JPH0473388B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to a thermal transfer recording sheet capable of gradation recording in a thermal transfer system using a thermal head. (B) Conventional technology Traditionally, thermal transfer systems include a thermal sublimation transfer method, in which an ink layer containing a heat sublimable dye is formed on a support, and the dye is sublimated onto the image receiving paper side for recording by heating; Forming a heat-melting ink layer containing colored dyes and pigments on the body (hereinafter referred to as donor sheet)
A heat-fusion transfer method is known in which recording is performed by melt-transferring to the image-receiving paper side by heating. Since the thermal sublimation transfer method uses dye as a gas to perform transfer recording, the gradation of the image is good and it is seen as a promising full-color recording method, and inventions have been made to improve the dye-dyeability of the image-receiving paper for this system. ing. (Unexamined Japanese Patent Publication No. 1983-
91296, JP 57-107885, JP 57-137191,
(JP-A-59-59495, JP-A-59-64393) However, the thermal sublimation transfer method requires a long heating time due to the high sublimation temperature of the dye, and has the disadvantage that the recording speed is slow. It is also possible to use a dye with a low sublimation temperature, but the re-sublimation of the dye results in poor image storage stability, and furthermore, because it is a dye, the image's light resistance is also poor. For these reasons, various methods of producing gradation using a thermal melt transfer method, which has a high recording speed and good image storage stability, have recently been studied. For example, in JP-A-57-56295, a heat-fusible ink layer (A) is provided on a support, and on the ink layer (A), dots are arranged at intervals from each other. ) is provided with a large number of spot-shaped heat-fusible ink layers (B) with a lower melting point than the ink layer (B), and the amount of ink transferred is changed by heating to produce intermediate tones. In addition, Japanese Patent Application Laid-Open No. 59-64391 discloses that on a support,
An image-forming substance formed by coating a layer containing an image-forming substance capable of forming an image by heating, and an image-receiving layer capable of receiving the image-forming substance and transferring it to a transfer medium by heating. The amount of thermal transfer to the image receiving paper side is controlled. (C) Problems to be solved by the invention The patent publications cited in the prior art mentioned above have various problems. For example, JP-A-57-56295 and JP-A-59-64391 both attempt to produce gradation by devising the layer structure of the ink applied to the support. That is,
The disadvantage is that the donor sheet must be completed by two coatings, and the manufacturing cost is also high. In addition, conventional single-layer donor sheets contain colored dyes and pigments,
A hot-melt ink containing a binder, waxes, and other additives is applied to a support by the gravure method or flexible method. The density of the coating layer is high and the conductivity of the heat given by the thermal head is good, and the ink layer that corresponds to the shape of the thermal head is almost completely dissolved. When thermal transfer printing is performed on coated paper, even if the printing machine has 16 or so gradations, density gradations cannot be obtained, and the image is recorded as a very sharp ON-OFF binary value. . Therefore, in this industry, donor sheets with different transfer densities are used to perform multiple overprinting to create density gradations, and at the same time, area gradation methods are also used to control the number of halftone dots in the printed matrix. I am trying to obtain a high-gradation image using a complicated method. This also increases the manufacturing cost of the donor sheet, and
The disadvantage is that the printing speed is also slow. The present inventors conducted research aimed at solving these drawbacks and obtaining a thermal transfer recording sheet capable of gradation recording. (D) Means for Solving the Problems The present inventors conducted intensive research to solve these drawbacks, and as a result, they were able to provide a gradation thermal transfer recording sheet. That is, in a thermal transfer recording sheet in which a heat-melt ink layer containing colored dyes and pigments, binders, and waxes as main components is coated on one side of a support, the heat-melt ink contains gallic acid or a derivative thereof. By doing so, it was possible to provide a thermal transfer recording sheet capable of gradation recording. Specifically, the gallic acid or its derivatives include gallic acid, methyl gallate, ethyl gallate, propyl gallate, isoamyl gallate, octyl gallate, lauryl gallate, stearyl gallate, trimethoxy gallic acid, and trimethoxy gallate. It consists of at least one selected from gallic acid methyl ester, gallic acid 3-methyl ether, gallic acid 4-methyl ether, gallic acid 3,4-dimethyl ether, and gallic acid 3,5-dimethyl ether. More preferably, the gallic acid derivative consists of at least one gallic acid alkyl ester selected from methyl gallate, ethyl gallate, propyl gallate, isoamyl gallate, octyl gallate, lauryl gallate, and stearyl gallate. It is. The heat-melt ink of the present invention contains gallic acid or a derivative thereof in an amount of 5 to 50% per total weight of the heat-melt ink as a component of colored dyes and pigments, binders, and waxes.
