JPS6372593A - Thermal transfer ink sheet - Google Patents

Abstract

PURPOSE:To obtain good repeated printing property even to low smoothness paper by enhancing the bonding strength of ink to recording paper and reducing the melt viscosity of the ink, by preparing a heat-meltable material from a mixture composed of a wax like compound having an urethane bond and at least two or more materials among fatty acid amide wax, ester wax and fatty acid. CONSTITUTION:In a repeatedly usable thermal transfer ink sheet wherein an intermediate adhesive layer is provided on a base material and a heat-meltable ink layer 23 composed of a coloring material, a filler and a heat-meltable mate rial is provided to said layer 22, the heat-Meltable material is composed of a mixture of a wax like compound having an urethane bond and at least two or more materials among fatty acid amide wax, ester wax and fatty acid. By Using the heat-meltable material as a main component, the melt viscosity of ink can be reduced while the film forming capacity and adhesiveness of the urethane wax is held and good printing can be obtained even on recording paper being poor in surface smoothness.

Description

[Detailed description of the invention] [Table of contents] - Overview - Industrial application field - Conventional technology - Problems to be solved by the invention - Means and effects for solving the problems - Examples - Effects of the invention [Overview] In order to obtain good prints even on recording paper with poor surface smoothness in reusable thermal transfer ink sheets, fatty acids are added to waxy compounds with urethane bonds as heat-melting materials that are solid at room temperature. By adding at least two of amide wax, ester wax, and fatty acid, the adhesion of the ink to recording paper is improved, and the melt viscosity of the ink is reduced, resulting in good repeatability even on low-smooth paper. A thermal transfer ink sheet designed to print.

[Industrial application field]

The present invention is used in recording devices such as thermal transfer printers and facsimiles, and the heat-melting ink is melted by the heat of the thermal head and transferred little by little to the recording paper, allowing the same area to be used many times. The present invention relates to a usable thermal transfer ink sheet.

Since the thermal transfer ink sheets currently available on the market are disposable, there is a demand for a thermal transfer ink sheet that is low in running cost and can be used repeatedly. In addition, with current recording devices, it is necessary to select recording paper with a good surface smoothness (Beck smoothness: 200 seconds or more) in order to obtain good printing.
70 seconds) is desired.

[Conventional technology]

In conventional thermal transfer ink sheets, in order to obtain good printing even on recording paper with poor surface smoothness, the resin component in the ink layer is increased to increase adhesion to the recording paper, and the crosslinking property is increased. There is a known method of transferring images by holding them. Furthermore, in terms of the printing mechanism, we have increased the pressure on the thermal head (or improved the timing and angle of peeling off the ink ribbon and recording paper after transfer), and changed the shape of the thermal head so that the ink ribbon and recording paper are more effective. Attempts have been made to improve the structure by creating a protruding structure that makes contact with the surface.

[Problem that the invention seeks to solve]

In the conventional thermal transfer ink sheet, the ink layer contains a large amount of a resin component with a high melting point, so the sensitivity is low and a large amount of printing energy is required to obtain good printing. This places a heavy burden on the thermal head, posing a problem in terms of its lifespan.

Furthermore, conventional thermal transfer ink sheets have the drawback of high running costs because they cannot be used repeatedly in principle.

Furthermore, there is a problem that it requires a special printing mechanism (conditions) and cannot be applied directly to current printers.

Furthermore, in conventional reusable thermal transfer ink sheets, since the same location is used many times, the thickness of the ink layer is 3 to 5 times thicker than that of a single-use thermal transfer ink sheet. For this reason, the sensitivity is low and a large amount of printing energy is required.Particularly at low temperatures, good printing cannot be obtained unless conditions exceed the thermal head's rating.

In addition, as mentioned above, when printing repeatedly on recording paper with poor surface smoothness, the ink is endowed with resin-like properties such as film-forming ability and adhesiveness.
Furthermore, the melting point and melt viscosity are at about 1, which is high, creating a problem that current thermal heads cannot deal with if the ambient temperature is also taken into consideration.

