JPH0737192B2 - Thermal transfer recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for applying a heat to a hot-melt ink layer of a thermal recording medium by using a thermal head, a laser or the like to melt-transfer an image onto a receiving sheet. The present invention relates to a thermal transfer recording medium.

[Prior Art] Conventionally, as a heat-sensitive transfer recording medium, a transfer sheet having a heat-sublimable dye layer provided on a support or a heat-meltable ink layer containing a heat-fusible substance and a pigment as main components is provided on a support. Is known from the US Pat. No. 6,096,849, and these are used for forming an image on a receiving sheet by thermal printing.

However, the method using the thermal sublimation dye is excellent in expressing the gradation of the image (printing density varies depending on the amount of applied thermal energy), but has low thermal sensitivity and image storability. The method using a heat-fusible substance and a pigment is excellent in heat sensitivity and storability, but has a drawback that gradation expression is not sufficient.

[Purpose] The present invention aims to remedy the above-mentioned drawbacks of the prior art. It is an object of the present invention to provide a heat-sensitive transfer recording medium capable of obtaining a high-density image excellent in storability and gradation.

[Structure] As a result of earnest research in view of the above-mentioned object of the present invention, as a result of containing a heat-fusible substance which is solid at room temperature and a colorant in a fine porous structure made of a resin on a support of a thermal transfer recording medium 1
Of the hot-melt ink layer, and then, on the first hot-melt ink layer, a hot-melt ink layer containing components similar to those of the first hot-melt ink layer is formed.
Alternatively, it was found that by stacking two or more layers, a storability is excellent and a clear image with expanded gradation is obtained.

The heat-sensitive recording medium of the present invention will be described in detail below. First, in the first heat-melting ink layer closest to the support, the heat-melting ink component such as the colorant retained in the fine porous resin structure at room temperature is In the second hot-melt ink layer that was leached from the resin microporous structure by heating with a thermal head and moved to the second layer, and then firmly held in the microporous resin structure until then. Of the hot-melt component is combined with the ink component pushed up from the first layer and leaches out from the fine porous structure. Further, when a hot-melt ink layer is formed on this second layer, it is likewise melted by heat and finally leaches little by little onto the receiving sheet. The amount of colorant that oozes out varies depending on the amount of heat energy applied by the thermal head, etc., so if the amount of heat energy applied is controlled according to the desired image density, the amount of colorant transferred Can be changed, and an image that faithfully and widely expresses gradation can be obtained. Since there is a slight discontinuity at the interface between each hot-melt ink layer, and the amount of ink seeping out is suppressed here, a single layer has the same thickness as the laminated hot-melt ink layer of the present invention. It is possible to obtain a clear image with more expanded gradation compared to the case where the hot-melt ink layer is formed. The level of thermal energy applied during recording varies depending on the type of each material and the ink layer thickness, and is a relative value.

Hereinafter, the materials used for the thermal transfer recording medium of the present invention will be described. As the support used in the present invention, a conventionally known film or paper can be used as it is,
For example, polyester, polyamide, polycarbonate,
Films of relatively heat-resistant plastics such as triacetyl cellulose, nylon, polyimide, cellophane, condenser paper, and sulfuric acid paper can be preferably used. The thickness of the support is preferably about 2 to 15 μm when a thermal head is considered as a heat source for heat transfer, but a heat source capable of selectively heating a heat transferable ink layer such as laser light is used. There is no particular limitation in this case. When using a thermal head, silicone resin, fluororesin, or
The heat resistance of the support can be improved by providing a heat resistant protective layer made of a polyimide resin, an epoxy resin, a phenol resin, a melamine resin, nitrocellulose, or the like, or a support material that cannot be used conventionally is used. You can also

Further, the resin constituting the microporous structure is selected from vinyl chloride, vinyl acetate, vinylidene chloride, acrylic acid, methacrylic acid, acrylic acid ester and methacrylic acid ester in relation to the oily carrier as described later. Thermoplastic resins such as homo- or copolymers of monomers, phenol, furan, formaldehyde,
It is preferable to use a thermosetting resin such as urea, melamine, alkyd, unsaturated polyester and epoxy.

Examples of the colorant include a color dye and a color pigment, but the dye is more preferable because an image having gradation can be obtained.

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

1) Direct dyes: direct sky blue, direct black W, etc.

