JPH0361589A - Thermal transfer material and thermal transfer recording method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 the thermal transfer material used is reduced.

[Conventional technology]

Thermal transfer recording method has the general features of thermal recording methods such as the equipment used is lightweight, compact, noiseless, and has excellent operability and maintainability. 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).

Furthermore, an electrically conductive thermal transfer recording method is also known as one of the thermal transfer recording methods. This method involves applying a voltage to a conductive support or ink layer and causing the conductive support or ink layer itself to generate heat using Joule heat (Japanese Patent Laid-Open No. 58-2207
No. 95, Japanese Patent Application Laid-Open No. 5812790, etc.), by transferring molten ink onto a recording medium, a transferred recorded image corresponding to the shape of heat supply is formed on the recording medium.

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, as in Japanese Patent Application Laid-Open No. 57-83471 or Japanese Patent Publication No. 62-58917, a recording method reduces the amount of thermal transfer material used by providing a relative speed between the thermal transfer material and the recording medium. (hereinafter referred to as double density recording) has been proposed.

[Problem that the invention is trying to solve]

However, this recording method has the following problems.

l) Since the same location on the thermal transfer material is printed several times, a transferred recorded image having a uniform print density cannot be obtained.

2) Since a relative speed is provided between the thermal transfer material and the recording medium, so-called "background stains" and "tailing" are likely to appear on the transferred recorded image.

l) As a countermeasure to the problem, JP-A-62-1047
As seen in No. 94, it is stated that the thicker the ink layer of a thermal transfer film that can be printed multiple times, the more times the ink can be printed completely without adhering to the printing area, but it is more specific. There is no description of the printing density and number of times of printing, nor is there any description of obtaining a uniform density.

In addition, JP-A-55-105579 is cited in the specification of JP-B-62-58917 (Page 232, left column, line 44), and according to this, the thermal transfer material of the porous ink-retaining layer is suitable for printing. The print density decreased significantly between the first and fourth times, and a uniform print density was not obtained.

On the other hand, regarding countermeasures for problem 2),
Publication No. 8993 states that the heat-melting ink is formulated with wax, a thermoplastic resin with a melt index of 1.5 to 500, and a colorant, and has a viscosity of 2 to 100 poise at 90°C. It has been found that in this viscosity range, "tailing" tends to occur and it is not possible to obtain a satisfactory print density. Also, JP-A-61-242893, JP-A-61-268488, JP-A-61-287790.
All of the publications contain a large amount of wax compared to the ethylene vinyl acetate copolymer, so this also causes "tailing".
It was also found that this is easy to occur.

The present invention has been made to solve the above-mentioned problems, and provides a thermal transfer material and a thermal transfer recording method that can provide a transferred image with uniform print density and have excellent print quality without any "tailing". With the goal.

[Means to solve the problem]

The heat-sensitive transfer material of the present inventor has a plurality of heat-melting ink layers on a support, and contains 65 to 40% by weight of ethylene vinyl acetate copolymer and 35 to 40% by weight of wax as a binder for the heat-melting ink layer. The melt viscosity of each hot-melt ink layer decreases as the distance from the support increases.

Further, in the thermal transfer recording method of the present invention, 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 using the above-mentioned thermal transfer material. is characterized by being shorter.

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

In the following description, "%" and "part" expressing quantitative ratios are based on weight unless otherwise specified.

The thermal transfer material of the present invention is shown in FIG.

A heat-melting ink layer 1b having a support 1a and a heat-melting ink layer 1b having different mixing ratios of ethylene-vinyl acetate copolymer and wax.

lc and ld are formed in three layers, and the support 1a is subjected to back surface treatment 1e as required.

Conventionally known plastic films and paper can be used as the support 1a, but in double-density recording, heat is applied many times to the same location on the base material, so for example aromatic polyamide film, polyphenylene sulfide film, polyether Preferably, materials with high heat resistance such as ether ketone, capacitors, and paper are used. In addition, when using a polyester film (especially polyethylene terephthalate film, abbreviated as PET film), which has been suitably used in conventional heat-sensitive transfer materials, a material having heat resistance and slip properties is provided on the surface opposite to the ink surface as the back surface treatment 1e. It is preferable.

