JP2011051300A - Thermal transfer recording medium - Google Patents

Abstract

Ribbon strength during printing is strong, and during thermal transfer recording, the thermal transfer layer, the transfer target, the heat-resistant slipping layer, and the thermal head do not cause fusion, and excellent printing without unevenness or streaking is achieved. Provided is a thermal transfer recording medium that can perform the above.
[Solution]
One surface of the base film is provided with a heat transfer layer having a binder resin and a lubricant, and the other surface of the base film is provided with at least a heat-resistant slip layer having a binder resin and a lubricant. Is a reaction product of a polyvinyl acetal resin having a degree of acetalization of 80% by weight or more and a polyisocyanate, and the amount of polyisocyanate added is 0.5 or more in terms of NCO / OH ratio. The binder resin constituting the conductive layer is a reaction product of a thermoplastic resin having a hydroxyl value of 100 mgKOH / g or more and a polyvalent isocyanate, and the addition amount of the polyvalent isocyanate is 0.8 or more in the ratio of NCO / OH. A thermal transfer recording medium.
[Selection] Figure 1

Description

  In the present invention, at least one heat transfer layer having at least a binder resin and a lubricant is provided on one surface of the base film, and at least a heat resistant slip layer having at least a binder resin and a lubricant is provided on the other surface of the base film. The present invention relates to a thermal transfer recording medium.

  Conventionally, a sublimation type thermal transfer system, a melt type thermal transfer system, or the like has been adopted as a system for thermally transferring and recording characters or images on a thermal transfer medium. For example, in the case of the sublimation type thermal transfer system, the thermal transfer layer surface of a thermal transfer recording medium provided with a thermal transfer layer containing a dye or a binder on a support and the thermal transfer provided with a receiving layer for receiving the dye on the support. The dye in the thermal transfer layer is sublimated by superimposing each other on the surface of the receiving layer of the body and heating the thermal transfer recording medium from the surface where the thermal transfer layer is not provided by a thermal head or the like temperature-controlled by text or image information. The desired character or image is transferred by thermal transfer to the receiving layer. On the other hand, in the case of the melt-type thermal transfer method, the surface of the thermal transfer recording medium provided with a heat-fusible thermal transfer layer containing a pigment, wax or the like on the support, and the thermal transfer member provided with the receiving layer on the support. The surface of the receiving layer is superposed on each other and heated by a thermal head or the like, so that a part of the thermal transfer layer is fused to the side of the thermal transfer body and transferred to the receiving layer, and desired characters or images are recorded by thermal transfer. Of the above methods, the sublimation thermal transfer method is widely used for monochrome copies such as characters and diagrams, and color copies such as digital camera images or computer graphics images.

  In recent years, in such a thermal transfer system, with the increase in printing and image formation speed, the energy applied per unit time by the thermal head during printing and image formation has increased, and the peak temperature applied to the thermal transfer recording medium has been As a result, the base film stretched and wrinkles occurred. In case of significant damage, the base film was broken or the thermal transfer layer and the thermal transfer body or the thermal head and the heat resistant slipping layer were fused. Good image formation may not be performed.

  In order to solve such a problem, several methods have been proposed. For example, in Patent Document 1, by using a sublimation type thermal transfer image-receiving sheet made of a modified polyvinyl acetal resin, and using a polyester resin having a bisphenol skeleton as a constituent material of the dye layer of the thermal transfer sheet, the dye layer and the image-receiving sheet Prevents fusion. Moreover, in patent document 2, the fracture | rupture of a film and the fusion | bonding of a thermal head and a heat resistant slipping layer are prevented by using a polyamideimide resin with high heat resistance as a constituent material of a heat resistant slipping layer.

JP 2006-281446 A JP-A-7-179077

  However, in the method of Patent Document 1, if the compatibility between the modified polyvinyl acetal resin used for the image receiving sheet and the resin used for the dye layer is good, there arises a problem that the image receiving sheet and the dye layer are thermally fused. Further, the method of Patent Document 2 has a problem that the cost of the polyamideimide resin itself is high. In addition, the above method specifies a single component of each of the thermal transfer layer and the heat resistant slipping layer, but if there is a defect on one side, a good image cannot be obtained, so the problem is completely solved. I can't.

