JP2869949B2 - Thermal transfer sheet and thermal transfer method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermal transfer sheet and a thermal transfer method using a sublimable dye (thermal transfer dye), and more particularly to a transferred image excellent in light resistance and dark fading resistance. It is an object of the present invention to provide a thermal transfer sheet and a thermal transfer method capable of forming the same.

(Prior art and its problems) Conventionally, various thermal transfer methods are known. Among them, a sublimable dye is used as a recording agent, and this is carried on a base sheet such as a polyester film to form a thermal transfer sheet. There have been proposed methods of forming various full-color images on an image receiving sheet having a dye receiving layer formed on a transfer material dyeable with a sublimable dye, for example, paper or plastic film.

In this case, a thermal head of a printer is used as a heating means, and a large number of color dots of three or four colors are transferred to the image receiving sheet by heating for a very short time, and a full-color image of an original is formed by the multicolored dots. That is to reproduce.

The image formed in this way is very clear because the coloring material used is a dye, and is excellent in transparency, so that the obtained image is excellent in the reproducibility and gradation of intermediate colors. And high quality comparable to full-color photographic images.

However, the resulting image is generally inferior to a pigmented image because it is formed from a dye, and has a problem that the image fades or discolors rapidly when exposed to direct sunlight. In the case where direct light is not applied, for example, discoloration (dark fading) even in a room, in a file, or even when binding a book
There is a problem of doing. These problems of light resistance and fading have been alleviated to some extent by adding an ultraviolet absorber or an antioxidant to the dye receiving layer of the image receiving sheet.

However, in the above prior art, the antioxidant and the like are uniformly distributed throughout the dye receiving layer, while the majority of the transferred dye is present near the surface of the receiving layer. There is a problem that the protective action is not performed efficiently and the prevention of discoloration is insufficient, and there is a demand for a technique capable of effectively protecting the transferred dye with an antioxidant or the like.

As a method for solving such a problem, a method of adding an ultraviolet absorber or the like to the dye layer of the thermal transfer sheet instead of the image receiving layer and transferring the ultraviolet absorber or the like to the image forming area simultaneously with the transfer of the dye is proposed in the present invention. The inventor has proposed previously (Japanese Patent Application No. 63
-290101).

However, although this method has a considerable effect, it is not always sufficient for forming a color image in which thermal transfer is performed a plurality of times on the same area of an image receiving sheet. The cause is that, among the multiple transfers, the ultraviolet absorber and the like which are initially transferred simultaneously with the dye penetrate into the dye receiving layer by heating during the subsequent transfer, and an actual image is formed. It was presumed that the density was insufficient on the surface of the image receiving layer.

Therefore, an object of the present invention is to provide a clear image having a sufficient density in a thermal transfer method using a sublimable dye,
Moreover, it is an object of the present invention to provide a thermal transfer sheet and a thermal transfer method in which a formed image exhibits excellent various fastnesses, particularly excellent light fastness and dark fading fastness.

(Means for Solving the Problems) The above object is achieved by the present invention described below. That is,
The present invention comprises three inventions, and the first invention is a heat transfer sheet having a plurality of color dye layers formed on the surface of a base film, and only in the dye layer which is finally transferred among the dye layers or on the surface thereof. A thermal transfer sheet characterized in that only a dye stabilizer is contained.The second invention is directed to a dye layer of the thermal transfer sheet, and an image receiving sheet provided with a dye receiving layer on the surface of a base film. In a thermal transfer method in which a receiving layer is superimposed and heated in the form of an image from the back of a thermal transfer sheet to perform multiple transfers to form a color image, a dye stabilizer is imaged only at the same time as the final transfer. The third invention is a thermal transfer method characterized by transferring to a region, a plurality of monochromatic thermal transfer sheets are sequentially used, and a dye layer of these thermal transfer sheets and a dye receiving layer on the surface of the base film. Image provided Again we are opposed to and over bets receiving layer,
In the thermal transfer method of forming a color image by performing image transfer from the back of the thermal transfer sheet to form an image and performing multiple transfers
A thermal transfer method characterized in that a stabilizer is included only in a dye layer of a thermal transfer sheet to be used last, and a dye stabilizer is transferred to an image forming area only simultaneously with the final transfer.

