JP2013184319A - Thermal transfer recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer recording medium which achieves high transfer sensitivity during high-speed printing both in low-density parts and high-density parts, and can reduce dye to be used for a dye layer.SOLUTION: In a thermal transfer recording medium, an undercoating layer and a dye layer are laminated on a base material in order. The undercoating layer is formed by applying an application liquid for forming undercoating layers including polyvinyl alcohol and heat conductive fine particles and drying it. The heat conductivity of the undercoating layer is 1.0-5.0 W/(m×K). The dye layer is formed by applying an application liquid for forming dye layers including an anthraquinone compound as a thermal transferable dye and drying it.

Description

  The present invention relates to a thermal transfer recording medium used in a thermal transfer printer, and more particularly to a thermal transfer recording medium in which an undercoat layer and a dye layer are sequentially formed on a substrate. More specifically, the present invention relates to a thermal transfer recording medium in which the transfer sensitivity during high-speed printing is high in both the low density portion and the high density portion, that is, the dye used for the dye layer can be reduced.

  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 heat-sensitive transfer layer is an ink layer, and the ink is sublimated (sublimation transfer method) or melted (melt transfer method) by heat generated in the thermal head of the printer, and transferred to the transfer target side. is there.

  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 printed material obtained. In recent years, durability has been given to the printed material on the same side of the base sheet. 2. Description of the Related Art Thermal transfer recording media having a plurality of thermal transfer layers provided so as not to overlap protective layers and the like that have been widely used have become quite popular.

  Under such circumstances, with the diversification and widespread use of applications, there has been 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 are caused by heat, pressure, etc. during the manufacture of the thermal transfer recording medium or during printing. It has a problem that it occurs or in some cases breaks.

  Further, in the dye layer of the thermal transfer recording medium, an attempt is made to increase the printing density and the transfer sensitivity in printing by increasing the dye ratio (Dye / Binder) to the resin. However, not only does the cost increase by increasing the dye, but part of the dye is transferred to the heat-resistant slipping layer of the thermal transfer recording medium in the winding state in the manufacturing process (setback), and when it is subsequently rolled back, When the transferred dye is re-transferred to the dye layer of another color or the protective layer (back-to-back), and this contaminated layer is thermally transferred to the transfer target, the hue becomes different from the specified color, so-called ground. Dirt is generated.

  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. Therefore, the so-called abnormal transfer in which the transfer target is fused 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 containing a polyvinylpyrrolidone resin and a modified polyvinylpyrrolidone resin between a base material and a dye layer.

  Patent Document 2 proposes a thermal transfer sheet having an adhesive layer composed of polyvinylpyrrolidone resin or polyvinyl alcohol resin, which is a thermoplastic resin, and colloidal inorganic pigment ultrafine particles, between a base material and a dye layer. Yes.

  Patent Document 3 proposes a thermal transfer sheet having an underlayer composed of a vinylpyrrolidone-vinyl acetate copolymer and colloidal inorganic pigment ultrafine particles between a substrate and a dye layer.

JP-A-2005-231354 JP 2006-150956 A JP 2008-155612 A

  However, when printing is performed with a high-speed printer using the sublimation transfer method on the thermal transfer recording medium proposed in Patent Document 1, the transfer sensitivity in printing is low from the low density portion to the high density portion, and reaches a sufficient level. It wasn't. On the other hand, when the same printing is performed with the thermal transfer recording medium proposed in Patent Documents 2 and 3, the transfer sensitivity in the high density portion is increased by the addition of colloidal inorganic pigment ultrafine particles as compared with Patent Document 1. Admitted. However, trying to reduce the dye in the dye layer (reducing the ratio of dye to resin) on a thermal transfer recording medium in which an increase in transfer sensitivity was observed only in the high density area, the transfer sensitivity in the low density area was insufficient. Become. As described above, in the prior art, the transfer sensitivity in printing is high in both the low density portion and the high density portion, that is, there is no thermal transfer recording medium that can realize the reduction of the dye used in the dye layer. .

  Accordingly, in view of the above problems, the present invention provides a thermal transfer recording medium in which the transfer sensitivity during high-speed printing is high in both the low density portion and the high density portion, that is, the reduction of the dye used in the dye layer can be realized. It is intended to do.

