Use of hydrophobic cationic dye in an ink layer of a thermal transfer ink ribbon

Abstract: When the counter ion of hydrophilic cationic dyes is substituted with an organic anion including a sulfosuccinate anion such as diethylhexylsulfonate anion, an alkylbenzenesulfonate anion such as a dodecylbenzenesulfonate, an alkylsulfate anion such as a laurylsulfate anion, or a soap anion such as a laurylsulfate anion, the cationic dyes are imparted with hydrophobicity. An ink layer 3 containing the hydrophobic cationic dye is formed on a support 2 to provide a thermal transfer ink ribbon 10.

Description: This invention relates to the use of hydrophobic cationic dyes which are adapted for use in image formation by a thermal transfer system and also to thermal transfer ink ribbons. Background In recent years, video printers for obtaining hard copies of images from video signals have been intensively developed. The images have been formed according to thermal transfer systems. More particularly, an ink ribbon comprised of a polyethylene terephthalate substrate and an ink layer formed by mixing a dye with or dissolving the dye in a hydrophobic polymer is provided. The ink layer is superposed in a dye-receiving hydrophobic polymer layer of a transfer material formed on a synthetic paper, under which the ink ribbon is heated according to image signals by means of a thermal head or the like. As a result, a disperse dye in the ink layer is thermally transferred to the dye-receiving layer to form an image. As the dyes of the thermal transfer ink ribbons which are employed in the thermal transfer system, sublimable dyes have been heretofore considered principally favorable from the standpoint of the image formation. According to recent investigative trends wherein types of materials have been taken into account, importance is placed on thermal diffusing properties rather than sublimability. Moreover, there are other important properties or factors of the dyes including miscibility with hydrophobic polymers used in the ink layer of the thermal transfer ink ribbon, dyeability against the dye-receiving layer consisting of hydrophobic polymers of the transfer material, and a degree of achievement of actual sensitivity at the time of the thermal transfer. To this end, disperse dyes have been frequently used as a dye for the thermal transfer ink ribbons. However, when disperse dyes are used as the dye for thermal transfer ink ribbons, there arises the problem that they are unsatisfactory in practical utility from the standpoint of the sensitivity during the transfer operations and the hue and light fastness of the resultant images. To avoid this, it may occur that cationic dyes which are known for dyeing acrylic fibers as having an inherent brightness, high coloring properties and good light fastness are used for the thermal transfer ribbons. Although the cationic dyes exhibit good light fastness and wet fastness, they are hydrophilic in nature, so that it is difficult to uniformly, stably keep the dye in butyryl resins ordinarily used as the binder of the ink layer of thermal transfer ink ribbons. Thus, it has not been possible for cationic dye to be used in the thermal transfer ink ribbon. The patent CH-A-374 135 discloses a process for the production of water-insoluble dyes. These dyes are prepared by reacting a water-soluble alkaline dye with a compound that releases an organic or an inorganic anion that is able to form, with the dye cation, a water-insoluble salt. The staining of estron using these dyes is described. DE-A-2 362 649 discloses colouring agents which contain alkaline dyes and are obtained by reacting and dispersing a water-soluble dye with an excess of an anionic dispersing agent. The product is a dispersion of water-insoluble dye salts in dispersing agent that can be used to stain textiles. Summary of the Invention An object of this invention is to provide ink layers for thermal transfer ink ribbons which contain a hydrophobic polymer and a dye, wherein, firstly, said dye can be mixed with said hydrophobic polymer satisfactorily and uniformly with good storage stability and, secondly, said dye provides for improved sensitivity at the time of the transfer and for improved color and light fastness of the resultant images. According to one aspect of this invention, there is used a hydrophobic cationic dye which is obtained by substituting, with an organic anion, a counter ion of a diazacarbocyanine cationic dye of the formula (1) wherein R1, R2, R3 and R4 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy roup, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, and Z- represents a counter ion in ink layers of thermal transfer ink ribbons. According to another aspect of this invention, there is provided a thermal transfer ink ribbon which comprises a support and an ink layer formed on the support, wherein the ink layer comprises a hydrophobic cationic dye which is obtained by substituting, with an organic anion, a counter ion of a diazacarbocyanine cationic dye of the formula (1) wherein R1, R2, R3 and R4 