JPH0494968A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To be excellent in thermal transfer in printing for high density and in high speed printing, to provide a high resolution printing image even to a low smoothness paper and to provide a clear printing image even under high temperature conditions by a method wherein a thermal fusible ink layer contains a coloring agent, ethylene copolymer resin of a specific ratio of a vinyl acetate quantity or an ethylacrylate quantity and silicon powder. CONSTITUTION:In a thermal transfer recording medium having a peeling off layer 2, a thermal fusible ink layer 3, and an overcoat layer 4 on a heat resistant base material 1, the thermal fusible ink layer 3 contains a coloring agent, ethylene-vinyl acetate copolymer and/or ethylene-ethylacrylate copolymer resin of which VA value (vinyl acetate amount) or EA value (ethyl-acrylate amount) is 20-35wt.%, and silicon powder. A frictional coefficient in the ink layer decreases by containing the silicon powder. Falling off of the ink layer against rubbing is further improved, and stains by rubbing under high temperature conditions can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has excellent thermal transfer properties especially during high-density printing and high-speed printing, and can print high-resolution 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 under high-temperature conditions.

[Prior 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 apparatus used is lightweight, compact, noiseless, and has excellent operability and maintainability.

However, among the recording papers used in thermal recording methods, ordinary thermal recording paper is a color-forming processed paper containing a color former and a color developer, and is therefore expensive. It has disadvantages in terms of recording 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.

It maintains the advantages of the thermal recording method described above and compensates for the disadvantages associated with the use of thermal recording paper! Thermal transfer recording method has recently been attracting particular attention.

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, while maintaining the advantages of thermal recording, it can be used as a plain paper recording medium, and the disadvantages associated with the use of 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. This results in a significant drop in print quality. 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 during printing cannot penetrate into the paper fibers, and because it adheres only to the convexities of the surface or the vicinity thereof, the edges or sharp edges of the printed image may be affected. The print quality may deteriorate if the image is not properly printed or part of the image is missing. In order to improve printing quality, it may be possible to use a heat-melting binder with a low melting point. In this case, the heat-transferable ink layer becomes sticky even at relatively low temperatures, resulting in a decrease in storage stability and recording. This causes inconveniences such as staining of non-printed areas of the medium.

In some cases, 0.3 to 10% by weight of a rubber elastic substance is added to the ink layer to improve rough paper printing. 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. 60-225795). It is known from JP-A-54-10750 that the ink layer contains a rubber-like substance, and a so-called bridge transfer method 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 areas because the ink layer contacts the irregularities of the receiving paper during transfer.

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. In transfer using a short heating time, there is a drawback that the smear property of the image is not sufficient to change the transfer rate and resolution of the image due to insufficient energy for melting and transferring the heat-fusible coloring material 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. An object of the present invention 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 Problems] According to the present invention, in a thermal transfer recording medium having a release layer, a heat-melt ink layer, and an overcoat layer on a heat-resistant support, the heat-melt ink layer contains a colorant and a VA value. (Amount of vinyl acetate) or EA (Amount of ethyl acrylate) value is 20 to 35
wt% of ethylene-vinyl acetate copolymer and/or ethylene-
A thermal transfer recording medium is provided that contains an ethyl acrylate copolymer resin and silicone powder.

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 is provided to facilitate the separation of the ink layer from the support when the coloring material layer is melt-transferred. It is preferable to use a substance that melts into a low viscosity liquid.

Such substances include natural waxes such as beeswax, spermaceti wax, candelilla wax, carnauba wax, rice bran wax, montan wax, and oshikerite, paraffin wax,
Examples include petroleum-based waxes such as microcrystalline wax, various modified waxes, hydrogen-based waxes, long-chain fatty acids, and the like. The release layer of the present invention is mainly composed of wax having a melting point of 50 to 90°C as described above, but ethylene ethyl acrylate or ethylene-vinyl acetate copolymer or the like may be mixed therein if necessary. Ru.

When the release layer of the present invention has a fine particle structure, it is easy to break 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 above-mentioned wax in a solvent and coating it. Examples of solvents include toluene, quinolene, ethyl acetate, methyl ethyl ketonan, acetone, methanol, ethanol, isopropanol,
Examples include ethylselosoneb and cyclohexanone.

The size of the fine particles is preferably 0.01 to 0.8 μm, preferably 0.05 to 0.4 μm. (If it is too large, the thermal sensitivity will be lowered, and if it is too small, the one-dot reproducibility and transfer efficiency will be lowered.) The thickness of the release layer is 0.1 to 10 μM, preferably 1 to 5 μL.

The ink layer of the present invention has a coloring agent and a VA value (acetate vinyl) or E
A thermoplastic ink layer composed of an ethylene-vinyl acetate copolymer or an ethylene ethyl acrylate copolymer having an A (ethyl acrylate amount) value of 20 to 35 vt% and silicone powder, wherein the VA value or EA value of the resin is 20-3
Because it is as high as 5wt%, both the adhesive force between the release layer and the ink layer and the adhesive force within the ink layer are strong, and the ink layer does not fall off due to the cost of transferring the transfer paper and thermal transfer recording medium due to the thermal head pressure. be. Furthermore, the inclusion of silicone powder reduces the friction coefficient within the ink layer,
It has the advantage of further improving the shedding of the ink layer in relation to cost and preventing staining due to scratches under high temperature conditions.

