JPH0361587A - Thermal transfer material and thermal transfer recording method - Google Patents

Abstract

PURPOSE:To prevent tailing, background staining and printing irregularity by providing an ink layer having specific breaking strength and containing specific amount of ethylene/vinyl acetate copolymer, wax and a tackifier in a binder and, further, setting specific amount of the aforementioned ethylene/ vinyl acetate copolymer to an ethylene/vinyl acetate copolymer containing vinyl acetate. CONSTITUTION:The breaking strength of an ink layer is within a range of 30-80kg/cm<2> at 25 deg.C and 40-80wt.% of ethylene/vinyl acetate copolymer and 20-60wt.% of wax are contained in a binder and, further, in order to prevent the transfer of excessive ink due to the first application of ink, 5-25% of the ethylene/vinyl acetate copolymer in the ink layer is constituted of an ethylene/ vinyl acetate copolymer whose vinyl acetate content is 1-13%. When the break ing strength of the ink layer is too low, background staining or tailing is generat ed and, when the breaking strength is too high, a recording image having infe rior sharpness is obtained.

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.

[Description of prior art]

In addition to the general features of thermal transfer recording methods, such as the equipment used being lightweight, compact, noiseless, and easy to operate and maintain, the thermal transfer recording method does not require color-forming processed paper; It has the feature of excellent image durability and has been widely used recently.

This heat-sensitive transfer recording method uses a heat-sensitive transfer material in which a heat-transferable ink layer consisting of a colorant dispersed in a heat-melting binder is coated on a base material that is generally in the form of a sheet or ribbon. The materials are stacked so that the thermally transferable ink layer is in contact with the recording medium, and heat is supplied from the substrate side by a recording head to transfer the melted ink layer onto the recording medium in accordance with the shape of the heat supply. It is something that forms.

[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 by applying heat several times, so it is disposable, resulting in high running costs and the risk of leaking confidential information from the used thermal transfer material. There were also concerns about leaks.

In contrast, as in Japanese Patent Application Laid-open No. 57-83471 or Japanese Patent Publication No. 62-58917, a relative speed is provided between the thermal transfer material and the recording medium to reduce the amount of thermal transfer material used. A recording method (hereinafter referred to as double-density recording) has been proposed.

However, this recording method has conventionally had the following problems.

The first problem is that background smear (unnecessary ink transfer to the surface of 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 scraped off the surface of the recording medium and transferred to the entire surface of the recording medium. .

The second problem is that, as shown in FIG. 7, unnecessary whisker-like transfers 20 (
(hereinafter referred to as tailing) occurs. This is because in double-density recording, heat is applied multiple times to the same part of the ink layer, so the ink layer accumulates heat and the melt viscosity of the ink decreases significantly, and in this state, the recording medium and thermal transfer material slide together. arise in order to

As a countermeasure against scumming, Japanese Patent Application Laid-open No. 60-178088 proposes providing an overlayer containing no colorant on the ink layer, but this prevents the overlayer from being transferred to the recording medium after heat is applied. , the issue of tailing has not been resolved.

These problems can be solved by using the thermal transfer material disclosed in Japanese Patent Application No. 1-25278 previously filed by the present inventors.

However, the third problem is that in double-density recording, heat is repeatedly applied to the same location on the thermal transfer material N times, so a large amount of ink on the thermal transfer material is transferred to the recording medium during the first application of heat. Then, when heat is applied for the second time or later, the amount of ink may be insufficient, resulting in uneven print density, or the thermal transfer material and recording medium may be tightly adhered through a large amount of ink, resulting in poor running due to the ink not being cut. sometimes occurred.

The present invention has been made in order to solve the problems of the prior art described above.In double-density recording, trailing and background smearing do not occur, recording can be performed with uniform and high print density, and furthermore, it is possible to perform recording with uniform and high print density. The present invention provides a thermal transfer material with stable properties and a thermal transfer recording method.