  In the thermal transfer recording medium according to the present invention, an undercoat layer and a dye layer are sequentially laminated on a substrate, and the undercoat layer is applied with an undercoat layer forming coating solution containing polyvinyl alcohol and thermally conductive fine particles. The undercoat layer has a thermal conductivity of 1.0 to 5.0 W / (m · K), and the dye layer contains an anthraquinone compound as a heat transfer dye. It is characterized by being formed by applying and drying a coating solution for forming a dye layer.

  In the thermal transfer recording medium of the present invention, an undercoat layer and a dye layer are sequentially laminated on a substrate, and the undercoat layer is applied with an undercoat layer forming coating solution containing polyvinyl alcohol and heat conductive fine particles. The undercoat layer has a thermal conductivity of 1.0 to 5.0 W / (m · K), and the dye layer contains an anthraquinone compound as a heat transfer dye. Since the coating solution for forming the dye layer is applied and dried, the transfer sensitivity during high-speed printing is high in both the low and high density areas, that is, the dye used in the dye layer is reduced. Make it possible.

Side sectional view of a thermal transfer recording medium according to an embodiment of the present invention

  As shown in FIG. 1, the thermal transfer recording medium of one embodiment of the present invention is provided with a heat-resistant slipping layer 40 that imparts slidability with a thermal head on one surface of the substrate 10. The undercoat layer 20 and the dye layer 30 are sequentially formed on the other surface.

  The substrate 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 polyamide , Synthetic resin films such as aramid and polystyrene, and papers such as condenser paper and paraffin paper can be used 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 or more and 50 μm or less in consideration of operability and workability, but in consideration of handling properties such as transfer suitability and workability, it is 2 μm or more and 9 μm or less. A degree is preferred.

  Moreover, in the base material 10, it is also possible to perform 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.

Next, 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 or slipping property, a filler, a curing agent, a solvent, and the like. Can be formed by preparing a coating solution for forming a heat resistant slipping layer, coating and drying. The coating amount after drying of the heat resistant slipping layer 40 is not particularly limited, but 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 refers to the solid content remaining after the coating solution for forming the heat resistant slipping layer is applied and dried. Also, the coating amount after drying of the undercoat layer 20 described later and the coating amount after drying of the dye layer 30 are similarly applied to the coating solution for forming the undercoat layer and the coating solution for forming the dye layer described later, The solid content remaining after drying.

  As an example of the heat resistant slipping layer, 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. Examples thereof include acrylate, polyether acrylate, epoxy acrylate, nitrocellulose resin, cellulose acetate resin, polyamide resin, polyimide resin, polyamideimide resin, polycarbonate resin, polyacrylic resin, and modified products thereof.

  Next, the undercoat layer 20 is formed by applying and drying an undercoat layer-forming coating solution containing polyvinyl alcohol and thermally conductive fine particles.

  Polyvinyl alcohol has an excellent dye barrier performance, and can impart high transfer sensitivity at a high density portion where the printing energy is large during printing. The saponification degree and average polymerization degree of such polyvinyl alcohol are not particularly limited. For example, Kuraray Poval PVA-117 (manufactured by Kuraray Co., Ltd.), Kuraray Poval PVA-217 (manufactured by Kuraray Co., Ltd.), etc. Can be used.

  The undercoat layer 20 can contain a water-soluble polymer compound other than the polyvinyl alcohol. Examples of the water-soluble polymer compound include a modified or copolymer of polyvinyl alcohol, polyvinyl pyrrolidone, a modified or copolymer of polyvinyl pyrrolidone, starch, gelatin, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and the like. Among these, from the point that the adhesion between the substrate 10 and the dye layer 30 can be improved and a higher printing density can be obtained, modified polyvinyl alcohol and copolymers, modified polyvinyl pyrrolidone and modified polyvinyl pyrrolidone. And copolymers are preferred.

