Thermal transfer dye image-receiving sheet

A thermal transfer dye image-receiving sheet having a high resistance to curling and capable of smoothly travelling through a printer, and recording thereon dye images, includes a substrate sheet formed from a polyolefin resin and inorganic particles and a dye receiving resin layer formed on the substrate sheet, the substrate sheet having a longitudinal thermal shrinkage of 1.5% or less and a transversal thermal shrinkage of 0.5% upon heating from 20.degree. C. to 120.degree. C., and a longitudinal tensile elastic modulus of 50 MPa or less and a transversal tensile elastic modulus of 100 MPa or less at 120.degree. C.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a thermal transfer dye image-receiving 
sheet. More particularly, the present invention relates to a thermal 
transfer dye image-receiving sheet which exhibits a high resistance to 
curling during a printing procedure by a dye thermal transfer printer, can 
be smoothly fed into and delivered from the printer and can record clear 
dye images thereon. 
2. Description of the Related Art 
Currently there is an enormous interest in the development of new types of 
thermal transfer hard copiers, especially thermal transfer dye printers 
capable of printing clear full colored images or pictures. For example, 
thermal transfer dye printers can print full color images on a recording 
sheet by superposing a dye ink ribbon selected from yellow, magenta, cyan 
and optionally black dye ink ribbons on the recording sheet in such a 
manner that a dye-receiving layer of the recording sheet comes into 
contact with a dye ink layer of the dye ink ribbon at a location between a 
thermal head and a platen roll of the printer; and locally heating 
imagewise the dye ink ribbon by the thermal head while rotating around or 
reciprocating over the thermal head 3 or 4 times and while replacing the 
dye ink ribbons in the older of yellow, magenta, cyan and optionally 
black, so as to record full colored images on the recording sheet. 
To thermally transfer the dye images with a high quality to the recording 
sheet at a high speed by the dye thermal transfer printer, the recording 
sheet has a dye-receiving layer formed on a substrate sheet and 
comprising, as a principal component, a resin having a high dyeability 
with sublimating-dyes. 
The recording sheets may be supplied in the form of a roll or individual 
cut sheets. Usually, recording sheets for thermal transfer printers are 
supplied in the form of individual cut sheets. 
To smoothly feed, print and deliver the recording sheets in the form of 
individual cut sheets without difficulty, the coefficient of friction of 
the individual cut sheets to each other, the coefficient of friction 
between the cut sheets and the conveyer rolls for the sheets, and the 
thickness, stiffness, dimensional stability and curling property of the 
cut sheets should be carefully controlled. Among the above-mentioned 
properties, the curling phenomenon of the recording sheets greatly hinders 
the smooth feed and delivery of the recording sheets into and from the 
printer. If curling of the recording sheets significantly occurs, the 
recording sheets are caught by a pickup roll of a sheet feeder and rolls 
or guides arranged in the printer, so as to result in misfeeding and 
jamming of the recording sheets. Also, even when the recording sheets are 
quite flat, sometimes a misfeed occurs, because the recording sheets are 
conveyed through a plurality of rollers, and thus it is preferable that 
the recording sheets have an appropriate curl along the curved peripheries 
of the rollers. Especially, when the recording sheets have a high 
stiffness, the stiff recording sheets are difficult to bend along the 
peripheries of the conveying rollers, and thus sometimes jamming occurs. 
With respect to the recording sheet for the dye thermal transfer printer, 
it is known that a bi-axially oriented film comprising, as a principal 
component, a thermoplastic resin, for example, a polyolefin resin, is used 
as a substrate sheet. This type of recording sheet has a dye 
image-receiving layer formed on the substrate sheet and comprising, as a 
principal component, a dye-receiving thermoplastic resin. The recording 
sheet having the above-mentioned substrate sheet is advantageous in that 
the resultant recording sheet has a uniform thickness and exhibits a high 
softness and a lower thermal conductivity than that of a conventional 
paper sheet comprising cellulose fibers, and thus the resultant printed 
images on the recording sheet are uniform and a high color density. 
Nevertheless, the conventional recording sheet having a substrate sheet 
consisting of an oriented thermoplastic resin film is disadvantageous in 
that when dye images are thermally transferred by imagewisely heating by 
the thermal head, the recording sheet is thermally deformed and curled, 
and the curled recording sheet causes a faulty sheet delivery to occur in 
the printer. This disadvantage is derived from the shrinkage of the dye 
image-receiving layer itself, and a differential shrinkage between the dye 
image-receiving surface portion and the opposite surface portion of the 
recording sheet because the imagewise heating by the thermal head is 
applied to the dye image-receiving surface of the recording sheet. 
To solve the above-mentioned problems of the conventional recording sheet, 
it has been attempted to form the substrate sheet from a plurality of 
films different in thermal shrinkage from each other to prevent the 
curling of the recording sheet. Namely, the substrate sheet is formed from 
a plurality of oriented films including a film having a relatively low 
thermal shrinkage and located in the dye image-receiving surface side of 
the recording sheet to which the heating at a high temperature is applied, 
and another film having a relatively high thermal shrinkage and located in 
the opposite surface side of the recording sheet which is slightly heated 
by the thermal head. These films are laminated on and bonded to each other 
so as to balance the local thermal shrinkages and prevent the curling of 
the recording sheet. However, the lamination of a plurality of films 
different in thermal shrinkage from each other to provide a substrate 
sheet is too complicated and costly. 
Japanese Unexamined Patent publication (Kokai) No. 62-152,793 discloses a 
method for producing a thermal transfer image-receiving sheet having a 
dye-receiving layer formed on a synthetic paper substrate sheet, in which 
method the synthetic paper substrate sheet is heat treated at a 
temperature of from 60.degree. C. to 140.degree. C., preferably from 
110.degree. C. to 130.degree. C. for 2 to 3 seconds or more, to prevent 
the curling of the image-receiving sheet during printing. Namely, the 
synthetic paper substrate sheet is previously heat treated to-minimize the 
thermal shrinkage of the image-receiving sheet during printing. In this 
method, the substrate sheet is continuously brought into contact with a 
heating roll or passed through a heating oven, to release a residual 
stress in the substrate sheet by heating and to decrease the, thermal 
shrinkage of the substrate sheet. However, if the heat treatment 
temperature is not high enough, the residual stress-releasing effect is 
insufficient. Also, if the heat treatment temperature is too high, there 
is a risk of elongating the substrate sheet in the longitudinal direction 
and of increasing the longitudinal elongation and the residual stress of 
the substrate sheet. Therefore, this method is not always satisfactory in 
controlling the curling of the image-receiving sheet to a low level and in 
reproducibility. 
It is also known that to enhance the resistance to curling or wrinkling of 
the image-receiving sheet, a laminate sheet produced by bonding oriented 
films to both the front and back surfaces of a core sheet having a low 
thermal shrinkage or a high modulus of elasticity is used as a substrate 
sheet. However, since this type of substrate sheet is composed of a 
plurality of component layers different in thermal shrinkage, the 
resultant image-receiving sheet is sometimes curled due to a differential 
thermal shrinkage between the front surface portion and the back surface 
portion of the sheet. Namely, during the thermal transfer printing 
procedure, heating is applied only to the front surface of the 
image-receiving sheet, and thus a difference in temperature is provided 
between the front and back surfaces and thus the curling occurs due to the 
differential thermal shrinkage between the front and back surfaces. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a thermal transfer dye 
image-receiving sheet for a dye thermal transfer printer, capable of 
recording clear images of dye, for example, sublimating dye, and of 
smoothly-travelling through the printer, without curling, wrinkling, or 
delivery trouble of the printed sheet. 
The above-mentioned object can be attained by the thermal transfer dye 
image-receiving sheet of the present invention, which comprises: 
a substrate sheet consisting of an oriented thermoplastic film comprising, 
as principal components, a polyolefin resin and an inorganic pigment, and 
a dye-receiving resin layer formed on a surface of the substrate sheet and 
comprising a resin capable receiving a thermally transferable dye for 
forming dye images, 
the substrate sheet exhibiting thermal shrinkages of 1.50% or less in the 
longitudinal direction and 0.50% or less in the transverse direction of 
the substrate sheet when heated from a temperature of 20.degree. C. to a 
temperature of 120.degree. C., and having tensile moduli of elasticity of 
50.0 MPa or less in the longitudinal direction and 100.0 MPa or less in 
the transverse direction of the substrate sheet, determined at a 
temperature of 120.degree. C. 
