Medical image forming method, forming apparatus of the same, and thermal transfer sheet of the same

A medical image forming method including the steps of superposing a three-primary-color thermal transfer sheet and an image receiving sheet, the thermal transfer sheet having a base film and three color dye layers of yellow, magenta, and cyan, each of the dye layer being composed of a dye and a binder, the image receiving sheet having a dye accepting layer; heating the rear surface of the thermal transfer sheet with a heating device in an image shape; and driving and controlling the heating device with a control unit so as to form a full color image on the image receiving sheet. The control unit is adapted to compensate tones of the image so that chromaticity values thereof formed on the image receiving sheet are in a region defined by four points of (a*=0, b*=0), (a*=20, b*=-5), (a*=18, b*=15), and (a*=0, b*=15) when an achromatic color signal is input and L*=80. According to an aspect of the present invention, the control unit is adapted to compensate tones of three primary colors so that the density graduation of light red of an image in accordance with a light red signal sent to the control unit becomes high and thereby the low density region (light region) of the image formed in accordance with a achromatic color signal becomes reddish. According to another aspect of the present invention, since the dye layers are formed so that the light region becomes reddish and the dark region greenish, images where colors from light orange to light red can be easily distinguished are formed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a medical image forming method and a 
forming apparatus of the same, in particular, to a forming method of 
clearly readable medical images of the surfaces of living tissues (such as 
the mouth, esophagus, and stomach walls) of a human body with sublimating 
dyes (thermal transfer dyes) through an endoscope or the like. 
2. Description of the Related Art 
As the needs of full-color prints increase, a variety of thermal transfer 
techniques have been developed. As an example of these techniques, 
thermosensitive sublimating transfer technique for transferring 
sublimating dyes as color materials held on a base film such as a 
polyester film to an image receiving sheet on which a synthetic resin such 
as polyester is coated is known. In this technique, the amount of energy 
supplied to a heating device (for example, a thermal head and a laser), 
which heats the rear surface of a thermal transfer sheet, is adjusted in 
accordance with electric signals (image signals) received from an 
endoscope or the like, thereby controlling the transferring amount of dyes 
to an image receiving sheet. When three types of dyes (three primary 
colors of yellow, magenta, and cyan) are used and the thermal transfer 
process is performed three times, a multi-tone full color image can be 
obtained. 
In this thermal transfer technique, since the thermal transfer efficiency 
depends on the color materials, when image signals are converted into 
thermal energy to be supplied to the heating device, compensations for 
these color materials are performed. 
In conventional image forming apparatuses according to this technique, the 
amount of thermal energy of each of the three primary colors is adjusted 
and their tones are compensated so that an achromatic color image can be 
formed in accordance with an achromatic color signal being input. 
When images of the surfaces of living tissues such as the mouth, esophagus, 
and stomach walls are formed, red color is much more frequently used than 
other colors due to the property of the living tissues. Moreover, in the 
clinical situation, medical doctors tend to diagnose the diseases of 
patients based on delicate changes of red color. Thus, the reproduction of 
red color is very important. 
However, in images obtained by the conventional tone compensations, the low 
density region of red color was not satisfactory. Therefore, the medical 
doctors could not precisely diagnose diseases of their patients with these 
images. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a medical image forming 
method with high reproducibilities of light red and tones. 
An aspect of the present invention is a medical image forming method 
comprising the steps of superposing a three-primary-color thermal transfer 
sheet and an image receiving sheet, the thermal transfer sheet having a 
base film and three color dye layers of yellow, magenta, and cyan, each of 
the dye layer being composed of a dye and a binder, the image receiving 
sheet having a dye accepting layer, carrying out heat printing in 
accordance with image information, and driving and controlling the heating 
device with a control unit so as to form a full color image on the image 
receiving sheet, wherein the control unit is adapted to compensate tones 
of the image so that chromaticity values thereof formed on the image 
receiving sheet are in a region defined by four points of (a*=0, b*=0), 
(a*=20, b*=-5), (a*=18, b*=15), and (a*=0, b*=15) when an achromatic color 
signal is input and L*=80. 
Another aspect of the present invention is a medical image forming 
apparatus, comprising a heating device for heating the rear surface of a 
three-primary-color thermal transfer sheet in an image shape and for 
forming a full color image on an image receiving sheet, the thermal 
transfer sheet having a base film and three color dye layers of yellow, 
magenta, and cyan, each of the dye layer being composed of a dye and a 
binder, and a control unit for driving and controlling the heating device 
in accordance with an input image signal, wherein the control unit is 
adapted to compensate tones of the image so that chromaticity values 
thereof formed on the image receiving sheet are in a region defined by 
four points of (a*=0, b*=0), (a*=20, b*=-5), (a*=18, b*=15), and (a*=0, 
b*=15) when an achromatic color signal is input and L*=80. 
A further aspect of the present invention is a thermal transfer sheet 
having a base film and at least three dye layers of yellow, magenta, and 
cyan, the dye layers being layered on the base film, wherein the back 
surface of the thermal transfer sheet is adapted to be heated by a heating 
device driven and controlled by a control unit so as to form a full color 
image on an image receiving sheet, and wherein chromaticity values of an 
image formed on the image receiving sheet are in a region defined by four 
points of (a*=0, b*=0), (a*=20, b*=-5), (a*=18, b*=15), and (a*=0, b*=15) 
when an achromatic color signal is input to the control unit and L*=80 or 
in another region defined by four points of (a*=0, b*=20), (a*=0, b*=-10), 
(a*=-20, b*=-20), and (a*=-20, b*=15) when an achromatic color signal is 
input to the control unit and L*=20. 
