JPH0377794B2 - - 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, it is a heat-sensitive transfer recording medium capable of producing a dye image having high sharpness and multi-gradation, which is stable against heat, light, etc., on a recording sheet such as plain paper through a heat transfer process using a heat-transferable dye. Regarding. [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. In these methods, there are problems with the stability of the image against heat and light due to the use of thermal paper, and there are also disadvantages of high manufacturing costs.Furthermore, for colorization, it is necessary to have multiple coloring layers. The drawback was that there was a limit to the degree of color. As a thermal recording method that solves the above-mentioned 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 Japanese Patent Application Laid-open 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 if a certain amount of thermal energy or more is applied, all the coloring material is transferred, making it difficult to obtain gradation of the image. 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 a sublimable dye is used in the recording medium, the sublimable dye deteriorates due to diffusion or disappearance due to sublimation over time, resulting in poor storage stability. In addition, sublimation transfer type uses sublimable dyes for image formation, so there are problems with image fixability and storage stability due to re-sublimation of the dyes, and especially when transferring to plain paper, color density may decrease. There was a drawback that the color density was significantly reduced due to low color density and re-sublimation of the dye over time. [Object of the Invention] Therefore, the first object of the present invention is to provide a thermal transfer recording medium that has excellent shelf life. 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] A heat-sensitive transfer recording medium that achieves the above object has, on a support, a coloring material layer that does not substantially contain a photosensitive component and a heat-fusible transfer layer that contains a heat-fusible substance. In the heat-sensitive transfer recording medium, the dye layer contains a complex compound formed by a heat-transferable dye and a polyvalent metal ion, and a ligand having a coordination force that can exchange ligands with the complex compound during heating. It is characterized in that it contains a phase exchange agent, and the heat-melting transfer layer or the recording sheet for forming an image contains a polyvalent metal ion compound. The present invention will be explained in detail below. The polyvalent metal ions used in the present invention include:
Ions such as copper (), nickel (), zinc (), platinum (), palladium (), cobalt () or aluminum () are preferred. The polyvalent metal ions are supplied from salts or complexes containing polyvalent metal ions, and the salts include inorganic acid salts (hydrochlorides, sulfates, nitrates, phosphates, etc.) of the polyvalent metals, alkyl carbonates, etc. acid, arylcarboxylic acid,
Organic acid salts such as alkylsulfonic acid, arylsulfonic acid, alkylphosphoric acid, and arylphosphoric acid are preferred, and as the complex containing the polyvalent metal ion, in order to perform a rapid ligand exchange reaction, Preferred are complexes in which the position bond is not too strong, that is, the stability constant of the complex is 10 ³ to 10 ¹² , particularly preferably 10 ⁶ to 10 ⁸ . The heat-transferable dye used in the present invention may be any dye that can be melted, sublimated, or vaporized by heat, and is heat-transferable, but preferably it is a sublimable or vaporizable dye, and it has a bidentate or more dentate relationship with a metal ion. These are azo, azomethine, anthraquinone, indigo, nitro, and other dyes that can form a complex with a ligand of the following general formula (1) or
It is a pigment represented by (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,
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: Examples include a benzene ring, a naphthalene ring, a pyridine ring, and a quinoline ring, and preferred substituents include an alkyl group, an alkoxy group, a cyano group, a nitro group, a hydroxyl group, an amino group, and a halogen atom. G represents a chelating group, and preferred chelating groups include a hydroxyl group, an amino group, a methoxy group, a thiol group, and a thioalkoxy group. 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, preferably an acetyl group, a substituted unsubstituted benzoyl group, a cyano group or an acetamido group, and Z ² is an alkyl group (preferably a methyl group) or an aryl group (preferably a phenyl group). represent. Specific examples of the dye represented by general formula (1) or general formula (2) are shown below. [Specific examples of Dye] (1) 1-(2-pyridylazo)-2-naphthol(2) 1-(4-hydroxy-2-pyridylazo)-
2-naphthol (3) 2-(2-hydroxyphenylazo)-5-hydroxypyridine (4) 2-(2-pyridylazo)-4-methoxy-1
-Naphthol(5) 2-(4-nitro-2-pyridylazo)-4-
Methoxy-1-naphthol(6) 1-(2-hydroxyphenylazo)-2-naphthol(7) 1-(2-aminophenylazo)-2-naphthol(8) 2-(2-hydroxyphenyl azo)-5-methoxyphenol (9) 8-(2-hydroxyphenylazo)-quinoline (10) 3-(2-hydroxyphenylazo)-2,4
-Pentadione (11) 1-phenyl-2-(2-hydroxyphenylazo)-1,3-butanedione (12) α-(2-hydroxyphenylazo)-β-
Hydroxycinnamonitrile (13) 2-(4-nitro-6-methyl-2-pyridylazo)-4-methoxy-1-naphthol (14) 2-amino-3-hydroxy-6-(2-
