JP2006103319A - Thermal transfer recording medium and thermal transfer recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal transfer recording medium which can be transferred by a low energy when printing is performed by a thermal transfer printer, and has the transferred image with excellent reproducibility and fastness of the image, and a thermal transfer recording method using the thermal transfer recording medium. <P>SOLUTION: The thermal transfer recording medium comprises a substrate, a releasing layer laminated on the substrate and comprising a wax as a main component, and an ink layer laminated on the releasing layer and comprising a coloring agent and a saturated polyester resin. The thermal transfer recording medium is characterized by that the saturated polyester resin is a resin synthesized by using an acid component with tri- or more valences, and the number-average molecular weight of the saturated polyester resin is at least 300 and less than 1,000. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal transfer recording medium and a thermal transfer recording method.

  When forming images such as distribution labels and rated nameplates by thermal transfer, printing energy is required to transfer the ink provided on the thermal transfer sheet when forming images on paper, film, etc. to be transferred. is there. The required amount of printing energy varies depending on the image density or the type or material of the transfer target. Further, when the surface of the target paper or film is rough, particularly when the printing energy is insufficient, the image may be lost or the image density may be reduced. On the other hand, applying a large amount of printing energy is advantageous in terms of transfer to a rough surface, but has disadvantages such as significantly reducing the thermal head life of the thermal transfer printer and increasing power consumption. In recent years, there is a large demand for printing a large amount of information in a limited space. For this purpose, small characters and figures must be accurately reproduced. If excessive printing energy is applied, the characters and figures are crushed. It becomes unreadable. In addition, labels used for logistics and rating nameplates must be able to withstand friction, heat, and chemicals with this label attached, so images must be robust. The thermal transfer recording medium has a problem that a clear image can be formed with a small printing energy and it is impossible to maintain the robustness of the image.

  Conventionally, as a technique capable of printing with high sensitivity, there are a number of known techniques in which a wax is contained in an ink layer as a main component to melt at low energy. Although this method is widely known, so-called image fastness such as scratch resistance, heat resistance and chemical resistance is poor. On the other hand, a thermal transfer sheet in which the ink layer is mainly composed of a resin is excellent in image fastness, but has a problem in that it does not melt at low energy and thermal sensitivity is deteriorated.

  For this reason, an example in which a polyester resin having excellent transfer characteristics is used for a label typified by a PET film has been conventionally known particularly for a thermal transfer sheet mainly composed of a resin.

  For example, Patent Document 1 discloses a technique in which a polyester resin having a glass transition point of 4 to 80 degrees and a number average molecular weight of 5,000 to 25000 is contained in a monomer composition having a sulfonic acid metal base; A technology that includes a polyester resin using an ethylene oxide adduct as a monomer; Patent Document 3 discloses a technology that uses a polyester resin having a glass transition point of 50 to 100 degrees and a number average molecular weight of 1000 to 10,000; Techniques for containing two or more kinds of polyester resins having different number average molecular weights are disclosed. Moreover, the technique etc. which prescribe | regulate the solubility to a solvent are known as improving chemical resistance specially (refer patent document 5).

However, the thermal transfer sheet composed mainly of the above-mentioned resin has a technique for extremely lowering the molecular weight because the thermal sensitivity is still inferior to that of the thermal transfer sheet mainly composed of wax because the image fastness is improved. It is known (see Patent Document 6). This technology lowers the molecular weight and improves melting characteristics, so it has excellent transferability at low energy, but it has the problem that heat reproducibility makes fine lines, fine characters and figures reproducible, and thermal sensitivity It has been difficult to achieve both image reproducibility and image robustness.
Japanese Patent Laid-Open No. 10-95172 JP-A-10-230682 JP 2003-89276 A JP 2003-103946 A JP 2001-171233 A Japanese Patent Publication No. 4-34957

  The present invention provides a thermal transfer recording medium capable of obtaining a transfer image excellent in reproducibility and robustness that can be transferred with low energy when printing with a thermal transfer printer, and a thermal transfer recording method using such a thermal transfer recording medium. For the purpose.

