JPH0361588A - Thermal transfer material and thermal transfer recording method using the same - Google Patents

Abstract

PURPOSE:To prevent rear end contamination in powdery form by setting the content of the oxidation inhibitor in a thermal transfer ink layer to a specific value or less. CONSTITUTION:An oxidation inhibitor is contained in a thermal transfer ink layer in an amount of 150ppm or less. The background staining and rear end powder contamination in double-density recording are extremely closely related to the content of the oxidation inhibitor in the thermal transfer ink layer and markedly developed when the content of the oxidation inhibitor is too much. The thermal transfer ink layer contains at least a heat-meltable binder and a colorant, and 40-80wt.% of a copolymer selected from an ethylene/vinyl acetate copolymer and an ethylene/ethyl acrylate copolymer and 20-60wt.% of wax are contained in the heat-meltable binder. The oxidation inhibitor is a phenolic one and, for example, 2, 6-di-t-butyl-p-cresol is designated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal transfer material used for thermal transfer recording, specifically,
The present invention relates to a thermal transfer material and a thermal transfer recording method that allow good recording to be obtained even if the amount of thermal transfer material used is reduced.

[Conventional technology]

In addition to the general features of thermal recording methods, such as the equipment used is lightweight, compact, noiseless, and has excellent operability and maintainability, the thermal transfer recording method does not require colored processed paper, and it also improves the quality of the recorded image. It has the feature of excellent durability and has been widely used recently.

This thermal transfer recording method uses a thermal transfer material in which a thermal transferable ink layer consisting of a colorant dispersed in a heat-melting binder is coated on a support, which is generally in the form of a sheet. By overlapping the thermally transferable ink layer so that it is in contact with the recording medium, and applying heat from the base material side using a thermal head to transfer the melted ink layer to the recording medium,
A transferred recorded image is formed on a recording medium according to a heat supply shape (pattern).

[Problem that the invention is trying to solve]

In conventional thermal transfer recording, the thermal transfer ink is almost completely transferred from the thermal transfer material to the recording medium with a single application of heat, so it is disposable, has high running costs, and can be kept confidential from the used thermal transfer material. There was also concern that the information would be leaked.

On the other hand, Japanese Patent Application Laid-open No. 57-83471, Japanese Patent Application Laid-open No. 5
Publication No. 8-201686 or Special Publication No. 62-5891
As in Japanese Patent No. 7, a recording method (hereinafter referred to as double-density recording) has been proposed in which the amount of thermal transfer material used is reduced by providing a relative speed between the thermal transfer material and the recording medium. However, this recording method has some problems like the conventional method.

The first problem is that background smudge (unnecessary ink transfer to a recording medium such as paper) occurs.

This occurs because in double-density recording, the thermal transfer material and the recording medium slide, so the ink layer of the thermal transfer material is scratched off the surface of the recording medium and transferred to the entire surface of the recording medium.

As a countermeasure against scumming, Japanese Patent Application Laid-Open No. 178088/1988 proposes a heat-sensitive transfer material in which an overlayer containing no colorant is provided on an ink layer.

The second problem is that unnecessary whisker-like transfer occurs at the end of the transferred ink layer in the head running direction.

This is due to the cohesive force of the thermally transferable ink layer after heat application.

The third problem is dirt on the trailing edge of the recorded image. This is because a powder-like transfer material separated from the recorded image adheres to the rear end of the recorded image.

The present invention was made in view of the above-mentioned circumstances, and it not only prevents background stains and whisker-like transfer even with double-density recording, but also
An object of the present invention is to provide a thermal transfer material and a thermal transfer recording method that prevent staining of the trailing edge of a recorded image.

[Means to solve the problem]

The thermal transfer material of the present invention is formed by providing a thermal transferable ink layer on a support, and is characterized in that the thermal transferable ink layer contains an antioxidant in a content of 150 PPM or less.