(Function) When a color image is formed by multiple thermal transfer, a dye stabilizer is included only in the dye layer used last, or a layer containing the stabilizer is formed only on the surface of the dye layer. By transferring these stabilizers to the image forming area only at the same time as the last dye transfer, a color image having excellent light fastness and dark fading fastness can be obtained.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

The thermal transfer sheet of the present invention has a dye film of at least two colors formed on one surface of the base film in a face-sequential manner,
It is characterized in that a dye stabilizer is contained only in the dye layer to be transferred last among them, or a layer of the stabilizer is formed only on the dye layer. For example, when the hue of the dye layer is three layers of yellow, magenta, and cyan, and the thermal transfer is performed in the order of yellow, magenta, and cyan, only the cyan layer contains the stabilizer.

The substrate film used in the present invention may be any one having a conventionally known degree of heat resistance and strength, for example, 0.5 to 50 μm, preferably 3 to 50 μm.
Paper having a thickness of about 10 to 10 μm, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, etc., and particularly preferred is polyester film.

When the substrate film as described above has poor adhesion to the dye layer formed on the surface, it is preferable to apply a primer treatment or a corona discharge treatment to the surface.

For the sublimable (heat transferable) dye layer formed on the base film as described above, at least two colors having different hues are selected from the following dyes, and each dye is coated on the base film with an appropriate binder resin. This is a layer carried on the substrate.

As the dye to be used, any dye conventionally used in a thermal transfer sheet can be effectively used in the present invention, and is not particularly limited. For example, some preferred dyes include MS Red G, Macrolex R as magenta dyes.
ed Violet R, Ceres Red 7B, Samaron Red HBSL, Resol
in Red F3BS, etc., and as a yellow dye, Holon Brilliant Yellow 6GL, PTY-52, Macrolex Yellow 6G, etc., and as a cyan dye, Kayaset Blue 714, Waxolin Blue AP −F
W, Holon Brilliant Blue SR, MS Blue 100 and the like.

As the binder resin for supporting the heat transferable dye as described above, any of conventionally known binder resins can be used, and preferred examples thereof include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose, and acetic acid. Cellulose, cellulose resins such as cellulose acetate butyrate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, vinyl resins such as polyacrylamide, polyester and the like, among these, cellulose,
Polyvinyl acetal, polyvinyl butyral, polyester and the like are particularly preferred.

The stabilizing agent used in the present invention is a chemical agent that can prevent the alteration or decomposition of the dye by absorbing or blocking the action of altering or decomposing the dye, such as light energy, heat energy, oxidizing action, and the like. Antioxidants, ultraviolet absorbers and light stabilizers conventionally known as additives for synthetic resins and the like can be mentioned.

Primary antioxidants such as phenolic, monophenolic, bisphenolic and amine based antioxidants,
Alternatively, sulfur-based, phosphorus-based secondary antioxidants, and the like,
For example, specifically, Sumilizer BBN-S, Sumilizer B
HT, Sumilizer GM, Sumilizer MB, Sumilizer TPP-R
(Manufactured by Sumitomo Chemical Co., Ltd.), Yoshinox 425, Yoshinox SR (manufactured by Yoshitomi Pharmaceutical Co., Ltd.), Irganox-1081, Irgan
It can be obtained from the market under trade names such as ox-1222 (manufactured by Ciba-Geigy) and Mark AO-40 (manufactured by Adeka Argus Chemical Co., Ltd.), and any of them can be used in the present invention.

