JPS62121090A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To obtain high-density images with excellent thermal sensitivity, preservability and gradation properties, by providing two layers differing in characteristics to each other on a base. CONSTITUTION:A first layer 3 having a fine network structure 2 is provided on the surface of a base 1, and a heat-fusible ink layer 4 is provided thereon. A portion of the ink in the ink layer 4 is caused to penetrate into a fine network structure to form an ink structure 5 in a first layer. When a receiving sheet is laid on the surface of the ink layer of this recording medium and the laminate is heated by a thermal head or the like from the base side, the ink thus melted gradually exudes to the surface of the receiving sheet while keeping balance with the force for penetrating into the fine network structure. The amount of the ink permitted to exude varies depending on the intensity of thermal energy applied by the thermal head or the like. Accordingly, by controlling the thermal energy, the amount of a coloring agent transferred can be varied, and a transferred image reproducing the gradations of an original image with favorable fidelity over a wide range can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a thermal transfer recording medium on which a recorded image is melted and transferred by heating with a thermal heater, laser, or the like.

Prior Art Conventionally, as thermal transfer recording media, there have been known transfer sheets in which a heat-sublimable dye layer is provided on a support, and transfer sheets in which a heat-fusible material and a face are provided on a support. It is used to form an image on a receiving sheet by printing.

However, although the method using heat-sublimable dyes has excellent image gradation expression, it has low thermal sensitivity and poor image storage stability. In addition, methods using thermofusible substances and pigments have excellent heat sensitivity and storage stability, but have the disadvantage of not being able to express gradation.

■--F The present invention aims to improve the drawbacks of the above-mentioned prior art.
It is an object of the present invention to provide a thermal transfer recording medium that has excellent thermal sensitivity and can produce high-density images that are particularly excellent in storage stability and gradation properties.

The present invention has a first layer having a fine network structure made of resin on a support, and a heat-melt ink layer made of a heat-melt material and a colorant that are solid at room temperature on top of the first layer. It is a thermal transfer recording medium with

The structure of the recording medium of the present invention will be explained in detail with reference to FIG. 1. A first layer 3 having a fine network structure 2 is provided on the surface of a support 1, and a heat-melting ink layer 4 is formed on the first layer 3. is.

A portion of the ink has penetrated into the fine network forming the ink structure 5 in the first layer.

When a receptor sheet is placed on the surface of the ink layer of this recording medium and heated from the surface of the support using a thermal head, etc., the molten ink oozes out little by little onto the surface of the receptor sheet in balance with the force of penetrating into the fine network structure. The amount of colorant that bleeds out varies depending on the amount of heat energy applied by a thermal head, etc., so by controlling this heat energy, the amount of colorant transferred can be changed, and the gradation of the original image can be changed. It is possible to obtain a transferred image that faithfully reproduces a wide range of tones.

In the recording medium shown in FIG. 2, the first layer 3 is made up of a fine network structure 2 and an ink structure 5, and the heat-melting substance and colorant are present in both the first layer and the ink layer. The operation of this recording medium is the same as that shown in FIG.

The magnitude of heating energy during transfer varies depending on the type of each material and the thickness of the ink layer, and is a relative value.

As the support used in the present invention, conventionally known films and papers can be used as they are, such as films of relatively heat-resistant plastics such as polyester, polyamide, polycarbonate, triacetyl cellulose, nylon, and polyimide; Cellophane, condenser paper, parchment paper, etc. can be suitably used. The thickness of the support is preferably about 2 to 15 microns when considering a thermal head as a heat source for thermal transfer, but it is preferable to use a heat source that can selectively heat the thermal transfer ink layer, such as a laser beam. There are no particular restrictions in this case. In addition, when using a thermal head, the surface of the support that comes into contact with the thermal head is coated with a heat-resistant protective layer or a lubricant layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. By providing a layer, the heat resistance of the support can be improved, and it is also possible to use a support material that could not be used conventionally.

Although there are no particular limitations on the method for producing the heat-melting ink layer having the above-described structure, the following method is generally used.

The ink is prepared by mixing and dispersing the following colorant and heat-melting substance together with a suitable solvent using a dispersion device such as an attritor or a ball mill to form an ink dispersion or solution.

The thus prepared dispersion or solution is applied onto the first layer having the fine network structure and dried to form a second layer consisting of a hot melt ink layer.

To form the fine network structure in the first layer, a mixed dispersion containing an oil-based carrier immiscible with the resin is applied onto the support.