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, and Z- represents a counter ion. Brief Description of the Drawings Figure 1 shows a sectional view of a thermal transfer ink ribbon of the invention. Figure 2 is a dynamic sensitivity characteristic graph of an ink ribbon of the invention. Figure 3 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 4 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 5 is a dynamic sensitivity characteristic graph of still another ink ribbon of the invention. Figure 6 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 7 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 8 is a dynamic sensitivity characteristic graph of yet another ink ribbon of the invention. Figure 9 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 10 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 11 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 12 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Figure 13 is a dynamic sensitivity characteristic graph of another ink ribbon of the invention. Description of the Preferred Embodiments We have found that the substitution of a counter ion, such as a halogen, of cationic dyes with an organic anion enables the cationic dyes to be imparted with hydrophobicity and that specific type of dyes have good gradation properties with respect to yellow, magenta and cyan colors necessary for the formation of full color images. The invention is accomplished based on this finding. The invention makes use of a yellow dye, a hydrophobic cationic dye which is obtained by substituting, with an organic anion, a counter ion of a diazacarbocyanine cationic dye of the formula (1) wherein R1, R2, R3 and R4 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, and Z- represents a counter ion. Examples of the cationic dyes not substituted with an organic anion include C.I. Basic Yellow 28 and 51. Another type of yellow dye provided for use according to the invention includes hydrophobic cationic dyes which are obtained by substituting the counter ion of a cationic dye such as C.I. Basic Yellow 21, 36, 67 or 73 with an organic anion. The invention also makes use of a magenta dye, a hydrophobic cationic dye which is obtained by substituting, with an organic anion, a counter ion of a hemicyanine cationic dye of the formula (2) wherein R21, R22 R23, R24 and R25 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, provided that R24 and R25 may join together to form a ring, and Z- represents a counter ion. Examples of the cationic dyes prior to substitution with an organic anion include C.I. Basic Red 13, 14, C.I. Basic Violet 7, 16, C.I. 48025 and 48030. Moreover, the invention makes use of, as a cyan due, a hydrophobic cationic dye which is obtained by substituting, with an organic anion, a counter ion of an oxazine cationic dye of the formula (3a) or (3b). wherein R31, R32, R33, R34, R35, R36, R37, R38, R39, R310, R311 and R312 independently represent a hydrogen atom, a halogen atom, a cyano group, on alkyl group, a cyoloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, a aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, provided that R31 and R32, R33 and R34, R37 and R38, R39 and R310, R310 and R311, and R311 and R312 may, respectively, join together to form a ring, and Z- represents a counter ion. Examples of the cationic dyes prior to the substitution with the organic anion include C.I. Basic Blue 3, 6, 10, 12, 49, 75, 87, 95, 96, 101, 104, 107, 108, 114 122, 124, 141, 151 155 and C.I. 51015. The present invention also provides a thermal transfer ink ribbon which comprises a support and an ink layer formed thereon, characterized in that the ink layer comprises any of these hydrophobic cationic dyes. The organic anions used in the present invention are those which can render the hydrophilic cationic dyes hydrophobic by substituting the counter ion of the cationic dye therewith. Such organic anions are those ions of anionic surface active agents indicated below. It will be noted here that these organic anions may be available as salts of alkali metals prior to the substitution with the counter ion of the hydrophilic cationic dyes. (1) Carboxylic acid anions (1a) Soaps (RCOO-) (1b) N-Acylamino acids (RCON-COO-) (1c) Alkyl ether carboxylic acids (RO(C 2 H 4 O) n COO-) (2) Sulfonic acid anions (2a) Alkylsulfonates ((RSO 3 -) (2b) Alkylbenzenesulfonates (formula (4)) (2c) Alkylnaphthalenesulfonates (formula (5)) (2d) Sulfosuccinates (formula (6)) (2e) a -Olefinsulfonates (2f) N-acylsulfonates (-CON-SO 3 -) (3) Sulfuric ester anions (3a) Sulfated oil (3b) Alkylsulfates (ROSO 3 -) (3c) Alkyl ether sulfates (RO(C 2 H 4 O) n SO 3 -) (3d) Alkyl aryl ether sulfates (formula (7)) (3e) Alkylamidosulfates (RCONH-OSO 3 -) (4) Phosphoric ester anions (4a) Alkylphosphates (formulas (8), (9)) (4b) Alkyl ether phosphates (formulae (10), (11)) (4c) Alkyl aryl ether phosphates In the above organic anions, it is preferred that R, Ra and Rb, respectively, represent a linear or branched alkyl or alkenyl group having 5 - 20 carbon atoms from the viewpoint of the ease in availability