[Means to solve the problem]

As a result of intensive research to solve the above problems, we found that in double-density recording, a large amount of ink is transferred to the recording medium when heat is applied for the first time to the area of the thermal transfer material where a large amount of ink exists. It has been found that it is effective to avoid this. That is, the thermal transfer material of the present invention has an ink layer containing a binder and a coloring material on a support, and the breaking strength of the ink layer is 30 to 80 at 25°C.
kg/cm2, and the binder contains an ethylene-vinyl acetate copolymer of 4% to the binder.
0 to 80% by weight, containing 20 to 60% by weight of wax,
Furthermore, 5 to 25 of the above ethylene-vinyl acetate copolymers
% by weight is ethylene with a vinyl acetate content of 1 to 13%.
It is characterized by being a vinyl acetate copolymer.

Further, in the thermal transfer recording method of the present invention, the thermal transfer material is used, and the distance that the thermal transfer material moves relative to the recording head is longer than the distance that the recording medium moves relative to the recording head within the same time. is recorded so that it is shorter.

The present invention will be described in detail below with reference to the drawings as necessary. In the following description, "parts" and "%" expressing quantitative ratios are based on weight unless otherwise specified.

As shown in FIG. 6, the thermal transfer recording method (double density recording method) using the thermal transfer material of the present invention includes the thermal transfer material 1 of the present invention shown in FIG. 1 and a recording medium 2 such as paper. By heating them with a recording head 3 such as a thermal head, the fully meltable ink of the heat-sensitive transfer material 1 is transferred onto the recording medium 2 to obtain a recorded image.

The thermal transfer material 1 and the recording medium 2 are connected to a capstan roller 1.
2, the pinch roller 13, and the platen roller 11 move continuously in the directions of arrows A and B, respectively, and recording is performed on the recording medium 2 one after another.

The capstan roller 12 and the pinch roller 13 are operated by a motor 14, and the platen roller 12 is operated by a motor 15.
are respectively driven by. The transported thermal transfer material 1 is wound up by a winding roller IO 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. 6, the thermal transfer material 1 and the recording medium 2 are moving in opposite directions. The recording body 2 may be moved in exactly the same direction.

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. 6, the head 3 does not move, and the thermal transfer material 1 moves slower than the recording medium 2. In the example shown in FIG. 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. 2 to 5.

As shown in FIG. 2, when the width of the heating element 3a of the recording head 3 in the feeding direction (direction of arrow A) of the thermal transfer material l is l, the first heat application is performed on completely unused thermal transfer material l. This is done with a size of l.

However, when heat is applied for the second time, as shown in FIG. 2nd to 5th
In the figure, only N = 5) is moved, so the portion (jl! - (j'/N)) of the thermal transfer material 1 that has already been subjected to heat application once will be used again.

When heat is applied continuously in the lateral direction in this manner, as shown in FIGS. 3 to 5, the thermal transfer material 1 subjected to the second and subsequent heat applications has f! Only /N is in an unused state (a newly supplied part), and the rest have already been heated several times by l/N.

In other words, the thermal transfer material 1 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.

Now, as is clear from the above explanation, since the thermal transfer material 1 of the present invention is used while sliding on the recording medium 2 such as paper, if the breaking strength of the ink layer 1b is too small, the surface of the recording medium This is undesirable because scumming and trailing occur due to friction. Furthermore, if the breaking strength of the ink layer 1b is too large, it becomes difficult to break well at the boundary between the heat applied part and the non-heat applied part of the ink layer 1b.
Poor sharpness (the edges of the recorded image are uneven and not sharp)
This may result in a recorded image, or in the worst case, the ink layer may not be cut and not transferred to the recording medium. The inventors
As a result of examining the relationship between the breaking strength of the ink layer and the recorded image in double-density recording using various thermal transfer media with different breaking strengths of the ink layers, it was found that the breaking strength of the ink layer was 25°C.
It has been found that it is very effective to set the pressure to 30 to 80 kg/c, more preferably 35 to 60 kg/c.