Examples of the ultraviolet absorber include salicylic acid, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ultraviolet absorbers.
vin P, Tinuvin234, Tinuvin320, Tinuvin326, Tinuvin
327, Tinuvin327 (manufactured by Ciba-Geigy), Sumisorb110,
Sumisorb140 (Sumitomo Chemical Co., Ltd.), Kemisorb1
0, Kemisorb11, Kemisorb12, Kemisorb13 (manufactured by Kemipro Kasei Co., Ltd.), Uvinul X-19, Uvinul Ms-40 (BASF
And Tomisorb 100, Tomizorb 600 (Yoshitomi Pharmaceutical Co., Ltd.), Viosorb-80, Viosorb-90 (Kyodo Yakuhin Co., Ltd.), etc., which can be obtained from the market and used in the present invention. Can be done.

Examples of the light stabilizer include hindered amines and the like, for example, specifically, SANOL LS-770, SANOL LS
-765, SANOL LS-774 (manufactured by Sankyo Co., Ltd.), Sumisorb T
M-061 (manufactured by Sumitomo Chemical Co., Ltd.) is available on the market under trade names, and any of them can be used in the present invention.

The stabilizer as described above preferably has the same thermal transferability (heat transferability) as the sublimable dye, and for example, does not contain a carboxyl group or a sulfonic acid group, and has a molecular weight of
Those having 500 or less are preferable. When the molecular weight exceeds 500, transferability may be insufficient.

As described above, the stabilizer is not included in all the dye layers to be formed, but is added only to the dye layer to be finally transferred at the time of thermal transfer. According to the inventor's research,
Compared to the case where a stabilizer was added to all the dye layers,
Even if the amount of the stabilizer added per layer is the same, almost the same effect is exhibited.
This is very economical because it is reduced to 1/4, and does not cause another problem due to the use of a large amount of a stabilizer, for example, a problem such as dullness of image tone.

The stabilizers can be used alone or as a mixture, and the amount of the stabilizer is preferably in the range of 10 to 100 parts by weight based on 100 parts by weight of the dye. If the amount is too small, the effect of stabilizing the dye is insufficient. If the amount is too large, problems such as a decrease in dye transferability occur, which is not preferable.

The dye layer of the thermal transfer sheet of the present invention is basically formed from the above-mentioned materials, but may also contain various additives as conventionally known, if necessary.

Such a dye layer is preferably formed by adding the above-mentioned sublimable dye, a stabilizer (only the last dye layer), a binder resin and other optional components in an appropriate solvent and dissolving or dispersing each component to form a dye layer. A paint or ink for use is prepared, and this is applied to the above-mentioned base film and dried to form a film.

The dye layer thus formed has a thickness of about 0.2 to 0.5 μm, preferably about 0.4 to 2.0 μm, and the sublimable dye in the dye layer accounts for 5 to 90% by weight, preferably about 90% by weight of the dye layer. Is preferably present in an amount of 10 to 70% by weight.

In another embodiment of the present invention, the dye layer is formed without including the stabilizer in the dye layer in the above-described embodiment, and the stabilizer is formed as a thin film only on the surface of the dye layer to be finally transferred. You can also.

The thin film of the stabilizer may be formed by dissolving the stabilizer as described above in a solvent and coating and drying only on the surface of the dye layer to be transferred last, or The agent is dissolved in a solvent together with the binder, coated and dried only on the surface of the dye layer to be finally transferred to form a stabilizer layer. The usage ratio of the stabilizer and the binder is not particularly limited, but generally, the stabilizer / binder = 1 / weight ratio.
It is about 10 to 10/1. The thickness of the layer to be formed is generally about 0.05 to 10 μm. If it is too thin, the effect of stabilizing the transfer dye is insufficient, and if it is too thick, the transferability of the dye is hindered.

The heat transfer sheet of the present invention as described above may be provided with a heat-resistant layer on the back surface thereof in order to prevent adverse effects due to heat of the thermal head.

The image receiving sheet used to form an image using the thermal transfer sheet as described above may be any image-receiving sheet as long as its recording surface has a dye-accepting property with respect to the dye. In the case of paper, metal, glass, synthetic resin film, sheet or the like having no dye, a dye receiving layer may be formed on at least one surface from a resin having excellent dye receiving property. Such a dye-receiving layer may contain a solid wax such as polyethylene wax, amide wax, or Teflon powder, a fluorine-based or phosphate-based surfactant, silicone oil, or the like as a release agent. preferable.

