JP5645117B2 - Thermal transfer sheet - Google Patents

Description

  The present invention relates to a thermal transfer sheet used in a thermal transfer type printer, and more particularly to a thermal transfer sheet that is suitable for a card application and has excellent plasticizer resistance of a printed matter.

  In recent years, the use of thermal transfer sheets (ribbons) has been rapidly spreading in order to perform printing or image formation by a printer equipped with a thermal head. Since such a thermal transfer recording method can easily and quickly form various images on a print medium, it is widely used for printed materials with a relatively small number of copies such as ID cards, PC image printing, and digital camera printing. Has been.

  When a full-color gradation image such as a facial photograph is preferable as a thermal transfer sheet used for such an application, yellow, magenta, and cyan as an ink layer on a continuous base film, and necessary Accordingly, a black colorant layer in which a large number of colorant layers are repeatedly formed in the surface order is used.

  For example, when creating an ID card such as an identification card using such a thermal transfer sheet, a gradation image such as a face photograph can be formed quickly and easily. There is a problem that the durability and weather resistance are inferior to those in the case of printing. In particular, when directly contacted with a card case, a file sheet, a plastic eraser or the like containing a plasticizer, there has been a problem that the dye of the transferred image is transferred to them or the plasticizer resistance is inferior such that the image itself is blurred.

  Therefore, conventionally, in order to solve such a problem of plasticizer resistance, a specific protective layer is formed on the surface of a transferred image (Patent Document 1).

As described above, the conventional means for improving the plasticizer resistance is mainly the approach from the formation of the protective layer, and there is a limit to the further improvement effect of the printed image quality that depends only on the protective layer. In this respect, the conventional thermal transfer sheet is not always satisfactory.

  The present invention has been made in view of the situation in the prior art described above, and provides a thermal transfer sheet that makes it possible to obtain a printed image with improved plasticizer resistance from a viewpoint different from the formation of a protective layer. It is intended to provide.

（ただし、Ｒ^１は、炭素数１〜６のアルキル基、Ｒ^２は、炭素数１〜６のアルキル基である。）

In order to achieve the above object, the thermal transfer sheet according to the present invention is a thermal transfer sheet in which a dye layer is formed on one surface of a base film, and the yellow dye layer constituting the dye layer is: It comprises a dye represented by the structural formula (1) and the following structural formula (2) in combination.

(However, R ¹ is an alkyl group having 1 to 6 carbon atoms, and R ² is an alkyl group having 1 to 6 carbon atoms.)

In a preferred embodiment of the present invention, the dye represented by the structural formula (1) is composed of a compound represented by the following structural formula (3).

  Furthermore, the thermal transfer sheet according to the present invention includes a thermal transfer sheet in which the dye layer is composed of yellow, magenta, cyan, and optionally a black dye layer.

    In addition, the present invention includes a printed material obtained by forming an image by the thermal transfer method using the above thermal transfer sheet.

  In a preferred embodiment of the present invention, the printed matter is in the form of a card.

  As will be understood from the results of Examples and Comparative Examples described later, according to the present invention, it is possible to obtain a printed matter that is excellent in image density to be formed and particularly excellent in plasticizer resistance.

  Hereinafter, preferred embodiments of the thermal transfer sheet of the present invention will be described.

  The thermal transfer sheet according to the present invention basically has a dye layer formed on one surface of a substrate film and a back slip layer formed on the other surface as desired.

  As the substrate film, conventionally used substrates are used and are not particularly limited. That is, in addition to polyethylene terephthalate (PET) conventionally used as a base film for a thermal transfer sheet, polycarbonate, polyethylene, polystyrene, polypropylene, polyimide, polyvinyl alcohol film, cellophane, cellulose derivatives such as cellulose acetate, polyethylene film, Resin films such as polyvinyl chloride film, nylon film, polyimide film, and ionomer film can be used. The thickness of a base film is 0.5-50 micrometers normally, Preferably it is the range of 4-7 micrometers.

  As the dye layer, conventionally used dye compositions for sublimation transfer and melt transfer can be used except for the yellow dye layer described below, and are not particularly limited. In the present invention, the “dye layer” means not only a layer containing a narrowly defined dye but also a layer containing a colorant containing a usable pigment. The dye layers for yellow, magenta, cyan, and black can be provided in the surface order.

（ただし、Ｒ^１は、炭素数１〜６のアルキル基、さらに好ましくは炭素数１〜３のアルキル基であり、Ｒ^２は、炭素数１〜６のアルキル基、さらに好ましくは炭素数３〜５ のアルキル基である。）

In the present invention, the yellow dye layer constituting the dye layer of the thermal transfer sheet contains a dye represented by the following structural formula (1) and the following structural formula (2) in combination. .

(Wherein, ^{R 1} is an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, ^{R 2} is an alkyl group having 1 to 6 carbon atoms, more preferably 3 carbon 5 alkyl group.)

Furthermore, in a preferred embodiment of the present invention, the dye of the structural formula (1) is composed of a compound represented by the following structural formula (3).

