JP5664387B2 - Thermal transfer recording medium - Google Patents

Description

  The present invention relates to a thermal transfer recording medium used in a thermal transfer type printer, and is provided with a heat-resistant slipping layer on one surface of a substrate, and an undercoat layer and a dye layer on the other surface of the substrate. Are sequentially formed. More specifically, the present invention relates to a thermal transfer recording medium that has high transfer sensitivity during high-speed printing, that is, can reduce the amount of dye used in the dye layer, and can prevent abnormal transfer in printing even in a low temperature and low humidity environment. is there.

  In general, a thermal transfer recording medium is an ink ribbon called a thermal ribbon, which is used in a thermal transfer type printer, and has a thermal transfer layer on one side of the substrate and heat resistance on the other side of the substrate. A slipping layer (back coat layer) is provided. Here, the thermal transfer layer is a layer of ink that is sublimated (sublimation transfer method) or melted (melt transfer method) by the heat generated in the thermal head of the printer, and transferred to the transfer target side. It is.

  Currently, among the thermal transfer systems, the sublimation transfer system can easily form full-color images with various functions of the printer, so digital camera self-prints, cards such as identification cards, amusement output, etc. Widely used. Along with the diversification of such applications, there is a growing demand for smaller size, higher speed, lower cost, and durability for the obtained printed material. A thermal transfer recording medium having a plurality of thermal transfer layers provided so as not to overlap a protective layer imparting durability has been widely used.

  Under such circumstances, along with the diversification and widespread use of applications, there has arisen a problem that sufficient print density cannot be obtained with the conventional thermal transfer recording medium as the printing speed of the printer further increases. In order to increase the transfer sensitivity, attempts have been made to improve the transfer sensitivity in printing by reducing the thickness of the thermal transfer recording medium. However, wrinkles due to heat, pressure, etc. may occur during the manufacture of the thermal transfer recording medium or during printing. Or a breakage in some cases.

  In addition, attempts have been made to increase the printing density and transfer sensitivity in printing by increasing the dye / resin (Dye / Binder) ratio in the dye layer of the thermal transfer recording medium. In addition to being up, a part of the dye migrates to the heat-resistant slipping layer of the thermal transfer recording medium during the winding state in the manufacturing process (setback), and when the rewinding is performed, the migrated dye has another color. When the dye layer or the protective layer is re-transferred (backside back) and the contaminated layer is thermally transferred to the transfer target, the hue becomes different from the designated color, or so-called scumming occurs.

  Attempts have also been made to increase the energy at the time of image formation on the printer side, not on the thermal transfer recording medium side, but not only the power consumption increases, but also the life of the thermal head of the printer is shortened. And the material to be transferred are fused, so that so-called abnormal transfer is likely to occur. On the other hand, when a large amount of a release agent is added to the dye layer or the transfer target in order to prevent abnormal transfer, blurring of the image or background staining may occur.

  In order to solve such a problem, several methods have been proposed. For example, Patent Document 1 proposes a thermal transfer sheet having an adhesive layer made of a polyvinyl alcohol resin and a polyvinyl pyrrolidone resin between a base material and a dye layer.

  Patent Document 2 proposes a thermal transfer sheet having an adhesive layer containing a polyvinylpyrrolidone resin and a modified polyvinylpyrrolidone resin between a base material and a dye layer.

  Patent Document 3 proposes a thermal transfer sheet having an adhesive layer composed of a polyvinyl pyrrolidone resin or polyvinyl alcohol resin thermoplastic resin and colloidal inorganic pigment ultrafine particles between a base material and a dye layer.

  Patent Document 4 proposes a thermal transfer sheet having a base layer composed of a copolymer of vinylpyrrolidone and vinyl acetate and colloidal inorganic pigment ultrafine particles between a substrate and a dye layer.

  Patent Document 5 and Patent Document 6 propose thermal transfer sheets in which the heat resistance of the dye layer is increased by adding isocyanate to the resin of the dye layer and reacting them individually.

