Thermosensitive image transfer recording medium

A thermosensitive image transfer recording medium comprising a support material; an image transfer layer formed on the support material, comprising a fine porous network structure made of a resin comprising cellulose acetate butyrate; a non-volatile oily material which is contained in the fine porous network structure, and which does not dissolve the resin of the fine porous network structure; and a thermofusible ink composition which is held in the fine porous network structure, comprising (a) a thermofusible wax material is solid at room temperature, and (b) a colorant.

BACKGROUND OF THE INVENTION 
The present invention relates to a thermosensitive image transfer recording 
medium capable of forming on a receiving sheet images having high image 
density, excellent image gradation and durability, with high thermal 
sensitivity by application of heat to an image transfer layer of the 
recording medium, for instance, through a thermal head or a laser beam 
application device so as to imagewise transfer a thermofusible ink 
composition contained in the image transfer layer to the receiving sheet, 
thereby recording images on the receiving sheet. The thermofusible ink 
composition comprises as the main components a colorant and a 
thermofusible wax material. 
More particularly, the present invention relates to a thermosensitive image 
transfer recording medium comprising a support material and an image 
transfer layer formed thereon, which image transfer layer comprises (i) a 
fine porous network structure made of a resin comprising a cellulose 
acetate butyrate, (ii) a non-volatile oily material which is contained in 
the fine porous network structure, and which does not dissolve the resin 
of the porous network structure, and (iii) a thermofusible ink composition 
held in the porous network structure, which comprises as the main 
components a colorant, and a thermofusible wax material which is solid at 
room temperature. 
Conventionally, there are known (i) a thermosensitive image transfer sheet 
comprising a support material and a sublimable dye layer formed on the 
support material, and (ii) a thermosensitive image transfer sheet 
comprising a support material and a thermofusible ink layer comprising a 
thermofusible material and a pigment which are homogeneously dispersed 
therein, capable of forming images on a receiving sheet by subjecting the 
thermosensitive image transfer medium to thermal printing. 
The method using a sublimable dye, however, is superior in the reproduction 
of image gradation, but has the drawbacks that the thermal sensitivity is 
low and the durability of the reproduced image is poor. On the other hand, 
the method using a thermofusible material and a pigment is superior in 
thermal sensitivity and the durability of the produced images, but has the 
drawback that the image gradation is unsatisfactory. 
Furthermore, there has been proposed a thermosensitive image transfer 
recording medium comprising a support material and a fine porous structure 
formed thereon, which contains a thermofusible ink composition consisting 
essentially of (a) a thermofusible material which is solid at room 
temperature and (b) a colorant. In comparison with the conventional 
thermofusible type recording mediums, the above proposed thermosensitive 
image transfer recording medium is improved on image gradation, but the 
image gradation obtained by this recording medium is not as good as that 
obtained by the recording medium using a sublimable dye. 
Further, in the case of the above thermosensitive image transfer medium, 
when image transfer is performed onto a receiving sheet having high 
smoothness such as a receiving sheet made of synthetic paper or high 
quality paper, high image density and precise image gradation can be 
obtained. However, when image transfer is performed onto a receiving sheet 
having a rough surface, for instance, having a smoothness of 100 seconds 
or less, clear images cannot be obtained due to the rough surface of the 
receiving sheet, with the formation of non-uniform solid images and poor 
image gradation. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a 
thermosensitive image transfer recording medium from which the above 
mentioned shortcomings of the conventional recording mediums have been 
eliminated, and which is superior in image producing stability and thermal 
sensitivity and capable of yielding images with high image density and 
excellent image gradation, even on a receiving sheet having a rough 
surface. 
The above object of the present invention is attained by a thermosensitive 
image transfer recording medium comprising a support material and an image 
transfer layer formed thereon, which image transfer layer comprises (i) a 
fine porous network structure made of a resin comprising a cellulose 
acetate butyrate, (ii) a non-volatile oily material which is contained in 
the fine porous network structure, and which does not dissolve the resin 
of the porous structure, and (iii) a thermofusible ink composition held in 
the porous network structure. The thermofusible ink composition comprises 
as the main components a colorant, and a thermofusible wax material which 
is solid at room temperature. 
In order to attain smooth image transfer with high image density and 
precise image gradation onto a receiving sheet having a rough surface, for 
instance, having a smoothness of 100 seconds or less, it is preferable 
that the content of the non-volatile oily material in the image transfer 
layer be in the range of about 20 to 50 wt. %, and the viscosity of the 
non-volatile oily material be 300 cps or less at 25.degree. C. 
In particular, in order to improve the image gradation, an image gradation 
control agent can be contained in the image transfer layer. 
Further, in order to improve the image producing stability, a protective 
layer can be formed on the back side of the support material opposite to 
the image transfer layer, which protective layer not only protects the 
support material from the heat applied thereto through a thermal head 
during the course of thermal printing, but also facilitates smooth running 
of the thermal head on the support material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the thermosensitive image transfer medium comprising a support material 
and an image transfer layer according to the present invention, it is 
considered that when heat is applied to the image transfer layer for image 
formation by means of a thermal head or the like, the thermofusible ink 
composition or the colorant gradually seeps from the fine pores of the 
network structure and is then transferred to a receiving sheet. 
The amount of the thermofusible ink composition or the colorant which seeps 
out varies in accordance with the amount of thermal energy applied to the 
image transfer layer. Therefore, the amount of the thermofusible ink 
composition or the colorant transferred can be accurately controlled by 
controlling the amount of thermal energy applied. Accordingly image 
reproduction with wide-range gradation can be attained, so that a clear 
image faithful to the original image can be reproduced. 
The amount of thermal energy to be applied of course varies, depending upon 
the specific materials employed in the thermosensitive image transfer 
recording medium and the thickness of the thermofusible image transfer 
layer. 
Preparation of Image Transfer Layer 
In the present invention, the image transfer layer can be prepared, for 
example, by the following method. 
A thermofusible wax material, a non-volatile oily material, and a colorant 
are mixed and dispersed in a suitable organic solvent using a dispersing 
device such as an attritor or a ball mill to obtain a thermofusible ink 
composition. 
