JPH0729504B2 - Thermal transfer sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal transfer sheet, and more particularly, to obtain an image on a thermal transfer sheet by performing thermal printing according to image information with a thermal head or a laser. It relates to a suitable thermal transfer sheet.

(Prior Art and Problems Thereof) In order to obtain an image according to image information by a thermal head, a laser, or the like, a thermosensitive coloring paper has been mainly used conventionally. In this heat-sensitive color-developing paper, a colorless or monochromatic leuco dye provided on a base paper and a developer are brought into contact with each other by heating to obtain a color-developed image. As such a color developer, a phenolic compound, a zinc salicylate derivative, rosin and the like are generally used. However, the above-mentioned thermosensitive color paper has a fatal defect that the obtained color image is erased when stored for a long period of time, and the color printing is limited to two colors and continuous gradation is provided. It was not possible to obtain the color image that it had.

On the other hand, in recent years, thermosensitive coloring paper in which a heat-melting wax layer having a pigment dispersed therein is provided on a base paper has started to be used. When the heat-sensitive color-developing paper and the transfer-receiving paper are superposed and heat printing is performed from the back of the heat-sensitive color-developing paper, the wax layer containing the pigment is transferred onto the transfer-receiving paper to obtain an image. According to such a printing method, a durable image can be obtained, and a multicolor image can be obtained by printing a plurality of times using a thermosensitive coloring paper containing pigments of three primary colors. It is not possible to obtain an image like a photograph having continuous gradation.

By the way, in recent years, there has been an increasing demand for directly obtaining an image such as a color photograph from an electric signal, and various attempts have been made. One of such attempts is a method of transferring an image onto a CRT and photographing it with a silver salt film, but when the silver salt film is an instant film, there is a drawback that the running cost increases, and When the silver salt film is a 35 mm film, there is a disadvantage that it is not immediate because development processing is required after photography. As another method, an impact ribbon method or an inkjet method has been proposed, but the former has a drawback that the image quality is poor, and the latter requires image processing, so it is difficult to easily obtain an image like a photograph. There is a drawback that.

In order to eliminate such a defect, a thermal transfer sheet provided with a sublimable disperse dye layer having a property of being transferred by heating is used in combination with a heat transferable sheet, and the sublimable disperse dye is controlled on the heat transferable sheet. A method has been proposed in which the image is transferred to obtain an image like a photograph having gradation (The Institute of Image Electronics Engineers of Japan, Volume 12, No. 1 (1983)). According to this method, an image requiring continuous gradation can be obtained from a television signal by a simple process, and a device used at that time is not complicated, and therefore, the method is attracting attention.

As one of the conventional techniques close to such a method, there is a dry transfer printing method of polyester fiber. In this dry transfer printing method, a dye such as a sublimable disperse dye is dispersed or dissolved in a synthetic resin solution to form a dye, and the dye is applied in a pattern on thin paper or the like and dried to form a heat transfer sheet. Is a method for obtaining an image by superimposing and closely adhering the polyester fiber, which is a thermal transfer sheet, on the sheet.

However, it is difficult to obtain a high-density colored image even if the conventionally used thermal transfer sheet is used as it is for the dry transfer printing method of polyester fiber and heated and printed by a thermal head or the like. The main reason is that the thermal sensitivity of the thermal transfer sheet is not high.

Among these disadvantages, those caused by the heat transferable sheet have a glass transition temperature of −100 ° C. to 20 ° C. and island portions independent of each other made of a synthetic resin having a polar group.
It was found that the thermal transfer sheet (Japanese Patent Application No. 58-135627) having a thermal transfer layer formed in a sea-island shape with a sea portion made of a synthetic resin having a glass transition of 40 ° C. or higher is found to be solved. However, the cause of the heat transfer sheet side has not been solved yet.

This is, for example, in the conventional printing method for textiles, for example, 200
Dye transfer / dyeing is achieved by heating at ℃ for 1 minute, while heating by the thermal head is about 40
The reason is that it is as short as several msec. At 0 ° C.

