JPH0632071A - Thermal transfer material - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer material provided with a resin-cured film superior in heat resistance as a heatresistant protective layer on the back surface of a base film. CONSTITUTION:In a thermal transfer material provided with a thermal transfer ink layer on a base film, a cured film consisting of a polycarbodiimide compound having two or more carbodiimide groups in a molecule and a resin having carboxyl group is provided on the back surface of the base film. Therefore, in producing a heat-resistant protective layer, an inhibition of curing caused by a slight amount of water content existing in a system does not occur. Furthermore, the obtained thermal transfer material has no possibility of an occurrence of a trouble caused by a sticking phenomenon during recording, the adhesion of foreign particles to a thermal head, and the wear and damage of the thermal head, but has a shelf stability under high-temperature and -humidity conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive transfer material which is provided with a heat-resistant protective layer to prevent the base film from being thermally fused or damaged during recording.

[0002]

2. Description of the Related Art In recent years, with the development of office automation, a thermal transfer recording system has been introduced into various terminal devices such as facsimiles and printers. In this recording method, a heat-sensitive transfer material coated with heat-meltable ink or heat-sublimable ink is superposed on a recording paper such as plain paper, and the ink is transferred from the heat-sensitive transfer material to the recording paper by heating the thermal head. Is recorded. In the recording method using a thermal head, the heat generated from the thermal head transfers the ink to recording paper by melting or sublimating the thermal transfer ink through the base film, so the ink layer melts but is a plastic film. The film must not melt. However, if the heat generation amount of the thermal head is increased or the platen roll pressure is increased in order to increase the recording speed or record on a recording paper having a rough surface, the amount of heat and pressure applied to the base film is significantly increased. As a result, the size of the base film becomes large, and the base film is melted to cause heat fusion or damage. As a result, not only normal recording cannot be performed, but also the thermal head may be damaged. Generally, such a phenomenon is called a stick phenomenon.

In order to improve the stick phenomenon, some attempts have been proposed in the past to provide a protective layer having excellent lubricity and heat resistance on the back surface of the base film. As a method for providing the back surface of the base film with slipperiness, see JP-A-59-14869
A method of coating or impregnating the back surface of a base film with a wax or a liquid or paste-like substance at room temperature as disclosed in JP-A-7, and colloidal silica or colloidal as disclosed in JP-A-60-15193. A method using inorganic fine particles such as alumina is known, but it is not satisfactory. If a lubricant (wax or oil) is attached to the thermal head during recording, or if the thermal transfer material is stored under high temperature and high humidity, The lubricant (wax or oil) migrates to the ink layer, which causes problems such as normal recording not being possible.In addition, the inorganic fine particles are extremely hard and may cause wear or damage to the thermal head. There was a chance Further, it has been conventionally known to use a polyisocyanate compound having two or more isocyanate groups in the molecule in order to carry out crosslinking and curing for the purpose of improving the heat resistance of the resin, but the isocyanate group reacts with the hydroxyl group. In addition to the reaction with the desired resin, it is also consumed by a trace amount of water contained in the coating liquid, and further by the humidity in the air, so it was necessary to add it in excess of the required amount.

[0004]

DISCLOSURE OF THE INVENTION As a result of earnest studies in view of the above problems, the present inventor has found that a heat-sensitive transfer material provided with a cured film of a polycarbodiimide compound and a resin having a carboxyl group is a base film during recording. The present invention has been made, and it has been found that it does not cause a trouble of being damaged, does not cause foreign matter to adhere to the thermal head even during long-term recording, and can withstand storage under high temperature and high humidity.

[0005]

That is, the present invention provides a thermal transfer material having a thermal transfer ink layer on a base film, wherein a polycarbodiimide compound having two or more carbodiimide groups in the molecule is provided on the back surface of the base film. ,
Provided is a heat-sensitive transfer material provided with a cured coating with a resin having a carboxyl group. In the present invention, the reaction between a carboxyl group and a carbodiimide group is utilized, and crosslinking cure proceeds without being impaired by trace amounts of moisture in the components of the resin cured film and moisture in the air. No agent needed. Further, since the carbodiimide group does not react with water, the coating liquid can be used as an aqueous emulsion.

As the polycarbodiimide compound in the present invention, a known method described in JP-A-59-187029, for example, a mono-, di-, or triisocyanate compound in a non-reactive solvent, a suitable catalyst such as 3 Heating in the presence of -methyl-1-phenyl-2-phosphorate-1-oxide,
Those obtained by a method of carbodiimidizing an isocyanate group by a condensation reaction involving decarbonization can be used.