In the present invention, the numerical value of the breaking strength is determined based on the dumbbell shape (JIS
K7113. Using a tensile strength tester (Tensilon RTM-100 manufactured by Toyo Baldwin Co., Ltd.), the ink film with a uniform thickness was measured at a temperature of 250 C and a tensile speed of 200 mm for 7 minutes. The yield value '(Kg/crd)

A dumbbell-shaped ink film is created as follows. That is, the same ink material as the ink layer used for the thermal transfer material is applied onto the release paper using an applicator, a wire bar, etc., so that the thickness after drying is about 35 μm.

After the ink layer dries, the release paper is removed to create an ink film.

Further, the ink layer of the thermal transfer material of the present invention has l 20 'C
Melt viscosity at 3 x 103 to 5 x 10'mPa
More preferably, it is 7 x 103 to 4 x 104 mPa-8. Also, the melt viscosity at 100°C is 5
X 103~lXl0'mPa-61 and even 9x10
It is preferable that it is 3 to 5 x 104 mPa-3.

If the melt viscosity of the ink layer is too small, 1
A large amount of ink is transferred by the first heat application, and only a small ink layer is transferred by the second and subsequent heat applications, resulting in a decrease in the density of the recorded image or uneven density. On the other hand, if the melt viscosity of the ink layer is too high, the ink may stick without being sheared after the ink layer and the recording medium have adhered to each other, resulting in poor running, which is undesirable.

In the present invention, the melt viscosity is a value measured using an E-type viscometer (PK-I-0, 3, Roto Visco manufactured by Haake Co., Ltd.).

However, even if the film strength and melt viscosity of the ink layer are designed as described above, when printing a pattern such as CCITT No. 8, running defects sometimes occur when solid black printing starts, and related problems occur. In black or solid black areas with white characters, white streaks appear and uniform density cannot be obtained. This is the state shown in FIG. 2, where when heat is applied to completely unused ink lb, the largest amount of ink 1b exists on the thermal transfer material l, so if a large amount of ink 1b is transferred, The adhesion between the thermal transfer material 1 and the recording medium 2 becomes strong, and the ink film is not cut by the shearing force caused by the difference in moving speed between the thermal transfer material 1 and the recording medium 2, and the ink of size 1 is transferred to the support 1a. White streaks appear in prints due to poor running caused by the ink being completely transferred or the cutting time of the ink film being delayed.

This phenomenon tends to occur when the printing environment is at a relatively low temperature (below 20°C) or when printing is suddenly started after not printing for a while. It returns to the previous large value quickly,
This is thought to be because even if an attempt is made to cut the film by misaligning the recording medium 2 and the thermal transfer material 1, it becomes difficult to cut.

In order to prevent this and ensure stable running at all times and to prevent density unevenness from occurring, it is necessary to prevent the ink 1b from being excessively transferred to the recording medium 2 during the first heat application.

That is, the material used for the binder in the ink layer 1b is preferably ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer, as it has film properties and softens/melts well when heat is applied. Among these, ethylene-vinyl acetate copolymer is preferred because, when used as an ink for thermal transfer materials, it has a relatively low softening point and can reduce the amount of heat applied from the recording head, reducing damage to the base material. It is.

The copolymerization ratio of ethylene and vinyl acetate is 80:20
~50: 50 is good and the softening point (according to DSC method) is 6
An ethylene-vinyl acetate copolymer having a temperature range of 0 to 130°C, more preferably 75 to 100°C is preferred.

If most of the binder is composed of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer, the melt viscosity will increase and the film strength of the ink layer will also become too high. Therefore, in order to adjust the melt viscosity of the ink and the breaking strength of the ink layer, natural waxes such as carnauba wax, montan wax, and linole wax, synthetic waxes such as paraffin wax, microcrystalline wax, castor wax, polyethylene wax, and linole wax, It is preferable to mix one or a mixture of two or more waxes selected from waxes such as natural waxes, ester waxes, and polypropylene waxes into the binder.