and costs. Of these organic anions, it is preferable to use sulfosuccinate anions of (2d) such as diethylhexylsulfosuccinate anion, alkylbenzenesulfonate anions of (2b) such as dodecybenzenesulfonate anion, alkylsulfate anions of 3b) such as lauryl sulfate anion, and soap anions of (1a). The hydrophobic cationic dyes used according to the invention can be obtained by dropping an aqueous solution of salts containing the above-indicated organic anions in an aqueous solution of a hydrophilic cationic dye under agitation, extracting the resulting mixture with an organic solvent such as toluene, and removing the solvent from the organic phase to obtain a hydrophobic dye as a residue insoluble or sparingly soluble in water. As a matter of course, the hydrophobic cationic dyes used according to the invention are hydrophobic in nature, so that they can be uniformly, stably, mixed with hydrophobic resins which would not be otherwise used along with known hydrophilic cationic dyes. For instance, the above hydrophobic cationic dyes can be uniformly, stably mixed with hydrophobic polymer binders for use in the ink layer of a thermal transfer ink ribbon and are thus suitable for use as the dye of thermal transfer ink ribbons. Accordingly, a thermal transfer ink ribbon composed of a support and an ink layer formed thereon wherein the ink layer contains the above hydrophobic cationic dye is within the scope of the invention. The ink layer of the thermal transfer ink ribbon of the invention may be constituted of the above hydrophobic cationic dye alone. If necessary, other ingredients such as hydrophobic polymer binders, melting point adjusting agents, plasticizers, solvents, binders, and pigments and dyes other than the hydrophobic cationic dyes used according to the invention can be used. The support of the thermal transfer ink ribbon of the invention may be, for example, polyethylene terephthalate films, nylon films, triacetyl cellulose films, moistureproof cellophane sheets, capacitor paper, thin paper, cloth the like. The thermal transfer ink ribbon of the invention may be fabricated by a usual manner. For instance, an ink composition comprising the above hydrophobic cationic dye is applied onto a support by use of a wire bar coater to obtain a ribbon. In order to form color images on a transfer material by the use of the thermal transfer ink ribbon of the invention, the ink layer of the ink ribbon and the dye-receiving layer of the transfer material are placed in face-to-face relation, under which an image-forming portion is heated from the support side of the ink ribbon by means of a thermal head of a laser beam of a printer, thereby causing the dye ingredient in the ink layer to be transferred on the image-receiving layer by sublimation or thermal diffusion. The hydrophobic cationic dyes used according to the invention are rendered hydrophobic by substitution of the counter ion of the hydrophilic cationic dye with an organic anion, making it possible to enhance miscibility with non-aqueous solvents and hydrophobic polymers. Thus, the above dyes are usable as a dye for the thermal transfer ink ribbon. The invention is more particularly described by way of examples. Example 1 - Preparation of a diethyhexylsulfosuccinate of C.I. Basic Yellow 28 1 g of C.I. Basic Yellow 28 (commercial name: Kayacryl Golden Yellow GL available from Nippon Kayaku K.K.) which is a diazacarbocyanine cationic dye for dyeing acrylic fibers from which additives such as sodium sulfate were removed by a Soxhlet apparatus using ethanol was dissolved in 100 ml of water. While agitating the dye solution, 50 g of a 2 wt% sodium diethylhexylsulfosuccinate aqueous solution was dropped in the dye solution to substitute the counter ion with an organic anion (diethylhexylsulfosuccinate anion). The resultant solution was evaporated to dryness under reduced pressure. Toluene was added to the resultant residue for extraction of the dye. The toluene solution of the dye was filtered to remove an unreacted matter and side products (inorganic salts). the filtrate was concentrated to dryness under reduced pressure. As a result, about 1.6 g of the captioned hydrophobic cationic dye with a dark orange in the form of a tar was obtained. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon it was found most of the dye remained in the toluene phase. On the other hand, the dye which had not been subjected to the substitution treatment with the organic anion was kept in the aqueous phase when treated in a similar manner as set out above. This reveals that the substitution treatment contributes to drastic improvement of miscibility with organic solvents. Fabrication of thermal transfer ink ribbon Using the thus obtained hydrophobic cationic dye, a thermal transfer ink ribbon 10 shown in Fig. 1 was fabricated in the following manner. A 6 µm thick polyethylene terephthalate (PET) film which had a heat-resistant, lubricating layer 1 on the one side thereof was provided as a support 2. The support 2 was applied with 25 g/m 2 of a thermal transfer ink composition with the following