JP2001301343A - Thermal transfer recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer recording medium which is excellent in thermal transferability especially at high speed printing and can give a high resolution printed image. SOLUTION: This thermal transfer recording medium comprises a support, on which a release layer mainly composed of wax is provided, and an ink layer containing a colorant provided thereon. A wax having an ester bond and / or a urethane bond having one endothermic peak represented by a differential heat curve showing an endothermic amount per unit time on a vertical axis, and having a half width of the endothermic peak of 20 ° C. or more. A thermal transfer recording medium characterized by being contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium, and more particularly, to a thermal transfer recording medium which is excellent in thermal transferability particularly at high speed printing and can provide a high-resolution printed image.

[0002]

2. Description of the Related Art A thermal transfer recording method using heat as recording energy and using plain paper and a thermal transfer recording medium (ink ribbon) is a widely used recording method since a printed image with excellent contrast can be obtained. At present, one of the thermal transfer recording apparatuses used is a thermal separation type recording apparatus. The hot-peeling type recording device is a recording device equipped with an edge type line thermal head, and is a device effectively used for a label printer or the like because high-speed recording is possible. As a thermal transfer recording medium suitable for this thermal release recording, a thermal transfer recording layer in which a release layer which can be easily released when heated and a high cohesive force ink layer which does not completely dissolve and become softened when heated, are laminated on a support. A medium has been proposed (JP-A-8-80679, JP-A-8-1507).
No. 85, JP-A-8-207462). Conventionally, a low melting point material such as wax has been used for the release layer in consideration of transferability in a short heating time such as high-speed recording. Among low-melting point materials, it has been attempted to use a wax or the like having a sharp melting property and a cohesive property in order to improve the delicateness of a printed image and the background stain at the time of printing (JP-A-2-310088). No.). However, this melting property, the thermal transfer recording medium provided with a release layer using a wax or the like whose cohesiveness is sharp, when a hot release recording is performed, due to its sharp melting property, solidification property,
Fluidity was exhibited only in an extremely narrow temperature range, and there was a severe limitation on the temperature range in which hot peeling was possible. Also,
Since the temperature range in which heat is absorbed is narrow, heat from the thermal head diffuses in the horizontal direction with respect to the head, and there is a disadvantage that it is difficult to obtain a sharp image.

[0003]

SUMMARY OF THE INVENTION The present invention provides a thermal transfer recording medium which solves the above-mentioned conventional drawbacks and has excellent thermal transferability particularly at high-speed printing and can provide a high-resolution printed image. That is the task.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies focusing on the release layer in order to solve the above-mentioned problems, and as a result, by including a specific wax in the release layer, it is possible to achieve high-speed printing. It has been found that a thermal transfer recording medium having excellent thermal transferability and capable of giving a high-resolution printed image can be obtained, and the present invention has been completed based on this finding. That is, according to the present invention, there is provided a thermal transfer recording medium in which a release layer mainly composed of wax is provided on a support, and an ink layer containing a colorant is provided thereon. The endothermic peak represented by a differential heat curve showing the temperature on the axis and the amount of heat absorbed per unit time on the vertical axis is 1
And a wax having an ester bond and / or a urethane bond having a half width of the endothermic peak of not less than 20 ° C. is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a thermal transfer recording medium in which a release layer mainly composed of wax is provided on a support, and an ink layer containing a colorant is provided thereon. As the support, a known resin film or paper is used, for example,
Examples include resin films having relatively good heat resistance, such as polyesters such as polyethylene terephthalate, polycarbonate, triacetyl cellulose, nylon, and polyimide, cellophane, and sulfuric acid paper.

In the present invention, if necessary, a protective layer may be provided on the back surface of the support. The protective layer is a layer for protecting the support from high temperatures when heat is applied by the thermal head.In addition to thermoplastic resins and thermosetting resins having high heat resistance, ultraviolet curable resins and electron beam curable resins are also used. It can be formed using. Suitable resins for forming the protective layer include a fluorine resin, a silicon resin, a polyimide resin, an epoxy resin, a phenol resin, a melamine resin, and the like. These resins may be used in the form of a film. In addition, since the heat resistance of the support can be significantly improved by providing the protective layer, it is possible to use a material which has been considered to be unsuitable in the past for the support.