Diisocyanate is usually used as an isocyanate compound as a raw material for synthesizing a polycarbodiimide compound, for example, aromatic diisocyanate, aliphatic diisocyanate, alicyclic diisocyanate, or a mixture thereof, such as 1,5- Naphthylene diisocyanate, 4,4-diphenylmethane diisocyanate, 4,4-diphenyldimethylmethane diisocyanate,
4,4-dibenzylisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2 , 4-Trimethylhexamethylene diisocyanate, lysine diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate, Examples thereof include m-tetramethylxylylene diisocyanate and dimeryl diisocyanate. Further, a monoisocyanate compound such as phenyl isocyanate or butyl isocyanate may be used in order to adjust the concentration of the carbodiimide group in the molecule.

The resin having a carboxyl group which is crosslinked and cured by a polycarbodiimide compound is not particularly limited as long as it has a carboxyl group in the main chain or side chain.
Examples of such a resin include a polymer obtained by radically polymerizing a monomer having a carboxyl group and a polymerizable double bond in the molecule alone or a monomer having another polymerizable double bond in the molecule, or two or more carboxyl groups. Among the polymers obtained by polycondensation or polyaddition of a polycarboxylic acid having with a compound having two or more reactive functional groups which carry out an addition reaction or a condensation reaction with a carboxyl group, a polymer having an unreacted carboxyl group, and further other There are polymers introduced by modifying the carboxyl group into the polymer, for example, acrylic resin, polyester resin,
Polyamide resin, maleic acid resin, fumaric acid resin,
Examples thereof include polyimide resin, alkyd resin, polycarbonate resin, carboxymethyl cellulose, cellulose acetate phthalate, and various carboxyl-modified polymers.

The cured resin film of the present invention is obtained by applying a coating solution containing the above-mentioned resin having a carboxyl group and a polycarbodiimide compound on a base film by a conventionally known method, drying it, and then heating it at room temperature or if necessary. It is obtained by proceeding the curing reaction. The thickness of the heat resistant protective layer is usually 0.01 to several μ, preferably 0.1.
Is ~ 5μ

As the base film of the present invention, conventionally known ones can be used, for example, polyester film (polyethylene terephthalate, polyethylene naphthalate etc.), polyamide film (nylon etc.), polyolefin film (polypropylene, polyethylene etc.), A plastic film such as a cellulose film (cellulose triacetate or the like) or a polycarbonate film can be used. Of these, polyester films are preferable because they are excellent in heat resistance, mechanical strength, dimensional stability, and the like. The thinner the base film, the better the thermal conductivity, but the strength and ease of handling during coating make it 3μ to 50μ.
μ is preferred.

Conventionally known ink can be used as it is for the thermal transfer ink layer of the present invention. 1 of such ink
Examples include paraffin wax, carnauba wax,
Examples of the ink include waxes such as wood wax and beeswax as binders, and colorants such as dyes and pigments. A thermal transfer ink layer can be formed by applying a conventionally known coating method. it can.

[0012]

The present invention will be described in detail in the following examples. In addition, "part" in an Example points out a "weight part." Example 1 A 6 μm polyethylene terephthalate film (base film) was coated with a coating liquid A having the following composition using a bar coater so that the dry film thickness would be 0.5 μm, and warm air from a dryer was sufficient. Dried. Next, the other surface of the base film was coated with an ink containing paraffin wax as a main component and colored with carbon black while being heated and melted using a bar coater to obtain a heat-sensitive transfer material. The thickness of the ink layer was 3.5μ. Coating liquid A Styrene-acrylic acid copolymer resin (John Cryl 780, manufactured by Johnson Polymer Co., Ltd.) 10 parts Polycarbodiimide compound (main material: hexamethylene diisocyanate, polymerization degree 9) 5 parts Methyl ethyl ketone 45 parts Toluene 40 parts

Example 2 A heat-sensitive transfer material was obtained in exactly the same manner as in Example 1 except that the coating liquid A was changed to the coating liquid B having the following composition. Coating liquid B Acrylic resin (Dianal BR87 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts Polycarbodiimide compound (main material: hexamethylene diisocyanate, degree of polymerization 9) 5 parts Methyl ethyl ketone 45 parts Toluene 40 parts

[Example 3] A thermal transfer material was obtained in the same manner as in Example 1 except that the coating liquid A was changed to the coating liquid C having the following composition. Coating liquid C Polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) 10 parts Polycarbodiimide compound (main material: hexamethylene diisocyanate, degree of polymerization 9) 5 parts Methyl ethyl ketone 45 parts Toluene 40 parts