It is considered that the non-volatile oily material employed above has at 
least two functions of (i) facilitating the smooth and uniform transfer of 
the thermofusible ink composition onto a receiving sheet having a rough 
surface by decreasing the viscosity of the thermofusible ink composition 
at the time of image transfer, particularly when the oily material is used 
in an amount of about 20 to 50 wt. % in the image transfer layer, and (ii) 
serving as an auxiliary agent for forming fine pores in the network 
structure made of the resin. To more facilitate the transfer of the 
thermofusible ink composition, it is preferable to employ a non-volatile 
oily material having a viscosity of 300 cps or less at 25.degree. C. in 
the above-mentioned amount. 
A resin comprising a cellulose acetate butyrate for forming the porous 
network structure is separately dissolved in an organic solvent or a mixed 
solvent such as methyl ethyl ketone and toluene to prepare a solution of 
the resin. 
This solution is mixed with the previously obtained ink dispersion. The 
mixture is then uniformly dispersed using a blender such as a ball mill. 
The thus obtained dispersion is then applied to a support material and 
dried, so that an image transfer layer, comprising a fine porous network 
structure made of the resin in which the thermofusible ink composition is 
held, is formed on the support material. 
A dispersing agent such as a non-ionic surfactant may be added to the above 
dispersion to facilitate the dispersion of the thermofusible wax material, 
the colorant and the oily material A commercially available example of the 
dispersing agent is Sorbon T-80, which is a non-ionic surfactant, sorbitan 
monoleate, made by Toho Chemical Industry Co., Ltd. 
In addition, commonly used humectants and fillers may be added, as 
required, to the above dispersion. 
An alternative method by which the image transfer layer is formed comprises 
the steps of kneading a material, which is not compatible with the resin 
for the fine porous network structure, but soluble in a solvent which will 
not dissolve the resin, together with the resin, applying the kneaded 
mixture to the surface of a support material to form a resin layer, 
dissolving the first mentioned material in the solvent to leave the fine 
porous resin structure on the support material, and filling the previously 
mentioned ink composition into the porous network structure, whereby an 
image transfer layer having the same structure as that of the first 
mentioned image transfer layer. 
Resins for Fine Porous Network Structure 
In the present invention, as a resin for forming porous network structure, 
a resin comprising a cellulose acetate butyrate is employed which is a 
mixed ester of cellulose containing acetyl groups and butyryl groups. The 
cellulose acetate butyrate can also be employed alone. 
Commercially available cellulose acetate butyrates can be classified into 
the following three types depending upon the content of butyryl group: 
(1) Low Butyryl Content Type (16 to 17%), m.p. 210.degree. C. or more 
(2) Medium Butyryl Content Type (27 to 38%), m.p. 155 to 210.degree. C. 
(3) High Butyryl Content Type (50%), m.p. 110.degree. to 160.degree. C. 
As can be seen from the above, the higher the content of butyryl group, the 
lower the melting point. In other words, the lower the content of butyryl 
group, the higher the melting point. 
Therefore, in the present invention, it is preferable to use the cellulose 
acetate butyrates of the medium and low butyryl group content types in 
view of the necessity for the heat resistance of the porous network 
structure. In other words, cellulose acetate butyrates having a butyryl 
content of 38% or less are preferable for use in the present invention. As 
a matter of course, the cellulose acetate butyrate of the low butyryl 
group content type is most preferable for use in the present invention. 
Non-volatile Oily Materials 
As the non-volatile oily material for use in the present invention, the 
following can be employed: 
Vegetable oils and animal oils such as cotton oil, rape oil and whale oil, 
mineral oils such as motor oil, spindle oil and dynamo oil. 
Further, as such oily material, lanolin fatty acid oil, lanolin fatty acid 
metal salt oil such as lanolin fatty acid calcium salt oil, and lanolin 
fatty acid ester oil can also be employed. Specific examples of such oils 
are Neocoat OES-181, OES-183, LFC-50M and LS-3102MB (made by Yoshikawa Oil 
& Fat Co., Ltd.). 
Further, it is preferable that the oily material for use in the present 
invention have a viscosity of 300 cps or less at 25.degree. C. for 
attaining more uniform and more smooth image transfer onto a receiving 
sheet having a rough surface. 
This phenomenon can be explained by using the following Olson-Peel's 
Formula concerning the osmosis of liquid into a paper including numerous 
capillaries under application of an external pressure to the paper. This 
formula indicates the permeating depth d of the liquid into the paper at 
the moment an external pressure is applied thereto: 
##EQU1## 
where P represents the external pressure, r represents the diameter of 
each capillary in the paper, t represents time, and .eta. represents the 
viscosity of the liquid. The above formula indicates that when P, r and t 
are constant, the permeating depth d, of the liquid, that is, the amount 
of the transferred liquid into the paper, increases as the viscosity 
.theta. of the liquid decreases. 
Specific examples of a non-volatile oily material having a viscosity of 300 
cps or less at 25? C. for use in the present invention are as follows, 
which are made by Itoh Oil Manufacturing Co., Ltd: 
(1) Esters derived from high alcohols and the following fatty acids: 
______________________________________ 
Viscosity 
Trademark Fatty Acids (cps/25.degree. C.) 
______________________________________ 
HISORATE = 4 Ricinoleic Acid 53.6 
HISORATE = 5 Isocaprylic Acid 8.8 
HISORATE = 7 "Versatic" Acid 12.7 
HISORATE = 10 
Isostearic Acid 24.3 
HISORATE = 11 
Stearic Acid 20.0 
HISORATE = 22 
12-hydroxystearic Acid 
51.4 
HISORATE = 101 
Capric Acid 22.2 
HISORATE = 105 
Isocaprylic Acid 24.2 
HISORATE = 107 
"Versatic" Acid 36.8 
HISORATE = 108 
"Dimer Acid" 36.0 
HISORATE = 110 
Isostearic Acid 56.0 
HISORATE = 111 
Stearic Acid 36.8 
HISORATE = 117 
Oleic Acid 80 
HISORATE = 122 
12-hydroxystearic Acid 
Paste 
______________________________________ 
(2) Hydroxy Fatty acid Esters 
______________________________________ 
Viscosity 
Trademark Composition (cps/25.degree. C.) 