One embodiment of the thermal transfer method according to the present invention is a method using the thermal transfer sheet according to the present invention. When a color image is formed by performing color transfer multiple times with dye layers of different hues to form a color image, The stabilizer is transferred to the dye transfer area (image forming area) only at the same time as the transfer.

In another embodiment of the thermal transfer method of the present invention, when a color image is formed using a plurality of conventionally known single-color thermal transfer sheets, only the dye layer of the thermal transfer sheet to be finally transferred contains a stabilizer. Use

As means for applying thermal energy at the time of thermal transfer used in the method of the present invention, any conventionally known applying means can be used, for example, recording with a thermal printer (for example, a video printer VY-100 manufactured by Hitachi, Ltd.) or the like. By controlling the recording time by the device, 5 to 10
By applying thermal energy of about 0 mJ / mm ² , the intended purpose can be sufficiently achieved.

(Effects) According to the present invention as described above, when a color image is formed by thermal transfer a plurality of times, a dye stabilizer is included only in the dye layer used last, or the dye layer By forming a layer containing the above stabilizer only on the surface and transferring these stabilizers to the image forming area simultaneously with the transfer of the final dye, a color image having excellent light fastness and dark fading resistance can be obtained. Can be

According to the study of the present inventors, almost the same effect is exhibited even when the amount of the stabilizer added per layer is the same as compared to the case where the stabilizer is added to all the dye layers. In addition to being very economical because the total amount of the stabilizer used is reduced to 1/2 to 1/4, there is another problem caused by using a large amount of the stabilizer, for example, the color tone of an image. No problems such as dullness occur.

(Examples) Next, the present invention will be described more specifically with reference to reference examples, examples, and comparative examples. In the following description, parts and% are based on weight unless otherwise specified.

Reference Example 1 Synthetic paper (Yupo-FRG-150, thickness 15) was used as the base film.
0 μm, manufactured by Oji Oil Chemical Co., Ltd.), and on the other side, a coating solution having the following composition was applied by a bar coater at a rate of 5.0 g / m ² when dried at the rate of 5.0 g / m ² when dried. After drying at 80 ° C. for 5 minutes, a thermal transfer image-receiving sheet was obtained.

Polyester (Byron 600, manufactured by Toyobo) 4.0 parts Vinyl chloride / vinyl acetate copolymer (# 1000A, manufactured by Denki Kagaku Kogyo Co., Ltd.) 6.0 parts Amino-modified silicone (X-22-3050C, manufactured by Shin-Etsu Chemical) 0.2 part Epoxy-modified Silicone (X-22-3000E, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 89.6 parts Reference Example 2 Four color ink compositions for forming a dye layer having the following compositions were prepared.

