JP3218602B2 - Thermal transfer recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium capable of clearly recording information such as a bar code pattern on various label papers or tag papers in any printing direction without surface peeling. About.

[0002]

2. Description of the Related Art A printer using a thermal transfer recording system has advantages such as a compact apparatus, easy maintenance, low noise, and the like. Therefore, it is widely used in label printers and word processors in recent years. It has become. Among them, a thermal transfer recording medium provided with a heat-fusible ink layer composed of a colorant and a wax on a substrate is used, and at the time of recording, the heat-fusible ink layer of the thermal transfer recording medium is heated and melted to transfer a recording paper or the like. The type of transferring to a body (hot-melt transfer recording method) is widely used.

On the other hand, for such a thermal transfer recording medium, it is possible to cope with an increase in the speed of a printer.
There is a need to improve print quality. For example,
When recording barcodes on label paper with a label printer, as a thermal transfer recording medium, it is necessary to be able to accurately record black bars of barcodes in a predetermined width and length, and to print on various types of label paper. It is required that the barcode can be recorded and that the printed barcode does not drop due to abrasion (abrasion resistance).

For this reason, thermal transfer recording media have been improved. For example, in order to improve the abrasion resistance, a heat-fusible ink layer is added to a coloring agent and a wax, and a heat-fusible resin having a high cohesive force is also used. It is also conceivable to form by using a release layer made of a hot-melt resin between the base material and the hot-melt ink layer, and this release layer functions as an overcoat layer of a transferred image after recording. (Japanese Patent Application Laid-Open No. Sho 62-30991 and Japanese Patent Application Laid-Open No. 1-978)
No. 4 publication) (hereinafter referred to as a first thermal transfer recording medium).

On the other hand, when a large amount of a heat-fusible resin having a high cohesive force is used, as in the first thermal transfer recording medium, the transferred image becomes tough and the abrasion resistance is improved. With the amount of heat applied by (1), the ink layer softens but does not melt. Therefore, when the transfer object has a smooth surface such as polyester or synthetic paper, the transfer can be performed by a certain degree of adhesiveness due to softening, but the transfer object is generally used for barcode printing. Coated paper (coating amount 10-2
5 g / m ² ) and lightweight coated paper (coating amount 5 to 10 g / m ² )
In the case where the surface is not smooth, as in the case of, for example, the heat-fusible ink layer is not melted and permeated into the transfer object, the transfer cannot be performed satisfactorily, resulting in voids (white spots without printing). Will be noticeable).

Therefore, the heat-fusible resin is contained in the heat-fusible ink layer in the form of fine particles or domains, whereby the heat-fusible ink layer is sufficiently melted in the heating section to enable transfer to coated paper. At the same time, the heat-fusible ink layer is prevented from melting in the non-heated part, the heat-fusible ink layer is easily cut at the boundary between the heated part and the non-heated part, and the transferability is improved. It has been proposed to improve the abrasion resistance of the ink layer (JP-A-62-16968).
No. 6, JP-A-63-45091, JP-A-63-45091
-98491) (hereinafter, referred to as a second thermal transfer recording medium).

[0007]

However, in both the first thermal transfer recording medium and the second thermal transfer recording medium, in addition to the original portion to be recorded, the other portions are thermally transferred in a foil shape. There is a problem of planar separation (so-called tailing) in which the toner is dropped and transferred from the non-reactive ink layer.
For example, as shown in FIG.
When the bar code is recorded in the bar code 2, each bar of the obtained bar code 2 has a tailing portion 2b in addition to the original bar 2a.

[0008] Such planar separation generally occurs as follows. That is, as shown in FIG. 4, a thermal transfer recording medium 5 composed of a base material 3 and a heat-fusible ink layer 4 is overlaid so that the heat-fusible ink layer 4 is in contact with the transfer target 1 such as coated paper. A part 4a of the heat-meltable ink layer 4 is transferred while heating the thermal transfer recording medium 5 and the transfer-receiving body 1 in the direction of the arrow with respect to the Samar head 6 by heating from the substrate 3 side with the Samar head 6 of the printer. (FIG. 4A), even after the heat generation application signal to the Samar head 6 is turned off, a considerable amount of residual heat remains in the Samar head 6, so that the heat located in the rear of the thermal transfer recording medium 5 in the moving direction is Heat is also transmitted to a portion 4b of the fusible ink layer 4 which should not be transferred, and the portion 4b is also in a semi-molten or molten state (FIG. 4).
(B)). This semi-molten or molten portion 4b is
The adhesive strength to the substrate 3 is weak. Therefore, when the thermal transfer recording medium 5 is peeled off from the transfer object 1, this portion 4b is also transferred to the transfer object 1 in addition to the original transfer portion 4a, and in addition to the original transfer image 2a, the jagged surface separation A portion (tailing portion) 2b is formed (FIG. 4C).