______________________________________ 
CO-FA Methyl 
Methyl Ricinolate 
40 
CO-FA Methyl-D 
Methyl Ricinolate 
30 
(distilled) 
CO-FA Ethyl-D 
Ethyl Ricinolate 
30 
(distilled) 
CO-FA Butyl Butyl Ricinolate 
40 
MAR Methylacetyl Ricinolate 
13 
BAR Butylacetyl Ricinolate 
17 
______________________________________ 
(3) Others 
______________________________________ 
Material Viscosity (cps/25.degree. C.) 
______________________________________ 
Soybean Oil 120 
Peanut Oil 150 
Liquid Paraffin 
250 
______________________________________ 
The above oily materials contain volatile components (at 120.degree. C.) in 
an amount of 1.0 wt. % or less. The esters derived from higher alcohols 
given in (1) are most preferable for use in the present invention in view 
of the use of the thermosensitve image transfer recording medium over an 
extended period of time. 
Thermofusible Wax Materials 
The thermofusible wax materials for use in the present invention are as 
follows: 
(1) Animal Waxes 
As the animal wax for use in the present invention, a lanolin derivative 
wax can be employed. 
Examples of a lanolin derivative wax are reduced lanolin, hard lanolin, 
lanolin alcohol, hydrogenated lanolin alcohol, lanolin fatty acid, metal 
salts of lanolin fatty acid, esters of lanolin fatty acid, and mixtures 
thereof. These waxes are solid at room temperature and become liquid when 
heated above their respective melting points. Of the above lanolin 
derivative waxes, lanolin fatty acid, metal salts of lanolin fatty acid, 
esters of lanolin fatty acid and mixtures thereof are particularly 
preferable for use in the present invention. 
It is preferable that lanolin fatty acid for use in the present invention 
comprise a hydroxylated fatty acid, an iso-fatty acid, and an 
anti-iso-fatty acid, each having 13 to 33 carbon atoms. 
As the metal salts of the lanolin fatty acid, for example, sodium salt, 
potassium salt, calcium salt, magnesium salt, barium salt, zinc salt, lead 
salt, manganese salt, iron salt, nickel salt, cobalt salt and aluminum 
salt can be employed. 
Further as the esters of lanolin fatty acid, for example, esters of methyl 
alcohol, ethyl alcohol, butyl alcohol, glycerin, pentaerythritol, 
polypropylene glycol and trimethylolpropane can be employed. These esters 
can be employed alone or in combination with the above-mentioned metal 
salts. 
Commercially available waxes containing the above metal salts of lanolin 
fatty acid are LANOX HHY-50, LANOX HH-73, and LANOX HHC-82 (made by 
Yoshikawa Oil & Fat Co., Ltd.). 
(2) Mineral Waxes 
As the mineral wax for use in the present invention, montan wax can be 
employed, which is derived by extraction of lignite or by purification of 
a crude product obtained by the above extraction. 
Of the above waxes, waxes having a melting point in the range of 60.degree. 
C. to 100.degree. C. are preferable for use. 
Instead of the above natural waxes, synthetic waxes such as polyethylene 
wax and polyester-based wax can be employed. 
The lanolin derivative wax and montan wax may be used in combination with a 
conventionally employed thermofusible material, with a mixing ratio by 
weight of the wax to the thermofusible material being 1 : not more than 1. 
Examples of such thermofusible material are waxes such as carnauba wax, 
paraffin wax, microcrystalline wax and castor wax; higher fatty acids, 
metal salts and esters of higher fatty acids such as stearic acid, 
palmitic acid, lauric acid, aluminum stearate, lead stearate, barium 
stearate, zinc stearate, zinc palmitate, methylhydroxy stearate, glycerol 
monohydroxy stearate; homopolymers and copolymers such as polyethylene, 
polypropylene, polyisobutylene, polyethylene wax, polyethylene oxide, 
polytetrafluoroethylene, ethylene--acrylic acid copolymer, ethylene--ethyl 
acrylate copolymer, ethylene--vinyl acetate copolymer. These thermofusible 
materials can be employed either alone or in combination when mixed with 
the lanolin derivative wax or montan wax. 
It is preferable that the lanolin derivative wax, montan wax or the above 
mentioned mixture be employed in an amount of 50 to 200 parts by weight to 
100 parts by weight of the resin which constitutes the fine porous network 
structure. 
Colorants 
As the colorant for use in the present invention, the following dyes and 
pigments are preferably employed for obtaining images with excellent image 
gradation: 
Examples of such dyes are direct dyes, acid dyes, basic dyes, mordant dyes, 
sulfur dyes, building dyes, azoic dyes, oil dyes and thermosublimable 
disperse dyes. 
Specific examples of the above dyes are as follows: 
(1) Direct Dyes: 
Direct Sky Blue and Direct Black W 
(2) Acid Dyes: 
Tartrazine, Acid Violet 6B and Acid Fast Red 3G 
(3) Basic Dyes: 
Safranine, Auramine, Crystal Violet, Methylene Blue, Rhodamine B and 
Victoria Blue B. 
(4) Mordant Dyes: 
Sunchromine Fast Blue MB, Eriochrome Azurol B and Alizarin Yellow 
(5) Sulfur Dyes: 
Sulphur Brilliant Green 4G 
(6) Building Dyes: 
Indanthrene Blue 
(7) Azoic Dyes: 
Naphthol AS 
(8) Oil Dyes: 
Nigrosin, Spirit Black EB, Varifast Orange 3206, Oil Black 215, Butter 
Yellow, Sudan Blue II, Oil Red B and Rhodamine B 
(9) Disperse Dyes: 
(9-1) Monoazo Disperse Dyes: Disperse Fast Yellow G, Disperse Fast Yellow 
5G, Disperse Fast Yellow 5R and Disperse Fast Red R; 
(9-2) Anthraquinone Disperse Dyes: Disperse Fast Violet OR, Disperse Fast 
Violet B, Disperse Blue Extra and Disperse Fast Brilliant Blue B; and 
(9-3) Nitrodiphenylamine Disperse Dyes: Disperse Fast Yellow RR and 
Disperse Fast Yellow GL 
In addition to the above dyes, the following commercially available 
colorants can be employed in the present invention: Neoazpon Red 346, 
Neozapon Blue 807, Neozapon Yellow 157, Kayaset Black, Spilon Blue 2BNH, 
Spilon Red GRLT, Spilon Red GRLT Special, Sudan Red 460, Sudan Blue 670, 
and Sudan Yellow 150. 
