JPS6227186A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To enable to obtain high-density images with excellent gradation properties and, particularly, excellent heat sensitivity, by incorporating a heat- conductive material into a microporous structure of a resin in a heat-fusible ink layer. CONSTITUTION:A heat-fusible coloring agent is firmly held by a stone-wall-like structure or reticular structure of a particulate or fibrous substance in the microporous structure of a resin. The coloring agent is melted when being heated by a thermal head or the like, and the molten coloring agent oozes out through the stone-wall-like structure or reticular structure and then through the microporous resin structure onto a receiving sheet, little by little. The amount of the coloring agent caused to ooze out can be varied by controlling the thermal energy applied by the thermal head or the like, whereby an image with high fidelity of gradations and a wide range expression of gradation can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a heat-sensitive recording medium for obtaining a recorded image by melting and transferring a heat-melting ink layer 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 substance and pigment are provided on a support. It is used to form an image on a receiving sheet.

However, methods that use heat-sublimable dyes have excellent gradation expression in images, but have the disadvantages of low heat sensitivity and poor image storage stability; This method has excellent thermal sensitivity and storage stability, but has the drawback of not being able to express gradation.

Purpose 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 heat-sensitive transfer recording medium that has particularly excellent thermal sensitivity and can produce high-density images with excellent gradation.

Structure The present invention is a thermal transfer recording medium having a heat-fusible ink layer on a support, characterized in that the heat-fusible ink layer contains a thermally conductive material in a microporous structure made of resin. This is a thermal transfer recording medium.

In the present invention, the heat-melting colorant is firmly held by the stone wall structure or network structure made of powdery or fibrous substances in the microporous structure of the resin. This colorant is melted by heating with a thermal head etc.
It oozes out between the stone walls or network structure, then through the converging porous structure of the resin, and trickles onto the receiving sheet. The amount of colorant that oozes out varies depending on the amount of thermal energy applied by a thermal head, etc. By controlling the applied thermal energy, it is possible to change the amount of colorant transferred, and the gradation can be faithfully reproduced. It is possible to obtain an image that is clearly and broadly represented.

In addition, by using a thermally conductive substance for the powder or fibrous substance at this time, a thermally conductive stone wall structure or network structure is formed, and recording with higher sensitivity can be performed.

Here, the level of heating energy 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, polycarbonate, triacetyl cellulose, nylon, and polyimide, cellophane, Capacitor paper or parchment paper 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, a heat-resistant protective layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. should be provided on the surface of the support that comes into contact with the thermal head. This makes it possible to improve the heat resistance of the support, or 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. That is, a powder or fibrous substance made of a thermally conductive material, a coloring agent, and a holding material are mixed and dispersed together with a suitable organic solvent using a dispersion device such as an attritor or a ball mill. Ink dispersion 'f1.
(It may also be a solution). Separately, a solution of the resin dissolved in an organic solvent is obtained, mixed with the ink dispersion, and uniformly dispersed using a mixer such as a ball mill. Next, the obtained dispersion is coated with a roll coater, a bar coater, etc.
By applying the ink onto a support using a coating device such as a doctor blade and drying it, a hot-melt ink layer having a porous structure as described above can be obtained. A wetting agent, a dispersing agent, etc. may be added to the dispersion liquid in order to improve the dispersion of the above-mentioned thermally conductive powder or fibrous substance, colorant, and holding material. Further, if necessary, it is also possible to add LJII, which is commonly used in this type of resin paint. The resin constituting the microporous resin structure is selected from vinyl chloride, vinyl acetate, vinylidene chloride, acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester in relation to the oil-based carrier as described below. It is preferable to use thermoplastic resins such as monomers or copolymers, and thermosetting resins such as phenol, furan, formaldehyde, urea, melamine, alkyd, unsaturated polyester, and epoxy.

Alternatively, a substance that is incompatible with the resin that forms the porous structure and soluble in a solvent that does not dissolve the resin is kneaded with the resin, and is coated on the support to form a resin layer. A thermal transfer layer having the above structure can also be obtained by dissolving a substance in the above solvent to form a porous resin structure, and then filling the porous structure with a thermal transfer ink.