To form the first layer of the recording medium shown in Figure 2, a colorant, a heat-melting substance (which may be different from the ink layer), a resin dissolved in an organic solvent, a gradation control agent, etc. are mixed together. The resin is then uniformly dispersed using a mixer such as a ball mill, and an oil-based carrier immiscible with the resin is added to form a fine network structure, and the mixed and dispersed mixture is applied onto a support and dried.

In the dispersion liquid, a wetting agent is added to improve the dispersion of the mixture.
A dispersant or the like may be added. Also, if necessary, fillers commonly used in resin coatings of this type can be added. The resins constituting the fine network structure include vinyl chloride, vinyl acetate, vinylidene chloride, acrylic acid, methacrylic acid,
Thermoplastic resins such as single or copolymers of seven polymers selected from acrylic esters and methacrylic esters, and thermosetting resins such as phenol, furan, formaldehyde, urea, melamine, alkyd, unsaturated polyester, and epoxy. It is preferable to use

Specific examples of the coloring agent include the following.

Coloring dyes and color pigments may be used, but dyes can provide images with more preferable gradation.

Examples of such dyes include the following direct dyes, acid dyes, basic dyes, mordant dyes, sulfur dyes, vat dyes, azoic dyes, and oil dyes.

1) Direct dyes: Direct Sky Blue, Direct Black W, etc.

2) Acid dye: tartrazine, acid violet 6
B, Acid Fast Red 3G, etc.

3) Basic dyes: safranin, auramine, crystal violet, methylene blue, rhodamine B, Victoria blue B, etc.

4) Mordant dyes: Sunchromine Fast Alu MB1 Eriochrome Azurol B1 Alizarin Yellow B, etc.

5) Sulfur dye: Sulfur Brilliant Green 4G, etc.

6) Vat dyes: indanthremble, etc.

7) Azoic dyes: naphthol As, etc.

8) Oil-based dye Nigrosin, Spirit Black EB,
Varifast Orange 3206, Oil Black 215
, Butter Yellow, Sudan Blue ■, Oil Red B
10-Damin B et al.

These colorants not only have an excellent effect as a coloring agent, but also have excellent image quality, storage stability, and weather resistance.

It is sufficient that the particle size of these dyes is smaller than that of the pigment having a network structure, and it is preferable that the dye be in a dissolved state.

The gradation control agent of the present invention is a coloring agent that firmly exists in a microporous structure made of resin, is melted by heating with a thermal head, etc., and is wrapped in a retention agent that seeps out from the microporous structure. It seems to subtly control the amount of metastasis.

In other words, the gradation control agent has better wettability and compatibility with the microporous resin than the main component of the molten ink, the holding material, i.e., oil and low-melting point substances, and is firmly retained in the microporous structure. There is a need to It is thought that its presence serves to finely control the pore size of the porous structure to make it smaller.

Therefore, even when thermal energy is applied, the colorant itself is not transferred, but is retained in the porous structure, and functions to control the amount of colorant transferred, which is wrapped in the surrounding retaining material. I think that the.

In fact, it is possible to achieve a certain level of gradation even with just a microporous structure made of resin without using a gradation control agent, but the gradation can be improved by using a gradation control agent. .

As tone control agents, needle-like crystal pigments having a network structure or fine powders having a stone wall structure are used, and for the grains, azo compounds, phthalocyanine compounds, and perylene compounds are used.

Acicular crystal pigments are not limited to inorganic ones, but also include organic ones. Specific examples of these include ocher,
Yellow lead G, phthalocyanine blue, Lysol red, Bonmartone light, clay, acicular zinc oxide, 2,7-bis[2-hydroxy-3-(2-chlorophenylcarbamoyl)naphthalen-1-ylazo] = 9- Fluorenone, 4°, 4″-bis[2-hydroxy-3-(2,4-
Examples include dimethylphenyl)carbamoylnaphthalen-1-ylazo)-1,4-distyrylbenzene, but any material can be used as long as the crystals are acicular and the crystals are arranged in a network structure in the transfer layer. can.

The length of this needle-shaped crystal is about 0.3 to 3μ, the width and thickness are 0.
．． It has a diameter of 5μ or less.

The amount of the needle-like crystal pigment added is 0 per part by weight of the dye.
．． It is 5 to 10 parts by weight, preferably 1 to 5 parts by weight.

Fine powders with a stone wall structure include inorganic or organic fine powders, such as fine powders of metal oxides such as zinc oxide, tin oxide, aluminum oxide, aluminum, copper, etc.
Fine metal powders such as cobalt (sometimes in the form of metal foil), fine organic powders such as diatomaceous earth, molecular sieves, phenolic resins, and epoxy resins, fine carbon black powders, and combinations of two or more of these. You can give things and other things. All of these fine powders have excellent cohesiveness, but carbon black, which has particularly high cohesiveness, is most suitable as a fine powder.