The thickness of the base material is preferably 3 to 20 μm, more preferably 4 to 12 μm.
μm is desirable. 3μ if it has high strength and heat resistance
It is also possible to use thin ones of less than m. Further, excessively thick materials are not preferable because they have poor thermal conductivity.

In the thermal transfer material of the present invention, the ink layer is a mixture of a binder and a coloring material. As the material used for the binder, ethylene-vinyl acetate copolymer is preferred because it softens/melts well upon application of heat. The copolymerization ratio of ethylene and vinyl acetate is 90, 10-50:
Preferably, the ethylene-vinyl acetate copolymer has a softening point (ring and ball method) of 70 to 130°C, more preferably 80 to 100°C, and a melt index value of 100 to 500.

If most of the binder is composed of ethylene-vinyl acetate copolymer, the melt viscosity will increase, so in order to adjust the melt viscosity of the ink layer, natural waxes such as carnauba wax, monk wax, linole wax, paraffin wax, micro Crystalline wax, castor wax.

It is preferable to mix one or more waxes selected from synthetic waxes such as polyethylene wax and Sasol wax, synthetic waxes thereof, ester waxes, polyethylene waxes, and polypropylene waxes into the binder.

In this way, the binder component of the heat-melting ink of the present invention is composed of an ethylene-vinyl acetate copolymer and a wax component. A lubricant such as acid amide and silicone oil, and an antioxidant such as 2,6-c-tertiary butyl p-cresol may be added.

Next, the heat-melting ink layers 1b and lc of the present invention.

1d will be explained.

The heat-melting ink layer 1b closest to the support 1a has a thicker melt viscosity than the heat-melting ink layer 1d furthest from the support. This is possible by increasing the mixing ratio of ethylene vinyl acetate copolymer to However, the amount of ethylene-vinyl acetate copolymer contained in the heat-melting ink layer 1b closest to the support must not exceed 65% by weight. It is not preferable that the amount of the ethylene vinyl acetate copolymer in layer 1d is less than 40% by weight.

The reason for this is that if it exceeds 65% by weight, "stickiness" occurs. The term "sticking" refers to the fact that when the melt viscosity is high, the thermal transfer material and the recording medium will stick together after printing, resulting in damage such as breakage of the thermal transfer material or the recording medium.

If it is less than 40% by weight, the melt viscosity will be too low and "tailing" will occur. This "tailing" is caused by the fact that in double-density recording, when the heat-melting ink is heated, the heat-sensitive transfer material and the recording medium have a relative speed. Therefore, the melt viscosity of the intermediate heat-melting ink layer IC is an intermediate value between lb and ld, and the mixing ratio of the ethylene vinyl acetate copolymer and wax is also close to the intermediate value.

The melt viscosity of each heat-melting ink layer was measured using an E-type viscometer (Roto Visco RV-12 manufactured by Haake Co., Ltd., rotor PK-I used).
-0,3) at 120'C, 7
．． 5 x 10' to 2 x 104 centipoise is preferred, and 8 x lO3 to 1.8 x 10' centipoise is more preferred. The respective heat-melting ink layers 1b, lc, l
The melt viscosity of d can be adjusted by adjusting the mixing ratio of the ethylene vinyl acetate copolymer and wax. In other words, increasing the mixing ratio of ethylene vinyl acetate copolymer increases the melt viscosity, and decreasing it decreases the melt viscosity.

Note that in the present invention, each of the heat-melting ink layers 1b, lc
.

The difference in melt viscosity between each layer may be equal, but the difference is preferably at least 8 x 10' to 1 x 10' centipoise at 120°C, more preferably 9 x 102 to 9 X I O3 centipoise.

When the melt viscosity is less than 7.5 x 10' centipoise, a large amount of ink will be transferred with one heat application, and only a small amount of ink will be transferred with subsequent heat applications, for example, solid images with extremely high black ratio. The concentration of is extremely reduced.

When the melt viscosity is greater than 2×10 4 centipoise, density unevenness occurs, presumably because it becomes difficult to control the amount of ink transferred. Furthermore, sticking becomes more likely to occur.

