JPH0441074B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a thermal transfer recording medium.

Specifically, it is possible to obtain a thermal transfer recording medium having a coloring material layer of constant quality. The present invention relates to a method of manufacturing a thermal transfer recording medium.

[Prior Art] A thermal transfer recording medium has been conventionally used as a recording medium for transferring and forming an image on a recording sheet such as plain paper by a thermal printer, a thermal facsimile, or the like. This thermal transfer recording medium has at least one coloring material layer on a support, and the coloring material layer includes, for example, a layer containing a coloring agent made of a dye such as a pigment and a heat-fusible substance. It has been known. In addition, films with excellent surface smoothness and dimensional stability are used as the support in order to obtain good reproducibility of the dye transfer image obtained from the color material layer coated on the support. There is.

A thermal transfer recording medium is manufactured by coating a coloring material layer on such a support having excellent surface smoothness and dimensional stability by a hot melt method or a solvent method. Among these, the present invention is a technology that belongs to the solvent method.

The technique of applying a coloring material layer by solvent coating generally has a problem in that it is difficult to obtain a stable coloring material layer with a constant film thickness. For example, JP-A-58-128897 discloses a technique in which a coloring material layer is applied at room temperature using wax (a heat-melting substance) that dissolves 10% by weight or more in a solvent. According to , when coating, the viscosity of the coating solution is sensitive to changes in temperature, or the viscosity of the coating solution becomes very low, so there are restrictions on the coating method and control of the coating film thickness. This is extremely difficult and has the disadvantage that it is difficult to obtain a thermal transfer recording medium having a coloring material layer of constant quality. Therefore, with this technique, a lot of cost and labor is required for coating management, such as controlling the temperature during coating and controlling the coating speed.

[Objective of the Invention] The object of the present invention is to provide a colorant layer in which the viscosity of the coating liquid during coating is not easily affected by environmental temperature changes, the coating speed is easy to control, and the quality is stable with a constant film thickness. An object of the present invention is to clarify a method for manufacturing a thermal transfer recording medium that can provide a thermal transfer recording medium having the following properties.

Other objects of the invention will become apparent from the following description of the specification.

[Summary of the Invention] As a result of intensive research, the present inventors have developed a method for producing a thermal transfer recording medium in which a coloring material layer is coated on a support by a solvent coating method.
Applying a coating solution made by dissolving or dispersing in a solvent a colorant, a resin, and a heat-fusible substance that does not dissolve 5 g or more at 40°C in 100 g of a solvent onto a support, and then removing the solvent. The inventors have discovered that the above object can be achieved by the following methods, and have arrived at the present invention.

[Structure of the invention] The present invention will be explained in more detail below.

The coating liquid used in the present invention is made by dissolving at least one of each of a colorant, a resin, and the heat-melting substance of the present invention in a solvent.

The resin of the present invention is preferably a resin that can dissolve 1 g or more in 100 g of solvent at 40°C.

As the resin of the present invention, either a hydrophilic polymer or a hydrophobic polymer can be used. Hydrophilic polymers are typically transparent or translucent hydrophilic colloids, such as gelatin, gelatin derivatives, cellulose derivatives, proteins such as casein, natural products and natural product derivatives such as polysaccharides such as starch, and polyvinyl alcohol. Synthetic water-soluble polymers such as water-soluble polyvinyl compounds such as , polyvinylpyrrolidone, and acrylamide polymers, as well as vinyl-based and polyurethane-based polymer latexes. The hydrophobic polymer is preferably transparent, as described in US Pat. No. 3,142,586;
No. 3143386, No. 3062674, No. 3220844, No.
Examples include the synthetic polymers described in No. 3287289 and No. 3411911. Preferred polymers include polyvinyl butyral, polyacrylamide, cellulose acetate butyrate, cellulose acetate phthalate, ethylcellulose, cellulose acetate, polyvinylpyrrolidone, polystyrene, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid- terpolymer, dextrin,
Examples include sodium alginate, polymethyl methacrylate, polyisobutylene, and the like. In the present invention, one type or a combination of two or more of these resins are used, and it is particularly preferable to use one type or a combination of two or more types of resins that can dissolve 1 g or more in 100 g of solvent at 40°C.