  The present invention has been made in order to solve the above-described problems, and has a high ribbon strength at the time of printing, and causes the thermal transfer layer, the thermal transfer body, the thermal head, and the heat-resistant slipping layer to be fused. It is an object of the present invention to provide a thermal transfer recording medium which can perform thermal transfer recording without any irregularity and can perform good printing without unevenness or streaking.

  As a result of earnest research to achieve the above-mentioned problems, the present inventor has found that on one side of the base film, a thermal transfer layer having at least a binder resin and a lubricant is provided on the other side of the base film. Is a thermal transfer recording medium comprising at least a heat-resistant slipping layer having at least a binder resin and a lubricant, wherein the binder resin in the constituent material of the heat-resistant slipping layer and the thermal transfer layer is a reactant comprising a predetermined resin and an additive. As a result, the present inventors have found that the above problems can be achieved, and have completed the present invention.

  That is, according to the first aspect of the present invention, the thermal transfer layer having at least a binder resin and a lubricant is provided on one side of the base film, and at least the binder resin and the lubricant are provided on the other side of the base film. In a thermal transfer recording medium provided with at least a heat resistant slipping layer, the binder resin constituting the thermal transfer layer is a reaction product of a polyvinyl acetal resin having a degree of acetalization of 80% by weight or more and a polyvalent isocyanate, and the addition of the polyvalent isocyanate The amount of NCO / OH is 0.5 or more, and the binder resin constituting the heat-resistant slipping layer is a reaction product of a thermoplastic resin having a hydroxyl value of 100 mgKOH / g and a polyvalent isocyanate, and the addition of the polyvalent isocyanate The thermal transfer recording medium is characterized in that the amount is 0.8 or more in the NCO / OH ratio.

  The invention according to claim 2 is the thermal transfer recording medium according to claim 1, wherein the degree of polymerization of the polyvinyl acetal resin constituting the thermal transfer layer is 1500 or more.

  Furthermore, the invention described in claim 3 is the thermal transfer recording medium described in claim 1 or 2, wherein the lubricant constituting the thermal transfer layer is a silicone-based lubricant.

  Furthermore, the invention according to claim 4 is the thermal transfer recording medium according to any one of claims 1 to 3, wherein the glass transition temperature of the thermoplastic resin constituting the heat resistant slipping layer is 40 ° C. or higher. It is characterized by being.

  Furthermore, the invention according to claim 5 is the thermal transfer recording medium according to any one of claims 1 to 4, wherein the lubricant constituting the heat resistant slipping layer contains a phosphate ester surfactant. It is characterized by.

  The thermal transfer recording medium of the present invention has a strong ribbon strength during printing, and can perform thermal transfer recording without causing the thermal transfer layer, the thermal transfer body, the thermal head, and the heat-resistant slipping layer to be fused. Therefore, if thermal transfer recording is performed using this thermal transfer recording medium, it is possible to obtain a good print without unevenness or streak.

It is explanatory drawing which shows schematic cross-sectional structure of the thermal transfer recording medium based on this invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. As shown in FIG. 1, the thermal transfer recording medium 1 is generally composed of a thermal transfer layer 3 having at least a binder resin and a lubricant on one surface of the base film 2, and the other surface of the base film 2. Is provided with at least a heat-resistant slip layer 4 having at least a binder resin and a lubricant.

  As the base film 2, any film having heat resistance and strength may be used, for example, polyethylene terephthalate film, polyethylene naphthalate film, polypropylene film, polysulfone film, polyimide film, polyvinyl alcohol film, polycarbonate film, A polystyrene film etc. are mentioned. Further, the thickness of the base film 2 may be in the range of about 2.0 to 50 μm, but in consideration of transfer suitability and the like, about 2.0 to 9.0 μm is more preferable.

