Intermediate transfer type thermal transfer recording method

An intermediate transfer type thermal transfer recording method comprising the steps of: forming first an image on an intermediate transfer medium by heating a melt-type thermal transfer recording medium with a heating head, and transferring the image formed on the intermediate transfer medium onto an image receptor pressed against the intermediate transfer medium, wherein an image of a heat-meltable colored ink is formed on an image receptor by said intermediate transfer type thermal transfer recording method and a transparent heat-meltable ink is then transferred on the image receptor to cover a region thereof including the image of the colored ink by said intermediate transfer type thermal transfer recording method. The method provides a lustrous image on a paper sheet and an image with high light transmittance on an OHP sheet.

BACKGROUND OF THE INVENTION 
The present invention relates to an intermediate transfer type thermal 
transfer recording method. 
The intermediate transfer type thermal transfer recording method is a 
method wherein a melt-type thermal transfer recording medium is used to 
form first an image on an intermediate transfer medium according to image 
signals, and the image obtained on the intermediate transfer medium is 
then transferred onto an image receptor. 
The intermediate transfer type thermal transfer recording method is an 
image formation method wherein an intermediate transfer printer such as 
shown in FIG. 1 or FIG. 2 is used. In FIGS. 1 and 2, numeral 10 denotes a 
rotatable intermediate transfer drum and numeral 20 denotes a rotatable 
intermediate transfer belt. Numeral 11 denotes a recording part which is 
arranged so. that a thermal transfer recording medium 12 can be pressed 
against the intermediate transfer drum 10 or intermediate transfer belt 20 
with a heating head 13. In recording, the recording medium 12 is moved in 
the direction indicated by an arrow as the intermediate transfer drum 10 
or intermediate transfer belt 20 rotates. Numeral 14 denotes a transfer 
part which is arranged so that an image receptor 15 can be pressed against 
the intermediate transfer drum 10 or intermediate transfer belt 20 with a 
pressing roller 16. In transferring, the image receptor 15 is moved in the 
direction indicated by an arrow. 
The thermal transfer recording medium 12 is heated with the heating head 13 
so as to selectively soften or melt portions of the colored ink thereof, 
which are transferred onto the surface of the intermediate transfer drum 
10 or intermediate transfer belt 20 as an intermediate transfer medium. 
While the intermediate transfer drum 10 or intermediate transfer belt 20 
and the recording medium 12 are thus moved in the directions indicated by 
the arrows, respectively, the colored ink is transferred onto the 
intermediate transfer drum 10 or intermediate transfer belt 20, thereby 
forming an ink image 17 thereon. As the intermediate transfer drum 10 or 
intermediate transfer belt 20 rotates, the ink image 17 is moved to the 
transfer part 14, pressed against the image receptor 15 there, and 
transferred onto the image receptor 15 to form a final ink image 18 
thereon. 
According to such an intermediate transfer type thermal transfer recording 
method, the ink of the recording medium which is heated with the heating 
head 13 is transferred onto a smooth surface of the intermediate transfer 
drum 10 or intermediate transfer belt 20. Hence, the problem involved in a 
common thermal transfer method of the type that unclear transferred images 
are likely to be formed on an image receptor paper of which the surface is 
poor in smoothness-is overcome. Further, according to the intermediate 
transfer type thermal transfer recording method, ink images 17 on the 
intermediate transfer drum 10 or intermediate transfer belt 20 are 
transferred onto the image receptor 15 by pressing thereagainst under a 
large pressure with the pressing roller 16. Hence, the quality of the thus 
obtained images is not subject so much to the superficial conditions of 
the image receptor. 
In the aforesaid intermediate transfer type thermal transfer recording 
medium, the surface of the intermediate transfer drum 10 or intermediate 
transfer belt 20 is formed of a material of releasing properties such as 
silicone resin or rubber, fluorine-containing resin or rubber, or the like 
to facilitate release of the ink image 17 therefrom. Further, when the ink 
image 17 formed on the intermediate transfer drum 10 or intermediate 
transfer belt 20 is transferred onto the image receptor 15, it is 
necessary that the ink is in a softened or molten state. Therefore, a 
means is usually adopted wherein a heater is contained in the intermediate 
transfer drum 10 intermediate transfer belt 20, or the pressing roller 16 
to heat the ink into a softened or molten state. 