The heat-melting substance of the present invention is added to 100 g of the main medium at 40°C.
A substance that does not dissolve in an amount of 3 g or more is preferable, and a substance that does not dissolve in an amount of 3 g or more is preferable.

Examples of the heat-melting substance of the present invention include vegetable waxes such as carnauba wax, wood wax, auricilla wax, and espal wax; animal waxes such as beeswax, insect wax, serrata wax, spermaceti wax; paraffin wax, and microcrystalline wax. In addition to waxes such as petroleum waxes such as , ester waxes and oxidized waxes, mineral waxes such as montan wax, ozokerite, and ceresin; palmitic acid, stearic acid,
Higher fatty acids such as margaric acid and behenic acid; higher alcohols such as palmityl alcohol, stearyl alcohol, behenyl alcohol, marganyl alcohol, myricyl alcohol, and eicosanol; cetyl palmitate, myricyl palmitate, cetyl stearate, myricyl stearate, etc. Higher fatty acid ester; amides such as acetamide, propionic acid amide, palmitic acid amide, stearic acid amide, amide wax; rosin derivatives such as ester gum, rosin maleic acid resin, rosin phenolic resin, hydrogenated rosin; phenolic resin, terpene resin, Polymer compounds with a softening point of 50 to 120°C such as cyclopentadiene resins and aromatic resins; higher amines such as stearylamine, behenylamine, and palmitinamine; and polyethylene oxides such as polyethylene glycol 4000 and polyethylene glycol 6000. , these may be used alone or in combination. Among these, waxes such as vegetable waxes, animal waxes, petroleum waxes, mineral waxes, and rosin derivatives are particularly preferred. In the present invention, one or a combination of two or more of these heat-fusible substances that do not dissolve 5 g or more in 100 g of the main medium at 40° C. can be used.

The solubility of the resin and thermofusible substance of the present invention is the value obtained when dispersing in a solvent at 40° C. for several tens of minutes with normal stirring, for example, with a homogenizer or a sand mill.

In the present invention, when two or more heat-melting substances are used together, it is not necessary for both heat-melting substances to satisfy the solubility of the present invention at the same time, and one of the heat-melting substances used in combination does not have to satisfy the solubility of the present invention. It is sufficient if the solubility conditions are satisfied.

The coating liquid used in the present invention contains at least one colorant. As the heat coloring agent, various dyes or pigments that have been widely used in the art can be used without any particular restrictions. for example,
A substance that can be dissolved or dispersed in the binder resin in the colorant layer when melted, has a color, and is solid or semi-solid at room temperature is used as the colorant, and various pigments known in the art may be used. Can be used. Specifically, the following can be mentioned. That is, the yellow pigments include Kayalon Polyester Light Yellow 5G-S (Nippon Kayaku), Oil Yellow S-7 (white clay), Eizenspiron GRH Special (Hodogaya), Sumiplast Yellow FG (Sumitomo), and Eizenspiron. Ron Yellow GRH (Hodogaya),
etc. are preferably used. As red pigments, Diaceriton Fastread R (Mitsubishi Kasei), Dianics Brilliant Red BS-E (Mitsubishi Kasei),
Sumiplast Stretched FB (Sumitomo), Sumiplast Stretched HFG (Sumitomo), Kayalon Polyester Pink
RCL-E (Nippon Kayaku), Eizenspiron Red
GEH Special (Hodogaya), etc. are preferably used. Blue pigments include Diaceritone Fast Brilliant Blue R (Mitsubishi Kasei), Dianics Blue EB-E (Mitsubishi Kasei), Kayalon Polyester Blue B-SF Conc (Nippon Kayaku), and Sumiplast Blue 3R (Sumitomo). , Sumiplast Blue G (Sumitomo), etc. are preferably used. In addition, as yellow pigments, Hansa Yellow G (3), Tartrazine Lake, etc. are used, and as red pigments, brilliant carmine FB-Pure (Sanyo Color), brilliant carmine 6B (Sanyo Color), Alizarin Lake, etc. are used. As the blue pigment, cerulean blue, Sumikaprint Cyanine Blue GN-O (Sumitomo), phthalocyanine blue, etc. are used, and as the black pigment, carbon black, oil black, etc. are used. In addition, metal particles or metal oxides may also be used.