Further, the thermal transfer recording method of the present invention includes a thermal transfer ink layer provided on a support, and using a thermal transfer material containing an antioxidant in the thermal transfer ink layer in a content of 150 PPM or less, The recording medium is characterized in that the distance that the thermal transfer material moves relative to the recording head is shorter than the distance that the recording medium moves relative to the recording head.

The present invention will be described below with reference to the drawings.

In addition, in the following description, "%" and "%" representing quantitative ratios are used.
Parts are by weight unless otherwise specified.

The thermal transfer recording method (double-density recording method) using the thermal transfer material of the present invention is, as shown in FIG. By heating with a recording head 3 such as a head, the thermal transferable ink of the thermal transfer material 1 is transferred to the recording medium 2 to obtain a recorded image. The thermal transfer material I and the recording medium 2 are continuously moved in the directions of arrows A and H by the rotation of the capstan roller 12, the pinch roller I3, and the platen roller 11, respectively, and are transferred onto the recording medium 2 one after another. A recording is made. The capstan roller 12 and the pinch roller 13 are operated by a motor 14, and the platen roller 11 is operated by a motor I.
5, respectively. Conveyed thermal transfer material 1
is wound up by a take-up reroller 10 driven by a motor 14. A spring 16 presses the recording head 3 against the platen roller 11 via the thermal transfer material 1 and the recording medium 2.

In FIG. 1, the thermal transfer material l and the recording medium 2 are moving in the same direction, but as shown in FIG. The material 1 and the recording medium 2 may be moved in completely opposite directions.

Now, in this thermal transfer recording method, there is a relative speed between the thermal transfer material 1 and the recording medium 2. In the example shown in FIG. 1, the head 3 does not move, and the thermal transfer material 1 moves slower than the recording medium 2. That is, when comparing the distance that the thermal transfer material l moves and the distance that the recording medium moves within the same time, the moving distance of the thermal transfer material l is shorter. As a result, in this recording method, recording is performed as shown in FIGS. 3 to 6.

As shown in FIG. 3, when the width of the heating element 3a of the recording head 3 in the thermal transfer material feeding direction (arrow A direction) is l, 1
The second heat application is applied to completely unused thermal transfer material 1 at a magnitude of 1 (FIG. 3). In addition, the thermal transfer material l is a support l.
A thermally transferable ink layer 1b is provided on a.

However, when the heat is applied for the second time, the recording medium 2 moves l in the direction of arrow B, while the thermal transfer material 1 moves l in the direction of arrow B, while the thermal transfer material 1 moves l in the direction of arrow B. /N (in Fig. 3, N = 5°N value depends on how many times the same part of the thermal transfer material 1 can be printed), so the thermal transfer material 1 moves by [p - 1/N))
The part shown in FIG. 4 is the part that has already been subjected to heat application once and will be used again (FIG. 4).

When heat is applied continuously in the horizontal direction in this way, only 17N of the heat-sensitive transfer material that receives heat application from the second time onwards is unused, and the rest have already been heat-applied several times in increments of 11N. (Figures 4 to 6). In other words, the thermal transfer material is in the same state as if the same location had been used N times, and moreover, it is moving while rubbing the surface of the recording medium.

In the above example, it is assumed that the thermal transfer material 1 moves by 1/N with respect to the recording head 3 during the second, third, etc. heat application, but the thermal transfer material 1 moves by less than 1 or more than 1/N. If so, the thermal transfer material 1 can be saved. The above N is 2~l
O1 is further preferably 3 to 8. In the above explanation, an example was shown in which the recording head 3 does not move. However, even if the thermal head 3 moves, the moving distances of the thermal transfer material 1 and the recording medium 2 are based on the recording head 3. recording head 3
If the distance from In other words, in the thermal transfer recording method of the present invention, the distance that the thermal transfer material l moves relative to the recording head 3 is shorter than the distance that the recording medium 2 moves relative to the recording head 3 within the same time. .

Now, as is clear from the above explanation, since the thermal transfer material l of the present invention is used while sliding on a recording medium such as paper, the surface portion of the thermal transfer ink layer in contact with the recording medium is likely to fall off. .