However, the aforesaid intermediate transfer type thermal transfer 
recording method involves two problems: (1) when the image receptor is a 
paper sheet, a lusterless image is obtained on the paper sheet and (2) 
when the image receptor is an OHP sheet (transparent sheet for an overhead 
projector), the image obtained on the OHP sheet is low in light 
transmittance and therefore the projection of the imprinted OHP sheet by 
means of an OHP provides a dull projected image. 
In view of the problems of the foregoing prior art, it is an object of the 
present invention to provide an intermediate transfer type thermal 
transfer recording method which is capable of providing a lustrous image 
on a paper sheet as an image receptor and providing an image with high 
light transmittance on an OHP sheet as an image receptor, resulting in a 
clear or vivid projected image. 
This and other objects of the present invention will become apparent from 
the description hereinafter. 
SUMMARY OF THE INVENTION 
The present invention provides (1) an intermediate transfer type thermal 
transfer recording method comprising the steps of: forming first an image 
on an intermediate transfer medium by heating a melt-type thermal transfer 
recording medium with a heating head, and transferring the image formed on 
the intermediate transfer medium onto an image receptor pressed against 
the intermediate transfer medium, 
wherein an image of a heat-meltable colored ink is formed on an image 
receptor by said intermediate transfer type thermal transfer recording 
method and a transparent heat-meltable ink is then transferred on the 
image receptor to cover a region thereof including the image of the 
colored ink by said intermediate transfer type thermal transfer recording 
method. 
The present invention further provides (2) the intermediate transfer type 
thermal transfer recording method of the above (1), wherein the 
intermediate transfer medium is heated to a temperature of 40.degree. to 
80.degree. C. at the surface thereof, and the intermediate transfer medium 
and the pressing roller are in contact with each other under a pressure of 
50 to 200 kg/30 cm, and the transparent heat-meltable ink has a softening 
point of 45.degree. to 90.degree. C. and a melt viscosity of 50 to 
5.times.10.sup.5 cp/100.degree. C. 
The present invention furthermore provides (3) the intermediate transfer 
type thermal transfer recording method of the above (1) or (2), wherein 
the transparent heat-meltable ink is transferred in substantially the same 
region as the region of the image of the colored ink transferred 
previously on the image receptor. 
Moreover, the present invention provides (4) the intermediate transfer 
thermal transfer recording method of any of the above (1) to (3), wherein 
if the image receptor is an OHP sheet, and the image of the colored ink is 
formed on the OHP sheet by using one or more of yellow, magenta and cyan 
inks as the heat-meltable colored ink, then the yellow, magenta and cyan 
inks are inks each capable of forming a region of single color image 
having a maximum transmittance of not less than 50% in the visible region, 
provided that the region of the single color image is formed by 
transferring each ink onto the OHP sheet to form an ink image of single 
color thereon and transferring the transparent heat-meltable ink onto the 
ink image of single color. 
In the present invention, the terms "melt-type" in the melt-type thermal 
transfer recording medium or "heat-meltable" in the heat-meltable vehicle 
is a concept including not only wherein the vehicle is changed from a 
solid state to a molten state but also wherein the vehicle is changed from 
a solid state to a softened state without reaching a molten state.

DETAILED DESCRIPTION 
In the thermal transfer recording method of the present invention, an image 
of a heat-meltable colored ink is first formed on an image receptor by the 
intermediate transfer method and an image of a transparent heat-meltable 
ink is then formed on the image of the colored ink by the intermediate 
transfer method. 
By virtue of such a constitution, an image formed on a paper sheet as an 
image receptor is reduced in diffused reflection of the surface thereof to 
improve the luster of the image. Further, an image formed on an OHP sheet 
as an image receptor is reduced in diffused reflection of the surface 
thereof to improve the light transmittance of the image and when the image 
is projected by means of an OHP, a projected image of vivid or clear color 
is obtained. Furthermore, smearing of the image does not occur in both 
cases. 
