JP2010046850A - Thermosensitive transfer recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive transfer recording medium in which the problem such as surface unevenness and the occurrence of thermal wrinkle is prevented. <P>SOLUTION: The thermosensitive transfer recording medium is provided with a thermosensitive transfer color layer containing at least a sublimation dye and a binder on one surface of a base material film, wherein the binder of the thermosensitive transfer color layer consists of a polymer having hydroxide, the ratio of a hydroxide-containing residue to total residue is <15 wt.%, the intrinsic viscosity of the binder is <0.5 dL/g measured in a mixed solvent containing methylene chloride, 1, 1, 2-trichloro ethane, toluene and ethanol in the ratio by weight of 5:2:2:1, and the thermosensitive transfer color layer contains a polymer having isocyanate as an additive in the range of 0.1-0.4 pts.wt., based on 1 pts.wt. of the binder. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermal transfer recording medium in which a thermal transfer sublimation color material layer containing at least a sublimation dye and a binder is provided on one surface of a substrate film, and more specifically, thermal transfer sublimation color material. The present invention relates to a thermal transfer recording medium in which a layer is uniform without unevenness, and thermal transfer recording is performed without generation of wrinkles or sticking.

  Thermal transfer is a recording in which a part of the thermal transfer layer of the thermal transfer recording medium is transferred to a transfer medium by heating and pressurizing with a thermal recording member on a thermal head or the like to form a desired transfer image on the image receiver. Is the method. As a thermal transfer medium used in this thermal transfer recording, a medium using a sublimation dye as a color material has been particularly widely used in recent years because of excellent gradation expression. A transfer image obtained using such a thermal transfer recording medium is similar to a silver salt photograph in terms of smoothness and density of the gradation, and unlike the silver salt photograph of an optical system, the image to be recorded is digital. Therefore, it is useful as a recording medium for outputting image information related to digital cameras and computer graphics and image information for printing proofreading applications.

  The thermal transfer recording medium using the sublimation dye is obtained by coating a mixture of a sublimation dye and a binder and providing a thermal transfer color material layer on the substrate film. Thermal transfer recording by dye thermal transfer is performed by using the thermal sublimation transfer recording medium thus obtained and transferring a part of the sublimable dye to the image receiving medium using a thermal recording member such as a thermal head.

  On the other hand, in order to obtain the thermal transfer recording as cleanly as possible, the thermal transfer recording medium must be designed so that the thermal transfer recording medium does not wrinkle during transfer and does not stick to the receiver. I must. Usually, when a thermal transfer recording layer is formed by coating a dye or a binder on a film, it is applied by dissolving them in an organic solvent. It is also required to consider this.

As a thermal transfer recording medium used for dye thermal transfer, there is one described in Patent Document 1. In this thermal transfer recording medium, the binder was measured at 25 ° C. in a mixed solvent containing methylene chloride, 1,1,2-trichloroethane, toluene and ethanol at a weight ratio of 5: 2: 2: 1. In this case, by selecting one having a density of 1.6 dL / g or more, the non-uniformity of coating at the time of forming the heat-sensitive transfer color material layer is eliminated, and a good transfer image can be obtained (this book) The intrinsic viscosity as used in the specification has the same meaning as the intrinsic viscosity described in Patent Document 1. In the present specification, what is simply described as “intrinsic viscosity” is methylene chloride, It represents the intrinsic viscosity when measured at 25 ° C. in a mixed solvent containing 1,1,2-trichloroethane, toluene and ethanol in a weight ratio of 5: 2: 2: 1.)
Japanese Patent No. 2703159

However, the following problems occur in thermal transfer recording using the thermal transfer recording medium as described above. That is, the use of a binder having an intrinsic viscosity of 0.5 dl / g or more as the binder results in a high viscosity of the coating solution obtained by dissolving the dye and binder used in forming the heat-sensitive transfer color material layer in an organic solvent. This means that when this coating solution is applied with a gravure roll or the like, a uniform coating film cannot be obtained. More specifically, the coating liquid splashes during gravure coating, and unevenness due to non-uniform coating occurs on the coated surface. This fact is supported by the comparative examples described below.