The present inventors use it in combination with a heat-transferable sheet, particularly the heat-transferable sheet described in the above-mentioned Japanese Patent Application No. 58-135627, in order to obtain a color photographic image by heating and printing with a thermal head or the like. As a result of various researches to obtain a heat transfer sheet suitable for, a disperse dye is economically used in a conventionally generally used heat transfer sheet even if it is initially dissolved or finely dispersed in a binder. Dye aggregation, crystal growth, and precipitation occur, and in order to heat the dye molecules in such a state to sublimate, the interaction within the dye aggregate or crystal is broken, and the heat exceeding the interaction with the binder resin is used. Energy must be applied to the dye molecules to sublimate and dye the heat-transferred sheet, which requires high energy, resulting in low thermal sensitivity of the heat-transfer sheet and deposition on the surface. Although the transfer member is contaminated proved by the dye.

Therefore, the object of the present invention is to solve the problems of the prior art,
A thermal transfer sheet capable of obtaining a high-sensitivity and high-density color-developed image when printed by heating with a thermal head or the like and which does not contaminate a transfer target.

(Means for Solving Problems) The above object is achieved by the present invention described below. That is, the present invention is a thermal transfer sheet for forming an image on a transfer object by applying thermal energy according to image information so as to be superposed on the transfer object, and transferred onto a plastic film by heating. The thermal transfer layer is formed in a state in which the dye to be transferred to the transfer body is dissolved in the binder resin that does not transfer when the thermal energy is applied, and the binder resin has (a) a molecular weight of 60,000 to 200,000 (b) glass transition (C) A thermal transfer sheet characterized by containing 90% by weight or more of a polyvinyl butyral resin in which the weight% of the vinyl alcohol portion is 10% to 40%.

(Function) In the past, since the dye in the thermal transfer layer was dispersed in the binder resin in the form of particles, it is sufficient to break each interaction between the dye and the binder resin and between the dye molecules in the crystal. Needed energy.

However, in the present invention, since the dye in the thermal transfer layer is dissolved in the binder resin, energy for breaking the interaction between the dye molecules in the crystal is unnecessary,
Energy sufficient to break the interaction between the dye and the binder resin is sufficient, and transfer can be performed with less energy than in the case of using a conventional thermal transfer sheet.

(Preferred Embodiment) As shown in FIG. 1, the thermal transfer sheet 1 of the present invention is basically a basic sheet 2 on which a thermal transfer layer 3 is provided.

The material of the basic sheet 2 is preferably paper such as condenser paper or plastic film such as polyester film, polystyrene film, polysulfone film, polyimide film, polyvinyl alcohol film or cellophane.

Of these materials, when importance is attached to price and heat resistance in an untreated state, condenser paper is used. On the other hand, it is preferable to use a polyester film when it is important to have mechanical strength, high rupture strength during handling during preparation of a thermal transfer sheet and running in a thermal printer, and smooth surface. . The thickness of the base sheet 2 is 3 to 50 μm, preferably 3
~ 15 μm.

The thermal transfer layer 3 is composed of a binder resin containing a dye that is transferred by heat and transferred to a transfer target in a binder resin. The thickness of the thermal transfer layer 3 is 0.5 to 5.0 μm, preferably 0.5 to 2.0 μm.

The dye contained in the thermal transfer layer is more preferably a disperse dye, which has a small molecular weight of about 150 to 400, and has a thermal sublimation temperature, hue, weather resistance, stability in ink and binder resin. Is selected in consideration of, and specifically, the following are exemplified.