In the thermal transfer dye image-receiving sheet of the present invention, 
preferably, the oriented thermoplastic film is provided with a 
multi-layered structure comprising a front surface layer on which the 
image-receiving resin layer is formed, a back surface layer and at least 
one core layer located between the front and back surface layers, 
satisfying the requirements (1) and (2): 
EQU Ds&lt;Db (1) 
EQU Ws&gt;Wb, (2) 
wherein Ds represents a density of the front surface layer, Db represents a 
density of the back surface layer, Ws represents a thickness of the front 
surface layer and Wb represents a thickness of the back surface layer, and 
has a total thickness of 50 to 300 .mu.m.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Generally, an image-receiving sheet usable for a dye thermal transfer 
printer comprises a substrate sheet, a dye-image-receiving layer formed on 
at least one surface of the substrate sheet and optionally an anti-static 
layer and/or a fuse adhesion-preventing layer. As a typical substrate 
sheet, a synthetic paper sheet, for example, an oriented thermoplastic 
film comprising, as principal components, a thermoplastic resin, for 
example, a polyolefine resin, and an inorganic pigment, and having a 
microporous structure. An oriented synthetic paper sheet having a 
microporous structure is practically used for printing, hand-writing and 
typing. Also, it is known that when an oriented synthetic paper sheet is 
used as a recording sheet for a thermal transfer printer, for example, a 
dye thermal transfer printer, transferred images which are clear and 
uniform can be formed on the sheet. However, in a thermal transfer 
printer, either in a sublimating dye-transferring system or a leuco 
dye-developing system, the image-receiving sheet is heated at one side 
surface thereof by a heating means such as a thermal head, and the heating 
at one side surface often causes the image-receiving sheet to curl. 
The inventors of the present invention have made a great effort to prevent 
the curling of the image-receiving sheet during the thermal transfer 
procedure, and discovered that by controlling the thermal shrinkage and 
tensile modulus of elasticity at high temperature of the substrate sheet 
to specific ranges, the differential stress created by a difference in 
heating between the front and back surfaces of the image-receiving sheet 
can be minimized, and thus the curling of the image-receiving sheet during 
the thermal transfer printing procedure can be restricted and problems in 
sheet delivery from the printer can be prevented. The present invention 
has been completed on the basis of the above-mentioned discovery. 
In the thermal transfer dye image-receiving sheet of the present invention, 
the specific substrate sheet which consists of an oriented thermoplastic 
film comprising, as principal components, a polyolefin resin and inorganic 
pigment, exhibits thermal shrinkages of 1.50% or less in the longitudinal 
direction and 0.5% or less in the transverse direction of the substrate 
sheet when heated from a temperature of 20.degree. C. to a temperature of 
120.degree. C., and has tensile moduli of elasticity of 50.0 MPa or less 
in the longitudinal direction and 100.0 MPa or less in the transverse 
direction of the substrate sheet determined at a temperature of 
120.degree. C. enabling the resultant image-receiving sheet to be free 
from trouble in feeding and delivery thereof. If the thermal shrinkages 
are more than 1.50% in the longitudinal direction and/or more than 0.50% 
in the transverse direction when heated from 20.degree. C. to 120.degree. 
C., and/or the tensile moduli of elasticity are more than 50.0 MPa in the 
longitudinal direction and/or more than 100.0 MPa in the transverse 
direction, during the thermal transfer printing procedure in which an 
imagewise heating by the thermal head is applied to the front surface of 
the image-receiving sheet, a differential stress created between the front 
and back surface portions of the sheet increases and thus the sheet is 
curled. 
The thermal shrinkages can be determined by the following method. 
On a surface of an image-receiving sheet, two straight lines intersecting 
each other in the form of a cross, extending in the longitudinal and 
transverse directions of the sheet and having a predetermined length of 
150 mm are marked at a temperature of 20.degree. C. The marked sheet was 
placed in an oven, heated to a temperature of 120.degree. C. for 10 
minutes, and cooled to a temperature of 20.degree. C. Thereafter, the 
lengths of the two lines are measured by using vernier calipers, and the 
thermal shrinkages are calculated from the differences between the 
original lengths and the measured lengths of the marked lines based on the 
original lengths. 
The tensile moduli of elasticity of the sheet are determined at a 
temperature of 120.degree. C. by using a tensile tester available under a 
trademark of TMA 8140C, from K.K. Rigaku, under a load of 5.0 g, at a 
frequency of 0.5 Hz and at a vibrational amplitude of 1 g. 
The substrate sheet for the image-receiving sheet of the present invention 
consists of an oriented thermoplastic film comprising, as principal 
components, a polyolefin resin and an inorganic pigment. 
The polyolefin resin is preferably selected from homopolymers and 
copolymers of ethylene, propylene and butene-1, ethylene-vinyl acetate 
copolymers, and poly(4-methylpentene-1). Among the above-mentioned 
polymers, the polypropylene resins are more preferable for the present 
invention, because the polypropylene resins have a high heat resistance, a 
high resistance to solvents and a low price. 
The substrate sheet optionally comprises, in addition to the polyolefin 
resin, an additional resin different from the polyolefin resin, compatible 
with the polyolefin resin, and comprising at least one member selected 
from the group consisting of polystyrene, polyamide, polyethylene 
terephthalate, hydrolysis products of ethylene-vinyl acetate copolymers, 
ethylene-acrylic acid copolymers and salts thereof and vinylidene chloride 
copolymers, for example, vinyl chloride-vinylidene chloride copolymers. 
The inorganic pigment, which is in the form of fine particles, preferably 
comprises at least one member selected from calcium carbonate, calcined 
clay, diatomaceous earth, talc, titanium dioxide, barium sulfate, aluminum 
sulfate and silica. 
The content of the inorganic pigment in the substrate sheet (the oriented 
thermoplastic film) is usually 3 to 80% by weight. 
The oriented thermoplastic film usable for the substrate sheet of the 
present invention can be produced by mixing the polyolefin resin, the 
inorganic pigment and optionally the additional polymeric substance which 
will be referred to as additional resin hereinafter, melt-extruding 
through a film-forming slit of an extruder and drawing monoaxially or 
bi-axially the extruded film to an extent that the resultant oriented 
thermoplastic film exhibits the specific thermal shrinkages and tensile 
moduli of elasticity in the longitudinal and transverse directions. 
The additional resins effectively serve to adjust the thermal shrinkages 
and the tensile moduli of elasticity to the desired ranges. The reasons 
for the specific effect of the additional resins is assumed to be as 
follows. 
Where the oriented thermoplastic film having a resinous matrix consisting 
of a polyolefin resin alone is heated imagewise by a thermal head, the 
polyolefin resin is melted and then solidified by cooling. Since the 
polyolefin resin has a high crystallization tendency, the solidified 
polyolefin resin has an increased degree of crystallization. The increase 
in the degree of crystallization causes the thermal shrinkages of the film 
resin is restricted by the presence of the additional to increase. 
When the polyolefin resin is mixed with the additional resin, the 
crystallization of the polyolefin resin, and thus the thermal shrinkages 
of the resultant oriented thermoplastic film is reduced. 
Also, it is possible to apply a known heat treatment to the oriented 
thermoplastic film to decrease the thermal thrinkages thereof and to 
prevent the curling of the resultant image-receiving sheet unless the heat 
treatment affects the effect of the present invention. 
The additional resin compatible with the polyolefin resin may be selected 
as follows. 