  If the amount of the organic solvent is increased, the viscosity can be lowered, but in this case, in order to obtain a desired coating amount, a large amount of coating solution must be applied, which is inefficient and impractical. Further, as described in Patent Document 1, the organic solvent used in the coating solution is a mixture of methylene chloride, 1,1,2-trichloroethane, toluene and ethanol, and the thickness of the substrate film to be coated is thick. When the amount of dye used is large, it is considered that the predetermined effect is achieved. However, in consideration of cost and environmental load, a general-purpose organic solvent is used as a solvent, a thin film is used as a base film, and When using as little dye as possible, a thermal transfer recording medium having a desired thermal transfer colorant layer could not be obtained, and a transfer image having a desired image quality could not be obtained.

  In order to solve this problem, it is conceivable to use a binder having a lower intrinsic viscosity. However, it has been found that the following problems occur when a binder having a low intrinsic viscosity is simply used alone. That is, there is a problem that thermal wrinkles are generated on the thermal transfer recording medium due to the heat of the thermal head during thermal transfer, and as a result, an image having a desired quality cannot be obtained. This fact is supported by the comparative examples described below.

  The present invention has been made in view of the above-described situation, and it is possible to optimize the intrinsic viscosity of the binder constituting the heat-sensitive transfer color material layer of the heat-sensitive transfer recording medium and to add a thin base by adding an additive. Even if a thermal transfer recording medium with a low sublimation dye content is used, it is possible to apply and form a uniform thermal transfer color material layer with good processability, and there is no thermal wrinkle during thermal transfer. Another object of the present invention is to provide a thermal transfer recording medium having a performance capable of performing excellent thermal transfer recording.

  In order to achieve this object, the invention according to claim 1 is the thermal transfer color material layer comprising at least a sublimation dye and a binder on one surface of the base film. In the recording medium, the binder of the heat-sensitive transfer color material layer is a polymer having hydroxyl groups, the weight ratio of the hydroxyl group-containing residues to all residues is less than 15%, and the intrinsic viscosity of the binder is 0.00. It is less than 5 dL / g, and the heat-sensitive transfer color material layer contains an isocyanate group polymer as an additive, and the amount is 0.1 to 0.4 weight when the weight part of the binder is 1. This is a thermal transfer recording medium characterized by being in the range of the part.

  According to a second aspect of the present invention, there is provided the thermal transfer recording according to the first aspect, wherein a back coat layer is provided on the surface of the base film on which the thermal transfer color material layer is not provided. It is a medium.

  The invention according to claim 3 is the thermal transfer recording medium according to claim 1 or 2, wherein the substrate film is a plastic film having a thickness of 1 to 20 μm.

  Furthermore, the invention described in claim 4 is the heat-sensitive transfer recording medium according to any one of claims 1 to 3, wherein the dry thickness of the heat-sensitive transfer color material layer is 0.5 to 5 μm. .

  Furthermore, the invention according to claim 5 is the thermal transfer recording medium according to any one of claims 1 to 4, wherein the binder is polyvinyl acetal.

Furthermore, the invention described in claim 6 is the heat-sensitive transfer recording medium according to any one of claims 1 to 5, wherein the heat-sensitive transfer color material layer further contains organic or inorganic fine particles as additives. is there.

  Furthermore, the invention described in claim 7 is the heat-sensitive transfer recording medium according to any one of claims 1 to 6, wherein the heat-sensitive transfer color material layer further contains a surfactant as an additive.

