JPH0377796B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a thermal transfer recording medium capable of thermally transferring a dye to form a dye image on a recording sheet.
More specifically, images using metal chelated dyes that are stable against heat, light, etc., have high sharpness, and have multi-gradation properties can be printed onto plain paper-like images using a thermal transfer process using non-sublimable chelatable dyes. The present invention relates to a thermal transfer recording medium that can be obtained on a recording sheet. [Prior Art] Conventionally, methods have been known for recording images, etc. by coloring thermal paper using a thermal head composed of thick film resistors, thin film resistors, semiconductor resistors, etc., or a heat source such as a laser or a xenon lamp. Since these methods use thermal paper, there are problems with the stability of the image against heat and light, and there are also disadvantages of high manufacturing costs.Furthermore, for colorization, it is necessary to have multiple coloring layers, and two-color printing is required. The drawback was that there was a limit to the extent of this. As a thermal recording method that solves the above drawbacks, for example, a coloring material that is solid or semi-solid at room temperature is coated on a support such as paper or resin film, as described in Jikai Publication No. 15446/1983. The coloring material on the support is brought into contact with the recording sheet, and the coloring material on the support is heated and selectively transferred to the recording sheet using a heat source controlled according to image information. A thermal transfer method for recording is known. The thermal transfer process in this method uses a coloring material mixed with a dye in a solvent with a low melting point and small heat capacity, and a melt transfer type that thermally transfers the dye together with the solvent, and a melt transfer type that uses a sublimable dye as the coloring material and uses a dye alone. A sublimation transfer type that performs thermal transfer is known. Among these, the melt transfer type has the disadvantage that it is difficult to obtain gradation of the image because all of the coloring material is transferred when heat energy other than a certain amount is applied. On the other hand, in the sublimation transfer type, the dye is transferred depending on the amount of thermal energy applied, so it is a desirable method for obtaining gradation. However, with sublimation transfer type,
Since sublimable dyes are used to form images, there are problems with the fixation and storage stability of the images due to resublimation of the dyes.Especially when transferring to plain paper, the color density is low and the dyes regenerate over time. The drawback was that the color density decreased significantly due to sublimation. Therefore, the inventors of the present invention disclosed in Japanese Patent Application No. 57-217796 that they used a sublimable dye, which is advantageous in order to obtain multi-gradation image recording, and that it is stable against heat, light, etc. on plain paper, etc. We have proposed a thermal transfer recording method that can form a unique image, and a recording medium for use in the method (hereinafter, this proposal will be referred to as the "previously proposed technology"). Although the previously proposed technology is very superior in that it overcomes the drawbacks of the conventional technology, there is a problem with the shelf life of the thermal transfer recording medium because it uses a sublimable dye.
It has also been found that because a sublimable dye is used, the selection range of dyes is limited. In view of these points, the present invention conducted research on a thermal transfer recording medium that can obtain a dye image with multi-gradation using a dye having a non-sublimable chelating ability, and arrived at the present invention. [Object of the Invention] Therefore, the first object of the present invention is to provide a thermal transfer recording medium that is excellent in raw storage stability in terms of tonality. A second object of the present invention is to provide a thermal transfer recording medium capable of obtaining a multi-gradation dye image with high transfer density and excellent thermal stability and light fastness on a recording sheet such as plain paper. It's about doing. [Structure of the Invention] The recording medium of the present invention that achieves the first and second objects described above is provided on a support by sublimation or substantially no photosensitive component at a temperature of 300°C or less. A coloring material containing a non-sublimable pigment that does not vaporize, exhibits migration properties by melting at a melting point of 300°C or lower, and can interact with a polyvalent metal ion compound to form a metal chelated pigment. layer, and a heat-fusible transfer layer containing a polyvalent metal ion compound and a heat-fusible substance. A preferred embodiment of the recording medium of the present invention is that the coloring material layer contains a heat-fusible substance. The present invention will be explained below. The non-sublimable dye used in the present invention is one that is capable of forming a metal chelated dye by interacting with a polyvalent metal ion compound (this is called chelating ability), and that has a temperature of 300°C or less. It is a dye that does not sublimate or substantially vaporize at a temperature of 300°C or less, and the dye has a melting point of 300°C or less and exhibits migration properties, and is particularly preferably a solid or semi-solid with a temperature of 50°C to 250°C. . The dye is preferably a non-sublimable dye that can form a chelate with a polyvalent metal ion compound represented by the following general formula (1) or (2). General formula (1) In the formula, X ¹ represents a group of atoms necessary to complete an aromatic carbocyclic or heterocyclic ring in which at least one ring is composed of 5 to 7 atoms, and the carbon bonded to the azo bond. At least one of the adjacent positions of is (a) a nitrogen atom, or (b) a carbon atom substituted with a nitrogen atom, an oxygen atom, or a sulfur atom, and the ring may be further substituted with a substituent, which is preferable. Substituents include alkyl groups, alkoxy groups,