[0009] Such surface peeling is caused by the fact that the heat-fusible resin contains fine particles or domains in the heat-fusible ink layer, and the heat-fusible ink layer breaks at the boundary between the heated part and the non-heated part. This also occurs in the above-described second thermal transfer recording medium which has been considered easy. That is, in the second conventional thermal transfer recording medium, a resin that becomes compatible with a heat-meltable substance such as a surrounding wax by heating is used as a resin contained in a fine particle state or in a domain. When heated by the head, as in the case shown in FIG. 4 (b), in the original transfer portion and the portion behind it, the particles or domains are fused to each other and the grain boundaries or domains are dissolved, so that a semi-molten or molten state is obtained. , And the hot-melt ink layer cannot be cut at the boundary between the original heated portion and the non-heated portion. Therefore, when the thermal transfer recording medium is peeled off from the transfer target, unnecessary portions are transferred in addition to the original transfer portions, and a tailing portion is formed.

Further, in this case, since the grain boundaries or domains of the heat-fusible resin are eliminated and transferred, as a result, the heat-fusible resin having a high cohesive force is uniformly contained in the heat-fusible ink layer. As in the case of the conventional thermal transfer recording medium, the viscosity of the heat-fusible ink layer at the time of transfer increases, and there is also a problem that the transferability decreases.

The present invention has been made to solve the above-mentioned problems of the prior art, and is intended to transfer information such as a bar code pattern to label paper or tag paper of various properties in an arbitrary printing direction. An object of the present invention is to provide a thermal transfer recording medium that enables clear recording without surface peeling and improves the scratch resistance of the transferred recording.

[0012]

Means for Solving the Problems The present inventors use a specific resin incompatible with wax as a hot-melt resin when the hot-melt resin is contained in the hot-melt ink layer as a domain. By this, it has been found that, without causing surface peeling, it is possible to obtain a good transferability by lowering the melt viscosity at the time of transfer, and it is possible to further improve the abrasion resistance of the image after transfer. Was completed.

That is, the present invention relates to a thermal transfer recording medium having a heat-fusible ink layer containing a heat-fusible resin, a wax, a softener and a colorant on a substrate, wherein the heat-fusible ink layer is a resin. It is provided on the substrate via a primer layer formed from the class, hot-melt resin, Hiai溶wax
Which indicates a softening point of 120 to 140 ° C by the ring and ball method.
-Provided is a thermal transfer recording medium containing an alkylstyrene-based resin and existing as a domain in a heat-fusible ink layer.

Hereinafter, the thermal transfer recording medium of the present invention will be described in detail with reference to the drawings. Note that the same reference numerals in the drawings, including the above-described conventional example, indicate the same or equivalent elements.

FIG. 1 is a sectional view of a thermal transfer recording medium 9 according to a preferred embodiment of the present invention. The thermal transfer recording medium 9 is provided on the base material 3 with the heat-meltable ink layer 4
Further, a heat-resistant lubricating layer 8 is provided on the surface of the substrate 3 opposite to the heat-fusible ink layer 4.

Here, as the substrate 3, those generally used as a substrate of a thermal transfer recording medium can be used, for example, a film sheet such as a polyester film, a polyimide film, a polycarbonate film, or a capacitor paper. Papers can be used.

In the present invention, the primer layer 7 enhances the adhesiveness between the hot-melt ink layer 4 and the base material 3 and enables the hot-melt ink layer 4 to be transferred with lower energy during transfer. Is provided. The primer layer 7 is formed from resins such as polyester, polyurethane, EVA, vinyl chloride-vinyl acetate copolymer, epoxy resin, and ethyl cellulose.

The hot-melt ink layer 4 is formed mainly of a hot-melt resin composed of wax, an α-alkylstyrene-based resin incompatible with wax, a softener, and a colorant.
It has a configuration characteristic of the present invention.

Here, as the wax, those conventionally used for the heat-fusible ink layer of the thermal transfer recording medium can be used. For example, candelilla wax, carnauba wax, rice wax, wood wax, natural wax such as beeswax, petroleum wax such as paraffin wax, petrolatum, ceresin, montan wax, polyethylene wax, fatty acid, synthetic wax such as acid amide alone or Two or more kinds can be used in combination. It is preferable to use a wax having a melting point of 80 ° C. or less. When the melting point of the wax exceeds 80 ° C., it becomes difficult to transfer the toner satisfactorily with an ordinary printer having a printing energy of about 14 mJ / mm ² .