Where the polyolefin resin is a polypropylene resin, the additional resin 
is preferably selected from polyethylene resins, ethylene-propylene 
copolymer resins, ethylene-vinyl acetate copolymer resins, polyvinyl 
chloride resins, polystyrene resins, 
acrylonitrile-butadiene-styrene-terpolymer (ABS) resins, polyvinyl 
alcohol, polyacrylic ester resins, acrylonitrile-styrene copolymer resins, 
polyvinylidene resins acrylonitrile-styrene-acrylic ester-terpolymer (ASA 
or AAS) resins, acrylonitrile-ethylene-styrene terpolymer (AES) resins, 
cellulose derivative resins, polyurethane resins, polyvinyl butyral 
resins, poly-4-methylpentene-1, polybutene, polyester resins, epoxy 
resins, phenolic resins, urea resins, melamine resins, diallyl-phthalate 
resins, silicone resins, fluorine-containing polymer resins, polycarbonate 
resins polyamideacetal resins, polyphenyleneoxide resins, polybutylene 
terephthalate, polyethylene terephthalate resins, polyphenylenesulfide 
resins, polyimide resins, polystyrene resins, polyethersulfone resins, 
aromatic polyester resins, and polyallylate resins. These additional 
resins may be employed alone or in a mixture of two or more thereof. The 
additional resins are employed in an amount of 0.5 to 50% based on the 
weight of the polypropylene resin. The crystallization of the 
polypropylene resin can be restricted by blending an atactic polypropylene 
with an isotactic polypropylene which is different in steric regularity 
from the atactic polypropylene, to reduce the thermal shrinkages of the 
resultant substrate sheet. 
Also, the addition of the additional resin effectively enables control of 
the density of the resultant substrate sheet. 
The substrate sheet usable for the present invention preferably has a 
thickness of 80 to 300 .mu.m, more preferably 120 to 250 .mu.m. If the 
thickness is less than 80 .mu.m, the resultant substrate sheet exhibits an 
unsatisfactory mechanical strength, and the resultant image-receiving 
sheet exhibits an unsatisfactory stiffness and resilience to deformation, 
and thus may not fully prevent the curling thereof during the thermal 
transfer printing procedure. Also, if the thickness is more than 300 
.mu.m, the resultant image-receiving sheet has too a large thickness. 
Namely, in the printer, the volume of sheet-containing space is limited 
and thus the larger the thickness of the individual image-receiving 
sheets, the smaller the number of the sheets capable of being contained in 
the sheet-containing space, or the larger the volume of the 
sheet-containing space necessary to contain a desired number of the 
sheets. The large sheet-containing space results in difficulty in making 
the thermal transfer printer compact. 
The substrate sheet for the present invention may have a single layered 
structure, or a may consist of a composite film having a multi-layered 
structure and made by forming a plurality of films comprising the 
polyolefin resin and the inorganic pigment, laminate-bonding the films 
into a composite film and drawing the composite film in at least one 
direction. For example, the multi-layered composite film has a three 
layered structure comprising a front surface layer, a core layer and a 
back surface layer, or a four or more-layered structure. In the 
multi-layered structures, the component layers are different in thermal 
shrinkage and strain from each other and thus the strains created in the 
component layers during the thermal transfer printing procedure cancel 
each other and thus the resultant multi-layered substrate sheet enables 
the image-receiving sheet to exhibit an enhanced resistance to curling. 
Also, in the multi-layered structure having the front surface layer, at 
least one core layer and the back surface layer, when at least the core 
layer comprises the blend of the polyolefin resin and the additional resin 
compatible with the polyolefin resin, the resultant substrate sheet can 
exhibit well-balanced thermal shrinkages and tensile moduli of elasticity. 
In the image-receiving sheet of the present invention, the dye-receiving 
resin layer formed on a surface of the substrate sheet comprises, as a 
principal component, a resin capable of receiving a dye thermally 
transferred from a dye ink ribbon. The dye-receiving resin comprises at 
least one member selected from thermoplastic saturated polyester resins, 
vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-vinyl 
propionate polymer resins, polycarbonate resins, polyvinyl acetal resins, 
polyacrylic acid ester resins, cellulose derivatives, actinic 
radiation-cured resins, and other dyeable synthetic resins. 
The dye-receiving resin layer preferably has a thickness of 1 to 12 .mu.m, 
more preferably 2 to 7 .mu.m. If the thickness is less than 1 .mu.m, the 
resultant dye-receiving resin layer exhibits an unsatisfactory 
dye-receiving sensitivity and gloss, and the resultant dye images exhibit 
a low color density. Also, if the thickness is more than 12 .mu.m, not 
only, the dye-receiving capacity is saturated, thus causing an economical 
disadvantage, but also, the resultant dye images have a reduced color 
density. 
In the dye-receiving resin layer of the image-receiving sheet of the 
present invention, an additive, for example, cross-linking agent for the 
dye-receiving resin, lubricating agent, and releasing agent for the 
purpose of preventing an undesired adhesion of the dye ink ribbon with the 
image-receiving sheet due to the heating by the thermal head during the 
thermal transfer printing procedure, is optionally contained. Also, if 
necessary, a further additive, for example, antioxidant, white pigment, 
coloring material, brightening agent, ultraviolet ray-absorber and 
sensitizing agent, may be added to the dye-receiving layer. 
The further additive may comprise, for example, substituted phenol 
compounds or terpene, which are low molecular weight compounds. The white 
pigment, coloring material (blue or violet coloring pigment and dye) and 
brightening agent (fluorescent brightener) can be employed to enhance the 
whiteness and opaqueness of the dye-receiving resin layer, to adjust the 
color of the dye-receiving resin layer to a desired color and to control 
the brightness of the dye-receiving resin layer to a desired level. The 
additive or further additive, for example, the white pigment, ultraviolet 
ray-absorber and cross-linking agent, may be contained in the 
dye-receiving resin layer by mixing these agents with the dye-receiving 
resin, and coating the mixture on the front surface of the substrate 
sheet. Alternatively, the additive or further additive may be coated, as 
uppercoat or undercoat, on or under the dye-receiving resin layer. 
The pigment included in the dye-receiving layer comprises preferably 
silica, more preferably specific silica having an average particle size of 
1 to 12 .mu.m and a specific surface area of 30 to 250 m.sup.2 /g. The 
pigment is contained preferably in an amount of 5 to 20%, by weight based 
on the weight of the dye-receiving resin. If the average size of the 
silica particles is too large, so that portions of the silica particles 
project from the front surface of the dye-receiving resin layer, the 
projected portions cannot be colored with dye and thus non-dye-transferred 
defective portions are formed in the thermally transferred images. 
Therefore, the pigment particles preferably have a size smaller than the 
thickness of the dye-receiving resin layer. When silica is added to the 
dye-receiving resin layer formed on the substrate sheet, the silica 
effectively prevents undesired adhesion of the dye ink ribbon with the 
image-receiving sheet, adequately controls a friction between the dye ink 
ribbon and the image-receiving sheet, and prevents wrinkles formed on the 
dye ink ribbon from being transferred to the dye-receiving resin layer and 
the transferred images from becoming defective. Also, the silica 
effectively improves the conveyance of the image-receiving sheets through 
the printer, and enhances the clearness of the resultant dye images on the 
dye-receiving layer. 
Further, to enhance the resistance of the dye-receiving layer to 
fuse-adhesion with the dye ink ribbon during the thermal transfer printing 
procedure, the dye-receiving layer preferably contains a release agent. 
The release agent is preferably selected from waxes, for example, paraffin 
and polyethylene wax, metal soaps, silicone oils, silicone resins, 
fluorine-containing surfactants and fluorine-containing resins. Usually, 
the release agent is added in an amount of 15% by weight or less to the 
dye-receiving resin layer. 
Furthermore, an intermediate layer is optionally arranged between the 
substrate sheet, for example, the oriented thermoplastic resin substrate 
sheet, and the dye-receiving resin layer to enhance the adhesion 
therebetween. The intermediate layer may comprise a hydrophilic or 
hydrophobic binder resin. Namely, the binder resin for the intermediate 
layer is selected from, for example, vinyl polymers, for example, 
polyvinyl alcohol and polyvinyl pyrrolidone, vinyl polymer derivatives, 
polyacrylic polymers, for example, polyacrylamide, polydimethylacrylamide, 
polyacrylic acid and salts thereof and polyacrylic acid esters, 
polymethacrylic polymers, for example, polymethacrylic acid and 
polymethacrylic acid esters, and natural polymers and derivatives thereof, 
for example, starch, sodium alginate, gum arabic, casein and 
carboxy-methyl cellulose. 
Still furthermore, to prevent the generation of static electricity on the 
image-receiving sheets and to enable the sheets to smoothly travel through 
the printer, an antistatic agent is contained in at least one of the 
component layers of the image-receiving sheet or coated on the front 
surface of the dye-receiving resin layer or the back surface of the 
substrate sheet. The antistatic agent preferably contains a cationic 
hydrophilic polymer, for example, quaternary ammonium group-containing 
polymers, polyamine derivatives, polyethylene imine, cationic 
monomer-acrylic monomer copolymers, cation-modified acrylic amides, and 
cation-modified starch. 