In the present invention, intermediate transfer printers, manners and 
conditions of operating the printers, thermal transfer recording media and 
the like which are used in the conventional intermediate transfer method 
can be adopted without any particular limitation except that an image of a 
heat-meltable colored ink is first formed on an image receptor by the 
intermediate transfer method and a transparent heat-meltable ink is 
transferred onto the image receptor to cover a region thereof including 
the image of the colored ink by the intermediate transfer method. 
In the intermediate transfer printer, usually, the releasing surface of the 
intermediate transfer medium is heated to a temperature of 40.degree. to 
80.degree. C. to enable the transfer of an image formed on the 
intermediate transfer medium to an image receptor. Further, the contact 
pressure between the intermediate transfer medium and the pressing roller 
is usually set to a value of 50 to 200 kg/30 cm (line pressure provided 
that the length of the intermediate transfer medium in the crosswise 
direction is 30 cm, hereinafter the same) to facilitate the transfer of an 
image formed on the intermediate transfer medium to an image receptor. 
The heat-meltable colored ink useful in the present invention is a colored 
ink comprising a coloring agent and a heat-meltable vehicle (comprising a 
wax and/or a thermoplastic resin). The heat-meltable colored ink may be 
further incorporated with an additive such as a dispersing agent, or the 
like. 
Examples of specific waxes include natural waxes such as lanolin, carnauba 
wax, candelilla wax, montan wax and ceresine wax; petroleum waxes such as 
paraffin wax and microcrystalline wax; synthetic waxes such as oxidized 
wax, ester wax, low molecular weight polyethylene wax, Fischer-Tropsch 
wax, .alpha.-olefin-maleic anhydride copolymer wax and synthetic petroleum 
wax. These waxes can be used either alone or in combination. 
Examples of specific thermoplastic resins (inclusive of elastomers) include 
ethylene copolymers such as ethylene-vinyl acetate copolymer, 
ethylene-vinyl butyrate copolymer, ethylene-(meth)acrylic acid copolymer, 
ethylene-alkyl (meth)acrylate copolymer wherein examples of the alkyl 
group are those having 1 to 16 carbon atoms, such as methyl, ethyl, 
propyl, butyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, dodecyl and 
hexadecyl, ethylene-acrylonitrile copolymer, ethylene-acrylamide 
copolymer, ethylene-N-methylolacrylamide copolymer and ethylene-styrene 
copolymer; poly(meth)acrylic acid esters such as polylauryl methacrylate 
and polyhexyl acrylate; vinyl chloride polymer and copolymers such as 
polyvinyl chloride, vinyl chloride-vinyl acetate copolymer and vinyl 
chloride-vinyl alcohol copolymer; polyesters, polyamides, epoxy resins, 
cellulose resins, natural rubber, styrene- butadine copolymer, isoprene 
polymer and chloroprene polymer; petroleum resins, rosin resins, terpene 
resins and cumarone-indene resins. These resins can be used either alone 
or in combination. 
Usable as the coloring agent in the colored ink layer are carbon black and 
other various organic and inorganic pigments. Examples of such organic and 
inorganic pigments include azo pigments (such as insoluble azo pigments, 
azo lake pigments and condensed azo pigments), phthalocyanine pigments, 
nitro pigments, nitroso pigments, anthraquinonoid pigments, nigrosine 
pigments, quinacridone pigments, perylene pigments, isoindolinone 
pigments, dioxazine pigments and titanium white. Such pigments may be used 
in combination with dyes. 
In the case of forming multi-color or full-color images by utilizing 
subtractive color mixture, there are used yellow pigments, magenta 
pigments and cyan pigments, and as required, black pigments. These 
pigments for yellow, magenta and cyan are preferably transparent ones. 
Pigments for balck are usually opaque ones. 