Comparative Example 1 A heat-sensitive transfer material was obtained in exactly the same manner as in Example 1 except that the coating liquid A was changed to the coating liquid D having the following composition. Coating liquid D Nitrocellulose (Celnova BTH1 / 2, manufactured by Asahi Kasei Co., Ltd.) 8 parts Polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) 5 parts Silicone oil (KP366, manufactured by Shin-Etsu Chemical Co., Ltd.) 2 parts Methyl ethyl ketone 50 parts Methyl isobutyl ketone 20 parts Cyclohexanone 15 parts

Comparative Example 2 A heat-sensitive transfer material was obtained in exactly the same manner as in Example 1 except that the coating liquid A was changed to the coating liquid E having the following composition. Coating liquid E Styrene-acrylic acid copolymer resin (John Cryl 780, manufactured by Johnson Polymer Co., Ltd.) 15 parts Methyl ethyl ketone 40 parts Toluene 45 parts

Comparative Example 3 A heat-sensitive transfer material was obtained in the same manner as in Example 1 without providing the heat resistant protective layer.

[Evaluation of Examples] A printing test was carried out with a thermal head using the heat-sensitive transfer materials of Examples 1 to 3 and Comparative Examples 1 to 3. Printing test with constant energy 5
Five cycles were performed with one cycle consisting of continuous for 5 minutes and rest for 5 minutes. The energy level of printing changes from 1.0mJ / dot to 3.0mJ / dot by changing the voltage and pulse width applied to the thermal head.
The energy was changed up to dot and evaluated. A film having a print resistance of 1.5 mJ / dot or more without causing the film to melt was regarded as having good stick resistance. In addition, after the printing test, the surface of the thermal head was observed to check whether the heat-resistant protective layer had scratches or dust. In the transfer test of the components of the heat-resistant protective layer to the ink layer side, two heat-sensitive transfer materials of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared, and a pair of heat-sensitive transfer materials were used as heat-resistant protective layers. And the ink layer were in contact with each other, and the layers were pressed with a pressure of 1 kg / cmcm ² . After aged at 40 ° C for 48 hours, a thermal transfer material with an ink layer in contact with the heat-resistant protective layer was printed with a thermal head at an energy of 1.0 mJ / dot, and the print quality was deteriorated compared to before storage. I checked whether it would be possible. The results are summarized in Table 1.

[0019]

[Table 1]

The thermal transfer materials of Examples 1 to 3 were 1.0 mJ / dot.
Even when the energy was changed from 1 to 3.0 mJ / dot, the printing was not disturbed and the stick phenomenon did not occur. Needless to say, the base film was not melted and damaged, and neither scratch nor dust adhered to the thermal head was observed. Also,
No transfer of the constituents of the heat-resistant protective layer to the ink layer was observed, and there was no effect on print quality. On the other hand, Comparative Example 1
No sticking phenomenon was observed in the same manner as in Examples 1 to 3, but the transfer of the silicon component of the heat resistant protective layer to the ink layer was severe and the print quality was remarkably deteriorated.
Further, in Comparative Example 2, since the resin was not cured, the stick phenomenon had already occurred from the energy of 1.3 mJ / dot due to insufficient heat resistance, and at 1.5 mJ / dot, the base film was damaged due to melting. . In Comparative Example 3 as well, a heat-resistant protective layer was not provided, so 1.3 mJ /
The stick phenomenon occurred from the dot, and at 1.5 mJ / dot, the base film was damaged due to melting.

[0021]

According to the present invention, no troubles due to the stick phenomenon occur during recording, no foreign matter is attached to the thermal head, abrasion or damage is caused even during long-term recording, and it can be stored under high temperature and high humidity. It was possible to obtain a heat-sensitive transfer material that can withstand. Further, if the thermal transfer material of the present invention is used,
The base film does not melt even if the amount of heat applied to the thermal head is increased to increase the amount of heat generation, and clear printing can be obtained without the stick phenomenon, so high-speed printing or surface printing is possible. Printing on rough recording paper is now possible.

Claims (1)

[Claims] 1. A heat-sensitive transfer material having a thermal transfer ink layer formed on a base film, wherein a cured film of a polycarbodiimide compound having two or more carbodiimide groups in the molecule on the back surface of the base film and a resin having a carboxyl group. A heat-sensitive transfer material provided with.