  The heat-sensitive transfer recording medium of the present invention is a heat-sensitive transfer recording medium in which a heat-sensitive transfer color material layer comprising at least a sublimable dye and a binder is provided on one surface of a base film, Since the binder of the layer is a polymer having a hydroxyl group, the weight ratio of the hydroxyl group-containing residues to all residues is less than 15%, and the intrinsic viscosity of the binder is less than 0.5 dL / g, the thermal transfer color Since the material layer has excellent processability, it is possible to form a uniform heat-sensitive transfer color material layer, and the heat-sensitive transfer color material layer contains a polymer having an isocyanate group as an additive. When it is 1, it is in the range of 0.1 to 0.4 parts by weight, so that thermal transfer recording can be performed without generating thermal wrinkles, and transfer images with good image quality can be recorded.

  The present invention will be described below with reference to the drawings. FIG. 1 shows a schematic cross-sectional structure of a thermal transfer recording medium according to the present invention.

  The base film (1) according to the present invention supports the heat-sensitive transfer color material layer (2) and the backcoat layer (3). In the case of the sublimation transfer method, the sublimation transfer layer (2) itself is prevented from being transferred when transferring the sublimation dye in the sublimation transfer layer (2) by the thermal head. It is desirable to consist of the easily bonding layer (12) formed in this.

  The film base (11) has heat resistance that is not softened and deformed by heating with a thermal head. For this reason, a polyester film, specifically, a polyethylene terephthalate film or a polyethylene naphthalate film is desirable. Also, a long film having a thickness of about 1 to 20 μm and a width of 1 to 20 cm is preferable from the viewpoint of thermal conductivity and strength.

  The easy adhesion layer (12) firmly bonds the film base (11) and the sublimation transfer layer (2).

  As will be described later, since the sublimation transfer layer (2) contains polyvinyl acetal or the like as the main component of the binder, the easily adhesive layer (12) is preferably a polyurethane resin composed of a reaction cured product of polyisocyanate and polyol.

  As the polyisocyanate, 2,4 tolylene diisocyanate, 2,6 tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, naphthalene diisocyanate, metaxylylene diisocyanate, vitolylene diisocyanate and the like can be used. Moreover, as a polyol, polyester polyol, polyether polyol, acrylic polyol, etc. can be used.

More specifically, they are polyols such as Nippon Polyurethane Co., Ltd. Nisporan 3110, 3113 and 3115, and polyisocyanates such as Nippon Polyurethane Co., Ltd. Coronate EH. Such polyurethane resins are commercially available under the name of urethane-based paints or urethane-based adhesives.
The easy adhesion layer (12) can be applied and formed by a thin film forming method such as roll coating, reverse coating or gravure coating. The thickness is preferably thinner from the viewpoint of thermal conductivity. For example, the thickness is 5 μm or less. However, in order to maintain the adhesive force, the thickness is desirably 0.1 μm or more.

  On the other hand, as the thermal transfer layer (2) for forming a gradation color image, yellow (Y), magenta (M), and cyan (C) in the longitudinal direction of the base film (1) are used. It is desirable that the heat-sensitive transfer color material layer exhibiting a hue is arranged in the surface order.

  The heat-sensitive transfer color material layer (2) contains at least a dye exhibiting each hue, a binder, and an additive. The dye is a so-called sublimation dye and is sometimes called a vaporizable dye or a heat-melt transfer dye. Usually a disperse dye or an oil-soluble dye. It is necessary to be able to transfer well under the heat generation conditions of the thermal head, for example, 5 to 50 V and several ms. The exothermic temperature is usually 300 to 400 ° C.

  Examples of the dye used in the yellow (Y) heat-sensitive sublimation transfer color material layer (2-Y) include, for example, Kayacet Yellow AG, Kayakut Yellow TDN (manufactured by Nippon Kayaku Co., Ltd.), PTY52, Dianix Yellow 5R-E. , Dianix Yellow F3G-E, Dianix Brilliant Yellow 5G-E (Mitsubishi Chemical Co., Ltd.), DY 108 (Arimoto Chemical Co., Ltd.), Sumikaron Yellow EFG, Sumikaron Yellow E-4GL (above, Examples include FORON Brilliant Yellow S6GLPI (manufactured by Sand), etc.