Yellow (no stabilizer) Disperse dye (Macrolex Yellow 6G, CI Disperse Yello
w201, manufactured by Bayer AG 5.5 parts Polyvinyl butyral resin (ESLEC BX-1, manufactured by Sekisui Chemical) 4.5 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 90.0 parts Magenta (no stabilizer) Disperse dye (Macrolex Red Violet R) , CIDisperse Vi
olet26, manufactured by Bayer) 5.5 parts Polyvinyl butyral resin (S-LEC BX-1, manufactured by Sekisui Chemical) 4.5 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 90.0 parts Cyanide (no stabilizer) Disperse dye (Foron Brilliant blue S) -R, manufactured by Sando Co., Ltd. 3.0 parts Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical) 5.0 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 92.0 parts Black (no stabilizer) Disperse dye (Macrolex Yellow 6G) , CIDisperse Yello
w201, manufactured by Bayer AG 2.5 parts Disperse dye (Macrolex Red Violet R, CIDisperse Vi)
olet26, manufactured by Bayer Corporation 2.5 parts Disperse dye (Foron Brilliant blue SR, manufactured by Sando Corporation) 2.0 parts Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical) 5.0 parts Methyl ethyl ketone / toluene (1/1 by weight) 88.0 Part Yellow (containing stabilizer) Disperse dye (Macrolex Yellow 6G, CIDisperse Yello
w201, manufactured by Bayer AG 5.5 parts UV absorber (Tinuvin P, manufactured by Ciba Geigy) 2.0 parts Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical) 4.5 parts Methyl ethyl ketone / toluene (1/1 by weight) 88.0 parts Magenta ( Disperse dye (Macrolex Red Violet R, CIDisperse Vi)
olet26, Bayer) 5.5 parts UV absorber (Tinuvin P, Ciba-Geigy) 2.0 parts Polyvinyl butyral resin (S-LEC BX-1, Sekisui Chemical) 4.5 parts Methyl ethyl ketone / toluene (1/1 by weight) 88.0 parts Cyan ( Stabilizer included) Disperse dye (Foron Brilliant blue SR, manufactured by Sando Co., Ltd.) 3.0 parts UV absorber (Tinuvin P, manufactured by Ciba Geigy) 2.0 parts Polyvinyl butyral resin (S-LEC BX-1, Sekisui Chemical) 5.0 parts Methyl ethyl ketone / Toluene (weight ratio 1/1) 90.0 parts Black (containing stabilizer) Disperse dye (Macrolex Yellow 6G, CIDisperse Yello
w201, manufactured by Bayer AG 2.5 parts Disperse dye (Macrolex Red Violet R, CIDisperse Vi)
olet26, manufactured by Bayer AG 2.5 parts Disperse dye (Foron Brilliant bulue S-R, manufactured by Sandoz) 2.0 parts UV absorber (Tinuvin P, manufactured by Ciba Geigy) 2.0 parts Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical) 5.0 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 86.0 parts Each of the above inks is heat-treated on the back side, 4.5μ
m thick polyethylene terephthalate film (Lumirror
5AF53, manufactured by Toray Co., Ltd.), dry it immediately with a drier immediately after applying it with a wire bar so that the dry coating amount becomes 1.0 g / m ² , and further dry it in an oven at 80 ° C. for 5 minutes, and then 8 types of thermal transfer I got a sheet.

Example 1 The above-mentioned thermal transfer sheet and thermal transfer image-receiving sheet were overlaid with their respective dye layers and dye-receiving surfaces facing each other, and were subjected to thermal sublimation transfer printer (VY-100, manufactured by Hitachi, Ltd.). In the following transfer order, recording was performed with a thermal head from the back side of the thermal transfer sheet at a printing energy of 90 mJ / mm ² to form a color image, and the results in Table 1 below were obtained.

a: yellow → magenta → cyan → black * b: yellow → magenta → cyan * c: yellow → magenta * d: yellow → cyan * e: magenta → cyan * (* indicates stabilizing agent, unmarked indicates no stabilizing agent Comparative Example 1 A color image was formed in the following printing order in the same manner as in Example 1 and evaluated in the same manner. The results shown in Table 1 below were obtained.

a: Yellow → Magenta → Cyan → Black b: Yellow → Magenta → Cyan c: Yellow → Magenta d: Yellow → Cyan e: Magenta → Cyan (No mark indicates no stabilizer) Comparative Example 2 As in Example 1, A color image was formed in the printing order described above and evaluated in the same manner to obtain the results shown in Table 1 below.

a: yellow * → magenta * → cyan * → black * b: yellow * → magenta * → cyan * c: yellow * → magenta * d: yellow * → cyan * e: magenta * → cyan * (* is a stabilizer Comparative Example 3 A color image was formed in the following printing order in the same manner as in Example 1 and evaluated in the same manner to obtain the results shown in Table 1 below.

a: Yellow * → Magenta * → Cyan * → Black b: Yellow * → Magenta * → Cyan c: Yellow * → Magenta * d: Yellow * → Cyan e: Magenta * → Cyan Example 2 A four-color thermal transfer sheet was prepared using the same amount of an antioxidant (Sumilizer BBM-S) in place of the ultraviolet absorber of the four-color dye ink of Reference Example 2. And Example 1 in combination with the stabilizer-free thermal transfer sheet of Reference Example 2 in the following order.
A color image is formed in the same manner as in
The results in the table were obtained.

a: Yellow → Magenta → Cyan → Black * b: Yellow → Magenta → Cyan * c: Yellow → Magenta * d: Yellow → Cyan * e: Magenta → Cyan * Comparative Example 4 Dark fading properties of the same color images a to e as in Comparative Example 1.