hydroxyphenylazo)-pyridine (15) 2-(N,N-dimethylamino)-3-hydroxy-6-(2-hydroxy-4-nitrophenylazo)-pyridine (16) 1-phenyl-3- Methyl-4-(2-pyridylazo)-5-pyrazolone (17) 1-(2-amineethylamino)-4-hydroxyanthraquinone (18) 1,4-diaminoanthraquinone (19) 1-amino-4-hydroxyanthraquinone In the present invention, the complex compound contained in the color material layer is a complex formed by the heat-transferable dye and the polyvalent metal ion, and for example, the dye and an inorganic metal salt are mixed in a suitable solvent. It is obtained by stirring the mixture in a filtrate and collecting the precipitate by filtration. In the present invention, the ligand exchange agent contained in the coloring material layer may be any compound having a coordination power capable of exchanging ligands with the complex compound during heating,
Preferably, the stability constant when forming a complex is
10 ¹⁴ or more compounds, such as ethylenediaminetetraacetic acid (EDTA), cysteine, tri(aminoethyl)amine, triethylenetetramine, 1,
2-Cyclohexanediaminetetraacetic acid (CyDTA)
etc. In the present invention, the heat-melting substance contained in the heat-melting transfer layer formed on the coloring material layer is solid or semi-solid at room temperature, but may be any substance as long as it melts and becomes liquid when heated. However, compounds with a low melting point, that is, colorless or white compounds having a melting point of 35°C to 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, xylitol, etc. Examples include alcohols, amides such as acetamide and benzamide, and ureas such as phenylurea and diethylurea. 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 providing a barrier layer (preferably a gelatin layer) to prevent the heat-transferable dye from migrating to the support during thermal transfer. Alternatively, a subbing 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, a color tone adjusting agent, antioxidant, ultraviolet absorber, etc. may be added to any constituent layer. The recording medium of the present invention can also be produced by a known coating method such as wire bar coating, roll coating, or gravure coating. Created. Specifically, a complex compound formed by a heat-transferable dye and a polyvalent metal ion and a ligand exchange agent are coated on a support using an appropriate binder, and then a polyvalent metal ion compound (if necessary) is coated on the support. ) and a heat-fusible substance together with a suitable binder (or the heat-fusible substance itself also serves as a binder) to form a heat-fusible transfer layer. At the time of such coating, an appropriate intermediate layer may be provided between the coloring material layer and the heat-melting transfer layer, and an overcoat layer, a bayer layer, etc. may optionally be provided. The binder may be selected from hydrophilic binders, hydrophobic binders, etc. depending on the type of heat-transferable dye, and examples thereof include polyvinyl butyral, polyvinyl acetate, polyvinyl alcohol, polystyrene, and styrene. Cellulose 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 was determined by smoothness test using a Beck tester (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 preferably 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 heat-sensitive transfer recording medium produced 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 amounts of complex compounds and ligand exchange agents contained in the colorant layer used in the present invention, and the polyvalent metal ion compounds contained in the heat-melting transfer layer or recording sheet are not limited and are not limited to the amounts used in the recording. Depending on the heating temperature and time, the use and type of the recording sheet, etc., it may be determined through trial work that a stable image with a dye, especially a chelated dye, can be obtained on the recording sheet. Next, a thermal transfer recording method using the recording medium of the present invention will be explained. When energy is applied to the thermal 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, thermal energy exceeding a certain value is generated. A heat-migratory dye is released by coordination exchange between a complex compound containing a migratory dye and a ligand exchange agent, and the released dye moves according to the amount of energy, and at the same time, before or after this, heat transfer occurs. The meltable transfer layer is transferred to the recording sheet by applying a certain amount of energy, and an image is obtained on the recording sheet using the metal chelated pigment formed by the action of the polyvalent metal ion and the pigment. In this case, it is not necessary to contain polyvalent metal ions in the recording sheet, and the recording sheet may be plain paper, and furthermore, a robust dye image can be provided on various plastic films, cloth, and the like. Images produced using this metal chelate dye not only have excellent sublimation resistance or vaporization resistance, but also excellent light resistance, heat resistance, moisture resistance, and the like. [Effects of the Invention] According to the present invention, it is possible to provide a heat-sensitive transfer recording medium that has excellent raw storage stability, and also has a high transfer density on a recording sheet such as plain paper, and has good thermal stability and light resistance. It is possible to provide a heat-sensitive transfer recording medium from which a dye image with excellent multi-tonal properties can be obtained. [Example] Preferred examples of the present invention are shown below, but the present invention is not limited to these examples. Example 1 The following composition-A was dispersed in an alumina ball mill, and the dispersion was mixed into a 6 μm powder having a gelatin subbing layer 2.