Further in the present invention, a finely-divided pigment can also be 
employed as the colorant. As such a finely-divided pigment, it is 
preferable that the particle size be not more than 1.0 .mu.m, more 
preferably not more than 0.5 .mu.m, after sufficient dispersion. 
Specific examples of such finely-divided pigments are the following 
pigments which are commercially available from Hoechst: 
Permanent Yellow GG 02 (C.I. Pigment Yellow 17), 
Permanent Yellow DHG trans 02 (C.I. Pigment Yellow 12), 
Novoperm Yellow HR 03 (C.I. Pigment Yellow 83), 
Hansa Brilliant Yellow 5GX 02 (C.I. Pigment Yellow 74), 
Permanent Orange RL 01 (C.I. Pigment Orange 34), 
Novoperm Red HFG (C.I. Pigment Orange 38), 
Novoperm Red HFT (C.I. Pigment Red 175), 
Permanent Lake Red LCLL 02 (C.I. Pigment Red 53:1), 
Novoperm Red HF 4B (C.I. Pigment Red 187), 
Permanent Carmine FBB02 (C.I. Pigment Red 146), 
Permanent Rubine L 6B (C.I. Pigment Red 57:1), 
Hostaperm Pink E trans (C.I. Pigment Red 122), and 
Reflex Blue R50 (C.I. Pigment Blue 61). 
In addition to the above, carbon black can be employed. 
Further, in the present invention, the following monoazo pigments having 
the following general formula can also be used as colorant: 
EQU X-N.dbd.N-Y 
where X represents a diazonium salt moiety and Y represents a coupler 
moiety. 
(1) Sico Fast Yellow D 1355 (made by BASF) 
(2) Sico Fast Yellow D 1250 (made by BASF) 
(3) Lake Red LC (made by Hoechst) having the formula: 
##STR1## 
(4) Lake Red C 405 (made by Dainichi Seika Color and Chemicals Mfg. Co., 
Ltd.) 
(5) Fast Red 1547 (made by Dainichi Seika Color and Chemicals Mfg. Co., 
Ltd.) having the formula: 
##STR2## 
It is preferable that these colorants be in a dissolved or finely dispersed 
state in the thermosensitive ink composition. When the previously 
mentioned dyes are used in combination with the above pigments, it is 
preferable that the colors of the pigments be the same as or similar to 
the colors of the dyes. 
Image Gradation Control Agents 
In the present invention, an image gradation control agent can also be 
added to the image transfer layer in order to improve the image gradation 
of the images to be obtained. 
The image gradation control agent for use in the present invention is more 
wetting and more compatible with the resin for the fine porous network 
structure than with the main components of the thermofusible ink 
composition such as the thermofusible wax material and is firmly held 
within the fine porous network structure and functions to precisely 
control the amount of the thermofusible ink composition transferred from 
the image transfer layer. It is considered that the image gradation 
control agent is able to precisely control the surface pore diameter of 
the fine porous network structure so as to make the pore diameter small, 
and when thermal energy is applied to the image gradation control agent, 
the image gradation control agent remains in the fine porous network 
structure, without being transported outside the porous network structure, 
thereby controlling the amount of the thermofusible ink composition 
transferred from the image transfer layer. Therefore, as such image 
gradation control agents, any materials can be employed as long as they 
work in the above-described manner. Specific examples of such image 
gradation control agents may be, but not restricted to, the following: 
(a) Needle-like Pigments 
As such needle-like pigments, not only inorganic pigments, but also organic 
pigments can be employed as long as they are in the form of needle and can 
constitute a network in the image transfer layer. 
Specific ex:unples of such needle pigments are ochre, Chrome Yellow G, 
Phthalocyanine pigments such as Phthalocyanine Blue, Lithol Red, BON 
Maroon Light, terra abla, needle zinc oxide, 
2,7-bis[2-hydroxy-3-(2-chlorophenylcarbamoyl)naphthalene-1-ylazo]-9-fluore 
none, 4',4"-bis 
[2-hydroxy-3-(2,4-dimethylphenyl)carbamoylnaphthalene-1-ylazo]-1,4-distyry 
lbenezene. 
(b) Azo Pigments 
An azo pigment having the following general formula: 
EQU X--(N.dbd.N-Y)n 
where X represents a diazonium salt moiety, Y is a coupler moiety, and n is 
an integer of 1, 2 or 3. 
(c) Phthalocyanine Pigments 
Metal-free phthalocyanine, metal-free phthalocyanine derivatives, metal 
phthalocyanine and metal phthalocyanine derivatives can be employed. 
It is preferable that the amount of the image gradation control agent be 
0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, to 1 
part by weight of the colorant in the image transfer layer. 
Support Material 
As the support material for use in the present invention, conventional 
films and papers employed in the field of thermosensitive recording can be 
used. More specifically, heat resistant plastic films made of polyester 
such as polyethylene terephthalate, polycarbonate, triacetyl cellulose, 
nylon or polyimide, cellophane, condenser paper and parchment paper are 
preferably employed as the support material. When a thermal head is 
employed as heat application device, it is preferable that the thickness 
of the support material 1 be about 2 to 15 .mu.m. By contrast, when laser 
beams are employed as the heat application device, the thickness of the 
support material is not always restricted to the above mentioned range. 
When a thermal head is employed, the heat resistance of the support 
material can be improved by coating the surface of the support material 
which comes into contact with the thermal head with a heat resistant 
protective layer comprising, for instance, silicone resin, 
fluorine-contained resin, polyimide resin, epoxy resin, phenolic resin, 
melamine resin or nitrocellulose. 
Protective Layer 
In the present invention, a protective layer can be formed on the back side 
of the support material opposite to the image transfer layer, which serves 
to protect the support material from the heat applied thereto during 
thermal recording and facilitate smooth movement of a thermal head on the 
support material, thereby obtaining image with excellent image gradation 
in a stable manner. 