The dye-receiving resin layer or another additional layer may be formed by 
coating a coating liquid or paste by using a coater, for example, a bar 
coater, gravure coater, comma coater, or air knife coater, and drying the 
coated layer, in conventional manner. 
In an embodiment of the dye image-receiving sheet of the present invention, 
the oriented thermoplastic film for the substrate sheet is provided with a 
multi-layered structure comprising a front surface layer on which the 
dye-receiving resin layer is formed, a back surface layer and at least one 
core layer located between the front and back surface layers; and 
satisfying the requirements (1) and (2): 
EQU Ds&lt;Db (1) 
EQU Ws&gt;Wb, (2) 
wherein Ds represents a density of the front surface layer, Db represents a 
density of the back surface layer, Ws represents a thickness of the front 
surface layer and Wb represents a thickness of the back surface layer. 
Also, the oriented thermoplastic film has a total thickness of 50 to 300 
.mu.m. 
In the embodiment of the dye image-receiving sheet of the present 
invention, the oriented thermoplastic film for the substrate sheet has a 
three or more-layered structure. 
For example, referring to FIG. 1, a thermal transfer dye image-receiving 
sheet 1 comprises a substrate sheet 2 and a dye-receiving resin layer 3 
formed on a front surface of the substrate sheet 2. 
The substrate sheet 2 consists of a three-layered composite film composed 
of a front surface layer 4 on which the dye-receiving resin layer 3 is 
arranged, a back surface layer 5 and a core layer 6 arranged between the 
front and back surface layers 4 and 5. Each of the front surface, core and 
back surface layers 4, 6 and 5 consists of a single layered film layer. Of 
course, the substrate sheet of the present invention may consist of a four 
or more-layered composite film. 
The multi-layered substrate sheet usable for the present invention has a 
thickness of 50 to 300 .mu.m, more preferably 120 to 250 .mu.m. If the 
thickness is less than 50 .mu.m, the resultant substrate sheet may exhibit 
an unsatisfactory mechanical strength and thus have a high risk of 
problems in the conveyance of the image-receiving sheets through the 
printer. Also, if the thickness is more than 300 .mu.m; the resultant 
image receiving sheets may have too a large thickness, thus the number of 
the image-receiving sheets capable of being contained in the 
sheet-containing space of the printer may become too small, and it may 
become difficult to provide a compact printer. 
In the multi-layered substrate sheet, the thickness Ws of the front surface 
layer and the thickness Wb of the back surface layer satisfies the 
relationship (2): 
EQU Ws&gt;Wb. (2) 
The thicknesses Ws and Wb of the front and back surface layers are not 
limited to specific ranges. Nevertheless, the front surface layer 
thickness Ws is preferably 20 to 120 .mu.m, and the back surface layer 
thickness Wb is 15 to 100 .mu.m. If Ws is not more than Wb, the resultant 
substrate sheet may not fully prevent the curling of the image-receiving 
sheet during the thermal transfer printing procedure. If the thickness Ws 
of the front surface layer is less than 20 .mu.m, the front surface of the 
resultant substrate sheet may be uneven and clearness of the dye images 
received thereon may be unsatisfactory. If the thickness Ws of the front 
surface layer is more than 120 .mu.m, the resultant substrate sheet may be 
too stiff. The thickness of the core layer is preferably 15 to 80 .mu.m. 
In the multi-layered substrate sheet, when the density Ds of the front 
surface layer and the density Db of the front surface layer meet with the 
requirement (1): 
EQU Ds&lt;Db, (1) 
it is found that the resultant image-receiving sheet exhibits a high 
resistance to curling in the thermal transfer printing procedure, and the 
dye images printed thereon are very clear. Preferably, a ratio Ds/Db is in 
the range of from 0.3 to 0.95, more preferably 0.6 to 0.9. In the present 
invention, there are specific limitations to the densities Ds and Db. 
Nevertheless, the front surface layer density (Ds) is preferably 0.5 to 
1.2 g/cm.sup.3, more preferably 0.7 to 1.2 g/cm.sup.3, and the back 
surface layer density (Db) is preferably 0.8 to 1.5 g/cm.sup.3, more 
preferably 0.8 to 1.3 g/cm.sup.3. The densities of the front and back 
surface layers can be determined by preparing single-layered films 
corresponding to the front and back surface layers under the same 
film-forming conditions as those of the multi-layered film-forming 
conditions, measuring areas and weights of the films and calculating the 
densities from the measured areas and weights. 
If Ds is not less than Db, the thermal shrinkage of the front surface layer 
may be higher than that of the back surface layer, and thus the resultant 
image-receiving sheets may be curled during the thermal transfer printing 
procedure. 
In polyolefin resin films having the same composition as each other, an 
increase in the drawing ratio results in an increase in the degree of 
crystallization, in an increase in the density and thus in an increase in 
the thermal shrinkage of the drawn films. Accordingly, in the preparation 
of the multi-layered film, the densities of the front and back surface 
layers can be controlled by melt-laminating the front and back surface 
layers on both the front and back surfaces of a core layer while 
controlling the thicknesses of the front and back surface layers and 
optionally controlling the draw ratios of the front and back surface 
layers, cooling the resultant laminated composite film, re-heating the 
cooled composite film, and drawing the re-heated composite film in a 
direction at a right angle to the direction of monoaxial drawing applied 
to the core layer at a desired draw ratio. 
The reasons why the curling of the resultant image-receiving sheet during 
the thermal transfer printing procedure can be restricted by adjusting the 
densities Ds and Db of the front and back surface layers so as to meet the 
requirement (1): Ds&lt;Db, is not yet completely clear. However, it is 
assumed that in the thermal transfer printing procedure, the 
image-receiving sheet is interposed, pressed and heated between a thermal 
head and a platen roller. In this printing procedure, the oriented film 
thermally shrinks due to a residual stress. Also, since the heating is 
applied asymmetrically to the front and back surfaces of the 
image-receiving sheet, a differential stress is created between the front 
and back surface layers of the multi-layered substrate sheet. The 
differential stress causes the image-receiving sheet to curl during the 
thermal transfer printing procedure. 
In the present invention, the front surface layer of the substrate sheet, 
on which the dye-receiving resin layer is formed, has a lower thermal 
shrinkage than that of the back surface layer, so that the curling of the 
image-receiving sheet during the thermal transfer printing procedure can 
be effectively restricted. 
In an embodiment of the present invention, the oriented-thermoplastic film 
for the substrate sheet is, for example, a multi-layered, oriented 
thermoplastic resin film comprising a front surface layer comprising a 
polyolefin resin film containing 0 to 25% by weight of fine inorganic 
particles, a core layer comprising a polyolefin resin film containing fine 
inorganic particles in an amount more than that in the front surface layer 
and having a number of microvoids formed by drawing, and a back surface 
layer comprising a monoaxially oriented polyolefin resin film containing 
10 to 75% by weight of fine inorganic particles. 
The polyolefin resin for the front and back surface and core layers is 
preferably selected from polyethylene resins, polypropylene resins, 
ethylene-propylene copolymer resins, ethylene-vinyl acetate copolymer 
resins and poly(4-methylpentene-1) resins, more preferably polypropylene 
resins which have a high heat resistance, a high resistance to solvents 
and a low price. As mentioned above, the polyolefin resin is optionally 
blended with an additional resin, for example, polystyrene, polyamide, 
polyethylene terephthalate, partial hydrolysis product of ethylene-vinyl 
acetate copolymer, ethylene-acrylic acid copolymer and salt thereof or 
vinylidene chloride copolymer, for example, vinylidene chloride-vinyl 
chloride copolymer. Also, the inorganic particles may be selected from 
fine calcium carbonate, calcined clay, diatomaceous earth, talc, titanium 
dioxide, barium sulfate, aluminum sulfate and silica particles. 
In the thermal transfer dye image-receiving sheet of the present invention, 
the oriented thermoplastic film for the substrate sheet can be produced by 
coating a polyolefin resin melt on a surface of a core polyolefin resin 
film drawn in one direction and further coating a polyolefin resin melt on 
the opposite surface of the core polyolefin resin film, by a 
melt-laminating method; cooling the resultant three-layered film to room 
temperature; heating the cooled film at a temperature of 100.degree. to 
180.degree. C.; drawing the heated film in a direction at a right angle to 
the drawing direction of the core polyolefin resin film; and heat treating 
the drawn film at a temperature of 50.degree. to 120.degree. C. 