[0007] The release layer is a layer provided to facilitate the separation of the ink layer and the support when the ink layer is melt-transferred. This release layer is formed mainly of wax. Further, in addition to the wax, the release layer is provided with isoprene rubber, butadiene rubber, ethylene propylene rubber, butyl rubber, in order to impart flexibility of the layer and adhesion to the support.
Unvulcanized rubbers such as nitrile rubber may be added, and ethylene-vinyl acetate copolymer, polyolefin-based resin such as ethylene-ethyl acrylate copolymer, and others, polyamide-based resin, polyurethane resin, polyester-based resin, Polyacrylic resin, cellulose resin, polyvinyl alcohol resin, petroleum resin, phenolic resin,
A resin such as a polystyrene resin may be added. These can be used in combination as appropriate. The thickness of the release layer is usually from 0.2 to 3.0 μm, preferably from 1.0 to 3.0 μm.
2.0 μm.

[0008] An ink layer containing a colorant is provided on the release layer. This ink layer is formed using a thermoplastic resin and a heat-fusible substance in addition to the colorant, and may have a laminated structure of two or more layers. As the colorant, an organic pigment, an inorganic pigment or a dye is appropriately selected and used in accordance with a desired color tone and concentration. For example, carbon black, disazo yellow, brilliant carmine 6B, lake C, phthalocyanine blue, Kayaset Black KR (Nippon Kayaku), Oil Yellow 3G
(Orient Chemical), Kayaset Red K-BE (Nippon Kayaku), Kayaset Blue KFL (Nippon Kayaku) and the like. The amount of the colorant added is not particularly limited, but is preferably 5 to 50% by weight based on the ink layer, and is preferably 10 to 20% in order not to lower the shearing force excessively.

[0009] The thermoplastic resin is added to improve the shearing force and to impart strength against rubbing of the image, and is preferably a resin capable of exhibiting an adhesive force to a recording medium. Examples of such thermoplastic resins include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyamide, polyester, polyurethane, polyvinyl chloride, various cellulose derivatives, polystyrene, polybutyral, phenolic resin, epoxy resin, and the like. Is mentioned. In particular, an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer is a suitable thermoplastic resin because it greatly contributes to image formation on a low-smoothness recording medium and high-speed printing characteristics. The amount of the thermoplastic resin to be added varies depending on its melting characteristics, but is usually 20 to 90%, preferably 40 to 70% by weight with respect to the ink layer.

The heat-meltable substance added to the ink layer is added for improving the thermal sensitivity. Since the substance is melted when heat is applied and shifts to the recording medium, the melting start temperature is preferably 40 ° C. or higher. Preferably, a wax at 50 to 120 ° C. is used. Examples of such heat-fusible substances include carnauba wax, candelilla wax, rice wax, beeswax, wood wax, whale wax, montan wax, and other natural waxes; paraffin wax, microcrystalline wax, oxidized wax, polyethylene wax, and the like. Synthetic waxes; higher saturated fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid and stearic acid;
Higher saturated alcohols such as stearyl alcohol and behenyl alcohol; higher esters such as fatty acid esters of sorbitan; higher fatty acid amides such as stearic acid amide and oleic acid amide; Among them, it is preferable to use carnauba wax or candelilla wax having a low penetration to increase the strength against rubbing of the image. The addition amount of the heat-fusible substance can be arbitrarily selected depending on the balance with the above resin.
Usually 20 to 90%, preferably 40 to 90% by weight.
~, Usually 10 to 60% by weight, preferably 2 to 60%
0 to 50%.

