JP2000025342A - Thermal transfer recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sensitivity as well as printing speed of a thermal transfer recording medium by permitting the employment of low-melting point wax while preventing fluffing and improving resistance to scratching further by improving the cutting of ink upon printing. SOLUTION: A thermal transfer recording medium is provided with a peeling layer, containing the group of wax, and an ink layer, containing ethylene-vinyl acetate copolymer, which are formed sequentially on a substrate. In this case, the ink layer is formed of ink solution, obtained by dispersing and treating an ink composition into organic solvent and applied on the peeling layer. Ethylene-acetate vinyl copolymer, having the value of melt index of 60-1000 is employed as the ethylene-vinyl acetate copolymer contained in the ink layer. Methyl ketone is employed as the organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal transfer recording medium used for a thermal transfer printer, for example.

[0002]

2. Description of the Related Art In recent years, edge head printers have been widely used in thermal transfer printers. The edge head printer is characterized in that it is simple in structure, has a high printing speed, and can cope with a recording medium having a rough surface such as so-called rough paper.

Conventionally, as such a thermal transfer recording medium for an edge head printer, for example, the one shown in FIG. 2 is known. As shown in FIG. 2, in the thermal transfer recording medium 101, an adhesive layer 10
5, a release layer 103 is formed, and a high-viscosity ink layer 104 is formed on the release layer 103. On the other hand, the opposite surface of the base material 102 has a heat-resistant lubricity of 10
Six layers are formed.

Conventionally, to form the ink layer 104 on such a thermal transfer recording medium 101, the ink composition is dissolved using a solvent such as, for example, toluene.

[0005]

However, such a conventional technique has the following problems.
That is, in the case of the conventional thermal transfer recording medium 101, since the ink composition is dissolved using a solvent having a relatively high boiling point such as toluene, the ink composition is dried at a low temperature so as not to affect the release layer 103. As a result, there is a problem that a long time is required for the drying step and a solvent remains in the ink layer 104 after the drying step.

In order to solve such a problem, it is conceivable to dry the ink layer 104 at a high temperature of about 90 ° C. after forming it.
In order to leave No. 3, a high-melting-point wax must be used as the material of the release layer 103, so that the sensitivity and printing speed of the thermal transfer recording medium 101 could not be sufficiently improved.

Further, in the prior art, the ink layer 1
Since a rubber-based material is used as the material of No. 04, there is also a problem that the ink is poorly cut during printing and fuzz is generated.

Further, in the case of the prior art, the resistance to rubbing (rubbing resistance) is not sufficient, and in particular, the rubbing resistance to a film-based transfer material is very poor, and improvement thereof has been desired.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and an object of the present invention is to make it possible to use a wax having a low melting point to thereby improve the sensitivity and printing of a thermal transfer recording medium. The goal is to improve speed.

Another object of the present invention is to provide a thermal transfer recording medium capable of improving the cut of ink at the time of printing to prevent fluffing and improving rub resistance.

[0011]

Means for Solving the Problems The inventors of the present invention have made intensive efforts to solve the above-mentioned problems, and as a result, obtained by dispersing an ethylene-vinyl acetate copolymer having a specific melt index as a binder for an ink layer. It has been found that a thermal transfer recording medium that can solve the above problem can be obtained by using the same, and the present invention has been completed.

The invention according to claim 1, which has been made based on such knowledge, is directed to a thermal transfer recording medium in which a release layer containing waxes and an ink layer containing an ethylene-vinyl acetate copolymer are sequentially formed on a substrate. An ink layer is formed by coating using an ink solution obtained by dispersing the ink composition in an organic solvent, and the above ethylene-vinyl acetate copolymer (EV
The value of the melt index of A) is from 60 to 1,000.

Further, according to the invention of claim 2, in the invention of claim 1, the organic solvent is methyl ethyl ketone (M
EK) as a main solvent.

According to the present invention, an organic solvent (eg, ME
By using EVA dispersed in K), an ink layer can be applied and formed on a low melting point wax, so that printing energy is reduced and sensitivity and printing speed of a thermal transfer recording medium are improved. .