Examples of specific transparent pigments for yellow include organic 
pigments such as Naphthol Yellow S, Hansa Yellow 5G, Hansa Yellow 3G, 
Hansa Yellow G, Hansa Yellow GR, Hansa Yellow A, Hansa Yellow RN, Hansa 
Yellow R, Benzidine Yellow, Benzidine Yellow G, Benzidine Yellow GR, 
Permanent Yellow NCG, Quinoline Yellow Lake and Disazo Yellow. These 
pigments may be used either alone or in combination. 
Examples of specific transparent pigments for magenta include organic 
pigments such as Permanent Red 4R, Brilliant Fast Scarlet, Brilliant 
Carmine BS, Permanent Carmine FB, Lithol Red, Permanent Red F5R, Brilliant 
Carmine 6B, Pigment Scarlet 3B, Rhodamine Lake B, Rhodamine Lake Y, 
Arizalin Lake and Quinacridone Red. These pigments may be used either 
alone or in combination. 
Examples of specific transparent pigments for cyan include organic pigments 
such as Victoria Blue Lake, metal-free Phthalocyanine Blue, Phthalocyanine 
Blue and Fast Sky Blue. These pigments may be used either alone or in 
combination. 
The term "transparent pigment" herein refers to a pigment which gives a 
transparently colored ink when dispersed in a transparent vehicle. 
Examples of pigments for black include inorganic pigments such as carbon 
black, and organic pigments such as Aniline Black. These pigments may be 
used either alone or in combination. 
In the case that the surface temperature of the intermediate transfer 
medium is from 40.degree. to 80.degree. C. and the contact pressure 
between the intermediate transfer medium and the pressing roller is from 
50 to 200 kg/30 cm, as described above, a colored ink having a softening 
point of 55.degree. to 75.degree. C. and a melt viscosity of 50 to 400 
cp/100.degree. C. is preferably used to achieve favorable formation of an 
image of the colored ink on the intermediate transfer medium and favorable 
transfer of the image on the intermediate transfer medium to an image 
receptor. 
The coating amount (on a solid basis, hereinafter the same) of the colored 
layer is preferably from 0.5 to 3.0 g/m.sup.2. 
The transparent heat-meltable ink usable in the present invention is a 
substantially colorless transparent one which comprises a heat-meltable 
vehicle (comprising a wax and/or a thermoplastic resin) and contains 
substantially no coloring agent. 
Those exemplified for the colored ink can be used as the wax and 
thermoplastic resin which are the components of the heat-meltable vehicle 
for the transparent heat-meltable ink. 
In the case that the surface temperature of the intermediate transfer 
medium is from 40.degree. to 80.degree. C. and the contact pressure 
between the intermediate transfer medium and the pressing roller is from 
50 to 200 kg/30 cm, as described above, there is preferably used a 
transparent ink having a softening point of 45.degree. to 90.degree. C., 
especially 65.degree. to 80.degree. C. and a melt viscosity of 50 to 
5.times.10.sup.5 cp/100.degree. C., especially 100 to 10.times.10.sup.3 
cp/100.degree. C. When the softening point of the transparent 
heat-meltable ink is lower than the above range, the transparent ink is 
excessively softened on the intermediate transfer medium and hardly forms 
a uniform transparent ink layer when transferred onto the image of the 
colored ink on the image receptor. When the softening point of the 
transparent ink is higher than the above range, the transfer sensitivity 
at the time when the transparent ink is transferred onto the intermediate 
transfer medium is low. When the melt viscosity of the transparent 
heat-meltable ink is lower than the above range, the ink hardly forms a 
uniform transparent ink layer when transferred onto the image of the 
colored ink on the image receptor for the same reason as mentioned above. 
When the melt viscosity of the transparent ink is higher than the above 
range, the transfer sensitivity at the time when the transparent ink is 
transferred onto the intermediate transfer medium is low. 
The coating amount of the transparent heat-meltable ink is preferably from 
1.0 to 8.0 g/m.sup.2. When the coating amount is smaller than the above 
range, the desired effects are hardly achieved. When the coating amount is 
larger than the above range, it is difficult to form a transparent ink 
layer on the image of the colored ink due to its low transfer sensitivity. 
