JPS60104390A - Production of thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To facilitate controlling the thickness of a coated film and to dry the film uniformly by a method wherein a coating liquid obtained by dissolving or dispersing at least a coloring agent and a heat-fusible substance in a solvent is applied to a base at a temperature near the clouding point of the coating liquid. CONSTITUTION:A coloring agent such as a direct dye, an acid dye, a basic dye and a dispersing dye and a heat-fusible substance are dissolved or dispersed in a solvent to prepare a coating liquid. Examples of the heat-fusible substance include paraffin wax, natural wax and higher alcohols. The base such as a paper and a resin film is solvent-coated with the coating liquid at a temperature near the clouding point of the coating liquid by a reverse roll coater method, an extrusion coater method or the like to provide a coloring material layer having a thickness of not more than 15mum. The coloring material layer is constituted of 50-90pts.wt. of the heat-fusible substance, 5-20pts.wt. of the coloring agent and 0-20pts.wt. of a resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a thermal transfer recording medium. Specifically, the present invention relates to a method for producing a thermal transfer recording medium, which makes it possible to obtain a thermal transfer recording medium having a coloring material layer of constant quality.

[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 groove paper using 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, as a support, films with excellent surface smoothness and dimensional stability may be used to ensure good II8 development of the dye transfer image obtained from the color material layer coated on this substrate. is used.

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 real 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-58-12
Publication No. 8897 discloses a technique in which a coloring material layer is applied at room temperature using a wax (heat-melting substance) that dissolves 10% by weight or more in a solvent.
(When applying i, the viscosity of the coating solution becomes very low, so there are restrictions on the coating method and it is extremely difficult to control the coating film thickness, and it is difficult to obtain a thermal transfer recording medium with a color material layer of a certain quality. Therefore, this technique not only has many limitations on the coating device, but also has drawbacks such as the tendency to cause uneven drying during drying.

[Objective of the Invention] The object of the present invention is that since the viscosity of the coating liquid during coating is high, the coating film thickness can be easily controlled, and the occurrence of drying unevenness can be suppressed, and stable quality can be achieved with a constant film thickness. The object of the present invention is to clarify a method for producing a heat-sensitive transfer recording medium that can provide a heat-sensitive transfer recording medium having a coloring material layer.

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 inventor of the present invention has developed a method for producing a thermal transfer recording medium in which a coloring layer is coated on a support by a solvent coating method, in which at least a colorant and a heat-fusible substance are combined. The inventors have discovered that the above object can be achieved by coating a coating solution prepared by dissolving or dispersing the compound in a solvent on a support at a temperature around the clouding point of the coating solution, leading to the present invention.

In the present invention, the cloud point of a coating solution refers to the cloud point measured in a system excluding the colorant contained in the solution.

[Structure of the invention] The present invention will be described in further detail below.

The coating liquid used in the present invention is made by dissolving at least one colorant and a heat-melting substance in a solvent. The coating 4
When coating Solution J on a support, the "cloud point temperature of the coating solution" refers to the clouding point temperature of the coating solution after adding a predetermined amount of the coating solution components excluding the colorant into a predetermined amount of an appropriate solvent and dissolving them by heating. , the temperature of the liquid is gradually lowered, and the liquid temperature is the temperature at which it can be visually determined that turbidity has started to occur in the liquid. (Refers to the actual amount of liquid in the applicable coating liquid when used as a liquid.)
"The coating temperature is near the cloud point" is defined as follows. That is, assuming that the coating temperature is T and the cloud point is Tc, Tc-5°
It refers to the case in the range of C≦T≦Tc+2o°c, and Tc
It is preferable to be in the range of '-3°C≦T≦Tc+10'0. When the coating temperature exceeds rTc+20°C, the viscosity of the coating liquid is too low and it becomes difficult to control the coating film thickness.
On the other hand, when the temperature is less than rTc-5°C, the colorant components are precipitated.
Or they will separate.

Specific examples of thermofusible substances preferably used in the present invention include paraffin wax, microwax,
Paraffin waxes such as polyethylene wax, natural waxes such as beeswax, carnauba wax, and wood wax, Nidityl waxes such as Hoechst wax, stearic acid, palmitic acid, hehenic acid, myristic acid, 1,
Higher fatty acids such as 2o-eicosanniic acid, higher alcohols such as stearyl alcohol and palmityl alcohol, higher amides such as stearamide, oleamide and palmitylamide, esters such as butyl stearate, ethyl palmitate and myristyl stearate, etc. can be mentioned. In the present invention, two or more of these heat-melting substances may be used in combination.

The coloring agent contained in the coloring material layer of the present invention may be appropriately selected from conventionally known dyes, such as direct dyes, acid dyes, 112-based dyes, molecule P1. You can choose from dyes, oil-soluble dyes, etc. The dye used in the coloring material layer of the present invention may be any dye that can be transferred (migrated) together with a heat-melting substance, and thus may be a pigment in addition to the above.