The heat-fusible resin constituting the heat-fusible ink layer 4 together with such a wax has an α-incompatibility with the wax.
-It is formed mainly of an alkylstyrene resin.
The hot-melt resin made of the α-alkylstyrene-based resin exists as a domain in the hot-melt ink layer 4 using wax as a medium.

As such an α-alkylstyrene resin, a homopolymer of α-alkylstyrene such as α-methylstyrene or a copolymer of α-lower alkylstyrene and another monomer is used. For example, a copolymer of α-methylstyrene and vinyl toluene can be suitably used. In this case, as the α-alkylstyrene resin, a single resin or a mixture of two or more resins can be used.

The α-alkylstyrene resin has a softening point of 90 ° C. or higher, especially 100 to 100 ° C. by a ring and ball method (JIS K2531) by appropriately selecting the degree of polymerization.
It is preferable to use one at 140 ° C. It is preferable that the amount of the α-alkylstyrene-based resin used is 5 to 45% by weight based on the entire hot-melt ink layer. When the α-alkylstyrene-based resin is excessively contained in the heat-fusible ink layer, the transferability is reduced, while when the amount is too small, surface peeling occurs at the time of transfer, and the scratch resistance of the transferred image is also reduced. .

The method for causing the heat-fusible resin composed of the α-alkylstyrene-based resin to exist as a domain in the heat-fusible ink layer 4 using wax as a medium is not particularly limited, and can be a conventional method.

As the softening agent to be contained in the hot-melt ink layer 4, oil-like agents such as DOP, linseed oil and oleic acid, and rubber-like agents such as EVA, EEA (ethylene-ethyl acrylate) and SBR can be used. Although it can be used, it is particularly preferable to use EVA, EEA or the like having good compatibility with the wax.

As the coloring agent, those generally used as coloring agents for the heat-fusible ink layer of the thermal transfer recording medium can be used. Various coloring agents such as carbon black and other inorganic pigments, organic pigments and dyes can be used. Can be used. If necessary, a filler such as silica or mica may be used in combination.

In the thermal transfer recording medium 9 of the present invention, the heat-resistant lubricating layer 8 is provided as needed in order to prevent sticking of the substrate 3 and to improve the running property of the thermal transfer recording medium 9. The heat-resistant lubricating layer 8 is formed from a resin having excellent heat resistance such as a silicone resin, a fluororesin, an acryl-silicone resin, a nitrocellulose resin, or a resin obtained by adding a lubricant such as a silicone oil or a fluorine powder to these resins. can do.

The thermal transfer recording medium 9 having each layer as described above can be manufactured according to a conventional method. For example, substrate 3
The composition for a heat-resistant lubricating layer is applied to one side of the base material using a wire bar and dried to form a heat-resistant lubricating layer 8, and the composition for a primer layer is formed on the other side of the substrate 3 using a wire bar or the like. The primer layer 7 is formed by coating and drying the product, and the hot-melt ink is further applied thereon by using a gravure coater and dried to form the hot-melt ink layer 4.

[0028] In the thermal transfer recording medium of the present invention, alpha-alkylstyrene-based resin to be contained as a heat-fusible resin to the heat-fusible ink layer is wax incompatible, the onset
Explanation of the same operation as that at the time of transfer of bright thermal transfer recording medium
FIG. 2 (a thermal transfer recording medium without a primer layer)
As shown in FIG. 4), the wax 11 is present as a medium in the hot-melt ink layer 4 as a domain 11.

As shown in FIG. 2, even when the portion 4b other than the portion to be transferred is heated by the residual heat of the thermal head 6 during the transfer, the domain 11 of the heat-fusible resin made of the α-alkylstyrene resin is Since the wax 10 has a higher softening point than the wax 10, the wax 10 melts at that portion, but the domain 11 does not completely melt. And
In the vicinity of the boundary between the portion 4a to be originally transferred and the other portion 4b, a hot melt made of an α-alkylstyrene-based resin having a high cohesive force in a molten state and a high cohesive force in a non-molten state in the wax 10 having a low cohesive force in a molten state Thus, domains 11 of the conductive resin are present (in the figure, the domains in the semi-molten state and in the molten state are shown by being painted out). Therefore, the hot-melt ink layer 4 maintains a high adhesive strength to the substrate 3.

On the other hand, not only the wax 10 but also the domain 11 of the hot-melt resin composed of an α-alkylstyrene resin is melted in the portion strongly heated as the portion 4a to be originally transferred by the thermal head 6, and the viscosity thereof is reduced. descend. Even in this case, the domain 11 is maintained because the α-alkylstyrene resin is incompatible with the wax.

