JPS61189994A - Thermal transfer paper - Google Patents

Abstract

PURPOSE:To enhance the close adhesiveness with a film and to eliminate abnormal transfer, by using a polyamide resin with a specific MW obtained by the reaction of dimer acid and di- or polyamine as the binder of an ink layer. CONSTITUTION:The binder used in a thermal recording medium, wherein an ink layer containing a sublimable dye is provided on a base material, is a polymide resin with MW of 40,000-80,000 obtained by reacting dimer acid and di- or polyamine and especially well in the close adhesiveness with a polymer film. The softening point of said resin is 100 deg.C or more, pref., 110-190 deg.C. If the softening point is 110 deg.C or less, said resin is melted or becomes markedly viscous by heat at the time of transfer and is transferred to image receiving paper to make image quality inferior. The polyamide resin is extremely low in water absorbability and the greater part thereof is 2% or less but the resin, of which water absorbability is as low as possible, is pref. used.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a method for printing still images of various types of images, such as images captured by a video camera, television, and personal computer images, as hard copies. It is a thermal transfer paper, and particularly relates to a thermal transfer paper for obtaining a color copy by sublimation transfer of a sublimation dye to an image receiving paper.

° [Background of the Invention] Conventionally, there are electrophotographic methods, inkjet methods, thermal transfer methods, etc. as recording methods for obtaining color images, but the thermal transfer method is preferred because it is noiseless and the device is easy to maintain. is proposed. This thermal transfer method is
Consisting of solidified color ink paper and image receiving paper,
This is a recording method in which an image is formed by heat-melting transfer or sublimation transfer of ink onto image-receiving paper using thermal energy controlled by electrical signals from a laser or a thermal head. Thermal transfer recording methods of Koki-1-1 include a thermal melt transfer type and a sublimation transfer type using a sublimation dye. The hot-melt transfer type uses ink paper with pigments or dyes bound with hot-melt wax, and the thermal energy of the thermal head transfers the pigments or dyes along with the melted wax to the receiving paper, so it is possible to achieve the required halftones for image quality. The disadvantages are that it is difficult to obtain and that a good hue cannot be obtained because of the transferred wax. In addition, the sublimation and migration type using sublimation dyes is an application of conventional sublimation transfer printing technology, and uses transfer paper with a binder binding disperse dyes, which are generally relatively easy to sublimate, to the thermal head. A color image is obtained by sublimating and transferring the sublimation dye to the receiver paper using heat energy. At this time, the sublimation dye sublimates in response to the thermal energy of the thermal head, so there is an advantage that halftones can be easily obtained. What is important in this sublimation dye type is the ink composition, and the most important thing to consider when adjusting the ink is the selection of an appropriate binder. It is undesirable that the resin melts or becomes extremely viscous due to heat during transfer, and the resin transfers to the image receiving paper, which is the transfer target, resulting in poor image quality. Japanese Patent Publication No. 59-149
94.59-71898 etc. uses polyamide resin as a binder. These are commonly referred to as nylons and provide very strong membranes. However, it has drawbacks such as poor water absorption and difficulty in dissolving in solvents. Furthermore, in order to make the thermal energy of the thermal head more efficient, the base material of condenser paper was changed to thin paper (28 μm), and a polymer film (6) was used.
A thin base material of micrometers or less is used, and adhesion between the film and the ink layer becomes a problem. Nylon does not have very good adhesion. In other words, if the adhesion with the fill is poor, the entire ink layer will be transferred to the image receiving paper side by the heat of the thermal head, resulting in an undesirable phenomenon of abnormal transfer.

As a result of extensive research into the present invention to meet the above-mentioned requirements, it has been possible to obtain a thermal transfer paper with good adhesion, no abnormal transfer, and low water absorption that fully satisfies the requirements.

[Purpose of the invention]

An object of the present invention is to provide a thermal transfer paper that has no adhesion to a film and no abnormal transfer in an ink layer consisting of a sublimation dye and a binder.

[Summary of the invention]

According to the present invention, the base material of the ink layer used can be condenser paper, glassine paper, thin cellulose paper, or other polymeric films. These are known. The thickness of the base material tends to be as thin as possible in order to efficiently conduct heat from the thermal head, and a polymer film such as polyethylene terephthalate (generally PET) with a thickness of 6 μm or less is mainly used.

However, when these films are used, a slippery heat-resistant layer is provided on the surface that contacts the head in order to ensure smooth running of the thermal head. What is the sublimation dye used in this invention?
It is a sublimation dye with a relatively small asci of about 200 to 400, and is contained in large amounts in conventionally known sublimation dyes and disperse dyes.
It vaporizes from solid or liquid at a temperature of about 100 to 200°C (at normal pressure) and is adsorbed to synthetic resin materials such as nylon, polyester, and acetate, and its chemical structure includes anthraquinone, azo, The main dyes are styryl dyes, quinophthalone dyes, and nitrodiphenylamine dyes. The binder used in the present invention is obtained from the reaction of dimer acid and di- or polythymine (molecular weight 4
000 to 8000), and has particularly good adhesion to polymeric films. Softening point is 100
'C or higher, more preferably 110°C to 190°C. If the softening point is below 110° C., the resin will melt or become extremely viscous due to the heat during transfer, and the resin will be transferred to the image receiving paper, resulting in poor image quality. In addition, this polyamide resin has a very low water absorption rate, most of which is less than 2%, and as a binder for thermal transfer paper, it is preferable to use one with a water absorption rate as low as possible.