  The thermally conductive fine particles have the effect of increasing the thermal conductivity of the undercoat layer 20 and increasing the transfer sensitivity in a low density portion where the printing energy is small by adding to the polyvinyl alcohol and other water-soluble polymer compounds. When the undercoat layer 20 is formed only of polyvinyl alcohol or other water-soluble polymer compound, for example, only a thermal conductivity of about 0.3 W / (m · K) can be obtained. Therefore, in the present invention, the thermal conductivity of the undercoat layer 20 is 1.0 to 5.0 W / (m · K) by using the thermally conductive fine particles in combination with polyvinyl alcohol and other water-soluble polymer compounds. It is essential to set it to 2.0 to 5.0 W / (m · K). When the thermal conductivity of the undercoat layer 20 is less than 1.0 W / (m · K), the effect of adding the heat conductive fine particles is not obtained, and the transfer sensitivity in the low density portion does not increase. On the other hand, when the thermal conductivity of the undercoat layer 20 exceeds 5.0 W / (m · K), even if the printing energy is very small, the transfer sensitivity is remarkably high, and the ratio of the dye to the resin is reduced. In addition, the coloring at the low density portion is too strong.

  Examples of the thermally conductive fine particles include inorganic fine particles such as magnesia, anhydrous magnesium carbonate, magnesium hydroxide, zirconia, titania, aluminum nitride, calcium carbonate, hexagonal boron nitride, and kaolin, as well as a thermally conductive material attached to the surface. Organic particles having a thermal conductivity of about 10 to 270 W / (m · K) and an average particle size of about 0.5 to 3.0 μm are preferably used. Among these, it is preferable to use at least one of magnesia, anhydrous magnesium carbonate, magnesium hydroxide, and zirconia, which is relatively inexpensive and has high thermal conductivity.

  In the present invention, the thermal conductivity of the undercoat layer 20 can be adjusted to 1.0 to 5.0 W by appropriately adjusting the type and amount of the heat conductive fine particles, the coating amount after drying the undercoat layer 20 and the like. / (M · K).

  The content ratio of the water-soluble polymer compound containing polyvinyl alcohol and the heat conductive fine particles in the undercoat layer 20 on a mass basis is water-soluble polymer compound / heat conductive fine particles = 40/60 to 90/10. It is preferable that the ratio is 50/50 to 80/20. If the content ratio of the water-soluble polymer compound / thermally conductive fine particles exceeds 90/10, the thermal conductivity of the undercoat layer may not be sufficiently increased, and the effect of improving the transfer sensitivity in the low density portion may be reduced. . On the other hand, if the content ratio of the water-soluble polymer compound / thermally conductive fine particle is less than 40/60, the effect of improving the transfer sensitivity may be reduced at a high density portion where the printing energy is large during printing.

Coating amount after drying of the undercoat layer 20, but are not unconditionally limited, 0.05 g / m ² or more, preferably in the 0.30 g / m ² or less of the range, and further 0. More preferably, it is in the range of 10 g / m ² or more and 0.20 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 during lamination of the dye layer, and the adhesion to the substrate or the dye layer may be reduced. On the other hand, if it exceeds 0.30 g / m ² , the sensitivity of the thermal transfer recording medium itself is affected, and the transfer sensitivity at the time of high-speed printing may be reduced.

  The undercoat layer 20 may use known additives such as inorganic pigment fine particles, isocyanate compounds, silane coupling agents, dispersants, viscosity modifiers, stabilizers and the like within a range not impairing the performance. it can.

  Next, the dye layer 30 is formed by preparing a coating solution for forming a dye layer by blending, for example, a binder, a solvent and the like in addition to the heat transferable dye, and applying and drying. The dye layer can be composed of a single layer of one color, and a plurality of dye layers containing dyes having different hues can be repeatedly formed on the same surface of the same base material in the surface order.