  The present invention can solve the above problems. Specifically, the following thermal transfer recording medium, thermal transfer recording method, and recording medium can be obtained.

  The invention according to claim 1 is an ink containing a support; a release layer mainly composed of wax laminated on the support; and a colorant and a saturated polyester resin laminated on the release layer. The saturated polyester resin is a resin synthesized using a trivalent or higher acid component, and the number average molecular weight of the saturated polyester resin is 300 or more and less than 1000. A thermal transfer recording medium is provided. As a result, it is possible to improve the melting characteristics and form an image with high sensitivity, and by containing a polyfunctional acid component, it is possible to suppress thermal diffusion and to create a thermal transfer recording medium excellent in image reproducibility. .

  In addition to the above, the present invention can further improve the scratch resistance and heat resistance by containing at least one of a lubricant such as wax, more preferably a polyolefin wax and an oxidized polyolefin wax, in the ink layer. .

  In the present invention, for the purpose of further improving thermal sensitivity and image reproducibility, it is more effective to include a polyolefin wax as a component of the release layer.

  Moreover, it is preferable that the glass transition point of the saturated polyester resin which concerns on this invention is 10-50 degreeC. Accordingly, in addition to the above, it is possible to provide a thermal transfer recording medium that does not cause blocking and prevents a decrease in thermal sensitivity.

  On the other hand, an invention according to claim 6 is characterized in that the thermal transfer recording medium according to any one of claims 1 to 5 is transferred to a transfer medium using a printer having a line-type thermal head. A thermal transfer recording method is provided. Thereby, it is possible to provide a thermal transfer recording method excellent in image reproducibility.

  The line-type thermal head is preferably an end face head. Thereby, it can be transferred to a thick transfer object used for an IC card or a tag.

  Moreover, it is preferable that the transfer target used in the above-described thermal transfer recording method is a film or paper. As a result, a transfer image having excellent thermal sensitivity and durability can be obtained.

  According to the present invention, a transfer image having high sensitivity and excellent image reproducibility can be obtained on a general-purpose transfer target, and the transfer image has high friction resistance and chemical resistance. A thermal transfer recording method using a medium can be obtained.

1. Support The thermal transfer recording medium used in the present invention can use a known support having a thickness of about 3 μm to 10 μm, and examples of the support material include polyester, polycarbonate, polyimide, polyamide, and polystyrene. , Polysulfone, polypropylene, polyethylene, cellulose acetate, and the like, and films in which these are laminated. In the present invention, the material for the support is not limited thereto.

2. Release Layer In the thermal transfer recording medium according to the present invention, a release layer mainly composed of wax is laminated on the above support. This release layer improves the peelability between the support and the thermal transfer layer at the time of printing. When heated with a thermal head, the release layer melts into a low-viscosity liquid. It is configured so that the layer is easily cut near the interface. Further, the release layer has an effect of blocking the heat-sensitive transfer layer after image formation, and can withstand physical impact such as smearing and washing. Natural waxes such as beeswax, whale wax, wood wax, rice bran wax, carnauba wax, candelilla wax, montan wax, shellac wax; paraffin wax, microcrystalline wax, ester wax, Known waxes including synthetic waxes such as polyethylene wax, oxidized paraffin wax, oxidized polyethylene wax, ozokerite, ceresin, and α-olefin derivatives can be used. Among these, a polyolefin wax, preferably a polyethylene wax, is preferably used in order to improve releasability from the support and to facilitate transfer when heat is applied.

  The release layer may be added with a small amount of a resin that serves as a viscosity reducing agent in order to prevent falling off or improve layer coatability. For this purpose, an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer may be added. A polymer or the like is used.

