JPS6280091A - Production of thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To reduce variations in then concentration of solids and enable a coloring agent to be uniformly dispersed, by coating a base with a coating liquid prepared by mixing a heat-fusible substance containing a coloring agent into an organic solvent, and evaporating off the organic solvent. CONSTITUTION:A coloring agent which is solid or semi-solid at room temperature and is dissolved or dispersed in a binder resin is a coloring material layer when being melted is incorporated in a coating liquid. The coloring agent may be a dye such as a direct dye and an acidic dye or a pigment such as carbon black and anthraquinone. A heat-fusible substance may be paraffin wax, Japan wax or the like. Further, gelatine, polyvinyl alcohol or the like is incorporated in the coloring material layer. Per 100pts.wt. of the coloring material layer, are used 50 to 90pts.wt. of the heat-fusible substance, 5 to 20pts.wt. of the coloring agent and 0 to 3pts.wt. of resins. A solvent such as toluene is used together with the above components to prepare the coating liquid, which is applied to a base such a coated paper by solvent coating, and the solvent is removed to obtain the coloring material layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a heat-sensitive transfer recording medium, and more specifically to a method for producing a heat-sensitive transfer recording medium that efficiently forms a uniform heat-melting coloring material layer on a support. Regarding the manufacturing method.

[Prior art]

Thermal transfer recording media are manufactured by coating a heat-melting coloring material layer on a support, and this involves a method of dissolving or dispersing the coloring material composition in a suitable solvent, coating it on the support and drying it. (solvent method), or a method in which a composition is heated to a temperature higher than its melting temperature to melt and liquefy and coat it on a support (hot melt method). Among these methods, the present invention belongs to the solvent method.

The solvent method involves a step of dispersing and dissolving the colorant. JP-A-58-128897, JP-A No. 60-838
As disclosed in No. 90 and No. 60-104390, the colorant dispersion and dissolution steps have conventionally been carried out using a solvent (including a coating solvent) used in the coating step.

Therefore, during the production of colorant dispersions, fluctuations (increases) in the solid content concentration due to evaporation of the coating solvent or agglomeration of the colorants are unavoidable, requiring high-precision heat retention equipment, and the solid state of the colorant dispersions There were problems such as the impossibility of storage in

Therefore, there is a strong demand for the development of a manufacturing technique that allows for less fluctuation in the solid content concentration of the coating solution, uniform dispersion of the colorant, and efficient work in the solvent method.

[Purpose of the invention]

The first object of the present invention is to provide a method for producing a stable thermal transfer recording medium using a coating liquid in which fluctuations in solid content concentration are reduced. The second object is to provide a method for manufacturing a thermal transfer recording medium in which a colorant is uniformly dispersed.

Third, there is no need for high-precision body temperature equipment, and the
Another object of the present invention is to provide a method for manufacturing a thermal transfer recording medium that allows safe manufacturing operations.

[Structure of the invention]

As a result of various studies on coating the mixture layer of thermal transfer recording media using the solvent method, the present inventors have found that the above problem can be solved by not using any solvent when dispersing the colorant in the heat-melting material. We have found a solution to this problem and have come up with the present invention.

That is, an object of the present invention is to provide a method for producing a heat-sensitive transfer recording medium having a heat-fusible coloring material layer on a support by the following (a) and (a).
This is achieved by including the steps (b) and (c).

(a) A step of incorporating a coloring agent into a heat-fusible substance.

(b) A step of producing a coating liquid by mixing the heat-melting substance containing the colorant obtained in step (a) with an organic solvent.

(c) A step of evaporating the organic solvent after coating the coating liquid produced in (b) on a support.

The present invention will be explained in more detail below.

The coating liquid used in the present invention contains at least one colorant. As the coloring agent, various dyes or pigments that have been widely used in the art can be used without any special restrictions. Substances that have a color and are solid or semi-solid at room temperature are used as colorants, and various pigments known in the art can be used.

Examples of the dye include direct dyes, acid dyes, basic dyes, disperse dyes, and oil-soluble dyes (including metal-containing oil-soluble dyes).