In addition to the above components, the coating liquid used in the present invention includes
Various additives may be included. for example,
A thermally conductive substance can be added. Examples include metals with good thermal conductivity such as aluminum, copper, and zinc. Such a thermally conductive substance promotes the heat conduction effect of melting, softening, or sublimating the coloring material layer by heat. Also, as a softener,
vegetable oils such as castor oil, linseed oil, and olive oil;
Animal oils such as whale oil and mineral oils may be suitably used.

These resins, heat-melting substances, and coloring agents are used in amounts of 0.5 to 30 parts, 40 to 90 parts, and 2 to 90 parts, respectively, based on 100 parts (parts by weight, same hereinafter) of the total amount of the heat-melting color material layer.
It is preferable to set the blending ratio to 25 parts, and in that case, the melt transferability of the formed heat-melting coloring material layer is extremely good.

Each component of the present invention is dissolved or dispersed in a solvent to form a coating liquid.

Examples of the solvent used in the present invention include paraffinic solvents such as n-hexane, ligroin, and isoparaffin; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; alcoholic solvents such as methanol, ethanol, propanol, and butanol; Examples include water, ester solvents such as ethyl acetate, special solvents such as DMF, DMSO, etc. Preferably, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, alcohols such as methanol, ethanol, propanol, butanol, etc. Examples include ester solvents such as ethyl acetate and ethyl acetate, and mixtures thereof may also be used.

The solvent of the present invention satisfies the solubility of the present invention for resins and thermofusible substances.

Coating methods suitable for applying a solvent coating of a colorant layer coating solution onto a support are known in the art, and these techniques can also be used in the present invention. For example, the coating solution of the present invention can be solvent coated using any known technique such as a reverse roll coater method, an extrusion coater method, a gravure coater method, or a wire bar coating method, and then the solvent can be removed to form a coating of 15μ or less. A color material layer can be applied.

The support used in the present invention may be any known support. Further, the thermal transfer recording medium of the present invention has at least one coloring material layer obtained by the present invention, and also has other constituent layers such as a subbing layer, an intermediate layer, or an overcoat layer. It's okay. That is, for example, examples of the undercoat layer include silicone resin, melamine resin, polyvinacetal resin,
Examples include polyethylene, polyvinyl chloride, polyvinylidene chloride, fluororesin, and the like, and the subbing layer can be applied prior to applying the coloring material layer.

[Effects of the Invention] According to the present invention, the colorant, the resin, and the solvent 100
A coating solution made by dissolving or dispersing 5 g or more of a heat-fusible substance that does not dissolve at 40°C in a solvent is applied onto the support, and then the solvent is removed, so the above purpose cannot be achieved. In particular, since the film thickness can be easily controlled, the desired thin coloring material layer can be stably obtained.

[Example] Examples are given below, but the embodiments of the present invention are not limited thereto.

Example 1 100 ml of 2-propanol, 20 g of heat-fusible substance insoluble in the 2-propanol (10 g of Micro Wax 155, 10 g of Hoechst Wax F, manufactured by Nippon Seiro Co., Ltd.), 40 g for 100 g of 2-propanol ℃
A mixture of 1 g of Hoechst Co., Ltd. and 2 g of a resin (acrylic resin Tesroid 931, manufactured by Tokushima Seisei Co., Ltd.) was dissolved and dispersed for 1 hour using a homogenizer while cooling on ice to obtain a milky white dispersion 1.

On the other hand, 30 g of carbon black (RAVEN1250 manufactured by Columbia Carbon Co., Ltd.), the above-mentioned Tesroid 931
A mixture of 3 g of 2-propanol and 100 ml of 2-propanol was dissolved and dispersed in a sand mill for 7 hours to obtain dispersion 2.

Mix 1100 ml of the dispersion liquid and 230 ml of the dispersion liquid,
Further dilute with 2-propanol to 10% solid content.
Coating liquid 1 was prepared. When the viscosity change with respect to temperature of this coating liquid 1 was measured, as shown in FIG. 1, the viscosity change around room temperature was small.