  The heat transferable dye used for the dye layer 30 is a dye that melts, diffuses or sublimates and transfers by heat. For example, as the yellow component, C.I. I. Solvent Yellow 56, 16, 30, 93, 33, or C.I. I. 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, 38, or C.I. I. Solvent red 19, 27, etc. can be mentioned. In the present invention, among these, C.I. I. It is essential to use an anthraquinone compound represented by Disperse Violet 38 or the like as a heat transfer dye. As the cyan component, C.I. I. Disperse Blue 24, 257, 354, or C.I. I. Solvent blue 36, 63, 266, etc. can be mentioned. In the present invention, among these, C.I. I. Solvent Blue 36, 63 or C.I. I. It is essential to use an anthraquinone compound typified by Disperse Blue 24 as a heat transfer dye. The reason for this is that when an undercoat layer is introduced between the substrate and the dye layer, the dye composed of an anthraquinone compound has a higher transfer sensitivity to the image receiving layer than other dyes, and thus gives a high transfer sensitivity, that is, This is because the dye used in the dye layer can be reduced.

  The binder contained in the dye layer 30 may be any conventionally known resin binder, and is not particularly limited, but cellulose such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, cellulose acetate, etc. And vinyl resins such as polyvinyl resins, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, polyvinyl pyrrolidone, polyacrylamide, polyester resins, styrene-acrylonitrile copolymer resins, phenoxy resins, and the like.

  Here, the blending ratio of the heat-transferable dye and the binder on the mass basis when forming the dye layer 30 is preferably heat-transferable dye / binder = 10/100 to 300/100. This is because when the blending ratio of the heat transferable dye / binder is less than 10/100, the dye is too little and the color development sensitivity becomes insufficient, and a good thermal transfer image cannot be obtained. Also, this blending ratio is 300/100. This is because the solubility of the dye in the binder is extremely reduced when the content exceeds 1, the resulting heat-sensitive transfer recording medium has low storage stability and the dye is likely to precipitate.

  The dye layer 30 may contain known additives such as a dispersant, a viscosity modifier, and a stabilizer as long as the performance is not impaired.

The coating amount after drying of the dye layer 30 is not limited in general, but it is 0.3 g / m ² or more from the viewpoint of suppressing abnormal transfer and wrinkling during printing and suppressing cost increase. 1.5 g / m ² or less is appropriate.

  The heat resistant slipping layer 40, the undercoat layer 20 and the dye layer 30 are respectively known as a heat resistant slipping layer forming coating solution, an undercoat layer forming coating solution and a dye layer forming coating solution. It can be formed by coating by a coating method and drying. Examples of the application method include a gravure coating method, a screen printing method, a spray coating method, and a reverse roll coating method.

  Below, the material used for each Example and each comparative example of this invention is shown. In the text, “part” is based on mass unless otherwise specified. Further, the present invention is not limited to these examples.

<Preparation of substrate with heat-resistant slip layer>
As a base material, use a polyethylene terephthalate film with a thickness of 4.5μm on one side, and after drying a coating solution for forming a heat-resistant slipping layer having the following composition on the non-adhesive surface by gravure coating. Was applied at 0.5 g / m ² and dried at 100 ° C. for 1 minute to obtain a substrate with a heat resistant slipping layer.

<Coating liquid for forming heat resistant slipping layer>
Silicon modified acrylic resin (US-350, manufactured by Toagosei Co., Ltd.) 50.0 parts Methyl ethyl ketone 50.0 parts

Example 1
The undercoat layer-forming coating solution-1 having the following composition is applied to the surface of the substrate with a heat-resistant slip layer by a gravure coating method so that the coating amount after drying is 0.20 g / m ^2. Then, an undercoat layer was formed by drying at 100 ° C. for 2 minutes. Subsequently, on the undercoat layer, a dye layer forming coating solution-1 having the following composition was applied by a gravure coating method so that the coating amount after drying was 0.70 g / m ² , at 90 ° C. The dye layer was formed by drying for 1 minute, and the thermal transfer recording medium of Example 1 was obtained.

<Undercoat layer forming coating solution-1>
Polyvinyl alcohol (Kuraraypoval PVA-117) 3.0 parts magnesia (thermal conductivity 55 W / (m · K), average particle size 1.0 μm)
0.9 parts pure water 57.7 parts isopropyl alcohol 38.4 parts

<Dye layer forming coating solution-1>
C. I. Solvent Blue 63 (anthraquinone dye) 6.0 parts Polyvinyl acetal 4.0 parts Toluene 45.0 parts Methyl ethyl ketone 45.0 parts

(Example 2)
In the thermal transfer recording medium produced in Example 1, the thermal transfer recording of Example 2 was performed in the same manner as in Example 1 except that the undercoat layer was formed with the undercoat layer forming coating solution-2 having the following composition. A medium was obtained.