  In addition, in order to improve the adhesion between the thermal transfer recording medium and the transferred material by giving the release layer elasticity, isoprene rubber, butadiene rubber, ethylene propylene rubber, butyl rubber, nitrile rubber, styrene-butadiene rubber, etc. Rubbers and known thermoplastic resins may be added. These additives are optimally added to such an extent that the meltability and releasability of the wax are not impaired, that is, about 0 to 20% of the entire release layer.

When a synthetic wax such as polyolefin is used to create a release layer, since the compound is a single material, a dispersion layer coating solution is prepared by dispersing these waxes in an organic solvent. When drying after the process, drying is performed at a temperature within a range of 5 ° C. higher than the melting start temperature of the wax used and 10 ° C. higher than the melting point of the wax used, so that a part of the wax used (low molecular weight) is dissolved. The portion having a large particle size is in the form of particles, and it is possible to form a uniform layer having excellent ink layer coating properties. When dried at a temperature of 10 ° C. or higher than the melting point of the wax used, the amount of wax dissolved increases, and the ink layer coating liquid applied thereon cannot be uniformly applied. The thickness of the release layer is preferably as thin as possible from the viewpoint of heat conduction. However, if it is too thin, the release property and the barrier property cannot be expressed. ^{m 2} ~3.0g / m ^2, it is preferably formed as a ^{1.2g / m 2 ~2.0g / m 2} .

3. Ink layer 3-1. Colorant The thermal transfer recording medium according to the present invention is constituted by laminating an ink layer on the above release layer. Also, a known colorant can be introduced into this ink layer. Examples of the colorant include carbon black, azo dyes and pigments, phthalocyanine, quinacridone, anthraquinone, perylene, quinophthalone, aniline black, titanium oxide, and zinc. Commonly used inorganic pigments and organic dyes such as white and chromium oxide can be used. In the present invention, the material of the colorant is not limited to these, but among these, carbon black is particularly preferable.

3-2. Saturated polyester resin As the main component of the ink layer used in the present invention, a saturated polyester resin is used as the carrier in addition to the above-described colorant. In the present invention, the saturated polyester resin is a compound obtained by synthesizing an acid component such as a polyvalent carboxylic acid and a polyhydric alcohol component by a polycondensation reaction. In the present invention, as the acid component, aliphatic carboxylic acids such as adipic acid, sebacic acid, succinic acid, azelaic acid, dodecanedioic acid and dimer acid; alicyclic carboxylic acids such as cyclohexanedicarboxylic acid and decalindicarboxylic acid; In addition to divalent carboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, hexahydrophthalic acid and maleic acid, trivalent carboxylic acids such as trimellitic acid, and tetravalent such as pyromellitic acid. It is characterized by containing a monovalent carboxylic acid. By including these trivalent or higher acid components, the resin skeleton has a branched structure and image reproducibility can be improved while having excellent thermal sensitivity.

  As alcohol components, ethylene glycol, neopentyl glycol, butyl glycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol, orthoxylene glycol, paraxylene glycol, 1,4-phenylene glycol and bisphenol A and These ethylene oxide adducts and the like are included.

  The saturated polyester resin in the present invention may be a homopolymer obtained by polymerizing only one kind of carboxylic acid and glycol, or may be a copolymer obtained by polymerizing two or more kinds of carboxylic acid and glycol. Part or all of the homopolymer and copolymer molecules may be cross-linked or not cross-linked. The glycol component is preferably ethylene glycol or neopentyl glycol. At this time, by using a short-chain glycol component typified by ethylene glycol as the main component as the glycol component, the layer aggregation becomes dense and the friction resistance and chemical resistance can be further improved. The carboxylic acid component may be substituted with a polar group such as sulfonic acid.

  Although the manufacturing method of saturated polyester resin can mention well-known dehydration condensation reaction, it is not limited to this.

