JPH04153090A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To provide the title recording medium excellent in thermal transfer properties at the times of high density printing and high speed printing, imparting a printed image of high resolving power to low smoothness paper and preventing background staining at high temp. by adding two or more kinds of waxes and dye/pigment to a release layer to provide specific heat absorbability to said layer. CONSTITUTION:A thermal transfer recording medium is constituted of a support 1, a release layer 2, an ink layer 3 and an overcoat layer 4. The release layer 2 contains two or more kinds of waxes and dye/pigment and continuously has endotherm of 40-80cal/g within a temp. difference range of 50 deg.C at 40-120 deg.C. By this constitution, transfer properties can be controlled within an energy range from low energy to high energy or within a range from a low temp. environment condition of 0 deg.C to a high temp. environment condition of 100 deg.C and one-dot reproducibility under low energy or low temp. environment can be enhanced and, further, the contamination due to the accumulation of heat under high energy or high temp. environment can be prevented. Since the melt viscosity of the release layer 2 is high because of the added dye/pigment and the release layer is easy to cut at the time of transfer, an excellent printed image is obtained by the synergistic effect with endotherm.

Description

Detailed Description of the Invention [Industrial Application Fields] The present invention has excellent thermal transfer properties especially during high-density printing and high-speed printing, and can produce high-resolution printed images not only on paper with high smoothness but also on paper with low smoothness. The present invention relates to a thermal transfer recording medium that provides clear printed images without background stains.

BACKGROUND ART In recent years, with the rapid development of the information industry, various information processing systems have been developed, and recording methods and devices suitable for each information processing system have also been developed and adopted. As one such recording method, the thermal recording method has recently been widely used because the device used is lightweight, compact, noiseless, and has excellent operability and maintainability.

However, among the recording papers used in the thermal recording method, ordinary thermal recording paper is a color-forming processed paper containing a coloring agent and a color developer, so it is expensive, and the recording can be tampered with. It has the disadvantage of poor storage stability, such as easily developing color due to heat or organic solvents and discoloring the recording layer in a relatively short period of time.

A thermal transfer recording method has recently been attracting particular attention as a method that maintains the advantages of the above-mentioned thermal recording method and compensates for the drawbacks associated with the use of thermal recording paper.

This thermal transfer recording method generally uses a thermal transfer agent formed by melt-coating a thermal transfer ink consisting of a coloring agent dispersed in a heat-melting binder onto a sheet-like support. The layer is superimposed on the recording medium so that it is in contact with the recording medium, and heat is supplied from the support side of the thermal transfer agent using a thermal head to transfer the melted ink layer to the recording medium, thereby applying heat to the recording medium according to the shape. It forms a transfer ink image.

According to this method, it is possible to use the paper as a plain paper recording medium while maintaining the advantages of the thermal recording method, and the disadvantages associated with the use of the thermal recording paper described above can also be eliminated.

However, conventional thermal transfer recording methods are not without drawbacks. In the conventional thermal transfer recording method, the transfer recording performance, that is, the print quality, is greatly affected by the surface smoothness of the recording medium. In some cases, the print quality deteriorates significantly. Moreover, even when using paper, which is the most typical recording medium, highly smooth paper is rather special, and ordinary paper has various degrees of unevenness due to entangled fibers. Therefore, in the case of paper with large surface irregularities, the hot melted ink cannot penetrate into the fibers of the paper during printing, and because it adheres only to the convexities of the surface or the vicinity thereof, the edges of the printed image are sharp. Otherwise, part of the image may be missing, resulting in a decrease in print quality. In order to improve print quality, it may be possible to use a heat-melting binder with a low melting point, but in this case, the heat-transferable ink layer becomes sticky even at relatively low temperatures, resulting in decreased storage stability and recording problems. This causes inconveniences such as staining of non-printed areas of the medium.

There are also examples in which 0.3 to 10% by weight of a rubber elastic substance is added to the ink layer to improve rough paper print quality.

However, with these methods, it was difficult to achieve the desired purpose because the rubber elastic material deteriorated in thermal sensitivity and the ink became difficult to clean.
No. 62-30083, Go-225795).

The inclusion of a rubber-like substance in the ink layer is disclosed in Japanese Patent Application Laid-open No. 54-10.
No. 750, there is also a so-called bridge transfer method which is already known as an attempt at printing on rough paper. This method has drawbacks such as poor image fixing properties and poor transfer in large depressions because the ink layer is transferred by contacting only the uneven areas of the receiving paper.