  On the other hand, in the thermal transfer layer 3, the components contained therein are selectively transferred onto the thermal transfer body by heating with a thermal head from the surface of the thermal transfer recording medium 1 opposite to the surface on which the thermal transfer layer 3 is formed. This is a layer containing a color material for thermal transfer recording of images.

  More specifically, when this thermal transfer layer is a thermal transfer layer containing a thermal sublimation dye, a thin film of a coating solution prepared by blending a thermal sublimation dye, a binder, a solvent, etc. is applied and dried. Can be obtained. The coating amount of the coating liquid at this time is preferably about 1.0 μm in terms of dry thickness.

  As the sublimation dye contained in such a thermal transfer layer, a sublimation disperse dye is mainly preferred. For example, diarylmethane, triarylmethane, thiazole, methine, azomethane, xanthene, axazine, thiazine , Azine-based, acridine-based, azo-based, spirodipyran-based, isodolinospiropyran-based, fluoran-based, rhodaminedactam-based, anthraquinone-based and the like.

  More specifically, examples of the yellow component include C.I. I. Solvent Yellow 14, 16, 29, 30, 33, 56, 93 etc., C.I. I. Examples of magenta components such as disperse yellow 7, 33, 60, 141, 201, 231 include C.I. I. Solvent Red 18, 19, 27, 143, 182, C.I. I. Disperse thread 60, 73, 135, 167, C.I. I. As a cyan component such as disperse violet 13, 26, 31, 56, etc., C.I. I. Solvent Blue 11, 36, 63, 105, C.I. I. Disperse blue 24, 72, 154, 354, etc. are mentioned, but it is not necessarily limited to these. These dyes may be used alone or in combination.

  The constituent material of the thermal transfer layer 3 constituting the thermal transfer recording medium 1 of the present invention is a reaction product of a polyvinyl acetal resin having a degree of acetalization of 80% by weight or more and a polyvalent isocyanate in combination with the above-described dye, and A binder resin having an addition amount of polyvalent isocyanate of 0.5 in terms of NCO / OH is used. Since the water resistance is maintained by using a polyvinyl acetal resin having an acetalization degree of 80% by weight or more, the storability of the thermal transfer layer 3 in a high temperature and high humidity environment, and thus the thermal transfer recording medium 1 can be improved. .

  When the amount of polyvalent isocyanate added is less than 0.5 in NCO / OH, the crosslinking density is low and the heat resistance is insufficient. On the other hand, when NCO / OH is greater than 1.5, unreacted NCO groups remaining in the thermal transfer layer react with moisture in the air or unreacted NCO groups to form a binder resin having a low film forming property. It becomes easy. A range of 0.5 to 1.5 is more preferable.

The degree of polymerization of the polyvinyl acetal resin is preferably 1500 or more, and particularly preferably in the range of 2000 to 3000. Since the glass transition temperature (Tg) is increased by setting the polymerization degree to 1500 or more, the heat resistance of the thermal transfer layer can be increased. Also, the dispersibility and storage stability of the dye can be improved.

  The weight ratio of the dye to the binder (dye / binder) may be about 0.1 to 3.0, more preferably about 0.5 to 1.5. If it is less than 0.1, the dye concentration becomes low, so that the color development sensitivity becomes insufficient and it becomes difficult to obtain a good thermal transfer image. On the other hand, when it is larger than 3.0, the solubility of the dye in the binder is extremely lowered, so that the storage stability of the thermal transfer layer is lowered and the dye is likely to precipitate.

  By containing a lubricant in the thermal transfer layer 3, it is possible to prevent fusion between the thermal transfer layer and the thermal transfer body during printing. Examples of the lubricant include various oils and surfactants such as silicone-based, fluorine-based, and phosphate ester-based, and silicone-based oils and surfactants are particularly preferable.