  The saturated polyester resin in the present invention preferably has a number average molecular weight of 300 or more and less than 1000 from the viewpoint of achieving both thermal sensitivity and image reproducibility. If the molecular weight is less than 300, synthesis is difficult if a trifunctional or higher functional acid component is included, and if it is 1000 or more, the thermal sensitivity is lowered. In order to provide image fastness, a high molecular weight resin may be used. However, the higher the polymer, the lower the thermal sensitivity. The glass transition point of the polyester resin synthesized as described above is in the range of 10 to 50 degrees, more preferably 30 to 50 degrees. In such a range, the performance as a thermal transfer recording medium is good. If the glass transition point is less than 10 degrees, sticking or so-called blocking that occurs during storage tends to occur, and if it exceeds 50 degrees, the thermal sensitivity tends to decrease.

  Examples of resins other than polyester resins include acrylic resins, polyurethane resins, epoxy resins, phenol resins, ketone resins, and ionomer resins.

3-3. Other In the ink layer containing a colorant and a polyester resin, in addition to the polyester resin, a lubricant is introduced for the purpose of giving further image reproducibility and fastness in order to obtain a highly sensitive and clear transfer image on the transfer body. Can do. As the lubricant, silicon compounds such as silicone oil, silica, organopolysiloxane, and known waxes such as beeswax, whale wax, wood wax, rice bran wax, carnauba wax, candelilla wax, montan wax, shellac wax, etc. Wax: Synthetic waxes such as paraffin wax, microcrystalline wax, ester wax, polyethylene wax, oxidized paraffin wax, oxidized polyethylene wax, ozokerite, ceresin, α-olefin derivatives; higher fatty acids, aliphatic esters, aliphatic amides, etc. However, among these, a polyolefin wax or an oxidized polyolefin wax may be added as a hard wax that is hardly affected by heat or a solvent, and the fastness of the image can be improved.

  For the purpose of further improving the chemical resistance against a solvent such as gasoline, various known resins can be added as a second component to the thermal transfer layer. Such resins preferably have excellent qualities such as friction resistance and chemical resistance, but the amount of heat applied by a conventional thermal transfer printer may be insufficient, and it is desirable to add so as not to impair sensitivity. For example, a suitable addition amount of such a resin is 10 to 20% by weight with respect to the thermal transfer layer.

  In addition to the above, various substances (surfactants, etc.) may be added to the thermal transfer layer for the purpose of improving the sensitivity, preventing the ink layer from falling off the support, and improving the dispersibility. Addition in a range that does not reduce the properties is desirable. The above-mentioned heat-sensitive transfer layer forming material is prepared by dispersing or dissolving in a suitable solvent, and preferably using a hot melt coating method, an aqueous coating method, an organic solvent, a gravure coater, a wire bar coater, a roll coater. The layer may be formed by applying a dissolved coating solution on a support and drying by a general coating method.

4). Intermediate layer Further, an intermediate layer may be provided between the release layer and the ink layer for further barrier properties, and a known resin in this technical field can be used in this intermediate layer. However, when the intermediate layer is applied, the thickness of the entire ink surface increases, and therefore application in a range that does not hinder the application of heat to the ink layer efficiently by the thermal head is desirable.

5. Back Layer The thermal transfer recording medium according to the present invention may be provided with a back layer on the surface opposite to the above layers (the surface opposite to the surface on which the ink layer is formed) when viewed from the support. Heat is applied to the opposite surface in accordance with the image by a thermal head or the like during transfer. As the back layer in the present invention, a layer resistant to high heat (heat-resistant protective layer); a layer resistant to friction with a thermal head (sliding protective layer) can be provided as necessary. In addition, a part of the backside of the support is thermally fused to the thermal head, which may cause a phenomenon that damages the transferred image or makes it difficult to transport the thermal transfer recording medium (this phenomenon is called sticking). A layer to prevent (stick prevention layer) can be provided.