The light fading rate of the print is a fading rate under JIS class 4 irradiation conditions, and the dark fading rate was compared with the fading rate after the recorded image was kept in a dry state at 70 ° C. for 24 hours. Each fade rate is a value calculated by the following equation.

Example 3 In Reference Example 2, a heat transfer sheet of the present invention was obtained by forming a dye layer in the following order on the same base film in the same order as in Example 1, and a color image was formed in the same manner as in Example 1. As a result of the same evaluation, the same effect as in Example 1 was obtained.

a: yellow → magenta → cyan → black * b: yellow → magenta → cyan * c: yellow → cyan * d: magenta → cyan * (* indicates stabilizing agent included, no mark indicates no stabilizing agent) Example 4 In Example 3-b, instead of adding a stabilizer to the cyan dye layer, a cyan dye layer containing no stabilizer was formed, and the following composition was further coated on the surface with a dry coating amount of 1.0 in the same manner. The composition was applied and dried at a rate of g / m ² to obtain a thermal transfer sheet of the present invention. When a color image was formed and evaluated in the same manner as in Example 1, similar results were obtained.

Stabilizer Polyvinyl butyral resin (S-LEC BX-1, manufactured by Sekisui Chemical) 6.0 parts UV absorber (Tinuvin P) 4.0 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 90.0 parts Example 5 Ultraviolet absorption in Example 1 or 2 Sumilizer BHT, SumilizerGM, Sumilizer M
B, Sumilizer TPP-R, Yoshinox 425, Yoshinox SR, Irganox-1081, Irganox-1222, Mark AO-40, T
inuvin234, Tinuvin320, Tinuvin326, Tinuvin327, Tin
uvin327, Sumisorb110, Sumisorb140, Kemisorb10, Kem
i-sorb11, Kemisorb12, Kemisorb13, UvinulX-19, Uv
inul Ms-40, Tomisorb 100, Tomisorb 600, Viosorb
-80, Viosorb-90, SANOL LS-770, SANOL LS-76
5. An image excellent in light resistance and dark fading resistance in the same manner as in Example 1 or 2 except that an antioxidant such as SANOL LS-774 and Sumi-sorb TM-061 and the like, an ultraviolet absorber and a light stabilizer are used. was gotten.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/38-5/40

Claims (4)

(57) [Claims] 1. A thermal transfer sheet having a dye film of a plurality of colors formed on the surface of a substrate film, wherein a dye stabilizer is contained only in the dye layer which is finally transferred among the dye layers or only on the surface thereof. A thermal transfer sheet, characterized in that: 2. The thermal transfer sheet according to claim 1, wherein the stabilizer is an antioxidant having a molecular weight of less than 500, an ultraviolet absorber or a light stabilizer. 3. A thermal transfer sheet according to claim 1, wherein the dye layer of the thermal transfer sheet and a receiving layer of an image receiving sheet provided with a dye receiving layer on the surface of a base film are superposed on each other, and an image is formed from the back side of the thermal transfer sheet. A thermal transfer method in which a color image is formed by performing a plurality of transfers by heating in the same manner as described above, wherein the dye stabilizer is transferred to the image forming area only at the same time as the final transfer. 4. A method of sequentially using a plurality of single-color thermal transfer sheets,
The dye layer of these thermal transfer sheets and the receiving layer of the image receiving sheet provided with the dye receiving layer on the surface of the base film are opposed to each other, and are heated in an image form from the back of the thermal transfer sheet to perform multiple transfers. In the thermal transfer method of forming a color image by performing, a stabilizer is included only in the dye layer of the thermal transfer sheet used last, and the dye stabilizer is transferred to the image forming area only at the same time as the final transfer. Thermal transfer method.