As the foundation for supporting the aforesaid colored ink or transparent 
ink, polyester films such as polyethylene terephthalate film, polybutylene 
terephthalate film, polyethylene naphthalate film and polyarylate film, 
polycarbonate film, polyamide film, aramid film, polyether sulfone film, 
polysulfone film, polyphenylene sulfide film, polyether ether ketone film, 
polyether imide film, modified polyphenylene ether film and polyacetal 
film, and other various plastic films commonly used for the foundation of 
ink ribbons of this type can be used. Thin paper sheets of high density 
such as condenser paper can also be used. The thickness of the foundation 
is usually from about 1 to about 10 .mu.m. From the viewpoint of reducing 
heat spreading to increase the resolution of images, the thickness of the 
foundation is preferably from 1 to 6 .mu.m . 
A conventionally known stick-preventive layer is preferably provided on the 
back side (the side adapted to come into slide contact with the heating 
head) of the foundation. Examples of the materials for the 
stick-preventive layer include various heat-resistant resins such as 
silicone resins, fluorine-containing resins and nitrocellulose resins, and 
other resins modified with these heat-resistant resins, such as 
silicone-modified urethane resins and silicone-modified acrylic resins, 
and mixtures of the foregoing heat-resistant resins and lubricating agent. 
The melt-type thermal transfer recording medium used for forming a colored 
ink image in the present invention includes a thermal transfer recording 
medium for forming an image of single color (monochromatic image) and a 
color thermal transfer recording medium for forming a multi-color or 
full-color image (polychromatic image) by utilizing subtractive color 
mixture. 
The thermal transfer recording medium for forming single color image is one 
wherein a heat-meltable colored ink layer of single color is disposed on a 
foundation (hereinafter referred to as "thermal transfer recording medium 
A"). The color of the heat-meltable colored ink is black, red, blue, 
green, yellow, magenta, cyan or the like. 
An embodiment of the color thermal transfer recording medium for forming a 
multi-color or full-color image is one wherein a yellow heat-meltable ink 
layer, a magenta heat-meltable ink layer and a cyan heat-meltable ink 
layer and optionally a black heat-meltable ink layer are disposed in a 
side-by-side relation on a single foundation. The manner of arrangement of 
such color ink layers includes various embodiments and is arbitrarily 
selected depending upon the type of printer used. 
For example, there is exemplified an example wherein a yellow heat-meltable 
ink layer, a magenta heat-meltable ink layer and a cyan heat-meltable ink 
layer and optionally a black heat-meltable ink layer, each of which 
preferably has a given constant size, are repeatedly arranged in a 
side-by-side relation on a foundation in a repeating unit wherein the 
yellow, magenta, cyan ink layers and optionally the black ink layer are 
arranged in a predetermined order (hereinafter referred to as "thermal 
transfer recording medium B"). The order of arrangement of the respective 
color ink layers in the repeating unit can be arbitrarily determined in 
consideration of the transfer order of the respective color ink layers. 
Another embodiment of the thermal transfer recording medium for forming a 
multi-color or full-color image is a set of thermal transfer recording 
media comprising a first thermal transfer recording medium having a yellow 
heat-meltable ink layer on a first foundation, a second thermal transfer 
recording medium having a magenta heat-meltable ink layer on a second 
foundation, and a third thermal transfer recording medium having a cyan 
heat-meltable ink layer on a third foundation, and optionally a fourth 
thermal transfer recording medium having a black heat-meltable ink layer 
on a fourth foundation (hereinafter referred to as "thermal transfer 
recording medium C"). 
An embodiment of the melt-type thermal transfer recording medium for 
forming a transparent ink image in accordance with the present invention 
is one wherein the aforesaid transparent heat-meltable ink layer is 
disposed on a foundation (hereinafter referred to as "thermal transfer 
recording medium D"). 
