JPH04211477A - Heat-sensitive transfer sheet and ink composition therefor - Google Patents

Abstract

PURPOSE:To provide the title sheet capable of giving densely yellow-colored recorded products of high light resistance in high speed without putting large burden on thermal head, with a binder and a specific pyridone azo-dye-contg. coloring material layer on a substrate. CONSTITUTION:The objective sheet with (A) a binder consisting of cellulose- or acrylic acid-based resin, PS or polyester, etc., pref. 100 deg.C or higher in the softening point and/or heat distortion temperature and (B) a coloring material layer containing a pyridone azo dye of formula I on a substrate. Said dyer can be prepared, for example, by diazotizing m-fluoroaniline followed by coupling the resulting product to pyridones of formula II.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet used for thermal transfer recording, particularly for sublimation type thermal transfer recording, and an ink composition for a thermal transfer sheet.

0002

2. Description of the Related Art Conventionally, color recording techniques using electrophotography, inkjet, thermal transfer, and the like have been studied for use in facsimile machines, copying machines, printers, and the like. Among them, the thermal transfer recording method is considered to be advantageous compared to other methods because the device is easy to maintain and operate, and the device and consumables are inexpensive.

Thermal transfer methods include a melting method in which a transfer sheet with a heat-melting ink layer formed on a base film is heated by a thermal head to melt the ink and transfer it onto an image receptor; A transfer sheet on which a color material layer containing a sublimable dye is formed on a base film is heated by a thermal head, and the dye is transferred from the transfer sheet to an image receptor by sublimation and/or thermal diffusion, and transferred onto the image receptor. There is a sublimation method for recording, but the sublimation method can control the amount of dye transfer by changing the energy given to the thermal head, making it easier to record gradations, and it is especially effective for full-color recording compared to the melting method. It's advantageous.

[0004] In sublimation type thermal transfer recording, the sublimable dye used in the transfer sheet and the ink composition for the transfer sheet has a great effect on the speed of transfer recording, the image quality of the recorded material, and the storage stability, so it is extremely important. is important to
It is necessary to satisfy the following conditions.

[0005] Easily sublimated and/or thermally diffused under the operating conditions of the thermal recording head. ■ Do not thermally decompose under the operating conditions of the thermal recording head. ■ Must have a favorable hue in terms of color reproduction. ■ Has a large molecular extinction coefficient. ■ Stable against heat, light, moisture, chemicals, etc. ■ Easy to synthesize. ■ Excellent ink suitability. ■ No health and safety problems.

A dye satisfying all of the above conditions has not yet been found, and yellow dyes in particular have various drawbacks and have not yet been found to be satisfactory. As a yellow dye, it has been reported in JP-A No. 61-244595 and JP-A-61-244595 that a pyridone-based monoazo dye, which has the same basic skeleton as the dye used in the present invention, is excellent as a dye for sublimation type thermal transfer recording. This method is disclosed in Japanese Patent Application Laid-open No. 60-27594 and Japanese Patent Application Laid-open No. 62-290583. However, the dyes specifically shown in the structural formulas therein do not yet have sufficient performance. Therefore, the inventors conducted a more detailed study on pyridone-based azo dyes, and found that
The present invention was achieved by discovering that by introducing a fluorine atom into the meta-position of the benzene ring bonded to the azo group, particularly better performance in sensitivity and light resistance than conventional products can be achieved.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal transfer sheet and an ink composition for a thermal transfer sheet, which are characterized by using a yellow dye that satisfies all of the above conditions.

[0008]

[Means for Solving the Problems] The present invention is characterized in that it has a coloring material layer on a base material containing a binder and a pyridone azo dye represented by the general formula (I) according to claim 1. The gist thereof is a thermal transfer sheet, and an ink composition for the thermal transfer sheet containing a pyridone azo dye represented by the general formula (I), a resin as a binder, and an organic solvent and/or water. .