  The dye of the structural formula (1) is excellent in concentration and plasticizer resistance, while the dye of the structural formula (3) is excellent in plasticizer resistance and has a good yellow color. Since these dyes have a relatively low molecular weight and good transferability, they are likely to be dyed on the receiving surface, so that it is presumed that such characteristics are developed.

  Furthermore, since the dye of the structural formula (2) has a higher concentration than the other general dyes and has good ribbon storage stability, it can be stored in the concentration and ribbon storage in combination with the dye of the structural formula (1). It is considered that a good thermal transfer sheet can be obtained in all of properties and plasticizer resistance.

  The thermal transfer sheet according to the present invention includes a thermal transfer sheet in which the dye layer is composed of a dye layer of yellow, magenta, cyan, and optionally black. In addition, as described above, with the exception of the yellow dye layer described above, conventionally used dye compositions for sublimation transfer and melt transfer should be used for the magenta, cyan and black dye layers. There is no particular limitation.

  The mixing ratio of the dye of the above structural formula (1) and the following structural formula (2) is preferably 10 to 70 of the dye of the structural formula (2) with respect to 90 to 30 parts by weight of the dye of the structural formula (1). More preferred is a range of 30 to 60 parts by weight of the dye of the structural formula (2) with respect to 70 to 40 parts by weight of the dye of the structural formula (1).

  If the ratio of the dye of the structural formula (1) is too small, a sufficient effect on the plasticizer resistance cannot be obtained, and conversely, the ratio of the dye of the structural formula (1) is too large or the dye alone is used. Since there is a tendency for the ribbon storage stability and the color density to decrease, it is preferable to combine the dyes of the above structural formula (2) having a higher concentration and good ribbon storage stability in a ratio within the above range.

  In the present invention, in addition to the dyes of the above structural formulas (1) and (2), other known yellow dyes can be additionally added as long as the properties are not affected. As such a yellow dye, quinophthalone D, CI Disperse Yellow 231 and the like can be preferably used.

  Each dye layer including the yellow dye layer usually contains a binder resin in addition to the dye component. A conventionally known resin can be used as the binder resin carrying the dye, and is not particularly limited. For example, cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, cidroxypropyl cellulose, methyl cellulose, cellulose acetate, etc., vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, polyacrylamide, polyester, etc. are used. Among these, a cellulose resin, an acetal resin, a butyral resin, and a polyester resin are preferable, and a butyral resin and an acetal resin are particularly preferable in terms of improving characteristics.

  The dye layer is prepared by applying a coating composition prepared by dissolving or dispersing in a suitable solvent, which is obtained by adding the necessary additives to the above-mentioned dye and binder resin, on a base sheet by a known means, and drying. Can be formed.

The proportion of the yellow dye in the dye layer is preferably 30 to 70% by weight, more preferably about 40 to 60% by weight. The coating amount of the dye layer is preferably 0.3 to 1.0 g / m ² , more preferably about 0.4 to 0.8 g / m ² .

  In addition, the present invention includes a printed material obtained by forming an image by the thermal transfer method using the above thermal transfer sheet.

  In the present invention, if desired, a back slipping layer can be formed on the other surface of the base film, that is, the surface (back surface) opposite to the surface on which the dye layer is formed. For such a back slipping layer, a conventionally known material can be appropriately used, and is not particularly limited.

  According to the thermal transfer sheet of the present invention, it is possible to form an image with excellent printing density and particularly excellent plasticizer resistance, and it is particularly suitable for image formation on a card-type thermal transfer medium.

  Hereinafter, the present invention will be described more specifically based on examples of the present invention and comparative examples.

Example 1
A yellow dye layer having the following composition was formed on the other surface of a PET film (4.5 μm thick) having a heat-resistant slip layer formed on one surface. This yellow dye layer was formed by coating with a wire bar so that the coating amount was 0.7 g / m 2 and then drying at 80 ° C. for 2 minutes.

(Composition for yellow dye layer)
Dye of structural formula (2) (CI Disperse Yellow 201) 2 parts by weight Dye of structural formula (3) 2 parts by weight Butyral resin 3.5 parts by weight Methyl ethyl ketone 46.25 parts by weight Toluene 46.25 parts by weight

  Using the obtained thermal transfer sheet, it was printed on a card made of vinyl chloride. After the yellow dye image was formed, the magenta layer, cyan layer, and OP layer of SP-55 media manufactured by Data Card were transferred to the image surface.

  The thermal transfer sheet was subjected to a storage stability test, a density measurement of the obtained printed material, and a plasticizer resistance test. The measurement conditions are as follows.

Printer used and printing conditions:
Printing was performed under the conditions of printing speed: 2 ms / line, printing energy: 0.20 mj / dot, using a thermal transfer printer capable of 256 gradation control equipped with a thermal head having a linear density of 300 dpi.

Print density measurement:
It was measured with Gretag Macbeth GRETAG Spectrolino (D65 light source, viewing angle 2 °).