  Patent Document 7 and Patent Document 8 propose thermal transfer sheets that use acid-modified polyvinyl acetal resin as the resin of the dye layer.

JP-A-5-131760 JP-A-2005-231354 JP 2006-150956 A JP 2008-155612 A JP 61-106296 A JP 2010-260928 A JP 2006-69196 A JP 2010-228415 A

  However, the techniques proposed in Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 satisfy the printing sensitivity when printing is performed with a high-speed printer using a sublimation transfer method on a thermal transfer recording medium. When the ratio is increased to the ratio of dye / resin (Dye / Binder), abnormal transfer has been confirmed in a low temperature and low humidity environment.

  Further, in the techniques proposed in Patent Document 5 and Patent Document 6, when the same image is printed on the thermal transfer recording medium, if the undercoat layer is not provided, the transfer sensitivity in the print is low and sufficient. The level was not reached.

  Further, in the techniques proposed in Patent Document 7 and Patent Document 8, when the same image is printed on the thermal transfer recording medium, if the undercoat layer is not provided, the transfer sensitivity in the print is increased, but it is sufficient. However, abnormal transfer has also been confirmed when no curing agent is added.

  As described above, none of the prior arts has found a thermal transfer recording medium that is compatible with a high-speed printer that has high transfer sensitivity in printing and does not cause abnormal transfer even in a low temperature and low humidity environment. .

  Therefore, in view of the above problems, the present invention has high transfer sensitivity during high-speed printing, i.e., can reduce the amount of dye used in the dye layer, and can perform abnormal transfer in printing even in low-temperature and low-humidity environments. It is an object of the present invention to provide a thermal transfer recording medium that can be prevented.

  The invention according to claim 1 is the thermal transfer recording medium in which a heat-resistant slipping layer is provided on one surface of the substrate, and an undercoat layer and a dye layer are provided in this order on the other surface of the substrate. The layer contains at least polyvinyl alcohol and polyvinyl pyrrolidone, the ratio of the polyvinyl alcohol in the undercoat layer is 50% or more by weight, and the binder resin constituting the dye layer is at least an acid-modified polyvinyl acetoacetal resin And a curing agent that reacts with the binder resin is added to the dye layer.

  The invention according to claim 2 is the thermal transfer recording medium according to claim 1, wherein the blending ratio of the polyvinyl alcohol and the polyvinyl pyrrolidone is (polyvinyl alcohol) / (polyvinyl pyrrolidone) = 7 / on a weight basis. It is 3 to 5/5.

  According to a third aspect of the present invention, in the thermal transfer recording medium according to the first or second aspect, the curing agent is an isocyanate compound.

The invention according to claim 4 is the thermal transfer recording medium of claim 1, wherein the coating amount after drying of the undercoat layer is, 0.05 g / ^{m 2} or more 0.30 g / ^{m 2} or less of It is within the range.

  The invention according to claim 5 is the thermal transfer recording medium according to claims 2 to 4, wherein a release agent comprising at least two kinds of modified silicone oils is added to the dye layer, and one modified silicone oil is A side-chain polyether-modified non-reactive silicone oil having a molecular weight of 8000 or more, and the other modified silicone oil is a side-chain diamine-modified reactive silicone oil having a molecular weight of 3000 or less. .

  According to the heat-sensitive transfer recording medium of the present invention, the transfer sensitivity is high during high-speed printing, the amount of dye used in the dye layer can be reduced, and abnormal transfer in printing can be prevented even under low-temperature and low-humidity environments. Can be obtained.

1 is a side sectional view showing a thermal transfer recording medium according to an embodiment of the present invention.

  Hereinafter, thermal transfer recording media according to embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a thermal transfer recording medium according to an embodiment of the present invention, and a heat-resistant slipping layer 40 is provided on one surface of a substrate 10 to provide slipperiness with a thermal head. An undercoat layer 20 and a dye layer 30 containing at least polyvinyl alcohol and polyvinyl pyrrolidone are sequentially formed on the other surface of the substrate 10.