The present invention has been made in view of the drawbacks of the prior art described above, and an object of the present invention is to provide a thermal transfer ink sheet that enables printing of good quality even on recording paper with poor surface smoothness.

[Means for solving problems]

In order to achieve the above object, in the first invention of the present application, an intermediate adhesive layer is provided on a base material, and a heat-melt ink comprising a coloring material, a filler, and a heat-melt material that is solid at room temperature is provided on the intermediate adhesive layer. In a layered heat transfer ink sheet that can be used repeatedly, the heat-melting material includes a waxy compound having a urethane bond, a fatty acid amide wax, an ester wax,
It is characterized by being a mixture with at least two or more of the three fatty acids.

Further, in the second invention of the present application, an intermediate adhesive layer is provided on the base material, and a heat-melting ink layer consisting of a coloring material, a filler, and a heat-melting material that is solid at room temperature is provided thereon. In the heat transfer ink sheet that can be used, the heat-melting material is characterized by consisting of a wax having at least a urethane bond and a fatty acid whose alkyl group has 14 to 22 carbon atoms.

Furthermore, in the third invention of the present application, an intermediate adhesive layer is provided on the base material, and an ink layer comprising a coloring material, a filler, and a heat-melting material whose main component is a waxy compound having urethane bonds thereon. A reusable thermal transfer ink sheet is characterized in that a plasticizer is added to the ink layer.

[For production]

By using the above-mentioned heat-melting material as the main component, the melt viscosity of the ink can be reduced while maintaining the film-forming ability and adhesive properties of urethane wax, making it suitable for recording paper with poor surface smoothness. You can get good printing results. In addition, the ink composition of the present invention is filled in the gaps in the stone wall-like structure constructed by the filler, and is melted by the heat of the thermal head and gradually oozes out from between the stone walls, making it easy to use repeatedly. It is possible to obtain clear printing without background smearing even during repeated printing.

In addition, by adding a plasticizer, the melt viscosity can be reduced without impairing the film-forming ability and adhesive properties of urethane wax, so sensitivity can be improved, for example,
Even at a low temperature of 0° C., there is no peeling and transfer, and good repeated printing can be obtained on recording paper with poor surface smoothness.

〔Example〕

FIG. 1 is a sectional view of a main part of a thermal transfer ink sheet according to the present invention. For example, on a base material 21 made of a polyester film with a thickness of 6 μm, an intermediate adhesive layer 22 made of a polyester resin and a polyamide resin is provided with a thickness of 3 μm. On this intermediate adhesive layer 22 is a heat-melting ink layer (23) consisting of a coloring material, a filler, and a heat-melting material that is solid at room temperature.
will be established.

On a 6 μm thick polyester film with a heat-resistant treatment layer on the top and back side of the actual spot, an intermediate adhesive layer made of polyester resin and polyamide resin is provided with a thickness of 3 μm, and an ink layer made of the following components is further applied on top of this. A thermal transfer ink sheet having a thickness of approximately 10 μm was prepared.

The thermal transfer ink sheet thus obtained was slit into an 8-width ribbon, and transfer recording was performed using a thermal transfer printer with an applied pulse width of 1.0 ms and an applied energy of 30 mJ/mm. The recording paper used was Xerox paper. (Kishu Paper, type PA4, Beck smoothness 50-70 seconds).Transfer density (Optical Density)
, 0.0. ) of 1.0 or more, and a homogeneous transferred image without white spots was obtained even on Xerox paper. Moreover, even in repeated printing, clear printing without background smearing was obtained.

In this example, instead of Diamond 0-200, erucic acid amide (such as Alflow P-10 manufactured by Nippon Kasei Co., Ltd.), N-stearyl oleic acid amide (such as Nikkaamide SO manufactured by Nippon Kasei Co., Ltd.), ricinoleic acid amide (such as Nippon Kasei Co., Ltd.'s Nickaamide SO), etc. A similar evaluation was conducted using a fatty acid amide wax such as Diamond H (manufactured by Daimichi Co., Ltd.), and as a result, good printing was obtained.