Further, the value of the melt index is 60 to 1
By using an EVA of 000, the cut of the ink at the time of printing is improved, and in particular, the adhesion to the film-based transfer object is improved, and the rub resistance is improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the thermal transfer recording medium according to the present invention will be described below in detail with reference to the drawings. In the thermal transfer recording medium of the present invention, for example, as shown in FIG. 1, a release layer 3 and an ink layer 4 are sequentially formed on one surface side of a substrate 2. A heat-resistant lubricating layer 6 is formed on the other surface side of the substrate 2.

In the present invention, as the substrate 2, those used in conventional thermal transfer recording media can be used.
For example, those made of paper such as condenser paper or parchment paper, polyester film, polyvinyl chloride film,
A plastic material such as a polycarbonate film can be suitably used.

Here, the thickness of the substrate 2 is preferably from 2 to 15 μm, more preferably from 3 to 10 μm, from the viewpoint of the strength and heat conduction of the film.

The release layer 3 of the present invention improves the transferability of the ink layer 4 during thermal transfer, and adheres well to the substrate 2 and the ink layer 4 during normal times (during non-thermal transfer). The layer 4 has a role of preventing the foil from developing.

Examples of the material of the release layer 3 include carnauba wax, candelilla wax, rice wax,
Those containing waxes such as paraffin wax can be used. Here, in order to improve the sensitivity and printing speed of the thermal transfer recording medium, it is preferable to use, for example, a low melting point wax such as candelilla wax as the wax.

From the viewpoint of preventing ink dropping, a thermoplastic elastomer such as polystyrene-polybutylene-polystyrene (SBS) may be added to the above wax.

The thickness of the release layer 3 can be variously selected in consideration of other components such as the material of the base material 2 and the ink layer 4 and the printing conditions. From the viewpoint of quality, it is preferably 0.1 to 3.0 g / m ² .

As the colorant in the ink composition of the ink layer 4 of the present invention, those conventionally used in thermal transfer recording media can be used.
Color pigments and the like can be suitably used.

On the other hand, the ink layer 4 of the present invention comprises ethylene-
It is formed by applying an ink solution containing a vinyl acetate copolymer (EVA) and dispersing the ink composition in an organic solvent.

In the present invention having such a structure, the ink layer 4 is applied and formed using an ink solution obtained by dispersing the ink composition in an organic solvent, so that a wax having a low melting point is used as the material of the release layer 3. Can be used, whereby the printing energy is reduced and the sensitivity and printing speed of the thermal transfer recording medium are improved.

Here, the preferred EVA content is 5% by weight to 80% by weight, more preferably 30% by weight.
~ 80% by weight.

In the case of the present invention, the EVA in the ink layer 4
, The smaller the content, the better the abrasion resistance to smooth paper (mirror-coated paper). On the other hand, the ink layer 4
When the content of EVA is large, the rubbing resistance of the film-based transfer member tends to be improved.

On the other hand, if the content of EVA is less than 5% by weight, the viscosity of the ink layer 4 becomes extremely low. If the content is more than 80% by weight, the coloring agent is hardly dissolved, and the ink layer 4 is hardly dissolved. Has to be formed thicker.

In the case of the present invention, various kinds of organic solvents can be used for dispersing the ink composition, but the drying time of the ink layer 4 is reduced and the effect on the release layer 3 during drying is reduced. In consideration of this, it is preferable to use one having a low boiling point.

An example of such a low-boiling organic solvent is methyl ethyl ketone (MEK).

In order to obtain a dispersion of the above-described ink composition, an organic solvent such as methyl ethyl ketone is added to a predetermined amount of the ink composition, and the mixture is heated to a temperature of, for example, about 70 ° C. to dissolve the ink composition. It is good to cool while stirring with.

On the other hand, in the present invention, it is preferable to use an EVA having a melt index (melt flow index shown in JIS K 6900) of 60 to 1000, and a more preferable EVA melt index is in a range of: , 150-800.

In the present invention, by using EVA having a melt index value of 60 to 1000, the ink can be cut easily during printing to prevent fluffing, and in particular, to adhere to a film-based transfer object. And the rub resistance is improved.