The thermally conductive powder or fibrous material that can be used in the present invention has a thermal conductivity of 10W at 273°K.
/ m, deg or more, and the following are examples. The value in parentheses is the thermal conductivity (W/m
, dec+).

80, (418), AI (238), Au (3
11), Be (230), graphite [crystal direction] (250), graphite [perpendicular to the crystal (80), Ca (98), Cr
(87), CIJ (400), l”e
(82) , In (2,'+) , Ir (148)
, Mo (140), Ni (90), Pb
(35), Pd (70), Pt (69>
, Sn (65), Ti (20), Zn (
120), brass (120), manganin (22)
), constanten (22), stainless steel (
14), N84CI (27) Combinations of two or more of these types, and others may also be mentioned.

In the case of the present invention, it does not play the role of a colorant, but rather a medium for leaching out the ink composition whose viscosity has been reduced by heat, so that it is not transferred onto the receiving sheet together with the ink composition. It remains on the base material as it is.

In the present invention, the particle size and fiber length of the powder as described above are advantageously between 0.01 and 200 μI. If the particle size and length used are less than 0.01 μl, the barrier effect, which is the first effect of the present invention, will not be expected. Conversely, if the particle size and length used exceed 200 μm, the resulting ink composition will be coarse and the print quality will deteriorate as the particle size increases. Further, the amount of the powdery or fibrous substance used as described above is 10 to 80% by weight, preferably 30 to 6% by weight, based on the total amount of the ink composition.
Advantageously, it is 0% by weight. The amount used can be arbitrarily selected within the above range depending on various factors such as transfer recording conditions, desired results, and other factors, as in the case of the low melting point compound mentioned above. It is possible.

This material forms a stone wall or network structure when applied to a support, but does not require any special means in the application method.

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, oil dyes, heat sublimable disperse dyes, and the like.

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 dye: Xancromine Fast Blue MB, Elio from Azurol B1 Alizarin Yellow B, etc.

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

6) Vat dyes: indanthremble, etc.

7) Azoic dyes: naphthol As, etc.

8) Oil dye: Nigrosine, Spirit Black EB,
Varifast Orange 3206, Oil Black 215
, Butter Yellow, Sudan Blue ■, Oil Red B
, Rhodamine B et al.

9) Heat-sublimable disperse dye (9-1) Monoazo disperse dye: Disbird's First Yellow G1 Disbird's First Yellow 5G,
Disbirds First Yellow SR, Disbirds Red R, etc.

(9-2) Anthraquinone disperse dye: Days Birds First Violet OR, Days Birds First Violet B1, Days Birds Blue Extra, Days Birds First Brilliant Blue B, etc.

(9-3) Nitrodiphenylamine-based disperse dyes: Disbird's Fast Yellow RR, Disbird's Fast Yellow GL, etc.

The particle size of these dyes may be smaller than the powdery or fibrous material having the stone wall or network structure, and is preferably in a dissolved state.

The colored fine particle pigment refers to one whose secondary particle size after sufficient dispersion is 1.0 μm or less, more preferably 0.5 μm or less.

Specific colored fine particle pigments are shown below. All of them are made by Hegist, and the color index numbers are not shown in parentheses.

Permanent Yellow GG, 2 (Pigment Yellow 17), Permanent Yellow DHG Transformer 02
(Pigment Yellow 12), Novo Balm Yellow HR03 (Pigment Yellow 83), Hansa Brilliant Yellow 5G 175), Permanent Lake Red LCLLO2 (Pigment Red 53:1), Novobalm Red HF4B (Pigment Red 187)
), Permanent Carmine F B B 02 (Pigment Red 146), Permanent Lupine 6
B <Pigment Red 57:1), Hosta Balm
Pink E Trance (Big Men 1- Red 122>,
reflex blue R50 (registration blue 61
) As the holding material, any liquid, semi-solid, or heat-melting solid may be used as long as it is incompatible with the above-mentioned thermoplastic resin and is nonvolatile. As liquid holding materials, for example, animal and vegetable oils such as cottonseed oil, rapeseed oil, and whale oil; or mineral oils such as motor oil, spindle oil, and dynamo oil are used; as semisolid carriers, for example, lanolin, petrolatum, lard, etc. are used. Further, as the solid holding material, a heat-melting binder that constitutes heat-melting ink in a normal heat-sensitive transfer material can be used, such as carnauba wax, paraffin wax, Sasol wax, microcrystalline wax, castor wax, etc. Waxes; stearic acid, palmitic acid, lauric acid, aluminum stearate, lead stearate,
Higher fatty acids such as barium stearate, zinc stearate, zinc balmitate, methyl hydroxystearate, glycerol monohydroxystearate, etc. or their metal salts, derivatives such as esters; polyethylene, polypropylene, polyisobutylene, polyethylene wax, polyethylene oxide, Thermoplastic resins made of olefins alone or copolymers, such as polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate polymer, or derivatives thereof. etc. are used. These holding materials are used alone or in a mixture of two or more at a ratio of 50 to 200 parts based on 1100 parts of the thermoplastic resin constituting the thermal transfer layer.

