JPH04163096A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To improve running properties at the time of high speed transfer and to prevent a sticking phenomenon or the blur of printing by providing a colorant layer to the upper surface of a base film and providing a heat- resistant protective film consisting of a heat-resistant resin and a boron nitride powder to the under surface thereof. CONSTITUTION:Ink is applied to the upper surface of a base film and dried in an oven to form a colorant layer. Next, a resin composition containing a boron nitride powder is applied to the under surface of the base film and dried in the oven to form a heat-resistant protective film to prepare a thermal transfer recording medium. By this method, the heat conductivity of the thermal transfer recording medium is markedly enhanced in addition to the heat deformation resistance and slip properties thereof and, even when transfer recording speed is high speed of 100-150 characters per one sec, sticking or the blur of printing can be effectively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a thermal transfer recording medium. More specifically, the present invention relates to a thermal transfer recording medium used to transfer an image or the like to a transfer object using a thermal head, and which has improved running properties during high-speed transfer.

[Conventional technology]

In recent years, as an image recording method for word processors, video printers, etc., a thermal head is used to heat a thermal transfer recording medium.
2. Description of the Related Art A thermal transfer recording method for recording an image on a transfer target such as recording paper has become widespread.

Various types of thermal transfer recording media have been developed in the past, but generally a coloring material layer made of a coloring material such as a dye and a solid oil or fat is formed on the top surface of a base film made of a PET film or the like. However, a heat-resistant protective film made of a heat-resistant resin and a lubricant is formed on the lower surface of the base film.

When using such a thermal transfer recording medium, the object to be transferred, such as recording paper, is placed on the coloring layer side of the thermal transfer recording medium, and the printer's thermal head is brought into contact with the protective film of the thermal transfer recording medium to transfer the printed information. In response, the thermal head is heated to locally heat and melt the coloring material layer, and the molten coloring material is transferred to the transfer target.

In this case, the protective film has a function of preventing the so-called sticking phenomenon in which the molten base film fuses to the thermal head. In other words, heating by the thermal head melts not only the color material layer but also a portion of the base film, which causes a sticking phenomenon in which the molten base film fuses to the thermal head, and also makes printing easier to fade. Since the film reduces the thermal deformability of the thermal transfer recording medium and improves the slipperiness, the sticking phenomenon is prevented.

[Problem to be solved by the invention]

However, with the recent demand for faster recording, the heating conditions for thermal heads have become higher and shorter, and the surface temperature has been raised to a temperature that far exceeds the melting point of the base film. For this reason, it has become difficult to effectively prevent the sticking phenomenon with conventional protective films, and printing has also become blurred.

Therefore, the transfer recording speed is usually 75 per second.
The printing speed of characters (75 cps) was the limit, and it was impossible to achieve good transfer at a higher speed. For this reason, there has been a problem in that it cannot sufficiently meet the recent demands for high-speed printing.

This invention is an attempt to solve the above-mentioned problems in the conventional technology, and it provides a heat-resistant protective film that can withstand even high-speed printing of 100 to 150 characters per second, and improves performance during high-speed transfer. The purpose of the present invention is to provide a thermal transfer recording medium with improved running properties.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a thermal transfer recording medium in which a coloring material layer is provided on the upper surface of a base film and a protective film made of a heat-resistant resin is provided on the lower surface, wherein the protective film contains boron nitride powder. A thermal transfer recording medium is provided.

In order to make a thermal transfer recording medium compatible with high-speed transfer, the present invention proposes the following characteristics to be imparted to the protective film of the thermal transfer recording medium:
Based on the knowledge that it is extremely effective to improve thermal conductivity in addition to the conventional improvements in heat deformation resistance and slipperiness, and that it is suitable to add boron nitride powder for this purpose. ing.

The boron nitride powder used in the protective film of the thermal transfer recording medium of the present invention may be hexagonal or cubic, but hexagonal is more preferably used.

Further, the shape of the boron nitride powder is not particularly limited, but for example, a scaly shape can be used.

The content of boron nitride powder in the protective film is preferably 5 to 60% by weight. If the amount is less than 5% by weight, the effect of preventing the sticking phenomenon will not be sufficiently exhibited, while if it is more than 60% by weight, it will be difficult to form a film and the film strength may be insufficient.

In the protective film, various heat-resistant resins conventionally used in protective films can be used as the resin serving as a binder for such boron nitride powder. For example, urethane resin, silicone resin, epoxy resin, melamine resin, phenol resin, fluororesin, polyimide resin,
Nitrocellulose resin, acetylcellulose resin, styrene-butadiene copolymer, alkyd resin, acrylic resin, urethane-modified silicone resin, polyvinyl butyral resin, polyethylene glycol, polypropylene glycol, fatty acid ester of polyvinyl alcohol, styrene-acrylic copolymer, Examples include vinyl urethane resins, aziridine compounds, polyolefin resins, acrylic silicone resins, and resins made of two or more of these.