In addition, in order to improve the above problem, there are products that use specific heat-melting substances such as amide ester compounds, amide alcohol compounds, fatty acid ethanolamide compounds, etc. in the release layer, but especially for high speed printing and high density printing. Transfer using a short heating time has the drawback that the transfer rate, resolution and smearability of the image are insufficient due to insufficient energy for melting and transferring the thermofusible colorant layer.

[Problems to be Solved by the Invention] The purpose of the present invention is to provide excellent thermal transfer properties during high-density printing and high-speed printing, and to provide high-resolution printing not only on paper with high smoothness but also on paper with low smoothness. The second object is to provide a thermal transfer recording medium that provides images and provides clear printed images without background stains under high temperature conditions.

[Means for Solving the Problem] According to the present invention, in a thermal transfer recording medium having a release layer, a heat-melting ink layer, and an overcoat layer on a heat-resistant support, the release layer includes at least two types of wax, and dyes and pigments, and the release layer is continuously heated for 40 to 80 ca within a temperature difference of at least 50°C at 40 to 120°C.
A thermal transfer recording medium characterized by having an endothermic amount of Ω/g is provided.

Here, 40° C. to 120° C. is the temperature applied to the release layer in thermal differential analysis, and the temperature difference is the width of the temperature range showing endothermic ffi of 40 to 80 caΩ/g in thermal differential analysis. Moreover, the endothermic amount indicates the latent heat of fusion of peeling.

The layer structure of the thermal transfer recording medium of the present invention is schematically explained as shown in FIGS. 1 and 2.

In the figure, 1 is a support, 2 is a release layer, 3 is an ink layer, 4 is an overcoat layer, and 5 is an overcoat layer.

The release layer of the present invention contains a small amount of 40caΩ/g to 80% of
Due to the release layer structure having an endothermic amount of CaΩ/g, transferability can be controlled in the energy range from low energy side to high energy side or in the range of low temperature environmental conditions (0°C) to high temperature environmental conditions (50°C). It is possible to improve one-dot reproducibility in a low-temperature environment, and it is also possible to prevent thick lines and contamination due to heat accumulation in a high-energy or high-temperature environment.

In addition, since the release layer of the present invention contains dyes and pigments, the melt viscosity is high (150 to 300 CpS...B at 120°C).
(type viscometer) and the feature that the inside of the peeling layer is easy to break during transfer, and the synergistic effect with the above-mentioned amount of heat absorption makes it possible to provide excellent printed images.

The release layer of the present invention consists of two types of wax: a low melting point wax and a high melting point wax.
Low melting point wax composed of seeds or more is 50℃~80℃
℃ range can be used, and high melting point waxes are 90℃~
A temperature range of 120°C can be used. In addition, the heat absorption amount of low melting point wax and high melting point wax alone is 30 to 55 caf.
Preferably it is in the l/lr range.

If the amount of heat absorbed is large, thermal sensitivity will be reduced and heat accumulation stains will occur under high temperature conditions, while if it is small, image blurring will occur.

The content ratio of low melting point wax and high melting point wax of the present invention is 6
In the range of 0 to 90% to 10 to 40%, preferably 70 to 8
5% to 15 to 30% is good. If there is too much high melting point wax, the thermal sensitivity will decrease, and if it is too little, the entire transfer will occur on the low energy side, resulting in a thick image.

Furthermore, the content ratio of the dye and pigment of the present invention is 2 to the total amount of wax.
-20%, preferably 5-13%.

If there is too much dye or pigment, the smear properties of the image will be poor, and if there is too little, transfer control will be insufficient, resulting in thick lines and poor one-dot reproducibility.

As a release layer material of the present invention Paraffin wax is a low melting point wax.

Examples include oxidized paraffin wax, campria wax, montan wax, and lanolin synthetic wax.

Examples of the high melting point wax include oxidized polyethylene wax, polyethylene wax, and various modified waxes.

When the release layer of the present invention has a fine particle structure, it is easy to tear during printing, has excellent transferability, and has excellent one-dot reproducibility, so it is suitable for high-density printing and high-speed printing.

The fine particle structure of the present invention is formed by dispersing the wax described above in a solvent and coating it. Examples of solvents include toluene, xylene, ethyl acetate, methyl ethyl ketonan, acetone, methanol, ethanol, impropatol,
Examples include ethylselosoneb and cyclohexanone.