According to the present invention, the bright region of an image becomes 
reddish and the dark region thereof greenish. Thus, the light red can be 
easily distinguished. As a result, the surfaces of reddish living tissues 
such as the mouth, esophagus, and stomach walls of a human body can be 
precisely reproduced. 
These and other objects, features and advantages of the present invention 
will become more apparent in light of the following detailed description 
of a best mode embodiment thereof, as illustrated in the accompanying 
drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
First Embodiment 
Basic Composition 
Next, with reference to the accompanying drawings, an embodiment of the 
present invention will be shown. FIGS. 1 and 2 shows a first embodiment of 
the present invention. In FIG. 1, a thermal transfer sheet 20 and an image 
receiving sheet 30 are layered. The thermal transfer sheet 20 comprises a 
base film 22 (such as a polyester film) and dye layers 21 for three 
primary colors (yellow, magenta, and cyan). Each dye layer 21 consists of 
a corresponding dye (yellow, magenta, or cyan) and a corresponding binder. 
The dye layers 21 are successively layered on the front surface of the 
base film 22. The image receiving sheet 30 comprises a base sheet 32 and a 
dye accepting layer 31. On the front surface of the base sheet 32, the dye 
accepting layer 31 is disposed. 
On the back surface of the thermal transfer sheet 20 (on the base film 22 
side), a thermal head 9 which heats the thermal transfer sheet 20 is 
disposed. This thermal head 9 is driven and controlled by a control unit 
10. The back surface of the thermal transfer sheet 20 is heated by the 
thermal head 9 in accordance with the shape of an image. By repeating the 
heating process for the three primary color dye layers of the thermal 
transfer sheet 20, a full color image 33 can be formed on the dye 
accepting layer 31 of the image receiving sheet 30. 
In FIG. 1, reference numeral 1 is an image signal input terminal. Electric 
signals (image signals) of a color image received from an electronic 
camera of an endoscope 15, a video tape recorder, or the like are supplied 
to the image signal input terminal 1. Reference numeral 2 is a matrix 
circuit. The matrix circuit 2 decomposes the color image signals received 
from the input terminal 1 into three primary color (yellow, magenta, and 
cyan) components on the pixel-by-pixel basis. Each decomposed color 
component is stored in an individual frame memory 4 through an individual 
A/D converting circuit 3. Thereafter, by a color selecting switch 5, one 
of the three primary colors is selected. Thus, the relevant frame memory 4 
is connected to a pulse width modulating circuit 6. The pulse width 
modulating circuit 6 reads compensation data in accordance with the 
relevant color from the corresponding pulse width memory 7 and compensates 
the pulse width of the color component (namely, compensates the tone of 
the color component). The resultant color component is sent from the pulse 
modulating circuit 6 to an output portion 8. The output portion 8 drives 
and controls the thermal head 9, thereby reproducing a desired full color 
image on the image receiving sheet 30. 
The control unit 10 comprises the input terminal 1, the matrix circuit 2, 
the A/D converting circuits 3, the frame memories 4, the color selecting 
switch 5, the pulse modulating circuit 6, the pulse width memory 7, and 
the output portion 8. 
According to the present invention, since data received from the pulse 
width memory 7 is optimized and the chromaticity range of the image 33 
formed on the image receiving sheet 30 is specifically designated, 
excellent medical images can be obtained. 
In other words, when an achromatic color signal is sent to the input 
terminal 1 of the control unit 10, the control unit 10 optimizes data 
received from the pulse width memory 7, compensates the tones in a region 
defined by four points of (a*=0, b*=0), (a*=20, b*=-5), (a*=18, b*=15), 
and (a*=0, b*=15) in the case L*=80 and in a region defined by four points 
of (a*=0, b*=20), (a*=0, b*=-10), (a*=-20, b*=-20), and (a*=-20, b*=15) in 
the case L*=20, and adjusts the thermal head 9. 
FIG. 2 shows the chromaticity values in accordance with JIS-Z8722 and 
JIS-Z8730 (JIS stands for Japanese Industrial Standard). In particular, 
JIS-Z8730 defines CIE1976. 
According to JIS-Z8722 and JIS-Z8730, chromaticity values are represented 
with three values L*, a*, and b*. L* represents lightness. As the value of 
L* increases, the lightness becomes strong. a* represents the degree of 
red. As the value of a* increases, the degree of red becomes strong. When 
the value of a* is minus, green appears instead of red. b* represents the 
degree of yellow. As the value of b* increases, the degree of yellow 
becomes strong. When the value of b* is minus, blue appears instead of 
yellow. When both the values of a* and b* are zero, achromatic color 
appears. 
Next, with specific examples and their comparisons, the present invention 
will be described in detail. 
Examples (Nos. 1 to 20) and Comparisons (Nos. 21 to 26) 
With three-color (yellow, magenta, and cyan) thermal transfer sheets and 
image receiving sheets which were commercially available, images were 
formed by a test printer having a thermal head. 
300 sets of data for the pulse width memory were prepared. Each of the 
prepared data was sent directly to the pulse width modulating circuit, not 
through the pulse width memory. With the same data as the pulse width 
memory (after the same tone compensation was performed), the following 
three types of images were formed on the image receiving sheets. In other 
words, in accordance with image signals from the input terminal, the same 
tone compensation was performed by the control unit, thereby forming three 
types of images. 