  More specifically, the silicone type includes straight silicone oils such as dimethyl silicone and methylphenyl silicone, amino modification, epoxy modification, carbinol modification, mercapto modification, carboxyl modification, methacryl modification, polyether modification, phenol modification, piece Non-reactive modified silicone oils such as reactive modified silicone oils such as terminal reactive / different functional group modified, polyether modified, aralkyl modified, fluoroalkyl modified, long chain alkyl modified, higher fatty acid ester modified, phenyl modified, etc. It is done.

  Such a lubricant is preferably contained in a range of about 0.5 to 2.0% by weight, and more preferably in a range of about 1.0 to 1.5% with respect to the binder resin of the thermal transfer layer. When the content is less than 0.5% by weight, fusion is likely to occur between the thermal transfer layer and the thermal transfer body at the time of printing, and heat wrinkles become severe due to fusion, and as a result, transfer unevenness is likely to occur. Become. On the other hand, when the amount is more than 2.0% by weight, the slipperiness with the transfer medium is improved, but the dye sublimation is hindered, and it becomes difficult to obtain transfer unevenness and a printed matter with a desired density.

  The thermal transfer layer 3 may contain various particles for the purpose of preventing dye back-off and blocking. Examples of the particles include inorganic particles such as talc, clay, kaolin, magnesium oxide, magnesium hydroxide, and calcium carbonate, and organic particles such as polyethylene particles, polypropylene particles, polystyrene particles, and silicone particles.

  On the other hand, as described above, the heat resistant slipping layer 4 is a reaction product of a thermoplastic resin having a hydroxyl value of 100 mgKOH / g or more and a polyvalent isocyanate, and the added amount of the polyvalent isocyanate is NCO / The OH ratio is 0.8 or more.

  Examples of the thermoplastic resin having a hydroxyl value of 100 mgKOH / g or more include a resin having a reactive polyol group. Such a resin is preferably used from the viewpoint of reactivity with the polyvalent isocyanate and compatibility. Moreover, when content of polyvalent isocyanate is less than 0.8, a crosslinking density is low and heat resistance becomes inadequate. On the other hand, if the polyisocyanate content is too high, unreacted NCO groups remaining in the heat-resistant slipping layer react with moisture in the air or unreacted NCO groups, resulting in a low film-forming binder resin. Will be easily formed. The amount of polyvalent isocyanate added is more preferably in the range of about 0.8 to 1.3 in terms of NCO / OH ratio.

  Moreover, it is thought that 40 degreeC or more is suitable for the glass transition temperature (Tg) of a thermoplastic resin. By setting Tg to 40 ° C or higher, the ribbon strength at the time of printing is further increased, and the ear is cut (a phenomenon in which the non-printed parts on both sides of the ribbon are broken by heat shrinkage), tears, and tears (the printed part end point is cut) It is thought that printing defects such as phenomenon are unlikely to occur.

  By including a lubricant in such a heat resistant slipping layer 4, fusion with the thermal head can be prevented. Examples of the lubricant include animal waxes, natural waxes such as 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, higher fatty acid metal salts such as zinc stearate, and surfactants such as phosphate esters Can be mentioned. Since these lubricants are present in a state of being dissolved in a molecular form in the binder, it is difficult to cause roughness in the printed portion as compared with the case where a solid lubricant is added. Among these lubricants, phosphate ester surfactants are particularly preferable.

  Specific examples include phosphate esters such as long-chain alkyl phosphate esters, polyoxyalkylene alkyl aryl ethers, and polyoxyalkylene alkyl ethers, but are not necessarily limited thereto.

  These lubricants are preferably included in the range of about 10 to 25% by weight with respect to the binder resin of the heat resistant slipping layer, but more preferably in the range of about 15 to 20% by weight. When the content is less than 10% by weight, fusion is likely to occur between the thermal head and the heat-resistant slipping layer during printing, and printing is stopped in the middle when it is remarkable. On the other hand, when the content is more than 20% by weight, the slipperiness with the thermal head is improved, but the lubricant is liable to float on the surface, so that problems such as set-off easily occur.

The heat-resistant slip layer 4 may further contain particles for the purpose of improving heat resistance. In particular, it is preferable to contain inorganic particles having a specific gravity of 3.0 × 103 kg / m ³ or more. It is considered that the inorganic particles sink into the heat resistant slipping layer and the inorganic particles are prevented from falling off.