These include a cyano group, a nitro group, a thiol group, a thioalkoxy group, or a halogen atom. X ² represents an aromatic carbocyclic or heterocyclic ring in which at least one ring is composed of 5 to 7 atoms, and the ring may be substituted with an appropriate substituent; preferable rings include: Alkyl group, alkoxy group, cyano group, nitro group, hydroxyl group, amino group, sulfamoyl group, carbamoyl group, acyl group, alkyloxycarbonyl group, acyl group, alkyloxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group At least one of the substituents is a group having a shape or size that suppresses the sublimation property of the dye, that is, a group having 6 or more carbon atoms (more preferably 12 carbon atoms). It is preferable that the substituent is a ballast group containing (1 or more) and/or a substituent containing a group derived from acids (carboxy group, sulfo group, etc.). General formula (2) In the formula, X ¹ has the same meaning as defined in the above general formula (1). Z ¹ is an electron-withdrawing group and preferably represents an acetyl group, a substituted and unsubstituted benzoyl group, a cyano group or an acetamido group, and Z ² represents an alkyl group or an aryl group. The ballast group not only suppresses sublimation, but also lowers the melting point of the dye or facilitates compatibility between the dye and a heat-melting substance, thereby increasing the transfer efficiency of the dye. Particularly preferred is substitution with . Specific examples of the dye represented by general formula (1) or general formula (2) are shown below. The polyvalent metal ion compound used in the present invention is
Any compound containing a polyvalent metal ion may be used, but a salt or a complex containing a polyvalent metal ion is preferable, and examples of the polyvalent metal ion include copper (), nickel (), and zinc (). , platinum ( ), palladium ( ), cobalt ( ) or aluminum ( ). The salts containing polyvalent ions include inorganic salts of the polyvalent metals (hydrochlorides, sulfates, nitrates, phosphates, etc.);
Preferred examples include organic salts such as alkyl carboxylic acids, aryl carboxylic acids, alkyl sulfonic acids, arylsulfonic acids, alkyl phosphoric acids, and aryl phosphoric acids. In order to carry out an exchange reaction, a complex having a not too strong coordination bond, that is, a stability constant of the complex of 10 ³ to 10 ¹² , particularly preferably 10 ⁶ is used.
~ ¹⁰⁸ is preferred. In the present invention, the heat-fusible substance contained in the heat-fusible transfer layer may be any substance that is solid or semi-solid at room temperature but melts into a liquid state when heated; Colorless or fair-skinned compounds having a melting point of ~200°C are preferred, such as waxes such as carnauba wax, beeswax and candelilla wax, higher fatty acids such as stearic acid and behenic acid, alcohols such as xylitol, acetamide and benzamide, etc. Examples include amides, ureas such as phenyl urea and diethyl urea. In addition to these, low melting point substances described in, for example, JP-A-54-68253 can also be used. In the present invention, an intermediate layer may be provided between the coloring material layer and the heat-melting transfer layer. The recording medium of the present invention may have other constituent layers as necessary, such as a barrier layer (preferably a gelatin layer) that prevents a heat-transferable non-sublimable dye from migrating to the support during thermal transfer. Alternatively, an undercoat layer, a protective layer, etc. may be provided. Further, the coloring material layer in the present invention does not need to be one layer, and may be two or more layers. Each of the constituent layers used in the present invention may contain various additives. For example, color tone adjusting agent,
Antioxidants, ultraviolet absorbers, etc. may be added to any constituent layers. The recording medium of the present invention can be produced by a known coating method such as wire bar coating, roll coating, or gravure coating. For example, it can be produced by sequentially coating a coloring material layer and a heat-fusible transfer layer on a support. It is desirable that Specifically, a non-sublimable dye with chelating ability is coated onto a support using an appropriate binder, or only the dye is coated onto a support to form a coloring material layer, and then a heat-melting layer is formed on the support. The heat-fusible transfer layer may be formed by applying a heat-fusible material together with a polyvalent metal ion compound using a suitable binder, or by applying the heat-fusible material itself to also serve as a binder. Incidentally, during such coating, a suitable intermediate layer may be provided between the coloring material layer and the heat-fusible transfer layer. Furthermore, a heat-fusible substance may be added to the coloring material layer. Furthermore, it is also optional to provide an overcoat layer, an undercoat, etc. The coating method includes heating the compound,