Image 1: 256 tones of achromatic color 
Image 2: Video input image of esophagus by endoscope 
Image 3: Video input image of pyloric region of stomach by endoscope 
Evaluation Method 
Image 1: With a spectral color difference meter CM-1000 (made by Minolta K. 
K.), the chromaticity values L*, a*, and b* of CIE for the image 1 were 
measured. 
Images 2 and 3: Under the following criteria, the images 2 and 3 were 
visually measured. 
.circleincircle.: Very clear. Details of tissue could be easily 
distinguished. 
.largecircle.: Clear. Details of tissue could be distinguished. 
.DELTA.: Somewhat unclear. Details of tissue-were distinguished with 
difficulty. 
x: Completely unclear. Details of tissue could not be distinguished. 
The results of this evaluation are shown in the following table. 
TABLE 1 
______________________________________ 
Image 1 
When L* is about 80 
When L is about 20 
Image Image 
No. a* b* a* b* 2 3 
______________________________________ 
1 12.08 1.96 -4.28 -10.31 .circleincircle. 
.circleincircle. 
2 18.63 -3.02 -4.10 -6.52 .circleincircle. 
.circleincircle. 
3 11.78 11.43 -8.31 -18.26 .circleincircle. 
.circleincircle. 
4 4.05 3.93 -12.00 -16.06 .circleincircle. 
.circleincircle. 
5 7.72 6.32 -14.03 -14.21 .circleincircle. 
.circleincircle. 
6 16.53 3.89 -14.16 2.34 .circleincircle. 
.circleincircle. 
7 6.65 12.48 -4.36 12.31 .circleincircle. 
.circleincircle. 
8 13.62 6.48 -8.07 2.78 .circleincircle. 
.circleincircle. 
9 3.28 2.04 -12.08 -8.38 .circleincircle. 
.circleincircle. 
10 16.42 -1.06 -13.88 -19.20 .circleincircle. 
.circleincircle. 
11 4.13 14.37 -4.55 3.45 .circleincircle. 
.circleincircle. 
12 1.78 7.45 -12.67 9.84 .circleincircle. 
.circleincircle. 
13 1.98 0.88 -2.37 -0.72 .circleincircle. 
.circleincircle. 
14 6.56 -0.34 -8.68 - 5.67 .circleincircle. 
.circleincircle. 
______________________________________ 
TABLE 2 
______________________________________ 
(CONTINUED FROM TABEL 1) 
Image 1 
When L* is about 80 
When L is about 20 
Image Image 
No. a* b* a* b* 2 3 
______________________________________ 
15 4.22 -0.08 -7.79 1.18 .circleincircle. 
.circleincircle. 
16 2.11 5.87 2.34 -4.21 .circle. 
.circle. 
17 7.63 9.05 -2.54 16.28 .circle. 
.circle. 
18 12.28 3.96 6.23 3.84 .circle. 
.circle. 
19 13.10 -2.33 -0.86 -13.56 .circle. 
.circle. 
20 16.73 8.29 11.45 -3.66 .circle. 
.circle. 
21 2.22 -1.76 0.54 -1.84 .DELTA. 
.DELTA. 
22 4.48 -1.66 -13.42 8.30 .DELTA. 
.DELTA. 
23 10.28 -4.22 -0.67 0.22 .DELTA. 
.DELTA. 
24 -8.31 6.03 -2.65 1.73 X X 
25 3.65 -8.56 5.59 3.67 X X 
26 -6.73 -3.21 -2.21 4.40 X X 
______________________________________ 
Effects of First Embodiment 
According to the medical image forming method of the present invention, 
since the tones of the three primary colors are compensated so that the 
density slope of light red of an image formed on an image receiving sheet 
in accordance with an image signal of light red is increased (namely, the 
low density region (light region of L*=80) of an image formed in 
accordance with an input of an achromatic color image signal becomes 
reddish and the high density region (dark region of L*=20) thereof becomes 
bluish green, the distinction of red which is the complementary of bluish 
green can be easily performed. 
Second Embodiment 
Basic Composition 
Next, a second embodiment of the present invention will be described. 
An example of a thermal transfer sheet 20 used in the second embodiment 
basically comprises a base film 22 and dye layers 21 for three primary 
colors like the first embodiment shown in FIG. 1. The dye layers 21 are 
disposed on the base film 22. The base film 22 of the thermal transfer 
sheet 20 according to the present invention can be any known material 
which has a heat resistance and hardness to some extent. For example, as 
the material of the base film 22, a paper, one of various processed 
papers, a polyester film, a polystyrene film, a polypropylene film, a 
polysulfone film, an aramid film, a polycarbonate film, a polyvinyl 
alcohol film, a cellophane, or the like can be used, the thickness thereof 
being preferably in the range from 0.5 to 50 .mu.m, more preferably in the 
range from 3 to 10 .mu.m. Most preferably, the base film 22 is a polyester 
film. The base film 22 can be either a cut type or a continuous film type. 
Each dye layer 21 formed on the front surface of the base film 22 is a 
layer where a corresponding dye is held by a corresponding binder resin. 
Any dye which is known and used for conventional thermal transfer sheets 
can be used for each dye layer 21 as long as it can be effectively used 
for the present invention. Preferably, as the material of the red dye, MS 
Red G, Macrolex Red Violet R, Ceres Red 7B, Samaron Red HBSL, Resolin Red 
F3BS, or the like can be used. As the material of the yellow dye, Phorone 
Brilliant Yellow 6GL, PTY-52, Macrolex Yellow 6G, or the like can be used. 