As mentioned above, the multi-layered, oriented polyolefin resin film for 
the substrate sheet comprises at least the front surface layer, core layer 
and back surface layer. 
In another embodiment of a process for producing the multi-layered, 
oriented polyolefin resin film, a polyolefin resin layer is melt-laminated 
on a front surface of a monoaxially oriented polyolefin resin film for the 
core layer to form a front surface layer; another polyolefin resin layer 
containing 10 to 75% by weight of fine inorganic particles is 
melt-laminated on the back surface of the core layer to form a back 
surface layer; the resultant laminate sheet is cooled; the cooled sheet is 
re-heated and drawn in a direction at a right angle to the monoaxial 
drawing direction of the core layer; and then the drawn sheet is 
heat-treated. 
In the above-mentioned process, the core layer is biaxially drawn and a 
great number of microvoids are formed in the core layer. The front and 
back surface layers comprise monoaxially oriented films having finely 
roughened surfaces. The finely roughened surfaces preferably have a Bekk 
smoothness of 500 to 15,000 seconds. 
To obtain an image-receiving sheet having a high resistance to curling, it 
is important that the thermal shrinkages of the front and back surface 
layers be well balanced with each other. It possible that a resin 
component consisting of a polyolefin resin alone is used to form the back 
surface layer and a resin blend of the polyolefin resin with an additional 
resin is used to form the front surface layer. For example, a 
polypropylene resin is used to form the back surface layer, and a resin 
blend comprising a polypropylene resin, an ethylene-propylene copolymer 
resin and an ethylene-propylene-diene copolymer rubber is employed to form 
the front surface layer. The blended additional resin effectively 
restricts the recrystallization of the polyolefin resin in the front 
surface layer so as to control the thermal shrinkage of the front surface 
layer so that it properly balances the thermal shrinkage of the back 
surface layer. 
EXAMPLES 
The present invention will be further illustrated with reference to the 
following examples which are merely representative and do not restrict the 
scope of the present invention in any way. 
In the examples, the resultant thermal transfer dye image-receiving sheets 
were subjected to the following tests. 
(1) Travelling performance through a printer 
The image-receiving sheets were heated at a temperature of 50.degree. C. 
for 48 hours and cut into A4 size. 
The cut sheets were subjected in the number of 20 sheets to a continuous 
thermal transfer printing using a sublimating dye printer available under 
the trademark of Video Printer JX 7000, from Sharp K.K. The travelling 
performance of the image-receiving sheets was evaluated and categorized in 
the following classes. 
______________________________________ 
Class Evaluation 
______________________________________ 
2 No trouble occurred 
1 Trouble occurred 
______________________________________ 
(2) Resistance to curling 
After the above-mentioned continuous printing procedure, the last 
(twentieth) printed sheet was placed on a horizontal plane so that the 
printed surface faced upward and the corners of the sheet were allowed to 
raise from the horizontal plane. The heights of the corner ends from the 
horizontal plane were measured. When the sheet curled into a cylinder 
form, the diameter of the cylinder was measured. 
When the measured curling value was less than 11 mm, the sheets were 
evaluated as very good in travelling performance through the printer and 
appearance thereof. 
When the measured curling value was 11 mm or more but less than 26 mm, the 
sheets were evaluated as useful without difficulty for the thermal 
transfer printing. When the measured curling value was 26 mm or more, or 
the sheet was curled into a cylinder, the sheets were evaluated as 
practically useless, because the curled sheets are difficult to smoothly 
travel through and deliver from the printer. 
(3) Clearness of the received dye images 
The dye images received on the dye-receiving layer were observed by naked 
eye to evaluate the quality of the dye images and categorized in the 
following classes. 
______________________________________ 
Class Evaluation 
______________________________________ 
3 Very clear and sharp 
2 Usable for practical use 
1 Unclear and useless for practical use 
______________________________________ 
Example 1 
A mixture of 50 parts by weight of a polypropylene resin with 20 parts by 
weight of a polyethylene resin and 30 parts by weight of fine calcium 
carbonate particles having an average particle size of 1.5 .mu.m was 
mix-kneaded in an extruder at a temperature of 27.degree. C. and then 
melt-extended into a film form, and the extended film was cooled to form 
an undrawn sheet. The undrawn sheet was heated to a temperature of 
140.degree. C., drawn at a draw ratio of 5.0 in the longitudinal direction 
and at a draw ratio of 3.0 in the transverse direction, to provide an 
oriented sheet having a thickness of 180 .mu.m. The oriented sheet was 
heat-treated at a temperature of 90.degree. C. for 24 hours to control the 
thermal shrinkage of the sheet to a desired level. 
The resultant oriented sheet exhibited a longitudinal thermal shrinkage of 
1.00%, and a transverse thermal shrinkage of 0.06% when the heating 
temperature was raised from 20.degree. C. to 120.degree. C., and a 
longitudinal tensile modulus of elasticity of 17.2 MPa and a transverse 
tensile modulus of elasticity of 55.8 MPa at a temperature of 120.degree. 
C. 
The oriented sheet was employed as a substrate sheet. 
A coating liquid (1) having the composition shown below was coated on a 
front surface of the substrate sheet and dried to form a dye-receiving 
resin layer having a dry thickness of 5 m. 
______________________________________ 
Coating liquid (1) 
Compound Part by weight 
______________________________________ 
Saturated polyester resin (*)1 
100 
Silicone oil (*)2 25 
Polyisocyanate compound (*)3 
5 
Silica (*)4 15 
______________________________________ 
Note 
(*)1 . . . Trademark: Vylon 200, made by Toyobo K. K. 
(*)2 . . . Trademark: SH 3740 (release agent), made by Toray DowCorning 
Silicone K. K. 
(*)3 . . . Trademark: Coronate L (Crosslinking agent), made by Nihon 
Polyurethane Kogyo K. K. 
(*)4 . . . Trademark: C212, made by Mizusawa Kagaku Kogyo K. K. 
Average particle size: 2.2 .mu.m 
Specific surface area: 170 m.sup.2 /g 
The mixture was dissolved and dispersed in a solvent consisting of toluene 
and methylethylketone in a mixing ratio of 5/1 to form a 15% coating 
liquid. The thermal shrinkages and the tensile moduli of elasticity were 
determined by the above-mentioned measurement methods. 
The test results are shown in Table 1. 
Example 2 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 1, with the following exceptions. 
The substrate sheet was produced by melt-kneading a mixture of 50 parts by 
weight of a polypropylene with 30 parts by weight of an ethylene-propylene 
copolymer resin and 20 parts by weight of calcium carbonate particles 
having an average size of 1.5 .mu.m in a melt-extruder at a temperature of 
270.degree. C.; the melt-kneaded resin mixture was extruded in a sheet 
form from the extruder; the extruded sheet was cooled by a cooling device 
to provide an undrawn sheet. The undrawn sheet was then heated to a 
temperature of 140.degree. C., and biaxially drawn at a longitudinal draw 
ratio of 5.0 and at a transverse draw ratio of 7.0, to provide an oriented 
sheet having a thickness of 185 .mu.m. 
The resultant oriented substrate sheet exhibited a longitudinal thermal 
shrinkage of 1.24% and a transverse thermal shrinkage of 0.33% when heated 
from 20.degree. C. to 120.degree. C., and a longitudinal tensile modulus 
of elasticity of 27.5 MPa and a transverse tensile modulus of elasticity 
of 48.1 MPa at a temperature of 120.degree. C. 
The test results are shown in Table 1. 
Example 3 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 2, with the following exceptions. 
In the preparation of the substrate sheet, the resin mixture consisted of 
70 parts by weight of the polypropylene resin, 10 parts by weight of the 
polyethylene, and 20 parts by weight of the calcium carbonate particles 
having the average size of 1.5 .mu.m. 
The resultant oriented substrate sheet having the thickness of 185 .mu.m 
had a longitudinal thermal shrinkage of 1.45%, and a transverse thermal 
shrinkage of 0.46% when heated from 20.degree. C. to 120.degree. C., and a 
longitudinal tensile modulus of elasticity of 45.5 MPa and a transverse 
tensile modulus of elasticity of 98.8 MPa at a temperature of 120.degree. 