As the solvent used in the present invention, various alcohol-based, ester-based, and ketone-based solvents can be used alone or in a mixture. In particular, mixed solvents are preferred for the polyamide resin used in the present invention.

[Embodiments of the invention]

The basic ingredients of the composition of the present invention are as described above,
In addition, various conventionally known additives and fillers can be used as necessary.

The composition of the present invention is manufactured by blending the above-mentioned components and carrying out a normal dispersion treatment.
The liquid ink composition of the present invention obtained as described above preferably has an amount of 0 to 97% by weight, using known coating means such as a blade coater, gravure coater, roll coater, curtain coater, bar coater, and air knife coater. It is coated to a thickness of 5 μm or less. The applied ink layer is heated and dried to obtain thermal transfer paper. The obtained thermal transfer paper is placed on an image-receiving paper, and heat energy is applied by a thermal head to sublimate the sublimation dye, thereby forming an image on the image-receiving paper. At this time, the binder of the ink layer cross-linked with polyisocyanate by the heating of the thermal head does not become excessively soft or sticky, and there is no transfer of the binder to the image receiving paper, and a clear image can be obtained. If an alcohol-based or aromatic-based mixed solution is used, the binder in the ink layer will not fuse due to air drying immediately after application, and the actual heat drying process can be performed at 50°C or less for a few seconds, and the sublimation dye There is no volatilization due to drying, which is preferable in terms of manufacturing thermal transfer paper.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 Kayaset Yellow G (Nippon Kayaku) 1 part Persamide 725 45 parts (softening point 125°C to 135°C: manufactured by Henkel Hakusui Co., Ltd.) Isopropyl alcohol/toluene = 3/1.・・・・・・
・20 parts hexane 25 parts were dispersed in a ball mill to obtain a sublimation dye composition ink liquid. This ink liquid was applied with a gravure coater to a polyester film (PET 6 μm) with a slippery heat-resistant layer on the back side.
The thermal transfer paper of the present invention was obtained by drying treatment. Film thickness is 0.8
It is μm. Using this thermal transfer paper, use art paper or synthetic paper coated with polyester etc. as the image receiving paper.

The thermal transfer paper and the image receiving paper were superimposed, and the thermal head recording conditions were 6 dots/I in both main scanning and sub-scanning, and 0 applied power.
．． The gradation was observed by adding a pulse width of 3 to 0.4 W/dot. As a result, there was no abnormal transfer such as melting of the ink layer due to heat or transfer of the binder to the image-receiving paper, and a good color tone with good gradation was obtained.

The color saturation density at this time was 0.9.

Example 2 Kayaset Red-〇 (Nippon Kayaku) 16.4 parts Persamide-865 10 parts (softening point 168°C to 184°C: manufactured by Henkel Hakusui Co., Ltd.) Isopropyl alcohol/toluene: 3 /1...
・30 parts Hexane 43.6 parts Example 3 Kayaset Blue 136 (Nippon Kayaku) 10 parts Persamide-725 48 parts Isopropyl alcohol/toluene: 371
・18 parts Hexane 24 parts Example 4 Rura Pick Blue-660 (manufactured by BASF)
・13.4 parts Persamide-711...8.0 parts (softening point 1
05℃~110℃: Henkel Hakusui Co., Ltd.) Isopropyl alcohol/toluene: 371...
・32.1 parts Hexane 46.5 parts Example 5 Rura Quick Red-430 (manufactured by CBASF)
...10 parts Persamide-93O8...20 parts (softening point 10
5°C to 110°C: Henkel Hakusui Co., Ltd. 11) Isopropyl alcohol/toluene = 3/1...
- 30 parts hexane - Old... 40 parts A thermal transfer paper of the present invention was obtained using the compositions of Examples 2 to 5 and the same method as in Example 1. The results are shown in Table 1.

Comparative Example 1 Rura Quick Red-430...10 parts Persamide-871...20 parts (softening point 80°C - 10
0℃: Henkel Hakusui Co., Ltd.) Isopropyl alcohol/toluene = 3/1...
・30 parts hexane 40 parts As a comparative example, Versamide 8 with a softening point of 86°C to 100°C
A thermal transfer paper was obtained in the same manner as in Example 1 using No. 71.

The results are shown in Table 1.

Table 1 [Effects of the Invention] According to the present invention, the polyamide resin obtained by polymerizing dimer acid and di- or polyamine has good adhesion to polymer films, and thermal transfer paper without abnormal transfer can be obtained. It will be done. In addition, sharp color copies similar to color still images were obtained.

Leprosy patent attorney Katsuo Ogawa

Claims (1)

[Scope of Claims] 1. In a thermal recording medium comprising an ink layer containing a sublimation dye provided on a base material, the binder of the ink layer has a molecular weight of 4,000 obtained by the reaction of a dimer acid and a di- or polyamine. A thermal transfer paper characterized in that it is a polyamide resin of ~8,000. 2. The thermal transfer paper according to claim 1, wherein the binder has a softening point of 100°C to 190°C.