Further, in order to roughen the surface of the ink layer, polyethylene, silica, alumina, calcium carbonate or the like may be added as a filler. However, when a filler is used, the adhesion may be reduced, and at the same time, the shearing force may be reduced. When a filler is used, the amount of the filler is desirably 10% or less based on the weight of the ink layer. Such an ink layer is provided by being laminated on a support by a hot melt coating method, an aqueous coating method, a coating method using an organic solvent, or the like. The thickness of the entire ink layer is usually set to 0.
It is 1 to 10 μm, preferably 0.5 to 6.0 μm.

According to the present invention, there is provided a thermal transfer recording medium comprising a release layer mainly composed of wax on a support and an ink layer containing a colorant provided thereon. Has one endothermic peak represented by a differential heat curve showing the temperature on the horizontal axis and the amount of heat absorbed per unit time on the vertical axis,
A thermal transfer recording medium containing a wax having an ester bond and / or a urethane bond having a half width of the endothermic peak of 20 ° C. or more. The wax used in the release layer preferably has a maximum endothermic amount per unit time at a temperature of 60 to 75 ° C., and has a penetration specified in JIS K2235 (25 ° C.). It is preferably 6 or less.

The present invention has one endothermic peak represented by a differential heat curve showing the temperature on the horizontal axis and the amount of endotherm per unit time on the vertical axis, and the half-value width of this endothermic peak is 20 ° C. or more. It is characterized by using a wax having a certain ester bond and / or urethane bond. When the half width of the endothermic peak is less than 20 ° C., since the temperature range for heat absorption is narrow, heat from the thermal head diffuses in the horizontal direction with respect to the head, making it difficult to obtain a sharp image. On the other hand, when the half width of the endothermic peak is 20 ° C. or more, the heat from the thermal head can be absorbed in a wide temperature range, so that a sharp image can be obtained. The half width of this endothermic peak is 20 ° C. or higher, preferably 40 ° C. or lower.

The wax used here has an ester bond and / or a urethane bond in its molecular structure. By having an ester bond and / or a urethane bond, the adhesive strength to the support is improved, and the phenomenon of transferring even the non-applied portion (tomochi phenomenon) can be suppressed, and a sharp image can be obtained. You can do it.

An ester bond having one endothermic peak represented by a differential heat curve showing the temperature on the abscissa and the amount of endotherm per unit time on the ordinate, and having a half width of the endothermic peak of 20 ° C. or more. Examples of the wax having a urethane bond include a urethane-modified natural wax or synthetic wax and an esterified product of a higher alcohol. FIG. 1 is a diagram showing a differential heat curve of the wax.

These waxes have a maximum endothermic amount per unit time represented by a differential thermal curve of 60 to 60 ° C.
What is 75 degreeC is preferable. When the temperature is lower than 60 ° C., the obtained printed image has poor heat resistance. When the temperature exceeds 75 ° C., sufficient fluidity is not exhibited particularly in a short heating time such as high-speed recording, and good transferability cannot be obtained. Not so desirable. In addition, as these waxes, JIS
K 2235 (25 ° C.) having a specified penetration of 6 or less is preferred. If the penetration exceeds 6, when it is sandwiched between the thermal head and the platen roller together with the recording medium, it deforms into a concave shape, and heat is diffused in the horizontal direction with respect to the head by applying heat. It is not desirable because it is difficult to obtain a sharp image.

The amount of the wax contained in the release layer is as follows:
It is usually 50 to 100%, preferably 80 to 100%, based on the weight of the release layer. If the content of the wax is less than 50%, the adhesive strength to the support at the time of the melt transfer is increased, and sufficient release property cannot be obtained.