In this case, the smaller the value of the melt index of EVA contained in the ink layer 4, the more the rub resistance against smooth paper tends to be improved.

On the other hand, if the value of the melt index of EVA is less than 60, it is difficult to disperse in an organic solvent, and if it is more than 1000, there is an inconvenience that the abrasion resistance to smooth paper is deteriorated.

[0036]

EXAMPLES Examples of the thermal transfer recording medium according to the present invention will be described in detail below along with comparative examples.

<Example 1> (Preparation of heat-resistant lubricating layer composition) 30 parts by weight of an acrylic-modified silicone resin (US380 manufactured by Toagosei Co., Ltd.) was dissolved using 70 parts by weight of toluene / MEK as a solvent, and the desired heat resistance was obtained. A lubricating layer composition was prepared.

(Preparation of composition for forming release layer) 30 parts by weight of carnauba wax (purified carnauba No. 2 manufactured by Kato Yoko Co., Ltd.)
SBS (ToughTech H-1052 manufactured by Asahi Kasei Corporation) was dissolved using 70 parts by weight of toluene as a solvent to prepare a target release layer forming composition.

(Preparation of Ink Layer Forming Dispersion) 10 parts by weight of EVA (Ultracene 725 manufactured by Tosoh Corporation) having a melt index of 1000 and 90 parts by weight of carbon black (Monarch 120 manufactured by Cabot Corporation) were used as an organic solvent in MEK90. The mixture was heated to a temperature of 70 ° C. to dissolve it by weight, and then cooled while stirring with a stirring device to obtain a target dispersion for forming an ink layer.

(Preparation of Thermal Transfer Recording Medium) The above heat-resistant lubricating layer composition was gravure coated to a thickness of 5.
A heat-resistant lubricating layer was formed on one surface (back surface) of a 0 μm PET (polyethylene terephthalate) film (F5 manufactured by Teijin Limited), and then the solvent was volatilized.

Next, a release layer was formed on the other side (front side) of the PET film by gravure coating using the release layer forming composition, and thereafter, the solvent was volatilized.

Further, using the ink layer forming dispersion liquid,
After an ink layer was formed on the release layer by gravure coating to evaporate the solvent, a curing treatment was performed at a temperature of 50 ° C. for 168 hours to obtain a target thermal transfer recording medium.

Here, the thickness of each layer is set at 0.
1 μm, release layer 2.0 μm, and ink layer 2.0
μm.

Example 2 Example 1 was repeated except that 30 parts by weight of a low melting point wax (Candelilla wax manufactured by Kato Yoko Co., Ltd.) was used instead of carnauba wax as a release layer component.
A thermal transfer recording medium was prepared in the same manner as described above.

Example 3 A thermal transfer recording medium was prepared in the same manner as in Example 1, except that EVA having a melt index value of 60 (MB11 manufactured by Sumitomo Chemical Co., Ltd.) was used as the ink binder.

Example 4 EVA having a melt index value of 60 (MB11 manufactured by Sumitomo Chemical Co., Ltd.) was used as an ink binder, and a low melting point wax (Candelilla wax manufactured by Kato Yoko Co., Ltd.) was used instead of carnauba wax. A thermal transfer recording medium was prepared in the same manner as in Example 1 except that the recording medium was used.

<Comparative Example 1> 5 parts by weight of candelilla wax (Candelilla wax manufactured by Kato Yoko Co., Ltd.), 5 parts by weight of styrene resin (FTR8100 manufactured by Mitsui Petrochemical Co., Ltd.)
5 parts by weight of a styrene-isoprene-styrene copolymer (Clinton D1111 manufactured by Shell Japan Co., Ltd.) and 5 parts by weight of EVA having a melt index value of 1000 (Urlacene 725 manufactured by Tosoh Corporation) were used as an organic solvent in toluene 8
Using 0 parts by weight, the composition was heated to a temperature of 80 ° C. and dissolved to prepare an ink layer forming composition.

Then, under the other conditions, a thermal transfer recording medium was prepared in the same manner as in Example 1.

(Evaluation) The above thermal transfer recording medium was evaluated according to the following evaluation items. Table 1 shows the results.

