Coloring method by use of new yellow dyestuff and coloring transfer material for thermal transfer using this method

Abstract: A novel method is disclosed by which paper and fabric are colored yellow. This coloring method comprises the step of transferring, under heating conditions, 2-pyridone compounds represented by the general formula (1) wherein R¹ is a lower alkyl group, and R² is an alkyl group, alkoxyalkyl group, aralkyl group, cycloalkyl group, alkenyl group or lower alkoxycarbonylmethyl group.

Description: The present invention is utilized in a field in which surfaces of substances are colored, particularly in a field in which yellow patterns and images are printed on fabric and on paper. That is, the present invention relates to a yellow coloring material for thermal transfer represented by the general formula (1) wherein R¹ is a lower alkyl group, and R² is an alkyl group, alkoxyalkyl group, aralkyl group, cycloalkyl group, alkenyl group or lower alkoxycarbonylmethyl group. The present invention can be applied to the thermal transfer printing process of synthetic fibers and the transfer type thermal recording system which is a means of recording information, and it can provide various good color fastness effects such as color fastness against light and enables to give the sharp coloring of images by transfer. Heretofore, as yellow dyestuffs for transfer printing, there have been known styryl dyestuffs (reference literature: Japanese Patent Publication No. 5029/1979) represented by the formula (2) pyrazole dyestuffs (reference literature: Japanese Patent Laid-open Nos. 139869/1976 and 10778/1978) represented by the formulae (3) and (4) pyridone dyestuffs represented by the formula (5) (reference literature: Japanese Patent Laid-open No. 23782/1979) or by formula (5') (EP-A-0247737): wherein Z is C₁₋₁₂ alkyl or phenyl, R can be C₂₋₁₂ alkyl which can be interrupted by one or two groups selected from -O-, CO, OCO-, -COO-, α phenyl, C₁₋₄ alkylphenyl or biphenyl wherein the phenyl ring A may be 4-substituted, e.g. A being 4-(2-[2-methoxyethoxy]ethoxycarbonyl) and other dyestuffs. Furthermore, as the coloring materials for recording information, the utilization of Color Index Disperse Yellow 54 [formula (6)] has been suggested: Moreover, pyrazolone and pyrazole dyestuffs represented by the formulae (7) and (8) are also disclosed by inventors of the present application (Japanese Patent Laid-open Nos. 12393/1986 and 12394/1986): GB-A-2008606 discloses compounds of formula (9) for use as yellow dyes suitable for dyeing hydrophobic synthetic fibres, particularly polyesters. X may be alkoxy. R² may be CN. R¹ may be alkyl or alkoxyalkyl. When the yellow coloring material is used on synthetic fibers or record papers in a way of thermal transfer system, important requirements to evaluate its quality are various color fastness factors such as color fastness against light and color value. However, the color fastness factors and color value of the above-mentioned known coloring materials are still poor. In addition, the color tone of these coloring materials is also defective in sharpness. The present invention provides a thermal transfer printing colour sheet which is a carrier sheet having a coating of a 2-pyridone compound represented by the general formula (1) wherein R¹ is a C₁-C₄ alkyl, and R² is C₁-C₈ alkyl group, alkoxyalkyl group R³-O-(CH₂) n - where R³ is C₁-C₇ alkyl and n is 1-6, benzyl group, phenethyl group, C₃-C₈ cycloalkyl group, C₃ or C₄ alkenyl group or alkoxycarbonylmethyl group wherein alkoxy is C₁-C₄. In a second aspect it provides a thermal transfer printing method wherein such a color sheet is pressed against a printable substrate and heat is applied to effect thermal transfer of the 2-pyridone compound. Typical examples of R¹ in the general formula (1) include lower alkyl groups such as a methyl group, ethyl group, propyl group and butyl group. Typical examples of R² include alkyl groups such as a methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group and octyl group; alkoxyalkyl groups such as a methoxymethyl group, methoxyethyl group, methoxypropyl group, methoxybutyl group, methoxypentyl group, methoxyhexyl group, methoxyheptyl group, ethoxymethyl group, ethoxyethyl group, ethoxypropyl group, ethoxybutyl group, ethoxypentyl group, ethoxyhexyl group, propoxymethyl group, propoxyethyl group, propoxypropyl group, propoxybutyl group, propoxypentyl group, butoxymethyl group, butoxyethyl group, butoxypropyl group, butoxybutyl group, pentyloxymethyl group, pentyloxyethyl group, pentyloxypropyl group, hexyloxymethyl group, hexyloxyethyl group and heptyloxymethyl group; aralkyl groups such as a benzyl group and phenethyl group; cycloalkyl groups such as a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group and cyclooctyl group; and alkenyl groups such as an allyl group, 1-butenyl group, 2-butenyl group, 2-butenylene group and 2-methylallyl group. In addition, other examples of the R² group include lower alkoxycarbonylmethyl groups such as a methoxycarbonylmethyl group, ethoxycarbonylmethyl group, propoxycarbonylmethyl group and butoxycarbonylmethyl group. The compound represented by the general formula (1) may be prepared by the following