Can be applied by hot melt coating. As the coating means, wire bar coating, roll coating, gravure roll coating, etc. are used. It can also be dissolved in a solvent such as toluene or xylene and applied using a similar application method. The binder may be selected from hydrophilic binders, hydrophobic binders, etc. depending on the type of dye of the present invention, and examples thereof include polyvinyl butyral, polyvinyl acetate, polyvinyl alcohol, polystyrene, and styrene. Threulose esters such as butadiene copolymers and ethyl cellulose, acrylic resins such as methyl methacrylate, gelatin, and the like can be used. As the support, a support having heat resistance strength and high smoothness is desirable. Heat resistance strength is required to maintain the toughness of the support without softening or plasticization due to the heating temperature of the thermal head, and smoothness is sufficient to ensure that each layer on the support exhibits a good transfer rate. A good level of smoothness is desired. Smoothness is determined by the smoothness hazard (JIS
P8119) is preferably 100 seconds or more, and 300 seconds or more will yield images with better transfer rate and reproducibility. As the material, for example, papers such as plain paper, synthetic paper, and laminated paper, resin films such as polyethylene, polystyrene, polypropylene, and polyimide, and paper-resin film composites are all suitably used. The thickness of the support is usually about 60 μm in order to obtain good thermal conductivity.
It is preferable that it is below. The heat of each layer of the thermal transfer recording medium created as described above is approximately 1 to 20 μm.
Desirably in order to obtain a good image, one layer preferably has a thickness of 15 μm or less, particularly preferably 2 μm to 8 μm
That's about it. Note that the amount of the non-sublimable dye having chelating ability contained in the coloring material layer used in the present invention and the polyvalent metal ion compound contained in the heat-melting transfer layer is not limited, and the amount of the polyvalent metal ion compound used in the recording is not limited. As a result of trial work, in order to obtain a robust image with chelated dye on the recording sheet, depending on the heating temperature and time, etc.
All you have to do is ask. Next, a recording method using the recording medium of the present invention will be explained. When energy is applied to the heat-sensitive transfer recording medium under the stack of recording sheets from the support side using a thermal head, thermal pen, etc. according to the image information to be recorded, the heat-fusible transfer layer will maintain a constant value. By applying the above energy, the dye is transferred to the recording sheet, and the dye is transferred from the coloring material layer according to the amount of thermal energy, and the polyvalent metal ion and chelate, which are stable against heat, light, etc., are transferred onto the recording sheet. A colored dye image is obtained. Therefore, the recording sheet may be plain paper, and it is also possible to provide a fast dye image on various plastic films, cloth, etc. Note that the recording sheet may contain a polyvalent metal ion compound, and the method of containing the compound is arbitrary. It can be applied to the recording sheet using a binder, impregnated or contained in the recording sheet by dipping or spraying, further added during paper making, or kneaded during film molding. It may also depend on [Example] Preferred examples of the present invention are shown below, but the present invention is not limited to these examples. First, the means for producing a thermal transfer recording medium will be explained based on FIG. First, apply the following composition to a 6μ thick polyethylene terephthalate film base 1 to a wet film thickness.
It was applied using a wire bar to a thickness of 59.4μ and dried to form coloring material layer 2. Cellulose diacetate 0.6g Specific example of the dye (1) 0.5g Acetone 20ml Next, the following composition was coated on the coloring material layer 2 to a wet film thickness of 27.4μ, and dried to form a heat-fusible transfer layer. 3 to prepare a thermal transfer recording medium A. Permarin PN (manufactured by Sanyo Kasei) 10ml Copper acetylacetone () 0.30g Water 10ml 2% anionic activator 0.3ml Next, a thermal transfer recording test using the thermal transfer recording medium A described above will be described based on FIG. That is, the surface coated with the color material layer, etc. of the thermal transfer recording medium A and the white plain paper 4 serving as the recording sheet are stacked facing each other, and heat is generated by the thermal head 5 from the support 1 side of the thermal transfer recording medium A. A transfer recording test was conducted by heating the dye through body 6 to transfer the dye together with the heat-fusible substance. As a result, a transferred image 7 of the metal chelated dye appears on the recording sheet.
was gotten. In this test, when the temperature of the thermal head 5 and/or the voltage application time were changed, the amount of dye transferred varied depending on the amount of thermal energy applied, and a magenta image with gradation was obtained. Rare ra ta. The maximum transfer density (Dmax) is 1.55.