  On the other hand, a thermal transfer body for performing thermal transfer recording with the thermal transfer recording medium of the present invention having the above-described configuration is one in which at least a receiving layer is provided on a support. As the support, those equivalent to those used as the base film of the thermal transfer recording medium can be used, but preferably have mechanical strength, flexibility, heat resistance and the like. Specifically, polyester films such as polyethylene terephthalate and polyethylene naphthalate, plastic films made of polyethylene, polyvinyl chloride, polycarbonate, polyester, polysulfane, polyimide, polyvinyl alcohol, aromatic polyamide, aramid film, etc. Examples thereof include paper base materials such as paper, coated paper, and synthetic paper. Although the thickness of a support body is not specifically limited, Generally, what is necessary is just about 25-250 micrometers. If it is about 75-200 micrometers, it is more preferable.

  Further, as the receiving layer, when a sublimation dye is contained in the thermal transfer layer, for example, butyral resin having a dyeing property, polyethylene, polyurethane, polypropylene, polyvinyl chloride, polybutadiene, polyvinyl acetate, vinyl chloride -Thermoplastic resins such as vinyl acetate copolymers, ethylene-vinyl acetate copolymers, polyamides, polyesters, polycaprolactones, polyvinyl acetals, epoxies, ketones, modified resins and blends thereof, and cross-linked products thereof; Or the like. These may be used alone or in combination of two or more.

  If the thickness of the receptor layer is too thin, the reflection density of the thermal transfer image recorded by thermal transfer is lowered, and it becomes difficult to form a good image. On the other hand, if it is too thick, it tends to cause a reduction in image quality such as color bleeding. Therefore, the thickness may be about 1 to 30 μm, preferably about 3 to 10 μm.

  Such a receiving layer preferably contains various releasing agents for the purpose of preventing thermal fusion to the heat-transferred member during image formation. As such a release agent, a known release agent can be appropriately selected and used. For example, various oils such as silicone-based, fluorine-based, and phosphate ester-based materials, surfactants, various fillers such as metal oxides and silica can be used. Among these, it is preferable to use silicone oil. The amount added varies depending on the constituent conditions of the image-receiving layer, but generally it is preferably 1 to 30% by weight.

  EXAMPLES Hereinafter, although an Example is described in detail, this invention is not limited to these Examples.

<Example 1>
First, a heat-resistant slip layer-forming coating liquid-1 having the following composition was prepared, and the coating liquid was applied to one surface of a polyethylene terephthalate film having a thickness of 4.5 μm as a base film and dried. Curing treatment was carried out by heating at 50 ° C. for 24 hours to form a heat-resistant slipping layer having a thickness of 1.0 μm.

<Coating liquid-1 for forming a heat resistant slipping layer>
Acrylic polyol resin (KOH = 150 mgKOH / g, Tg = 37 ° C.)
21 parts by weight tolylene diisocyanate 14 parts by weight (NCO / OH = 1.0)
Butyl stearate 4.1 parts by weight Toluene 42.7 parts by weight Methyl ethyl ketone 18.2 parts by weight

  Moreover, the coating liquid-1 for thermal sublimation transfer layer (thermal transfer layer) formation of the following composition was prepared, the coating liquid was apply | coated to the surface opposite to the surface in which the heat resistant slipping layer of the above-mentioned base film was formed, Thereafter, the film was dried to form a thermal transfer layer having a thickness of 1.0 μm, and the thermal transfer recording medium of Example 1 was produced.