By containing it in a weight percent, gradation recording can be obtained. Preferably it is 10 to 30 weight percent. The gradation thermal transfer recording sheet of the present invention can produce images with high density gradation simply by coating a support in a single layer. Rather than coating with a single color,
Images with color gradation can also be obtained by forming a thermal transfer recording sheet in which a heat-melting ink consisting of dyes and pigments of at least yellow magenta and cyan is partially coated on a support. The reason why the thermal transfer recording sheet of the present invention has density gradation is not very clear, but when the only component that provides the transfer effect of heat-melting ink in a normal thermal transfer recording sheet is wax, the ink is applied from the thermal head. While complete transfer to the image receiving paper occurs at a certain level of energy, the mixture of gallic acid or its derivatives of the present invention has a high melting point and suppresses the amount of transfer at low energy, gradually increasing in proportion to the increase in energy. It is thought that density gradation appears as the amount of transfer increases. Furthermore, when the components of the present invention are mixed, when the heat-melting ink layer on the thermal transfer recording sheet is enlarged, the ink is arranged in the form of particles on the support, and the particles change depending on the energy of the thermal head. It is thought that there is a tendency for density gradation to appear even more easily as the ink is independently transferred to the image receiving paper surface. Furthermore, the types, amounts, and melting points of binders, waxes, dyes and pigments, which are the main components of the heat-melting ink, are also thought to have a subtle influence. For example, waxes with a melting point of 50°C to 200°C, preferably 60°C to 150°C, are good, and if the melting point is lower than 50°C, the form in the ink layer may be particulate. However, during thermal transfer, it is difficult to obtain density gradation because the sensitivity is too high. Conversely, if the melting point is higher than 200℃, high energy is required for the thermal head and the amount of thermal transfer is reduced.
Not practical. Typical examples of such waxes are listed below, but the waxes are not limited thereto. Examples of waxes include plant-based waxes such as rice wax, Japanese wax, candelilla wax, and carnauba wax; animal-based waxes such as lanolin, beeswax, and serratus wax; and mineral-based waxes such as montan wax. Synthetic waxes include paraffin wax, microcrystalline wax, oxidized paraffin wax, chlorinated paraffin wax, ricinoleic acid amide, lauric acid amide, erucic acid amide, valmitic acid amide, oleic acid amide, and 12-hydroxystearic acid. , distearyl ketone, ethylene bisstearamide, etc. Metallic soaps include sodium stearate, sodium palmitate, potassium laurate, potassium myristate, calcium stearate, zinc stearate, aluminum stearate, magnesium stearate, stearic acid. Lead, dibasic barium stearate, etc. Higher fatty acids include palmitic acid, stearic acid, etc. Higher alcohols include palmityl alcohol, stearyl alcohol, ceryl alcohol, etc. Synthetic polyalcohols include polyethylene glycol, polypropylene glycol, etc. Equals, etc. can be mentioned. Next, as dyes and pigments, any of water-soluble dyes, oil-soluble dyes and pigments, disperse dyes, and solvent-insoluble organic pigments can be used, and they are not directly related to the quality of gradation. Each of the above types of dyes and pigments can be used depending on the coating method. In particular, water-soluble dyes are preferably used for water-based coating and solvent coating. Further, for those that dissolve in organic solvents, solvent coating is preferred, and in the case of hot melt coating, either dissolution or dispersion may be used. It is better to make the dye and pigment into fine particles with a particle size of about 1 μm or less, so that the transferred image does not have roughness. Although there are sublimation dyes, the dyes of the present invention cannot fully exhibit their sublimation function. However, as long as it is used as a coloring material, it does not impede the present invention and may be used without any problem. Specific examples of dyes and pigments are given below,
It is not limited to these, and two or more types may be used in combination. Water-soluble dyes include nitroso dyes, azo dyes (mono, bis, tris, and tetrakisazo dyes), stilbene azo dyes,
Ketoimine (diphenylmethane) dyes, triphenylmethane dyes, xanthene dyes, acridine dyes, quinoline dyes, methine dyes, polymethine dyes, thiazole dyes, indamine dyes, azine dyes, thiazine dyes, oxyketone dyes, anthraquinone dyes, phthalocyanine dyes, etc. I can do it. To give a more specific example, Mordant Green 4 (C.