The heat-melting ink layer contains a colorant, and examples of the colorant include carbon black, nigrosine dye,
Lamp Black, Sudan Black SM, Fast Niro G1 Benzine Yellow Pigment Yellow, Indo Fast Orange, Irgazine Red, Varanitroaniline Red, Toluidine Red, Carmine FB, Permanent Bordeaux FRR, Pigment Orange R
1 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 GG.

Kayaset Y963, Sumiplast Yellow GG, Zapon Fast Orange RR, Oil Scarlet, Sumiplast Orange G1 Orazole Brown G1 Pomelo Fast Scarlet CG, Fast Gen Blue-5007, Sudan Blue, Oil Peacock Blue, etc. Use one type or a mixture of two or more types.

The amount of colorant contained in the ink layer is preferably 5 to 40% by weight, more preferably 10 to 35% by weight based on the entire ink layer.
is desirable. If the amount of coloring material is less than 5% by weight, the density of the recorded image will be extremely low, and if it exceeds 35% by weight, the recording energy will increase, the breaking strength of the ink layer will decrease, or the transferability to the recording medium will decrease. This is undesirable because problems such as a decrease in

Next, as a method for producing the thermal transfer material of the present invention, ethylene vinyl acetate copolymer and wax are mixed with toluene, xylene, M.E.
It may be dissolved in an organic solvent such as K, mixed with a colorant, sufficiently dispersed using a dispersing machine such as a sand mill, and coated on a base material using a coating method such as a bar code or gravure coating. In addition, after heating the resin above its softening point and dispersing the coloring material,
It may be applied using a so-called hot melt coat. Furthermore, the resin or colorant may be applied as an aqueous emulsion by adding a dispersant such as a surfactant.

When forming a multi-layered heat-melting ink layer, this process can be repeated, but if dissolution of the heat-melting ink layer closer to the support is a problem, change the type of organic solvent or use an aqueous solvent. This can be easily done using an emulsion.

When applying ink to the substrate, apply a single color (e.g. black) to the entire surface.
If colored ink is applied, a single color thermal transfer can be obtained. In addition, multiple color ink layers (for example, cyan ink, magenta ink, yellow ink, blue ink, green ink Alternatively, a thermal transfer material capable of multi-color recording can be obtained by repeatedly applying different colors (such as red ink) and recording so that the colors are overlapped during printing.

The reason why a transferred image with a uniform print density can be obtained in the present invention is that the ink layer gradually peels off due to the difference in melt viscosity due to double-density recording.

The thickness of the heat-melting ink layer is preferably 3 to 20 g/lri based on the total dry coating weight of each heat-melting ink layer,
4 to 18 g/lri is more preferable. If it is less than 3 g/rrr, the print density of the transferred image will be insufficient, and if it is more than 20 g/rrl', the recording energy will increase and damage to the support will increase.

In FIG. 1 of the present invention, the number of heat-melting ink layers is three, but is not particularly limited. It varies depending on the mixing ratio of ethylene vinyl acetate copolymer and wax, the content of coloring material, etc. In addition, the increase in the number of heat-melting ink layers depends on the thickness of the ink layer and the coating. Although it cannot be clarified as it is related to construction costs, it is generally assumed that the structure will be 3 to 4 layers.

Further, an adhesive layer may be provided between the support 1a and the heat-melt ink layer 1b in order to adjust the adhesiveness between the support and the heat-melt ink layer.

Next, in the thermal transfer recording method (double density recording method) using the thermal transfer material of the present invention, as shown in FIG. The thermal transfer material l is heated by the recording head 3 such as a thermal head.
A recorded image is obtained by transferring the heat-melting ink onto the recording medium 2. The thermal transfer material 1 and the recording medium 2 are continuously moved in the directions of arrows A and B by the rotation of the capstan roller 12, the pinch roller 13, and the platen roller 11, respectively, and are deposited onto the recording medium 2 one after another. A recording is made. The capstan roller 12 and the pinch roller 13 are driven by a motor 14, and the platen roller 12 is driven by a motor 15, respectively. The conveyed thermal transfer material l is taken up by a winding roller 10 driven by a motor 14.
It is wound up. 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 1 and the recording medium 2 are moving in the same direction, but for example, by conveying the recording medium 2 in the opposite direction to the direction of arrow B, the thermal transfer material 1 and the recording medium There is no problem even if the body 2 moves in the completely opposite 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. 2, 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 a completely unused thermal transfer material 1 with a magnitude of 1 (FIG. 3). Incidentally, the thermal transfer material 1 is a support la.
A hot melt ink layer 1b, lc on top.