CI Disperse Yellow 42 (Mitsui Toatsu, Miketone Polyester Yellow, -YL), CI Disperse Yellow 5 (Mitsui Toatsu, Miketone Polyester Yellow-5)
G), CI Solvent Yellow 77 (Nippon Kayaku, Kayaset Yellow G), CI Solvent Yellow 125 (S)
(Nippon Kayaku, Kayaset Yellow A-N), CI Disperse Yellow 14-1 (Mitsubishi Kasei PTY-52), C.I.
I. Disperse Yellow 3 (Mitsubishi Chemical, PTY-56),
CI Disperse Red 111 (Mitsui Toatsu, Miketone Polyester Red-BSF), CI Disperse Red 228
(S) (Mitsui Toatsu Press, Miketone Polyester Red-T3
B), CI Disperse Red 135 (Nippon Kayaku, Kayaset Red B), CI Disperse Red 4 (Nippon Kayaku, Kayaset Red 126), CI Disperse Red 5
0 (Mitsubishi Kasei, PTR-54), CI Disperse Red 60
(Made by Mitsubishi Kasei, PTR-63), CI Disperse Blue 56
(Mitsui Toatsu Press, Miketone Polyester Blue-FBL),
CI Disperse Blue 106 (Mitsui Toatsu, Discharge Blue R), CI Solvent Blue 33 (Mitsui Toatsu, Mitsui PS Blue 3R), CI Disperse Blue 241
(Mitsubishi Kasei, PTB-67), CI Solvent Blue 90
(Mitsubishi Kasei, PTB-77), CI Solvent Blue 112
(Nippon Kayaku, Kayaset Blue 906), CI Solvent Blue 114 (S) (Nippon Kayaku, Kayaset Blue 14)
1), CI Solvent Blue 63 (Nippon Kayaku, Kayaset Blue 714), CI Disperse Violet 26 (Bayer, Macrolex Red Violet R), C.
I. Solvent Red 19 (Made by Bayer, Seres Red 7
B), CI Disperse Red 60 (manufactured by Mitsui Toatsu, MS Red G) The ratio of the dye contained in the thermal transfer layer depends on the sublimation temperature of the dye and the covering power (color rendering) in the colored state. Is usually 5 to 70%, preferably about 10 to 60%.

A polyvinyl butyral resin is used as the binder resin that constitutes the thermal transfer layer 3, and its molecular weight is 60,000 or more in the sense of producing a binding force as a binder, and it is necessary to make the viscosity at the time of application appropriate. Further, it is preferably 200,000 or less. Further, the glass transition temperature (Tg) is 60 ° C. or higher, more preferably 70 ° C. or higher in order to prevent dye aggregation, crystal growth, and precipitation in the thermal transfer layer 3, and from the viewpoint of facilitating dye sublimation. It is below 110 ℃. Further, in order to improve the affinity with the dye due to hydrogen bonding or the like, the weight% of the vinyl alcohol portion is 10% to 40%, preferably 15 to 30% in the polyvinyl butyral resin.

If the weight% of the vinyl alcohol portion is less than 10%, the thermal transfer layer will not have sufficient stability over time, and dye aggregation, precipitation and bleeding on the surface will be observed. If it exceeds 40%, there will be too many affinity portions. When printing with a thermal head or the like, the dye is not released from the thermal transfer amount and the printing density becomes low.

In order to improve the drying property when the thermal transfer layer is formed by coating, the binder resin may be replaced with a cellulose resin up to 10% of the weight of the binder resin. Examples of such preferable cellulose-based resin include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, nitrocellulose and the like.

In order to provide the thermal transfer layer 3 on the base sheet 2, a dye and a binder resin may be dissolved together with a solvent to prepare an ink composition for forming a thermal transfer layer, which may be applied and dried by an appropriate printing method or application method. If desired, any additive may be added to the thermal transfer layer forming ink composition.

The basic configuration of the thermal transfer sheet of the present invention is as described above, but by a contact type heating means such as a thermal head,
When the surface of the base sheet 2 is directly heated, as shown in FIG. 2, a slip layer 4 containing a lubricant such as wax or a release agent is provided on the side of the base sheet 2 where the thermal transfer layer is not provided. As a result, it is possible to prevent fusion between the heating means such as a thermal head and the base sheet and to improve the sliding.

The shape of the thermal transfer sheet of the present invention may be in the form of a single sheet cut to a required size, may be continuous or wound, and may be narrow tape. .

As a method for providing the thermal transfer layer 3 on the base sheet 2, the surface of the base sheet 2 may be entirely coated with the ink composition for the thermal transfer layer containing the same coloring material, but it may be different depending on the case. A plurality of thermal transfer ink compositions each containing a color material may be formed on different areas of the surface of the base sheet 2.