In the present invention, the colored ink and the transparent ink may be 
disposed in a side-by-side relation on a single foundation. For example, 
one can use the above-mentioned thermal transfer recording medium for 
forming single color images modified such that a colored ink layer and a 
transparent ink layer are alternately repeatedly disposed in a 
side-by-side relation on a foundation in the longitudinal direction 
thereof (hereinafter referred to as "thermal transfer recording medium 
E"). Further, one can use the above-mentioned color thermal transfer 
recording medium B modified such that a transparent ink layer is further 
included in the repeating unit comprising the yellow, magenta and cyan ink 
layers and optionally the black ink layer (hereinafter referred to as 
"thermal transfer recording medium F"). 
The thermal transfer recording method of the present invention will be 
explained using the intermediate transfer printer illustrated in FIG. 1. 
Of course, the present method can be practiced in the same manner using 
the intermediate transfer printer illustrated in FIG. 2. 
First the formation of single color image using the thermal transfer 
recording media A and D will be explained. The formation of an image on 
the intermediate transfer drum 10 is performed by selectively heating the 
thermal transfer recording medium A 12 according to image signals with the 
heating head 13 to soften or melt portions of the colored ink layer, which 
are transferred onto the surface of the intermediate transfer drum 10. 
While the intermediate transfer drum 10 and the thermal transfer recording 
medium A 12 are thus moved in the directions indicated by the arrows, 
respectively, portions of the colored ink layer are transferred onto the 
intermediate transfer drum 10, thereby forming an image 17 of the colored 
ink thereon. As the intermediate transfer drum 10 rotates, the image 17 of 
the colored ink is moved to the transfer part 14, pressed against an image 
receptor 15 to form a final image 18 of the colored ink thereon. Then, 
using the thermal transfer recording medium D, a region of the transparent 
ink is formed on the intermediate transfer drum 10 and the region of the 
transparent ink is transferred onto the image 18 of the colored ink on the 
image recetor 15 in the same manner as above. 
When using the thermal transfer recording medium E, an image of the colored 
ink and a region of the transparent ink are also formed successively on an 
image receptor in the same manner as above except that the colored ink 
layer and the transparent ink layer on the same recording medium are used. 
The formation of a multi-color or full-color image using the thermal 
transfer recording medium B or C and the thermal transfer recording medium 
D will now be explained. When forming a color image using the thermal 
transfer recording medium C, one uses an intermediate transfer printer 
wherein the recording part 11 shown in FIG. 1 or FIG. 2 is one equipped 
with respective heating heads 13 for transfer of yellow ink, magenta ink 
and cyan ink, and optionally black ink. 
The formation of a multi-color or full-color image using the thermal 
transfer recording media C and D can be performed by the following two 
methods: 
Method I 
Using, for example, a thermal transfer recording medium having a yellow ink 
layer among the three or four color ink layers, a yellow ink image is 
formed on the intermediate transfer drum 10 and the yellow ink image on 
the intermediate transfer drum 10 is transferred onto an image receptor 15 
in the same manner as in the above-mentioned formation of a single color 
image. Then, the formation of a magenta ink image, and a cyan ink image, 
and optionally a black ink image are successively performed in the same 
manner as above. In that case, when one color signal among yellow, magenta 
and cyan color signals is absent, the formation of the corresponding color 
ink image is not performed. When a black image is formed by 
superimposition of the yellow, magenta and cyan ink layers, it is not 
required to use a thermal transfer recording medium having a black ink 
layer. The order of transfer of the respective color ink layers can be 
arbitrarily determined. 
Thus, a multi-color or full-color ink image including regions wherein at 
least two of the yellow, magenta and cyan ink layers are superimposed to 
develop a color by virtue of subtractive color mixture is obtained on the 
image receptor 15. 
Then, using the thermal transfer recording medium D, a region of the 
transparent ink is formed on the intermediate transfer drum 10 and the 
region of the transparent ink is transferred onto the color ink image on 
the image receptor 15 in the same manner as above. 