If this falling-off occurs when no heat is applied, it will appear as so-called background stains. Furthermore, when heat is applied, that is, when the thermal transfer ink is transferred to the recording medium, stains due to powdery transfer material occur at the rear end of the image area. This latter trailing edge stain is a problem unique to the double-density recording system, which does not occur in conventional thermal recording systems in which the thermal transfer material and the recording medium have no relative speed.

Background stains and trailing edge powder stains in double-density recording are extremely closely related to the antioxidant content in the thermal transfer ink layer, and will become noticeable if the antioxidant content is too high. . In double-density recording, it is preferable to include a resin, such as ethylene-vinyl acetate copolymer, in the ink layer to increase the strength of the ink layer. , it is common to add antioxidants to prevent odor generation. The ethylene vinyl acetate copolymer usually contains 750 to 2000 ppm of antioxidant.

Although the mechanism by which the antioxidant causes dust stains at the trailing edge of recorded images is not clearly understood, it is presumed as follows.

When a thermally transferable ink layer is formed on a support, the thermally transferable ink is melted or dissolved or dispersed in a solvent to form a coating ink; in the former case, it is solidified, and in the latter case, the solvent is evaporated and evaporated.

It is presumed that the antioxidant floats to the surface of the thermally transferable ink layer in the step of forming the thermally transferable ink layer. Therefore, although each ink component should be homogeneous in the thermal transferable ink layer, it is actually in a non-uniform state.
It seems that dust stains on the trailing edge are likely to occur. Powder stains on the trailing edge also occur when the device is left in an environment at a temperature higher than room temperature, for example 60° C., for a period of time.

The heat-sensitive transfer material of the present invention has an antioxidant content of 150 PPM or less, more preferably 1100 PPM or less, in the heat-transferable ink layer.
As shown below, background stains and powder stains at the trailing edge of recorded images are prevented.

The following are commonly used as antioxidants: As a phenolic antioxidant, 2.6-di-t
-Butyl-p-cresol (BHT).

Butylated hydroxyanisole (BHA), 2,6-di-t-butyl-4-ethylphenol, stearyl-β
- monophenolic antioxidants such as (3,5-di-t-butyl-4-hydroxyphenyl)propionate,
2.2'-methylene-bis-(4-methyl-6-t-butylphenol), 2.2'-methylene-bis-(4-ethyl-6-t-butylphenol), 4.4'-thiobis-(3- methyl-6・-4-butylphenol),
4.4'-Butylidene-bis-(3-methyl-6-
Bisphenolic antioxidants such as (t-butylphenol), 1,1.3-)lis-(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3.5-
Trimethyl-2゜4,6-tris(3,5-di-t-
butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate comethane, bis[3°3'-bis(4 '-Hydroxy-3'-t
- Polymeric phenolic antioxidants such as butyric acid coglycol ester (butylphenyl); sulfur-based antioxidants such as dilaurylthiopropionate, similystylthiodipropionate, distearylthiodipropionate, etc. Examples of phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, and 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl) phosphite. , cyclic neopentane tetrarubis (octadecyl phosphite),
Tris(nonyl◆phenyl) phosphite, tris(monononylphenyl) phosphite, tris(dinonylphenyl) phosphite, diisodecylpentaerythritol diphosphite, 9. IO-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3゜5-di-t-butyl-4-hydroxybenzyl)-9゜10-dihydro-9-oxa-1O −
Examples include phosphaphenanthrene-10-oxide, IO-desyloxy9.10-dihydro-9-oxa-10-phosphaphenanthrene, etc. Phenolic antioxidants are particularly useful for preventing discoloration of polyolefins and preventing odor generation. is often used, and B, H, and T are commonly used for polyethylene resins.