1d is provided.

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 l moves I! with respect to the recording head 3. /n (in Figure 3, n = 5° The value of n 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 [l - lln):
] The parts that have already been subjected to heat application once will be used again (Fig. 4).

When heat is applied continuously in the lateral direction in this way, the heat-sensitive transfer material that receives heat from the second time onward is l/
Only n is unused, and the remaining lln have already been heated several times (FIGS. 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, when heat is applied for the second, third time, etc., the thermal transfer material l is j! /
Although it is assumed that the movement is by n, if the movement is less than 1 or more than n/n, the thermal transfer material 1 can be saved. This is a case where the amount of movement of the thermal transfer material 1 with high efficiency is l/n movement from one heat application to the next heat application.

The above n is preferably 2 to 10, more preferably 3 to 8.

In the above explanation, an example was shown in which the recording head 3 does not move. However, even when the thermal head 3 moves, the moving distance of each of the thermal transfer material l and the recording medium 2 is determined by the recording head 3.
If the distance from the recording head 3 is taken as a reference, it can be considered in the same way as the examples explained in FIGS. 2 to 6. That is, in the thermal transfer recording method of the present invention, the distance that the thermal transfer material 1 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 period of time.

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

Example 1 Ink-■ The above materials were mixed in a ball mill to obtain an ink.

The melt viscosity of this ink is 1.8X10 at 120℃
'It was centiboise.

Ink (■) The above materials were mixed in a ball mill to obtain ink (■). The melt viscosity of this ink is 1.5X1 at 120℃
It was 0' centipoise.

Ink-■ The above materials were mixed in a ball mill to obtain ink-■. The melt viscosity of this ink is lXl0' at 120°C.
It was centipoise.

Next, ink-■, ink-■, and inter-■ were coated on a PET film having a thickness of 6 μm using a Mayer bar in this order.

The dry coating weight was 4 g/rd for each layer, and the total weight of the ink layer was 12 g/rrr to obtain a thermal transfer material I.

In addition, a back treatment agent of silicone-acrylic-urethane ternary copolymer was applied in advance to the opposite side of the polyester film from the ink-coated side so that the dry coating weight was 0.3 g/nf. I used something.

Example 2 Inter ■ The above materials were mixed in a ball mill to obtain Inter ■. The melt viscosity of this ink is 1.0X1 at 120℃
It was 0' centipoise.

Ink (■) The above materials were mixed in a ball mill to obtain ink (■). The melt viscosity of this ink is 9X10' at 120°C.
It was centipoise.

Ink (■) The above materials were mixed in a ball mill to obtain ink (■). The melt viscosity of this ink is 8.5 at 120'C.
It was X103 centipoise.

Next, Ink-■, Ink-■, and Ink-■ were coated on a PET film having a thickness of 6 μm using a Mayer bar in the following order.

The dry coating weights were each 3.5 g/rrl', and the total ink layers were lo and 5 g/rrl, to obtain a thermal transfer material (2).

Example 3 Ink-■ The above materials were mixed and prepared in a ball mill to obtain ink-■. The melt viscosity of this ink at 120°C is 1. lX1
It was 0' centipoise.

Ink (■) The above materials were mixed in a ball mill to obtain ink (■). The melt viscosity of this ink is 9.2X1 at 120℃
It was 0.3 centipoise.

Next, ink-■ and ink-■ were coated on a PET film with a thickness of 6 μm using Mayer/<- in this order.

The dry coating weight is 6g/rr each. The total weight of the ink layers was 12 g/rrr, and a thermal transfer material (2) was obtained.

Comparative Example 1 Ink-■ The above materials were mixed and prepared in a ball mill to obtain ink-■. The melt viscosity of this ink is 2.5 at 120'C.
It was x10' centipoise.

Ink-[Phase] The above materials were mixed and prepared in a ball mill to obtain an ink-[Phase]. The melt viscosity of this ink is 1 at 120'C.
．． It was 1×10′ centipoise.