<Undercoat layer forming coating solution-2>
Polyvinyl alcohol (Kuraraypoval PVA-117) 1.5 parts Polyvinylpyrrolidone (N-vinyl-2-pyrrolidone homopolymer)
1.5 parts magnesia (thermal conductivity 55 W / (m · K), average particle size 1.0 μm)
0.9 parts pure water 57.7 parts isopropyl alcohol 38.4 parts

(Example 3)
In the thermal transfer recording medium produced in Example 1, the thermal transfer recording of Example 3 was performed in the same manner as in Example 1 except that the undercoat layer was formed with the undercoat layer-forming coating solution-3 having the following composition. A medium was obtained.

<Undercoat layer forming coating solution-3>
Polyvinyl alcohol (Kuraraypoval PVA-117) 3.0 parts magnesia (thermal conductivity 55 W / (m · K), average particle size 1.0 μm)
4.5 parts pure water 55.5 parts isopropyl alcohol 37.0 parts

(Comparative Example 1)
In the thermal transfer recording medium produced in Example 1, a thermal transfer recording medium of Comparative Example 1 was obtained in the same manner as in Example 1 except that no undercoat layer was formed.

(Comparative Example 2)
In the thermal transfer recording medium produced in Example 1, the thermal transfer recording of Comparative Example 2 was performed in the same manner as in Example 1 except that the undercoat layer was formed with the undercoat layer forming coating solution-4 having the following composition. A medium was obtained.

<Undercoat layer forming coating solution-4>
Polyvinyl pyrrolidone (N-vinyl-2-pyrrolidone homopolymer)
3.0 parts magnesia (thermal conductivity 55 W / (m · K), average particle size 1.0 μm)
0.9 parts pure water 57.7 parts isopropyl alcohol 38.4 parts

(Comparative Example 3)
In the thermal transfer recording medium produced in Example 1, the thermal transfer recording of Comparative Example 3 was performed in the same manner as in Example 1 except that the undercoat layer was formed with the undercoat layer forming coating solution-5 having the following composition. A medium was obtained.

<Undercoat layer forming coating solution-5>
Polyvinyl alcohol (Kuraray Poval PVA-117) 3.0 parts Fused silica (thermal conductivity 3 W / (m · K), average particle size 1.0 μm)
3.0 parts Pure water 56.4 parts Isopropyl alcohol 37.6 parts

(Comparative Example 4)
In the thermal transfer recording medium produced in Example 1, the thermal transfer recording of Comparative Example 4 was performed in the same manner as in Example 1 except that the undercoat layer was formed with the undercoat layer forming coating solution-6 having the following composition. A medium was obtained.

<Undercoat layer forming coating solution-6>
Polyvinyl alcohol (Kuraraypoval PVA-117) 3.0 parts magnesia (thermal conductivity 55 W / (m · K), average particle size 1.0 μm)
6.0 parts pure water 54.6 parts isopropyl alcohol 36.4 parts

(Comparative Example 5)
In the thermal transfer recording medium produced in Example 1, the thermal transfer recording medium of Comparative Example 5 was prepared in the same manner as in Example 1 except that the dye layer was formed with the dye layer forming coating liquid-2 having the following composition. Obtained.

<Dye layer forming coating solution-2>
C. I. Solvent Blue 266 (azo dye) 6.0 parts Polyvinyl acetal 4.0 parts Toluene 45.0 parts Methyl ethyl ketone 45.0 parts

<Preparation of transfer object>
A white foamed polyethylene terephthalate film having a thickness of 188 μm is used as a substrate, and an application layer-forming coating solution having the following composition is applied on one surface thereof by a gravure coating method to a coating amount after drying of 5.0 g / m ^2. The material to be transferred for thermal transfer was prepared by applying and drying.

<Image-receiving layer forming 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

<Measurement of thermal conductivity>
An undercoat layer was formed on the thermal conductivity measurement substrate in the same manner as in Examples 1 to 3 and Comparative Examples 2 to 5, and the photoacoustic thermal diffusivity measurement device “LaserPIT” (manufactured by ULVAC-RIKO) was used. Measured. The results are shown in Table 1.