C. 
The test results are shown in Table 1. 
Example 4 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 1, with the following exceptions. 
1 Preparation of undrawn sheets (A) for front and back surface layers 
A mixture of 70 parts by weight of a polypropylene resin with 10 parts by 
weight of a polyethylene resin and 20 parts by weight of calcium carbonate 
particles having an average size of 1.5 .mu.m was melt-kneaded in a melt 
extruder at a temperature of 270.degree. C., extruded in the form of a 
sheet from the extruder and cooled by a cooling device to provide two 
undrawn sheets (A) for the front and back surface layers. 
2 Preparation of oriented sheet (B) for core layer 
A mixture of 55 parts by weight of a polypropylene resin with 10 parts by 
weight of a polyethylene resin, 10 parts by weight of an 
ethylene-propylene copolymer resins and 25 parts by weight of calcium 
carbide particles having an average size of 1.5 .mu.m was melt-kneated in 
a melt-extruder at a temperature of 270.degree. C.; the melt was extruded 
into the form of a sheet from the extruder and then cooled by a cooling 
device to provide an undrawn sheet. This undrawn sheet was heated to a 
temperature of 140.degree. C. and at this temperature, the sheet was drawn 
at a draw ratio of 5.0 in the longitudinal direction of the sheet to 
provide an oriented sheet (B) for the core layer. 
3 Preparation of a three layered laminate sheet 
The two undrawn sheets (A) were laminated on the front and back surfaces of 
the oriented sheet (B) and the laminate was drawn at a draw ratio of 6.0 
in the transverse direction of the core layer sheet (B) at a temperature 
of 170.degree. C. 
The resultant three layered sheet had a total thickness of 170 .mu.m and 
was composed of a front surface layer having a thickness of 60 .mu.m, a 
core layer having a thickness of 50 .mu.m and a back surface layer having 
a thickness of 60 .mu.m. 
Also, the three layered sheet exhibited a longitudinal thermal shrinkage of 
0.94% and a transverse thermal shrinkage of 0.08% upon heating from 
20.degree. C. to 120.degree. C., and a longitudinal tensile modulus of 
elasticity of 9.5 MPa and a transverse tensile modulus of elasticity of 
70.6 MP at a temperature of 120.degree. C. 
The three-layered sheet was employed as a substrate sheet. 
The test results are shown in Table 1. 
Comparative Example 1 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 1, with the following exceptions. 
The substrate sheet consisted of a biaxially oriented thermoplastic resin 
sheet having a thickness of 110 .mu.m and produced in such a manner that a 
mixture of 70 parts by weight of a polypropylene resin with 30 parts by 
weight of calcium carbonate particles having an average size of 1.5 .mu.m 
was melt-kneaded in a melt-extruder at a temperature of 270.degree. C.; 
the melt was extruded into a sheet form and cooled by a cooling device to 
provide an undrawn sheet; the undrawn sheet was heated to a temperature of 
140.degree. C. and biaxially drawn at a draw ratio of 5.0 in the 
longitudinal direction and at a draw ratio of 5.0 in the transverse 
direction, to provide an oriented substrate sheet. 
The resultant substrate sheet exhibited a longitudinal thermal shrinkage of 
2.2% and a transverse thermal shrinkage of 0.76% upon heating from 
20.degree. C. to 120.degree. C. and a longitudinal tensile modulus of 
elasticity of 26.7 MPa and a transverse tensile modulus of elasticity of 
108.0 MPa at a temperature of 120.degree. C. 
The test results are shown in Table 1. 
Comparative Example 2 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 1, with the following exceptions. 
The substrate sheet consisted of a biaxially oriented thermoplastic resin 
sheet having a thickness of 150 .mu.m and produced in such a manner that a 
mixture of 80 parts by weight of a polypropylene resin with 20 parts by 
weight of calcium carbonate particles having an average size of 1.5 .mu.m 
was melt-kneaded in a melt-extruder at a temperature of 270.degree. C.; 
the melt was extruded into a sheet form and cooled by a cooling device to 
provide an undrawn sheet; the undrawn sheet was heated to a temperature of 
140.degree. C. and biaxially drawn at a draw ratio of 5.0 in the 
longitudinal direction and at a draw ratio of 7.0 in the transverse 
direction, to provide an oriented substrate sheet. 
The resultant substrate sheet exhibited a longitudinal thermal shrinkage of 
2.66% and a transverse thermal shrinkage of 1.02% upon heating from 
20.degree. C. to 120.degree. C., and a longitudinal tensile modulus of 
elasticity of 57.1 MPa and a transverse tensile modulus of elasticity of 
87.4 MPa at a temperature of 120.degree. C. 
The test results are shown in Table 1. 
Comparative Example 3 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 1, with the following exceptions. 
The substrate sheet consisted of a biaxially oriented thermoplastic resin 
sheet having a thickness of 190 .mu.m and produced from a mixture of 60 
parts by weight of a polypropylene resin with 40 parts by weight of 
calcium carbonate particles having an average size of 1.5 .mu.m by the 
same procedures as in Example 1. 
The resultant substrate sheet exhibited a longitudinal thermal shrinkage of 
1.48% and a transverse thermal shrinkage of 0.40% upon heating from 
20.degree. C. to 120.degree. C., and a longitudinal tensile modulus of 
elasticity of 63.7 MPa and a transverse tensile modulus of elasticity of 
121.0 MPa at a temperature of 120.degree. C. 
The test results are shown in Table 
TABLE 1 
__________________________________________________________________________ 
Thermal shrinkage (%) 
Tensile modulus of elasticity (MPa) 
Curling 
Travelling property 
Clearness of 
Example No. 
Longitudinal 
Transverse 
Longitudinal 
Transverse 
(mm) in printer 
dye images 
__________________________________________________________________________ 
Example 
1 1.00 0.06 17.1 55.8 14 2 3 
2 1.24 0.33 27.5 48.1 16 2 3 
3 1.45 0.46 45.5 98.8 20 2 3 
4 0.94 0.08 9.5 70.6 9 2 3 
Comparative 
1 2.20 0.76 26.7 108.6 35 1 2 
Example 
2 2.66 1.02 57.1 87.4 (*)1 29 
1 2 
3 1.48 0.40 63.7 121.0 38 1 2 
__________________________________________________________________________ 
Note: (*)1 . . . This sheet curled into a cylinder form having a diameter 
of 29 mm. 
Table 1 clearly shows that the thermal transfer dye image-receiving sheets 
of Examples 1 to 4 in accordance with the present invention exhibited a 
high resistance to curling, a good travelling property in the printer and 
could record thereon clear dye images. 
However, the comparative image-receiving sheets of Comparative Examples 1 
to 3 significantly curled and often blocked the printer during the thermal 
transfer printing procedure. 
Example 5 
A thermal transfer dye image-receiving sheet was produced by the following 
procedures. 
1 Preparation of monoaxially oriented sheet (M1) for core layer 
A mixture of 85 parts by weight of a polypropylene resin with 5 parts by 
weight of a polyethylene resin and 15 parts by weight of calcium carbonate 
particles having an average size of 1.5 .mu.m was melt-kneaded in a 
melt-extruder at a temperature of 270.degree. C., and then extruded into a 
sheet form through an extruding slit of the extruder; and the resultant 
undrawn sheet was drawn at a draw ratio of 5.0 in the longitudinal 
direction of the sheet to provide a monoaxially oriented sheet (M1) for a 
core layer three-layered substrate sheet. 
2 Preparation of three-layered substrate sheet 
A mixture of 55 parts by weight of a polypropylene resin with 30 parts by 
weight of a polyethylene resin and 15 parts by weight of calcium carbonate 
particles having an average size of 1.5 .mu.m was melt-kneaded in a 
melt-extruder at a temperature of 270.degree. C.; the melt was extruded in 
a sheet form from the extruder; and the extruded sheet (S1) was laminated 
on the front surface of the monoaxially oriented sheet (M1). Also, a 
mixture of 55 parts by weight of a polypropylene resin with 45 parts by 
weight of calcium carbonate particles having an average size of 1.5 .mu.m 
was melt-kneaded in a melt-extruder at a temperature of 270.degree. C. and 
extruded in a sheet form from the extruder; and the extruded sheet (B1) 
was laminated on the back surface of the monoaxially oriented sheet (M1). 
