JPS62108086A - Thermal transfer ink film - Google Patents

Abstract

PURPOSE:To enable a sufficient developed color density to be obtained with a small quantity of heat, by incorporating a substance for accelerating the diffusion of a vapor of a dye in an ink layer of a thermal transfer film at a part nearer to a thermal head. CONSTITUTION:A compound represented chemical formula (I), wherein each of R1, R2, R3 an up to 6C straight-chain or branched alkyl, alkoxyl, hydrogen, hydroxyl, nitro, a halogen, phenyl, carboxyl, alkyloxycarbonyl, carbamoyl, cyano, isocyano, formyl, amino, acetonitrile, propionyl or phenacyl, is incorporated in an ink layer at least on the side of a base, in a thermal transfer ink film which comprises an ink layer comprising a binder and/or a dye on a base. The effect of the compound of formula (I) is the same irrespective of whether a single such compound is incorporated in the ink of the thermal transfer film or a plurality of such compounds are incorporated in the ink. A thermal transfer ink film obtained by applying an ink solution comprising the compound of the formula to the base, followed by drying, and then applying an ink solution not containing the compound of the formula thereto, followed by drying is markedly enhanced in transfer efficiency and developed color density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ink film for thermal transfer recording, and particularly to a thermal transfer ink film that can be efficiently transferred with a small amount of heat.

[Background of the invention]

Conventionally, a thermal transfer ink film was used, in which ink obtained by dispersing dye in a binder was applied onto a thin heat-resistant sheet such as paper, and heat was applied from the back side with a heat generating head to vaporize only the dye in the ink, resulting in good dyeability. - A method has been proposed in which a color image is formed by transferring dye onto an image-receiving paper whose surface is coated with a bright resin. This method does not require handling in the dark or under safe light as with silver halide photography, and the image forming process is quick and easy, making it suitable for a wide range of practical purposes.

The thermal transfer ink film used here increases the color density of the image, obtains clear images with high contrast, reduces the thermal energy applied to the printer's heat-generating head, reduces power consumption, and extends the life of the heat-generating head. There was a need to be able to efficiently transfer the dye onto the image receiving paper so that it could be used for a long time.

In other words, in such a color image forming method, the dye in the ink must be heated and vaporized in a short time using a heat-generating head heated to a high temperature of 200° C. or higher, and then diffused and dyed into the dyed layer on the image receiving paper. Must be. To achieve this, it is known that inorganic fine powders with good heat conductivity such as alumina and metal powders are mixed into the ink to improve the efficiency of heat transfer from the heating head to the dye and increase the vaporization rate of the dye. (Japanese Patent Application Laid-Open No. 59-79788, Japanese Patent Application Laid-open No. 59-67080)
, Japanese Patent Publication No. 59-162090).

However, in the above method, since the inorganic fine powder is mixed in an amount about 5 to 6 times the amount of dye, the dye content in the ink decreases, and the total amount of vaporized dye becomes insufficient. Moreover, these fine powders prevent the diffusion of dye vapor, making it impossible to obtain sufficient color density.On the other hand, if the amount of ink applied is increased to increase the color density, the ink film becomes thicker, and the heat transfer efficiency decreases. There was a drawback that sufficient color density could not be obtained unless the electric power applied to the heating head was increased due to the insufficient amount of heat supplied to the heating head.

[Purpose of the invention]

An object of the present invention is to provide a thermal transfer ink film with excellent transfer efficiency that can realize sufficient color density with a small amount of heat.

[Summary of the invention]

In order to efficiently transfer the dye in the thermal transfer ink film to the image receiving paper using a small amount of heat, it is necessary to improve not only the rate of heat transfer from the heat generating head to the dye, but also the rate of diffusion of the generated dye vapor.

The diffusion rate is proportional to the product of the dye vapor pressure and the diffusion coefficient in the binder or receiver paper dyed layer (eg.

- Naoji Iro, Basic Mechanical Engineering Complete Book 9. "Heat Transfer Engineering" 1967
(2013 Morikita Publishing) Therefore, it is best to choose materials with large values. However, when considering the storage stability of an unused thermal transfer ink film, practical restrictions are placed on the vapor pressure of the dye and the range of the diffusion coefficient of the binder or dyed layer. Therefore, it was thought that the objective could be achieved if the diffusion coefficient could be increased by some means only during the thermal transfer operation. Therefore, we considered including a substance in the ink that vaporizes during thermal transfer, acts on the binder of the thermal transfer film and the dyed layer of the image receiving paper, and promotes the diffusion of the dye vapor. It is generally known that the diffusion coefficient of polymeric materials such as binders and dyed layers changes significantly after reaching the glass transition temperature (for example, Shigeharu Onogi, "Polymer Materials Science", 1939).
(July 1980, Seibundo Shinkosha), we thought that if we lowered the glass transition temperature by using some kind of substance, the dye diffusion rate would increase and the transfer efficiency would improve even if the transfer temperature remained the same.

Furthermore, it was thought that if a substance that acts in this manner is mixed in advance in the ink layer of the thermal transfer film closer to the heating head, it will vaporize more efficiently and act more effectively on the binder and dyeing layer.

Therefore, we conducted experiments with various compounds and obtained the following results.

That is, in order to produce the above effect, the substance must at least vaporize and diffuse before the dye and act on the binder and dyed layer. For this purpose, the vapor pressure and diffusion coefficient must be greater than those of the dye during thermal transfer, and a substance with a molecular weight smaller than the dye is suitable as such. Moreover, among such substances, those having a small heat of vaporization are particularly preferable because they cause a slight drop in ink temperature during thermal transfer and do not reduce the amount of dye vapor generated.