  Examples of the dye used for the heat-sensitive sublimation transfer coloring material layer (2-M) of magenta (M) include, for example, Kayacet Red 026, Kayacet Red 130, Kayacet Red B (above, Nippon Kayaku Co., Ltd.), Oil Red DR -99, Oil Red DK-99 (Arimoto Chemical Co., Ltd.), Diacelliton Pink B (Mitsubishi Chemical Co., Ltd.), Sumikaron Red E-FBL (Sumitomo Chemical Co., Ltd.), Latyl Red Examples include B (manufactured by du Pont), Sudan Red 7B (manufactured by BASF), Resolin Red FB, and Ceres Red 7B (manufactured by Bayer).

  Examples of the dye used for the cyan (C) heat-sensitive sublimation transfer color material layer (2-C) include, for example, Kaylon Fast Blue FG, Kayacet Blue FR, Kayacet Blue 136, Kayacet Blye 906 (Nippon Kayaku Co., Ltd.) ), Oil Blue 63 (above, manufactured by Arimoto Chemical Co., Ltd.), HSB9 (above, manufactured by Mitsubishi Chemical Corporation), Disperse Blue # 1 (produced by Sumitomo Chemical Co., Ltd.), Ceres Blue GN (manufactured by Bayer) ), DuranoI Brilliant Blue 2G (manufactured by ICI) and the like.

  The binder is for fixing the above-described sublimation transfer dye to the substrate (1), and is a polymer having a hydroxyl group. Examples include acetal, cellulose, polyester, and acrylic polyol polymers.

  Here, the hydroxyl group-containing residue of this polymer is preferably less than 15% of the total weight. As will be described later, since the hydroxyl group reacts with the isocyanate group of the additive, if it is 15% or more, the reaction proceeds too much, and a thermal transfer recording medium having a desired physical property, that is, a dye releasing property upon heating, is in an appropriate range. It is because it cannot be obtained.

  It is necessary that the binder does not adhere to the image receiving body and does not transfer to the image receiving side when performing thermal transfer with a thermal head or the like. For this reason, a resin whose main component is a crosslinked product of polyvinyl alcohol is particularly desirable. For example, polyvinyl acetal and polyvinyl butyral. These resins having a molecular weight of 10,000 to 200,000 can be used. The binder component may be used by mixing not only one type of resin but also a plurality of resins. In order to improve the permeation of the dye at the time of transfer, a small amount of other resins such as ethyl cellulose can be mixed and used.

  In order to improve the thermal responsiveness of the heat-sensitive sublimation transfer color material layer (2), it is desirable that the dye occupies 30 to 70% by weight in the heat-sensitive sublimation transfer color material layer (2). The heat-sensitive sublimation transfer color material layer (2) can be formed by applying a gravure coating method or the like by dissolving or dispersing a dye and a binder in an appropriate solvent. As the solvent, known solvents such as alcohols, ketones, and aromatics can be used. The heat-sensitive sublimation transfer color material layer (2) may be provided in a thickness of about 0.5 to 5 μm depending on the target image density. When forming a layer, if a predetermined thickness cannot be ensured by a single application, the layers may be applied multiple times.

   This heat-sensitive transfer color material layer (2) contains a polymer having an isocyanate group as an additive in addition to the dye and the binder. As the isocyanate group-containing polymer, one having a molecular weight of about 100 to 2,000 can be used. By including both of this additive and the above-mentioned hydroxyl group-containing polymer, it is possible to bring about an effect that good processability, uniform surface shape, and heat wrinkle are not generated during thermal transfer.