Pigments include inorganic pigments (carbon black, Prussian blue, cadmium sulfide, iron oxide, chromate, etc.) and organic pigments (anthraquinone, anthurone, triphendioxazine, quinacridone, phthalocyanine, etc.).

Specific examples of thermofusible substances preferably used in the present invention include bubble-in wax, microwax,
Paraffin waxes such as polyethylene wax, natural waxes such as beeswax, carnauba wax, and wood wax, ester waxes such as Hoechst wax, stearic acid, valmitic acid, behenic acid, myristic acid, 1.
Higher fatty acids such as 20-eicosanniic acid, higher alcohols such as stearyl alcohol and palmityl alcohol, higher amides such as stearamide, chloramide, palmitylamide, and esters such as butyl stearate, ethyl palmitate, myristyl stearate, etc. etc. can be mentioned. Other room temperature soluble waxes described in JP-A-58-128897 can also be preferably used in the present invention.

Two or more of these heat-melting substances may be used in combination.

The composition ratio of the coloring material layer of the present invention is not limited, but the heat-melting substance is 50 to 90 parts and the coloring agent is 5 to 20 parts with respect to 100 parts (parts by weight, same hereinafter) of the total amount of the coloring material layer. , 0 resins
~30 copies.

It is preferable that the color material layer of the present invention contains a resin. The resin used in the present invention preferably has a softening point (measured by the ring and ball method) of 40 to 200°C, and is a hydrophilic polymer or a hydrophobic polymer. Any of these can be used. Examples of hydrophilic polymers include gelatin, gelatin derivatives, cellulose derivatives, proteins such as casein, natural products and natural product derivatives such as polysaccharides such as starch, water-soluble polyvinyl compounds such as polyvinyl alcohol, polyvinylpyrrolidone, and acrylamide polymers. Examples include synthetic water-soluble polymers such as vinyl-based and polyurethane-based polymer latexes.

As a hydrophobic polymer, U.S. Patent No. 3.142.586
No. 3,143.386, No. 3,062,674, No. 3,220.844, No. 3.287.289,
The synthetic polymers described in 3.411.911 may be mentioned as examples.

Preferred polymers include polyvinyl butyral, polyvinyl formal, polyethylene, polypropylene,
Polyamide, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid terpolymer, polymethyl methacrylate Examples include acrylic resins such as, polyisobutylene, and rosin derivatives such as ester gum. In the present invention, one kind or a combination of two or more kinds of these resins are used.

In the present invention, a so-called dispersant may be used to disperse the colorant or to keep the dispersion state stable. Specific examples include sorbitan fatty acid ester, unsaturated fatty acid alkylolamide, alkylimidase, etc. Examples include phosphorus, polyacrylic acid partial fatty acid ester, and alkylbenzene sulfonic acid calcium salt. These dispersants may be present at the time of dispersion or may be included in the coating solvent. Note that heat-melting substances, resins, and other various additives may also act as dispersants for the colorant. be.

The coating liquid used in the present invention may contain various additives in addition to the above-mentioned components. For example, powder or fine particles of a metal with good thermal conductivity such as aluminum, copper, or zinc can be added as a thermally conductive substance. Such a thermally conductive substance promotes the heat conduction effect of melting, softening, or sublimating the coloring material layer by heat. Furthermore, vegetable oils such as castor oil, linseed oil, and olive oil, animal oils such as whale oil, and mineral oils may be suitably used as softeners.

Examples of the dispersing machine used in the present invention include a dispersion machine, a homomixer, a kneader, a roll mill, and a sand mill.

The solvent used in the present invention may be any solvent that dissolves or disperses the colorant layer components, such as toluene,
In addition to xylene, trichlene, white spirit, etc.
- Paraffinic solvents such as hexane, ligroin, isoparaffin, ketone solvents such as acetone, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, alcoholic solvents such as methanol, ethanol, propatool, butanol, ester solvents such as ethyl acetate, dimethyl Examples include organic solvents such as special solvents such as formamide and dimethyl sulfoxide, and water, and mixed solvents thereof may also be used. The amount of these solvents is preferably 0.05 parts by weight to 20 parts by weight per 1 part by weight of coloring material layer components.