Although carbon black is normally used as a black pigment, in the present invention, it does not play the role of a pigment but rather a medium for exuding the ink composition whose viscosity has been reduced by heat, and therefore, the ink It is not transferred onto the image-receiving sheet together with the composition and remains as it is on the substrate.

In the present invention, the particle size of the fine powder as described above is 0.01
Advantageously, the thickness is ˜200 μm.

If the particle size of the fine powder used is less than 0.01 μm, it will not be possible to expect the barrier effect, which is the first effect of using such a fine powder in the present invention.

Conversely, if the particle size of the fine powder used exceeds 200 μm, the resulting ink composition will be coarse and the print quality will deteriorate as the particle size increases. This fine powder forms a stone wall structure when applied to a support, but
No special means are required for the application method.

This fine powder forms a stone wall structure when applied to a support, but no special means are required for the application method.

The amount of the gradation control agent used is 1 to 80% by weight, preferably 5 to 40@14%, based on the total amount of the ink composition.
I'll go. The ratio to the resin (tone control agent amount/resin amount) is 0.05 to 2.0, preferably 0.1 to 1.
It is 0.

The oil-based carrier that facilitates the formation of a fine network structure may be any liquid, semi-solid, or heat-melting solid as long as it is incompatible with the above-mentioned thermoplastic resin and is non-volatile. used. Examples of liquids include cottonseed oil,
Animal and vegetable oils such as rapeseed oil and whale oil; or motor oil;
Mineral oils such as spindle oil and dynamo oil are used, and semi-solid carriers such as lanolin, petrolatum, lard and the like are used. Further, as the heat-melting substance that is solid at room temperature, heat-melting binders that constitute heat-melting ink in ordinary heat-sensitive transfer materials can be used, such as carnauba wax, paraffin wax, Sasol wax, and microcrystalline wax. , high grade waxes such as castor wax, nistearic acid, palmitic acid, lauric acid, aluminum stearate, lead stearate, barium stearate, zinc stearate, zinc palmitate, methyl hydroxy stearate, glycerol monohydroxy stearate, etc. Derivatives of fatty acids or their metal salts, esters, etc.: polyethylene, polypropylene, polyisobutylene, polyethylene wax, polyethylene oxide, polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer,
Thermoplastic resins made of olefins alone or copolymers, such as ethylene-vinyl acetate copolymers, or derivatives thereof, are used. These holding materials are used alone or in a mixture of two or more at a ratio of 50 to 200 parts per 100 parts of the thermoplastic resin constituting the thermal transfer layer.

In addition, in order to more strongly maintain the fine network structure and the network structure of the gradation control agent, it is also possible to provide an intermediate adhesive layer on the support in advance.

Examples of the intermediate adhesive layer include so-called plastic resins and plastic resins to which fillers are added.

The receiving sheet may basically be plain paper or synthetic paper, but if necessary, it may be made of the above resins, TiO2, silica, ZnO.
It is also possible to apply a filler containing fillers such as the like on plain paper to facilitate the transfer of the colorant.

In addition, by incorporating fillers such as titanium oxide, silica oxide, and zinc oxide into the second layer, and applying the fillers so that they are slightly exposed above the surface layer of the second layer, the second layer It is also possible to prevent scumming caused by direct contact of the colorant therein with the receiving paper.

Generally, it is better to apply the second layer in a manner that reduces the amount of colorant per unit area. The state in which the amount of colorant per unit area is reduced is as follows: 1) The coating thickness is made thinner than that of the first layer.

2) Decreasing the ratio of colorant/thermofusible substance, etc.

Hereinafter, the present invention will be specifically explained with reference to Examples. Note that all amounts (parts) of each component described in Examples are parts by weight.

Composition of coating liquid for fine network structure: Vinyl chloride, vinyl acetate copolymer, 10 parts modified lanolin oil, 3 parts dispersant
0.2 parts 2.7-bis[2-hydroxy-3-(2-
(chlorophenylcarbamoyl)naphthalen-1-ylazo]-9-fluorenone (gradation control agent) 1.2 parts Toluene 20 parts Methyl ethyl ketone 20 parts This mixture was sufficiently dispersed,
A coating liquid for fine network tissue is obtained. This coating liquid was applied to a thickness of 6 μm,
It is coated on the surface of a polyester film with a silicone resin heat-resistant layer on the back using a wire bar, and the drying temperature is 1.
It was dried at 00° C. for 1 minute to form a first layer (fine network) with a thickness of about 2 μm.