For example, as shown in FIG. 3, a black thermal transfer layer 5 and a red thermal transfer layer 6 may be manufactured by stacking the black thermal transfer layer 5 and the red thermal transfer layer 6 in parallel on the base sheet 2, or as shown in FIG. As shown, the thermal transfer sheet may be manufactured by repeatedly providing the yellow thermal transfer layer 7, the red thermal transfer layer 8, the blue thermal transfer layer 9, and the black thermal transfer layer 10 on the base sheet 2.

When a plurality of thermal transfer layers having different hues are provided on the thermal transfer sheet in this manner, there is an advantage that a multicolor image can be obtained by simply using one thermal transfer sheet.

The thermal transfer sheet may be provided with a registration mark or the like for forming perforations or detecting the positions of areas having different hues, so that it can be conveniently used.

The thermal transfer sheet prepared as described above includes the thermal transfer sheet, for example, the thermal transfer layer 3 of the thermal transfer sheet 1 as shown in FIG. 5, and the image receiving layer 13 on the base sheet 12 of the thermal transfer sheet.
The dyes in the thermal transfer layer are transferred to the image receiving layer by applying the heat energy corresponding to the image information to the interface between the thermal transfer layer and the image receiving layer so that they are in contact with each other.

As a heat source that gives thermal energy, the thermal head 14
In addition to the above, known materials such as laser light, infrared flash, and hot pen can be used.

The thermal energy may be applied from the thermal transfer sheet side, from the thermal transfer sheet side or from both sides, but from the viewpoint of effective utilization of thermal energy, the thermal transfer sheet side is preferred.

However, in order to express the gradation of light and shade of the image, it is easy to control the heat energy to be applied or the color material is promoted to diffuse on the heat-transferred sheet to express the continuous gradation of the image. From the viewpoint of ensuring the reliability, it is preferable to apply heat energy from the heat transfer target sheet side.

Further, by applying the heat energy from both sides, both advantages described above can be enjoyed at the same time.

When a thermal head is used as a heat source for applying thermal energy, the applied thermal energy can be changed continuously or in multiple steps by modulating the voltage or pulse width applied to the thermal head.

When laser light is used as a heat source for giving heat energy, the heat energy to be given can be changed by changing the light amount of the laser light or the irradiation area.
If a dot generator with a built-in acousto-optic element is used, it is possible to give heat energy according to the size of the halftone dot.

When using a laser beam, it is advisable to bring the thermal transfer sheet and the thermal transfer sheet into close contact with each other. Also, in order to improve the absorption of the laser beam on the surface irradiated with the laser beam,
For example, it may be colored black.

If a non-sublimable substance that absorbs laser light and converts it into heat is added to the thermal transfer layer 3, the heat transfer to the dye is performed more efficiently and the resolution is increased.

When an infrared flash lamp is used as a heat source for providing heat energy, it may be performed in the same manner as when using a laser beam, or a pattern that continuously expresses the shade of an image such as black, or by using a halftone dot pattern. You may perform it via the pattern of. Alternatively, in connection with the latter, the colored layer of one surface such as black may be combined with a negative pattern of any one of the above patterns.

When thermal energy is applied to the interface between the thermal transfer layer and the image receiving layer as described above, the dye in the thermal transfer layer thermally transfers to the image receiving layer 13 in an amount according to the applied thermal energy and is received to form an image. To do.

The image obtained in this manner is a monochromatic image, but thermal transfer sheets of different colors, for example, yellow, red, indigo and black if necessary, the thermal transfer sheets of each color are sequentially replaced to perform thermal transfer. It is also possible to obtain an image that looks like a color photograph that is a combination of them.

Further, when forming an image such as a color photograph, instead of sequentially replacing the thermal transfer sheets of each color as described above and performing thermal transfer, as shown in FIG. Thermal transfer sheet is prepared, for example, first the yellow color separation image is thermally transferred using the yellow area of the heat transfer sheet, and then the red color separation image is thermally transferred using the red area of the same thermal transfer sheet. If the method of thermally transferring each color separation image of yellow, red, indigo, and black if necessary by repeating the same operation for indigo and black in sequence, the thermal transfer sheet is not replaced. It is possible to form a color image like a color photograph.