The content of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer in the binder is 40 to 80% by weight, and further 45 to 70% by weight based on the binder.
Weight percent is preferred.

The melting point of the ink is between 60 and 60, since the ink layer needs to be larger in thermal transfer materials for double-density recording than in conventional thermal transfer materials, which is disadvantageous in terms of thermal energy.
It is preferable to set the temperature to 65 to 85°C (temperature of main peak measured by DSC measurement) rather than 100°C. Therefore, when selecting a wax component, its melting point (according to DSC measurement) should be 60 to 100°C, more preferably 65 to 8°C.
It is best to choose one with a temperature of around 5℃.

If the temperature is less than 60°C, problems will arise in the storage stability of the heat-sensitive transfer material, which is undesirable, and if it exceeds 1000C, problems such as an increase in printing energy will occur, which is undesirable.

Furthermore, in order to prevent excessive ink transfer due to the first heat application, 5 to 25% of the ethylene-vinyl acetate copolymer in the ink layer is replaced with an ethylene-vinyl acetate copolymer with a vinyl acetate content of 1-13%. Preferably, it is a polymer.

As an ethylene-vinyl acetate copolymer, the softening point (DS
method C) is 70-110°C, more preferably 75-110°C
A temperature of about 95°C is preferable.

By adding as described above, the sensitivity of the ink itself is slightly lowered, and furthermore, the hot touch property is lowered, thereby preventing excessive transfer of the ink due to the first heat application. Furthermore, in the second and subsequent heat applications, as the heat-sensitive transfer material accumulates heat, the compatibility of the transfer layer is good, so that it is dominated by the wax and ethylene-vinyl acetate copolymer, which are the main components. It exhibits melting behavior, and further heat accumulation makes it easier to cut the film, stabilizing running performance.

Therefore, 5 to 2 of the ethylene-vinyl acetate copolymer
The adverse effects of replacing 5% with an ethylene-vinyl acetate copolymer having a vinyl acetate content of 1 to 13% are not seen within the above range.

If the vinyl acetate content exceeds 13%, the melting properties will be broad and the hot tack properties will be strong, making it impossible to prevent excessive transfer. If the vinyl acetate content is less than 1%, the compatibility with wax, ethylene-vinyl acetate copolymer, etc. will be extremely deteriorated, which is not preferable.

When the content of the ethylene-vinyl acetate copolymer with a vinyl acetate content of 1 to 13% is less than 5 to 25% of the total ethylene-vinyl acetate copolymer, no effect is observed. . If it exceeds 25%, it is not preferable because it causes a decrease in film properties and tends to cause scumming and trailing.

Further, the thermal transfer material of the present invention may further contain a tackifier as a binder component. The effect of adding a tackifier is to improve the compatibility of the other binder components, wax, ethylene-vinyl acetate copolymer, and ethylene-vinyl acetate copolymer with a vinyl acetate content of 1 to 13%. This enables more uniform (stable) transfer of ink and stabilizes running performance.

In order to achieve the above effects, it is preferable that the binder contains 5 to 15% by weight, more preferably 7 to 12% by weight. If the content is less than 5%, no sticky effect will be produced, and if it exceeds 15%, the melt viscosity will increase, hot tack properties will increase, and the like will have an adverse effect on runnability.

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. .

The ink layer 1b is composed of the above binder containing a coloring material.

Examples of colorants include carbon black, nigrosine dye, lamp black, Sudan Black SM, Fast Yellow G1 Benzine Niro, Pigment Yellow, Indo Fast Orange, Irgazine Red, Paranitroaniline Red, Toluidine Red, Carmine FB, Permanent Bordeaux. FRR, Pigment Orange R1 Resole Red 2G.

Lake Red 2G, Lake Red C10-Damin FB.

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

Zapon Fast Yellow GG, Sumiplast Yellow GG
, Zapon Fast Orange RR, Oil Scarlet,
Sumiplast Orange G1 Orazur Brown G1 Pomelo Fast Scarlet CG, Fast Gemble-50
07, one or a mixture of two or more of conventionally known colorants such as Sudan Blue and Oil Peacock Blue are used.

