JP6572573B2 - Thermal transfer recording medium - Google Patents

Description

  The present invention relates to a thermal transfer recording medium used in a thermal transfer printer.

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

  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 protective layer for imparting durability and a plurality of thermal transfer layers provided so as not to overlap therewith 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 (back-in reverse) and the contaminated layer is thermally transferred to the transfer target, a hue different from the designated color is obtained.

  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 transferred material are fused, and banding that occurs because the dye layer and the transferred material are not continuously peeled, and so-called abnormal transfer in which the dye layer is transferred to the transferred material are likely to occur. On the other hand, if a large amount of a release agent is added to the dye layer or the transfer target in order to prevent banding or abnormal transfer, blurring of the image or background stains may occur.

  In order to solve such a problem, several methods have been proposed. For example, Patent Document 1 proposes a thermal transfer sheet made of any one or more of cellulose acetate propionate resin, cellulose acetate butyrate resin, and ethyl cellulose resin.

  Patent Document 2 proposes a thermal transfer sheet made of a binder resin having a nitrocellulose resin and a polyvinyl acetal resin.

JP 2013-146876 A JP 2013-202846 A

  However, when printing is performed with a sublimation transfer type high-speed printer using the thermal transfer sheet proposed in Patent Document 1, dye transfer efficiency is increased and sufficient print density is obtained, but storage stability of the dye is increased. This is a problem, because the dye deposited on the surface of the dye layer contaminates the unprinted area during printing, and the adhesion between the dye layer and the substrate is not sufficient, and abnormal transfer also occurs. There is. In addition, when printing is similarly performed using the thermal transfer sheet proposed in Patent Document 2, the amount of the dye mixed with the polyvinyl acetal resin for the purpose of improving the adhesion to the base material is higher than that of the nitrocellulose resin alone. There is a problem that the transfer efficiency of the toner becomes low.

  In view of the above problems, the present invention has high dye transfer efficiency during high-speed printing, excellent storage stability, and suppresses the occurrence of abnormal transfer in which the dye layer is transferred to the transfer medium during thermal transfer. It is an object of the present invention to provide a thermal transfer recording medium.

The present invention provides a heat-sensitive transfer recording medium in which a heat-resistant slipping layer is provided on one surface of a substrate, and an undercoat layer and a dye layer are provided in this order on the other surface of the substrate. It contains a nitrocellulose resin and a cellulose acetate butyrate resin, and a release agent is added. The mixing ratio of the nitrocellulose resin and the cellulose acetate butyrate resin in the dye layer is 3.20: 0. 80 to 1.20: 2.80 and wherein the der Rukoto.

  Further, the mixing ratio of the nitrocellulose resin and the cellulose acetate butyrate resin in the dye layer may be in the range of 7: 3 to 4: 6 on a mass basis.

  Further, the release agent added to the dye layer may be a polyether-modified silicone oil.

  According to the thermal transfer recording medium of the present invention, it is possible to realize a thermal transfer recording medium that has high dye transfer efficiency during high-speed printing, excellent storage stability, and suppresses abnormal transfer.

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

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

  Since the base material (10) is required to have heat resistance and strength that is not softened and deformed by heat pressure in thermal transfer, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide , Synthetic resin films such as polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, and ionomer, 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. In addition, 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.

  Moreover, in a base material (10), it is also possible to give an adhesive process to single side | surface or / and both surfaces. 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

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 imparting releasability or slipperiness, a filler, a curing agent, a solvent, and the like. A coating solution for forming a heat resistant slipping layer can be prepared by blending, coating and drying. 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) refers to the amount of solid content remaining after coating and drying the coating solution for forming the heat-resistant slipping layer. Similarly, the coating amount after drying and the coating amount after drying the dye layer (30) also refer to the amount of solid content remaining after coating and drying the coating solution.

  As an example of the heat resistant slipping layer (40), as the binder resin, polyvinyl butyral resin, polyvinyl acetoacetal resin, polyester resin, vinyl chloride-vinyl acetate copolymer, polyether resin, polybutadiene resin, acrylic polyol, polyurethane Examples thereof include acrylate, polyester acrylate, polyether acrylate, epoxy acrylate, nitrocellulose resin, cellulose acetate resin, polyamide resin, polyimide resin, polyamideimide resin, and polycarbonate resin.