The present invention will be explained in detail below. The pyridone azo dye represented by the general formula (I) used in the present invention can be produced according to a conventionally known method. For example, by diazotizing m-fluoroaniline by a conventional method,

0010

[Case 2]

It can be obtained by coupling to a pyridone represented by the formula (wherein R has the same meaning as in general formula (I)) by a conventional method. To specifically explain the dye represented by the general formula (I) used in the present invention, in the formula, the unsubstituted alkyl group represented by R is a C2 to C8 linear or branched alkyl group. Examples of substituted alkyl groups include alkyl groups, and examples of substituted alkyl groups include carbon atoms with 1
~8 linear or branched alkyl groups are substituted with other groups, specifically 2-hydroxyethyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 2-hydroxy Hydroxy-substituted alkyl groups such as propyl group; Carboxy-substituted alkyl groups such as carboxymethyl group, 2-carboxyethyl group, and 3-carboxypropyl group; Cyano-substituted alkyl groups such as 2-cyanoethyl group and cyanomethyl group; 2-aminoethyl group Amino-substituted alkyl groups such as; halogen-substituted alkyl groups such as 2-chloroethyl group, 3-chloropropyl group, 2-chloropropyl group, 2,2,2-trifluoroethyl group; benzyl group, p-chlorobenzyl group , phenyl-substituted alkyl group optionally having a halogen atom such as 2-phenylethyl group; 2-methoxyethyl group, 2-ethoxyethyl group, 2-(n) propoxyethyl group, 2-(iso)propoxyethyl group group, 2-(n)butoxyethyl group, 2-
(iso) Alkoxy-substituted alkyl groups such as butoxyethyl group, 2-(2-ethylhexyloxy)ethyl group, 3-methoxypropyl group, 4-methoxybutyl group, 2-methoxypropyl group; 2-(2-methoxyethoxy) Ethyl group, 2-(2-ethoxyethoxy)ethyl group, 2-(
2-(n)propoxyethoxy)ethyl group, 2-(2-
(iso)propoxyethoxy)ethyl group, 2-(2-
(n) Butoxyethoxy)ethyl group, 2-(2-(is
o) Alkoxyalkoxy-substituted alkyl groups such as butoxyethoxy)ethyl group and 2-{2-(2-ethylhexyloxy)ethoxy}ethyl group; alkenyloxyalkyl groups such as allyloxyethyl group; aryl such as 2-phenoxyethyl group Oxyalkyl group; Substituted alkyl group such as aralkyloxyalkyl group such as 2-benzyloxyethyl group: 2-acetyloxyethyl group, 2-propionyloxyethyl group, 2-(n)butyryloxyethyl group, 2-( iso) butyryloxyethyl group, acyloxy-substituted alkyl group optionally substituted with a halogen atom such as 2-trifluoroacetyloxyethyl group; methoxycarbonylmethyl group, ethoxycarbonylmethyl group,
(n) propoxycarbonylmethyl group, (iso) propoxycarbonylmethyl group, (n) butoxycarbonylmethyl group, (iso) butoxycarbonylmethyl group, 2
-Ethylhexyloxycarbonylmethyl group, benzyloxycarbonylmethyl group, furfuryloxycarbonylmethyl group, tetrahydrofurfuryloxycarbonylmethyl group, 2-methoxycarbonylethyl group, 2-ethoxycarbonylethyl group, 2-(n) propoxycarbonylethyl group group, 2-(iso)propoxycarbonylethyl group, 2-(n)butoxycarbonylethyl group, 2-
Substituted or unsubstituted alkoxycarbonyl-substituted alkyl groups such as (iso)butoxycarbonylethyl group, 2-(2-ethylhexyloxycarbonyl)ethyl group, 2-benzyloxycarbonylethyl group, 2-furfurylcarbonylethyl group; 2- Methoxycarbonyloxyethyl group, 2-ethoxycarbonyloxyethyl group, 2-
(n) Propoxycarbonyloxyethyl group, 2-(i
so) propoxycarbonyloxyethyl group, 2-(n
) butoxycarbonyloxyethyl group, 2-(iso)
Substituted or unsubstituted alkoxycarbonyloxy-substituted alkyl groups such as butoxycarbonyloxyethyl group, 2-(2-ethylhexyloxycarbonyloxy)ethyl group, 2-benzyloxycarbonyloxyethyl group, 2-furfuryloxycarbonyloxyethyl group, etc. ; Examples include heterocyclic-substituted alkyl groups such as furfuryl group and tetrahydrofurfuryl group.