  Since the base material 10 is required to have heat resistance and strength not to be softened and deformed by heat pressure in thermal transfer, for example, polyethylene terephthalate, polyethylene naphthalate, polypropylene, cellophane, acetate, polycarbonate, polysulfone, polyimide, polyvinyl alcohol, aromatic It is possible to use a film of a synthetic resin such as an aromatic polyamide, aramid, or polystyrene, and a paper such as a condenser paper or paraffin paper, alone or in combination. Among these, a polyethylene terephthalate film is preferable in view of physical properties, workability, cost, and the like.

  The thickness can be in the range of 2 μm to 50 μm in consideration of operability and workability, but in consideration of handling properties such as transfer suitability and workability, it is about 2 μm to 9 μm. Those are preferred.

  Further, the base material 10 can be subjected to an adhesion treatment on the surface on which the heat resistant slipping layer 40 and / or the undercoat layer 20 is formed. As the adhesion treatment, known techniques such as corona treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, roughening treatment, plasma treatment, primer treatment, etc. can be applied, and these treatments are used in combination. You can also In the present invention, it is effective to improve the adhesion between the substrate and the undercoat layer, and it is preferable to use a primer-treated polyethylene terephthalate film from the viewpoint of cost.

The heat-resistant slipping layer 40 can be handled by a conventionally known layer. For example, a resin serving as a binder, a functional additive that imparts releasability and slipperiness, a filler, a curing agent, a solvent, and the like are blended to provide heat resistance. A coating solution for forming a slipping layer can be prepared, applied and dried. The coating amount after drying of the heat resistant slipping layer 40 is suitably about 0.1 g / m ² or more and 2.0 g / m ² or less. Here, the coating amount after drying of the heat resistant slipping layer 40 means the amount of solid content remaining after applying and drying the coating solution for forming the heat resistant slipping layer, and after drying the undercoat layer 20 described later. Similarly, the coating amount of the dye layer 30 and the coating amount after the drying of the dye layer 30 indicate the solid amount remaining after the coating liquid is applied and dried.

  As an example of the heat-resistant slip layer 40, the binder resin may be polyvinyl butyral resin, polyvinyl acetoacetal resin, polyester resin, vinyl chloride-vinyl acetate copolymer, polyether resin, polybutadiene resin, acrylic polyol, polyurethane acrylate. , Polyester acrylate, polyether acrylate, epoxy acrylate, nitrocellulose resin, cellulose acetate resin, polyamide resin, polyimide resin, polyamideimide resin, polycarbonate resin and the like.

  Functional additives include natural waxes such as animal waxes and plant waxes, synthetic hydrocarbon waxes, aliphatic alcohols and acid waxes, fatty acid esters and glycerite waxes, synthetic ketone waxes, amine and amide waxes Synthetic waxes such as chlorinated hydrocarbon waxes and alpha-olefin waxes, higher fatty acid esters such as butyl stearate and ethyl oleate, sodium stearate, zinc stearate, calcium stearate, potassium stearate, magnesium stearate, etc. Surfactants such as higher fatty acid metal salts, long chain alkyl phosphate esters, polyoxyalkylene alkyl aryl ether phosphate esters or phosphate esters such as polyoxyalkylene alkyl ether phosphate esters, etc. Rukoto can.

  As fillers, talc, silica, magnesium oxide, zinc oxide, calcium carbonate, magnesium carbonate, kaolin, clay, silicone particles, polyethylene resin particles, polypropylene resin particles, polystyrene resin particles, polymethyl methacrylate resin particles, polyurethane resin particles, etc. Can be mentioned.

  Examples of the curing agent include isocyanates such as tolylene diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, and derivatives thereof, but are not particularly limited.

  The undercoat layer 20 includes at least polyvinyl alcohol and polyvinyl pyrrolidone, and is formed by blending polyvinyl alcohol and polyvinyl pyrrolidone to prepare a coating solution for forming an undercoat layer, and applying and drying.