This coating liquid 1 was applied at each temperature of 10°C, 25°C, and 45°C onto a polyethylene terephthalate film support with a thickness of 5.4 μm using a wire bar to form a coloring material layer with a thickness of 2.8 μm after drying. Three types of thermal transfer recording medium samples were prepared.

When the colorant layer coated surface of each sample was observed using a 10x magnifying glass, it was found that the surface condition was the same regardless of the temperature change during coating.

Thermal printer (heating element density 8 dots/
A prototype machine equipped with a thin film type line thermal head of mm. ) was used to perform transfer recording on plain paper.
Transfer prints of equivalent quality were obtained for each sample.

Example 2 100 ml of ethyl acetate, 25 g of a thermofusible substance insoluble in the ethyl acetate (12.5 g of Micro Wax 155 manufactured by Nippon Seiro Co., Ltd., 12.5 g of Hoechst Wax F manufactured by Hoechst), and 100 g of ethyl acetate. against
Polyethylene-ethyl acrylate copolymer that dissolves at least 1g at 40℃ (manufactured by Nippon Unicar Co., Ltd.)
NUC6070) 3g, and carbon black (RAVEN1250 manufactured by Columbia Carbon) 6g
Coating liquid 2 was prepared by dissolving and dispersing the mixture with a ball mill for 2 days. When the viscosity change with respect to temperature of this coating liquid 2 was measured, as shown in FIG. 2, the viscosity change around room temperature was small.

This coating liquid 2 was applied with a wire bar onto a polyethylene terephthalate film support with a thickness of 5.4μ at each temperature of 10°C, 25°C, and 40°C to form a coloring material layer with a thickness of 2.8μ after drying. Three types of thermal transfer recording medium samples were prepared.

When the colorant layer coated surface of each sample was observed using a 10x magnifying glass, no difference was observed in the surface condition, regardless of temperature changes during coating.

When transfer recording was performed on plain paper using a thermal printer in the same manner as in Example 1, no difference in the quality of transfer printing was observed for each sample.

Comparative Example 1 Coating liquid 3 was obtained in the same manner as in Example 1 except that xylene was used instead of ethyl acetate. In addition, the amount dissolved per 100g of xylene at 40℃ is
The amount of Micro Wax 155 was 20 g or more, and the amount of Hoechst Wax F was 6 g.

When the viscosity change of this coating liquid 3 was measured with respect to temperature, as shown in FIG. 3, it changed significantly between 10 and 40°C. Also, when the temperature was increased, the viscosity value was different from that when the temperature was also decreased.

Next, this coating solution 3 was applied at each temperature of 10°C, 25°C, and 40°C onto a polyethylene terephthalate film support with a thickness of 5.4 μm using a wire bar to form a coloring material layer with a thickness of 2.8 μm after drying. , and three types of thermal transfer recording medium samples were prepared.

For each test, when the surface coated with the coloring material layer was observed using a 10x magnifying glass, it was found that there was a strong dependence on temperature changes during coating, and the appearance of the coated surface was clearly visible when the temperature rose and fell at the same temperature. Differences were observed, and there were even areas where uneven coating was observed. Furthermore, when transfer recording was performed on plain paper using a thermal printer as in Example 1, differences in print density, resolution, etc. were observed, and the influence of temperature during coating was strongly recognized.

[Brief explanation of drawings]

Figures 1 and 2 are graphs showing the relationship between coating liquid temperature and coating liquid viscosity in a thermal transfer recording medium of the present invention, respectively, and Figure 3 is a graph showing the relationship between coating liquid temperature and coating liquid viscosity in a thermal transfer recording medium of a comparative example. It is a graph showing the relationship between

Claims (1)

[Claims] 1. In a method for producing a thermal transfer recording medium in which a coloring material layer is coated on a support by a solvent coating method, a coloring agent, a resin, and 100 g of a solvent are mixed at 40°C.
1. A method for producing a thermal transfer recording medium, which comprises coating a support with a coating solution prepared by dissolving or dispersing in a solvent a heat-fusible substance that does not dissolve in excess of 5 g, and then removing the solvent.