[0012] Examples of the cycloalkyl group represented by R include a cyclopentyl group and a cyclohexyl group. Furthermore, the substituted phenyl group represented by R includes one having a C1 to C8 linear or branched alkyl group as a substituent, and a C1 to C4 linear or branched alkoxy group. Examples include those having a halogen atom such as a fluorine atom, a chlorine atom, and a bromine atom, and those having a nitro group, a cyano group, and a trifluoromethyl group.

Among the groups represented by R, particularly advantageous are C2-C8 linear or branched alkyl groups, C3-C8 alkoxyalkyl groups, benzyl groups, 2-phenylethyl groups, Examples include an allyl group and a C4-C10 dialkylaminoalkyl group. Specific examples of the pyridone azo dye used in the present invention include those in which the group represented by R in the general formula (I) is shown in Table 1 below.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

When forming a coloring material layer containing the above-mentioned dye in the heat-sensitive transfer sheet of the present invention, the method is not particularly limited, and the dye is usually dissolved in a medium or formed into fine particles together with a binder. An ink is prepared by dispersing the ink, and the ink is applied onto a substrate and dried to form a coloring material layer on the substrate. As a binder for ink preparation,
In order to prevent heat fusion with the image receptor during transfer recording, a material with good heat resistance is used, and in particular, a material with a softening point and/or heat distortion temperature of 100° C. or higher is preferred.

Specifically, cellulose-based, acrylic acid-based,
Examples include water-soluble resins such as starch, acrylic resins, methacrylic resins, polystyrene, polycarbonate, polysulfone, AS resin, polyethersulfone, polyvinyl butyral, polyester, ethyl cellulose, acetyl cellulose, and other organic solvents or water-soluble resins. I can do it. These resins may be selected as appropriate depending on the solvent used as a medium for preparing the ink, and any resin that can be dissolved or uniformly dispersed in the solvent may be used.

The amount of these resins used is 1 to 40% by weight, preferably 5 to 3% by weight based on the total weight of the ink composition.
A range of 0% by weight may be mentioned. In addition to water, media for preparing ink include alcohols such as methyl alcohol, isopropyl alcohol, and isobutyl alcohol,
Cellosolves such as methyl cellosolve and ethyl cellosolve, aromatics such as toluene, xylene and chlorobenzene, esters such as ethyl acetate and butyl acetate, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, methylene chloride, chloroform, Chlorinated solvents such as trichlorethylene, ethers such as tetrahydrofuran and dioxane, N,N-
Organic solvents such as dimethylformamide and N-methylpyrrolidone may be used, and these may be used alone or in combination.

[0021] In addition to the above-mentioned components, the above-mentioned ink contains organic or inorganic non-sublimable fine particles, a dispersant, an antistatic agent, an antiblocking agent, an antifoaming agent, an antioxidant, and a viscosity modifier as required. , a mold release agent, etc. can be added. The base materials for applying ink for making transfer sheets include condenser paper, thin paper such as glassine paper, polyester,
Plastic films with good heat resistance such as polycarbonate, polyamide, polyimide, and polyaramid are suitable, and their thicknesses can range from 1 to 50 μm.

Among the above-mentioned base materials, polyethylene terephthalate film is particularly advantageous in view of mechanical strength, solvent resistance, economic efficiency, and the like. However, in some cases, polyethylene terephthalate film does not necessarily have sufficient heat resistance, and the running properties of the thermal head are insufficient. By providing a layer of synthetic resin, it is possible to use a thermal head with improved running performance.