Conventionally known plastic films and paper can be used as the support, but since heat is applied to the same location on the base material many times in double-density recording, for example, aromatic polyamide film, polyphenylene sulfide film, polyamide Preferably, materials with high heat resistance such as ether ether ketone and condenser paper are used. In addition, when using polyester film (especially polyethylene terephthalate film, abbreviated as PET film), which has been suitably used in conventional heat-sensitive transfer materials, it is necessary to provide a heat-resistant and slippery material on the surface opposite to the ink surface as a backside treatment. is preferred. The thickness of the base material is preferably 3 to 20 μm, more preferably 4 to 12 μm. As long as the material has high strength and heat resistance, it is also possible to use a material as thin as 3 μm or less. Further, excessively thick materials are not preferable because they have poor thermal conductivity.

The heat-transferable ink layer provided on the support is formed by dispersing a colorant in a heat-melting binder.

As the material used for the heat-melting binder, ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is preferably used as it has film properties and softens/melts well when heat is applied. Ethylene-vinyl acetate copolymer is preferred, and the copolymerization ratio of ethylene and vinyl acetate is 90:10 to 50.
: 50 is good, softening point (ring and ball method) is 70-130℃,
More preferably, an ethylene-vinyl acetate copolymer having a temperature in the range of 85 to 100°C is preferred. The copolymerization ratio of ethylene and ethyl acrylate in the ethylene-ethyl acrylate copolymer is preferably 90:1O to 65:35, and the softening point (ring and ball method) is preferably 85 to 100C, more preferably 70 to 1300C.
Preferably, the temperature is within the range of °C.

If most of the binder is composed of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer, the melt viscosity will increase, the breaking strength of the ink layer will also increase, and the trailing edge of the resulting image will have a whisker-like appearance. . Therefore, in order to adjust the melt viscosity of the ink layer and the breaking strength of the ink layer, it is preferable to mix waxes.

Examples of waxes include natural waxes such as carnauba wax, candelilla wax, rice wax, vegetable waxes such as Japanese wax, mineral waxes such as ceresin wax and montan wax, and derivatives thereof, such as acid derivatives of montan wax. Wax, ester wax, partially saponified ester wax, etc. Animal waxes such as beeswax, spermaceti, and lanolin and their derivatives; and petroleum waxes such as paraffin wax and microcrystalline wax.

Synthetic waxes include polyethylene wax and Fischer-Tropsch wax. Other higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid; higher alcohols such as stearyl alcohol and behenyl alcohol; esters such as sucrose fatty acid ester and sorbitan fatty acid ester; and amides such as oleylamide. , are also available. The above waxes may be used alone or in combination of two or more.

The content of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer in the binder is
40 to 80% by weight, more preferably 45 to 7% by weight based on the binder
0% by weight is preferred. In addition, the wax content is 20
-60% by weight, more preferably 25-50% by weight. If the wax content exceeds 60% by weight, scumming occurs, which is undesirable. Furthermore, it is also possible to add other heat-melting resins as necessary. For example, polyolefin resin, polyamide resin, polyester resin1. Epoxy resin, polyurethane resin, polyacrylic resin, polyvinyl chloride resin, cellulose resin, polyvinyl alcohol resin, petroleum resin, phenol resin, polystyrene resin, vinyl acetate resin, natural rubber, styrene butane Elastomers such as Jen rubber, isoprene rubber, and chloroprene rubber, polyisobutylene, and polybutene can be used.

As a particularly suitable resin to be added, what is generally called a tackifier is effective in firmly adhering the transferred image to the recording medium.

Tackifiers include coumaron indene resin, phenol/formaldehyde resin, polyterpene resin, xylene/formaldehyde resin, polybutene, rosin pentaerythritol ester, rosin glycerin ester, hydrogenated rosin, hydrogenated rosin methyl ester,
One type or a mixture of two or more types selected from hydrogenated rosin triethylene glycol ester, hydrogenated rosin pentaerythritol ester, polymerized rosin ester, aliphatic petroleum resin, alicyclic petroleum resin, synthetic polyterpene, pentagene resin, etc. .

When the binder contains tackifier, the content of tackifier is preferably 5 to 15% by weight, more preferably 7 to 12% by weight, based on the binder.