The composition ratio of the coloring material layer of the present invention is not limited, but with respect to 100 parts (parts by weight, hereinafter) of the total amount of the coloring material layer, the heat-melting substance is 50 to 80 parts, and the colorant is 5 to 20 parts. Part, resins are 0~
There are 20 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'O, and either a hydrophilic polymer or a hydrophobic polymer 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. Examples of hydrophobic polymers include U.S. Pat. No. 3,142.586, U.S. Pat.
No. 386, 3,062. f174, 3.220,
No. 844, No. 3,287.2813, No. 3,411,
The synthetic polymers described in No. 811 may be mentioned by way of example. 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, vinyl chloride-vinyl acetate-malein. Examples include acid terpolymers, acrylic resins such as polymethyl methacrylate, polyisobutylene, rosin derivatives such as ester gums, and the like. In the present invention, one kind or a combination of two or more kinds of these resins are used. 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.

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

The solvent used in the present invention may be any solvent as long as it dissolves the colorant layer components when heated, such as toluene, xylene, trichlene, white spirit, etc.
- Paraffinic solvents such as hexane, ligroin, and isoparaffin; ketone solvents such as acetone, cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone; alcoholic solvents such as methanol, ethanol, 2-propertool, and butanol; and ester solvents such as ethyl acetate. Examples include solvents, organic solvents such as special solvents such as DMF and DMSO, and water, and mixed solvents thereof may also be used.

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 coloring material layer of 15 pm or less. can be painted.

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 has other constituent layers such as an undercoat layer, an intermediate layer, or an overcoat layer. You can leave it there. That is, for example, examples of the undercoat layer include silicone resin, melamine resin, polyvinacetal resin, polyethylene, polyvinyl chloride, polyvinylidene chloride, fluorine resin, etc., and the application of the undercoat layer is performed on the basis of the color material layer. This can be done prior to coating.

[Effects of the Invention] According to the present invention, in a method for producing a heat-sensitive transfer recording medium in which a coloring material layer is coated on a support by a solvent coating method, at least a coloring agent and a heat-melting substance are dissolved or dispersed in a solvent. Since the coating liquid made of the above-mentioned coating liquid is applied to the support at a temperature near the cloud point of the coating liquid, the above objectives can be achieved. In particular, since the control of the film J1 is easy, the desired thin layer of the coloring material can be formed. The effect is that the layer can be stably obtained.

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

Example 1 Paraffin wax (melting point 64°C) 10 parts Carnahata wax 10 parts Ethylene-vinyl acetate copolymer 5 parts Carbon black 5 parts 10 Parts of the above composition were dissolved and dispersed in 200 parts of xylene to form a coloring material layer. A coating solution (D (liquid temperature: 60°C)) was prepared.

The cloud point of this coating solution (■) is 40°C.
After cooling to 38°C and 38°C, 6. A sample of a thermal transfer recording medium having a coloring material layer with a thickness of 3.0 gm (43°C Painted iHi
) and (coated at 38°C) were obtained.

When the colorant layer-coated surface of Sample (j) and (Motion) was observed under a 10x magnifying glass, it was observed that there was no drying unevenness and that the surface condition was uniform.

When transfer printing was performed on plain paper using a thermal printer (a prototype machine equipped with a thin-film line thermal head with a heating element density of 8 dots/mm), high-quality transfer printing was obtained from both samples ■ and (N). Obtained.

Comparative Example 1 Coating solution ■ of Example 1 was coated on a polyethylene terephthalate film support with a thickness of 8.0 pm at each temperature of 33°C and 62°C in the same manner as sample ■, and dried by blowing hot air. , a coloring material layer was provided, and two types of thermal transfer recording medium samples, Φ) and Φ, were prepared.

For each sample (1) and (2), the coating film thickness was measured and found to be non-uniform, ranging from 27 to 3.8 grn, and when the surface to which the coloring material layer was applied was observed with a 10x magnifying glass, uneven drying was observed. Furthermore, when transfer recording was performed on plain paper using a thermal printer as in Example 1, the print density,
Resolution etc. were not constant.

Patent applicant: Konishiroku Photo Industry Co., Ltd. Deputy Physician BUC Saka 1” Nobuaki (and 1 other person)

Claims (1)

[Claims] In a method for producing a heat-sensitive transfer recording medium in which a coloring material layer is coated on a support by a vinyl vent coating method, a coating liquid comprising at least a coloring agent and a heat-melting substance dissolved or dispersed in a solvent is applied to the coating. A method for producing a thermal transfer recording medium, which comprises coating a support on a support at a temperature near the cloud point of liquid J.