Such a protective layer can be made using as the main component a 
thermosetting, ultraviolet ray (UV) setting or electron beam (B) setting 
acrylic resin. Finely-divided inorganic or organic particles can be 
contained or dispersed in the protective layer. 
The finely-divided organic or inorganic particles to be mixed with the 
above acrylic resins are not restricted to particles made of a particular 
material, but a variety of materials can be employed for such particles. 
For example, silica, alumina, titanium oxide, zinc oxide, calcium 
carbonate, aluminum carbonate, cobalt stearate, carbon fluoride, ethylene 
fluoride resin, polyimide resin and other hardened polymer beads can be 
employed. 
It is preferable that the amount of the finely-divided particles be in the 
range of 0.1 to 100 parts by weight to 1 part by weight of the 
thermosetting acrylic resin. 
With respect to the particle size of the finely-divided particles, the 
smaller, the better, since the smaller the particle size, the less the 
image quality is affected by the presence of the particles. Generally, it 
is preferable that the average particle size be 5 .mu.m or less. 
When forming a protective layer on the support material made of a polyester 
film, the above-mentioned thermosetting acrylic resins or a UV or EB 
setting acrylic resin, and the finely-divided particles are dispersed in a 
solvent, and the thus prepared dispersion is coated on the support 
material by use of a wire bar, air-knife, roll, or by gravure or by a 
screen coating process. It is preferable that the thickness of the coated 
protective layer be in the range of 0.1 to 8 .mu.m, more preferably in the 
range of 0.5 to 3 um, in view of the necessary heat resistance and 
smoothness. 
Intermediate Layer 
In order to more firmly fix the above described porous network structure to 
the support material, thereby obtaining images with excellent image 
gradation, an intermediate layer may be interposed between the support 
material and the image transfer layer. Such intermediate layer can be made 
of a plastic resin or a filler-containing plastic resin. 
In particular, for obtaining images with excellent image gradation, it is 
preferable to use a resin which is partly soluble in or compatible with 
the resin of which the porous network structure is composed. 
Receiving Sheet 
As the receiving sheet to be used in combination with the thermosensitive 
image transfer recording medium according to the present invention, 
conventional plain paper and synthetic paper can be employed. In order to 
facilitate the transfer of the coloring agent from the image transfer 
recording medium to the receiving sheet, it is preferable that a filler 
such as the above-mentioned resins, TiO.sub.2, silica or ZnO be contained 
in such papers. 
When thermal printing is performed by use of the thermosensitive image 
transfer recording medium according to the present invention, the 
recording medium is superimposed on the receiving sheet in such a manner 
that the image transfer layer comes into close contact with the receiving 
sheet, and heat is applied imagewise on the back side of the support 
material opposite to the image transfer layer by a heat application means 
such as a thermal head and a laser beam application device, thereby 
causing the thermofusible ink composition to melt and ooze from the porous 
network structure, and imagewise transferring the thermofusible ink 
composition onto the receiving sheet. 
By referring to the following examples, the present invention will now be 
explained more specifically: 
EXAMPLE 1 
(1) Preparation of Thermosensitive Image Transfer Recording Medium No. 1 
A mixtue of the following components was dispersed in a ball mill at 
68.degree. C. for about 48 hours: 
______________________________________ 
Parts by Weight 
______________________________________ 
Neozapon Blue 807 (Colorant) 
10 
(made by BASF) 
2,7-bis [2-hydroxy-3-(2-chlorophenyl- 
10 
carbamoyl)naphthalene-1-ylazo]- 
9-fluorenone (Gradation Control 
Agent) 
Modified Lanolin Oil 30 
Carnauba Wax 20 
Paraffin Wax 20 
Sorbon T-80 (Non-ionic surfactant, 
0.5 
sorbitan monooleate, made by Toho 
Chemical Industry Co., Ltd.) 
(Dispersing Agent) 
Liquid paraffin 5 
Methyl ethyl ketone 100 
Toluene 130 
______________________________________ 
To the above dispersion, 300 parts by weight of a 10 wt. % cellulose 
acetate butyrate solution comprising (i) a cellulose acetate butyrate with 
a butyryl group content of 17% (m.p. 230.degree..about.240.degree. 
C.)(made by Kanto Chemical Co., Ltd.), (ii) toluene and (iii) methyl ethyl 
ketone, with the mixing ratio by weight thereof respectively being 
10:20:20, were added. The mixture was dispersed for about 1 hour in a ball 
mill, so that an image transfer layer coating liquid was prepared. 
The thus prepared image transfer layer coating liquid was coated by a wire 
bar on the front side of a polyester film having a thickness of 6 .mu.m, 
backed with a silicone resin heat resistant layer, and was then dried at 
100.degree. C. for 1 minute, so that an image transfer layer having a 
thickness of about 5 .mu.m was formed on the polyester film, whereby a 
thermosensitive image transfer recording medium No. 1 according to the 
present invention was prepared. 
(2) Image Transfer Tests by Use of Thermosensitive Image Transfer Recording 
Medium No. 1 
Image Transfer Recording Medium No. 1 was super-imposed on a sheet of 
synthetic paper in such a manner that the image transfer layer came into 
close contact with the synthetic paper. A thermal head was then applied to 
the back side of the image transfer recording medium, with the applied 
thermal energy per dot varied o 0.5 mJ, 1.0 mJ, 1.5 mJ, 2.0 mJ and 2.5 mJ, 
so that the image densities of the respective images obtained were 
measured by a Macbeth densitometer. As a result, images with a cyan color 
having the image gradation as shown by Curve Ex. No. 1 in FIG. 1 was 
obtained. 
(3) Heat Resistance and Light Resistance of the Image obtained by 
Thermosensitive Image Transfer Recording Medium No. 1 
The image density of the cyan images recorded on the thermosensitive image 
transfer recording medium No. 1 was scarcely changed either when the 
recording medium was placed in an atmosphere at 60.degree. C. for 50 hours 
by means of a thermostat or when the recording medium was exposed to light 
by a standard fade meter for 24 hours. 
Comparative Example 1-1 
Example 1 was repeated except that the cellulose acetate butyrate employed 
in Example 1 was replaced by a polyester resin (Vylon 200 made by Toyobo 
Co., Ltd.), whereby a comparative thermosensitive image transfer recording 
medium No. 1-1 was prepared. 