The content of the coloring material in the ink layer 1b is preferably 1 to 50% by weight, more preferably 5 to 35% by weight. If the colorant content is less than 1% by weight, the density of the recorded image will be very low;
If it exceeds 50% by weight, problems such as a decrease in the adhesive strength of the ink to the recording medium and a decrease in the breaking strength of the ink layer are undesirable.

The thickness of the ink layer 1b is 10 to 30 g/dry coating weight.
rr? is preferable, and more preferably 12 to 20 g/rd. If the ink layer thickness is less than Jog/rr1', sufficient recording density cannot be obtained in double-density recording, and 30 g/, rf
If it exceeds l', problems such as curling of the thermal transfer material and an extreme increase in recording energy occur, which is not preferable.

Next, as the support 1a of the thermal transfer material 1, conventionally known plastic films, paper, etc. can be suitably used, but in double-density recording, heat is applied to the same location on the support many times. Therefore, for example, polyethylene terephthalate film, aromatic polyamide film, polyphenylene sulfide film, polyether ether ketone film, condenser paper, etc. are preferable.

Further, it is desirable to provide a conventionally known back surface treatment on the surface of the support opposite to the surface on which the ink layer is applied, in order to improve the slidability with the thermal head and the heat resistance of the support.

The thickness of the support is preferably 3 to 20 μm, and more preferably 4 to 20 μm.
12 μm is desirable. Materials with a diameter of 3 μm or less can also be used as long as they have high strength and heat resistance. Further, excessively thick materials are not preferable because they have poor thermal conductivity. However, when used in the current transfer recording method, which uses a conductive support, uses an electrode needle head instead of a thermal head, and applies a voltage to the heat-sensitive transfer material to generate Joule heat, this method cannot be used. There is no limit.

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 the ink 1b to the substrate, if a monochromatic (for example, black) colored ink is applied to the entire surface, a monochromatic thermal transfer can be obtained. In addition, multiple color ink layers (for example,
Multi-color recording is possible by repeatedly applying cyan ink, magenta ink, yellow ink, blue ink, green ink, or red ink, etc., and recording in such a way that the colors overlap when printing. A thermal transfer material can also be obtained.

EXAMPLES The present invention will be specifically explained below with reference to Examples.

[Example 1] [Ink ■] Of the above materials, except carbon black, were heated and dissolved in toluene, carbon black was added thereto, and the mixture was dispersed in a sand mill at 200 Or, p, m for 30 minutes to obtain an ink.

This was coated with a backside treatment consisting of silicone-acrylic-urethane terpolymer at a thickness of 6 μm at 0.8 g/rrf.
polyethylene terephthalate film (hereinafter referred to as thickness 6)
Apply the above ink to the opposite side of the back-treated PET film (hereinafter referred to as "μm back-treated PET film") using a mailer bar, and heat the film at 100°C.
Dry for 1 minute in a dry oven and apply dry fi 1
A thermal transfer material 1 having an ink layer of 5 g/rrr was obtained.

In addition, in the above ink (2), the vinyl acetate content was 10% instead of 15% based on the total ethylene-vinyl acetate copolymer.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 5
It was 5 kg/cpo.

[Example 2] [Ink ■] Among the above materials, except carbon black, were heated and dissolved in toluene, carbon black was added thereto, and the mixture was dispersed in a sand mill at 2000 r, p, m for 30 minutes to obtain ink ■.

The above ink (■) was applied with a mailer bar to the side opposite to the back side treatment of a 6 μm thick back side treated PET film.
Dry for 1 minute in a dry oven at 0°C and apply dry
A thermal transfer material (2) having an ink layer of 15 g/rrl' was obtained.

In the above ink (1), 7% of the total ethylene-vinyl acetate copolymer was replaced by an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10%.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 5
It was 7 kg/ctrr.