Further, for such heat-resistant resins, curing agents such as isocyanates, carboxylic acids, acid anhydrides, and alcohols can be used.

In addition, the protective film of the present invention may contain various additives including lubricants such as graphite and silica.

The protective film can be formed on the lower surface of the base film by a conventional method. For example, the above-mentioned heat-resistant resin composition containing boron nitride powder may be applied to a base film and heated, or a film of heat-resistant resin containing boron nitride powder may be laminated on the base film. You may.

The thickness of such a protective film is generally about 0.5~
The thickness is preferably 5 μm.

In the thermal transfer recording medium of the present invention, the base film and the coloring material layer can be constructed in the same manner as in the conventional example.

That is, as the base film, plastic films such as polyester film, polystyrene film, polysulfone film, polyimide film, polyvinyl alcohol film, aromatic polyamide film, and aramid film, or thin paper such as cellophane and condenser paper can be used. can.

Further, the coloring material layer may be formed from an ink containing a binder and a coloring material such as various dyes such as sublimable dyes and heat-melt migration dyes, or carbon black or other pigments. For example, the dyes used include diarylmethane, triarylmethane,
Commonly used substances include thiazole series, methine series, azomethane series, xanthine series, acridine series, thiazine series, azine series, acridine series, azo series, spirodipyran series, isodorinospiropyran series, fluoran series, rhodamine lactam series, and anthraquinone series. Dyes can be widely used.

Further, as the binder, vinyl acetal resin, polyester resin, cellulose resin, acrylic resin, polyamide resin, etc. can be used.

In addition, surfactants, softeners, additives, etc. can be added to the ink as appropriate.

The method for forming the coloring material layer on the upper surface of the base film can also be carried out by a conventional method. For example, ink may be applied to the surface of the base film using a bar coater or the like and dried.

The thermal transfer recording medium of the present invention can have various layer configurations, as long as a coloring material layer is provided on the upper surface of the base film, and a heat-resistant protective film made of heat-resistant resin and boron nitride powder is provided on the lower surface of the base film. It can be done. For example, a transfer promotion layer may be provided on the coloring material layer to improve the reproducibility of highlight portions at low applied voltages.

[Effect]

According to the thermal transfer recording medium of the present invention, since the heat-resistant protective film is made of a heat-resistant resin containing boron nitride, in addition to heat deformation resistance and slipperiness, thermal conductivity is significantly improved, and the transfer recording speed is 1 second. Even at high speeds of 10 to 150 characters, it is possible to effectively prevent sticking and blurred printing.

〔Example〕 Hereinafter, the present invention will be specifically explained with reference to Examples.

Example An ink having the composition shown below was applied to the upper surface of a PET film having a thickness of 4.5 μm, and was dried in an oven at 60° C. to form a color material layer having a thickness of 4 μm.

Ink composition: Carvana wax: 20 parts by weight Paraffin wax: 30 parts by weight Vaseline: 10 parts by weight Carbon black: 20 parts by weight Next, a heat-resistant protective film-forming resin composition having the following composition was applied to the lower surface of the PET film. The film was dried in an oven at 60° C. to form a heat-resistant protective film with a thickness of 1 μm, thereby producing a thermal transfer recording medium of the present invention.

Heat-resistant protective film composition Nitrocellulose 10 parts by weight Sodium stearyl sulfonate 0.5 parts by weight Toluene 40 parts by weight Methyl ethyl ketone 30 parts by weight Boron nitride powder (H-BN, 111111 3 parts by weight) The obtained thermal transfer recording medium was coated with a width of 12.7 mm. 100C at a printing speed of 75 cpss using a serial printer.
When printing was performed at three levels of p8% and 150Cp8, no sticking phenomenon or fading of the print occurred at any printing speed.

Comparative Example A thermal transfer recording medium was manufactured in the same manner as in Example except that the heat-resistant protective film did not contain boron nitride powder, and the printing speed was 75 cps using a serial printer.

Printing was performed at three different speeds: 100 cps and 150 cps. As a result, the print speed is 100cps and 150cps.
In the case of cps, sticking phenomenon and blurred printing occurred.

〔Effect of the invention〕

According to the thermal transfer recording medium of the present invention, running performance during high-speed transfer is improved, and the transfer recording speed is 100 to 150 per second.
Even when printing characters at high speeds, it is possible to effectively prevent the sticking phenomenon and blurred printing.

Claims (1)

[Claims] 1. A thermal transfer recording medium in which a coloring material layer is provided on the upper surface of a base film and a protective film made of a heat-resistant resin is provided on the lower surface, characterized in that the protective film contains boron nitride powder. A thermal transfer recording medium. 2. The thermal transfer recording medium according to claim 1, wherein the protective film contains 5 to 60% by weight of boron nitride powder.