Other porous resin structure and powder stone wall structure or mm
In order to maintain the network structure more strongly, it is also possible to provide an intermediate adhesive layer on the support in advance.

Examples of the intermediate joint 1j 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, TiOz, 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.

Next, examples and comparative examples will be described. All parts indicate the heavy camellia part.

Example 1 Sudan Red 460 (@color dye) (manufactured by BΔSF) 10 parts graphite (UFG-5, manufactured by Showa Denko) 10 parts modified lanolin oil (retention material) 30 parts carnauba wax (retention material) 20 parts paraffin wax (retention material) Material) 20 parts dispersant 0.5 parts liquid paraffin 5 parts
Quantum dispersion was carried out for about 48 hours in a ball mill with a mixed solution of 100 parts of methane and 130 parts of toluene at .degree.

Next, a 20-layer solution of vinyl chloride-vinyl acetate copolymer resin solution (10 parts of resin, 20 parts of toluene, 20 parts of methyl ethyl ketone) was added.
300 parts were added to the above ink dispersion and dispersed in a ball mill for about 1 hour to prepare a coating of a thermal transfer composition.

This coating was applied to the surface of a 6 μm thick polyester film with a silicone resin heat-resistant layer on the back side using a wire bar, dried for 1 minute at a drying temperature of 100°C, and heated to a thickness of approximately 5 μm. A molten ink layer was formed.

The ink layer of the transfer medium thus obtained was stacked so as to face the synthetic paper receiver, and an image was recorded using a thermal head from the back side of the transfer medium by varying the heating energy, as shown in the table below. A magenta image was recorded.

Comparative Example 1 The image recording results for the same recording medium (layer thickness of 5 μm is the same) except that the graphite in the formulation in Example 1 was replaced with the i-pigment phthalocyanine blue are as follows:
Ru.

It can be seen that Example 1 has sufficient gradation reproduction and is almost the same as Comparative Example 1, but the thermal sensitivity is increased. Further, even after this recorded image was stored in a constant temperature bath at 60° C. for 50 hours, the density of the recorded image hardly changed.

Example 2 The graphite in Example 1 was replaced with copper powder and the coloring pigment was replaced with Sudan Blue 670 (manufactured by BASF).
All the images were recorded in the same way, and the image recording results are as shown in the table below.The results of Comparative Example 2 are as follows. It has been observed that thermal sensitivity is also improved.

Example 3 The graphite of Example 1 is made into stainless steel!
! Coarsely and colored dye Sudan Yellow 150 (
All procedures were carried out in the same manner, except that the paper was replaced with (manufactured by BASF), and as a result, a yellow image shown in the table below was recorded.

Similarly, the results of Comparative Example 3 are as follows, and from the above results, it can be seen that this example has good gradation reproduction and improved thermal sensitivity.

Effects As is clear from the above explanation, the thermal transfer medium of the present invention allows ink to flow between the porous resin structure and the material having a thermally conductive stone wall structure or network structure, depending on the amount of heating energy. It oozes out and transfers to the receiving sheet surface, so by controlling the heating energy during transfer,
A transferred image with excellent gradation expression (wide gradation reproduction) can be obtained, and since the stone wall or network structure is thermally conductive, thermal sensitivity is further improved. .

Claims (1)

[Claims] A thermal transfer recording medium having a heat-fusible ink layer on a support, characterized in that the heat-fusible ink layer contains a thermally conductive material in a microporous structure made of resin. Medium.