Method II 
Using, for example, a thermal transfer recording medium having a yellow ink 
layer among the three or four color ink layers, a yellow ink image is 
formed on the intermediate transfer drum 10 in the same manner as in the 
above-mentioned formation of a single color image. Then, using of a 
thermal transfer recording medium having a magenta ink layer and a thermal 
transfer recording medium having a cyan ink layer, and optionally a 
thermal transfer recording medium having a black ink layer, the formation 
of a magenta ink image and a cyan ink image, and optionally a black ink 
image are successively formed on the intermediate transfer drum 10. In 
that case, when one color signal among yellow, magenta and cyan color 
signals is absent, the formation of the corresponding color ink image is 
not performed. When a black image is formed by superimposition of the 
yellow, magenta and cyan ink layers, it is not required to form the black 
ink image using the black ink layer. The order of transfer of the 
respective color ink layers can be arbitrarily determined. 
Thus, a multi-color or full-color ink image including regions wherein at 
least two of the yellow, magenta and cyan ink layers are superimposed to 
develop a color by virtue of subtractive color mixture is obtained on the 
intermediate transfer drum 10. 
The multi-color or full-color ink image formed on the intermediate transfer 
drum 10 is transferred onto an image receptor 15 in the same manner as in 
the formation of a single color image. 
Then, using of the thermal transfer recording medium D, a region of the 
transparent ink is formed on the intermediate transfer drum 10 and the 
region of the transparent ink is transferred onto the color ink image on 
the image receptor 15 in the same manner as above. 
The formation of a multi-color or full-color image using the thermal 
transfer recording medium B and the thermal transfer recording medium D 
can be performed in the same manner as in Method I or Method II except 
that the respective color ink layers on the same recording medium are used 
to form a multi-color or full-color image on an image receptor 15. 
Further, the formation of a multi-color or full-color image using the 
thermal transfer recording medium F can also be performed in the same 
manner as in Method I or Method II except that the respective color ink 
layers and the transparent ink layer on the same recording medium are used 
to form a multi-color or full-color ink image on an image receptor, and 
then to form a region of the transparent ink on the multi-color or 
full-color ink image. 
In the method of the present invention, it is sufficient that the region 
where the transparent ink is transferred is substantially the same as or 
larger than the region of the colored ink image which has been previously 
transferred on the image receptor. It is particularly preferable to 
transfer the transparent ink in substantially the same region as the 
region of the colored ink image because the texture or touch of the region 
of the image receptor where the colored ink image is not formed is not 
injured. 
As the image receptor useful in the method of the present invention various 
materials such as paper sheets, plastic films or sheets, fabrics and 
nonwoven fabrics are exemplified. 
In particular, when an OHP sheet is used as the image receptor and the 
colored ink image (inclusive of single color image and multi-color or 
full-color image) is formed on the OHP sheet by using one or more of 
yellow, magenta and cyan inks as the heat-meltable colored ink, it is 
preferable to use yellow, magenta and cyan inks each capable of forming a 
region of single color image having a maximum transmittance of not less 
than 50% in the visible region, provided that the region of the single 
color image is formed by transferring each ink onto the OHP sheet to form 
an ink image of single color thereon and transferring the transparent 
heat-meltable ink onto the ink image of single color. The obtained OHP 
sheet with a color image gives a projected image of a vivid or clear color 
when projected by means of an OHP. Herein the transmittance value is a 
value obtained by subtracting the transmittance value of the foundation 
from the observed value (hereinafter the same). 
The present invention will be more fully described by way of the following 
Examples. It is to be understood that the present invention is not limited 
to the Examples, and various changes and modifications may be made in the 
invention without departing from the spirit and scope thereof. 
Production of thermal transfer recording media 
Onto the front side of a 3.5 .mu.m-thick polyethylene terephthalate film 
which was provided on the back side thereof with a heat-resistant 
stick-preventive layer were applied the colored inks of respective colors 
each having the formula shown in Table 1 by a hot-melt coating method to 
give a color thermal transfer recording medium wherein yellow, magenta and 
cyan ink layers were repeatedly disposed in a side-by-side relation on the 
foundation film in the longitudinal direction thereof. 