  In the undercoat layer 20, polyvinyl alcohol and polyvinyl pyrrolidone are essential components, and it is particularly preferable that polyvinyl alcohol and polyvinyl pyrrolidone are the main components of the undercoat layer (20).

  Here, the main component means that, in addition to polyvinyl alcohol and polyvinyl pyrrolidone, other components may be added unless the effect of the present invention is impaired, and the total of polyvinyl alcohol and polyvinyl pyrrolidone is Although it means that it is contained in an amount of more than 50% by mass as viewed from the whole when the undercoat layer is formed, it is preferably 80% by mass or more.

  Polyvinyl alcohol is generally obtained by saponifying polyvinyl acetate, from so-called partially saponified polyvinyl alcohol in which several tens of percent of acetate groups remain, to so-called fully saponified polyvinyl alcohol in which only several percent of acetate groups remain. There is no particular limitation.

  The blending ratio of polyvinyl alcohol and polyvinyl pyrrolidone is preferably (polyvinyl alcohol) / (polyvinyl pyrrolidone) = 5/5 to 7/3 on a mass basis. By satisfying this range, it is possible to obtain a printed material that has a higher transfer sensitivity during high-speed printing, and that does not cause abnormal transfer during printing in a low-temperature and low-humidity environment.

  In addition, the undercoat layer 20 may contain known additives such as an isocyanate compound, a silane coupling agent, a dispersant, a viscosity modifier, and a stabilizer as long as the performance is not impaired.

Here, the coating amount after drying of the undercoat layer 20, but are not unconditionally limited, it is preferably in the range of 0.05 g / ^{m 2} or more 0.30 g / ^{m 2} or less. If it is less than 0.05 g / m ² , the transfer sensitivity at the time of high-speed printing is insufficient due to deterioration at the time of laminating the dye layer, and there is a concern that the adhesion to the substrate or the dye layer may be problematic. On the other hand, if it exceeds 0.30 g / m ² , the sensitivity of the thermal transfer recording medium itself is affected, and there is a fear that the transfer sensitivity at the time of high-speed printing is insufficient.

The dye layer 30 can be a conventionally known one. For example, the dye layer 30 is formed by blending a heat-transferable dye, a binder, a curing agent, a solvent, and the like to prepare a coating liquid for forming a dye layer, and applying and drying the coating liquid. Is done. An appropriate coating amount of the dye layer 30 after drying is about 1.0 g / m ² . The dye layer can be composed of a single layer of one color, or a plurality of dye layers containing dyes having different hues can be repeatedly formed on the same surface of the same substrate in the surface order.

  The heat transferable dye of the dye layer 30 is not particularly limited as long as it is a dye that melts, diffuses, or sublimates and transfers due to heat. For example, as yellow components, solvent yellow 56, 16, 30, 93, 33, Disperse Yellow 201, 231, 33 and the like. Examples of the magenta component include C.I. I. Disperse thread 60, C.I. I. Disperse violet 26, C.I. I. Solvent Red 27, or C.I. I. Solvent Red 19 etc. can be mentioned. As the cyan component, C.I. I. Disperse Blue 354, C.I. I. Solvent Blue 63, C.I. I. Solvent Blue 36, or C.I. I. Disperse Blue 24 and the like. As a black ink dye, it is common to perform color matching by combining the above dyes.

  It is essential for the binder contained in the dye layer 30 to contain an acid-modified polyvinyl acetoacetal resin.

  In the binder contained in the dye layer 30, the acid-modified polyvinyl acetoacetal resin is an essential component, and in particular, the acid-modified polyvinyl acetoacetal resin is preferably the main component of the binder contained in the dye layer 30.

  Here, the main component means that, in addition to the acid-modified polyvinyl acetoacetal resin, in addition to the acid-modified polyvinyl acetoacetal resin, other components may be added. Although it means that it is contained in an amount exceeding 50% by mass in view of the whole binder contained in the dye layer 30, it is preferably 80% by mass or more. As a resin to be added to the binder contained in the dye layer 30, any conventionally known resin binder can be used, and is not particularly limited. However, ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, Examples include cellulose resins such as methyl cellulose and cellulose acetate, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, and polyacrylamide, polyester resins, styrene-acrylonitrile copolymer resins, and phenoxy resins. Can do.