I.10005, CI No. is shown in the cut below), Direct Red 28 (22120) as an azo dye, Direct Orange 71 as a stilbene azo dye
(40205), Ketoimine dye is Basic Yellow 2 (41000), triphenylmethane dye is Basic Blue 1 (42025), xanthene dye is Acid Dred 52 (45100), acridine dye is Basic Orange 23 (46075), Quinoline dyes include acid yellow 2 (47010),
Direct Yellow 59 as a methine dye
(49000), acid blue 59 as an azine dye
(50315), an oxazine dye such as Modern Blue 10 (51030), a thiazine dye such as Basic Blue 9 (52015), an anthraquinone dye such as Acid Blue 45 (63010), and a phthalocyanine dye such as Direct Blue 86 (74180). be. Examples of oil-soluble dyes include azo dyes, azo metal complex dyes, anthraquinone dyes, and phthalocyanine dyes. To give a more specific example, the azo dye is Solvent Yellow 2.
(CI11020, below the cut indicates CI No.), Solvent Orange 1 (11920), Solvent Red 24
(26105), Solvent Brown 3 (11360), etc.
As an azo metal complex dye, Solvent Yellow 19
(13900A), Solvent Orange 5 (18745A), Solvent Red 8 (12715), Solvent Brown
37 and Solvent Black 123 (12195), anthraquinone dyes such as Solvent Violet 13 (60725), Solvent Blue 11 (61525), and Solvent Green 3 (61565), and phthalocyanine dyes such as Solvent Blue 25 (74350). and so on. Examples of disperse dyes include aminoazo or aminoanthraquinone dyes, nitroarylamine dyes, and the like. To give a more specific example, the aminoazo dye is Disperse Yellow 3.
(CI11855, below the cut indicates CI No.), Disperse Orange 3 (11005), Disperse Red 1 (11110), Disperse Violet 24
(11200), Daspers Blue 44, etc. Aminoanthraquinone dyes include Disperse Orange 11 (60700) and Disperse Red 4.
(60755), Disperse Violet 1 (61100),
Examples include Disperse Blue 3 (61505). Examples of nitroarylamine dyes include Disperse Yellow 1 (10345) and 42 (10338). Pigments include azo pigments (monoazo, bisazo, condensed azo pigments), dyeing lake pigments (acid dye lake, basic dye lake, mordant dye lake pigments), nitro pigments,
Nitroso pigments, phthalocyanine pigments, high-grade pigments (vat dye pigments, metal complex pigments, perylene pigments,
Examples include isoindolinone pigments and quinacridone pigments). To give a more specific example, the azo pigment is Banza Yellow G (C.