process: In the first place, pyridone is synthesized from ethyl acetoacetate, ethyl cyanoacetate and an amine (general formula NH₂R²) by a known process shown by the following chemical equation: Afterward, the thus synthesized pyridone is diazo-coupled with para-aminobenzoic acid in a known method to obtain a base, and the latter is then reacted with mono-chloroacetic acid derivatives to prepare a compound having the general formula (1): The thus prepared compound is excellent in heat stability and transfer velocity which are required at the time of the use as a coloring material. This compound is sublimed when heated, so that it binds to a substance and colors the bound areas yellow. Procedures for the transfer coloring of synthetic fibers are described in, for example, French Patent No. 1223330 and German Patent Laid-open No. 1769757, and dyestuffs and additives used in the procedures may be disclosed in German Patent Laid-open Nos. 1771813 and 1771812, and they can be applied to the present invention. When the coloring method of the present invention is used in a thermal transfer type recording system for recording information, images can be transferred from a thermal transfer printing color sheet to a print paper by thermal head. The color sheet may be prepared, for example, by finely dispersing or dissolving the coloring material, and then coating a carrier sheet with the resultant dispersion or solution. Such a carrier sheet as used above may be a thin paper or plastic film which can withstand the thermal transfer. EXAMPLES In examples given below, parts and percent are based on weight. Example 1 A coloring composition was used which was composed of 10 parts of a dyestuff (colouring material) represented by the formula 5 parts of ethyl cellulose, 70 parts of ethyl alcohol, 20 parts of ethyl acetate and 5 parts of ethyl glycol, and printing was performed on a paper (carrier sheet) by the flexographic printing process, followed by drying to produce a thermal transfer printing colour sheet. The dried paper was then put on a polyester fabric so that the printed surface of the paper might be in contact directly with the fabric, and the fabric having the paper thereon was passed through a calender at 200°C for 30 seconds. As a result, the coloring material was transferred to the fabric, and a yellow print was obtained on white ground. The thus obtained print was then subjected to a light resistance test at a temperature of 63±2°C by the use of Xenon-fade Meter (made by Suga Shikenki Co., Ltd.), and it became apparent that the print scarcely discolored, which indicated that the print was excellent in light resistance. Additionally, the print was also good in image stability at high temperatures and high humidities. Example 2 A coloring composition was used which was composed of 5 parts of a dyestuff (colouring material) represented by the formula 20 parts of polymerized styrol and 80 parts of toluol, and this was printed onto a paper by the copper gravure printing process, followed by drying. Afterward, a print pattern of the dried paper was transferred to polyacrylonitrile fabric by the same procedure as in Example 1 at 190°C for 25 seconds, so that a yellow print was obtained on the white ground. For the thus obtained print, light resistance and image stability were tested in the same method as in Example 1, and it became apparent that the quality of the print was good as in Example 1. Example 3 A coloring composition was used which was composed of 21 parts of a dyestuff (colouring material) represented by the formula 318 parts of methyl ethyl ketone, 125 parts of toluene and 30 parts of ethylhydroxyethyl cellulose, and this was printed onto a paper by the rotary film printing process, followed by drying. Afterward, a print pattern of the dried paper was transferred to polyester fabric by the same procedure as in Example 1 at 210°C for 30 seconds, so that a yellow print was obtained on the white ground. For the thus obtained print, light resistance and image stability were tested in the same method as in Example 1, and it became apparent that the quality of the print was good as in Example 1. Example 4 A coloring composition was used which was composed of 10 parts of a dyestuff (colouring material) represented by the formula and 90 parts of a varnish comprising 40 parts of phenol-modified colophonium resin, 20 parts of vegetable drying oil, 10 parts of long oil alkyd resin, 25 parts of a mineral oil, 10 parts of an aerosil® and 2 parts of cobalt desiccant, and a suitable pattern was printed on a transfer paper (carrier sheet) by means of the offset printing process. The dried paper was put on polyacrylonitrile fabric so that the printed surface of the paper might be in contact directly with the fabric, and it was then treated on a leaf press at 25°C for 25 seconds. As a result, a yellow print having good color fastness against light and humidity was obtained on the white ground. For the thus obtained print, light resistance and image stability were tested in the same method as in Example 1, and it became apparent that the quality of the print was good as in Example 1. Example 5 A coloring composition was used which was composed of 21 parts of a dyestuff (colouring