Here, the VA value or EA value is a value determined by the saponification method.

As the ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer having a VA value or EA value of 20 to 35 νt% of the present invention, EV manufactured by Mitsui DuPont Polychemical Co., Ltd.
A-310 (VA value 25wt!?6), E VA
210 (VA value 28wt5%), EVA-220 (V
A value 28wt%), EVA-360 (VA value 25wt%)
%) etc.

Also, MB-730 (EA value 35wt) manufactured by Konica Nippon
%), MB-910 (EA value 28wt%), MB-9
00 (EA value 23vt%), etc.

When the VA value or the EA value is less than 20 wt%, the adhesive force within the ink layer and the adhesive force between the ink layer and the release layer become weak, causing the ink layer to fall off. On the other hand, if it is more than 35 wt%, the cohesive force within the ink layer increases, resulting in poor transferability and failure to produce clear images.

Examples of the silicon powder of the present invention include XC99-301 and XC99-501 manufactured by Toshiba Silicone ■.

The composition ratio of the ethylene-vinyl acetate copolymer or ethylene ethyl acrylate copolymer of the present invention is in the range of 1 to 10% silicon powder to 90 to 99% resin, preferably silicon powder to 92 to 97% resin. A range of 3 to 8% is preferable.

If the amount of silicon powder is more than 10%, the resolution will decrease,
Also, if it is less than 1%, there is a drawback that stains may occur.

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.

The colorant may be any organic or inorganic dye or pigment that has properties suitable for use as a recording material. For example, it is preferable to use a material that has sufficient color density and does not change color 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, phthalocyanine 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 colorant j is 1 to 80%, preferably 5 to 309% by weight of the total weight of the colorant and the specific copolymer.

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 described above is 01 μm to
Approximately 10 μm or more, preferably 1 μm to 5 μm
It is.

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.

Note that the size of the fine particles is 0. O1~0.8μm,
Preferably it is 0.05 to 0.04 μm. If it is too large, the thermal sensitivity will decrease, and if it is too small, the 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 preferably vinyltoluene-butadiene copolymer and particulate ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer. By giving the thermoplastic resin a unique elasticity due to its composition mainly composed of polymers, the contact density with the rough paper surface can be easily increased by the head pressure during printing, which improves the rough paper printing quality. The adhesion effect of the Gen copolymer increases adhesion to the unevenness of rough paper, making it possible to improve image fall-off.

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

The ethylene-vinyl acetate copolymer or ethylene ethyl acrylate copolymer of the present invention is the same as that used in the ink layer described above, and in addition to vinyltoluene-butadiene copolymer, vinylquinlene-butadiene copolymer may also be used. .

The composition ratio of the vinyltoluene-butadiene copolymer and the ethylene-vinyl acetate copolymer or the ethylene-ethyl acrylate copolymer of the present invention is in the range of 8.2 to 2.8, preferably 7.
A range of 3-4; 6 is good.

If the amount of vinyltoluene-butanene copolymer is too high, the heat sensitivity will decrease, and if it is too low, the rough paper print 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, paraffin wax, polyethylene wax, candelilla wax, carnauba wax, etc. Waxes may also be added.

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
~5 μm.

The size of fine particles is 0.01-0.8μ,
Preferably it is 0.05 to 04 .mu.m; if it is larger than 0.08 .mu.m, the thermal sensitivity will be reduced, and if it is smaller than 0.001 .mu.m, the one-dot reproducibility and transfer efficiency will be reduced.

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. Composites of each material can be exemplified.

Examples of the composite include an aluminum/paper composite, metal-deposited paper, and metal-deposited plastic film. When considering a thermal head as a heat source during thermal transfer, the thickness of the support is preferably about 2 to 15 μm.For example, when using a heat source such as a laser beam that can selectively heat the thermal transferable ink layer. There are no particular restrictions. Also, if you use a heat head,
The heat resistance of the support is improved by providing a heat-resistant protective layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. on the surface of the support that comes into contact with the heat head. Alternatively, it is also possible to use support materials that have not been previously available.

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 printing methods such as gravure printing, gravure offset printing, and silk screen printing.

In addition, in the present invention, the base material, the release layer, the ink layer 1, i-
An adhesive layer may be provided to improve the adhesiveness of the barcode layer.