Therefore, when the thermal transfer recording medium is peeled off from the transfer-receiving member 1 after heating by the thermal head 6, the cut surface x of the thermal fusible ink layer 4 is formed of a domain of the thermal fusible resin composed of an α-alkylstyrene resin. 11 passes through the wax and 10 portions. For this reason, it is possible to suppress the planar separation in which the heat-fusible ink layer 4 is separated from the original transfer portion.

As described above, not only the wax 10 but also the domain 11 of the heat-fusible resin made of the α-alkylstyrene resin is melted in the portion strongly heated by the thermal head 6 as the portion 4a to be originally transferred. , Its viscosity is greatly reduced. Therefore, it is possible to transfer with good print quality not only to a transfer target having a smooth surface but also to a transfer target having various properties, for example, it is possible to accurately print a barcode on coated paper. Become.

Further, since the domains of the heat-fusible resin composed of the α-alkylstyrene-based resin are present in the heat-fusible ink layer transferred to the transfer object, the transferred image has excellent scratch resistance. It will be.

[0034]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto.

Example 1 A polyester resin (Vylon # 200, manufactured by Toyobo Co., Ltd.) containing 10% by weight of MEK was coated on the other surface of a 5 μm-thick polyester film (manufactured by Teijin Limited) having one surface treated on the back side.
The solution was applied using a wire bar to a dry thickness of 0.3 μm, and dried at 110 ° C. to form a primer layer.

Next, an ink solution having the composition shown in Table 1 was prepared, and this ink solution was applied on the primer layer and dried to form an ink layer having a thickness of about 3.5 μm, thereby preparing a thermal transfer recording medium. did.

Examples 2 to 7 and Comparative Examples 1 to 6 Thermal transfer recording media were prepared in the same manner as in Example 1 except that the composition of the ink solution for forming the ink layer was as shown in Table 1. However, in Examples 4 and 5, the thermoplastic resin was used.
Α-methylstyrene / vinyl with a difficulty point of 100 ° C. as fat
It is positioned as a reference example using a toluene copolymer.
It is.

[0038]

[Table 1]

Notes in the table ^* 1 Carnava No. 2, manufactured by Noda Wax Co., Ltd. ^* 2 HNP-10, manufactured by Nippon Seisaku Co., Ltd. ^* 3 α-methylstyrene / vinyltoluene copolymer (softening point 120 ° C.) Picotex 120, manufactured by Rika Hercules Co., Ltd. ^* 4 α-methylstyrene / vinyltoluene copolymer (softening point 100 ° C.), Picotex 100, manufactured by Rika Hercules Co., Ltd. ^* 5 α-methylstyrene polymer (softened Crystallex 5140, manufactured by Rika Hercules Co., Ltd. ^* 6 α-methylstyrene / vinyltoluene copolymer (softening point: 90 ° C.), Picotex LC, Rika Hercules Co., Ltd. ^* 7 Styrene polymer ( Picolastic A75, Rika Hercules Co., Ltd. ^* 8 Styrene polymer (softening point 125 ° C), picostick D125, Rika Hercules ( ^* 9 Terpene resin (softening point 80 ° C), YS resin Px #
800, manufactured by Yasuhara Chemical Co., Ltd. ^* 10 Terpene resin (softening point 115 ° C), YS resin Px
# 1150, manufactured by Yasuhara Chemical Co., Ltd. ^* 11 Ethylene-vinyl acetate copolymer, KA-31, manufactured by Sumitomo Chemical Co., Ltd. ^* 12 Carbon black ^* 13 Barcode label made of coated paper, 1C, FAS
Bar code label made of SON ^* 14 coated paper, C6TB, manufactured by Mitsubishi Paper Mills, Ltd.

(Evaluation) Using the thermal transfer recording media obtained in Examples and Comparative Examples, using a printer having a thermal head (B-30, manufactured by TEC Co., Ltd.), dot density on each of two types of coated paper was measured. 7.6 dots / mm, printing speed 5
Under the condition of 0.4 mm / sec, as shown in FIG.
t pattern (narrow bar: wide bar
= 3: 9) in the serial direction. In addition, the printing energy was set to an energy that allows printing of a barcode width as specified dimensions when a 3: 9 dot pattern of Code 39 is printed in the parallel direction.

With respect to the obtained bar code pattern,
(I) surface peeling, (ii) transferability, (iii) abrasion resistance were evaluated as follows, and (iv) comprehensive evaluation was performed as follows.
The results are shown in Table 1.