As the material of the blue dye, Kayaset Blue 714, Waxoline Blue AP-FW, 
Foron Brilliant Blue S-R, MS Blue 100, or the like can be used. 
As a binder resin which holds the above-mentioned dies, any known binder 
resin can be used. Preferably, as the material of the binder resin, a 
cellulose resin (such as ethyl cellulose, hydroxyethyl cellulose, 
ethylhydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, acetic 
cellulose, or acetate butyric cellulose), a vinyl resin (such as polyvinyl 
alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl 
pyrrolidone, or polyacrylic amide), polyester, or the like can be used. 
Among these materials, a cellulose resin, an acetal resin, a butyral 
resin, a polyester resin, or the like is preferable from stand points of 
heat resistance and dye transfer property. In the dye layers, when 
necessary, various known additives can be contained. 
Each dye layer 21 is produced in the following manner. An above-mentioned 
sublimating dye, an above-mentioned binder resin, a surface lubricant, and 
if necessary other components are added in a proper solvent so as to 
dissolve or disperse these components. Thus, a dye layer forming paint or 
a dye layer forming ink is made. This paint or ink is coated on the base 
film 22 and dried. The thickness of the dye layer 21 is preferably in the 
range from 0.2 to 5.0 .mu.m, more preferably in the range from 0.4 to 2.0 
.mu.m. The amount of sublimating dye to be contained in the dye layer 21 
is preferably in the range from 5 to 90% by weight of the dyeing layer, 
more preferably, in the range from 10 to 70% by weight thereof. 
In addition, according to the present invention, an intermediate layer can 
be disposed between the base film 22 and the dye layers 21 so as to 
improve the adhesive property and cushioning property. For example, as the 
material of the intermediate layer, a polyurethane resin, an acrylic 
resin, a polyethylene resin, a butadiene rubber, an epoxy resin, or the 
like can be used. The thickness of the intermediate layer is preferably in 
the range from 0.1 to 5 .mu.m. The intermediate layer can be formed in the 
same manner as the above-mentioned dye layers. 
As an example of the image receiving sheet 30 for forming an image along 
with the thermal transfer sheet 20, any material can be used as long as 
the surface on the thermal transfer sheet side has a dye accepting 
property according to the above-mentioned dyes like the first embodiment 
shown in FIG. 1. For example, the image receiving sheet 30 comprises the 
base sheet 32 and the dye accepting layer 31 layered thereon. For example, 
as the material of the base sheet 32, a paper, a metal, a glass, a 
synthetic resin, or the like which does not have a dye accepting property 
can be used. 
As a thermal energy applying means which is used for performing thermal 
transfer with the thermal transfer sheet 20 and the image receiving sheet 
30, any known thermal energy applying means can be used. For example, by 
using a thermal printer with a thermal head 9 shown in FIG. 1 (for 
example, a video printer VY-100 made by Hitachi K. K.), the heating time 
of the thermal head is controlled so that thermal energy of 5 to 100 
mj/mm.sup.2 is applied to the image receiving sheet 30, thereby forming a 
desired image thereon. In other words, the thermal head 9 is driven and 
controlled by the control unit 10 in the same manner as the first 
embodiment shown in FIG. 1 so that the rear surface of the thermal 
transfer sheet 20 is heated for a predetermined time period. 
As a preferable example of the thermal transfer sheet 20 according to the 
present invention, when the dye layers 21 of three primary colors (yellow, 
magenta, and cyan) are layered in succession on the base film 22, the dye 
of magenta is selected so that it has higher thermal transfer property 
than the dyes of yellow and cyan. With this thermal transfer sheet 20, 
when a color image is formed on an image receiving sheet 30 under the 
normal image forming condition in which the tone compensations of the 
first embodiment are not performed, the regions from orange to red of the 
color image are emphasized. 
With the coating amount of solid component of dye layer 21 of yellow being 
in the range from 0.8 to 1.1 g/m.sup.2, that of dye layer 21 of magenta 
being in the range from 0.6 to 0.9 g/m.sup.2, and that of dye layer 21 of 
cyan being in the range from 10 to 15 g/m.sup.2 when a color image is 
formed under the normal image forming conditions, the regions from orange 
to red of the color image are emphasized. 
As a feature of colors of dye layers 21 composed of sublimating dyes, when 
the coating amount thereof is small, due to large thermal transfer rate an 
image can be formed with a small amount of thermal energy being applied. 
On the other hand, when the coating amount is large, although the amount 
of energy required for forming an image is larger than the above case, the 
maximum density becomes large. In other words, the colors of the dye 
layers and their maximum densities can be adjusted by the coating amount 
thereof. According to the present invention, when each dye layer is coated 
for the above-mentioned coating amount and a color image is formed under 
the normal image forming conditions, the regions from orange to red of the 
color image are emphasized. 
Example 
Next, a practical example of the second embodiment will be described. 
A heat resisting treatment was performed for the rear surface (opposite to 
the dye layer 21) of the base film 22 (a polyethylene terephthalate film 
with a thickness of 6 .mu.m). The following dye forming inks with these 
components were made. Thereafter, the inks were coated on the front 
surface of the base film by gravure-printing technique and then dried. As 
a result, the thermal transfer sheet according to the present invention 
was produced. 