Thermal printing was performed on this comparative thermosensitive image 
transfer recording medium in the same manner as in Example 1. The result 
was that a half-tone image was not obtained. 
Comparative Example 1-2 
Example 1 was repeated except that the cellulose acetate butyrate employed 
in Example 1 was replaced by a polycarbonate resin (G.E. LEXAN 141-111 
made by Engineering Plastics, Ltd.), whereby a comparative thermosensitive 
image transfer recording medium No. 1-2 was prepared. 
Thermal printing was performed on this comparative thermosensitive image 
transfer recording medium in the same manner as in Example 1. The result 
was that a half-tone image was not obtained. 
Comparative Example 1-3 
Example 1 was repeated except that the cellulose acetate butyrate employed 
in Example 1 was replaced by a styrene-acryl copolymer resin (RTR-28 made 
by Fujikura Kasei Co., Ltd.), whereby a comparative thermosensitive image 
transfer recording medium No. 1-3 was prepared. 
Thermal printing was performed on this comparative thermosensitive image 
transfer recording medium in the same manner as in Example 1. The result 
was that a half-tone image was not obtained. 
Comparative Example 1-4 
Example 1 was repeated except that the cellulose acetate butyrate employed 
in Example 1 was replaced by a nitrocellulose resin ("DN type" made by 
Daicel Chemical Industries, Ltd.), whereby a comparative thermosensitive 
image transfer recording medium No. 1-4 was prepared. 
Thermal printing was performed on this comparative thermosensitive image 
transfer recording medium in the same manner as in Example 1. As a result, 
an image with a cyan color having the image gradation as shown by Curve 
Comp. Ex. No. 1-4 in FIG. 1 was obtained. 
Comparative Example 1-5 
Example 1 was repeated except that the cellulose acetate butyrate employed 
in Example 1 was replaced by a vinyl chloride--vinyl acetate copolymer 
(VYHH made by Union Carbide Co., Ltd.), whereby a comparative 
thermosensitive image transfer recording medium No. 1-5 was prepared. 
Thermal printing was performed on this comparative thermosensitive image 
transfer recording medium in the same manner as in Example 1. As a result, 
an image with a cyan color having the image gradation as shown by Curve 
Comp. Ex. No. 1-5 in FIG. 1 was obtained. 
EXAMPLE 2 
Example 1 was repeated except that the Neozapon Blue 807 (Colorant) 
employed in Example 1 was replaced by Spilon Red GRLT Special (made by 
Hodogaya Chemical Co., Ltd), whereby a thermosensitive image transfer 
recording medium No. 2 according to the present invention was prepared. 
Thermal printing was performed on this thermosensitive image transfer 
recording medium in the same manner as in Example 1. As a result, a 
magenta image having the image gradation as shown by Curve Ex. No. 2 in 
FIG. 1 was obtained. This curve indicates that the image gradation was 
suitable for use in practice. 
The image density of the cyan image recorded on the thermosensitive image 
transfer recording medium No. 2 was scarcely changed either when the 
recording medium was placed in an atmosphere at 60.degree. C. for 50 hours 
or when the recording medium was exposed to light by a standard fade meter 
for 24 hours. 
EXAMPLE 3 
Example 1 was repeated except that the Neozapon Blue 807 (Colorant) 
employed in Example 1 was replaced by Neozapon Yellow R (made by BASF), 
whereby a thermosensitive image transfer recording medium No. 3 according 
to the present invention was prepared. 
Thermal printing was performed on this thermosensitive image transfer 
recording medium in the same manner as in Example 1. As a result, a yellow 
image having the image gradation as shown by Curve Ex. No. 3 in FIG. 1 was 
obtained. 
The image density of the yellow image recorded on the thermosensitive image 
transfer recording medium No. 3 was scarcely changed either when the 
recording medium was placed in an atmosphere at 60.degree. C. for 50 hours 
or when the recording medium was exposed to light by a standard fade meter 
for 24 hours. 
EXAMPLE 4 
A mixture of the following components was dispersed in a ball mill at 
68.degree. C. for about 48 hours: 
______________________________________ 
Parts by Weight 
______________________________________ 
Neozapon Black RE (Colorant) 
8 
(made by BASF) 
Heltogen Blue D 7030 (Colorant) 
15 
(made by BASF) 
Machine Oil 20 
Carnauba Wax 20 
Castor Wax 20 
Sorbon T-80 (Non-ionic surfactant, 
0.4 
sorbitan monooleate, made by Toho 
Chemical Industry Co., Ltd.) 
(Dispersing Agent) 
Liquid paraffin 4 
Methyl ethyl ketone 100 
Toluene 130 
______________________________________ 
To the above dispersion, 300 parts by weight of a 10 wt. % cellulose actate 
butyrate solution compriisng (i) a cellulose actate butyrate resin with a 
butyryl group content of 37%, (m.p. 155.degree..about.165.degree. C.) 
(CAB-381-0.5 made by Eastman Kodak Company), (ii) toluene and (iii) methyl 
ethyl ketone, with the mixing ratio by weight thereof respectively being 
10:20:20 were, added. The mixture was dispersed for about 1 hour in a ball 
mill, so that an image transfer layer coating liquid was prepared. 
The thus prepared image transfer layer coating liquid was coated by a wire 
bar on the front side of a polyeseer film having a thickness of 6 .mu.m, 
backed with a silicon. resin heat resistant layer, and was then dried at 
100.degree. C. for 1 minute, so that an image transfer layer having a 
thickness of about 4 .mu.m was formed on the polyester film, whereby a 
thermosensitive image transfer recording medium No. 4 according to the 
present invention was prepared. 
Thermal printing was performed on this thermosensitive image transfer 
recording medium in the same manner as in Example 1. As a result, a black 
image having the image gradation as shown by Curve Ex. No. 4 in FIG. 1 was 
obtained. 
The image density of the black image recorded on the thermosensitive image 
transfer recording medium No. 4 was scarcely changed either when the 
recording medium was placed in an atmosphere at 60.degree. C. for 50 hours 
or when the recording medium was exposed to light by a standard fade meter 
for 24 hours. 