[Example 3] [Ink 1] The above materials except carbon black were heated and dissolved in toluene, and then carbon black was added and dispersed in a sand mill at 200 Or, p, m for 30 minutes to obtain ink 2.

The above ink (■) was applied with a mailer bar to the side opposite to the back side treatment of a 6 μm thick back side treated PET film.
Dry for 1 minute in a dry oven at 0°C, dry coating amount: 1
A thermal transfer material (2) having an ink layer of 5 g/rrr was obtained.

In addition, in the above ink (1), the vinyl acetate content was 10% instead of 20% based on the total ethylene-vinyl acetate copolymer.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 5
It was resistant to 3 kg/c.

[Example ■]

[Ink (1)] Among the above materials, other than carbon black was heated and dissolved in toluene, and then carbon black was added and dispersed in a sand mill at 200 Or, p, m for 30 minutes to obtain ink (2).

The above ink (■) was applied with a mailer bar to the side opposite to the back side treatment of a 6 μm thick back side treated PET film.
Dry for 1 minute in a dry oven at 0°C and apply dry
A thermal transfer material (2) having an ink layer of 15 g/rrr was obtained.

In the above ink (1), 15% of the total ethylene-vinyl acetate copolymer was made up of ethylene-vinyl acetate copolymer having a vinyl acetate content of 5%.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 6
It was 0 kg/clT1+.

[Example ■]

[Ink ■] Of the above materials, except carbon black, were heated and dissolved in toluene, and then carbon black was added and dispersed in a sand mill at 200 Or, p, m for 30 minutes to obtain ink ■.

The above ink (■) was applied with a mailer bar to the side opposite to the back side treatment of a 6 μm thick back side treated PET film.
Dry for 1 minute in a dry oven at 0°C, dry coating amount: 1
A thermal transfer material (2) having an ink layer of 5 g/% was obtained.

In addition, in the above ink (2), the vinyl acetate content was 10% instead of 15% based on the total ethylene-vinyl acetate copolymer.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 5
It was 0 kg/cbo.

[Comparative Example 1] [Ink (■)] Among the above materials, other than carbon black was heated and dissolved in toluene, carbon black was added thereto, and the mixture was dispersed in a sand mill at 200 Or, p, m for 30 minutes to obtain ink (■).

The above ink (■) was applied with a mailer bar to the side opposite to the back side treatment of a 6 μm thick back side treated PET film.
Dry for 1 minute in a dry oven at 0°C, dry coating amount: 1
A thermal transfer material (2) having an ink layer of 5 g/% was obtained.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 1
It was resistant to 8 kg/c.

[Comparative Example 2] [Ink ■] Of the above materials, except for carbon black, were heated and dissolved in toluene, carbon black was added thereto, and the mixture was dispersed in a sand mill at 200 Or, p, m for 30 minutes to obtain ink ■.

The above ink (■) was applied with a mailer bar to the side opposite to the back side treatment of a 6 μm thick back side treated PET film.
Dry for 1 minute in a dry oven at 0°C, dry coating amount: 1
A thermal transfer material (2) having an ink layer of 5 g/rrr was obtained.

In the ink (1) above, the vinyl acetate content was 10% instead of 30% based on the total ethylene-vinyl acetate copolymer.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 3
It was 5 kg/crrr.

[Comparative Example 3] [Ink (■)] Among the above materials, other than carbon black was heated and dissolved in toluene, and then carbon black was added and dispersed in a sand mill at 200 Or, p, m for 30 minutes to obtain ink (■).

The above ink (■) was applied with a mailer bar to the side opposite to the back side treatment of a 6 μm thick back side treated PET film.
Dry for 1 minute in a dry oven at 0°C, dry coating amount: 1
A thermal transfer material (2) having an ink layer of 5 g/ni' was obtained.

The breaking strength of the film at 25℃ due to the solid matter of ink ■ is 9
It was 8 kg/cpo.