  The above effects are manifested in the following two stages. At the time of coating the heat-sensitive transfer layer, which is the first stage, good workability and uniform surface properties can be obtained by using a binder having a low intrinsic viscosity. Here, since the isocyanate group-containing polymer has a very small molecular weight compared to the binder, the viscosity of the coating solution is not affected. In the case where the thermal transfer medium of the second stage is used, that is, at the time of transfer, the binder, which is a polymer having a hydroxyl group, and an isocyanate group are passed through an appropriate drying / aging process after the first stage. The additive, which is a polymer, is reactively polymerized, whereby a heat-sensitive sublimation transfer medium that does not generate heat wrinkles can be obtained.

  This effect can be exhibited well when the base film is a plastic film having a thickness of 1 to 20 μm and the dry thickness of the thermal transfer color material layer is 0.5 to 5 μm. .

  In addition, this effect can be more effectively exhibited when the binder having a hydroxyl group is a polyacetal resin containing a polyvinyl alcohol residue, specifically, polyvinyl acetoacetal or polyvinyl butyral.

  Further, by including inorganic or organic fine particles as an additive in the heat-sensitive transfer color material layer (2), it is possible to prevent sticking between the heat-sensitive transfer color material layer (2) and the image receptor during heat transfer. The fine particles having a size of 0.01 to 1.0 μm can be preferably used.

  In order to improve the releasability of the thermal transfer color material layer (2) and the image receptor during thermal transfer, it is preferable that the thermal transfer color material layer (2) contains a surfactant. Examples of such surfactants include fluorine-based and silicone-based surfactants.

  Furthermore, an antifoaming agent may be included in the coating liquid in order to improve the operability of the coating liquid when the thermal transfer color material layer (2) is formed by printing.

    In the present invention, if necessary, a heat transferable protective layer (not shown) for protecting the transferred image on the image receptor may be provided on the substrate film in the surface order with the heat-sensitive transfer color material layer (2). Good. As a constituent material of this thermal transferable protective layer, cellulose derivatives such as nitrocellulose, ethyl cellulose, cellulose acetate propionate, styrene resins such as polystyrene and poly α-methylstyrene, polymethyl methacrylate, polyethyl acrylate, etc. Acrylic resins, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, vinyl resins such as polyvinyl butyral, polyvinyl acetal, polyester resins, polyamide resins, epoxy resins, polyurethane resins, petroleum resins, ionomers, ethylene Synthetic resins such as acrylic acid copolymer, ethylene-acrylic acid ester copolymer, rosin, rosin modified maleic acid resin, ester gum, polyisobutylene rubber, butyl rubber, styrene butadiene rubber, butadiene acrylo Nitrile rubber, polyamide resins, derivatives of natural resins and synthetic rubber polychlorinated olefins such like. The heat transferable protective layer can be formed of a composition comprising one or more of the above materials.

  In order to improve the peelability of the transferable protective layer as required, a release layer made of a resin that is incompatible with the constituent material of the thermal transferable protective layer or a resin that is incompatible with the base film is used. It may be provided between them. Further, an adhesive layer may be provided on the thermal transfer protective layer in order to improve the adhesion between the image receiving surface of the image receiver and the protective layer. Further, these protective layers and adhesive layers may contain an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, organic / inorganic fine particles, and the like, if necessary.

  When the long thermal transfer recording medium is wound up, the thermal transfer color material layer (2) and the above-described thermal transferable protective layer adhere (block) to the surface of the substrate film on which they are not formed. In addition, the thermal transfer coloring material layer (2) and the thermal transferable protective layer of the base film (1) are formed to prevent the thermal head from adhering to the smooth running of the thermal sublimation transfer medium. It is desirable to provide a backcoat layer (3) on the surface of the base film that has not been formed.