[0050]

[Table 1]

1. Sensitivity Using a thermal transfer printer (Barcode Printer TTX650 manufactured by AVERY), 12i on PET film
A barcode image was formed at a printing speed of nch / sec.

Then, the sensitivity of the printed matter was visually observed. Table 1 shows the results. Here, a mark that can be transferred with a low energy (standard energy of the above-described printer) is denoted by “○”, and a mark that can be transferred with a high energy (the transfer is possible although the standard energy needs to be applied) is denoted by “△”.

2. Rough paper properties Using the same printer as above, rough paper (Stielo
The rough paper property was evaluated by a barcode image or solid image at a printing speed of 12 inches / sec. Table 1 shows the results. Here, a barcode image or solid image having no whitening is denoted by “○”, and a barcode image or solid image having slight whitening but having practically no problem is denoted by “△”.

3. Rubbing resistance (film) Using a rubbing tester (AB-301 rubbing tester manufactured by Tester Sangyo Co., Ltd.), 1 cm on which predetermined printing was performed
200 g or 800 g for a × 1 cm PET film
The degree of dirt when the weight g was slid back and forth 20 times was visually observed. Table 1 shows the results. Here, "O" indicates that the image has no chipping, "△" indicates that the image has slight chipping but no problem, and "X" indicates that the image cannot be read.

As can be seen from Table 1, EVA is ME
Examples 1 to 3 dispersed in K to form an ink binder
In No. 4, the sensitivity was generally good, and the abrasion resistance to the film was greatly improved. In addition, the cut of the ink during printing was good, and no fluff was generated.

On the other hand, in Comparative Example 1 in which a conventional wax or the like was dissolved in toluene to form an ink binder, the rubbing resistance to the film was very poor, and the ink was not cut well, so that fluffing occurred. did.

<Examples 5 to 8 and Comparative Examples 2 to 4> As shown in Table 2, as an ink binder, the melt index value was 7, 60, 150, 300, 1000, 1
A thermal transfer recording medium was prepared in the same manner as in Example 1 except that EVA 200 and 2500 were used.

The rough paper properties and the abrasion resistance (smooth paper) of Examples 5 to 8 and Comparative Examples 2 to 4 were evaluated by the above-described methods. Table 2 shows the results.

[0059]

[Table 2]

Here, with respect to the rub resistance, "◎" indicates that the image has no chipping, "○" indicates that the image has slight chipping but no problem, and "X" indicates that the image cannot be read. .

As can be understood from Table 2, Examples 5 to 8 using EVA having a melt index value of 60 to 1000 have good rough paper properties and extremely poor rub resistance against smooth paper. Was excellent.

On the other hand, in Comparative Example 2 using EVA having a melt index value of less than 60 (= 7),
Could not be dispersed.

When the value of the melt index is 1000
In Comparative Examples 3 and 4 using a larger (= 1200, 2500) EVA, the rub resistance against smooth paper was deteriorated.

[0064]

As described above, according to the present invention, a wax having a low melting point can be used as the material of the release layer, thereby improving the sensitivity and printing speed of the thermal transfer recording medium. Further, according to the present invention, it is possible to prevent ink fuzz by preventing the ink from being cut during printing, and to significantly improve rub resistance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a thermal transfer recording medium according to the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a conventional thermal transfer recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal transfer recording medium 2 Substrate 3 Release layer 4 Ink layer 6 Heat resistant slip layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Ohara 18 Satsuki-cho, Kanuma-shi, Tochigi Sony Chemical Co., Ltd. 1st factory F-term (reference) 2H111 AA01 AA10 AA20 AA26 AA33 BA03 BA07 BA53 BA63 BA71 DA02

Claims (2)

[Claims] 1. A thermal transfer recording medium in which a release layer containing waxes and an ink layer containing an ethylene-vinyl acetate copolymer are sequentially formed on a substrate, wherein the ink layer is a dispersion treatment of the ink composition in an organic solvent. The ethylene-vinyl acetate copolymer has a melt index of 60 to 1
000. The thermal transfer recording medium, wherein 2. The thermal transfer recording medium according to claim 1, wherein the organic solvent is mainly methyl ethyl ketone.