[0023] Methods for applying ink to the base film include reverse roll coater, gravure coater,
It can be carried out using a rod coater, an air doctor coater, etc., and the thickness of the ink coated layer is 0.5 mm after drying.
It is sufficient to apply the coating to a thickness of 1 to 5 μm (Coating Method, written by Yuji Harasaki, published by Maki Shoten in 1979). On the other hand, an ink composition for a thermal transfer sheet, which is another object of the present invention, contains a pyridone azo dye represented by the general formula (I), a resin as a binder, and an organic solvent and/or water. It is something that

The details of the pyridone azo dye are as described above. Further, the binder is specifically selected from among the above-mentioned water-soluble or organic solvent-soluble resins, depending on the solvent. Among the above-mentioned resins, those having a heat distortion temperature and/or softening point of 100° C. or higher are particularly preferred. As the organic solvent, the above-mentioned solvents are used. Also,
In addition to the above-mentioned non-sublimable fine particles, dispersants, antistatic agents, antiblocking agents, antifoaming agents, antioxidants, viscosity modifiers,
Additives such as a mold release agent may also be used.

Further, in the ink composition of the present invention, the amount of the dye of general formula (I) used is 1 to 30% by weight, preferably 3 to 20% by weight, based on the total weight of the ink. The method for preparing the ink composition of the present invention is to place a mixed solution consisting of a pigment, a solvent, and a resin in a suitable container equipped with a stirrer, heat it as necessary, or add additives, etc., to prepare the pigment. The pigment can be adjusted by dissolving it in a solvent, or by using a paint conditioner, ball mill, sand grind mill, etc., to uniformly disperse the pigment in the solvent by adding additives as necessary.

[0026]

Effects of the Invention Since the pyridone azo dye represented by the general formula (I) used in the thermal transfer sheet of the present invention has a vivid yellow color, color reproducibility can be improved by combining appropriate cyan and magenta colors. It is suitable for obtaining good full-color recordings, and because it is easily sublimated and/or thermally diffused and has a large molecular extinction coefficient, it is possible to obtain high-speed recordings with high color density without placing a large burden on the thermal head. can. Furthermore, since it is stable against heat, light, moisture, chemicals, etc., it does not undergo thermal decomposition during transfer recording, and the resulting recording has excellent storage stability, particularly in terms of light resistance. In addition, since the pigment has good solubility in organic solvents and dispersibility in water, it is easy to prepare a highly concentrated ink in which the pigment is uniformly dissolved or dispersed. It is possible to obtain a heat-sensitive transfer sheet coated uniformly and with high concentration. Therefore, by using these heat-sensitive transfer sheets, recording with good uniformity and color density can be obtained.

Furthermore, the heat-sensitive transfer sheet of the present invention can utilize not only a thermal head but also infrared rays, laser light, etc. as a heating means. Further, the ink composition of the present invention can be coated on a current-carrying film that generates heat when energized, and used as a current-carrying thermal transfer sheet.

[0028]

[Examples] The present invention will be specifically explained below with reference to Examples, but these Examples are not intended to limit the present invention. Example 1 a) Preparation of ink R in the general formula (I) is -C6H13(n) 5g
Pyridone azo dye (dye No. 4 in Table 1 above)
Polysulfone resin*

10g chlorobenzene

100g total

115g
*Product name: Udel P-1700 (product of Nissan Chemical Industries, Ltd.) Heat distortion temperature
(ASTMD-648) A mixture having the above composition was treated with a paint conditioner at 175° C. for 10 minutes to prepare an ink.

b) Preparation of transfer sheet The above ink was applied to a polyethylene terephthalate film (6 μm
(thickness) and dried (dry film thickness approximately 1 μm) to obtain a transfer sheet. The heat-resistant and slippery treatment for polyethylene terephthalate film is performed using the following formula.