Dye Layer Ink A (Cyan Ink) 
Dye: Kayaset Blue 714, made by Nippon Kayaku K. K. . . . 4.0 parts 
Resin: Polyvinyl acetoacetal, KS-5D, made by Sekisui Kagaku K. K. . . . 4.0 
parts 
Particles: Polyethylene wax, AF-31, made by BASF . . . 0.3 parts 
Solvent: Toluene/methyl-ethyl ketone (weight ratio 1/1) . . . 92.0 parts 
Dye Layer Ink B (Magenta Ink) 
Dye: Baymicron VPSN 2670, made by Bayer . . . 0.3 parts 
Resin: Polyvinyl acetoacetal, KS-5D, made by Sekisui Kagaku K. K. . . . 4.0 
parts 
Particles: Polyethylene wax, AF-31, made by BASF . . . 0.3 parts 
Solvent: Toluene/methyl-ethyl ketone (weight ratio 1/1) . . . 93.0 parts 
Dye Layer Ink C (Yellow Ink) 
Dye: Macrolex Yellow 6G, made by Bayer . . . 2 parts 
Resin: Polyvinyl acetoacetal, KS-5D, made by Sekisui Kagaku K. K. . . . 3.0 
parts 
Particles: Polyethylene wax, AF-31, made by BASF . . . 0.2 parts 
Solvent: Toluene/methyl-ethyl ketone (weight ratio 1/1) . . . 95.0 parts 
Next, as a base sheet 32, a synthetic paper Yupo (with a thickness of 150 
.mu.m) was used. Then, the following coating solution with these 
components for the accepting layer was coated on one surface of the base 
sheet 32 so that the amount of accepting layer dried became 4.5 g/m.sup.2. 
Thereafter, the base sheet 32 was dried for 30 minutes at 100.degree. C. 
As a result, an image receiving sheet 30 for use in the present invention 
and a comparison was obtained. 
Composition of Coating Solution for Dye Accepting Layer 
Polyester resin (Vylon 103, made by Toyobo K. K.) . . . 100.0 parts 
Amino-denatured silicone oil (X-22-343, made by Shinetsu Kagaku Kogyo K. 
K.) . . . 0.5 parts 
Epoxy-denatured silicone oil (KF-393, made by Shinetsu Kagaku Kogyo K. K.) 
. . . 0.5 parts 
Toluene/methyl-ethyl ketone (weight ratio 1/1) . . . 500 parts 
The above-mentioned thermal transfer sheet 20 and the image receiving sheet 
30 were layered so that the dye layers 21 of three colors were opposed to 
the dye accepting layer 31. With a thermal head 9 (KMT-85-6, MPD2), a 
thermal head recording was performed for the rear surface of the thermal 
transfer sheet 20 in the conditions where a head applying voltage is 12.0 
V, a step pattern of applying pulse width starts from 16.0 msec/line with 
a decrement of 1 msec, and a scanning width is 6 lines/mm (33.3 
msec/line). In this example, the reflection density of each step of the 
print image was measured with a density meter (Macbeth RD-918) so as to 
compare the thermal transfer property of the dyes of the dye layers 21. 
In addition, with the above-mentioned thermal transfer sheet 20 and the 
image receiving sheet 30, under the control of a control unit 10 of a 
video printer (such as VY-200 made by Hitachi K. K. or UP-5000 made by 
Sony K. K.), image signals were input and evaluated. 
Image 1: 64 tones of achromatic color 
Image 2: Video input image of esophagus by endoscope 
Image 3: Video input image of pyloric region of stomach by endoscope 
Evaluation Method 
Image 1: With a spectral color difference meter CM-1000 (made by Minolta K. 
K.), the chromaticity values L*, a*, and b* of CIE for the image 1 were 
measured. 
Images 2 and 3: Under the following criteria, the images 2 and 3 were 
visually measured. 
.circleincircle.: Very clear. Details of tissue could be easily 
distinguished. 
.largecircle.: Clear. Details of tissue could be distinguished. 
.DELTA.: Somewhat unclear. Details of tissue were distinguished with 
difficulty. 
x: Completely unclear. Details of tissue could not be distinguished. 
The results of this evaluation are shown in the following tables. 
TABLE 3 
__________________________________________________________________________ 
EVALUATION BY VY-200 
Coating Image 1 
Amount 
Comparison of Thermal 
When L* is about 80 
When L* is about 20 
Image 
Image 
No 
(g/m.sup.2) 
Transfer Property 
a* b* a* b* 2 3 
__________________________________________________________________________ 
1 Ink When pulse width is 11 msec, 
7.43 12.62 
-4.17 
-1.35 
.circleincircle. 
.circleincircle. 
A: 1.06 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
B: 0.60 
When pulse width is 5 msec, 
C: 0.82 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
2 When pulse width is 11 msec, 
5.26 8.71 -7.38 
-5.30 
.circleincircle. 
.circleincircle. 
A: 1.25 
OD.sub.B &gt; OD.sub.A &gt; OD.sub.C 
B: 0.71 
When pulse width is 5 msec, 
C: 0.92 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
3 When pulse width is 11 msec, 
3.06 4.67 - 5.54 
-7.22 
.circleincircle. 
.circleincircle. 
A: 1.40 
OD.sub.B &gt; OD.sub.A &gt; OD.sub.C 
B: 0.87 
When pulse width is 5 msec, 
C: 1.09 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
4 When pulse width is 11 msec, 
9.91 -0.72 
-3.48 
-5.34 
.circle. 
.circle. 
