10 fed out of the third supply reel 12, are 
interposed together between the guide roller 11 and the heating roller 13 
is heated. This causes the ink pattern 4a (full color) together with the 
layer of the transparent material 8b to contact closely with the recording 
medium 10 and to be heated together by the heating roller 13 so that the 
ink pattern 4a together with the layer of the transparent material 8b is 
thermally transferred to the recording medium 10 as shown in FIG. 5. 
As mentioned in the foregoing, after the ink pattern is transferred to the 
surface of the transparent material sheet 8 with the thermal head 1, then 
the ink pattern is further transferred together with the layer of the 
transparent material 8b to the recording medium 10 by causing the layer of 
the transparent material 8b to be separated from the base film 8a and 
transferred on to the recording medium 10. 
Thus, it will be understood that the printing quality according to the 
present invention is not affected by the unevenness of the surface of the 
recording medium 10. 
Further, transparent material sheet which carries the ink pattern on the 
layer of the transparent material 8b, may be cut to a section of printed 
sheet so that such section may be used to print the carried pattern on a 
desired recording medium, for example, a recording medium having a 
predetermined configuration or a three dimensional configuration can be 
thermally printed by using such a cut section of printed sheet. 
Next, the description is given to a further embodiment of the present 
invention accompanying FIGS. 6 through 11. 
FIG. 6 and FIG. 7 are side elevations respectively showing a general 
construction and the operation of a thermal transfer printer according to 
the further embodiment of the present invention. 
Referring to FIG. 6 and FIG. 7, this thermal transfer printer generally 
comprises a thermal head 21, a supply reel 22, a take-up reel 23, an ink 
sheet 24 extendedly provided between the supply and take-up reels 22, 23, 
a platen roller 25 having a soft and smooth surface and equipped with a 
heater (not shown) therein and a press roller 27 for pressing a recording 
medium 26 to the platen roller 25. 
FIG. 8 is a plan view showing an ink sheet used for the further embodiment 
of the present invention. 
As shown in FIG. 8, the ink sheet 24 is provided with ink frame layers made 
of hot-melt and/or sublimable ink 24a of at least one or more colors, for 
instance, yellow (Y), magenta (M) and cyan (C), and a transparent hot-melt 
material frame layer U at a predetermined pitch on a base sheet, where a 
material of the transparent hot-melt material frame layer U is printable 
with the sublimable ink. 
The following is the description of the method for transferring the ink to 
the recording medium 26 in the above thermal transferring printing 
apparatus. 
At first, the transparent material frame layer U on the ink sheet 24 is 
thermally transferred onto the platen roller 25 as shown in FIG. 9 by 
pressing the ink sheet 24 onto the platen roller 25 with the thermal head 
21 as shown in FIG. 6. Then, the ink sheet 24 is fed in an arrow 
direction, and an ink pattern made of hot-melt and/or sublimable ink 24a 
is thermally transferred onto the transparent material frame layer U 
previously transferred on the platen roller 25 as shown in FIG. 10. After 
that, as shown in FIG. 7, the ink pattern together with the transparent 
frame U is thermally transferred onto a recording medium 26 by being 
closely contacted, heated and depressed to the recording medium 26 by the 
heater in the platen roller 25 and the press roller 27 respectively. 
Thus, the ink pattern 24a is printed on the recording medium 26 as shown in 
FIG. 11. 
It should be noted that the recording medium 26 comprises a base 26b and a 
printing ink acceptable layer 26a on the base 26b for being easily 
printed. 
Accordingly, it is possible to obtain a high printing quality for the 
recording medium 26 having an uneven surface without being affected by the 
unevenness, since the ink pattern is thermally transferred onto the 
transparent material frame layer U transferred preliminary on the platen 
roller 25, then to the recording medium 26, together with the transparent 
material frame U, i.e. not directly on the uneven surface. 
As shown in FIG. 12, since it is possible to make the printing area P of 
the platen roller 25 equal to the area of the recording medium 26 or more 
than that, it is easy to print the ink pattern on a full area of the 
recording medium. 
Further, in the prior art, an ink pattern printed on the recording medium 
with the sublimable ink in the thermal printing has to be overcoated 
subsequently with a protective transparent layer to prevent the sublimable 
ink pattern from sublimating. However, it should be noted that the method 
of the present invention requires no additional protective transparent 
layer because the layer of the transparent material 8b has a such function 
effect as a protection film.