  Examples of the curing agent contained in the dye layer 30 include dialdehydes, phenol resins, epoxy resins, and melamine resins in addition to isocyanates, such as tolylene diisocyanate, triphenylmethane triisocyanate, and tetramethylxylene diisocyanate. Isocyanates and derivatives thereof are particularly preferred in terms of reactivity with the acid-modified polyvinyl acetoacetal resin.

  Here, the blending ratio of the dye of the dye layer 30 to the binder + curing agent is preferably (dye) / (binder + curing agent) = 10/100 to 300/100 on a mass basis. This is because when the ratio of (dye) / (binder + curing agent) is less than 10/100, the amount of dye is too small and the color development sensitivity becomes insufficient, and a good thermal transfer image cannot be obtained. If the ratio exceeds / 100, the solubility of the dye in the binder is extremely lowered, so that when it becomes a thermal transfer recording medium, the storage stability is deteriorated and the dye is likely to precipitate. The dye layer may contain known additives such as a silane coupling agent, a dispersant, a viscosity modifier, and a stabilizer as long as the performance is not impaired.

  The heat-resistant slip layer 40, the undercoat layer 20, and the dye layer 30 can be formed by applying and drying by a conventionally known application method. Examples of the application method include a gravure coating method, a screen printing method, a spray coating method, and a reverse roll coating method.

  In the following, Examples 1 to 6 and Comparative Examples 1 to 5 are produced and compared as specific examples according to the present invention. In the text, “part” is based on mass unless otherwise specified.

<Preparation of substrate with heat-resistant slip layer>
As a base material, use a polyethylene terephthalate film with 4.5 μm single-sided easy-adhesion treatment, and apply a heat-resistant slipping layer coating solution of the following composition to the non-adhesive-treated surface by gravure coating method, After apply | coating so that it might be set to 1.0 g / m < ² > and drying at 100 degreeC for 1 minute, the base material with a heat-resistant slipping layer was obtained by aging for 1 week in a 40 degreeC environment.

<Heat resistant slipping layer coating solution>
Acrylic polyol resin 12.5 parts Polyoxyalkylene alkyl ether / phosphate ester 2.5 parts Talc 6.0 parts 2,6-tolylene diisocyanate prepolymer 4.0 parts Toluene 50.0 parts Methyl ethyl ketone 20.0 parts Ethyl acetate 5.0 parts (Example 1)
The undercoat layer coating solution-1 having the following composition was applied to the easy-adhesion treated surface of the substrate with a heat-resistant slip layer by a gravure coating method so that the coating amount after drying was 0.20 g / m ² . The undercoat layer was formed by drying at 100 ° C. for 2 minutes. Subsequently, a dye layer coating solution having the following composition is applied on the undercoat layer by a gravure coating method so that the coating amount after drying is 0.70 g / m ² and dried at 90 ° C. for 1 minute. Thus, a dye layer was formed, and the thermal transfer recording medium of Example 1 was obtained.

<Undercoat layer coating solution-1>
Polyvinylpyrrolidone 2.5 parts Polyvinyl alcohol 2.5 parts Pure water 76.0 parts Isopropyl alcohol 19.0 parts <Dye layer coating solution-1>
C. I. Solvent Blue 63 5.0 parts Acid-modified polyvinyl acetoacetal resin 4.0 parts 2,6-tolylene diisocyanate prepolymer 1.0 part Toluene 44.9 parts Methyl ethyl ketone 44.9 parts Side chain diamine-modified silicone oil 0.1 Parts (molecular weight 1500)
Side chain polyether-modified silicone oil 0.1 parts (molecular weight 10,000)
(Example 2)
In the thermal transfer recording medium produced in Example 1, the thermal recording transfer medium of Example 2 was obtained in the same manner as in Example 1 except that the undercoat layer was changed to the undercoat layer coating liquid-2 of the following composition. .