A: 1.06 
OD.sub.B &gt; OD.sub.A .gtoreq. OD.sub.C 
B: 0.60 
When pulse width is 5 msec, 
C: 1.09 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
__________________________________________________________________________ 
TABLE 4 
__________________________________________________________________________ 
(CONTINUED FROM TABLE 3) 
__________________________________________________________________________ 
5 When pulse width is 11 msec, 
11.06 
14.31 
-4.19 
-3.79 
.circle. 
.circle. 
A: 1.40 
OD.sub.B &gt; OD.sub.C .gtoreq. OD.sub.A 
B: 0.60 
When pulse width is 5 msec, 
C: 0.82 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
6 When pulse width is 11 msec, 
11.37 
-1.58 
-4.31 
4.66 .DELTA. 
.DELTA. 
A: 1.06 
OD.sub.B .gtoreq. OD.sub.C &gt; OD.sub.A 
B: 0.87 
When pulse width is 5 msec, 
C: 1.09 
OD.sub.B .gtoreq. OD.sub.A &gt; OD.sub.C 
7 When pulse width is 11 msec, 
5.94 
14.23 
-6.02 
-8.33 
.DELTA. 
.DELTA. 
A: 1.40 
OD.sub.B &gt; OD.sub.C .gtoreq. OD.sub.A 
B: 0.87 
When pulse width is 5 msec, 
C: 0.82 
OD.sub.B .gtoreq. OD.sub.C &gt; OD.sub.A 
8 When pulse width is 11 msec, 
22.41 
13.67 
- 20.21 
6.31 X X 
A: 1.06 
OD.sub.C &gt; OD.sub.A &gt; OD.sub.B 
B: 0.42 
When pulse width is 5 msec, 
C: 0.82 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
9 When pulse width is 11 msec, 
-1.52 
3.39 
17.65 
-10.62 
X X 
A: 1.06 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
B: 1.23 
When pulse width is 5 msec, 
C: 0.82 
OD.sub.C &gt; OD.sub.A &gt; OD.sub.B 
__________________________________________________________________________ 
TABLE 5 
__________________________________________________________________________ 
(CONTINUED FROM TABLE 3) 
__________________________________________________________________________ 
10 When pulse width is 11 msec, 
5.27 
18.43 
-13.03 
-11.36 
X X 
A: 1.06 
OD.sub.B &gt; OD.sub.A &gt; OD.sub.C 
B: 0.60 
When pulse width is 5 msec, 
C: 0.62 
OD.sub.C &gt; OD.sub.B &gt; OD.sub.A 
11 When pulse width is 11 msec, 
10.86 
-4.31 
-0.75 
1.24 X X 
A: 1.06 
OD.sub.C &gt; OD.sub.B &gt; OD.sub.A 
B: 0.60 
When pulse width is 5 msec, 
C: 1.52 
OD.sub.B &gt; OD.sub.A &gt; OD.sub.C 
12 When pulse width is 11 msec, 
6.35 
-10.35 
1.13 3.87 X X 
A: 0.72 
OD.sub.B &gt; OD.sub.C .gtoreq. OD.sub.A 
B: 0.60 
When pulse width is 5 msec, 
C: 0.82 
OD.sub.A .gtoreq. OD.sub.B &gt; OD.sub.C 
13 When pulse width is 11 msec, 
11.97 
16.34 
-4.50 
-8.91 
A: 1.64 
OD.sub. A &gt; OD.sub.B &gt; OD.sub.C 
B: 0.60 
When pulse width is 5 msec, 
C: 0.82 
OD.sub.B &gt; OD.sub.C &gt; OD.sub.A 
__________________________________________________________________________ 
where the thermal transfer comparisons (OD.sub.A, OD.sub.B, and OD.sub.C) 
represent the reflection densities of step images in thermal head 
recording in accordance with the dye layer inks A, B, and C, respectively. 
TABLE 6 
__________________________________________________________________________ 
EVALUATION BY UP-5000 
Coating Image 1 
Amount 
Comparison of Thermal 
When L* is about 80 
When L* is about 20 
Image 
Image 
No 
(g/m.sup.2) 
Transfer Property 
a* b* a* b* 2 3 
__________________________________________________________________________ 
14 
Same as No. 1 9.21 10.05 
-3.86 
-1.66 
.circleincircle. 
.circleincircle. 
15 
Same as No. 2 7.46 7.90 -7.11 
-5.96 
.circleincircle. 
.circleincircle. 
16 
Same as No. 3 4.03 3.92 -5.14 
-7.31 
.circleincircle. 
.circleincircle. 
17 
Same as No. 8 25.33 
10.68 
-21.28 
6.54 X X 
18 
Same as No. 9 -0.89 
3.21 17.88 
-10.97 
X X 
19 
Same as No. 11 11.53 
-5.14 
-0.45 
1.19 X X 
20 
Same as No. 12 9.04 -10.99 
2.31 3.91 X X 
__________________________________________________________________________ 
Effects of Second Embodiment 
According to the present invention, since the dye layers of the transfer 
sheet are formed so that the light region and the dark region of an image 
formed on an image receiving sheet in accordance with an achromatic color 
supplied to the control unit are printed reddish and greenish 
respectively, medical images with color regions from light orange to light 
red which are easily distinguished can be formed. 
Other Specific Example 
Next, another specific example of the second embodiment will be described. 
In this practical example, dyes and binders which can compose dye layers 
of a thermal transfer sheet, binders which can compose a dye accepting 
layer of an image receiving sheet, and surface lubricants which can 
prevent the thermal transfer sheet and the image receiving sheet from 
thermally adhering each other will be described in detail. These materials 
will be described in the order of (1) dye binder, (2) dye accepting layer 
binder, (3) surface lubricant, and (4) dyes. 