Example 5-1 
A mixture of the following components was dispersed in a ball mill at 
85.degree. C. for about 24 hours: 
______________________________________ 
Parts by Weight 
______________________________________ 
Neozapon Blue 807 (Colorant) 
3 
(made by BASF) 
Lanolin Fatty Acid Oil 
2.15 
(Neocoat OES-183 made by 
Yoshikawa Oil & Fat Co., Ltd.) 
(Oily Material) 
Carnauba Wax (Carnauba Wax No. 1 
6 
made by Noda Wax Co., Ltd.) 
Sorbon T-80 (Non-ionic surfactant, 
0.12 
sorbitan monooleate, made by Toho 
Chemical Industry Co., Ltd.) 
(Dispersing Agent) 
Liquid paraffin 1.25 
Methyl ethyl ketone 20 
Toluene 50 
______________________________________ 
To the above dispersion, 45 parts by weight of a 20 wt. % cellulose acetate 
butyrate solution comprising (i) the same cellulose acetate butyrate as 
that employed in Example 1, (ii) toluene and (iii) methyl ethyl ketone, 
with the mixing ratio by weight thereof respectively being 9:18:18, were 
added. The mixture was dispersed for about 1 hour in a ball mill, so that 
an image transfer layer coating liquid was prepared. 
The thus prepared image transfer layer coating liquid was coated by a wire 
bar on the front side of a polyester film having a thickness of 6 .mu.m, 
backed with a silicone resin heat resistant layer, and was then dried at 
100.degree. C. for 1 minute, so that an image transfer layer having a 
thickness of about 5 .mu.m was formed on the polyester film, whereby a 
thermosensitive image transfer recording medium No. 5-1 according to the 
present invention was prepared. 
In this thermosensitive image transfer recording medium, the content of the 
oily material in the image transfer layer is 10 wt. %. 
Image Transfer Recording Medium No. 5-1 was super-imposed on a sheet of 
plain paper having a smoothness of 37 seconds (Xerox Bond Paper 4024) in 
such a manner that the image transfer layer came into close contact with 
the paper. A thermal head was then applied to the back side of the image 
transfer recording medium, with the applied thermal energy per dot varied 
to 0.5 mJ, 1.0 mJ, 1.5 mJ, 2.0 mJ and 2.5 mJ, so that the image densities 
of the respective images obtained were measured by a Macbeth densitometer. 
As a result, images with a cyan color having the image gradation as shown 
by Curve Ex. No. 5-1 in FIG. 2 were obtained. The total quality obtained 
was fairly good since the background was clear, but there was room for 
improvement with respect to the uniformity of image quality, which is 
indicated by a mark ".DELTA." in Table 1. 
Examples 5-2 to 5-6 
Example 5-1 was repeated except that the amount of lanolin acid oil 
employed in Example 5-1 was increased as shown in Table 1, whereby 
thermosensitive image transfer recording mediums No. 5-2 to No. 5-6 
according to the present invention were prepared. 
Thermal printing was performed on these thermosensitive image transfer 
recording mediums in the same manner as in Example 5-1. As a result, 
images with a cyanine color having the image gradations as shown by Curves 
Ex. No. 5-2 to No. 5-6 in FIG. 2 were obtained. 
In Table 1, in the uniformity of image quality, a mark "o" indicates that 
the uniformity of image quality was perfect, and a mark ".DELTA." 
indicates that the uniformity of image quality was fairly good, but there 
was still room for improvement thereof. In the background, a mark "o" 
indicates that the obtained background was clear, and a mark ".DELTA." 
indicates that the background was slightly unclear, but sufficiently 
suitable for use in practice. 
TABLE 1 
______________________________________ 
Examples 
5-1 5-2 5-3 5-4 5-5 5-6 
Oily Material (wt. %) 
Formulation 10% 15% 20% 30% 45% 55% 
______________________________________ 
Colorant 3 3 3 3 3 3 
(Neozapon Blue 807, 
made by BASF) 
Lanolin Fatty Acid 
2.15 3.4 4.8 8.3 15.8 23.7 
(Oily Material) 
(Neocoat OES-183, 
made by Yoshikawa 
Oil & Fat Co., Ltd.) 
Carnauba Wax 6 6 6 6 6 6 
(Carnauba Wax 
No. 1, made by 
Noda Wax Co., 
Ltd.) 
Dispersing Agent 
0.12 0.12 0.12 0.12 0.12 0.12 
Liquid Paraffin 
1.25 1.25 1.25 1.25 1.25 1.25 
Methyl ethyl ketone 
20 20 20 20 20 20 
Toluene 50 50 50 50 50 50 
Uniformity of 
.DELTA. .DELTA. 
o o o o 
Image Quality 
Background o o o o o .DELTA. 
______________________________________ 
The image qualities obtained in Example 5-1 to 5-6 were fairly good and 
sufficiently suitable for use in practice. The above results indicate that 
when the content of the oily material was in the range of about 20 wt. % 
to about 50 wt. % in the image transfer layer, particularly high quality 
images can be obtained. 
EXAMPLE 6-1 
A mixture of the following components was dispersed in a ball mill at about 
90.degree. C. for about 48 hours: 
______________________________________ 
Parts by Weight 
______________________________________ 
Neozapon Blue 807 (Colorant) 
10 
(made by BASF) 
Oleinic Acid Ester Oil 
6.6 
(Hisorate #117, Viscosity 80 cps/25.degree. C.) 
(Oily Material with low viscosity) 
Carnauba Wax (Carnauba Wax No. 1 
20 
made by Noda Wax Co., Ltd.) 
Lanolin Fatty Acid Oil 
6 
(Neocoat OES-183, made by Yoshikawa 
Oil & Fat Co., Ltd.) 
Sorbon T-80 (Non-ionic surfactant, 
0.5 
sorbitan monooleate, made by Toho 
Chemical Industry Co., Ltd.) 
(Dispersing Agent) 
Liquid paraffin 3 
Methyl ethyl ketone 60 
Toluene 150 
______________________________________ 
To the above dispersion, 300 parts by weight of a 20 wt. % cellulose 
acetate butyrate solution comprising (i) the same cellulose acetate 
butyrate as that employed in Example 1, (ii) toluene and (iii) methyl 
ethyl ketone, with the mixing ratio by weight thereof respectively being 
20:40:40, were added. The mixture was dispersed for about 1 hour in a ball 
mill, so that an image transfer layer coating liquid was prepared. 