Examples of colorants include carbon black, nigrosine dye, lamp black, Sudan black SM, Fast Yellow 61 Benzine Niro Pigment Niro,
Indofast Orange, Irgazine Red, Varanitroaniline Red, Toluidine Red, Carmine F
B, Permanent Bordeaux FRR, Pigment Orange R1 Linole Red 2G, Lake Red C10
- Damin FB.

Rhodamine B Lake, Methyl Violet B Lake, Phthalocyanine Blue, Pigment Blue Brilliant Green B1 Phthalocyanine Green, Oil Yellow GG, Zapon Fast Yellow CGG.

Kayaset Y963, Sumiplast Yellow GG, Zabon Fast Orange RR, Oil Scarlet, Sumiplast Orange G1 Orazur Brown G1 Pomelo Fast Scarlet CG, Eisen Spiron Red F4R,
One or a mixture of two or more of conventionally known colorants such as Fastgen Blue 5007, Sudan Blue, and Oil Peacock Blue are used.

The amount of coloring material contained in the ink layer is preferably 1 to 50% by weight, more preferably 5 to 35% by weight, based on the entire ink layer. If the amount of colorant is less than 1% by weight, the density of the recorded image will be extremely low, and if it exceeds 50% by weight, problems such as increased recording energy or decreased transferability to the recording medium will occur. Undesirable.

In producing the thermal transfer material of the present invention, a binder material selected from the above-mentioned viewpoints is dissolved in an organic solvent such as toluene, methyl ethyl ketone, isopropyl alcohol, methanol, xylene, etc., and a coloring material is mixed therein, and then the binder material is mixed with a coloring material and then processed using a sand mill or the like. It can be sufficiently dispersed using a dispersing machine, and then applied onto a substrate using a coating method such as a bar code or gravure coating. Alternatively, the resin may be heated to a temperature above its softening point to disperse the coloring material, and then applied using a so-called hot melt coating. Furthermore, the resin or colorant may be applied as an aqueous emulsion by adding a dispersant such as a surfactant.

When applying ink to the substrate, apply a single color (e.g. black) to the entire surface.
A single-color thermal transfer material can be obtained by applying colored ink. In addition, multiple color ink layers (for example, cyan ink, magenta ink, yellow ink,
It is also possible to obtain a thermal transfer material capable of multicolor recording by repeatedly applying different colors (such as blue ink, green ink, or red ink) and recording so that the colors overlap during printing.

The thickness of the ink layer varies depending on the double density, but for example, n
=3 to 8, the dry coating weight is preferably 15 to 30 g/rf, more preferably 16 to 25 g/rrr.

If the ink layer thickness is less than 15 g/rrl', sufficient recording density cannot be obtained in double-density recording, and if it exceeds 30 g/i, problems such as an increase in the recording energy of the thermal transfer material occur, which is not preferable.

〔Example〕

The present invention will be explained in more detail below with reference to Examples.

The above composition was dissolved and dispersed in 400 parts of toluene, and further dispersed and mixed using a sand mill to obtain a coating liquid.

The coating solution was coated onto a back-treated polyethylene terephthalate film having a thickness of 6 μm using a wire bar so that the weight after drying was 18 g/rrr, and dried to obtain a heat-sensitive transfer material (I).

Evaflex V-5411 of the composition of Example 1 was added to Evaflex EV-2101: *Antioxidant 2.6-di-
Ethylene vinyl acetate copolymer containing 750 ppm of t-butyl-p-cresol (hereinafter referred to as B, H, T) in total Evaflex 210 MI: 400 VA: 2
A thermal transfer material (n) was obtained in the same manner as in Example 1 except that the material was changed to Mitsui Dupont Polychemical (manufactured by Kiki).

Next, the 2,6-di-t contained in EVAFLEC 210
-Butyl-p-cresol (hereinafter referred to as B, H, T) is extracted with methanol, and EVs containing different E, H, and T are extracted.
-210-A (500ppm), EV-210-B
(370ppm), EV-210-C (250ppm)
, EV-21-D (120 ppm) was obtained.