The resultant three-layered sheet was drawn at a draw ratio of the 
transverse direction of the monoaxially oriented sheet (M1) at a 
temperature of 160.degree. C. 
The resultant oriented substrate sheet had a total thickness of 150 .mu.m 
and consisted of a monoaxially oriented front surface layer having a 
thickness of 60 .mu.m, a biaxially oriented core layer having a thickness 
of 40 .mu.m and a monoaxially oriented back surface layer having a 
thickness of 50 .mu.m. 
The front surface had a density of 0.9 g/cm.sup.3 and the back surface 
layer had a density of 1.2 g/cm.sup.3. 
Also, the resultant oriented substrate sheet exhibited a longitudinal 
thermal shrinkage of 0.94% and a transverse thermal shrinkage of 0.12% 
upon heating from 20.degree. C. to 120.degree. C. and a longitudinal 
tensile modulus of elasticity of 19.6 MPa and a transverse tensile modulus 
of elasticity of 68.5 MPa at a temperature of 120.degree. C. 
3 Production of thermal transfer dye image-receiving sheet 
A coating liquid (2) for a dye-receiving resin layer was prepared in the 
following composition. 
______________________________________ 
Component Part by weight 
______________________________________ 
Polyester resin (*)5 
100 
Silicone oil (*)6 3 
Polyisocyanate component (*)7 
5 
Toluene 300 
______________________________________ 
Note: 
(*)5 . . . Trademark: Vylon 200, made by Toyobo K.K. 
(*)6 . . . Trademark: KF 393 (release agent), made by Shinetsu Silicone 
K.K.) 
(*)7 . . . Trademark: Takenate (crosslinking agent), made by Takeda 
Yakuhin K.K. 
The coating liquid (2) was coated on the front surface of the substrate 
sheet and dried to form a dye-receiving resin sheet having a dry thickness 
of 5 .mu.m. 
The test results are shown in Table 2. 
Example 6 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 5, with the following exceptions. 
In the preparation of the monoaxially oriented sheet for the core layer, 
the width of the extruding slit of the melt-extruder was adjusted so as to 
provide a monoaxially oriented sheet (M2). 
In the preparation of the three-layered substrate sheet, a mixture of 75 
parts by weight of a polypropylene resin with 5 parts by weight of a 
polyethylene resin and 20 parts by weight of a polyethylene resin and 15 
parts by weight of calcium carbonate particles having an average size of 
1.5 .mu.m was melt-kneaded in a melt-extruder at a temperature of 
270.degree. C.; the melt was extruded into a sheet form from the extruder; 
and the extruded sheet (B2) was laminated on the back surface of the 
monoaxially oriented sheet (M2); and the resultant laminate was drawn at a 
draw ratio of 3.5 in the transverse direction at a temperature of 
160.degree. C. Also, a mixture of 50 parts by weight of a polypropylene 
resin with 25 parts by weight of a polyethylene resin and 25 parts by 
weight of calcium carbonate particles having an average size of 1.5 .mu.m 
was melt-kneaded in a melt-extruder at a temperature of 270.degree. C. and 
extruded into a sheet form from the extruder; and the extruded sheet (S2) 
was laminated on the front surface of the monoaxially oriented sheet (M2). 
The resultant three-layered sheet was drawn at a draw ratio of 3.0 in the 
transverse direction at a temperature of 160.degree. C. 
The resultant oriented substrate sheet had a total thickness of 250 .mu.m 
and consisted of a monoaxially oriented front surface layer having a 
thickness of 100 .mu.m, a biaxially oriented core layer having a thickness 
of 80 .mu.m and a monoaxially oriented back surface layer having a 
thickness of 70 .mu.m. 
The front surface layer had a density of 1.0 g/cm.sup.3 and the back 
surface layer had a density of 1.1 g/cm.sup.3. 
Also, the resultant oriented substrate sheet exhibited a longitudinal 
thermal shrinkage of 1.12% and a transverse thermal shrinkage of 0.35% 
upon heating from 20.degree. C. to 120.degree. C., and a longitudinal 
tensile modulus of elasticity of 24.8 MPa and a transverse tensile modulus 
of elasticity of 8.21 MPa at a temperature of 120.degree. C. 
The coating liquid (2) for a dye-receiving resin layer was coated on the 
front surface of the three layered, oriented substrate sheet in the same 
manner as in Example 1. 
The test results are shown in Table 2. 
Example 7 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 5, with the following exceptions. 
1 Preparation of monoaxially oriented sheet (M3) for core layer 
A mixture of 70 parts by weight of a polypropylene resin with 10 parts by 
weight of a polyethylene resin, and 20 parts by weight of calcium 
carbonate particles having an average size of 1.5 .mu.m was melt-kneaded 
in a melt-extruder at a temperature of 270.degree. C., and then extruded 
into a sheet form through an extruding slit of the extruder; and the 
resultant undrawn sheet was drawn at a draw ratio of 5.0 in the 
longitudinal direction of the sheet to provide a monoaxially oriented 
sheet (M3) for a core layer of a three-layered substrate sheet. 
2 Preparation of three-layered substrate sheet 
A mixture of 50 parts by weight of a polypropylene resin with 20 parts by 
weight of a polyethylene resin, 20 parts by weight of a polystyrene resin 
and 10 parts by weight of calcium carbonate particles having an average 
size of 1.5 .mu.m was melt-kneaded in a melt-extruder at a temperature of 
270.degree. C.; the melt was extruded in a sheet form from the extruder; 
and the extruded sheet (S3) was laminated on the front surface of the 
monoaxially oriented sheet (M3). Also, a mixture of 70 parts by weight of 
a polypropylene resin with 10 parts by weight of a polyethylene resin, 10 
parts by weight of a polystyrene resin and 10 parts by weight of calcium 
carbonate particles having an average size of 1.5 .mu.m was melt-kneaded 
in another melt-extruder at a temperature of 270.degree. C. and extruded 
in a sheet form from the extruder; and the extruded sheet (B3) was 
laminated on the back surface of the monoaxially oriented sheet (M1). 
The resultant three-layered sheet was drawn at a draw ratio of 6.0 in the 
transverse direction of the monoaxially oriented sheet (M3). 
The resultant oriented substrate sheet had a total thickness of 80 .mu.m 
and consisted of a monoaxially oriented front surface layer having a 
thickness of 30 .mu.m, a biaxially oriented core layer having a thickness 
of 30 .mu.m and a monoaxially oriented back surface layer having a 
thickness of 20 .mu.m. 
The front surface layer had a density of 0.9 g/cm.sup.3 and the back 
surface layer had a density of 1.0 g/cm.sup.3. 
Also, the resultant oriented substrate sheet exhibited a longitudinal 
thermal shrinkage of 1.732% and a transverse thermal shrinkage of 0.46% 
upon heating from 20.degree. C. to 120.degree. C., and a longitudinal 
tensile modulus of elasticity of 11.3 MPa and a transverse tensile modulus 
of elasticity of 85.9 MPa at a temperature of 120.degree. C. 
3 Production of thermal transfer dye image-receiving sheet 
The same coating liquid (2) as in Example 5 was coated on the front surface 
of the substrate sheet and dried in the same manner as in Example 5. 
Comparative Example 4 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 5, with the following exceptions. 
A single-layered substrate sheet was produced by melt-kneading a mixture of 
75 parts by weight of a polypropylene resin, with 5 parts by weight of a 
polyethylene resin and 20 parts by weight of calcium carbonate particles 
having an average size of 1.5 .mu.m in a melt-extruder at a temperature of 
270.degree. C., extruding the melt from the extruder, and biaxially 
drawing the resultant undrawn sheet (M4) at a draw ratio of 5.0 in the 
longitudinal direction and at a draw ratio of 5.0 in the transverse 
direction. The resultant single-layered substrate sheet having a thickness 
of 220 .mu.m was employed in place of the three layered substrate sheet. 
The test results are shown in Table 2. 
Comparative Example 5 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 5, with the following exceptions. 
1 Preparation of monoaxially oriented sheet (M5) for core layer 
The same procedures as in Example 5 were carried out except that the width 
of the extruding slit of the melt-extruder was changed. 