(1) Dye binder 
For example, as the material of the binder of the dye layers, a cellulose 
derivative (such as ethyl cellulose, hydroxyethyl cellulose, 
ethylhydroxyethyl cellulose, methyl cellulose, acetate cellulose, 
acetate-butyrate cellulose, acetate propionic acid cellulose, or nitric 
acid cellulose), a vinyl resin (such as polyvinyl alcohol, polyvinyl 
acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl pyrrolidone, 
polystyrene, or polyvinyl chloride), a polyamide resin, a polyester resin, 
a poly-carbonate resin, an acrylic resin, a polyurethane resin, an 
elastomer, an epoxy resin, a phenoxy resin, a mixture thereof, or a 
copolymerization thereof can be used. 
(2) Dye accepting binder 
For example, as the material of the binder of the dye accepting layer, a 
cellulose derivative (such as ethyl cellulose, hydroxyethyl cellulose, 
ethyl-hydroxyethyl cellulose, methyl cellulose, acetate cellulose, 
acetate-butyrate cellulose, acetate propionic acid cellulose, or nitric 
acid cellulose), a vinyl resin (such as polyvinyl alcohol, polyvinyl 
acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl pyrrolidone, 
polystyrene, or polyvinyl chloride), a polyamide resin, a polyester resin, 
a poly-carbonate resin, an acrylic resin, a polyurethane resin, an 
elastomer, an epoxy resin, a phenoxy resin, a mixture thereof, or a 
copolymerization thereof can be used. 
(3) Surface lubricant 
To prevent the thermal transfer sheet containing the dye layers from 
thermally adhering to the image receiving sheet which accepts dyes, as the 
material of the surface lubricant, an inorganic particle (such as 
colloidal silica or titanium oxide), an organic particle (such as 
polyolefin wax or teflon powder), a higher fatty acid salt, a higher fatty 
acid ester, a surface active agent, a fluororesin, a silicone resin, or 
the like can be disposed in or on the thermal transfer sheet or the image 
receiving sheet. 
(4) Dyes 
For example, as the materials of the dyes, diaryl methane, triaryl methane, 
thiazole, methine (such as merocyanine), azomethine (such as indoaniline, 
acetophenone azomethine, pyrazolone azomethine, imidazole azomethine, 
pyrazolone azomethine, imidazo azomethine, or pyridone azomethine), 
xanthine, oxazine, cyano methylene (such as dicyano styrene or tricyano 
styrene), thiazine, azine, acridine, benzene azo, heterocyclic azo (such 
as pyridone azo, thiophene azo, isothiazole azo, pyrrole azo, pyrazole 
azo, imidazole azo, thiazole azo, triazole azo, or diazo) , spiro-dipyran, 
indolinospiropyran, fluorene, rhodamine lactam, naphthoquimone, 
anthraquinone, quinophthalone, or the like can be used. Practically, the 
following dyes are preferably used. C.I. (Color Index) C.I. 
Disperse yellow: 51, 3, 54, 79, 60, 23, 7, 141, 201, and 261 
Disperse blue: 24, 56, 14, 301, 334, 165, 19, 72, 87, 287 154, 26, and 354 
Disperse red: 135, 146, 59, 1, 73, 60, and 167 
Disperse violet: 4, 13, 26, 36, 56, and 31 
Disperse orange: 149 
Solvent violet: 13 
Solvent black: 3 
Solvent green: 3 
Solvent yellow: 56, 14, 16, and 29 
Solvent blue: 70, 35, 63, 36, 50, 49, 111, 105, 97, and 11 
Solvent red: 135, 81, 18, 25, 19, 23, 24, 143, 146, 182, and the like. 
More specifically, as the materials of the dyes, a methine (cyanine) basic 
dye of mono-methine, di-methine, tri-methine, or the like [such as 
3,3'-diethyloxathiacyanine iodide Astrazone Pink FG (made by Bayer, C.I. 
48015), 2,2' carbocyanine (C.I. 808) , Astraphylloxine FF (C.I. 48070), 
Astrazone Yellow 7GLL (C.I. basic yellow 21), Aizen Kachiron Yellow 3GLH 
(made by Hodogaya Kagaku K. K., C.I. 48055), Aizen Kachiron Red 6BH (C.I. 
48020) or the like]; a di-phenylmethane basic dye [such as auramin (C.I. 
655) ]; a triphenylmethane basic dye [such as Malachite Green (C.I. 
42000), Brilliant Green (C.I. 42040), Magenta (C.I. 42510), Metal Violet 
(C.I. 42535), Crystal Violet (C.I. 42555), Methyl Green (C.I. 684), 
Victoria Blue B (C.I. 44045), or the like]; a xanthene basic dye [such as 
Pyronine G (C.I. 739), Rhodamine B (C.I. 45170), Rhodamine 6G (C.I. 
45160), or the like]; an acridine basic dye [such as Acridine Yellow G 
(C.I. 785), Leonine AL (C.I. 46075), Benzo-Flavin (C.I. 791), Affine (C.I. 
46045) or the like]; a quinoneimine basic dye [such as Neutral Red (C.I. 
50040), Astrazone Blue BGE/.times.125% (C.I. 51005), Methylene Blue (C.I. 
52015), or the like]; or an anthraquinone basic dye having a class four 
ammonium group can be used. 