<Undercoat layer coating solution-2>
Polyvinylpyrrolidone 1.5 parts Polyvinyl alcohol 3.5 parts Pure water 76.0 parts Isopropyl alcohol 19.0 parts (Example 3)
The thermal recording transfer medium of Example 3 was obtained in the same manner as in Example 1 except that the dye layer was changed to the dye layer coating liquid-2 having the following composition in the thermal transfer recording medium produced in Example 1.

<Dye layer coating solution-2>
C. I. Solvent Blue 63 5.0 parts Acid-modified polyvinyl acetoacetal resin 4.0 parts 2,6-tolylene diisocyanate prepolymer 1.0 part Toluene 44.9 parts Methyl ethyl ketone 44.9 parts Side chain diamine-modified silicone oil 0.2 (Example 4)
In the thermal transfer recording medium produced in Example 1, the thermal recording transfer medium of Example 4 was obtained in the same manner as in Example 1 except that the undercoat layer was changed to the undercoat layer coating solution-3 of the following composition. .

<Undercoat layer coating solution-3>
Polyvinylpyrrolidone 1.0 part Polyvinyl alcohol 4.0 part Pure water 76.0 parts Isopropyl alcohol 19.0 parts (Example 5)
In the heat-sensitive transfer recording medium produced in Example 1, the Example was carried out in the same manner as in Example 1 except that the undercoat layer was applied and dried so that the coating amount after drying was 0.03 g / m ^2. No. 5 thermal recording transfer medium was obtained.

(Example 6)
In the heat-sensitive transfer recording medium produced in Example 1, the Example was applied in the same manner as in Example 1 except that the undercoat layer was applied and dried so that the coating amount after drying was 0.35 g / m ^2. No. 6 thermal recording transfer medium was obtained.

(Comparative Example 1)
After forming the undercoat layer on the easy-adhesion treated surface of the substrate with a heat-resistant slipping layer, the same dye layer coating solution as in Example 1 is dried on the easy-adhesive treated surface by a gravure coating method. The coating amount was 0.70 g / m ² and dried at 90 ° C. for 1 minute to form a dye layer, whereby the thermal transfer recording medium of Comparative Example 1 was obtained.

(Comparative Example 2)
In the thermal transfer recording medium produced in Example 1, the thermal recording transfer medium of Comparative Example 2 was obtained in the same manner as in Example 1 except that the undercoating layer was changed to the undercoating layer coating solution-4 of the following composition. .

<Undercoat layer coating solution-4>
Polyvinylpyrrolidone 5.0 parts Pure water 76.0 parts Isopropyl alcohol 19.0 parts (Comparative Example 3)
A thermal recording transfer medium of Comparative Example 3 was obtained in the same manner as in Example 1 except that the thermal transfer recording medium produced in Example 1 was changed to Dye Layer Coating Liquid-3 having the following composition.

<Dye layer coating solution-3>
C. I. Solvent Blue 63 5.0 parts Polyvinyl acetoacetal resin 4.0 parts 2,6-tolylene diisocyanate prepolymer 1.0 part Toluene 44.9 parts Methyl ethyl ketone 44.9 parts Side chain diamine-modified silicone oil 0.1 parts ( Molecular weight 1500)
Side chain polyether-modified silicone oil 0.1 parts (molecular weight 10,000)
(Comparative Example 4)
A thermal recording transfer medium of Comparative Example 4 was obtained in the same manner as in Example 1, except that the thermal transfer recording medium produced in Example 1 was changed to the dye coating solution-4 having the following composition.