[0030]

[Chemical formula 3]

8 parts by weight of polycarbonate resin having the repeating structural unit shown below, 1 part by weight of phosphate ester surfactant (trade name: Plysurf A-208B: No. 1
This was done by applying a solution consisting of 91 parts by weight of toluene (product of Kogyo Seiyaku Co., Ltd.) and drying (dry film thickness approximately 0.5 μm).

c) Preparation of image receptor 10 parts of saturated polyester resin (product name: TP-220, product of Nippon Gosei Co., Ltd.), 0.5 part of amino-modified silicone (product name: KF393, product of Shin-Etsu Chemical Co., Ltd.), A liquid consisting of 15 parts of methyl ethyl ketone and 15 parts of xylene was applied to synthetic paper (product name: Yupo FPG150, manufactured by Oji Yuka Co., Ltd.) using a wire bar and dried (dry film thickness was approximately 5
μm) and further heat-treated at 100° C. for 30 minutes in an oven to prepare an image receptor.

d) Transfer Recording The ink coated surface of the above transfer sheet was overlapped with the recording medium and recording was performed using a thermal head under the following conditions, and a clear yellow record with uniform color density as shown in Table 2 could be obtained. Ta. Recording conditions Main scanning and sub-scanning density: 8 dots/mm Recording power: 0
．． 25W/Heating time of dot head: 10msec Color density was measured using Densitometer TR manufactured by Macbeth Co., Ltd.
Measurements were made using Model -927.

A light resistance test of the obtained record was carried out using a carbon arc fade meter (manufactured by Suga Test Instruments Co., Ltd.) (black panel temperature 63±2°C).
The degree of discoloration after time irradiation is shown in Table 2 below as a ΔE* value. Furthermore, the transfer sheet and the recorded matter were stable against heat and moisture, and had excellent storage stability in the dark. The dye used in this example was prepared by diazotizing m-fluoroaniline using a conventional method and then producing N-(n-hexyl)-3-cyano-
It was synthesized by coupling with 4-methyl-6-hydroxy-2-pyridone, the maximum absorption wavelength in acetone is as shown in Table 2 below, and the melting point is 156.9-158.8°C. Met.

Examples 2 to 10 Ink preparation, transfer sheet production, and transfer recording were carried out in the same manner as in Example 1 using the dyes shown in Table 2 below instead of the dyes used in Example 1. As a result, Clear yellow records with the color densities shown in Table 2 could be obtained, and the light resistance was also good as shown in Table 2.

Comparative Examples 1 to 4 The following general formula (III) was used instead of the dye used in Example 1.
Using each of the dyes whose substituents are as shown in Table 3 below, ink preparation, transfer sheet production, transfer recording, and light resistance testing were carried out in the same manner as in Example 1, and the results are shown in Table 2 below. I got it.

[0037]

[C4]

[0038]

[Table 5]

[0039]

[Table 6]

Example 11 A transfer sheet was prepared and transfer recording was performed in the same manner as in Example 1, using ink prepared by the following method instead of the ink used in Example 1. As a result, a bright yellow color was obtained. It was possible to obtain a record of uniform color density. Further, the results of the light fastness test of the obtained recording and the dark storage stability test of the transfer sheet and the recording were both good.

Preparation of ink Same pigment as Example 1

5g (Table 1 No. 4 pigment)

Claims (2)

[Claims] [Claim 1] A binder and the following general formula (I) [
A color containing a pyridone azo dye represented by the following formula: (wherein R represents a hydrogen atom, an alkyl group having 2 or more carbon atoms, a substituted alkyl group, a cycloalkyl group, an allyl group, or a substituted or unsubstituted phenyl group) A heat-sensitive transfer sheet characterized by having a material layer. 2. An ink composition for a thermal transfer sheet, comprising a pyridone azo dye represented by the general formula (I) according to claim 1, a resin as a binder, and an organic solvent and/or water.