formulation on a side opposite to the side of the heat-resistant lubricating layer 1 of the support 1 and dried. By this, there was obtained a thermal transfer ink ribbon 10, as shown in Fig. 1, which had the PET film support 2 and the ink layer 3 with a thickness of about 1 µm. Thermal transfer ink composition Hydrophobic cationic dye of the invention 1 part by weight Polyvinylbutyral 1 part by weight (6000-CS, made by Denki Chem. Ind. Co., Ltd.) Toluene 12 parts by weight Methyl ethyl ketone 12 parts by weight The thermal transfer ink ribbon obtained above was set in a ribbon cassette (not shown). A color video printer (commercial name: CVP-G500, made by Sony Co., Ltd.) was used for single color printing on a printing sheet whose image-receiving layer was made of a vinyl chloride-vinyl acetate copolymer resin (commercial name: UPC-3010, made by Sony Co., Ltd.), a printing sheet whose dye-receiving layer was made of a polyester resin (commercial name: VPM-30ST, made by Sony Co., Ltd.), and a printing sheet whose dye-receiving layer was made of a cellulose ester resin (commercial name: VPM-30STA, made by Sony Co., Ltd.) As a result, there was obtained an image with a good yellow color and good gradation properties. Fig. 2 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. The abscissa axis indicates a gradation (step) which shows an energy added for image printing in a stepwise manner. As shown in the figure, the ink ribbon fabricated in this example ensures gradation printing by the thermal transfer with respect to all the printing sheets. Example 2 - Preparation of dodecylbenzenesulfonate of C.I. Basic Yellow 28 In the same manner as in Example 1, 1 g of C.I. Basic Yellow 28 and 1 g of sodium dodecylbenzenesulfonate were reacted to obtain about 1.8 g of crystals of the captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing, test. As a result, there was obtained an image which assumed a good yellow color and good gradation properties. Fig. 3 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 3 - Preparation of laurylsulfate of C.I. Basic Yellow 28 In the same manner as in Example 1, 1 g of C.I. Basic Yellow 28 and 1 g of sodium laurylsulfate were reacted to obtain about 1.5 g of crystals of the captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test. As a result, there was obtained an image which assumed a good yellow color and good gradation properties. Fig. 4 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 4 - Preparation of laurylsulfate of C.I. Basic Yellow 51 In the same manner as in Example 1, 1 g of C.I. Basic Yellow 51 (commercial name: Diacryl Yellow 3G-N, made by Mitsubishi Chem. Hoechest Co., Ltd.) and 1 g of sodium dodecylbenzenesulfonate were reacted to obtain about 1.5 g of crystals of the captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, following by a similar printing test. As a result, there was obtained an image which assumed a good lemon yellow color and good gradation properties. Fig. 5 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 5 - Preparation of laurylsulfate of C.I. Basic Yellow 21 In the same manner as in Example 1, 1 g of C.I. Basic Yellow 21 (commercial name: Aizen Cathilon Yellow 7GLH, made by Hodogaya Chem. Inc. Co., Ltd.) and 1 g of sodium dodecylbenzenesulfonate were reacted to obtain about 1.6 g of crystals of the captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon followed by a similar printing test. As a result, there was obtained an image which assumed a good lemon yellow color and good gradation properties. Fig. 6 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 6 - Preparation of diethylhexylsulfosuccinate of C.I. Basic Yellow 36 In the same manner as in Example 1, 1 g of C.I. Basic Yellow 36 (commercial name: Aizen Cathilon Yellow K-3RLH, made by Hodogaya Chem. Inc. Co., Ltd.) and 1 g of sodium diethylhexylsuccinate were reacted to obtain about 1.8 g of a tar-like captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test. As a result, there was obtained in image which assumed a good yellow color and good gradation properties. Fig. 7 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 7 - Preparation of laurylsulfate of C.I. Basic Yellow 67 In the same manner as in Example 1, 1 g of C.I. Basic Yellow 67 (commercial name: Kayacryl Yellow 3RL, made by Nippon Kayaku K.K.) and 1 g of sodium laurylsulfate were reacted to obtain about 1.8 g of a tar-like captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test. As a result, there was obtained an image which assumed a good yellow color and good gradation properties. Fig. 8 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbons As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Exemple 8 - Preparation of laurylsulfate of C.I. Basic Yellow 73 In the same manner as in Example 1, 1 g of C.I. Basic Yellow 73 (commercial name: Aizen Cathilon Yellow CD-RLH, made by Hodogaya Chem. Ind. Co., Ltd.) and 1 g of sodium laurylsulfate were reacted to obtain about 1.8 g of a tar-like captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test. As a result, there was obtained