The thus prepared image transfer layer coating liquid was coated by a wire 
bar on the front side of a polyester film having a thickness of 6 .mu.m, 
backed with a silicone resin heat resistant layer, and was then dried at 
100.degree. C. for 1 minute, so that an image transfer layer having a 
thickness of about 5 .mu.m was formed on the polyester film, whereby a 
thermosensitive image transfer recording medium No. 6-1 according to the 
present invention was prepared. 
In this thermosensitive image transfer recording medium, the content of the 
oily material in the image transfer layer is 10 wt. %. 
Image Transfer Recording Medium No. 6-1 was superimposed on a sheet of 
plain paper having a smoothness of 37 seconds (Xerox Bond Paper 4024) in 
such a manner that the image transfer layer came into close contact with 
the paper. A thermal head was then applied to the back side of the image 
transfer recording medium, with the applied thermal energy per dot varied 
to 0.5 mJ, 1.0 mJ, 1.5 mJ, and 2.0 mJ, so that the image densities of the 
respective images obtained were measured by a Macbeth densitometer. As a 
result, images with a cyan color having the image gradation as shown by 
Curve Ex. No. 6-1 in FIG. 3 were obtained. 
Examples 6-2 to 6-6 
Example 6-1 was repeated except that the amount of lanolin acid oil 
employed in Example 6-1 was increased as shown in Table 2, whereby 
thermosensitive image transfer recording mediums No. 6-2 to No. 6-6 
according to the present invention were prepared. 
Thermal printing was performed on these thermosensitive image transfer 
recording mediums in the same manner as in Example 6-1. As a result, 
images with a cyanine color having the image gradations as shown by Curves 
Ex. No. 6-2 to No. 6-6 in FIG. 3 were obtained. 
In Table 1, in the uniformity of image quality, a mark "o" indicates that 
the uniformity of image quality was perfect, and a mark ".DELTA." 
indicates that the uniformity of image quality was fairly good, but there 
was still room for improvement thereof. In the background, a mark "o" 
indicates that the obtained background was clear, and a mark ".DELTA." 
indicates that the background was slightly unclear, but sufficiently 
suitable for use in practice. 
TABLE 2 
______________________________________ 
Examples 
6-1 6-2 6-3 6-4 6-5 6-6 
Oily Material (wt. %) 
Formulation 10% 15% 20% 30% 50% 60% 
______________________________________ 
Colorant 10 10 10 10 10 10 
(Neozapon Blue 807, 
made by BASF) 
Oleinic Acid Ester 
6.6 10.5 14.9 25.5 59.5 89.3 
Oil 
(Hisorate #117, 
Viscosity 80 cps/ 
25.degree. C.) (Oily Material 
with low viscosity) 
Lanolin Fatty Acid 
6 6 6 6 6 6 
(Oily Material) 
(Neocoat OES-183, 
made by Yoshikawa 
Oil & Fat Co., Ltd.) 
Carnauba Wax 20 20 20 20 20 20 
(Carnauba Wax 
No. 1, made by 
Noda Wax Co., 
Ltd.) 
Dispersing Agent 
0.5 0.5 0.5 0.5 0.5 0.5 
Liquid Paraffin 
3 3 3 3 3 3 
Methyl ethyl ketone 
60 60 60 60 60 60 
Toluene 150 150 150 150 150 150 
Uniformity of 
.DELTA. .DELTA. 
o o o o 
Image Quality 
Background o o o o o .DELTA. 
______________________________________ 
The image qualities obtained in Example 6-1 to 6-6 were fairly good and 
sufficiently suitable for use in practice. The above results indicate that 
when the content of the oily material was in the range of about 20 wt. % 
about 50 wt. % in the image transfer layer, particularly high quality 
images can be obtained. 
EXAMPLE 7 
Example 6-1 was repeated except that the oleinic acid ester oil employed in 
Example 6-1 was replaced by a 25.5 parts by weight of stearic acid ester 
oil (Hisorate #111, viscosity 36.8 cps/25.degree. C.), whereby a 
thermosensitive image transfer recording mediums No. 7 according to the 
present invention was prepared. 
In this thermosensitive image transfer recording medium, the amount of the 
oily material with low viscosity corresponds to 30 parts by weight of the 
entire weight of the thermosenstivie image transfer layer. 
Thermal printing was performed on this thermosensitive image transfer 
recording medium in the same manner as in Example 6-1. The result was that 
the images obtained were as excellent as the images obtained in Example 
6-4. 
EXAMPLE 8 
Example 6-1 was repeated except that the oleinic acid ester oil employed in 
Example 6-1 was replaced by a 25.5 parts by weight of capric acid ester 
oil (Hisorate #101, viscosity 22.2 cps/25.degree. C.), and carnauba wax 
employed as thermofusible wax material in Example 6-1 was replaced by 
montan wax (made by Hoechst), whereby a thermosensitive image transfer 
recording mediums No. 8 according to the present invention was prepared. 
In this thermosensitive image transfer recording medium, the amount of the 
oily material with low viscosity corresponds to 30 parts by weight of the 
entire weight of the thermosenstivie image transfer layer. 
Thermal printing was performed on this thermosensitive image transfer 
recording medium in the same manner as in Example 6-1. The result was that 
the images obtained were as excellent as the images obtained in Example 
6-4. 
EXAMPLE 9 
Example 6-1 was repeated except that the oleinic acid ester oil employed in 
Example 6-1 was replaced by a 25.5 parts by weight of peanut oil 
(Viscosity 150 cps/25.degree. C.), whereby a thermosensitive image 
transfer recording mediums No. 9 according to the present invention was 
prepared. 
In this thermosensitive image transfer recording medium, the amount of the 
oily material with low viscosity corresponds to 30 parts by weight of the 
entire weight of the thermosenstivie image transfer layer. 
Thermal printing was performed on this thermosensitive image transfer 
recording medium in the same manner as in Example 6-1. The result was that 
the images obtained were as excellent as the images obtained in Example 
6-4.