The quality of the obtained image can be improved by appropriately adjusting the size of the heat source used to apply the heat energy, the adhesion between the heat transfer sheet and the heat transfer target sheet, and the heat energy.

The thermal transfer sheet of the present invention, when combined with a thermal transfer sheet, can be used for printing using various thermal printing printers, facsimiles, photographic prints by magnetic recording, or prints on a television screen.

For example, one screen of the received television is stored in a storage medium such as a magnetic tape or a magnetic disk as a signal of each color separation pattern of yellow, red, indigo, and black if necessary, and each stored screen is stored. A signal of a color separation pattern is output, and heat energy corresponding to the output signal is applied to the superposed body of the thermal transfer sheet and the thermal transfer sheet by the above-mentioned heat source such as a thermal head, and thermal printing is sequentially performed for each color. As a result, the screen of the television can be reproduced as a sheet-like print.

When a combination of the heat-transferable sheet and the heat-transferable sheet of the present invention is used for printout of a television screen, a white image-receiving layer alone or a colorless and transparent image-receiving layer is usually used as the heat-transferable sheet. It is convenient to obtain a reflection image when a backing material with a base material such as paper or a white image-receiving layer backing with a base material such as paper is used.

In addition to the above, the thermal transfer sheet of the present invention can be used in combination with characters, figures, symbols, colors and the like formed on a CRT screen by operating a computer to use a graphic pattern or the like as an original image. Original picture is picture element, photograph,
When the image is a fixed image such as a printed matter or an actual object such as a person, a living thing, or a landscape, the same operation can be performed by using an appropriate means such as a video camera as an intermediary. When extracting the signals of each color separation pattern from the original image, an electronic plate making machine (color scanner) used for photolithography of printing may be used.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 As a base sheet, a thickness of 9 μ having corona treatment on one side
m PET film (Toyobo Co., Ltd., S-PET) was coated with the ink composition for forming a thermal transfer layer having the following composition by wire bar coating so that the dry thickness was 1.0 g / m ^2, and then dried. After dropping a drop of silicone oil (X-41 ・ 4003A made by Shin-Etsu Silicone) on the back of it,
It was spread on the entire surface and subjected to a back surface treatment to obtain a thermal transfer sheet of the present invention.

Ink composition for thermal transfer layer Disperse dye (Nippon Kayaku, Kayaset Blue 714) 4 parts by weight Polyvinyl butyral resin (Sekisui Chemical, S-LEC BX-
1) 4.3 parts by weight Toluene 40 parts by weight Methyl ethyl ketone 40 parts by weight Isobutanol 10 parts by weight Here, the polyvinyl butyral resin (BX-1) has a molecular weight of about 100,000, a Tg of 83 ° C, and a weight% of the vinyl alcohol part.
Is about 20% by weight. The resulting thermal transfer layer is transparent,
No particles were observed under a microscope (magnification)
400).

Next, a synthetic paper (YUPO-FPG 150, manufactured by Oji Yuka Co., Ltd.) having a thickness of 150 μm was prepared as a base sheet, and an ink composition for an image receiving layer having the following composition was dried by a wire bar coating method to give a dry thickness of 5 g / After coating so as to be m ² , it was dried to obtain a heat transfer sheet. The temperature is 10 after drying the dryer temporarily.
It was carried out in an oven at 0 ° C. for 1 hour to sufficiently evaporate the solvent.