(I) Surface peeling The printed Code 39 was measured for deviations from the respective standard widths of the black bar width and the space width (white bar width) using a bar code verifier, and the obtained value was measured. By averaging, a deviation from the standard value of the entire barcode pattern was obtained. This numerical value indicates a deviation from the designated size of the barcode pattern, and becomes larger as the surface peeling increases.

Next, an adhesive tape (Cellotape, made by Nichiban Co., Ltd.) was applied from above the barcode pattern, and the adhesive tape was peeled off from the transfer paper so as to peel off only the planar peeling portion. The deviation of the space width from each standard value was measured using a bar code verifier. Then, a planar peeling value was obtained from the obtained value according to the following equation.

[0044]

## EQU1 ## (Sheet release value) = (deviation from the standard value of the bar width after printing)-(deviation value from the standard value of the bar width after peeling the adhesive tape)

The surface peel value thus obtained is C
In the case of the 3: 9 dot pattern of the mode 39, the deviation from the allowable standard value can be calculated to be ± 136 μm by the following equation. If the deviation is larger than this, a barcode reading error occurs or reading becomes impossible. become.

[0046]

(Tolerance) = ± {4 (N−2 / 3) · X} / 27 (where N = (wide bar) / (narrow)
bar), X represents the set narrow bar width)

The peeling values obtained for the examples and comparative examples were evaluated according to the following four grades according to their magnitudes. The evaluation results are shown in Table 1.

Rank Surface peel value ◎: less than 10 μm ：: 10 μm or more and less than 50 μm Δ: 50 μm or more and less than 100 μm ×: 100 μm or more

(Ii) Transferability The transfer state of the barcode pattern was visually observed. The case where the transfer state was very good was indicated by ◎, the case where the transfer state was good was indicated by ○, the case where the transfer state was not preferable was indicated by △, and the case where the transfer state was very unfavorable was indicated by ×.

(Iii) Abrasion resistance Using a friction tester for dye fastness (JIS LO823), a cotton fabric and printed matter were brought into surface contact with a load of 200 g, and the loaded portion was reciprocated 100 times to contaminate the cotton fabric. The degree was observed. The case where the degree of contamination of the cotton cloth was low and very good was indicated by ◎, the case where it was good was indicated by ○, the case where it was not preferable was indicated by △, and the case where it was not very preferable was indicated by ×.

(Iv) Comprehensive Evaluation A bar indicates that there is no possibility of erroneous reading or inability to read the bar code and the transferability and the abrasion resistance of the printed matter are good. (I) to (iii)
If at least one of the evaluation items has x, the overall evaluation is x.

From the results shown in Table 1, it can be seen that the examples of the present invention can print barcodes on coated paper without causing surface peeling, and the printed barcodes have excellent scratch resistance. You can see that it is.

[0053]

According to the thermal transfer recording medium of the present invention, information such as a barcode pattern can be clearly recorded on label paper or tag paper of various properties in any printing direction without surface peeling. And the abrasion resistance of the transferred image is also improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the thermal transfer recording medium of the present invention.

FIG. 2 is an explanatory diagram of an operation at the time of transfer of a thermal transfer recording medium from which a primer layer is omitted .

FIG. 3 is an explanatory diagram of a barcode pattern printed by a conventional thermal transfer recording medium.

FIG. 4 is an explanatory diagram of an operation at the time of transfer of a conventional thermal transfer recording medium.

FIG. 5 is an explanatory diagram of a barcode pattern and its printing direction.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 transfer target 2 bar code 3 base material 4 heat-fusible ink layer 5 thermal transfer recording medium 6 thermal head 7 primer layer 8 heat-resistant lubricating layer 9 thermal transfer recording medium 10 wax 11 heat-fusible resin composed of α-alkylstyrene resin Domain of

Claims (3)

(57) [Claims] 1. A heat transfer recording medium having a heat-fusible ink layer containing a heat-fusible resin, a wax, a softener and a colorant on a substrate, wherein the heat-fusible ink layer is made of a resin. is provided on the substrate via a layer, heat-fusible resin is a Hiai溶wax, ring and ball
A thermal transfer recording medium containing an α-alkylstyrene-based resin having a softening point of 120 to 140 ° C. by a method and existing as a domain in a hot-melt ink layer. 2. The thermal transfer recording medium according to claim 1, wherein the α-alkylstyrene resin is a homopolymer of α-methylstyrene or a copolymer of α-methylstyrene and vinyltoluene. 3. The thermal transfer recording medium according to claim 1, wherein the α-alkylstyrene-based resin is contained in an amount of 5 to 45% by weight based on the entire heat-fusible ink layer.