A coloring material layer 3 was formed on a polyethylene terephthalate film base 1 of 500 m in diameter using a wire bar to give a wet film thickness of 59.4 μm and drying. (Composition-A) Cobalt complex of specific example (1) of the dye 1.0g Sodium dodecylbenzenesulfonate
0.067g Gelatin 1.25g Ligand exchange agent (EDTA/disodium salt)
3.0 g Distilled water 100 ml Next, the following composition B was coated on the coloring material layer 3 to a wet film thickness of 27.4 μm and dried to form a heat-melting transfer layer 8, and a heat-sensitive transfer recording medium B-1 was formed. (See Figure 1). (Composition-B) Permarin PN (manufactured by Sanyo Chemical Co., Ltd.) 10ml Copper acetylacetone 0.25g Water 10ml 2% anionic activator 0.3ml Next, the thermal transfer recording test using the thermal transfer recording medium B-1 is shown in Figure 2 and This will be explained based on FIG. The surface coated with the transfer layer 8 of the thermal transfer recording medium B-1 and the white plain paper 9 serving as the recording sheet are stacked facing each other, and the thermal head 5 is applied from the support 1 side of the thermal transfer recording medium B-1. A transfer recording test was conducted in which the dye and the heat-fusible transfer layer were transferred by heating via a heating element 6 to form an image 7 of a metal chelated dye on plain paper 9. In this test as well, when the voltage application time of the thermal head 5 was varied, a transferred image with gradation was obtained. Note that the highest concentration was 1.65. Next, the storage stability and light fastness of the image formed on the recording sheet, as well as the storage stability test of the recording medium, will be described. First, thermal transfer recording media B-2 to B-6 were prepared using the same composition as the thermal transfer recording medium B-1 and using the same method except for the following composition changes. Thermal transfer recording medium B-2...Specific example of dyeing the dye in composition A (13)
I replaced it with B-3... Specific example of dyeing the pigment in composition A (16)
I replaced it with B-4...Specific example (1) of dyeing the complex compound in composition A
and a complex with zinc () ion. B-5...The polyvalent metal ion compound in composition B was replaced with nickel chloride. B-6...The polyvalent metal ion compound in composition B was replaced with a nickel complex of salicylic acid. Furthermore, as a comparative example, the thermal transfer recording medium B
In -1, B-2 and B-3, the dye was not made into a complex of polyvalent metal ions, but only the dye was contained in the coloring material layer, and these were used as thermal transfer recording media D, E and F, respectively. . Comparative thermal transfer recording media B-1, B-2, and B-3 were prepared in the same manner except that the ligand exchange agent was removed from the coloring material layer, and were designated as G, H, and I, respectively. Immediately after each of the above thermal transfer recording media was produced, they were superimposed on a recording sheet, and a thermal plate (4 cm x 1) having a surface temperature of 170°C was pressed for 1 second to give a transferred image (transfer density -1) to the recording sheet. Next, each of the above thermal transfer recording media was left at a temperature of 80 DEG C. for one week, and then a transferred image (transfer density -2) was provided in the same manner. Next, the transferred recording sheet was left at 80℃ for one week, and the optical density measured by λmax before and after (before and after)
D ⁰ , D ¹ ) were measured, and the thermal stability of the image was tested using D ¹ /D ⁰ ×100 (%) as the residual rate. In addition, 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 table, the thermal transfer recording media B-1 to B-6 of the present invention have excellent storage stability, and the obtained images are also stable against heat and light. I understand that there is something. Furthermore, it is particularly excellent in providing images with excellent thermal stability (fixing properties) and light fastness on plain paper. A preferred embodiment of the present invention has been described above, that is, a case in which dyes are transferred from a thermal transfer recording medium by applying heating with a heating element of a thermal head, but the present invention is not limited thereto. , carbon gas laser,
The heat-sensitive transfer recording medium may be irradiated with a laser beam such as a YAG laser to generate heat to transfer the dye and form an image.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the thermal transfer recording medium of the present invention, Fig. 2 is a diagram when thermal transfer is performed using the recording medium shown in the above figure, and Fig. 3 is a diagram after thermal transfer. It is a constituent layer and does not represent the thickness ratio of each constituent layer. In the figure, 1 is a support, 2 is a subbing layer, 3 is a coloring material layer,
5 is a thermal head, 6 is a heating element, 7 is a dye image, 8 is a heat-melting transfer layer, and 9 is a recording sheet.

Claims (1)

[Claims] 1. A heat-sensitive transfer recording medium having, on a support, a coloring material layer that does not substantially contain a photosensitive component and a heat-melting transfer layer containing a heat-melting substance, in which the coloring material layer contains a heat-transferable dye. and a polyvalent metal ion, and a ligand exchange agent having a coordination power capable of exchanging ligands when the complex compound is heated, and the heat-melting transfer agent A heat-sensitive transfer recording medium characterized in that a layer or a recording sheet for forming an image contains a polyvalent metal ion compound.