<Print evaluation>
Using the thermal transfer recording media of Examples 1 to 3 and Comparative Examples 1 to 5, solid printing was performed with a thermal simulator (manufactured by Wedge Co., Ltd.), and each gradation obtained by dividing 255 gradations, which are the maximum reflection density, into 11 parts. The reflection density was evaluated. The results are shown in Table 2. The transfer sensitivity in the low density area was evaluated by the reflection density at 23 to 93 gradations, and the transfer sensitivity in the high density area was evaluated by the reflection density at 255 gradations. The reflection density is a value measured with a spectral densitometer “X-Rite 528” (manufactured by X-Rite Co., Ltd.).

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

  From the results shown in Tables 1 and 2, the thermal transfer recording media of Examples 1 to 3 clearly have a transfer sensitivity at the time of high-speed printing as compared with the thermal transfer recording medium of Comparative Example 1 in which no undercoat layer is provided. It was found that both the low density part and the high density part were high, and it was possible to reduce the dye used in the dye layer.

  The thermal transfer recording medium of Example 2 uses a water-soluble polymer compound so that the content ratio of polyvinyl alcohol and polyvinyl pyrrolidone on a mass basis is polyvinyl alcohol / polyvinyl pyrrolidone = 50/50. Since the layer is formed, it can be seen that the transfer sensitivity of the high density portion is slightly lowered as compared with the thermal transfer recording medium of Example 1 in which the undercoating layer is formed using polyvinyl alcohol alone.

  In the thermal transfer recording medium of Example 3, in the undercoat layer, the content ratio of polyvinyl alcohol and magnesia, which is a heat conductive fine particle, on a mass basis is polyvinyl alcohol / magnesia = 100/150, and polyvinyl alcohol / magnesia. Compared with the thermal transfer recording medium of Example 1 in which = 100/30, the thermal conductivity of the undercoat layer is higher, so that the transfer sensitivity of the low density portion is further increased.

  On the other hand, the thermal transfer recording medium of Comparative Example 2 was obtained by forming an undercoat layer using only polyvinyl pyrrolidone without using polyvinyl alcohol as the water-soluble polymer compound. In comparison, it was found that the transfer sensitivity was extremely low.

  In the thermal transfer recording medium of Comparative Example 3, an undercoat layer is formed using fused silica instead of magnesia, and the thermal conductivity of fused silica is significantly lower than that of magnesia. Although the content ratio on the mass basis is polyvinyl alcohol / fused silica = 100/100, the thermal conductivity of the undercoat layer is less than 1.0 W / (m · K), and the transfer of the low density portion is performed. The sensitivity was comparable to that of Comparative Example 1 where no undercoat layer was formed.

  In the thermal transfer recording medium of Comparative Example 4, since the thermal conductivity of the undercoat layer exceeds 5.0 W / (m · K), the transfer sensitivity is greatly increased even at 23 gradations. When trying to reduce the ratio of the dye, it was found that the color development in the low density part was too strong.

  The thermal transfer recording medium of Comparative Example 5 did not use an anthraquinone compound but formed a dye layer using only an azo compound. As a result, compared with the thermal transfer recording medium of Example 1, the transfer sensitivity at a high density portion was high. It can be seen that is significantly reduced. Therefore, in addition to containing polyvinyl alcohol in the undercoat layer, it was found that the transfer sensitivity of the high concentration part was further improved by containing an anthraquinone compound as a heat transfer dye in the dye layer.

  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.

10 Substrate 20 Undercoat layer 30 Dye layer 40 Heat resistant slipping layer

Claims (1)

An undercoat layer and a dye layer are sequentially laminated on the substrate,
The undercoat layer is formed by applying a coating solution for forming an undercoat layer containing polyvinyl alcohol and thermally conductive fine particles, and drying it. The thermal conductivity of the undercoat layer is 1.0-5. 0.0 W / (m · K),
A thermal transfer recording medium, wherein the dye layer is formed by applying and drying a dye layer forming coating solution containing an anthraquinone compound as a heat transfer dye.

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