JPH04173292A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To prevent the transfer of the component of a thermal transfer layer to the rear of a base material or to the heat-resistant protective layer provided to the rear of the base material by applying a composition containing a specific inorg. fine powder as the second thermal transfer layer. CONSTITUTION:A thermal transfer recording medium is formed by providing the first thermal transfer layer being a coloring layer on a base material and providing the second thermal layer thereon. As the base material, a plastic film, cellophane or paper with thickness of 2-20mum relatively excellent in heat resistance can be used. The second thermal transfer layer is formed by applying a composition containing diatomaceous earth fine powder and has thickness of 0.05-5.0mum. Diatomaceous earth is ground and/or classified to be used as a fine powder having a mean particle size of 0.5-10mum. By this method, the diatomaceous earth powder is exposed from the surface of the second thermal transfer layer in a proper state to prevent the direct contact of the rear of the base material with the surface of the thermoplastic resin of the second thermal transfer layer and the resin enters voids to obtain high anchoring effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvement of a thermal transfer recording medium used in a thermal transfer recording device using a thermal head for word processors, facsimile machines, bar codes, etc. More specifically, while maintaining high thermal sensitivity such as coverage and flatness on paper with low smoothness and dot reproducibility, the components of the thermal transfer layer migrate to the back side of the base material during long-term storage at high temperatures. 11-shi,
This invention relates to a thermal transfer recording medium that prevents printing and running troubles by improving storage stability.

[Conventional technology]

Thermal transfer recording method is widely used because the device is simple, has low noise, is small, low cost, and can easily record on plain paper. However, the print quality is easily affected by the surface smoothness of the transfer paper, and it has been difficult to make clear prints on the transfer paper with poor surface smoothness.

In addition, as the speed and resolution of thermal heads have increased in recent years, it has become easier for thermal heads to accumulate heat, and as a result, the temperature of the surrounding area of the heat generating part also rises, making it easier for background stains to occur on the transfer paper. Challenges have also arisen.

Recently, in order to solve the above problems, one side of the base material (
A heat-resistant protective layer is provided on the back side (hereinafter referred to as the back side) for the purpose of preventing stickiness, a heat-melting ink layer on the other side of the base material (hereinafter referred to as the front side) has a laminated structure, and the first thermal transfer layer, which is a colored layer, is provided on the other side (hereinafter referred to as the front side) of the base material. Furthermore, the second feature is improved printing performance on low-smooth paper.
Styrene resin, acrylic resin, polyamide resin, butyral resin, with adhesion properties (2) and dirt resistance (1).
A second thermal transfer layer is provided, which is made of a thermoplastic material such as vinyl chloride-vinyl acetate copolymer resin or ethylene-vinyl acetate copolymer resin, mixed with tackifier resin, wax, colorant, etc. as necessary. The structure is common.

However, when ribbons with such a structure are stored at high temperatures or for long periods in a rolled state, components of the top thermal transfer layer migrate to the heat-resistant protective layer on the back side, which often causes problems in printing and running.

According to the structure of conventional thermal transfer recording media, printing properties such as cover wrap properties on low-smooth paper, dot reproducibility, and background stain resistance have been solved to some extent. On the other hand, in order to obtain clear printing due to high thermal sensitivity, it is necessary to use a thermoplastic resin with a low softening point as the main component of the I/tub layer, which is the second thermal transfer layer. However, when a resin with a low softening point is used for the top layer, which is the second thermal transfer layer, if it is stored in a roll at high temperatures or for a long period of time, the resin of the top layer may be formed on the back of the base material that is in direct contact with it or on this back surface. The print quality on low-smooth paper decreases due to a decrease in cover wrap properties, the print quality decreases due to head misalignment of the thermal head, the stick phenomenon occurs, and the print quality in the cassette decreases. Problems such as problems with ribbon running occurred.

In other words, conventional thermal transfer recording media had the problem of being unable to achieve both high-temperature and long-term storage stability, cover-wrap performance on low-smooth paper, dot reproducibility, and stain resistance. .

[Problem to be solved by the invention]

The purpose of the present invention is to prevent the components of the thermal transfer layer from migrating to the JA back side or the heat-resistant protective layer provided on this back side during high temperature and long-term storage, which could not be achieved with conventional thermal transfer recording media. The purpose of this invention is to provide a thermal transfer recording medium that has greatly improved the clarity of transfer to transfer paper, which has poor properties, and the background smearing of the transfer paper.

[Means to solve the problem]

As a result of intensive research to solve the above problem, the present inventors found that the problem could be solved by applying a blended composition containing a specific inorganic fine powder as the second thermal transfer layer, and completed the present invention.