Ink composition Colored dye (Sudan Red 460) (manufactured by BASF) 10 parts carnauba wax 20 parts paraffin wax 20 parts liquid paraffin
2 parts The above components of the hot-melt ink are sufficiently dispersed in a ball mill at 68° C. with a liquid mixture of 70 parts of methyl ethyl ketone and 150 parts of toluene to obtain a hot-melt ink.

This coating liquid was applied to the surface of the first layer using a wire bar, and dried at a drying temperature of 100°C for 1 minute to a thickness of about 4 cm.
A μm molten ink layer was formed.

The thus obtained transfer medium with a two-layer structure was stacked so as to face the synthetic paper receiver, and an image was recorded from the surface of the transfer medium using a thermal head by varying the heating energy, as shown in Figure 3. A magenta image having the gradation characteristics as shown was obtained.

Example 2 Among the ink components in Example 1, the colored dye was replaced with Neoz
A transferred image was formed under all the same conditions as in Example 1 except that apon Blue 807 (manufactured by BASF) was used.

As a result, a cyan image having tone characteristics as shown in FIG. 3 was obtained.

Example 3 Among the ink components in Example 1, the colored dye was Neo
zapon Yel low 073 (B A S F
A transferred image was formed under all the same conditions as in Example 1, except that the transfer image was replaced with the following.

As a result, a yellow image having gradation characteristics as shown in FIG. 3 was obtained.

Comparative Example 1 Similar to the conventionally commercialized heat-melting type transfer recording medium, a recording medium having only a heat-melting ink layer (its composition is the same as Example 1) on the surface of the support was used. Transfer images were formed in the same manner.

The results are shown in FIG.

Comparative Example 2 A transfer image was formed using a recording medium having only the hot-melt ink layer of Example 2 on a support.

The results are shown in FIG.

Comparative Example 3 A transfer image was formed using a recording medium having only the hot melt ink layer of Example 3 on a support.

The results are shown in FIG.

Example 4 An example of this is the recording medium shown in FIG. 2 of the drawings.

Composition of first layer forming liquid: PVC/vinyl acetate copolymer: 10 parts: modified lanolin oil: 3 parts: dispersant
0.2 parts 2.7-bis[2-hydroxy-3-(2-chlorophenylcarbamoyl)naphthalen-1-ylazo[-9-fluorenone (gradation control agent) 1.2 parts toluene 20 parts methylethylkene 20 parts Neozapon Blu
e 807 (manufactured by BASF) 3 parts carnauba wax 1.5 parts paraffin wax
1.5 parts of the above components were mixed and dispersed to prepare a coating liquid for the first layer. This coating liquid was applied to the surface of the support using a wire bar, and dried at a drying temperature of 100° C. for 1 minute to form a first layer having a thickness of 4 μm.

Ink composition Neozapon Blue 807 (B A S F
Made>10 parts carnauba wax 20 parts paraffin wax 20 parts liquid paraffin
2 parts These components were sufficiently dispersed in a ball mill together with 70 parts of methyl ethyl ketone and 150 parts of toluene to prepare a coating liquid for a heat-melting ink layer.

- This coating liquid was applied onto the first layer using a wire bar and dried at a drying temperature of 100° C. for 1 minute to form an ink layer with a thickness of 1 μm.

The printing characteristics of the recording medium thus produced are as shown in FIG.

In order to obtain gradation using only the ink layer as in Comparative Examples 1 to 3, it appears that the coating thickness of the sheet should be adjusted, for example. If the thickness of the heat-melting ink layer of the current recording medium is increased from 1 μm to 5 μm, it will become as shown by the dotted line A in FIG. but,
Even if the coating thickness is varied between 1 and 5 .mu.m, neither the line slope nor the image density will be the same as in the present invention.

The case of the first layer alone does not work as in the present invention.

Effects As is clear from the above explanation, in the thermal transfer medium of the present invention, ink oozes out from between the fine networks and transfers to the receiving sheet surface depending on the magnitude of heating energy. By controlling this, it is possible to obtain a transferred image with excellent gradation expression (wide gradation reproduction).

Furthermore, this image has good storage stability, and full-color images can be obtained by selecting various dyes.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing the structure of a specific example of a thermal transfer recording medium of the present invention, and FIGS. 3 and 4 are gradation characteristics of a thermal transfer recording medium of an example of the present invention and a comparative example. This is a graph showing. DESCRIPTION OF SYMBOLS 1... Support body, 2... Fine network structure, 3... First
Layer, 4... Second layer (thermal melt ink layer), 5... Ink structure.

Claims (1)

[Claims] A heat-sensitive transfer recording comprising a first layer having a fine network structure made of resin on a support, and a heat-melt ink layer made of a heat-melt substance and a colorant that are solid at room temperature on top of the first layer. Medium.