  The backcoat layer (3) is preferably a layer containing a slippery component in order to ensure smooth running of the heat-sensitive sublimation transfer medium. For example, it is a layer containing a metal salt of a phosphate ester, an alkyl phosphate ester, a silicone resin, silicone oil, or the like. The back coat layer (3) is preferably thin, and a thickness of 0.1 to 5 μm is sufficient. The formation may be performed by gravure coating, roll coating, reverse coating or the like.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Table 1 shows the names and characteristics of binders used in this example. In the following examples, the binder names described in Table 1 are used.

<Example 1>
First, 0.5 g / m ² of silicone (manufactured by Shin-Etsu Chemical Co., Ltd.) is applied to the surface of the PET film (thickness: 4.5 μm, manufactured by Toray Industries, Inc.) that has been previously subjected to easy adhesion treatment on one side. Thus, a base film with a back coat layer was obtained.

  Next, on the surface of the base film with the back coat layer obtained as described above, on the surface subjected to the easy adhesion treatment, the following heat-sensitive sublimation transfer color material layer forming use liquid is obtained by a gravure coating method. The coated film was coated to a thickness of 1.5 μm after drying to provide a heat-sensitive sublimation transfer color material layer, and then dried and aged at 120 ° C. for 24 hours to obtain a heat-sensitive transfer recording medium according to Example 1.

<Composition of heat-sensitive sublimation transfer color material layer forming liquid>
Sublimation dye 61 parts by weight Binder A 36 parts by weight Isocyanate group-containing polymer (NCO / OH ratio = 1.8) 8 parts by weight fluorinated surfactant (manufactured by DIC) 1 part by weight organic fine particles (melamine / formaldehyde condensate, granules (Diameter 0.2 μm) 2 parts by weight solvent methyl ethyl ketone 217 parts by weight solvent toluene 109 parts by weight <Example 2>
A heat-sensitive transfer recording medium according to Example 2 for comparison is obtained in the same manner as in Example 1 except that the isocyanate group-containing polymer is excluded from the liquid composition for forming a heat-sensitive sublimation transfer colorant layer in Example 1. It was.

<Example 3>
In the liquid composition for forming a heat-sensitive sublimation transfer color material layer in Example 1, the binder A was replaced with the binder B, and the isocyanate group-containing polymer was removed. 3 was obtained.

<Example 4>
Example for comparison in the same manner as in Example 1 except that the binder A was replaced with the binder C in the liquid composition for forming the heat-sensitive sublimation transfer colorant layer of Example 1 and the isocyanate group-containing polymer was removed. 4 was obtained.

  The intrinsic viscosity of the binder used in Examples 1 to 4 was measured as follows.

<Intrinsic viscosity measurement>
Weight ratio of methylene chloride, 1,1,2-trichloroethane, toluene and ethanol in a constant temperature bath maintained at 25 ° C using an Ostwald viscometer (specification: water 30 ° C, 10 mL, 100 sec (± 20 seconds)) The binder was dissolved in a mixed solvent containing 5: 2: 2: 1, and the intrinsic viscosity was measured. When a plurality of binders were used, the measurement was performed on a mixture of a predetermined amount of binder. The results obtained are shown in Table 1.

  The generation of thermal wrinkles during the transfer of the thermal transfer recording media according to Examples 1 to 4 was evaluated as follows.

<Heat wrinkle evaluation>
The heat-sensitive transfer recording medium was set in a commercially available printer, transferred to a commercially available image receiving paper, and it was confirmed whether the image after the transfer was disturbed by heat wrinkles. Evaluation was evaluated in three stages: ◎: very good, ○: good, ×: bad. The results obtained are shown in Table 2.

  The surface state of the thermal transfer color material layer of the thermal transfer recording media according to Examples 1 to 4 was evaluated as follows.

<Surface condition evaluation>
A portion of the thermal transfer recording medium on which the thermal transfer color material layer is provided is cut out and visually observed with transmitted light. The uniformity of the surface is: ◎: very good, ○: good, ×: bad. Rated by stage. The results obtained are shown in Table 2.