TABLE 1 
______________________________________ 
Yellow ink 
Magenta ink 
Cyan ink 
______________________________________ 
Ink formula (% by weight) 
Paraffin wax 60 60 60 
Candelilla wax 
10 10 
.alpha.-Olefin-maleic 
10 
10 10 
anhydride copolymer wax 
Ethylene-vinyl 
5 5 
acetate copolymer 
Disazo Yellow -- -- 
Brilliant Carmine 6B 
-- 15 -- 
Phthalocyanine Blue 
-- 
-- 15 
Physical properties of ink layer 
Coating amount (g/m.sup.2) 
2.0 2.0 2.0 
Softening point (.degree. C.) 
72 72 72 
Melt viscosity 
110 120 
(cps/100.degree. C.) 
______________________________________ 
Onto the front side of a 3.5 .mu.m -thick polyethylene terephthalate film 
which was provided on the back side thereof with a heat-resistant 
stick-preventive layer was applied the heat-meltable ink having the 
formula shown in Table 2 by a hot-melt coating method to give a thermal 
transfer recording medium having a transparent ink layer (hereinafter 
referred to as "transparent thermal transfer recording medium"). 
TABLE 2 
______________________________________ 
Transparent ink 
A B 
______________________________________ 
Ink formula (% by weight) 
Ethylene-vinyl 10 17 
acetate copolymer 
Candelilla wax 30 45 
Carnauba wax 38 18 
Alicyclic saturated 15 
hydrocarbon resin 
Synthetic petroleum resin 
-- 15 
Physical properties of ink layer 
Coating amount (g/m.sup.2) 
6.0 6.0 
Softening point (.degree. C.) 
75 73 
Melt viscosity (cps/100.degree. C.) 
2500 
______________________________________ 
Examples 1 and 2 and Comparative Example 
With use of the thus obtained color thermal transfer recording medium, 
single color ink images of yellow, magenta and cyan were formed on an 
image receptor (Xerox 4024 paper sheet made by Xerox Corporation or OHP 
sheet made by Minnesota Mining and Manufacturing Company) by means of an 
intermediate transfer printer (test machine). The printer had 
substantially the same construction as illustarated in FIG. 1. The 
intermediate transfer drum used was one coated with a silicone rubber at 
its surface. The intermediate transfer drum was used under the condition 
of being heated to 55.degree. C. at its surface. The contact pressure 
between the intermediate transfer drum and the pressing roller was set to 
a value of 100 kg/30 cm. 
Then, using of the transparent thermal transfer recording medium, the 
transparent ink was solid-printed onto the respective color ink images 
formed on the image receptor by means of the aforesaid intermediate 
transfer printer. In the Comparative Example the transparent ink was not 
transferred onto the respective color ink images formed on the image 
receptor. 
With respect to the respective color ink images formed on the paper sheet, 
Xerox 4024, the degree of luster was evaluated through the visual 
observation 
Further, with respect to the color images formed on the OHP sheet, the 
maximum transmittance of the yellow, magenta and cyan regions in the 
visual region (value measured at 650 nm for yellow, 650 nm for magenta and 
500 nm for cyan) was measured by means of a spectrophotometer, MS-2020 
made by Macbeth corp. 
The results thereof are shown in Table 3. 
TABLE 3 
______________________________________ 
Paper sheet OHP sheet 
Transparent (Xerox 4024) 
Transmittance (%) 
ink Luster Yellow Magenta 
Cyan 
______________________________________ 
Ex. 1 A Good 65 66 65 
Ex. 2 B Good 
63 
63 
60 
Com. Ex. 
None 
None 
42 
45 
40 
______________________________________ 
According to the intermediate transfer type thermal transfer recording 
method of the present invention, a lustrous image is provided on a paper 
sheet as an image receptor and an image with high light transmittance is 
provided on an OHP sheet as an image receptor, resulting in a clear or 
vivid projected image. 
In addition to the materials and ingredients used in the Examples, other 
materials and ingredients can be used in the present invention as set 
forth in the specification to obtain substantially the same results.