material) represented by the formula 318 parts of methyl ethyl ketone, 125 parts of toluene and 30 parts of ethylhydroxyethyl cellulose, and printing was made on a paper by the rotary film printing process, followed by drying. Afterward, a print pattern of the dried paper was transferred to polyester fabric by the same procedure as in Example 2 at 210°C for 20 seconds, so that a yellow print having good color fastness against humidity was obtained on the white ground. For the thus obtained print, light resistance and image stability were tested in the same method as in Example 1, and it became apparent that the quality of the print was good as in Example 1. Example 6 A coloring composition was used which was composed of 10 parts of a dyestuff (colouring material) represented by the formula and 90 parts of a varnish comprising 10 parts of ethyl cellulose, 75 parts of ethyl alcohol, 20 parts of ethyl acetate and 5 parts of ethylene glycol, and a suitable pattern was printed on a transfer paper by means of the intaglio printing process. The dried paper was put on polyester fabric so that the printed surface of the dried paper might be in contact directly with the fabric, and it was then passed through a calender at 200°C for 30 seconds. As a result, the color material was transferred to the polyester fabric, and a yellow print having good color fastness against light and humidity was obtained on the white ground. For the thus obtained print, light resistance and image stability were tested in the same method as in Example 1. The test results were good as in Example 1. Example 7 A pattern was printed on a paper by the use of the coloring composition prepared in Example 1, followed by drying, to obtain a ribbon. This ribbon was then passed between a paper coated with polyester and a heating element while the latter element was pressed against the ribbon, so that the coloring material was transferred to the coated paper, thereby reproducing sharp characters and images on the coating paper. For the thus obtained transfer-printed paper, light resistance and image stability were tested in the same method as in Example 1. The test results were good as in Example 1. Examples 8 to 26 By the use of various compounds shown in Table 1, yellow prints were obtained in the same method as in Example 1. For the obtained prints, light resistance test was carried out by the same procedure as in Example 1, and it became apparent that the prints scarcely changed, which indicated that they were excellent in image stability at high temperature and high humidities. The evaluation of the light resistance is also shown in Table 1. Substituents in General Formula (1) Light Resistance R¹ R² Example 8 C₂H₅- CH₃- Excellent Example 9 CH₃- C₃H₇- " Example 10 C₃H₇- C₄H₉- " Example 11 C₄H₉- C₈H₁₇- " Example 12 C₄H₉- C₂H₅OC₂H₄- " Example 13 C₂H₅- C₂H₅OC₆H₁₂- " Example 14 C₃H₇- C₃H₇OCH₂- " Example 15 CH₃- C₃H₇OC₄H₈- " Example 16 C₂H₅- C₄H₉OC₂H₄- " Example 17 C₄H₉- C₄H₉OC₄H₈- " Example 18 C₂H₅- C₅H₁₁OCH₂- " Example 19 CH₃- C₅H₁₁OC₃H₆- " Example 20 C₂H₅- C₆H₁₃OC₂H₄- " Example 21 CH₃- C₇H₁₅OCH₂- " Example 22 C₄H₉- C₃H₅- " Example 23 C₂H₅- C₅H₉- " Example 24 CH₃- C₈H₁₅- " Example 25 C₂H₅- CH₂=CHCH₂- " Example 26 C₃H₇- CH₃CH₂CH=CH- "

Claims: A thermal transfer printing method in which images are transferred from a colour sheet which is a carrier sheet having a coating of a 2-pyridone compound represented by the general formula (1) wherein R¹ is a C₁-C₄ alkyl, and R² is C₁-C₈ alkyl group, alkoxyalkyl group R³-O-(CH₂) n - where R³ is C₁-C₇ alkyl and n is 1-6, benzyl group, phenethyl group, C₃-C₈ cycloalkyl group, C₃ or C₄ alkenyl group or alkoxycarbonylmethyl group wherein alkoxy is C₁-C₄; wherein the colour sheet is pressed against a printable substrate and heat is applied to effect thermal transfer of the 2-pyridone compound. A method according to claim 1 wherein the printable substrate comprises fabric or paper. A method according to claim 1 wherein the printable substrate is polyester-coated paper. A method according to any preceding claim wherein the carrier sheet is paper. A method according to any preceding claim wherein the coating is applied to the carrier sheet as a dispersion or solution which is then dried. A method according to any preceding claim wherein the coating is applied to the carrier sheet as a pattern by a printing process selected from flexographic, copper gravure, rotary film, offset, and intaglio printing processes; and the method effects transfer of the pattern to the printable substrate. A thermal transfer printing colour sheet which is a carrier sheet having a coating of a 2-pyridone compound represented by the general formula (1) wherein R¹ is a C₁-C₄ alkyl, and R² is C₁-C₈ alkyl group, alkoxyalkyl group R³-O-(CH₂) n - where R³ is C₁-C₇ alkyl and n is 1-6, benzyl group, phenethyl group, C₃-C₈ cycloalkyl group, C₃ or C₄ alkenyl group or alkoxycarbonylmethyl group wherein alkoxy is C₁-C₄. A sheet according to claim 7 wherein the carrier sheet is paper.

Inventors: IGATA AKITOSI, MIKODA TAMIO, IGATA, AKITOSI, MIKODA, TAMIO
Applicants: MITSUI TOATSU CHEMICALS, MITSUI TOATSU CHEMICALS, INC.
Application year: 1988
Main classification: B41M5
IPC codes: B41M5, C07D213, C09B29, D06P5