2) Acid dyes: Tartrazine, Acid Violet 6
B, Acid Fast Red 3G, etc.

3) Basic dyes: safranine, auramine, crystal violet, methylene blue, rhodamine B, Victoria blue B and the like.

4) Mordant dyes: Sanchromin First Blue MB, Eriochrome Azurol B, Alizarin Yellow B, etc.

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

6) Vat dye: Indanthrene blue, etc.

7) Izoc dye: Naphthol AS, etc.

8) Oily dyes: Nigrosine, Spirit Black EB, Varifast Orange 3206, Oil Black 215, Butter Yellow, Sudan Blue II, Oil Red B, Rhodamine B and the like.

9) Thermal sublimation disperse dye (can be used at sublimation temperature or lower because storage is important) (9-1) Monoazo disperse dye: Dispers First Yellow G, Dispers First Yellow 5G, Dispers First Yellow 5R, Di Spurs Red R etc.

(9-2) Anthraquinone type disperse dyes: Dispers First Violet OR, Dispers First Violet B, Dispers Blue Extra, Dispers First Brilliant Blue B and the like.

(9-3) Nitrodiphenylamine-based disperse dyes: Dispers First Yellow RR, Dispers First Yellow GL and the like.

The colorant of the present invention is not only excellent in coloring effect, but also excellent in storage stability of image quality and light resistance.

Further, gradation control as described below can be added to the microporous resin structure.

(1) Needle-shaped crystal pigments Not only inorganic pigments but also organic ones can be used. Specific examples of these include ocher, yellow lead G, phthalocyanine blue, resole red, and bon martone 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-dimethylphenyl) carbamoylnaphthalen-1-ylazo) -1,4-distyrylbenzene and the like can be mentioned, but the crystals are needle-shaped and are arranged in a reticulated structure in the transfer layer. Any substance can be adopted.

(2) Azo compound having the following chemical structural formula X (N = NY) n where X: diazonium salt residue Y: coupler residue n: 1,2,3 (3) Metal-free phthalocyanine and its derivative, metal phthalocyanine and its derivative (4) Perylene pigment For example, one having the following structural formula However, R ₁ : H, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, R ₂ , R ₃ : a substituted or unsubstituted alkyl group or alkoxy group, a halogen, a nitro group, n: 0, 1 2, 3, 4 As an oily carrier that facilitates the formation of porosity, a liquid is used as long as it is incompatible with the resin forming the microporous structure as described above and is non-volatile, Both semi-solid and heat-fusible solids are used. As a liquid carrier,
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, and semi-solid carriers such as lanolin,
Vaseline, lard, etc. are used.

Further, as the heat-melting substance that is solid at room temperature, a heat-melting binder that constitutes heat-melting ink in an ordinary heat-sensitive transfer medium can be used, and examples thereof include carnauba wax, paraffin wax, sazol wax, and microcrystalline. Waxes such as wax and castor wax; stearic acid, palmitic acid, lauric acid, aluminum stearate, lead stearate, barium stearate, zinc stearate, zinc palmitate, methyl hydroxystearate, glycerol monohydroxystearate, etc. Higher fatty acids or their metal salts, derivatives such as S; polyethylene, polypropylene, polyisobutylene, polyethylene wax, polyethylene oxide, polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-a Acrylic acid ethyl copolymer, ethylene - such as olefin homo- or copolymer or a thermoplastic resin comprising these derivatives such as vinyl acetate copolymer. These heat-fusible substances are used alone or in a mixture of two or more kinds in an amount of 50 to 200 parts with respect to 100 parts of the resin constituting the fine porous structure forming the heat-fusible ink layer.

In addition, it is possible to previously provide an intermediate adhesive layer on the support in order to strongly retain the network structure of the porous resin structure.

Examples of the intermediate adhesive layer include so-called plastic resins and plastic resins to which a filler is added.

The receiving sheet may be plain paper or synthetic paper, but if necessary, the above resin or a material containing a filler such as TiO ₂ , silica, or ZnO may be coated on plain paper to form a colorant. It is also possible to devise to facilitate the transfer.

The method for producing the heat-meltable ink layer having the above structure is not particularly limited, but is generally as follows. That is, a clathrate compound host and a colorant, a holding material such as a heat-soluble substance, and optionally a gradation control agent are mixed and dispersed with a suitable organic solvent using a dispersing device such as an attritor and a ball mill. Then, an ink dispersion liquid (or a solution) may be obtained.