  These back layers (the heat-resistant protective layer, the slip-proof protective layer, the stick-preventing layer, etc.) are all thin layers formed of a heat-resistant polymer, and one layer serves two or more functions. Can also be used. Examples of polymers suitable for the formation of the back layer described above are cellulose resin, silicone resin, acrylic resin, epoxy resin, melamine resin, phenol resin, fluororesin, polyimide, aromatic polyamide, polyurethane, aromatic polysulfone. And acetoacetyl group-containing polyvinyl alcohol. In addition, inorganic fine particles such as talc, silica, organopolysiloxane, the above-mentioned lubricants, and the like can be added.

6). Thermal transfer recording method according to the present invention The thermal transfer sheet thus obtained is transferred to a transfer material by a method of melting and transferring the transfer layer by heating and melting such as hot stamp, heat roll, laser irradiation transfer, serial thermal head, line thermal head, etc. Can be made. Among these, a transfer method using a line thermal head that has image sharpness and can be easily transferred with less energy is more preferable. Line-type thermal heads include a flat head with a resistor on the surface of the head (flat head), an end surface head at the head corner (corner head), and a pseudo end surface head at the end of the head surface (near edge head). In particular, a flat head is generally used. The end face head is expected to become mainstream in the future because it can form an image on a thick transfer medium such as various cards and can perform high-speed printing. Among them, the thermal transfer sheet according to the present invention can be printed not only by a flat head but also by an end face head.

7). In addition to the commonly used films such as polyester film, polyolefin film, polyamide film, polystyrene film, synthetic paper, light coated paper, cast A well-known thing can be used about to-be-transferred bodies, such as a card | curd with thickness, such as paper generally used, such as a coated paper and art paper, and PVC * PET. Among these, a film such as a polyester film, a polyolefin film, a synthetic paper, or a paper such as cast coated paper is particularly suitable.

  Examples of the present invention and comparative examples will be specifically described below. Parts are parts by weight unless otherwise indicated. The present invention is not limited to the following examples.

Example 1
First, a release layer-forming coating solution having the following composition was coated on a 4.5 μm thick polyester film (support) and dried at 50 ° C. for 10 seconds to release a dry adhesion amount of about 0.9 g / m ² . A coating liquid for forming an ink layer having the following composition was applied thereon and dried at 60 ° C. for 10 seconds to provide an ink layer having a dry adhesion amount of about 1.5 g / m ² . Next, a 5% toluene solution of a silicone-modified acrylic resin is applied to the support surface opposite to the side on which the ink layer is provided so that the dry adhesion amount is 0.2 g / m ² and dried at 90 ° C. for 10 seconds. Thus, a back layer was provided to produce the thermal transfer recording medium of the present invention.

(Composition of release layer forming coating solution)
Carnauba wax 9 parts Ethylene-vinyl acetate copolymer resin 1 part Toluene 90 parts (Composition of ink layer forming coating solution)
Carbon black 5 parts Saturated polyester resin (A) 15 parts Methyl ethyl ketone (MEK) 80 parts However, the above (A) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components, and ethylene glycol and neopentyl glycol as alcohol components. The number average molecular weight is 700 and Tg is 15 ° C.

Example 2
A release layer and a back layer were formed in the same manner as in Example 1, and an ink layer forming coating solution having the following composition was applied on the release layer in the same manner as in Example 1 to provide an ink layer.

(Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (B) 15 parts Methyl ethyl ketone (MEK) 80 parts However, the above (B) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components, and ethylene glycol and neopentyl glycol as alcohol components. The number average molecular weight is 950 and Tg is 20 ° C.

Example 3
A release layer and a back layer were formed in the same manner as in Example 1, and an ink layer forming coating solution having the following composition was applied on the release layer in the same manner as in Example 1 to provide an ink layer.

(Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (B) 12 parts Montanic acid wax 3 parts Methyl ethyl ketone (MEK) 80 parts However, the above (B) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components and ethylene as alcohol components A resin containing glycol and neopentyl glycol, having a number average molecular weight of 950 and Tg of 20 ° C.