For example, as the material of the cyan dye, Kayaset Blue 714 (made by 
Nippon Kayaku K. K., solvent blue 63), Foron Brilliant Blue S-R (made by 
Sand K. K., disperse blue 345), or Waxoline AP-FW (made by ICI, solvent 
blue 36) can be selected. For example, as the material of the magenta dye, 
MS-RED G (made by Mitsui Toatsu K. K., disperse red 60), or Macrolex Red 
Violet R (made by Bayer, disperse violet 26) can be used. For example, as 
the material of the yellow dye, Foron Brilliant Yellow S-6GL (made by 
Sand, disperse yellow 231), Macrolex Yellow 6G (made by Bayer, disperse 
yellow 201), or a compound having the following composition can be used. 
##STR1## 
Moreover, the sublimating yellow dyes described in Japanese Patent 
Laid-Open Serial Nos. SHO 59-78895, 60-28451, 60-28453, 60-53564, 
61-148096, 60-239290, 60-31565, 60-30393, 60-53563, 60-27594, 61-262191, 
60-152563, 61-244595, 62-196186, International Laid-Open Serial No. 
W092/05032 can be suitably used. The sublimating magenta dyes described in 
Japanese Patent Laid-Open Serial Nos. SHO 60-223862, 60-28452, 60-51563, 
59-78896, 60-31564, 60-30391, 61-227092, 61-227091, 60-30392, 60-30394, 
60-131293, 61-227093, 60-159091, 61-262190, and U.S. Pat. No. 4,698,651, 
Japanese Patent Application Serial No. SHO 62-220793, and U.S. Pat. No. 
5,079,365 can be suitably used. The sublimating cyan dyes described in 
Japanese Patent Laid-Open Serial Nos. SHO 59-78894, 59-227490, 60-151098, 
59-227493, 61-244594, 59-227948, 60-131292, 60-172591, 60-151097, 
60-131294, 60-217266, 60-31559, 60-53563, 61-255897, 60-239289, 61-22993, 
61-19396, 61-268493, 61-35994, 61-31467, 61-145269, 61-49893, 61-57651, 
60-239291, 60-239292, 61-284489, 62-191191, Japanese Patent Application 
Serial No. SHO 62-176625, and U.S. Pat. No. 5,079,365 can be also suitably 
used. 
Example of more preferable dyes are given by the following structural 
formulas. 
##STR2## 
where 
R1 and R2 are an alkyl group which is substitutable or non-substitutable, a 
cycloalkyl group which is substitutable or non-substitutable, or an 
aralkyl group which is substitutable or non-substitutable; 
R3 is an alkyl group which is substitutable or non-substitutable, an alkoxy 
group which is substitutable or non-substitutable, an alkylcarbonyl-amino 
group which is substitutable or non-substitutable, an alkylsulfonylamino 
group which is substitutable or non-substitutable, an alkylaminocarbonyl 
group which is substitutable or non-substitutable, an alkylaminosulfonyl 
group which is substitutable or non-substitutable, or a halogen atom; 
R4 is an alkoxy-carbonyl group which is substitutable or non-substitutable, 
an alkylaminocarbonyl group which is substitutable or non-substitutable, 
an alkoxy group which is substitutable or non-substitutable, an alkyl 
group which is substitutable or non-substitutable, a cycloalkyl group 
which is substitutable or non-substitutable, a heterocyclic group, or a 
halogen atom; 
R5 is an alkyl group which is substitutable or non-substitutable, an 
alkoxycarbonyl group which is substitutable or non-substitutable, an 
alkylaminocarbonyl group which is substitutable or non-substitutable, an 
alkoxy group which is substitutable or non-substitutable, an 
alkylaminosulfonyl group which is substitutable or non-substitutable, a 
cyano group, a nitro group, or a halogen atom; 
R6 is an alkyl group which is substitutable or non-substitutable, an aryl 
group which is substitutable or non- substitutable, an amino group which 
is substitutable or non-substitutable, a cycloalkyl group which is 
substitutable or non-substitutable, a cyano group, a nitro group, or a 
halogen atom; 
R7 is an alkyl group which is substitutable or non-substitutable, an amino 
group which is substitutable or non-substitutable, an alkoxy group which 
is substitutable or non-substitutable, an alkoxycarbonyl group, or a 
halogen atom; 
R8 is an aryl group which is substitutable or non-substitutable, an 
aromatic heterocyclic group, a cyano group, a nitro group, a halogen atom, 
or an electron attracting group; 
R9 is selected from the group consisting of CONHR.sub.10, SO.sub.2 
NHR.sub.10, NHCOR.sub.11, NHSO.sub.2 R.sub.11, or a halogen atom; 
R10 is an alkyl group which is substitutable or non-substitutable, a 
cycloalkyl group which is substitutable or non-substitutable, an aryl 
group which is substitutable or non-substitutable, or an aromatic 
heterocyclic group which is substitutable or non-substitutable; and 
R11 is an alkyl group which is substitutable or non-substitutable, a 
cycloalkyl group which is substitutable or non-substitutable, an amino 
group which is substitutable or non-substitutable, an aryl group which is 
substitutable or non-substitutable, or an aromatic heterocyclic group 
which is substitutable or non-substitutable. 
These dyes can be used independently or in mixtures thereof. In addition, 
known dyes which are transferred by thermal sublimation, vaporization, or 
dispersion can be added. 
Although the present invention has been shown and described with respect to 
a best mode embodiment thereof, it should be understood by those skilled 
in the art that the foregoing and various other changes, omissions, and 
additions in the form and detail thereof may be made therein without 
departing form the spirit and scope of the present invention.