Separately, a resin constituting a fine porous resin structure is dissolved in an organic solvent, and this is mixed with the ink dispersion liquid, and uniformly dispersed by a kneader such as a ball mill. Then, the obtained dispersion is applied onto a support and dried to obtain a hot-melt ink layer having a fine structure. A wetting agent, a dispersant, etc. may be added to the dispersion liquid in order to improve the dispersion of the above-mentioned colorant, gradation control agent, and holding material.

On the first heat-melting ink layer thus formed, one or more heat-melting ink layers are formed in the same manner as the layer. The gradation control agent is a desired component and can be used only in the upper layer.

Further, as another method of forming a porous resin structure, a resin forming a porous structure is incompatible, and a substance soluble in a solvent that does not dissolve the resin is kneaded together with the resin,
After coating on a support to form a resin layer, the substance may be dissolved in a solvent as described above to form a porous resin structure, and the porous structure may be filled with a thermal transfer ink.

The recording medium of the present invention described above can record a large number of sheets with one sheet.

Next, examples and comparative examples will be described. All parts are parts by weight.

Example 1 Sudan Red 460 (coloring dye) (manufactured by BASF) 10 parts Modified lanolin oil (holding material) 30 parts Carnauba wax (holding material) 20 parts Paraffin wax (holding material) 20 parts Dispersant 0.5 part Liquid paraffin 5 parts Methyl ethyl ketone 100 at 68 ℃
And 130 parts of toluene together with a ball mill for 48 hours to thoroughly disperse.

Then, a 20 wt% 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) was added to the above ink dispersion and dispersed by a ball mill for about 1 hour to prepare a coating material for the heat-sensitive transfer structure.

The coating material thus obtained was applied to the surface of a polyester film having a silicone resin heat-resistant layer provided on the back side having a thickness of 6 μm with a wire bar and dried at a drying temperature of 100 ° C. for 1 minute to give a thickness of 4 μm. To form a first hot melt ink layer.

Then, a second heat-melting ink layer having a thickness of 3 μm was formed on the first layer in the same manner as the layer to obtain a heat-sensitive transfer recording medium.

The ink layer side of the heat-sensitive transfer recording medium having the two-layered heat-melt ink layer obtained as described above is overlapped so as to face the synthetic paper that is the receptor, and the thermal head ( When an image was recorded at a resolution of 8 dots / mm) while changing the heating energy, a magenta image with gradation as shown in the figure was recorded.

Example 2 A thermal transfer recording medium was obtained in the same manner except that the coloring dye of Example 1 was changed to Neozapon Blue807 (manufactured by BASF), and image recording was carried out. As a result, a cyan color excellent in gradation as shown in the figure was obtained. Image was recorded.

Example 3 The colored dye of Example 1 was used as Neozapon Yellow073 (manufactured by BASF).
When a heat-sensitive transfer recording medium was obtained in the same manner as described above except that the above was changed to, an yellow image having excellent gradation as shown in the figure was recorded.

Comparative Example 1 Recording was carried out in the same manner as in Example using a commercially available thermal recording medium (manufactured by Fuji Kagaku Shimbun), and the results are shown in the figure.

Comparative Example 2 Thermal recording was performed in the same manner as in Example 1 except that the heat-melt ink layer was a single layer having a thickness of about 7 μm (the total thickness of the first layer and the second layer of Example 1). The medium was obtained. Recording was performed in the same manner as in Example 1 using the comparative product thus obtained, and the results shown in the figure were obtained. As is apparent from the results in the figure, the thermal recording medium according to this comparative example can obtain an enlarged gradation property as compared with the comparative example 1, but the gradation property is considerably inferior as compared with the embodiment.

[Effect] As is clear from the above results, the thermosensitive recording medium of the present invention can provide a clear image with excellent gradation, which could not be obtained by the conventional thermosensitive recording medium.

[Brief description of drawings]

The figure is a gradation characteristic curve of a thermal recording medium according to the present invention and a comparative example.

Claims (1)

[Claims] 1. A first heat-meltable ink layer containing a heat-meltable substance which is solid at room temperature and a colorant in a fine porous structure made of a resin is provided on a support, and then the first heat-meltable ink layer is provided. A heat-sensitive transfer recording medium, characterized in that one or more hot-melt ink layers containing the same components as the melt-ink layer are laminated on the melt-ink layer.