<Coating liquid for forming a heat sublimation transfer layer-1>
Polyvinyl acetal resin (degree of acetalization 85% by weight, degree of polymerization 1300)
4.0 parts by weight tolylene diisocyanate 0.48 parts by weight (NCO / OH = 1.2)
C. I. Solvent Blue 63 5.0 parts by weight Phosphate-based surfactant 0.04 parts by weight Toluene 30 parts by weight Methyl ethyl ketone 60 parts by weight

Next, a foamed polypropylene film (thickness: 50 μm) / adhesive resin layer / coated paper (application amount: 108 g / m ² ) / adhesive resin layer / foamed polypropylene film (thickness: 50 μm) is laminated as a base sheet. Using this laminated film, apply a thin film of receiving layer forming ink having the following composition on one side of the film so that the film thickness after drying is 4 μm, dry, and then age at 45 ° C. for 1 week. As a result, a thermal transfer member with a receiving layer was obtained.

[Receptive layer forming ink]
Vinyl chloride-vinyl acetate copolymer 50 parts Silicone oil 2 parts Methyl ethyl ketone 25 parts Toluene 25 parts

<Example 2>
Other than using the coating liquid-2 for forming a heat sublimation transfer layer using a polyvinyl acetal resin having a polymerization degree of 2000 instead of the polyvinyl acetal resin having a polymerization degree of 1300 used in the coating liquid-1 for forming a heat sublimation transfer layer. Was the same as in Example 1 to obtain a thermal transfer recording medium of Example 2.

<Example 3>
Example 2 except that the coating liquid-3 for forming a heat sublimation transfer layer using silicone oil was used instead of the phosphate ester surfactant used in the coating liquid-2 for forming a heat sublimation transfer layer. Similarly, a thermal transfer recording medium of Example 3 was obtained.

<Example 4>
Instead of the acrylic polyol resin having a hydroxyl value of 150 mgKOH / g and Tg = 37 ° C. used in the coating solution-3 for forming a heat resistant slipping layer, an acrylic polyol resin having a hydroxyl value of 150 mgKOH / g and Tg = 43 ° C. was used. A thermal transfer recording medium of Example 4 was obtained in the same manner as Example 3 except that the coating liquid for forming a sublimation transfer layer-4 was used.

<Example 5>
Instead of the butyl stearate used in the heat-resistant slip layer forming coating solution-4, the same procedure as in Example 4 was conducted except for the coating solution for forming a heat sublimation transfer layer using a phosphate ester surfactant. Thus, a thermal transfer recording medium of Example 5 was obtained.

<Comparative Example 1>
The amount of tolylene diisocyanate used in the coating solution for forming a heat sublimation transfer layer-5 is not 0.18 parts by weight (NCO / OH = 0) but 0.48 parts by weight (NCO / OH = 1.2). The thermal transfer recording medium of Comparative Example 1 was obtained in the same manner as in Example 5 except that it was changed to .3).

<Comparative Example 2>
In the same manner as in Example 5, except that a polyvinyl acetal resin having a polymerization degree of 900 was used instead of the polyvinyl acetal resin having a polymerization degree of 2000 used in the coating liquid for forming a heat sublimation transfer layer-5, Comparative Example 2 A thermal transfer recording medium was obtained.

<Comparative Example 3>
A thermal transfer recording medium of Comparative Example 3 was obtained in the same manner as in Example 5 except that the silicone oil used in the coating liquid for forming a sublimation transfer layer-5 was not added.

<Comparative example 4>
Instead of the acrylic polyol resin having a hydroxyl value of 150 mgKOH / g and Tg = 43 ° C. used in the coating solution for forming a heat resistant slipping layer-5, an acrylic polyol resin having a hydroxyl value of 80 mgKOH / g and Tg = 43 ° C. was used. A thermal transfer recording medium of Comparative Example 5 was obtained in the same manner as Example 4 except for the above.

<Comparative Example 5>
The amount of tolylene diisocyanate used in the coating solution for forming a heat resistant slipping layer-5 is not 5.6 parts by weight (NCO / OH = 0.4) but 14 parts by weight (NCO / OH = 1.0). The thermal transfer recording medium of Comparative Example 5 was obtained in the same manner as in Example 5 except for the above.

<Comparative Example 6>
A thermal transfer recording medium of Comparative Example 6 was obtained in the same manner as in Example 5 except that the phosphate ester surfactant used in the coating solution for forming a heat resistant slipping layer-5 was not added.