Ink composition for image receiving layer Polyester resin (Toyobo, Byron 103) 8 parts by weight EVA polymer plasticizer (Mitsui Polychemical, Elvalloy 7)
41) 2 parts by weight amino-modified silicone oil (Shin-Etsu Silicone, KF-
393) 0.125 parts by weight Epoxy-modified silicone oil (Shin-Etsu Silicone, X
-22-343) 0.125 parts by weight Toluene 70 parts by weight Methyl ethyl ketone 10 parts by weight Cyclohexanone 20 parts by weight The thermal transfer sheet and the thermal transfer transfer sheet obtained as described above are stacked so that the thermal transfer layer and the image receiving layer are in contact with each other, and thermal transfer is performed. Output of the thermal head from the base sheet side of the sheet by the thermal head; 1W / 1 dot, pulse width; 0.3-4.5msec,
Dot density: As a result of recording under the condition of 3 dots / mm,
The reflection density of the high-density coloring part with a pulse width of 4.5 msec. Is 1.65,
The reflection density of the low-density color-developed portion with a pulse width of 0.3 msec. Was 0.16, and recording with gradation according to the applied energy was obtained (measuring machine; Macbeth densitometer RD-918).

Also, when printing with a thermal head and peeling off the heat transfer sheet and the heat transfer target sheet, no transfer of the resin of the heat transfer layer onto the image receiving layer was observed, and scumming of the non-heated portion also occurred. There wasn't.

Furthermore, even if the same thermal transfer sheet was left in an oven at a temperature of 60 ° C. for 30 days in a wound state, no apparent change or deterioration in recording performance was observed, and the practicability was demonstrated.

Example 2 A thermal transfer sheet of the present invention was produced in the same manner as in Example 1 except that the polyvinyl butyral resin in the thermal transfer ink composition was changed from BX-1 to Denka Butyral 5000-A (manufactured by Denki Kagaku). .

Denka Butyral 5000-A has a molecular weight of approximately 130,000 and a Tg of approximately
At 78 ° C, the weight% of the vinyl alcohol part is about 16% by weight. The resulting thermal transfer layer was also transparent and no particulate matter was observed.

When the obtained thermal transfer sheet was combined with the same thermal transfer sheet as used in Example 1 and recorded under the same conditions as in Example 1, the reflection density of the high density color-developed portion having a pulse width of 4.5 msec. Was 1.70, The reaction density of the low-density color-developed portion with a pulse width of 0.3 msec was 0.17.

In addition, neither the background stain of the non-heated portion nor the transfer of the resin which occurs when the both sheets are peeled off occurred. Furthermore, when a heating acceleration test was performed under the same conditions as in Example 1, no change was observed.

Example 3 A thermal transfer sheet of the present invention was produced in the same manner as in Example 1 except that the polyvinyl butyral resin in the thermal transfer ink composition was changed from BX-1 to Denka Butyral 6000-C (manufactured by Denki Kagaku). .

Denka Butyral 6000-C has a molecular weight of about 155,000, Tg
About 90 ° C, the weight% of the vinyl alcohol part is about 16% by weight.

When the obtained thermal transfer sheet was combined with the same thermal transfer sheet as used in Example 1 and recorded under the same conditions as in Example 1, the reflection density of the high density color-developed portion having a pulse width of 4.5 msec. Was 1.60, The reflection density of the low-density color-developed portion with a pulse width of 0.3 msec. Was 0.10. In addition, the results of other aging tests were also good.

Example 4 A thermal transfer sheet of the present invention was produced in the same manner as in Example 1 except that the polyvinyl butyral resin in the ink composition for the thermal transfer layer was changed from BX-1 to Denka Butyral 4000-1 (manufactured by Denki Kagaku). did.

Denka Butyral 4000-1 has a molecular weight of about 60,000 and a Tg of about
At 80 ° C, the weight% of the vinyl alcohol part is about 20% by weight.

When the obtained thermal transfer sheet was combined with the same thermal transfer sheet as used in Example 1 and recorded under the same conditions as in Example 1, the reflection density of the high-density color-developed portion having a pulse width of 4,5 msec. Was 1.90. The reflection density of the low-density color-developed portion with a pulse width of 0.3 msec. Was 0.17.

In addition, the results of other aging tests were also good.