<Dye layer coating solution-4>
C. I. Solvent Blue 63 5.0 parts Acid-modified polyvinyl acetoacetal resin 5.0 parts Toluene 44.9 parts Methyl ethyl ketone 44.9 parts Side chain diamine-modified silicone oil 0.1 parts (Molecular weight 1500)
Side chain polyether-modified silicone oil 0.1 parts (molecular weight 10,000)
(Comparative Example 5)
In the thermal transfer recording medium produced in Example 1, the thermal recording transfer medium of Comparative Example 5 was obtained in the same manner as in Example 1 except that the undercoat layer was changed to the undercoat layer coating solution-5 of the following composition. .

<Undercoat layer coating solution-5>
Polyvinylpyrrolidone 3.0 parts Polyvinyl alcohol 2.0 parts Pure water 76.0 parts Isopropyl alcohol 19.0 parts <Preparation of transferred object>
As a base material, a white foamed polyethylene terephthalate film of 188 μm is used, and an image-receiving layer coating solution having the following composition is applied to one surface thereof by a gravure coating method so that the coating amount after drying is 5.0 g / m ^2. By applying and drying, a transfer object for thermal transfer was produced.

<Image-receiving layer coating solution>
Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 19.5 parts Amino-modified silicone oil 0.5 part Toluene 40.0 parts Methyl ethyl ketone 40.0 parts <Evaluation of adhesion of dye layer at room temperature>
With respect to the thermal transfer recording media of Examples 1 to 6 and Comparative Examples 1 to 5, a cellophane tape having a width of 18 mm and a length of 150 mm was pasted on the dye layer of the thermal transfer recording medium stored at room temperature, and immediately thereafter. Table 1 shows the results of evaluation by examining the presence or absence of the dye layer adhering to the cellophane tape when peeled off.
The evaluation was performed 10 times, and the number of sheets was recorded based on the following criteria.
○: Adhesion of the dye layer is not recognized Δ: Adhesion of the dye layer is very slightly observed ×: Adhesion of the dye layer is recognized on the entire surface X is not possible when one or more or four or more are Δ judge.

<Dye layer print evaluation under low temperature and low humidity>
For the thermal transfer recording media of Examples 1 to 6 and Comparative Examples 1 to 5, using the thermal transfer recording medium and the transfer target that were further stored in an environment of 15 ° C. and 20% RH for 24 hours, Table 1 shows the results of printing and evaluating the maximum reflection density, the presence or absence of abnormal transfer, and the printing sound. The maximum reflection density is a value measured with X-Rite 528.
The printing conditions are as follows.

Printing environment: 23 ° C, 50% RH
Applied voltage: 29V
Line cycle: 0.7msec
Print density: main scanning 300 dpi sub-scanning 300 dpi
<Abnormal transcription evaluation>
The abnormal transcription was evaluated according to the following criteria.

○: Abnormal transfer to the transfer object is not observed Δ: Abnormal transfer to the transfer object is very slight ×: Abnormal transfer to the transfer object is observed on the entire surface

As the evaluation, the results shown in Table 1 were obtained. That is, the thermal transfer recording media of Examples 1 to 6 provided with an undercoat layer formed by applying and drying a coating liquid containing polyvinyl alcohol and polyvinylpyrrolidone as main components are not provided with an undercoat layer. Compared with the heat-sensitive transfer recording medium of Comparative Example 1, it was found that the transfer sensitivity during high-speed printing was clearly higher. It was also found that abnormal transfer during printing at room temperature and in a low-temperature and low-humidity environment has no practical problem. Among them, the thermal transfer recording media of Examples 1 and 4 preferably have a polyvinyl alcohol content of 50% or more in the undercoat layer from the comparison with Comparative Example 5 in abnormal transfer of low temperature / low humidity printing. I understood it. Further, when comparing the thermal recording media of Examples 1 and 2 and the thermal transfer recording medium of Example 4, the content ratio of polyvinyl alcohol and polyvinyl pyrrolidone is the solid content mass ratio from the highest reflection density of low temperature / low humidity printing. Thus, it was found that polyvinyl alcohol / polyvinylpyrrolidone = 5/5 to 7/3 was more preferable. Further, the thermal transfer recording medium of Example 3 is not a combination of two types of modified silicone oils as compared with the thermal transfer recording medium of Example 1, so that the printing sound during low temperature / low humidity printing is low. I found it big. Further, the thermal transfer recording medium of Example 5 has a coating amount of the undercoat layer of less than 0.05 g / m ^{2 as} compared with the thermal transfer recording medium of Example 1, so that it is within a range where there is no practical problem. Although there was, it was found that the adhesion at room temperature was lowered. Further, the thermal transfer recording medium of Example 6 has a practically no problem since the coating amount of the undercoat layer is more than 0.30 g / m ^{2 as} compared with the thermal transfer recording medium of Example 1. However, it was found that the effect of transfer sensitivity was lowered.