  The thermal transfer layer surface of the thermal transfer recording medium obtained as described above and the receiving layer surface of the above-described thermal transfer medium were overlapped, and the dye was transferred using a thermal head to form an image.

  The following evaluation was performed on the obtained image. The results are shown in Table 1. The evaluation criteria are as follows.

(Evaluation criteria)
[State of base film]
◎: No tearing or tearing ○: Tearing or tearing is less than 2% (no effect on subsequent printing)
×: 2% or more torn or tearing (affects subsequent prints)
[Fusion of thermal transfer layer and transferred material]
A: No fusion (no peeling sound during printing)
○: No fusing (with peeling sound during printing)
×: Severe fusing, printing stopped (may affect subsequent printing)
[Fusion of thermal head and heat-resistant slip layer]
○: No fusing ×: Fusing is severe and printing stops (the effect on the subsequent printing)
[State of printed matter]
◎: Good with no defects ×: There are unevenness and streaks

  As described above, the thermal transfer recording medium of the present invention has a strong ribbon strength at the time of printing, and during thermal transfer recording, the thermal transfer layer, the thermal transfer body, the substrate film, and the thermal head are prevented from being fused, and unevenness and streaking are prevented. A good print without omission can be obtained. On the other hand, since the NCO / OH ratio of the thermal transfer recording medium according to Comparative Example 1 was small, the base film was torn or torn and the thermal transfer layer and the thermal transfer body were fused. Further, since the thermal transfer recording medium according to Comparative Example 2 uses a resin having a low degree of polymerization, the base film was torn or torn. Since the silicone oil was not added to the thermal transfer recording medium according to Comparative Example 3, the base film was torn or torn and the thermal transfer layer and the thermal transfer body were fused. Since the thermal transfer recording medium according to Comparative Example 4 uses a resin having a small hydroxyl value, the base film is torn or torn. In the thermal transfer recording medium according to Comparative Example 5, since the NCO / OH ratio was small, the base film was torn or torn, and the thermal head and the heat-resistant slipping layer were fused. In the thermal transfer recording medium according to Comparative Example 6, since no phosphate ester surfactant was added, tearing and tearing of the base film and fusion between the thermal head and the heat resistant slipping layer occurred.

  The thermal transfer recording medium of the present invention is widely used as a recording medium used for monochrome printing such as characters and diagrams, and color printing such as digital camera images or computer graphics images.

DESCRIPTION OF SYMBOLS 1 ... Thermal transfer recording medium 2 ... Base film 3 ... Thermal transfer layer 4 ... Heat-resistant slipping layer

Claims (5)

  A thermal transfer layer having at least a binder resin and a lubricant on one surface of the base film, and at least a heat-resistant slip layer having at least a binder resin and a lubricant on the other surface of the base film. In the recording medium, the binder resin constituting the thermal transfer layer is a reaction product of a polyvinyl acetal resin having a degree of acetalization of 80% by weight or more and a polyvalent isocyanate, and the addition amount of the polyvalent isocyanate is 0.5 by NCO / OH ratio. The binder resin constituting the heat resistant slipping layer is a reaction product of a thermoplastic resin having a hydroxyl value of 100 mgKOH / g or more and a polyvalent isocyanate, and the amount of polyvalent isocyanate added is 0.8 in terms of NCO / OH. The thermal transfer recording medium characterized by the above.   2. The thermal transfer recording medium according to claim 1, wherein the degree of polymerization of the polyvinyl acetal resin constituting the thermal transfer layer is 1500 or more.   The thermal transfer recording medium according to claim 1 or 2, wherein the lubricant constituting the thermal transfer layer is a silicone-based lubricant.   The thermal transfer recording medium according to any one of claims 1 to 3, wherein the thermoplastic resin constituting the heat-resistant slipping layer has a glass transition temperature of 40 ° C or higher.   The thermal transfer recording medium according to any one of claims 1 to 4, wherein the lubricant constituting the heat resistant slipping layer contains a phosphate ester-based surfactant.

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