Also, instead of carnauba wax, you can use beeswax, stearyl behenate (manufactured by NOF), and C! Sugar fatty acid ester (manufactured by Dai-Kogyo Seiyaku, Sugar Wax FA-10E
A similar evaluation was conducted using ester waxes such as (e.g.), and good printing was obtained.

Instead of the fatty acid amide wax of Example 1, the fatty acids of myristic acid, valmitic acid, stearic acid, and behenic acid (
(all manufactured by NOF), thermal transfer ink sheets were produced in the same manner. These ink sheets were evaluated in the same manner as in Example 2, and as a result, transfer densities of 1.0 or higher were obtained, and four homogeneous transferred images with no white spots were obtained even on Xerox paper. Moreover, even in repeated printing, clear printing without background smearing was obtained.

1. A thermal transfer ink sheet was prepared using the fatty acid used in Example (2) instead of the ester wax in Example (2), and the same evaluation was conducted. In all combinations, the transfer density was 1.0 or higher, and the homogeneity on Xerox paper was also extremely good.

The transfer characteristics of the thermal transfer ink sheet when neither fatty acid amide wax, ester wax, nor fatty acid are added is that the urethane wax is too sticky, causing white spots in the transferred image and causing problems in terms of homogeneity. was there.

In addition, when each is added individually, the homogeneity on Xerox paper improves, but in the case of ester wax and fatty acid amide wax, peeling and transfer within the ink layer may occur, making it unstable. Met. This is because the melt viscosity of the ink hardly decreases even if ester wax or fatty acid amide wax is added. In the case of fatty acids, the melt viscosity of the ink was lowered, but the transfer density could not be higher than 1.0.

The results of the above Examples and Comparative Examples are summarized in Table 1.

Below is a blank sheet of 11 sheets ■ On a 6 μm thick polyester film with a heat-resistant treatment layer on the back side, a 3 μm thick intermediate adhesive layer made of polyester resin and polyamide resin is applied, and on top of this, the following ingredients are added. Narui: About 10 layers! A thermal transfer ink sheet having a thickness of m was prepared.

The fatty acids are myristic acid whose main component is CI4, palmitic acid whose main component is CI6, stearic acid whose main component is C16 and CI6, and behenic acid whose main component is C2□.

These fatty acids may be used alone or in combination. In this example, transfer recording was carried out using a thermal transfer printer using a thermal transfer ink ribbon (slit 8 widths) with an applied pulse width of 1 ms and an applied energy of 30 mJ/mm''.The recording paper used was , Xerox paper (Kishu Paper, type PA
4, Bekk smoothness of 50 to 70 seconds). No matter which fatty acid is used, the transfer density (Optical Densit
y, 0.0. ) of 1.0 or more, and a homogeneous transferred image without white spots was obtained even on Xerox paper.

When fatty acids were not added, the homogeneity on Xerox paper decreased, and peeling and transfer may occur within the ink layer, resulting in instability.

When the number of carbon atoms in the alkyl group of fatty acid is less than CIz (
For example, because the melting point of CI2 (lauric acid, the main component of which is lauric acid) is as low as 50° C. or lower, background smearing occurs due to rough transfer during printing.

When the number of carbon atoms in the alkyl group of the fatty acid is C24 or more, (
For example, lignoceric acid), on the other hand, had a disadvantage that the melting point was too high and the energy required for recording increased.

FIG. 2 shows the melt viscosity characteristics of an ink that supports the effects of the present invention, using stearic acid as an example. By adding fatty acids, the viscosity, especially at low temperatures, is significantly reduced.

On a 6 μm thick polyester film with a heat-resistant treated layer on the back side of the actual square, an intermediate adhesive layer of 3 μm thick made of polyester resin and polyamide resin is provided, and on top of this is an ink layer made of the following components. A thermal transfer ink sheet having a thickness of about 10 μm was prepared.