That is, the thermal transfer recording medium of the present invention has a laminated structure in which a first thermal transfer layer, which is a colored layer, is provided on the substrate and a second thermal transfer layer is further provided thereon. It is characterized in that it is formed by coating a blended composition containing fine diatomaceous earth powder as a thermal transfer layer.

Next, the configuration of the present invention will be explained.

As 28, I, a plastic film having relatively excellent heat resistance such as polyester, polycarbonate, polyimide, etc. having a thickness of 2 to 2 Qltm, cellophane, paper, etc. can be used. If necessary, a heat-resistant protective layer or an anti-stick layer made of a silicone-modified polymer, a fluorine-based polymer, or the like may be provided on the surface in contact with the thermal head.

The first thermal transfer layer consists of a hot melt ink with a colorant, a vehicle, and various additives. As the coloring agent, carbon black, organic pigment, dye R1, etc. can be used alone or in combination. It is preferable to select a material that has sufficient color density and does not discolor or fade due to light, heat, temperature/humidity, solvents, etc. As a vehicle, the melting point is 45 ~] 2
0 'C wax is the main component, and one or more types specified by paraffin wax, carnauba wax, microcrystalline wax, candelilla wax, polyethylene wax, wood wax, beeswax, fatty acid amide, fatty acid ester, etc. However, the present invention does not particularly limit it. In addition to the above-mentioned colorant vehicle, the hot-melt ink may contain a fixing agent made of a thermoplastic resin, if necessary.
Various additives such as dispersants and leveling agents may be added.

The composition and thickness of the thermal transfer layer are determined by the required printing density and thermal sensitivity, and the thickness is 0.1 to 1.0 (t
, preferably 2 to 5μ.

The second thermal transfer layer is formed by coating a blended composition containing fine diatomaceous earth powder. The thickness is 0.05~5. 0 μm, preferably 0.1 to 2.0 μm. Furthermore, a release layer or an adhesive layer may be provided between the base material and the first thermal transfer layer, if necessary. The blended composition contains a thermoplastic resin as a main component, diatomaceous earth fine powder, and a volatile solvent, and if necessary,
Additives such as softening point regulators, waxes, colorants, surfactants, and leveling agents may also be added.

The main component thermoplastic resins are styrene resins, acrylic resins, polyamide resins, butyral resins, vinyl chloride-vinyl acetate copolymer resins, ethylene-vinyl acetate copolymer resins, etc., and have a softening point of 50.
-200°C, preferably 70-1-50°C, one or more thermoplastic resins are used. In order to uniformly mix the diatomaceous earth fine powder and to easily coat the blended composition in a thin film form on the first thermal transfer layer, the resins to be blended should be selected to be soluble in volatile solvents. is preferred.

Examples of volatile solvents include alcohols, ketones, and esters. The amount of solvent used depends on the particle size of the resin and diatomaceous earth used, their mixing ratio, the type of solvent, the coating method, and the thickness of the second thermal transfer layer, but it is between 50 and 50 ml.
99.5% by weight is good.

Examples of the softening point adjusting agent include low-to-medium molecular weight resins such as adhesive resins, specifically ketone resins.

The diatomaceous earth that is an essential component of the second thermal transfer layer, that is, the blended composition, is one or two types of diatomaceous earth made of normally produced diatomaceous earth and/or silicic acid earth other than diatomaceous earth. More than one species can be used. Generally, diatomaceous earth is obtained as raw soil with a particle size in the range of 1 to 120 μm, but in the present invention, this is pulverized and/or classified to form a fine powder with an average particle size in the range of 0.5 to 10 μm. Use. If the average particle diameter is less than 0.5 μm, the storage stability will not be improved, and if it exceeds Otlm, the printing performance will deteriorate. The ratio of the diatomaceous earth fine powder contained in the second thermal transfer layer is preferably 0.5 to 25% by weight; similarly to the particle size, if it is less than 0.5% by weight, the storage stability will not be improved, and if it exceeds 25% by weight. and printability deteriorates.

The method for preparing the blended composition to be applied to the second transfer layer involves using a single or mixed solvent that dissolves the thermoplastic resin, and adding the thermoplastic resin, diatomaceous earth fine powder, and, if necessary, the additives. In addition, there are methods of mixing and stirring, methods of kneading the above-mentioned mixture using a kneading machine such as a roll mill or kneader, and then letting down the mixed material with a solvent, but basically the thermoplastic resin is mixed with a solvent. It is important to completely dissolve the diatomaceous earth powder and mix it uniformly.

The method for forming the first thermal transfer layer and the second thermal transfer layer is to apply the heat-melt ink of the first thermal transfer layer to the surface of the base material or a base material provided with a heat-resistant protective layer on the back side as necessary by a hot-melt method or a solvent method. A first thermal transfer layer is formed by applying the compounded composition thereon by a known method such as a gravure roll method, a kiss roll method, or a tire bar method, and then the solvent is evaporated to form a second thermal transfer layer. obtain.