Example 5 The thermal transfer sheet of the present invention was prepared in the same manner as in Example 1 except that the following ink composition for the thermal transfer layer was used and applied onto a substrate sheet so that the dry thickness would be 1.0 g / m ^2. And

Ink composition for thermal transfer layer Disperse dye (Nippon Kayaku, Kayaset Blue 714) 4 parts by weight Polyvinyl butyral resin (Sekisui Chemical, S-LEC BX
-1) 4 parts by weight Ethyl cellulose (Hercules, EC N-14) 0.3
Parts by weight Toluene 40 parts by weight Methyl ethyl ketone 40 parts by weight Isobutanol 10 parts by weight Using the resulting thermal transfer sheet, recording was carried out in the same manner as in Example 1, and the same recording performance as in Example 1 was obtained, and There was no problem in stability over time.

Comparative Example 1 A thermal transfer sheet of Comparative Example was prepared by using the following ink composition for a thermal transfer layer and applying it to S-PET having a thickness of 9 μm so that the dry thickness was 1.0 g / m ² . .

Ink composition for thermal transfer layer Disperse dye (Nippon Kayaku, Kayaset Blue 714) 4.0 parts by weight Polyvinyl butyral resin (Sekisui Chemical, S-LEC BM
-2) 4.3 parts by weight Toluene 40 parts by weight Methyl ethyl ketone 40 parts by weight Isobutanol 10 parts by weight Here, S-LEC BM-2 has a molecular weight of about 50,000 and a Tg of 62.
This resin is about 21% by weight of vinyl alcohol part at ℃. When this thermal transfer sheet was allowed to stand at room temperature for about 10 hours, deposition of dye was observed on the surface of the thermal transfer layer, and when printing was performed on the transferred layer with a thermal head, recording with high color density was obtained. Soil was also generated, which was not practical.

Comparative Example 2 The binder in Comparative Example 1 was changed from BM-2 to Denka Butyral 3000-K (manufactured by Denki Kagaku), and the dry coating amount was 1.1 g.
A thermal transfer sheet was produced in the same manner as in Comparative Example 1 except that m ² was used.

Decanty butyral 3000-K has a molecular weight of about 57,000, a Tg of about 80 ° C., and a weight percentage of the vinyl alcohol portion of 9%.

When the obtained thermal transfer sheet was combined with the same thermal transfer sheet as used in Example 1 and recorded under the same conditions as in Example 1, the color density of the portion having a pulse width of 4.5 msec.
A high density recording of 2.04 was obtained, but this thermal transfer sheet
When it was put in an oven at 60 ° C for 20 hours to perform a time-acceleration test, the dye was deposited on the surface of the thermal transfer layer, and when printing was performed using the thermal transfer sheet in the deposited state, scumming was observed in the non-recorded area. The thermal transfer sheet was insufficient.

Comparative Example 3 A thermal transfer sheet was prepared in the same manner as in Example 1 except that S-LEC BL-1 (manufactured by Sekisui Chemical Co., Ltd.) was used instead of the binder in Comparative Example 1, and at the time of drying with a dryer, Aggregation occurred. This phenomenon could not be prevented even if the solvent in the ink was changed to dioxane or cyclohexanone, which has a high dye solubility and a high boiling point. The S-LEC BL-1 used here has a molecular weight of about 15,000 and a Tg of about 5
At 8 ° C, the weight% of the vinyl alcohol part is 25%.

Comparative Example 4 The following was used as the ink composition for the thermal transfer layer, and this ink was applied to the same base sheet as in Example 1 by the wire bar coating method so that the thickness when dried was 1.0 g / m ^2. It was dried to obtain a heat transfer sheet.

Ink composition for thermal transfer layer Disperse dye (Nippon Kayaku, Kayaset Blue 714) 4.0 parts by weight Ethyl hydroxyethyl cellulose (Hercules,
EHEC-Low) 4.3 parts by weight Toluene 40 parts by weight Methyl ethyl ketone 40 parts by weight Isobutanol 10 parts by weight The above thermal transfer sheet was combined with the same thermal transfer transfer sheet as used in Example 1 and recorded under the same conditions as in Example 1. However, the reflection densities of the respective pulse width portions of 4.5 msec. And 0.3 msec. Were 1.85 and 0.17, respectively. When this thermal transfer sheet was put in an oven at 60 ° C for 20 hours and subjected to a time-dependent acceleration test, a dye was deposited on the surface of the thermal transfer layer, and printing was performed using the thermal transfer sheet in the deposited state. It was recognized and the stability was insufficient.