an image which assumed a good yellow color and good gradation properties. Fig. 9 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 9 - Preparation of dodecylbenzenesulfonate of C.I. Basic Red 14 In the same manner as in Example 1, 1 g of C.I. Basic Red 14 (commercial name: Aizen Cathilon Red 4GH, made by Hodogaya Chem. Ind., Co., Ltd.) and 1 g of sodium dodecylbenzenesulfonate were reacted to obtain about 1.6 g of a dark reddish purple tar-like captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, following by a similar printing test. As a result, there was obtained an image which assumed a good red color and good gradation properties. Fig. 10 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 10 - Preparation of dietylhexylsulfosuccinate of C.I. Basic Red 13 In the same manner as in Example 1, 1 g of C.I. Basic Red 13 (commercial name: Aizen Cathilon Pink FGH, made by Hodogaya Chem. Ind., Co., Ltd.) and 1 g of sodium diethylhexylsuccinate were reacted to obtain about 1.8 g of a tar-like captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaked, whereupon the due mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test. As a result, there was obtained an image which assumed a good magenta color and good gradation properties. Fig. 11 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheet. Example 11 - Preparation of dodecylbenzenesulfonate of C.I. Basic Violet 7 In the same manner as in Example 1, 1 g of C.I. Basic Violet 7 (commercial name: Aizen Cathilon Red 6BH, made by Hodogaya Chem. Ind. Co., Ltd.) and 1 g of sodium dodecylbenzenesulfonate were reacted to obtain about 1.8 g of the captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution of the counter ion with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobia cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test. As a result, there was obtained an image which assumed a good magenta color and good gradation properties. Fig. 12 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 12 - Preparation of dietylhexylsulfosuccinate of C.I. Basic Blue 75 In the same manner as in Example 1, 1 g of C.I. Basic Blue 75 (commercial name: Kayacryl Light Blue 4GSL, made by Nippon Kayaku K.K.) and 1 g of sodium diethylhexylsuccinate were reacted to obtain about 1.6 of a dark bluish green, tar-like captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution with the organic anion contributes to drastically improving miscibility with the organic solvent. In the same manner as in Example 1, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test using a printing sheet (VMP-30STA) of Sony Co., Ltd. As a result, there was obtained an image which assumed a good cyan color and good gradation properties. Fig. 13 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 13 - Preparation of dodecylbenzenesulfonate of C.I. Basic Blue 3 In the same manner as in EXanple 1, 1 g of C.I. Basic Blue 3 (commercial name: Aizen Cathilon Pure Blue 5GH, made by Hodogaya Chem. Ind. Co., Ltd.) and 1 g of sodium dodecylbenzenesulfonate were reacted to obtain about 1/8 g of crystals of the captioned hydrophobic cationic dye. the hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution of the counter ion with the organic anion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 12, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test. As a result, there was obtained an image which assumed a good cyan color and good gradation properties. Fig. 13 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Example 14 - Preparation of laurylsulfate of C.I. Basic Blue 3 In the same manner as in Example 1, 1 g of C.I. Basic Blue 3 (commercial name: Aizen Cathilon Pure Blue 5GH, made by Hodogaya Chem. Ind. Co., Ltd.) and 1 g of sodium laurylsulfate were reacted to obtain about 1.8 g of crystals of the captioned hydrophobic cationic dye. The hydrophobic cationic dye was placed in a water-toluene phase and shaken, whereupon the dye mostly remained in the toluene phase. This reveals that the substitution of the counter ion contributes to drastically improved miscibility with the organic solvent. In the same manner as in Example 12, the resultant hydrophobic cationic dye was used to make a thermal transfer ink ribbon, followed by a similar printing test using a printing sheet (UPC-3010) of Sony Co., Ltd. As a result, there was obtained an image which assumed a good cyan color and good gradation properties. Fig. 13 shows a so-called dynamic sensitivity (color-development) characteristic of the ink ribbon. As shown in the figure, the ink ribbon obtained in this example ensures gradation printing by the thermal transfer on the printing sheets. Since the cationic dyes used according to the invention are hydrophobic in nature, they can be mixed with hydrophobic polymers satisfactorily and uniformly with good storage stability. Accordingly, when these hydrophobic cationic dyes and hydrophobic polymers are used to form an ink layer of a thermal transfer ink ribbon, the sensitivity at the time of the transfer and the color and light fastness of the resultant images can be improved.