(In the formula, R1, R2, Rs are straight chain or branched alkyl groups or alkoxy groups having 6 or less carbon atoms.

(Indicates hydrogen atom, hydroxyl group, nitro group, halogen atom, phenyl group, carboxy group, alkyloxycarbonyl group, carbamoyl group, cyano group, isocyano group, formyl group, amino group, acetonyl group, propionyl group, phenacyl group) The effects of these compounds shown in formula 1) are the same whether they are mixed alone into the ink of the thermal transfer film or when a plurality of compounds are mixed into the ink.

A thermal transfer ink film obtained by coating a substrate with an ink solution containing the compound represented by formula ([) and drying it, and then coating and drying an ink solution that does not contain the compound of formula (I) is an untreated ink film. The transfer efficiency is significantly improved compared to thermal transfer ink films, and when comparing the images on receiving paper obtained by setting these films in a thermal printer, it is found that the thermal transfer film containing the compound shown in formula (1) in the ink produces more color. 1 degree was significantly improved.

[Embodiments of the invention]

The present invention will be described below based on comparative examples and examples, but the present invention is not limited to these examples.

Also, what are the color density values in the comparative examples and examples? 1
There will be slight variations depending on the method used.

[Comparative example]

Ink coating liquid 0 with the following formulation on base film [6 μm thick polyethylene terephthalate (PET) film]
．． 5mQ using a bar coater to 10cm x 15cm
After coating, it was dried at room temperature, and 0.5 m of the coating solution (1) was again coated on a 10 cm x 15 cm area using a bar coater and dried at room temperature to prepare a thermal transfer ink film.

Composition Weight sublimable dye (BASF, M430) 2.0g polyamide (
Henkel Japan, Parsalon) 2.0 g Toluene 9.0 g Improper Tool 9.0 g [Example 1] 0.5 mA of ink coating liquid with the following formulation was applied onto a base film (6 μm thick PET film) using a bar coater. 0.5 mQ of the coating solution shown in Comparative Example was coated on a 10 cm x 15 cm layer using a bar coater, and dried at room temperature to prepare a thermal copying ink film.

Composition: Coating liquid shown in weight comparison example 5. Og [Example 2
] As in Example 1, an ink coating liquid of the following formulation was applied onto a base film (6 μm thick PET film) at 0 and 5 mQ.
was coated on an area of 10 cm x 15 cm using a bar coater and dried, and 0-5 m Q of the coating liquid shown in the comparative example was overlaid and dried to produce a thermal transfer ink film.

Composition Weight 5.0 g of the coating liquid shown in the comparative example [Example 3] The following ink was applied on a base film (6 μm thick PET film) in the same manner as in Example 1, and after drying at room temperature, the coating liquid of the comparative example was applied. A thermal transfer ink film was prepared by applying 0.5 mQ of ink in layers and drying at room temperature.

Composition: Coating liquid shown in weight comparison example 5. Og [Example 4] The following ink coating liquid 0, 5m-Q was coated on a base film (6 μm thick PET film) using a bar coater,
Apply 0.5 mQ of the coating liquid of the comparative example to the thing dried at room temperature,
A thermal transfer ink film was prepared by drying at room temperature.

Composition: Coating liquid shown in weight comparison example 5. Og [Example 5] On the base film (6 μm thick PET film), apply 0.5 mA of the following ink coating liquid using a bar coater and dry at room temperature. Apply 0.5 m Q of the coating liquid of the comparative example and dry at room temperature. A thermal transfer ink film was prepared.

Composition: Coating liquid shown in weight comparison example 5. Thermal transfer ink films prepared in Og comparative example and Examples 1 to 5 were used in a thermal printer (heating head resistance 210Ω, head applied voltage 70Ω).
0 V) and set the head energization time to 0 to 20 m.
s, and the input thermal energy was varied to print on receiver paper. Next, the reflected color density of this image-receiving paper was measured using a Macbeth color densitometer, and the color density characteristics shown in Table 1 were obtained.

It is clear from Table 1 that the thermal transfer ink films produced in Examples 1 to 5 all develop colors at higher densities than those of the comparative example, provided the time for which electricity is applied to the heating head is the same. That is, according to the present invention, the efficiency of dye transfer from the thermal transfer ink film to the image receiving paper is improved, and the color density is increased.

〔Effect of the invention〕

As is clear from the above, according to the present invention, if the thermal energy input to the thermal transfer film is the same, the color density of the image receiving paper will improve, and conversely, if the color density of the image receiving paper is the same, the thermal energy input to the thermal transfer film will be improved. An excellent effect is obtained in that it is possible to reduce thermal energy.

Claims (1)

[Scope of Claims] 1. In a thermal transfer ink film having an ink layer containing a binder and/or a dye provided on a base material, a compound represented by the following chemical formula (I) is contained at least on the side of the base material side of the ink layer. A thermal transfer ink film characterized by ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (However, in the formula, R_1, R_2, R_3 are straight chain or branched alkyl groups with 6 or less carbon atoms, alkoxy groups, hydrogen atoms, hydroxyl groups, nitro groups, halogen atoms, phenyl group, carboxy group, alkyloxycarbonyl group, carbamoyl group,
2. The compound represented by the chemical formula (I) is contained in a high concentration on the upper side of the substrate. The thermal transfer ink film according to claim 1, characterized in that: 3. Two or more ink layers containing the binder and dye are provided, and at least one of the ink layers on the side in contact with the base material contains a compound represented by the chemical formula (I). A thermal transfer ink film according to claim 1.