I.11680, CI No. is shown below), Hansa Yellow R (12710), Pyrazolone Red B (21120),
Permanent Red R (12085), Lake Red C
(15585), Brilliant Carmine 6B (15850), Permanent Carmine FB (12490) (monoazo pigments), Benzidine Yellow G (21090), Benzidine Yellow GR (21100), Permanent Yellow NCR
(20040) (bisazo pigments), chromophthal yellow, chromophthal red (condensed azo pigments)
and so on. Dyeing lake pigments include quinoline yellow lake (47005), eosin lake (45380), alkali blue lake (42750A,
42770A) (Acidic dye lake pigment), Rhodamine Lake B (45170), Methyl Violet Lake (42535), Victoria Blue Lake (44045), Malachite Green Lake (42000) (Basic dye lake pigment), Alizarin Lake ( 58000) (mordant dye lake pigment). Nitro pigments include naphthol yellow S (10316), nitroso pigments include pigment green B (10006) and naphthol green B (10020), and phthalocyanine pigments include metal-free phthalocyanine blue (74100), phthalocyanine blue (74160), and phthalocyanine green (74260). )and so on. As a high-grade pigment,
Anthrapyrimidine Yellow (68420), Indanthrene Brilliant Orange GK (59305), Indanthrene Blue RS (69800), Thioindigolet B (73300) (vat dye pigments), Nickel Azo Yellow (12775) ( Metal complex salt pigment), perylene red (71140), perylene scarlet (71137) (perylene pigment), isoindolinone yellow (isoindolinone pigment), quinacridone red Y
(46500) and Quinacridone Magenta (73915). Carbon black (C.
I.77265). As the binder, either a water-soluble binder or a water-insoluble binder can be used, and the water-soluble binder is used in an aqueous/non-aqueous system (a system in which the binder is dispersed in a water-insoluble binder) by solvent coating. Water-insoluble binders are used for solvent coating and hot melt coating. Typical examples of such binders are illustrated below, but the binder is not limited to these, and two or more types may be used in combination. Examples of the binder include polyvinyl alcohol, methylcellulose, gelatin hydroxyethylcellulose, carboxymethylcellulose gum arabic, starch and its derivatives, casein, polyvinylpyrrolidone, butyral resin, ethylene ethyl acrylate styrene-butadiene copolymer, vinyl acetate resin, vinyl acetate resin. Copolymer, acrylic resin, methyl methacrylic resin, styrene/acrylonitrile resin,
Examples include ethylene-vinyl acetate copolymer, polyester resin, and petroleum resin. The amount of dye/pigment used based on the main component of the heat-melting ink is 0.5 to 40% by weight, preferably 1% by weight.
~25% by weight, waxes from 10 to 70% by weight, preferably 20 to 60% by weight,
The binder is 5 to 60 weight percent, preferably 10 to 50 weight percent. In the present invention, as described above, gallic acid or its derivatives, colored dyes and pigments, binders, and waxes are the main components, but other additives such as surfactants, dispersants, etc. are added when coating or printing on the support. Agents such as antistatic agents, antioxidants, and ultraviolet inhibitors may be added. As a support, thin paper such as capacitor paper, typewriter paper, tracing paper, synthetic paper, cellophane paper, polyester film, etc.
Synthetic resin films such as polyimide film, polyethylene film, polycarbonate film, polystyrene film, and Teflon film are used as they are or after heat-resistant treatment so that they do not stick to heat heads. Coating machines include hot melt coater, air knife coater, roll coater, blade coater,
Coating is carried out using a known coater such as a bar coater, and a known printing machine using a flexo method, a gravure method, etc. may also be used. In order to obtain a full-color image, at least yellow, magenta, and cyan color inks are partially printed on the same support in a line-sequential, area-sequential, or dot-sequential manner. For solvent coating, general solvents can be used, and for example, methanol, ethanol, isopropyl alcohol, toluene, methyl ethyl ketone, acetone, ethyl acetate, etc. can be used as appropriate. (E) Effect The gradation thermal transfer recording sheet of the present invention has a high degree of gradation by containing gallic acid or a derivative thereof in a heat-melting ink containing colored dyes and pigments, binders, and waxes on one side of the support. It is possible to record gradation. With conventional thermal transfer recording sheets, when forming images using a thermal head, when printing starts from a low energy state, there is little difference in transfer density from the energy range where transfer occurs to high energy, and the transfer density remains constant. Unable to obtain gradation. On the other hand, by containing gallic acid or a derivative thereof in the ink composition, the thermal transfer recording sheet of the present invention exhibits a smooth transfer density from a low energy range to a high energy range and can obtain gradation. This is a wax that has high transfer efficiency and gallic acid or its derivatives that have a high melting point to control the transfer properties and exhibits transfer with gradation. It works more effectively. (F) Examples Hereinafter, the present invention will be specifically explained with reference to Examples. Note that "parts" in Examples and Comparative Examples indicate parts by weight of solid content. Example 1 1-1 In producing a gradation thermal transfer recording sheet (donor sheet), the composition of the heat-melting ink was as follows, and the dry coating method was applied to a 9 μPET film that had been heat-resistant treated using a Mayer bar. 4
g/m ² was solvent coated. SOT Blue G (Hodogaya Chemical, melting point 74-75℃)
10 parts by weight 150〓 Paraffin wax 40 parts by weight Polyvinyl alcohol 20 parts by weight Lauryl gallate (melting point 96°C) 30 parts by weight The heat-melting ink was prepared as a 20% ethanol dispersion using a ball mill. be. The ink side of the prepared donor sheet was coated with plain paper (image receiving paper for thermal transfer paper, manufactured by Mitsubishi Paper Mills,
(Product name: TTR-PW), and from the back side of the donor sheet, the pulse width was set from 0.2 milliseconds at 16.0V using a facsimile tester manufactured by Matsushita Electronic Components.