Ink-■ The above materials were mixed in a ball mill to obtain ink-○. The melt viscosity of this ink at 120°C is 1. lX1
It was 0' centipoise.

Next, ink-■, ink-[phase], and ink-○ were layered and coated on a 6 μm thick PET film using a Mayer bar in this order.

The dry coating weight is 4g/rr each. ', the total weight of the ink layers was 12 g/rf, and a thermal transfer material (2) was obtained.

In addition, on the opposite side of the polyester film from the ink-coated side, a back treatment agent of silicone-acrylic-talethane ternary copolymer was applied in advance to a dry coating weight of 0.3 g/rr+'. I used something.

Comparative Example 2 The above materials were mixed in a ball mill to obtain ink-■. The melt viscosity of this ink is 7.5X at 120 °C
It was 10” centipoise.

Ink-■ The above materials were mixed in a ball mill to obtain ink-■. The melt viscosity of this ink is 8.2 at 120'C.
It was X103 centipoise.

Ink-■ The above materials were mixed in a ball mill to obtain ink-■. The melt viscosity of this ink is 8.0X1 at 120℃
It was 0" centipoise.

Next, Ink-■, Ink-■, and Ink-■ were coated on a PET film having a thickness of 6 μm using a Mayer bar in the following order.

The dry coating weight of each layer was 3.5 g/rrf, and the total weight of the ink layer was 10.5 g/d, yielding a thermal transfer material (2).

On the other hand, a facsimile manufactured by Canon (product name: Canofa)
x630) was partially modified to convey the recording medium and the thermal transfer material so that the thermal transfer material and the recording medium have a relative speed as shown in Figure 2, and to cover the conveyance length of the thermal plate and the recording medium. The length was modified to be less than the transport length of the recording medium. The printing conditions are as follows.

Thermal head: 8 pel thick film type full multi-thermal head Heater Size: Main scanning direction 100μm Sub-scanning direction 60μm Thermal transfer material feed amount: Compare the feed amount of the recording medium 11
5 (i.e. n=5) Feeding direction: The feeding direction of the thermal transfer material and the recording medium are opposite (
In other words, in Fig. 3, the feeding direction of the recording medium is the opposite direction to B) Printing speed: 25mm/sec Printing energy: 22mJ/mrr? Next, the above-mentioned thermal transfer materials (1) to (■) were loaded into the apparatus, and a thin line pattern with horizontal lines was printed on facsimile thermal transfer paper.

Next, the image of the Institute of Image Electronics Engineers facsimile test chart No. 2 was transferred to plain paper (manufactured by Jujo Paper Industries, TRW-LA) using the aforementioned thermal transfer material as a received image from the device.

Bekk smoothness: 220 seconds). The evaluation items are as follows.

Density unevenness: Presence or absence of uneven streaks in the main scanning direction in part 1 of ■ ○: The image is homogeneous with almost no streaks observed. Pull: Whether or not whiskers occur at the back end of each kanji character ○:
No occurrence ×: The evaluation results of occurrence are shown below.

〔Effect of the invention〕

As explained above, the heat-sensitive transfer material of the present invention not only provides a transferred image with a uniform print density particularly suitable for double-density recording, but also provides a recorded image with excellent print quality with no scumming, trailing, or collapse. It is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a layer configuration diagram of an example of the thermal transfer material of the present invention, FIG. 2 is a perspective view of an example of a device using the thermal transfer material of the present invention, and FIGS. 3 to 6 are of the present invention. FIG. 2 is a partial side view showing an example in which the heat-sensitive transfer material of 1 is used for double-density recording. l...Thermal transfer material 2...Recorded object 3...Recording head 3a...Heating element

Claims (3)

[Claims] (1) Having a plurality of heat-melting ink layers on a support, the binder of the heat-melting ink layer includes 65 to 40% by weight of ethylene vinyl acetate copolymer and 35 to 60% by weight of wax.
% by weight, and the melt viscosity of each heat-melting ink layer decreases as the distance from the support increases. (2) The heat-sensitive transfer material according to claim 1, wherein each of the heat-melting ink layers has a melt viscosity of 7.5 x 10^3 to 2 x 10^4 centipoise at 120°C. (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 characterized by its short length.