  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.

  Next, the undercoat layer (20) can be formed mainly of a binder having good adhesion to both the substrate and the dye layer. Examples of the binder include polyvinyl pyrrolidone resins, polyvinyl alcohol resins, polyester resins, polyurethane resins, polyacrylic resins, polyvinyl formal resins, epoxy resins, polyvinyl butyral resins, polyamide resins, and polyethers. Resin, polystyrene resin, styrene-acrylic copolymer resin and the like.

Coating amount after drying of the undercoat layer (20), but are not unconditionally limited, in coating amount of solid content ^{is 0.02g / m 2 ~2.0g / m 2} . If this film thickness is less than 0.02 g / m ² , there is a concern that the transfer sensitivity will decrease, and if it is greater than 2.0 g / m ² , heat transfer from the thermal head to the dye layer will deteriorate. This causes a disadvantage that the print density is lowered.

  In the undercoat layer (20), known additives such as colloidal inorganic pigment ultrafine particles, isocyanate compounds, silane coupling agents, dispersants, viscosity modifiers and stabilizers can be used. As the colloidal inorganic pigment ultrafine particles, conventionally known ones can be used, for example, silica (colloidal silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or hydrate thereof). , Suspected boehmite, etc.), aluminum silicate, magnesium silicate, magnesium carbonate, magnesium oxide, titanium oxide and the like.

Next, the dye layer (30) can be formed, for example, by preparing a coating solution for forming a dye layer by blending a heat-transferable dye, a binder, a solvent, and the like, and applying and drying. The coating amount after drying the dye layer (30) is suitably about 0.5 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 contained in the dye layer (30) is not particularly limited as long as it is a dye that melts, diffuses or sublimates and transfers by 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.

  Examples of the binder resin contained in the dye layer (30) include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, and cellulose acetate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, and polyvinyl acetal. , Polyvinyl pyrrolidone, polyacrylamide and other vinyl resins, polyester resins, styrene-acrylonitrile copolymer resins, phenoxy resins, etc., but high dye transfer efficiency during high-speed printing, excellent storage stability, Nitrocellulose resin and cellulose acetate butyrate resin are required to realize a thermal transfer recording medium that can suppress abnormal transfer of the dye layer to the transfer material during thermal transfer. It is.

  Since the nitrocellulose resin as the binder resin has a high dye-holding power, it is possible to prevent the occurrence of background stains. Further, it is superior in dye transfer efficiency in a high gradation portion as compared with conventionally known vinyl resins.

  Nitrocellulose resin is self-igniting and requires careful handling. In consideration of safety, the nitrogen content is preferably 12.5% or less.

  The viscosity of nitrocellulose according to JIS K-6703 is preferably from 1/4 to 120. When the viscosity according to JIS K-6703 is less than ¼, the storage stability is deteriorated and soiling is likely to occur. On the other hand, when the viscosity according to JIS K-6703 exceeds 120, ink breakage deteriorates, so that ink mist is generated and surface defects may occur.

Nitrocellulose is commercially available. For example, the following products can be used.
Taihei Chemical Products Co., Ltd. H1 / 4, H1 / 2, H1, H5, H20, H60, H120, L1 / 4, Inabata Sangyo Co., Ltd. DHX8-13, DHX11-16, DHX30-50, DHX40-70 , DHL25-45, DHL120-170, DLX8-13

  Cellulose acetate butyrate as a binder resin has a higher dye transfer efficiency than conventionally known vinyl resins and nitrocellulose resins, so that a sufficient print density can be obtained.

  The molecular weight of cellulose acetate butyrate is preferably 30000 or more. If the molecular weight is less than 30000, the dye retention during heating and the adhesion to the substrate are inferior, so abnormal transfer is likely to occur. Moreover, since the viscosity of the dye layer coating solution is low, surface defects are likely to occur when the dye layer is formed.

Cellulose acetate butyrate is commercially available. For example, the following products can be used.
CAB551-0.2, CAB531-1, CAB500-5, CAB381-0.5, CAB381-20, CAB171-15 manufactured by Eastman Chemical Co.