[Function] - The fine diatomaceous earth powder contained in the second transfer layer of the thermal transfer recording medium of the present invention has the following function.

Incorporating fine diatomaceous earth powder into the second thermal transfer layer 9 = This means that the surface of the base material and the second
The purpose is to improve storage stability by minimizing contact between the surface of the thermoplastic resin of the thermal transfer layer and the surface of the thermoplastic resin. For this purpose, the diatomaceous earth fine powder is partially exposed on the surface of the second thermal transfer layer. Further, the fine soil powder is strongly fixed inside the second thermal transfer layer so that it will not fall off when it rubs against the back surface of the base material or when it travels within the cassette.

On the other hand, as is clear from its origin, diatomaceous earth is a particle that has a wide variety of complex particle shapes and has a large number of pores inside. By pulverizing and/or classifying this powder and using a fine powder with an average particle size in the range of 0.5 to 10 μm, it is exposed in an appropriate state from the surface of the second thermal transfer layer and transferred to the back surface of the base material and the second thermal transfer layer. Direct contact with the thermoplastic resin surface of the layer is prevented, and the resin enters the pores, creating a large anchoring effect.

Furthermore, if the surface of the second thermal transfer layer is formed with the above-mentioned diatomaceous earth fine powder exposed, the surface will inevitably become rough and the coefficient of friction will increase. In particular, since the running of thermal transfer recording media for serial printers is caused by the difference in the coefficient of friction between the back surface of the base material and the back surface of the substrate, a large coefficient of friction is desirable, and it is desirable to have a high coefficient of friction, such as stick resistance and meandering resistance around the head. will also be improved.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by these Examples.

Example 1 Preparation of hot melt ink.

A hot-melt ink was prepared by sufficiently kneading 15% by weight of ethylene-vinyl acetate copolymer resin, 20% by weight of carbon black, 20% by weight of carnauba wax, and 45% by weight of paraffin wax using a heated Miki roll for ink. .

Preparation of formulated compositions.

50 parts by weight of polyvinyl butyral, 25 parts by weight of ketone resin as a softening point regulator, and 15 parts by weight of diatomaceous earth fine powder with an average particle size of 3 μm were added to ethyl acetate and thoroughly stirred to obtain a concentration of 10% by weight. A blended composition was prepared as an ethyl acetate solution for coating.

Preparation of heat-sensitive transfer recording medium: The heat-melt ink described in "2" was applied with a pot-melt gravure roll onto the surface of a 40 μm thick polyester film, the back surface of which was provided with a heat-resistant protective layer made of urethane-modified resin. A thermal transfer layer was formed. Next, the above-mentioned blended composition is applied onto the thermal transfer layer using a wire bar and dried to form a second thermal transfer layer having a thickness of l lt m to obtain the thermal transfer recording medium of the present invention. Ta.

Comparative Example] A thermal transfer recording medium was obtained in the same manner as in Example 1, except that the diatomaceous greige powder in the composition of the second thermal transfer layer was omitted.

Comparative Example 2 In the composition of the second thermal transfer layer, the diatomaceous greige powder was replaced with fine talc powder, which had the same average particle size of 3 μm and was non-porous and uniform in shape and scale. A thermal transfer recording medium was obtained in the same manner as in Example.

Next, the thermal transfer recording medium obtained by the above operation was wound up into a roll and stored at 60'C-2 for 4 hours, after which the degree of migration of the components of the second thermal transfer layer to the heat-resistant protective layer side was observed using a microscope. , Measurement of the coefficient of friction on the surface of the second thermal transfer layer (JIS
A printing test was conducted on transfer paper with a Beck smoothness of 50 seconds using a commercially available thermal transfer printer based on the P-81.47 paper friction test method (Uni word processor paper manufactured by Mitsubishi Pencil ■). The results are shown in the table below.

〔Effect of the invention〕

As is clear from the test results of Examples and Comparative Examples, the thermal transfer recording medium of the present invention is more effective in protecting the back side of the base material and heat-resistant components of the thermal transfer layer during high-temperature and long-term storage than conventional thermal transfer recording media. This is a heat-sensitive transfer recording medium with an excellent laminated structure that prevents transfer to layers, greatly improves the clarity of transfer to transfer paper with poor smoothness, and greatly improves the background stains on transfer paper.

Claims (1)

[Claims] In a thermal transfer recording medium having a laminated structure in which a first thermal transfer layer, which is a colored layer, is provided on a base material, and a second thermal transfer layer containing a thermoplastic resin as a main component is further provided thereon, the second thermal transfer layer is A heat-sensitive transfer recording medium characterized in that it is coated with a blended composition containing fine soil powder.