Example 4
A release layer and a back layer were formed in the same manner as in Example 1, and an ink layer forming coating solution having the following composition was applied on the release layer in the same manner as in Example 1 to provide an ink layer.

(Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (B) 12 parts Polyethylene wax 3 parts Methyl ethyl ketone (MEK) 80 parts However, the above (B) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components, and ethylene glycol as alcohol components And neopentyl glycol, the number average molecular weight is 950, and the glass transition point is 20 ° C.

Example 5
A back layer is formed in the same manner as in Example 1, and a release layer forming coating solution having the following composition is applied to the opposite surface, followed by drying at 80 ° C. for 10 seconds, and a dry adhesion amount of about 0.9 g / m ² . A release layer was provided, and an ink layer forming coating solution having the following composition was applied thereon in the same manner as in Example 1 to provide an ink layer.

(Composition of release layer forming coating solution)
Polyethylene wax 9 parts Ethylene-vinyl acetate copolymer resin 1 part Toluene 90 parts (Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (B) 12 parts Polyethylene wax 3 parts Methyl ethyl ketone (MEK) 80 parts However, the above (B) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components, and as alcohol components A resin containing ethylene glycol and neopentyl glycol, having a number average molecular weight of 950 and Tg of 20 ° C.

Example 6
A back layer is formed in the same manner as in Example 1, and a release layer forming coating solution having the same composition as in Example 5 is applied to the opposite surface, followed by drying at 80 ° C. for 10 seconds, and a dry adhesion amount of about 1. A release layer of 5 g / m ² was provided, and an ink layer forming coating solution having the following composition was applied thereon by the same method as in Example 1 to provide an ink layer.

(Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (B) 12 parts Polyethylene wax 3 parts Methyl ethyl ketone (MEK) 80 parts However, the above (B) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components, and as alcohol components A resin containing ethylene glycol and neopentyl glycol, having a number average molecular weight of 950 and Tg of 20 ° C.

Example 7
A back layer is formed in the same manner as in Example 1, and a release layer forming coating solution having the following composition is applied to the opposite surface, followed by drying at 80 ° C. for 10 seconds, and a dry adhesion amount of about 0.9 g / m ² . A release layer was provided, and an ink layer forming coating solution having the following composition was applied thereon in the same manner as in Example 1 to provide an ink layer.

(Composition of release layer forming coating solution)
Polyethylene wax 9 parts Ethylene-vinyl acetate copolymer resin 1 part Toluene 90 parts (Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (B) 12 parts Polyethylene wax 3 parts Methyl ethyl ketone (MEK) 80 parts However, the above (B) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components, and as alcohol components A resin containing ethylene glycol and neopentyl glycol, having a number average molecular weight of 350 and Tg of 16 ° C.

Comparative Example 1
A release layer is provided on a support (polyester film) in the same manner as in Example 1, and a coating liquid for forming an ink layer having the following composition is applied thereon, dried at 60 ° C. for 10 seconds, and a dry adhesion amount of about An ink layer of 1.5 g / m ² was provided. The back layer was provided in the same manner as in Example 1 to produce the thermal transfer recording medium of the present invention.

(Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (C) 15 parts Methyl ethyl ketone (MEK) 80 parts However, the above (C) is a resin containing terephthalic acid and isophthalic acid as acid components and ethylene glycol and neopentyl glycol as alcohol components. The number average molecular weight is 600 and Tg is 11 ° C.

Comparative Example 2
A release layer was provided on the support (polyester film) in the same manner as in Example 1, and an ink layer-forming coating solution having the following composition was dried at 70 ° C. for 10 seconds for 10 minutes to dry adhesion amount of about 1.5 g / m ^2. The ink layer was provided. The back layer was provided in the same manner as in Example 1 to produce the thermal transfer recording medium of the present invention.