Example 6 An ink composition for a thermal transfer layer having the following composition was prepared, and a coating film was formed on the same film as in Example 1 by a wire bar coating method so that the coating amount when dried was 0.6 g / m ^2. To obtain the thermal transfer sheet of the present invention.

When printing was performed using this thermal transfer sheet under the same conditions as in Example 1, recordings were obtained with reflection densities of 1.54 and 0.08 at pulse widths of 4.5 msec. And 0.3 msec., Respectively.

Ink composition for thermal transfer layer Disperse dye (Mitsubishi Kasei, PTY-52) 1.2 parts by weight Polyvinyl butyral resin (Sekisui Chemical, S-LEC BX
-1) 4.2 parts by weight Ethyl cellulose (Hercules, EC N-14) 0.3
Parts by weight Toluene 40 parts by weight Methyl ethyl ketone 40 parts by weight Isobutanol 10 parts by weight When observed under a microscope, no particles were observed in the thermal transfer sheet, and the dye was in a dissolved state (400 magnification). Further, when this thermal transfer sheet was put in an oven at a temperature of 60 ° C. and an accelerated test was conducted, no abnormalities were observed even after two months, and similar printing was possible.

Example 7 An ink composition for a thermal transfer layer having the following composition was prepared, and a coating film was formed on the same film as in Example 1 by a wire bar coating method so that the coating amount when dried was 1.0 g / m ^2. To obtain the thermal transfer sheet of the present invention.

When printing was performed using this thermal transfer sheet under the same conditions as in Example 1, recording was obtained with reflection densities of 1.60 and 0.12. At pulse widths of 4.5 msec. And 0.3 msec., Respectively.

Ink composition for thermal transfer layer Disperse dye (Mitsui Toatsu Chemicals, Red-G) 2.5 parts by weight Polyvinyl butyral resin (Sekisui Chemical, S-LEC BX
-1) 4.4 parts by weight Toluene 40 parts by weight Methyl ethyl ketone 40 parts by weight Isobutanol 10 parts by weight No graininess was observed in the thermal transfer sheet when observed under a microscope, and the thermal transfer sheet was heated at a temperature of 60 ° C. When an accelerated test was carried out by placing it in an oven, no abnormalities were observed even after two months, and similar printing was possible.

(Effect) In the present invention, since the dye in the thermal transfer layer is dissolved in the binder resin, energy for breaking the interaction between the dye molecules in the crystal is unnecessary, so that the interaction between the dye and the binder resin is not necessary. Energy enough to break the action is sufficient, and transfer can be performed with less energy than in the case of using a conventional thermal transfer sheet.

[Brief description of drawings]

1 to 4 show an embodiment of a thermal transfer sheet according to the present invention. FIGS. 1 and 2 are sectional views, FIGS. 3 and 4 are perspective views, and FIG. 5 is a book. It is explanatory drawing which illustrates the method of transferring using the thermal transfer sheet of invention. 1: Thermal transfer sheet 2: Substrate sheet 3: Thermal transfer layer 11: Thermal transfer sheet 12: Substrate sheet 13: Image receiving layer 14: Thermal head 15: Plantain roll

Claims (2)

[Claims] 1. A thermal transfer sheet for forming an image on a transfer target by applying thermal energy according to image information to the transfer target so as to transfer the transfer onto a plastic film by heating. The thermal transfer layer is formed in a state in which the dye to be transferred to the body is dissolved in the binder resin that does not transfer when the thermal energy is applied, and the binder resin has (a) a molecular weight of 60,000 to 200,000 (b) a glass transition temperature. 60 ° C. to 110 ° C. (c) A thermal transfer sheet containing 90% by weight or more of a polyvinyl butyral resin in which the weight% of the vinyl alcohol portion is 10% to 40%. 2. The thermal transfer sheet according to claim 1, wherein each of the yellow, red, indigo and, if necessary, black thermal transfer layers is separately formed on the base sheet.