It was hot. As described above, it has been found that, according to the present invention, by a simple operation of changing the temperature of the thermal head 5 or the application time, multi-gradation of an image can be obtained corresponding to each change. Next, the gradation storage stability of the thermal transfer recording medium and the light fastness test of the transferred recorded image will be described. First, thermal transfer recording media B to E were each prepared using the same composition as the thermal transfer recording medium A and using the same means except for the following composition changes. Thermal transfer recording medium B: 0.3 g of carnauba wax was added to the coloring material layer. C...The dye in thermal transfer recording medium B was replaced with dye 3. D...The dye in thermal transfer recording medium B was replaced with specific example (8) of dye Dye. E...The polyvalent metal ion compound of recording medium B is N,N
- Substituted with a nickel complex of di(hydroxycarbomethyl)aniline. Further, as a comparative example, F was obtained by removing the polyvalent metal ion compound (copper acetylacetone ()) from the thermal transfer recording medium B, and G was obtained by removing the heat-melting transfer layer. Furthermore, a heat-sensitive transfer recording medium H was prepared by replacing the dye of the thermal transfer recording medium A with the following sublimable dye. Next, the coated surfaces of each of the above-mentioned thermal transfer recording media A to H were superimposed on plain paper, and the surface temperature was set to 170.
A thermal plate (4 cm x 1 cm) at 0.degree. C. was pressed for 1 second to obtain a transferred image on plain paper. The results are shown in Table 1 (see the section on transfer density in the same table). From the above results, it can be seen that the recording media A to E of the present invention can provide transferred images with higher density than Comparative Example G. Next, the thermal transfer recording media A to E and H were left at a temperature of 60° C. for one week, and then transferred onto plain paper in the same manner as above, and the gradation properties were examined. This result is the first
As shown in the table (see section on shelf life in the same table). Next, the transferred image obtained in the same manner was irradiated with a 6000W xenon lamp for 48 hours (the illuminance on the image surface was
6000 Lux), λmax before and after exposure
The optical density (D ² ₀ before exposure, D ² after exposure) was measured using D ² /D ² ₀ × 100 (%) as the residual rate, and the light resistance was tested. These results are shown in Table 1.

[Table] As is clear from the same table, when thermal transfer recording media A to E of the present invention are used, compared to thermal transfer recording medium F, which does not contain a polyvalent metal ion compound in the heat-fusible transfer layer, It can be seen that the light resistance is very good. The preferred embodiment of the present invention has been described above, that is, the case where the dye is transferred from the thermal transfer recording medium by applying heat to the thermal head or the heating element of the thermal plate, but the present invention is not limited to this, for example, from the support side A laser beam such as a helium-neon laser, a carbon dioxide laser, or a YAG laser may be irradiated to impart thermal energy to the thermal transfer recording medium to transfer the dye and form an image.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the case of thermal transfer using the thermal transfer recording medium of the present invention, and Fig. 2 is a diagram after thermal transfer. Each figure schematically shows the constituent layers, and the thickness ratio of each constituent layer is shown. It's not something I did. In the figure, 1 is a support, 2 is a coloring material layer, 3 is a heat-melting transfer layer, 4 is a recording sheet, 5 is a thermal head,
6 shows a heating element, and 7 shows a dye image.

Claims (1)

[Scope of Claims] 1. Substantially no photosensitive component is present on the support, does not sublimate or substantially vaporize at a temperature of 300°C or lower, melts at a melting point of 300°C or lower, and exhibits migration properties. show,
and a coloring material layer containing a non-sublimable dye that can act with a polyvalent metal ion compound to form a metal chelated dye, and a heat-melting layer containing a polyvalent metal ion compound and a heat-melting substance. 1. A heat-sensitive transfer recording medium comprising a transfer layer. 2. The heat-sensitive transfer recording medium according to claim 2, wherein the coloring material layer contains a heat-fusible substance.