  The mixing ratio of the nitrocellulose resin and the cellulose acetate butyrate resin is preferably in the range of 7: 3 to 4: 6 by mass ratio. When the mixing ratio of the nitrocellulose resin is less than or equal to the upper limit (70%), a sufficient print density is easily obtained, and when the cellulose acetate butyrate resin is less than or equal to the upper limit (60%), the storage stability of the dye is improved. Improves soiling.

  Here, the mixing ratio of the dye and the binder resin in the dye layer (30) is preferably (dye) / (binder resin) = 10/100 to 300/100 on a mass basis. This is because when the ratio of (dye) / (binder resin) 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. This is because the solubility of the dye with respect to the binder resin decreases, and thus, when it becomes a thermal transfer recording medium, the storage stability deteriorates and the dye is likely to precipitate.

  By including a release agent in the dye layer (30), it is possible to prevent fusion between the dye layer and the transfer target during printing. Examples of the release agent include various oils and surfactants such as silicone-based, fluorine-based, and phosphate ester-based, and polyether-modified silicone oil is particularly preferable. The polyether-modified silicone oil is a silicone oil (polysiloxane) that is a polymer composed of a siloxane bond, and has a polyether having a hydrophilic group introduced in a side chain and / or a terminal. The siloxane chain may be linear, branched, or crosslinked. General silicone oil does not dissolve in water at all and exhibits water repellency. However, it has excellent compatibility with both aqueous and non-aqueous systems due to its polyether modification. It exhibits an excellent anti-fusing effect that cannot be obtained with an activator.

The polyether-modified silicone is commercially available. For example, the following products can be used.
KF-351, KF-352, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-644, manufactured by Shin-Etsu Silicone Co., Ltd. KF-6020, KF-6204, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017, KF-6004, X-22-4952, X-22-4272, KF-6123, Toray Dow Corning SH8700, SF8410, SH8400, L-7002, FZ-2104, FZ-77, L-7604, FZ-2203, Momentive Performance Materials TSF4440, TSF4441, TSF4445, TSF4450, TSF4446, TSF4452 and TSF4460

  A release agent having a small molecular weight is likely to be localized on the surface of the dye layer, but is liable to cause soiling and tends to deteriorate dye storage stability. Therefore, the molecular weight of the release agent is preferably 8000 or more.

  The addition amount of the release agent is preferably in the range of 1.0 to 7.0% by mass, particularly in the range of 2.0 to 6.0% by mass with respect to the binder resin of the dye layer (30). preferable. When the content is less than 1.0% by mass, fusion is likely to occur between the thermal transfer layer at the time of printing and the transfer target, and heat wrinkles become severe due to fusion, resulting in transfer unevenness. On the other hand, when the content is larger than 7.0% by mass, the slipperiness with the transfer medium is improved, but the dye sublimation is hindered, and transfer unevenness or a printed matter with a desired density cannot be obtained.

  The dye layer (30) 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.

  According to the heat-sensitive transfer recording medium according to the present embodiment, the dye layer contains a nitrocellulose resin and a cellulose acetate butyrate resin as a binder resin, and a release agent is added, so that the dye at the time of high-speed printing can be obtained. The transfer efficiency is high, the storage stability is excellent, and the occurrence of abnormal transfer can be suppressed. In addition, when the mixing ratio of the nitrocellulose resin and the cellulose acetate butyrate resin in the dye layer is in the range of 7: 3 to 4: 6 on a mass basis, a sufficient print density can be obtained and the dye can be stored. It is possible to suppress the occurrence of background stains due to a decrease in stability. Further, by using a polyether-modified silicone oil as the release agent added to the dye layer, it is possible to prevent fusion between the dye layer and the transfer target during printing.

  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.

<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 become 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 one 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, on the undercoat layer, the dye layer 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 , and at 90 ° C. for 1 minute. By drying, a dye layer was formed, and the thermal transfer recording medium of Example 1 was obtained.