The above thermal transfer materials I to ■ are facsimile machines manufactured by Canon,
Canofax 630 was modified as shown in Figure 6 and used as an evaluation machine. The outline of the evaluation machine is as follows.

The thermal transfer material 1 and the recording medium 2 are connected to a capstan roller 1.
2, the pinch roller 13, and the platen roller 11 move continuously in the directions of arrows A and B, respectively.
Recording is performed on the recording medium 2 one after another.

The capstan roller 12 and the pinch roller 13 are operated by a motor 14, and the platen roller 12 is operated by a motor 15.
are respectively driven by. The transported thermal transfer material l is wound up by a winding roller 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.

The mechanical and physical conditions of this device are as follows.

(1) Equipped with a full multi-thermal head of 8 pel/mm, 1 kg/c against the platen roller
rr? is fixed with pressure.

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

(3) The thermal transfer material and the recording medium are fed in opposite directions.

(4) Printing speed on recording medium is 25 mm/
It is sec. Further, the relative speed between the recording medium and the thermosensitive plate photographic material at this time was 31.2 mm/sec.

(5) The surface heat energy of the thermal head is 28 m
J/mrr? It is.

Using thermal transfer materials I to ■ under the above conditions, C (JTTN
(L8 charts were printed and evaluated on the following items.

■The running stability is affected by a large change in resistance when the recording medium and the thermal transfer material are sliding through the melted ink at the transition from the solid ring to the white blank text. The running of the material becomes unstable and white streaks occur.

■Regarding tailing, as solid rings were printed continuously, the thermal head and platen roll accumulated heat, which in turn accumulated heat in the ink layer, resulting in a decrease in breaking strength and a persistently low melt viscosity of the ink, causing trailing.

■The stability when moving from a solid ring to an all-white area requires an extremely large amount of force as the recording medium and thermal transfer material must be peeled off over a 256,5 mm distance. Since this is necessary, running stops, etc. occur.

■When printing a solid ring from all white, if the ink cannot be stably and uniformly transferred to the recording medium from the time it receives heat for the first look, it may cause blurring, chipping, or white streaks. Causes unevenness.

■Although it is a non-heat application part, due to the sliding between the recording medium and the thermal transfer material, if the colored ink layer (first ink layer) has low breaking strength and is brittle, it may be transferred to the recording medium by pressure and abrasion. Causes dirt.

The thermal transfer materials ■～■ were evaluated regarding the above items, but
This is summarized in the table on the next page.

In the above evaluation, ◯ indicates good, ∆ indicates slightly inferior but no problem in actual use, and × indicates very poor and difficult to use in actual use.

〔Effect of the invention〕

As explained above, in double-density recording using the thermal transfer material of the present invention, it is possible to prevent trailing and scumming with a simple configuration, improve density uniformity by making transfer uniform, and improve thermal transfer. By stabilizing the running of the material, it is possible to prevent uneven printing.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the structure of the thermal transfer material of the present invention. FIGS. 2 to 5 are schematic diagrams showing double-density recording. FIG. 6 is a perspective view showing an embodiment of an apparatus for performing double-density recording using the thermal transfer material of the present invention. Thermal transfer material recording medium recording head

Claims (3)

[Claims] (1) In a thermal transfer material having an ink layer containing a binder and a coloring material on a support, the breaking strength of the ink layer is in the range of 30 to 80 kg/cm^2 at 25°C, and For the binder, 40 to 80% by weight of ethylene-vinyl acetate copolymer, 20 to 60% by weight of wax, and 5 to 15% of tackifier.
% by weight, and 5 to 25% by weight of the ethylene-vinyl acetate copolymer has a vinyl acetate content of 1 to 13% by weight.
% ethylene-vinyl acetate copolymer. (2) A thermal transfer material characterized in that the binder contains 5 to 15% by weight of tackifier fire. (3) Using the thermal transfer material according to claim 1, the distance that the thermal transfer material moves relative to the recording head is longer than the distance that the recording medium moves relative to the recording head within the same time. A thermal transfer recording method that is characterized by its short length.