(Composition of coating liquid for ink layer formation)
Carbon black 5 parts Saturated polyester resin (D) 15 parts Methyl ethyl ketone (MEK) 80 parts However, the above (D) contains terephthalic acid, isophthalic acid and trimellitic acid as acid components, and ethylene glycol and neopentyl glycol as alcohol components. The number average molecular weight is 2000 and Tg is 37 ° C.

  Examples 1 to 6 and Comparative Examples 1 and 2 of the thermal transfer recording media produced as described above were transferred to a white polyester film (Lintec LVIP series) and a thermal transfer printer (line type thin film thermal head, DATAMAX I -4308 ・ Printing speed 101.6mm / sec. ・ Dot density 12 lines / mm) 6 dot characters (gothic numbers, alphabets, kanji, and characters) at the minimum printing energy scale that can form 1-dot horizontal ruled lines without fading. (About 2.1 mm in size) was printed. The energy scale transferred in the printing test was evaluated as thermal sensitivity (the smaller the printing energy scale, the better the thermal sensitivity), and the reproducibility of the characters and ruled lines transferred in the printing test was evaluated. Furthermore, the image was rubbed lightly with the tip of a mechanical pencil without a center, and the number of times until the image was chipped was evaluated to determine image robustness. The results are shown in Table 1.

表１から、実施例１・２では、熱感度目盛＋８〜＋１０で罫線が印字できる。実施例３〜６ではさらに画像の堅牢性が向上している。実施例５はさらに熱感度目盛が低く、より低エネルギーで印字できることがわかった。

From Table 1, in Examples 1 and 2, ruled lines can be printed with a thermal sensitivity scale of +8 to +10. In Examples 3 to 6, the fastness of the image is further improved. It was found that Example 5 has a lower thermal sensitivity scale and can be printed with lower energy.

(Evaluation test method)
Thermal sensitivity scale: A density scale (minimum −30 to maximum +30) of a thermal transfer printer manufactured by DATAMAX Co., Ltd. is shown as a guideline for the minimum printing energy that can be normally reproduced without fading of a 1-dot ruled line.

Image reproducibility: The Gothic 6-point kanji characters “Den” and “Made” were printed without being crushed and readable, and the image was crushed and unreadable.
A Gothic 6-point number “1” that can be printed without fading is marked with ◯, and a thing that is faint and cannot be read is marked with ×. The thickness of 1-dot horizontal ruled lines was measured with a microscope, etc., and those that were accurately reproduced without thickness (1 dot: approx. 0.08 mm) were marked with ○, and those with partial or overall weight were marked with ×. .

  Friction resistance: The number of times until an image was chipped by reciprocating and rubbing on the image at an angle of 45 ° and a weight of 40 grams with a nib of a sharpened pen (made of metal) with no core.

Claims (8)

Support;
A wax-based release layer laminated on the support; and an ink layer containing a colorant and a saturated polyester resin laminated on the release layer;
A thermal transfer recording medium comprising:
The saturated polyester resin is a resin synthesized using a trivalent or higher acid component,
The thermal transfer recording medium, wherein the saturated polyester resin has a number average molecular weight of 300 or more and less than 1000.   The thermal transfer recording medium according to claim 1, wherein the ink layer contains a lubricant.   The thermal transfer recording medium according to claim 1, wherein the lubricant is a polyolefin wax and / or an oxidized polyolefin wax.   The thermal transfer recording medium according to any one of claims 1 to 3, wherein the release layer contains a polyolefin-based wax.   5. The thermal transfer recording medium according to claim 1, wherein the glass transition point of the saturated polyester resin is 10 ° C. or more and 50 ° C. or less.   6. A thermal transfer recording method, wherein the thermal transfer recording medium according to claim 1 is transferred to a transfer medium using a printer having a line thermal head.   The thermal transfer recording method according to claim 6, wherein the line-type thermal head is an end face head.   The thermal transfer recording method according to claim 6 or 7, wherein the transfer target is a film or paper.