Color Materials: Kayascent Black 1 part by weight (Nippon Kayaku) Sox: Urethane wax 2 parts by weight (Nippon Oil & Fats) Diamond 0-200 0.5 parts by weight (Nippon Kasei) Paraffin wax 1 part by weight (Nippon Haro) ) Plasticizer: (manufactured by Daihe Kagaku) 0.3 parts by weight Plasticizers include dioctyl phthalate and diisodecyl phthalate as phthalate esters, dioctyl azelate dibutyl sebacate as fatty acid ester, and dibutyl maleate as maleic acid/fumarate ester. Thermal transfer ink sheets were prepared using dioctyl fumarate, and tributyl phosphate and trioctyl phosphate as orthophosphoric acid esters. These were slit into ribbons with a width of 81 layers, and applied using a thermal transfer printer with a width of 1 m.
Transfer recording was performed with an applied energy of 30 mJ/vn''.The recording paper used was Xerox paper (Kishu Paper, type PA4, Beck smoothness 50-70 seconds).The ambient temperature was 5-40°C. As a result of the transfer recording shown below, no matter which plasticizer was used, good prints were obtained without peeling or transfer at low temperatures.Also, even at high temperatures, there was no background smudge due to repeated printing, and the prints were clear. Printing was obtained.

FIG. 3 shows the temperature characteristics when triptyl phosphate is added. It can be seen that the characteristics at low temperatures are significantly improved compared to the case without addition.

FIG. 4 shows the dependence on the amount of tributyl phosphate added. When the amount of tributyl phosphate is less than 3tm, t% of the total ink components,
There is no additive effect. Furthermore, as the amount added was increased, the transfer density decreased, but the homogeneity of the transferred image on recording paper with poor surface smoothness improved. However, the amount added is 15w
If it exceeds t%, a problem arises in storage stability at high temperatures.

Therefore, the preferable addition amount is 3 to 15 wt%.

〔Effect of the invention〕

According to the present invention, the excellent properties of urethane wax (
Since the melt viscosity of the ink can be reduced without impairing the film-forming ability and adhesion properties, good printing can be obtained even on recording paper with poor surface smoothness. Moreover, even in repeated printing, clear printing without background smearing can be obtained.

Furthermore, by adding a plasticizer, the melt viscosity of the ink can be reduced without impairing the excellent film-forming ability and adhesive properties of urethane wax. Print is obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main part of the thermal transfer ink sheet according to the present invention, Fig. 2 is a melt viscosity characteristic diagram showing the effect of Example
4 and 4 are a temperature characteristic diagram showing the effect of Example (2) and a graph showing the transfer density with respect to the amount of plasticizer added, respectively. 21... Substrate, 22... Intermediate adhesive layer,
23...Thermofusible ink layer. Fig. 1 is a cross-sectional view of the main parts explaining the present invention in detail Fig. 1 is a diagram of melt viscosity characteristics Fig. 3 is a diagram of transfer density versus temperature

Claims (1)

[Claims] 1. An intermediate adhesive layer (22) is provided on a base material (21), and a heat-melt ink layer ( 23) In the reusable thermal transfer ink sheet provided with 23), the heat-melting material is a mixture of a waxy compound having a urethane bond and at least two of fatty acid amide wax, ester wax, and fatty acid. A thermal transfer ink sheet characterized by being a mixture. 2. The thermal transfer ink sheet according to claim 1, wherein the alkyl group of the fatty acid has 14 to 22 carbon atoms. 3. An intermediate adhesive layer (22) is provided on the base material (21), and an ink layer (
23) A reusable thermal transfer ink sheet, characterized in that a plasticizer is added to the ink layer. 4. The thermal transfer ink sheet according to claim 3, wherein the plasticizer comprises at least one of phthalic acid ester, fatty acid ester, maleic acid/fumaric acid ester, and orthophosphoric acid ester. 5. The thermal transfer ink sheet according to claim 3 or 4, wherein the plasticizer is added in an amount of 3 to 15 wt% based on the total ink components.