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

Example 1 Candelilla wax 8 parts by weight Paraffin wax 8 parts by weight Monitan wax on a 3.5 μm thick polyester film with a heat-resistant layer on the back side
4 parts by weight toluene
9. 80 parts by weight of the composition was dispersed in a ball mill and a release layer with a thickness of 4 μm was formed using a gravure roll coating method, and then on the surface: 1.5 parts by weight of carbon black 9. Ethylene-vinyl acetate copolymer. 5 parts by weight EVA-21
0 (manufactured by DuPont Mitsui Polychemical ■VA value 28wt9°・silicon powder 0.5 parts by weight (XC99-501 manufactured by Toshiba Silicon ■) Toluene/methyl ethyl ketone (1/1) 88.5 parts by weight of the composition was dispersed with a ball mill. An ink layer with a thickness of 3 μm is formed using a gravure roll coating method, and then 5 parts by weight of vinyltoluene-butadiene copolymer (vinyltoluene/butadiene 85/15) and 5 parts by weight of ethylene-ethyl acrylate copolymer are coated on the surface. MB-910 Konica Japan Melt Index 1100g/10m1nE, 1
A composition of 90 parts by weight of methyl ethyl ketone/toluene (1/1) with a content of 28% was dispersed using a ball mill, and a fixability improving layer with a thickness of 2 μcm was formed using a gravure roll coating method to create a thermal transfer recording medium (A). did.

Example 2 In Example 1, ethylene-ethyl acrylate polymer (MB-210) was used instead of EVA-210 in the ink layer composition.
A thermal transfer recording medium (B) was prepared in the same manner except that EA 910 (manufactured by Nippon Konica Mari) was used (EA28vt%).

Example 3 A thermal transfer recording medium (C) was prepared in the same manner as in Example 1 except that the silicon powder content ratio of the ink layer composition was changed from 5% to 896.

Example 4 In Example 1, the ink layer composition was replaced with silicone powder
A thermal transfer recording medium (D) was prepared in the same manner except that C99-501 was replaced with XC99301.

Example 5 A thermal transfer recording medium (E) was prepared in the same manner as in Example 1 except that the release layer was replaced with hot melt coating.

Comparative Example 1 A thermal transfer recording medium ( b) was created.

Comparative Example 2 A thermal transfer recording medium (b) was prepared in the same manner as in Example 1, except that EVA210 was used as the ink layer composition.

Thermal transfer recording medium (A) of the example obtained as described above
(E) and the thermal transfer recording media (a) to (b) of the comparative example were printed on a thermal transfer printer (prototype machine...the head was 18 pieces/mm).
) with a head energy of 14 mj/dat.

Printing was performed at a printing speed of 150 characters/second. As the transfer paper, paper with a Beck smoothness of 25 seconds was used.

The printing results are shown in Table-1.

In addition, each evaluation was performed using 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 characters in the rank 5 column clearly appear in the east of the gate.

// 4 ／〆 East is a little clear //
3 // East slightly unclear // 2
/〆 East or indistinct // I II
The east part is extremely unclear (3) Smearing (smearing) (Evaluated using a limit sample of the 5-step method) (The east part was rubbed 50 times using a Lahoter tester.

(Visually observe the stains on the imaged area) Rank 5: No stains 4 // Slight stains 3 // Slight stains 2 ・・ Strong stains 1 // Very strong stains (4) Rough carpet printing product O Solid printing on paper with smoothness of 10 to 30 seconds or completely buried.

Δ There are some white blank areas in the solid printed area of paper with a smoothness of 10 to 30 sec.

* There is a white blank part or the entire surface in the solid printing part of the paper with a smoothness of 10 to 30 seconds.

(5) Thermal sensitivity (evaluated using limit sample of 5-step method) 1000
Reproduction ratio rank of 1 dot number 590% or more - 100% / l 470% or more - less than 90% 17350% or more - less than 70% l 230% or more - less than 50% l - 10% or more - less than 30% ( 6) Dirt during printing (evaluated using limit sample of 5-step method) 4
Visual observation of stains on 100 consecutive A-4 sheets printed under 0°C condition with head energy of 14 mj/dot Rank 5: No stains // 4 /〆 Slight stains // 3 /〆 Slightly strong stains // ') tt Strong generation... 1 〃 Extremely strong generation (7) Blocking Layer a polyester film on the surface of the overcoat layer on each side and heat at 50°C under a load of I kg/C-.
After storage for 24 hours, the polyester film was peeled off, and the presence or absence of blocking was determined based on whether the polyester coating was attached.

[Effects of the Invention] As is clear from the above description, the thermal transfer recording medium of the present invention has excellent thermal transfer properties 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. can be given.

In addition, sharp images can be obtained without thickening of characters, and furthermore, image smearing (smearing) is significantly less than before.

Furthermore, it has the effect that extremely clear images without staining can be obtained during continuous printing under high temperature conditions.

[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 body, 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-melt ink layer, and an overcoat layer on a heat-resistant support, the heat-melt ink layer contains a colorant and a VA value (vinyl acetate amount) or an EA (vinyl acetate amount).
1. A thermal transfer recording medium comprising an ethylene-vinyl acetate copolymer and/or an ethylene-ethyl acrylate copolymer resin having an ethyl acrylate content of 20 to 35 wt% and silicon powder.