<Undercoat layer coating solution-1>
Polyvinyl alcohol 2.50 parts Polyvinylpyrrolidone 2.50 parts Pure water 57.0 parts Isopropyl alcohol 38.0 parts

<Dye layer coating solution-1>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Industry Co., Ltd.) 2.80 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Company) 1.20 parts Diamine-modified silicone oil 0 .08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

In the thermal transfer recording medium produced in Example 1, the thermal transfer of Example 2 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-2 having the following composition. A recording medium was obtained.
<Dye layer coating solution-2>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Industry Co., Ltd.) 2.40 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Co.) 1.60 parts Diamine-modified silicone oil 0 .08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Example 3)
In the thermal transfer recording medium produced in Example 1, the thermal transfer of Example 3 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-3 having the following composition. A recording medium was obtained.
<Dye layer coating solution-3>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Industry Co., Ltd.) 2.00 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Co.) 2.00 parts Diamine-modified silicone oil 0 .08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

Example 4
In the thermal transfer recording medium produced in Example 1, the thermal transfer of Example 4 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-4 having the following composition. A recording medium was obtained.
<Dye layer coating solution-4>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Industry Co., Ltd.) 1.60 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Co.) 2.40 parts Diamine-modified silicone oil 0 .08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Example 5)
In the thermal transfer recording medium produced in Example 1, the thermal transfer of Example 5 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-5 having the following composition. A recording medium was obtained.
<Dye layer coating solution-5>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Industry Co., Ltd.) 3.20 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Co.) 0.80 parts Diamine-modified silicone oil 0 .08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Example 6)
In the thermal transfer recording medium produced in Example 1, the thermal transfer of Example 6 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-6 having the following composition. A recording medium was obtained.
<Dye layer coating solution-6>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Industry Co., Ltd.) 1.20 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Co.) 2.80 parts Diamine-modified silicone oil 0 .08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Example 7)
In the thermal transfer recording medium produced in Example 1, the thermal transfer of Example 7 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-7 having the following composition. A recording medium was obtained.
<Dye layer coating solution-7>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Industry Co., Ltd.) 2.40 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Co.) 1.60 parts Polyether-modified silicone oil 0.08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Comparative Example 1)
In the thermal transfer recording medium produced in Example 1, the thermal transfer of Comparative Example 1 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-8 having the following composition. A recording medium was obtained.
<Dye layer coating solution-8>
C. I. Solvent Blue 63 6.0 parts Polyvinyl acetal resin 4.0 parts Polyether-modified silicone oil 0.08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Comparative Example 2)
In the thermal transfer recording medium produced in Example 1, the thermal transfer of Comparative Example 2 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-9 having the following composition. A recording medium was obtained.
<Dye layer coating solution-9>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: manufactured by Taihei Chemical Co., Ltd.) 4.0 parts Polyether-modified silicone oil 0.08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Comparative Example 3)
In the thermal transfer recording medium prepared in Example 1, the thermal transfer of Comparative Example 3 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-10 having the following composition. A recording medium was obtained.
<Dye layer coating solution-10>
C. I. Solvent Blue 63 6.0 parts Cellulose acetate butyrate resin (CAB171-15: manufactured by Eastman Chemical Co.) 4.0 parts Polyether-modified silicone oil 0.08 parts Methyl ethyl ketone 44.92 parts Toluene 45.00 parts

(Comparative Example 4)
In the thermal transfer recording medium prepared in Example 1, the thermal transfer of Comparative Example 4 was performed in the same manner as in Example 1 except that the dye layer coating solution-1 of the dye layer was changed to the dye layer coating solution-11 having the following composition. A recording medium was obtained.
<Dye layer coating solution-11>
C. I. Solvent Blue 63 6.0 parts Nitrocellulose resin (H20: Taihei Chemical Industry Co., Ltd.) 2.40 parts Cellulose acetate butyrate resin (CAB171-15: Eastman Chemical Co., Ltd.) 1.60 parts Methyl ethyl ketone 45.00 parts Toluene 45.00 parts

<Preparation of transfer 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

<Print evaluation>
Using the thermal transfer recording media of Examples 1 to 7 and Comparative Examples 1 to 4 stored at room temperature and the transfer target, the maximum density of 255 gradations in a thermal simulator under an environment of 23 ° C. and 50% RH Table 1 shows the results of producing a solid printed material and evaluating the maximum reflection density, transfer efficiency, and background stain. Furthermore, Table 1 also shows the results of 30 black gradation prints performed with a thermal simulator in a 48 ° C. and 5% RH environment, and the evaluation of the presence of peeling traces and abnormal transfer. The printing conditions are as follows.
Applied voltage: 29V
Line cycle: 0.7msec
Print density: main scanning 300 dpi sub-scanning 300 dpi