Concentration standard:
The density standard is less than 2.30 or more than 2.30. If it is 2.30 or more, the concentration is sufficiently high.

Thermal transfer sheet storage stability test:
Store thermal transfer sheet at 50 ° C for 1 week. A gradation image with a gradation of 0 to 255 is printed on the PVC card after storage. If the density change near OD = 1.0 is within 20% before storage and after storage, it is evaluated as ◯.

Plasticizer resistance test:
This is a test based on "ANSI INCITS 322-2002 5.14 Plasticizer Induced Migration". The printed matter of the example and the comparative example is subjected to a 300-bend bending test on the back and front of the major axis and minor axis, respectively, and protected. Decreasing the adhesiveness of the layer, dripping DOP onto the surface of the printed material, coating the entire surface with a bar coater, then covering the surface with a PET film and storing it in a 40 ° C environment for 4 hours, the effect of DOP on the printed material It was confirmed. Evaluation was performed by microscopic observation of the surface of the printed material, and evaluation was performed according to the following evaluation criteria.

Plasticizer resistance test evaluation criteria:
The plasticizer resistance test evaluation criteria were evaluated in the following five stages.
5: Neither lifting nor peeling of the protective layer occurred at the place where the bending test was performed.
4: The protective layer is slightly lifted or peeled off at the place where the bending test was performed.
3: About half of the places where the bending test was performed, the protective layer was lifted and peeled off.
2: The protective layer is lifted and peeled over the entire area where the bending test was performed.
If it was 4 or more, it evaluated that it had sufficient plasticizer resistance.

Example 2
A yellow dye layer having the following composition was formed on the other surface of a PET film (4.5 μm thick) having a heat-resistant slip layer formed on one surface. This yellow dye layer was formed by coating with a wire bar so that the coating amount was 0.7 g / m ² and then drying at 80 ° C. for 2 minutes.

(Composition for yellow dye layer)
Dye of structural formula (2) 2 parts by weight Dye of structural formula (3) 3 parts by weight Butyral resin 3.5 parts by weight Methyl ethyl ketone 46.25 parts by weight Toluene 46.25 parts by weight Each evaluation test was carried out in the same manner as in Example 1. I went.

Comparative Example 1
A yellow dye layer having the following composition was formed on the other surface of a PET film (4.5 μm thick) having a heat-resistant slip layer formed on one surface. This yellow dye layer was formed by coating with a wire bar so that the coating amount was 0.7 g / m ² and then drying at 80 ° C. for 2 minutes.

(Composition for yellow dye layer)
CI Disperse Yellow 201 2 parts by weight Dye of the following structural formula (CI Disperse Yellow 231) 2 parts by weight

Butyral resin 3.5 parts by weight Methyl ethyl ketone 46.25 parts by weight Toluene 46.25 parts by weight

  The evaluation test was performed in the same manner as in Example 1.

Comparative Example 2
A yellow dye layer having the following composition was formed on the other surface of a PET film (4.5 μm thick) having a heat-resistant slip layer formed on one surface. This yellow dye layer was formed by coating with a wire bar so that the coating amount was 0.7 g / m ² and then drying at 80 ° C. for 2 minutes.

(Composition for yellow dye layer)
Dye of the following structural formula (Kinophthalone D) 2 parts by weight

Dye of the following structural formula (CI Disperse Yellow 231) 2 parts by weight

Butyral resin 3.5 parts by weight Methyl ethyl ketone 46.25 parts by weight Toluene 46.25 parts by weight

Comparative Example 3
A yellow dye layer having the following composition was formed on the other surface of a PET film (4.5 μm thick) having a heat-resistant slip layer formed on one surface. This yellow dye layer was formed by coating with a wire bar so that the coating amount was 0.7 g / m ² and then drying at 80 ° C. for 2 minutes.

(Composition for yellow dye layer)
Dye of the following structural formula (CI Disperse Yellow 141) 2 parts by weight

Dye of structural formula (3) 2 parts by weight Butyral resin 3.5 parts by weight Methyl ethyl ketone 46.25 parts by weight Toluene 46.25 parts by weight

(result)
The evaluation results of the above examples and comparative examples are shown below.

  As can be seen from the evaluation results, there was no significant difference in the storage stability of the thermal transfer sheet between the examples and the comparative examples, but the concentration and the plasticizer resistance were measured when the thermal transfer sheet of the present invention was used. A clear improvement effect was observed.

Claims (4)

In the thermal transfer sheet in which a dye layer is formed on one side of the base film,
A thermal transfer sheet, wherein the yellow dye layer constituting the dye layer contains a dye represented by the following structural formula (3) and the following structural formula (2) in combination.

  The thermal transfer sheet according to claim 1, wherein the dye layer comprises a yellow, magenta, cyan, and optionally black dye layer. Using the thermal transfer sheet according to claim 1 or 2, a printed matter formed by image formation by a thermal transfer method ,
At least a dye represented by the structural formula (3) and the structural formula (2) is transferred from the thermal transfer sheet .   The printed matter according to claim 3, wherein the printed matter is in a card form.