Coating methods suitable for solvent coating a support with a colorant layer coating solution are known in the art, and these techniques can also be used in the present invention. For example, the coating liquid is 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 is removed to form a color material layer of 15 μm or less. can be painted.

The support used in the present invention may be any known support, but it is desirable that the support has heat-resistant strength, dimensional stability, and surface smoothness. Heat resistance strength requires strength and dimensional stability to maintain the toughness of the support without becoming softened or corrupted by the heating temperature of a heat source such as a thermal head, and surface smoothness requires heat resistance on the support. It is desired that the colorant layer containing the fusible substance has sufficient smoothness to exhibit a good transfer rate. The smoothness should be 100 sec or more in the smoothness test (JIS P 8119) using a Beck tester (300 sec or more, a better transfer rate and reproducible image can be obtained.As for the material, For example, paper such as plain paper, condenser paper, laminated paper, coated paper, resin films such as polyethylene, polyethylene terephthalate, polyester, polystyrene, polypropylene, polyimide, paper-resin film composites, metal sheets such as aluminum foil, etc. etc. are all suitably used.

The thickness of the support is usually about 60μ to obtain good thermal conductivity.
It is preferably less than m, particularly 2 to 20 μm.

Furthermore, in the thermal transfer recording medium of the present invention, the structure of the back side of the support is arbitrary.

The thermal transfer recording medium of the present invention has at least one coloring material layer obtained by the present invention, and may have other constituent layers such as a subbing layer, an intermediate layer, or an overcoat layer. That is, for example, examples of the undercoat layer include silicone resin, melamine resin, polyvinacetal resin, polyethylene, polyvinyl chloride, polyvinylidene chloride, fluororesin, etc., and the application of the undercoat layer is similar to that of the coloring material layer. This can be done prior to application.

〔Example 〕

Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, "1 part" used below indicates "part by weight."

Example 1 The following composition was dispersed in a molten state at 90°C for 5 hours using a sand grinder to obtain a pigment dispersion.

Carnauba wax 29 parts Paraffin wax 29 parts Microcrystalline wax 29 parts Ethylene-vinyl acetate copolymer 5 parts Pigment Yellow 12 (C, 1, 2
1090) 20 parts of the obtained pigment dispersion were added to 80 parts of xylene and stirred at 60° C. for 1 hour to dissolve. At this time, almost no evaporation of the solvent was observed.

The resulting coating solution was coated on a polyethylene terephthalate support with a thickness of 6 μm at 60° C., and dried by blowing hot air to obtain a heat-sensitive recording medium sample having a coloring material layer with a dry film thickness of 3.0 μm.

When the obtained sample was observed under a microscope, almost no pigment aggregates were observed, and the pigment was in a good dispersion state.

Example 2 A thermal transfer recording medium sample was obtained in the same manner as in Example 1 except that Pigment Yellow 12 was replaced with Pigmentlet 57:1 (C, 1, 15850: 1). Again, almost no evaporation of the solvent was observed during the dissolution of the pigment dispersion in xylene. Also,
When the obtained sample was observed under a microscope, almost no pigment aggregates were observed, and the pigment was in a good dispersion state.

Example 3 Example 1 was repeated in exactly the same manner except that Pigment Yellow 12 was replaced with Pigment Blue 15 (C, 1,74160).

In this case as well, no evaporation of the solvent was observed during the production of the coating solution, and the pigment dispersion state of the obtained thermal transfer recording medium sample was good.

Example 4 Example 1 was repeated in exactly the same manner except that Pigment Yellow 12 was replaced with carbon black.

In this case as well, no evaporation of xylene was observed during the production of the coating solution, and the pigment dispersion state of the obtained thermal transfer recording medium sample was good.