Claims: Use of a hydrophobic cationic dye in an ink layer of a thermal transfer ink ribbon, said ink layer containing a hydrophobic polymer and said dye being obtainable by substituting, with an organic anion, a counter ion of a diazacarbocyanine cationic dye of the formula (1) wherein R1, R2, R3 and R4 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, and Z - represents a counter ion. A thermal transfer ink ribbon comprising a support and an ink layer formed on said support, wherein said ink layer comprises a hydrophobic cationic dye which is obtained by substituting, with an organic anion, a counter ion of a diazacarbocyanine cationic dye of the formula (1) wherein R1, R2, R3 and R4 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, and Z- represents a counter ion. Use of a hydrophobic cationic dye in an ink layer of a thermal transfer ink ribbon, said ink layer containing a hydrophobic polymer and said dye being obtainable by substituting a counter ion of a cationic dye of C.I. Basic Yellow 21, 36, 67 or 73 with an organic anion. A thermal transfer ink ribbon comprising a support and an ink layer formed theron, wherein said ink layer comprises a hydrophobic cationic dye which is obtained by substituting a counter ion of a cationic dye of C.I. Basic Yellow 21, 36, 67 or 73 with an organic anion. Use of a hydrophobic cationic dye in an ink layer of a thermal transfer ink ribbon, said ink layer containing a hydrophobic polymer and said dye being obtainable by substituting, with an organic anion, a counter ion of a hemicyanine cationic dye of the formula (2) wherein R21, R22, R23, R24 and R25 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, provided that R24 and R25 may join together to form a ring, and Z- represents a counter ion. A thermal transfer ink ribbon comprising a support and an ink layer formed on said support, wherein said ink layer comprises a hydrophobic cationic dye obtained by substituting, with an organic anion, a counter ion of a hemicyanine cationic dye of the formula (2) wherein R21, R22, R23, R24 and R25 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, provided that R24 and R25 may join together to form a ring, and Z - represents a counter ion. Use of a hydrophobic cationic dye in an ink layer of a thermal transfer ink ribbon, said ink layer containing a hydrophobic polymer and said dye being obtainable by substituting, with an organic anion, a counter ion of an oxazine cationic dye of the formula (3a) or (3b) wherein R31, R32, R33, R34, R35, R36, R37, R38, R39, R310, R311 and R312 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, provided that R31 and R32, R33 and R34, R37 and R38, R39 and R310, R310 and R311, and R311 and R312 may, respectively, join together to form a ring, and Z- represents a counter ion. A thermal transfer ink ribbon comprising a support and an ink layer formed on said support, wherein said ink layer comprises a hydrophobic cationic dye obtained by substituting, with an organic anion, a counter ion of an oxazine cationic dye of the formula (3a) or (3b) wherein R31, R32, R33, R34, R35, R36, R37, R38, R39, R310, R311 and R312 independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkoxy group, an alkenyl group, an alkenoxy group, an alkoxycarbonyl group, an acyloxy group, or an acyl group which may be substituted, provided that R31 and R32, R33 and R34, R37 and R38, R39 and R310, R310 and R311, and R311 and R312 may, respectively, join together to form a ring, and Z- represents a counter ion.

Inventors: HIDA MASANOBU, ISAJI KAORI, ITO KENGO, HIDA, MASANOBU, ISAJI, KAORI, ITO, KENGO
Applicants: SONY CORP, SONY CORPORATION
Application year: 1993
Main classification: C09B69
IPC codes: B41M5, C09B69