2 Preparation of three layered oriented substrate sheet 
The same laminating procedures as in Example 5 were carried out except that 
the extruded undrawn sheets (S4) and (B4), which respectively have the 
same compositions as (S1) and (B1) of Example 5, were laminated on the 
front and back surfaces of the monoaxially oriented sheet (M5); and the 
resultant three layered sheet was drawn at a draw ratio of 7.5 in the 
transverse direction. 
The resultant oriented substrate sheet had total thickness of 1.90 .mu.m 
and consisted of a monoaxially oriented front surface layer having a 
thickness of 50 .mu.m, a biaxially oriented core layer having a thickness 
of 80 .mu.m and a monoaxially oriented back surface layer having a 
thickness of 60 .mu.m. 
The front surface layer had a density of 0.9 g/cm.sup.3 and the back 
surface layer had a density of 1.2 g/cm.sup.3. 
Also, the resultant oriented substrate sheet exhibited a longitudinal 
thermal shrinkage of 2.20% and a transverse thermal shrinkage of 0.76% 
upon heating from 20.degree. C. to 120.degree. C. and a longitudinal 
tensile modulus of elasticity of 26.7 MPa and a transverse tensile modulus 
of elasticity of 108.0 MPa at a temperature of 120.degree. C. 
3 In the production of thermal transfer dye image-receiving sheet, the same 
coating liquid (2) as in Example 5 was coated on the front surface of the 
substrate sheet and dried to form a dye-receiving resin layer having a 
thickness of 5 .mu.m. 
The test results are shown in Table 2. 
Comparative Example 6 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 5, with the following exceptions. 
1 Preparation of monoaxially oriented sheet (M6) for core layer 
The same procedures as in Example 5 were carried out except that the width 
of the extruding slit of the melt-extruder was changed. 
2 Preparation of three-layered oriented substrate sheet 
A mixture of 75 parts by weight of a polypropylene resin with 25 parts by 
weight of calcium carbonate particles having an average size of 1.5 .mu.m 
was melt-kneaded in a melt-extruder at a temperature of 270.degree. C.; 
the melt was extruded in a sheet form from the extruder; and the extruded 
sheet (B5) was laminated on the back surface of the monoaxially oriented 
sheet (M6). The laminate was drawn at a draw ratio of 3.5 in the 
transverse direction. Also, a mixture of 95 parts by weight of a 
polypropylene resin with 5 parts by weight of calcium carbonate particles 
having an average size of 1.5 .mu.m was melt-kneaded in another 
melt-extruder at a temperature of 270.degree. C. and extruded into a sheet 
form from the extruder; and the extruded sheet (S5) was laminated on the 
front surface of the monoaxially oriented sheet (M6). 
The resultant three-layered sheet was drawn at a draw ratio of 3.5 in the 
transverse direction of the monoaxially oriented sheet (M6). 
The resultant oriented substrate sheet had a total thickness of 195 .mu.m 
and consisted of a monoaxially oriented front surface layer having a 
thickness of 80 .mu.m, a biaxially oriented core layer having a thickness 
of 50 .mu.m and a monoaxially oriented back surface layer having a 
thickness of 65 .mu.m. 
The front surface layer had a density of 1.2 g/cm.sup.3 and the back 
surface layer had a density of 1.2 g/cm.sup.3. 
Also, the resultant oriented substrate sheet exhibited a longitudinal 
thermal shrinkage of 1.48% and a transverse thermal shrinkage of 0.40% 
upon heating from 20.degree. C. to 120.degree. C., and a longitudinal 
tensile modulus of elasticity of 63.7 MPa and a transverse tensile modulus 
of elasticity of 121.0 MPa at a temperature of 120.degree. C. 
3 Production of thermal transfer dye image-receiving sheet 
The same coating liquid (2) as in Example 5 was coated on the front surface 
of the substrate sheet and dried to form a dye-receiving resin layer with 
a thickness of 5 .mu.m. 
The test results are shown in Table 2. 
Comparative Example 7 
A thermal transfer dye image-receiving sheet was produced and tested by the 
same procedures as in Example 5, with the following exceptions. 
1 Preparation of monoaxially oriented sheet (M7) for core layer 
The same procedures as in Example 5 were carried out except that the width 
of the extruding slit of the melt-extruder was changed. 
2 Preparation of three-layered oriented substrate sheet 
A mixture of 70 parts by weight of a polypropylene resin with 10 parts by 
weight of a polyethylene resin, 10 parts by weight of a polystyrene resin 
and 10 parts by weight of calcium carbonate particles having an average 
size of 1.5 .mu.m was melt-kneaded in a melt-extruder at a temperature of 
270.degree. C.; the melt was extruded into a sheet form from the extruder; 
and the extruded sheet (S6) was laminated on a front surface of the 
monoaxially oriented sheet (M7). Also, a mixture of 50 parts by weight of 
a polypropylene, 20 parts by weight of a polyethylene resin, 20 parts by 
weight of a polystyrene and 10 parts by weight of calcium carbonate 
particles having an average size of 1.5 .mu.m was melt-kneaded in another 
melt extruder at a temperature of 270.degree. C., and extruded into a 
sheet form from the extruder; and the resultant extruded sheet (B6) was 
laminated on the back surface layer of the oriented sheet (M7). 
The resultant three-layered sheet was drawn at a draw ratio of 6.0 in the 
transverse direction. 
The resultant oriented substrate sheet had a total thickness of 135 .mu.m 
and consisted of a monoaxially oriented front surface layer having a 
thickness of 40 .mu.m, a biaxially oriented core layer having a thickness 
of 75 .mu.m and a monoaxially oriented back surface layer having a 
thickness of 20 .mu.m. 
The front surface layer had a density of 1.1 g/cm.sup.3 and the back 
surface layer had a density of 0.9 g/cm.sup.3. 
Also, the resultant oriented substrate sheet exhibited a longitudinal 
thermal shrinkage of 1.68% and a transverse thermal shrinkage of 0.72% 
upon heating from 20.degree. C. to 120.degree. C., and a longitudinal 
tensile modulus of elasticity of 58.6 MPa and a transversal tensile 
modulus of elasticity of 67.5 MPa at a temperature of 120.degree. C. 
3 Production of thermal transfer dye image-receiving sheet 
The same coating liquid (2) as in Example 5 was coated on the front surface 
of the substrate sheet and dried to form a dye-receiving resin layer with 
a thickness of 5 .mu.m. 
The test results are shown in Table 
TABLE 2 
__________________________________________________________________________ 
Substrate sheet 
Thickness (.mu.m) 
Density (g/cm.sup.3) Traveling 
Clear- 
Front 
Back Front 
Back Tensile modulus of 
property 
ness 
surface 
surface 
surface 
surface 
Thermal shrinkage (%) 
elasticity (MPa) 
Curling 
in of dye 
Example No. 
layer 
layer 
Total 
layer 
layer 
Longitudinal 
Transverse 
Longitudinal 
Transverse 
(mm) printer 
images 
__________________________________________________________________________ 
Example 
5 60 50 150 
0.9 1.2 0.94 0.12 19.6 68.5 14 2 3 
6 100 70 250 
1.0 1.1 1.12 0.35 24.8 82.1 18 2 3 
7 30 20 80 0.9 1.0 1.32 0.46 11.3 85.9 17 2 3 
Comparative 
4 -- -- 220 
(1.1) 2.66 1.02 57.1 87.4 (*)1 29 
1 2 
Example 
5 50 60 190 
0.9 1.2 2.20 0.76 26.7 108.0 
35 1 2 
6 80 65 195 
1.2 1.2 1.48 0.40 63.7 121.0 
38 1 2 
7 40 20 135 
1.1 0.9 1.68 0.72 58.6 67.5 (*)1 15 
1 2 
__________________________________________________________________________ 
Note: (*)1 . . . The sheet curled into a cyldiner form having a diameter 
shown in the table. 
Table 2 clearly shows that the thermal transfer dye image-receiving sheets 
of Examples 5 to 7 in accordance with the present invention exhibited a 
high resistance to curling, a good travelling property in the printer and 
could record thereon clear dye images. 
However, the comparative image-receiving sheets of Comparative Examples 4 
to 7 significantly curled and often blocked the printer during the thermal 
transfer printing procedure.