Note that the size of the fine particles is 0. O1 to 0.8 μm, preferably 0.05 to 0.4 μm. (If the thickness is too large, the thermal sensitivity will be lowered, and the reproducibility of one dot will be lowered and the transfer efficiency will be lowered.) The thickness of the peeling layer is 0.1 to 10 .mu.m, preferably 1 to 5 .mu.m.

For the ink layer of the present invention, those used in conventional thermal transfer recording media can be used, but preferably a colorant and a melt index of 800 to 3000 g/10 m1n, preferably 1000 to 2000 g/10 m1n of ethylene and ethyl acrylate. or a copolymer with vinyl acetate (ethylene content 70-90%, preferably 70%)
~85% by weight).

Melt index is 800-3000g/101
Because of its high n, it melts and flows in a short time, making it easy to wet the transferred material, and the copolymer's ethyl acrylate, acetic acid, and vinyl content of 10 to 30% improves its adhesion to paper. is appropriate. As an ethylene-ethyl acrylate copolymer having a melt index of 800 to 3000 g/10 m1n and an ethylene content of 70 to 90%, MB-91 manufactured by Nippon Unicar Co., Ltd.
0 (Ml = l!00g/10sin, EA-2
8%), MB-900 (Ml-1500g/1
0sin.

EA-23%), etc.

Melt index is 800-3000g/10I
Iins ethylene content of 70-90%
As the vinyl acetate copolymer, MB-850 (M1~800g/10iin, manufactured by Nippon Unicar Co., Ltd.,
VA-22%), MB-010 (Ml-1200g/
10m1n, VA-25%), MB-080 (M
l=2500g/1011in.

VA-19%), etc.

When the melt index is less than 800, thermal sensitivity decreases and high energy is required for thermal transfer.

Moreover, if it is larger than 3000, it is not possible to create a strong image on rough paper.

The ink layer of the present invention may contain styrene-based and/or
Alternatively, styrene derivatives, vinyl, acrylic, paraffin, polyethylene, campria, carnauba wax, etc. may be added.

As the coloring agent, it is preferable to use organic or inorganic dyes or pigments that have properties suitable for recording materials. For example, it is preferable to have sufficient coloring density and not discolor or fade due to light, heat, humidity, etc. Further, it may be a substance that is colorless when not heated, but develops color when heated, or a substance that develops color when it comes into contact with a substance coated on a transfer target.

Specific examples include pigments and dyes such as carbon black, titanium dioxide, red iron oxide, Lake Red C1 Fast Sky Blue, benzidine yellow, phthalonanine green, phthalocyanine blue, direct dyes, oil dyes, and basic dyes.

The ink layer of the present invention may be prepared by kneading a colorant and the above-described specific copolymer into a composition, and applying the composition to the surface of the release layer using an appropriate coating method.

As for the composition, the colorant and the above-mentioned specific copolymer are blended so that the weight of the colorant is 1 to 80%, preferably 5 to 30% of their total weight.

Further, the fine particle structure is formed by dispersing the composition in a solvent and coating it. Solvents include toluene, xylene, ethyl acetate, methyl ethyl ketone, acetone,
Examples include methanol, ethanol, isopropanol, ethyl cellosolve, and cyclohexanone.

The thickness of the ink layer provided as above is 0.1 μr.
Approximately A to 10 μm mark, preferably 1 μm to 5 μm
It is μl.

When the ink layer of the present invention has a fine particle structure, it is easily cut during printing, has excellent transferability, and further has excellent one-dot reproducibility, and is therefore suitable for high-density printing and high-speed printing.

The size of the fine particles is 0.01 to 0.8 μts.
, preferably 0.05 to 0.4 μm. If it is too large, thermal sensitivity will decrease, and if it is too small, one-dot reproducibility and transfer efficiency will decrease.

For the overcoat layer of the present invention, materials used in conventional thermal transfer recording media can be used, but preferred are vinyltoluene-butadiene copolymer and particulate ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate. Due to the structure whose main component is a copolymer. In this case, by imparting unique elasticity to the thermoplastic resin, the contact density with the rough paper surface can be easily increased by the head pressure during printing, improving the rough paper print quality. The adhesive effect of the adhesive increases the adhesion to the irregularities of the rough paper, making it possible to improve the resistance to image falling off.

Furthermore, because it has a particulate structure made of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer, the endothermic latent heat from the release layer to the ink layer to the overcoat layer is small and thermal transfer can be performed with low energy, making it suitable for high-density applications. Suitable for thermal transfer during printing and high-speed printing.

The ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer used in the overcoat layer is the same as that used in the ink layer described above, except that vinylxylene-butadiene copolymer is used instead of vinyltoluene-butadiene copolymer. You may also use

The composition ratio of vinyltoluene or a copolymer of vinylxylene and butadiene to ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is in the range of 8:2 to 2.8, preferably 73 to 4:6. Good range.

If the amount of vinyltoluene-butadiene copolymer is too large, thermal sensitivity will decrease, and if it is too low, rough paper printing quality will decrease.

In addition to the above-mentioned main components, the overcoat layer of the present invention may optionally contain styrene-based and/or styrene derivative-based, vinyl-based, acrylic-based resins, and waxes such as paraffin wax, polyethylene wax, candelilla wax, and carnauba wax. It is also possible to add other substances.

The overcoat layer of the present invention has a fine particle structure when the composition is dispersed in a solvent and coated on the surface of the ink layer.

Examples of the solvent include toluene, xylene, ethyl acetate, methyl ethyl ketone, acetone, methanol, ethanol, isopropanol, ethyl cellosolve, and cyclohexanone.

The thickness of the overcoat layer provided as described above is 0.
．． Approximately 1 μm to 10 μm, preferably 1 μm
It is m~5μ.

In addition, the size of the fine particles is 0.01 to 0.8 μ■,
Preferably, it is 0.05 to 0.4 .mu.m. If it is larger than 0.8 .mu.m, the thermal sensitivity will decrease, and if it is smaller than 0.01 .mu.m, the one-dot reproducibility and transfer efficiency will decrease.

Examples of the support for the thermal transfer recording medium of the present invention include relatively heat-resistant plastic films such as polyester, polycarbonate, triacetyl cellulose, nylon, and polyimide, as well as glassine paper, condensate paper, metal foil, and the above. A composite of each material can be exemplified.

Examples of the composite include aluminum/paper board combination, metal-deposited paper, and metal-deposited plastic film. The thickness of the support is preferably about 2 to 15 μm when considering a thermal head as a heat source for thermal transfer, but it is preferable to use a heat source that can selectively heat the thermal transferable ink layer, such as a laser beam, for example. There are no particular restrictions in this case. In addition, when using a thermal head, silicone resin should be applied to the surface of the support that comes into contact with the thermal head.
By providing a heat-resistant protective layer made of fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc., the heat resistance of the support can be improved, or supports that could not be used conventionally can be provided. Body materials can also be used.

Application methods include hot melt coating and solvent coating methods such as gravure coating, roll coating, air knife coating, and wire barcoding, as well as gravure printing,
Printing methods such as gravure offset printing and digital screen printing may also be used.

In the present invention, an adhesive layer may be provided to improve the adhesion between the base material, the release layer, the ink layer, and the overcoat layer.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Paraffin wax (Nippon Seiro HNP-10) (
mp72℃) 10.5 parts by weight Lasox wax (Yoshikawa Oil Co., Ltd. FP-14) (m
p70℃) 4.54 parts by weight oxidized polyethylene wax (PED-52 manufactured by Hoechst)
1) (ap 105 °C) 3.78 parts by weight carbon black 1.2 parts by weight Toluene 80 parts by weight of the composition was dispersed in a ball mill, and a peeled M layer with a thickness of 4 μm was formed using a gravure roll coating method. Carbon black on the surface 1.5 parts by weight ethylene-ethyl acrylate copolymer [MB-910 (manufactured by Nippon Unicar Co., Ltd., melt index 1100 g/lomIn).

A composition of 90 parts by weight of 22 toluene/methyl ethyl ketone (1/1) containing EA was dispersed in a ball mill and an ink layer with a thickness of 3 μl was formed using a gravure roll coating method. Polymer 5 parts by weight (vinyltoluene/butadiene 85/15) ethylene-ethyl acrylate copolymer 5 parts by weight (MB-910 Nippon Unicar Kansei Melt Index 1100g/10ωinE,A
Content: 28%) A composition of 90 parts by weight of methyl ethyl ketone/toluene (1/1) was dispersed using a ball mill, and a 2 μm thick fixability improving layer was formed using a gravure roll coating method to create a thermal transfer recording medium (A). did.

Example 2 In Example 1, oxidized paraffin wax (Nihon Seiro 0X-W-1) was used instead of HNPlo in the release layer composition.
A thermal transfer recording medium (B) was prepared in the same manner except that the temperature was changed to 5 mp (72° C.).