A thermal transfer material (III) was obtained in the same manner as in Comparative Example 1 except that EV-210-A was used instead of EV-210.

- 2 3 4 EV-210 of Comparative Example 1 was converted into EV-210-B, C,
Thermal transfer material (■) was prepared in the same manner except that D was used.

(V) and (VI) were obtained.

A thermal transfer material (■) was obtained using the above composition in the same manner as in Example 1.

2,2'-methylene-bis-(4-ethyl-
A thermal transfer material (■) was obtained in the same manner as in Example 5, except that the number of parts of (6-t-butylphenol) was 0.02 parts.

On the other hand, a facsimile manufactured by Canon Co., Ltd. (trade name: Canofax 630) was partially modified to transport the recording medium and the thermal transfer material so that the thermal transfer material and the recording medium had a relative speed as shown in FIG. The evaluation machine was modified so that the conveyance length of the thermal transfer material was less than the conveyance length of the recording medium. The physical conditions of this evaluation machine are as follows.

(1) The thermal head is a thick film type full multi-head heater with a rate of 8 pel/mm, and the main scanning direction is 100 μm1.
The sub-scanning direction is 60 μm.

(2) The feeding amount of the thermal transfer material is 115 times the feeding amount of the recording medium.

(3) The feeding directions of the thermal transfer material and the recording medium are opposite.

(4) The recording speed is 25 mm/sec, and the relative speed between the recording medium and the thermal transfer material is 31 mm/sec.
．． 2 mm/sec.

(5) The surface heat energy of the recording thermal head is 2
It is 2mJ/mPo.

Next, the thermal transfer materials (I) to (■) described above were loaded into the evaluation machine, and the Image Electronics Engineers of Japan facsimile test chart No.
, 2 images were output in copy mode.

Table 1 shows the evaluation results for the trailing edge stain of the obtained images.

×: Powder-like stains are observed at the rear edge of the image and are noticeable △: Powder-like stains are slightly observed at the rear edge of the image, but there is no problem in practical use ○: No rear-edge stains occur [invention [Effects] As explained above, the thermal transfer material of the present invention contains 150 ppm or less of antioxidant in the thermal transferable in-layer, so it is free from trailing edge stains, especially powdery stains, which are problems specific to double-density recording systems. It is possible to prevent edge staining and to obtain clear transferred recorded images.

[Brief explanation of drawings]

FIGS. 1 and 2 are perspective views showing an example of a device using the thermal transfer material of the present invention, and FIGS. 3 to 6 are portions showing an example of using the thermal transfer material of the present invention for double-density recording. FIG. 1...Thermal transfer material 2...Recorded object 3...Recording head 3a...Heating element

Claims (5)

[Claims] (1) In a thermal transfer material comprising a thermal transferable ink layer provided on a support, an antioxidant is added to the thermal transferable ink layer.
A heat-sensitive transfer material comprising a content of 50 PPM or less. (2) The heat-transferable ink layer contains at least a heat-melt binder and a colorant, and the heat-melt binder is selected from ethylene vinyl acetate copolymer and ethylene ethyl acrylate copolymer. 2. The thermal transfer material according to claim 1, wherein the content of wax is 40 to 80% by weight based on the binder, and the wax content is 20 to 60% by weight based on the binder. (3) The thermal transfer material according to claim 1, wherein the antioxidant is a phenolic antioxidant. (4) The antioxidant is 2,6-di-t-butyl-p-
4. The thermal transfer material according to claim 3, which is a cresol. (5) Using a thermal transfer material in which a thermally transferable ink layer is provided on a support, and the thermally transferable ink layer contains an antioxidant in a content of 150 PPM or less, the recording medium moves to the recording head within the same time. A thermal transfer recording method characterized in that the distance that the heat-sensitive transfer material moves relative to the recording head is shorter than the distance that the heat-sensitive transfer material moves relative to the recording head.