(Maximum reflection density evaluation)
The maximum reflection density was measured under the following conditions. For those having a maximum reflection density of 2.00 or more, it was evaluated that a sufficient print density was obtained, and for those having a maximum reflection density of 2.05 or more, it was evaluated that a sufficient print density was obtained.
Colorimeter: X-Rite 528 (manufactured by X-Rite)
Filter for measurement: Status A

(Evaluation of transfer efficiency)
The absorbance of the unprinted thermal transfer recording medium and the thermal transfer recording medium after printing was measured with a spectrophotometer (measurement wavelength: 850 to 350), and the transfer efficiency was calculated by the following equation using the maximum absorbance. Those having a transfer efficiency of 50% or more were evaluated as having good transfer efficiency.

(Earth dirt evaluation)
The evaluation of scumming was performed according to the following criteria. ○ and Δ are levels that are practically acceptable.
○: Soil is not recognized. △: Slightly soiled is observed. ×: Soil is recognized on the entire surface.

(Abnormal transcription evaluation)
The abnormal transcription was evaluated according to the following criteria. ○ is a level where there is no practical problem.
○: Abnormal transfer to the transfer object is not observed ×: Abnormal transfer to the transfer object is observed on the entire surface

(Banding evaluation)
Banding was evaluated according to the following criteria. ○ and Δ are levels that are practically acceptable.
○: No banding on the transfer object is observed Δ: Very little banding on the transfer object is recognized ×: Banding on the transfer object is recognized on the entire surface

(Evaluation results)
From the results shown in Table 1, the thermal transfer recording media of Examples 1 to 7 have high dye transfer efficiency and were able to obtain a sufficient print density. In addition, since the storage stability is excellent, the background contamination is at a level where there is no practical problem, and abnormal transfer and banding are at a level where there is no problem in practice.

  On the other hand, the thermal transfer recording medium of Comparative Example 1 in which the binder resin of the dye layer is a polyvinyl acetal resin that is conventionally known and is used in many thermal transfer recording media has a poor dye transfer efficiency and is sufficient. The print density could not be obtained. In addition, the thermal transfer recording medium of Comparative Example 2 in which the binder resin of the dye layer is a nitrocellulose resin alone can improve the transfer efficiency as compared with Comparative Example 1, but cannot obtain a sufficient print density. It was. In addition, the thermal transfer recording medium of Comparative Example 3 in which the binder resin of the dye layer is cellulose acetate butyrate resin alone has high transfer efficiency and a sufficient print density, but the adhesion to the undercoat layer is weak. Therefore, abnormal transcription occurred. In addition, since the retention of the dye was not sufficient, soiling occurred. Further, the heat-sensitive transfer recording medium of Comparative Example 4 in which no release agent was added to the dye layer was fused with the transfer target and could not be printed.

  The thermal transfer recording medium obtained by the present invention can be used in a sublimation transfer type printer, and in addition to the 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 prints, ID cards, and amusement output.

DESCRIPTION OF SYMBOLS 1 ... Thermal transfer recording medium 10 ... Base material 20 ... Undercoat layer 30 ... Dye layer 40 ... Heat-resistant slipping layer

Claims (3)

In a thermal transfer recording medium provided with a heat-resistant slipping layer on one side of the substrate, and an undercoat layer and a dye layer provided in this order on the other side of the substrate,
The dye layer includes a nitrocellulose resin and a cellulose acetate butyrate resin as a binder resin, and a release agent is added ,
The mixing ratio between the nitrocellulose resin and the cellulose acetate butyrate resin of said dye layer is by weight 3.20: 0.80 to 1.20: 2.80 thermal transfer recording, characterized in der Rukoto Medium. The mixing ratio between the nitrocellulose resin and the cellulose acetate butyrate resin of said dye layer is 7 by weight: 3-4: characterized in that it is a 6, thermal transfer recording medium according to claim 1. The thermal transfer recording medium according to claim 1 or 2, wherein the release agent added to the dye layer is a polyether-modified silicone oil.