Example 3 In Example 1, the release layer composition was changed to polyethylene wax (instead of oxidized polyethylene wax PED-521).
A thermal transfer recording medium (C) was prepared in the same manner except that Mitsui Petrochemical Co., Ltd. 4052E mp110°C) was used.

Example 4 In Example 1, the composition ratio of low melting point wax and high melting point wax in the release layer composition was changed from 80:20 to 70:30.
A thermal transfer recording medium (D) was prepared in the same manner except that .

Example 5 A thermal transfer recording medium (E) was prepared in the same manner as in Example 1 except that the composition ratio of dye and pigment to wax in the release layer composition was changed from 6:94 to 10:90.

Comparative Example 1 A thermal transfer recording medium (A) was prepared in the same manner as in Example 1 except that the release layer composition was only a low melting point wax.

Comparative Example 2 A thermal transfer recording medium (former) was prepared in the same manner as in Example 1 except that the release layer composition was only a high melting point wax.

Comparative Example 3 A thermal transfer recording medium (c) was prepared in the same manner as in Example 1 except that only wax was used as the release layer composition.

The temperature range in which the amount of endotherm in the thermal differential analysis in Examples 1 to 5 and Comparative Examples 1 to 3 shows 40 to 80 cal/g is as follows.

Example 1 40°C to 100°C 〃 2 43°C to 95°C // 3 55°C to 115°C / l 4 50°C to 110°C 〃 5 36°C to 100°C Comparative example 1 40°C to 70°C // '; ) 65℃～100℃
〃Thermal transfer recording media (A) to (E) of Examples obtained as above to 355°C to 100°C and thermal transfer recording media (A) to (C) of Comparative Examples were heated in a thermal transfer printer (prototype machine). ...The head has 18 heads/mu), the head energy is 14 mj/dat, and the printing speed is 1.
Printing was performed at 50 characters/second. As the transfer paper, paper with a hex smoothness of 25 seconds was used. The printing results are shown in Table-1.

In addition, each evaluation was performed according to the following method.

(1) Resolution: O Clear and high resolution, similar to the type on printed matter △ Slightly unclear or legible characters × Extremely unclear, difficult to read (2) Thick text (in the limit sample of the 5-step method) Evaluation) The text in the rank 5 column clearly shows the east part of the gate.

// 4 1/ East is somewhat clear //
3 // The east is a little unclear〃 2
・L East is unclear... 1 〃 East is extremely unclear (3) Smear stain (smear property) (Evaluated using limit sample of 5-step method) (Coat the solid area 50 times with a lab tester.

(Visually observe the stains on the imaged area at that time) Rank 5 No stains 4 Slight stains 3 Slightly stains 2 Slight stains 1 Very strong stains (4) Rough paper printing quality ○ Smoothness 10~ 30 seconds of solid printing on the paper is completely buried.

△ There are some white blank areas in the solid printing area of paper with a smoothness of 10 to 30 seconds.

×f Paper with smoothness of 10 to 30 sec has blank white areas all over the solid printed area.

(5) Thermal sensitivity (evaluated using limit sample of 5-step method) 1000
Reproduction ratio rank of 1 dot number 590% or more - 100% 〃 470% or more - less than 90%〃 350% or more - less than 70%//') 3 Q% or more - less than 50%/l 1
0% or more - less than 30% (6) Heat storage stain (evaluated using limit sample of 5-step method) 50℃
Visual observation of contamination from continuous solid printing in an environment of
Strong generation // 1 // Extremely strong generation [Effects of the invention] As is clear from the above explanation, the thermal transfer recording medium of the present invention has excellent thermal transfer properties during high-density printing and high-speed printing, and paper with high smoothness is Of course, high-resolution printed images can be provided even on low-quality paper.

In addition, it is possible to obtain sharp images without thickening the characters, and there is also much less smearing than before, and there is no thickening of the characters or heat accumulation stains under high-temperature conditions, resulting in extremely clear images. This has the effect that an image can be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams schematically explaining the layer structure of the thermal transfer recording medium of the present invention. DESCRIPTION OF SYMBOLS 1...Support, 2...Peeling layer, 3...Ink layer, 4...Overcoat layer, 5...Adhesive layer.

Claims (1)

[Claims] In a thermal transfer recording medium having a release layer, a heat-melting ink layer, and an overcoat layer on a heat-resistant support, the release layer contains at least two or more kinds of waxes and dyes and pigments, and the release layer has a temperature of 40 to 120°C. at least a temperature difference of 50
A thermal transfer recording medium characterized in that it has a continuous endothermic amount of 40 to 80 cal/g within a temperature range of .degree.