[0018]

(Release layer)

 Wax [HAD6160 (manufactured by Nippon Seiro)] 100 parts Half-width of endothermic peak 20 ° C Temperature at which endothermic peak shows maximum value 68 ° C Penetration at 25 ° C 5 [Ink layer] Carbon black 20 parts Ethylene vinyl acetate copolymer Coalescence 40 parts Terpene resin 15 parts Carnauba wax 25 parts

Example 2 A thermal transfer recording medium was produced in the same manner as in Example 1 except that the release layer had the following composition. [Release layer] Wax [Parakol 6160 (manufactured by Nippon Seiwa)] 100 parts Half-width of endothermic peak 20 ° C Temperature at which endothermic peak shows maximum value 71 ° C Penetration at 25 ° C 6

Comparative Example 1 A thermal transfer recording medium was produced in the same manner as in Example 1 except that the release layer had the following composition. [Release layer] Wax [FP-14 (manufactured by Nippon Seika)] 100 parts Half-width of endothermic peak 18 ° C Temperature at which endothermic peak shows maximum value 70 ° C Penetration at 25 ° C 8

Comparative Example 2 A thermal transfer recording medium was produced in the same manner as in Example 1 except that the release layer had the following composition. [Release layer] Wax [weissen 252C (manufactured by Nippon Seiro)] 100 parts Half-width of endothermic peak 16 ° C Temperature at which endothermic peak shows maximum value 66 ° C Penetration at 25 ° C 6

Comparative Example 3 A thermal transfer recording medium was produced in the same manner as in Example 1 except that the release layer had the following composition. [Release layer] Wax [Candelilla wax No.1 (manufactured by Nippon Wax) 100 parts Half-width of endothermic peak 8 ° C Temperature at which endothermic peak shows maximum value 65 ° C Penetration at 25 ° C 1

Comparative Example 4 A thermal transfer recording medium was produced in the same manner as in Example 1 except that the release layer had the following composition. [Release layer] Wax [HNP-10 (manufactured by Nippon Seiro)] 100 parts Half-width of endothermic peak 5 ° C Temperature at which endothermic peak shows maximum value 75 ° C Penetration at 25 ° C 6

Comparative Example 5 A thermal transfer recording medium was produced in the same manner as in Example 1 except that the release layer had the following composition. [Release layer] Wax [HNP-1 (manufactured by Nippon Seiro)] 100 parts Half-width of endothermic peak 5 ° C Temperature at which endothermic peak shows maximum value 65 ° C Penetration at 25 ° C 9

[Evaluation of Thermal Transfer Recording Medium] The thermal transfer recording medium of the example and the comparative example was mounted on a printer equipped with an edge type line thermal head (peeling distance of the thermal head 200 μm), and the printing speed was 300 mm / s. And 500 mm / s, applied energy 0.11 mj / dot
Then, a printing test was performed using a recording medium as a polypropylene film. Each thermal transfer recording medium was evaluated from the barcode reading rate (%) of the obtained image. The barcode reading rate is based on the SymbolTech
nologirs, Inc. Laser Check L
Using C-2811, the laser was scanned 100 times, and the number of readings out of which was expressed as a percentage. In other words, when the reading rate is 100%, it is shown that, when the laser is scanned 100 times, it is possible to read 100 times, which indicates that the barcode is clear. Table 1 shows the evaluation results.

[Table 1]

[0026]

According to the present invention, there is provided a thermal transfer recording medium which is excellent in thermal transferability particularly at the time of high-speed printing and can provide a high-resolution printed image. The contribution to the field is very large.

[Brief description of the drawings]

FIG. 1 is a view showing a differential heat curve of a wax used in the present invention.

Continued on the front page (72) Inventor Mitsuru Naruse 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H111 AA12 AA26 AA33 BA07 BA54 BA63 BA76

Claims (3)

[Claims] 1. A thermal transfer recording medium comprising a support, on which a release layer mainly composed of wax is provided, and an ink layer containing a colorant provided thereon. Having one endothermic peak represented by a differential heat curve showing the amount of heat absorbed per unit time on the vertical axis, and having an ester bond and / or urethane bond whose half-value width of the endothermic peak is 20 ° C. or more. A thermal transfer recording medium comprising: 2. The thermal transfer recording medium according to claim 1, wherein the wax has a temperature of 60 to 75 ° C. as a temperature showing a maximum value of the heat absorption per unit time. 3. The wax according to JIS K 2235.
The thermal transfer recording medium according to claim 1, having a penetration of 6 or less as a prescribed penetration at (25 ° C.).