  In contrast, in the thermal transfer recording medium of Comparative Example 2, as compared with the thermal transfer recording medium of Example 1, as a result of providing the undercoat layer only with polyvinylpyrrolidone, the adhesion of the dye layer at room temperature and the low temperature were reduced.・ It has been found that there is a problem with abnormal transcription under low humidity conditions. Further, in the thermal transfer recording medium of Comparative Example 3, as compared with the thermal transfer recording medium of Example 1, the binder of the dye layer was changed from acid-modified polyvinyl acetoacetal resin to polyvinyl acetoacetal resin. It has been found that it has the same problems as thermal transfer recording media. Further, the thermal transfer recording medium of Comparative Example 4 was compared with the thermal transfer recording medium of Example 1, and the room temperature confirmed in the thermal transfer recording media of Comparative Examples 2 and 3 as a result of removing the curing agent from the dye layer. It was found that the same problems were observed with respect to the adhesion of the dye layer and abnormal transfer in a low temperature and low humidity environment. In addition, the thermal transfer recording medium of Comparative Example 5 was compared with the thermal transfer recording medium of Example 1, and the polyvinyl alcohol ratio of the undercoat layer was 50% or less.・ It has been found that there is a problem with abnormal transcription under low humidity conditions.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problems described in the column of problems to be solved by the invention can be solved, and the effects described in the effects of the invention can be obtained. In some cases, a configuration from which this configuration requirement is deleted can be extracted as an invention.

  The thermal transfer recording medium obtained by the present invention can be used in a sublimation transfer type printer, and in combination with high speed and high functionality of the printer, various images can be easily formed in full color. Can be widely used for cards such as identification cards, amusement output, etc.

DESCRIPTION OF SYMBOLS 10 ... Base material 20 ... Undercoat layer 30 ... Dye layer 40 ... Heat-resistant slipping layer

Claims (5)

In the heat-sensitive transfer recording medium provided with a heat-resistant slipping layer on one side of the substrate, and provided with an undercoat layer and a dye layer in this order on the other side of the substrate,
The undercoat layer contains at least polyvinyl alcohol and polyvinylpyrrolidone, the ratio of polyvinyl alcohol in the undercoat layer is 50% or more by weight, and the binder resin constituting the dye layer is at least acid-modified polyvinyl A thermal transfer recording medium comprising an acetoacetal resin and a curing agent that reacts with a binder resin added to the dye layer.   2. The thermal transfer recording medium according to claim 1, wherein the blending ratio of the polyvinyl alcohol and the polyvinyl pyrrolidone is (polyvinyl alcohol) / (polyvinyl pyrrolidone) = 7/3 to 5/5 on a weight basis. .   3. The thermal transfer recording medium according to claim 1, wherein the curing agent is an isocyanate compound. Coating amount after drying of the undercoat layer is, the heat-sensitive transfer of any one of claims 1 to 3, characterized in that in the range of 0.05 g / m ² or more 0.30 g / m ² or less recoding media.   A release agent composed of at least two kinds of modified silicone oils is added to the dye layer, and one modified silicone oil is a non-reactive silicone oil modified with a side chain polyether having a molecular weight of 8000 or more. The thermal transfer recording medium according to any one of claims 1 to 4, wherein the modified silicone oil is a reactive silicone oil modified with a side chain diamine having a molecular weight of 3000 or less.

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