, -111--\ μ lower, a white) Example 5 In Example 1, the temperature when dispersing the pigment was set to 80~
A thermal transfer recording medium sample was obtained in the same manner as in Example 1, except that the temperature during dissolving the pigment dispersion in xylene was changed back and forth between 50 and 70°C.

In this case, as in Examples 1 to 4, almost no solvent evaporation was observed in the coating liquid manufacturing process, and the pigment dispersion state of the obtained sample was good.

Comparative Example 1 The following composition was subjected to dispersion treatment using a sand grinder for 8 hours while maintaining the temperature at 60°C to obtain a pigment dispersion coating liquid.

Carnauba wax 29 parts Paraffin wax 29 parts Microcrystalline wax 29 parts Ethylene-vinyl acetate copolymer 5 parts Pigment Yellow 12
8 parts xylene 400 parts The solid content concentration at the beginning of dispersion was 20% by weight, but the solvent evaporated during dispersion, and the solid content concentration at the end of dispersion increased to 25% by weight.

The obtained coating solution was coated on a polyethylene terephthalate support with a thickness of 6 μm at 60° C., and dried by blowing hot air to obtain a thermal transfer recording medium sample having a coloring material layer with a dry film thickness of 3.5 μm. Ta.

When the obtained sample was observed under a microscope, many aggregates of pigment were observed, and the dispersion state of the pigment was poor.

Comparative Example 2 When producing a coating liquid having the same composition as Comparative Example 1, the dispersion temperature was changed back and forth between 55 and 65°C, and dispersion treatment was performed using a sand grinder for 8 hours to obtain a coating liquid.

The solid content concentration at the beginning of dispersion is 20% by weight, but it is 3% at the end of dispersion.
It increased to 0% by weight.

The resulting coating solution was coated on a polyethylene terephthalate support with a thickness of 6 μm at 60″C, and dried by blowing hot air to obtain a thermal transfer recording medium sample having a coloring material layer with a dry thickness of 4 μm.

When the obtained sample was observed under a microscope, many aggregates of pigment were observed, and the state of dispersion of the pigment was poor.

This result shows that, compared to Example 5, the tolerance for temperature control during production of the coating liquid is smaller.

Example 6 The pigment dispersion obtained in Example 1 was solidified and left to stand for one month, and then dissolved in xylene in the same manner as in Example 1, and a thermal transfer recording medium sample A was obtained through the same operation.

On the other hand, the dispersion-treated coating liquid obtained in Comparative Example 1 was stored in a closed container for a day and night, and then subjected to the same operations as in Comparative Example 1 to prepare a thermal transfer recording medium sample having a coloring material layer with a dry film thickness of 3.5 μm. I got a B.

When the obtained samples were observed under a microscope, it was found that almost no pigment aggregates were observed in Sample A, and the pigment was well dispersed, but in Sample B, a large number of pigment aggregates were observed. However, the dispersion state of the pigment was extremely poor.

〔Effect of the invention〕

By implementing the present invention, the following effects can be obtained.

(1) Since no coating solvent is used in the colorant dispersion and dissolution process, fluctuations in the solid content concentration of the coating solution are small;
Stable and uniform production is possible.

(2) Since the viscosity of the colorant dispersion and dissolution medium is high and the shear force required for dispersion can be increased, a heat-melting colorant layer with almost no colorant aggregates can be applied.

(3) High precision heat insulation equipment is not required in the dispersion process, and deterioration of the working environment and pollution caused by evaporation of the solvent can be prevented.

(4) Since a colorant dispersion composition that does not contain a coating solvent can be stably stored in a solid state, production efficiency can be improved.

Claims (1)

[Scope of Claims] A method for producing a heat-sensitive transfer recording medium having a heat-melting coloring material layer on a support, characterized by comprising the following steps (a), (b), and (c). A method for manufacturing a recording medium. (a) A step of incorporating a coloring agent into a heat-fusible substance. (b) A step of producing a coating liquid by mixing the heat-melting substance containing the colorant obtained in step (a) with an organic solvent. (c) A step of evaporating the organic solvent after coating the coating liquid produced in (b) on a support.