表１は、感熱昇華転写色材層形成用途液に使用したバインダーの呼称と、その性質を記した表である。

Table 1 is a table describing the names and properties of binders used in the heat-sensitive sublimation transfer color material layer forming solution.

表２は、感熱昇華転写色材層形成用途液の組成の概要と、転写画像における熱シワの発生と、感熱転写記録媒体の面状態と、以上を総合した印画後の画像につき、実施例１〜４について記した表である。

Table 2 shows a summary of the composition of the heat-sensitive sublimation transfer color material layer forming liquid, the occurrence of heat wrinkles in the transferred image, the surface state of the heat-sensitive transfer recording medium, and the image after printing, in which the above is combined. It is the table | surface described about ~ 4.

<Evaluation results>
When printing was performed with a thermal head using the obtained thermal transfer recording medium, the generation of thermal wrinkles was remarkable in the case where the additive did not contain an isocyanate group-containing polymer, that is, in Example 2. Moreover, as can be seen in Examples 3 and 4, the higher the intrinsic viscosity of the binder, the less heat wrinkles are generated. Thus, when a binder having an intrinsic viscosity of less than 0.5 is used alone, heat wrinkles are generated. However, in the case where an isocyanate group-containing polymer is included as an additive, that is, in Example 1, generation of heat wrinkles is not observed. However, it was found that the same performance as that obtained when a binder having an intrinsic viscosity of 0.5 or more was used alone was produced.

  In Examples 1 and 2 where the intrinsic viscosity of the binder was less than 0.5, a very good surface state could be obtained. When the intrinsic viscosity of the binder is 0.5 or more, that is, in the heat-sensitive transfer color material layer of the heat-sensitive transfer recording medium according to Examples 3 and 4, the heat-sensitive transfer color material layer forming coating liquid is splashed at the time of application. As a result, a non-uniform surface was considered.

  By combining the above results and evaluating the image after printing, a good image was obtained when the intrinsic viscosity of the binder was less than 0.5 and an isocyanate group-containing polymer was included as an additive. In the case where the intrinsic viscosity was 0.5 or more or no additive was used even when the viscosity was 0.5 or less, surface unevenness, heat wrinkles, and image deterioration due to sticking were observed.

It is explanatory drawing which shows the general | schematic cross-section structure of the thermal transfer recording medium used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base film 11 Film base 12 Easy-adhesion layer 2 Thermal transfer color material layer 3 Backcoat layer

Claims (7)

  A thermal transfer recording medium provided with a thermal transfer color material layer containing at least a sublimable dye and a binder on one surface of a substrate film, wherein the binder of the thermal transfer color material layer has a hydroxyl group The weight ratio of the hydroxyl group-containing residues to the total residues is less than 15%, and the intrinsic viscosity of the binder is methylene chloride, 1,1,2-trichloroethane, toluene and ethanol in a weight ratio of 5: 2: In the mixed solvent containing 2: 1, when measured at 25 ° C., the thermal transfer colorant layer contains a polymer having an isocyanate group as an additive, and the amount is A heat-sensitive transfer recording medium, wherein the binder is in the range of 0.1 to 0.4 parts by weight when the weight part of the binder is 1.   2. The thermal transfer recording medium according to claim 1, wherein a backcoat layer is provided on the surface of the base film on which the thermal transfer color material layer is not provided.   3. The thermal transfer recording medium according to claim 1, wherein the base film is a plastic film having a thickness of 1 to 20 [mu] m.   4. The thermal transfer recording medium according to claim 1, wherein the dry thickness of the thermal transfer color material layer is 0.5 to 5 [mu] m.   The thermal transfer recording medium according to any one of claims 1 to 4, wherein the binder is polyvinyl acetal.   6. The thermal transfer recording medium according to claim 1, wherein the thermal transfer color material layer further contains organic or inorganic fine particles as an additive.   The thermal transfer recording medium according to claim 1, wherein the thermal transfer color material layer further contains a surfactant as an additive.

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