Heated printing was performed at intervals of 3.0 milliseconds and 0.2 milliseconds, and the transferred image density was measured using an optical densitometer (Macbeth RD514 model). The results are shown in Table 1. In the same manner as 1-1, 1-2 and 1-3, and 1-1 to 1-3 were also tested as comparative examples, and the results are shown in Table 1.
It was listed on. As is clear from Table 1, Examples 1-1 to 1
-3 shows a density change with gradation, whereas in comparative examples 1-1 and 1-2, the transfer density is high from the low pulse width region and does not have gradation. . On the other hand, samples 1-3 had low transfer density in the low pulse width region and insufficient gradation.

[Table] Example 2 To prepare a gradation thermal transfer recording sheet (donor sheet), the following hot-melt hot-melt ink was prepared and coated on a heat-resistant 9μPET film at a coating density of 3.5 g/m ² It was hot melt coated so that Carbon Black 10 parts by weight Paraffin Wax (Product name manufactured by Nippon Seiro Co., Ltd., SP-
0145) 53 parts by weight ethylene-vinyl acetate resin 6 parts by weight petroleum resin (manufactured by Arakawa Chemical, trade name Alcon M)
6 parts by weight Ethyl gallate (melting point 150-153°C) 25 parts by weight The prepared donor sheet was printed in the same manner as in Example 1, and the results are shown in Table 2. Comparative Example 2 A donor sheet was prepared using the same method as in Example 2 except that ethyl gallate was removed from the hot-melt ink and the amount of paraffin wax was 78 parts by weight. Printing was carried out in the same manner as in Example 2, and the results are shown in Table 2. As is clear from Table 2, Example 2 showed density changes with gradation, whereas Comparative Example 2 showed high density from the low pulse region and could not obtain gradation.

【table】

[Table] (G) Effects of the Invention The present invention provides extremely high density gradation by containing 5 to 50% by weight of gallic acid or its derivatives in the heat-melting ink, and in addition to single-color coating, By using partial coating of the three colors yellow, magenta, and cyan, and the four colors black, a color image with high color reproducibility can be obtained, and an excellent gradation thermal transfer recording sheet with high industrial significance can be provided. It is something.

Claims (1)

[Claims] 1 Colored dyes and pigments, binders,
In a thermal transfer recording sheet coated with a heat-fusible ink layer containing waxes as a main component, the heat-fusible ink contains gallic acid or a derivative thereof in an amount of 5 to 50% by weight based on the total weight of the hot-fusible ink. A gradation thermal transfer recording sheet characterized by: 2. The gallic acid or its derivatives are gallic acid, methyl gallate, ethyl gallate, propyl gallate, isoamyl gallate, octyl gallate, lauryl gallate, stearyl gallate, trimethoxy gallic acid, trimethoxy gallic acid methyl ester, gallic acid. acid 3-methyl ether, gallic acid 4
The gradation thermal transfer recording sheet according to claim 1, wherein the gradation thermal transfer recording sheet is at least one selected from -methyl ether, gallic acid 3,4-dimethyl ether, and gallic acid 3,5-dimethyl ether.