JPH10297107A - Thermal transfer recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer recording medium improved in running frictional coefficient and blocking characteristics. SOLUTION: This recording medium is so constituted as to have at least a thermal transferring ink layer on one side of a support and a heat resistant lubricating layer. In this case, a paint forming the thermal transferring ink layer consists of a coloring agent, waxes, thermoplastic resins and an organic solvent and an be obtained by mixing and dispersingly treating a solution, which is prepared by crushingly dissolving the waxes in the organic solvent, in a composition, which consists of the coloring agent, the thermoplastic resins and the organic solvent under a kneaded and dispersed state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium in which a heat transferable ink layer is provided on one side of a support and a heat resistant lubricating layer is provided on the other side.

[0002]

2. Description of the Related Art Conventionally, a thermal transfer recording medium having a thermally transferable ink layer provided on one surface of a support such as polyethylene terephthalate is heated from the back of the support by a thermal head to form a thermally fusible ink layer. A thermal transfer recording method of forming a printed image on a receptor by transferring (melt transfer type) or sublimating sublimable ink (sublimation transfer type) is widely used. The method for producing a thermal transfer recording medium, particularly a melt transfer type recording medium, includes the following method. A method in which a hot-melt binder is heated to a temperature higher than the softening point to disperse a colorant and then hot-melt coated. A method in which a hot-melt binder or a colorant is added as a water-based emulsion by adding a dispersant such as a surfactant. A solvent coating method in which a hot-melt binder, a colorant, and an organic solvent are mixed, dispersed by a disperser such as a ball mill, an attritor, or a sand mill and applied.

[0003]

In the above-mentioned conventional manufacturing method, although the printing quality is good, the physical properties, particularly the running friction coefficient and the blocking characteristics, are insufficient. Although measures such as adding a lubricant or the like to the thermal transfer ink layer or the heat-resistant lubricating layer and deteriorating the surface properties were taken, they were not satisfactory.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and found that after kneading and dispersing a composition comprising a colorant, a thermoplastic resin and an organic solvent, By mixing a solution obtained by mixing and dispersing waxes and an organic solvent, and further forming a heat transferable ink layer using a paint prepared by a production method of performing a dispersion treatment, the heat transfer recording medium is prepared. The inventors have found that the problem is solved, and arrived at the present invention. That is, the present invention relates to (1) a thermal transfer recording medium having at least a thermal transferable ink layer on one surface of a support and a heat-resistant lubricating layer on the other surface of the support. The paint to be formed is composed of a coloring agent, a wax, a thermoplastic resin and an organic solvent, and after kneading and dispersing a composition comprising the coloring agent, the thermoplastic resin and the organic solvent, the wax is added to the composition in an organic solvent. And a dispersion obtained by mixing and dispersing a solution obtained by pulverizing and dissolving the mixture into a thermal transfer recording medium.

The present invention will be described in detail below. The present invention is applicable to the production of a thermal transfer recording medium having at least a thermal transferable ink layer on one surface of a support and a heat-resistant lubricating layer on the other surface. FIG. 1 shows an example of such a configuration. In the thermal transfer recording medium shown in FIG. 1A, a thermal transferable ink layer 2 is provided on one surface of a support 1, and a heat-resistant lubricating layer 3 is provided on the other surface. The thermal transferable ink layer 2 may be a single layer or a multilayer of two or more layers as necessary. FIG. 1B shows a configuration of a thermal transfer recording medium in which an undercoat layer 4 is provided between a thermal transferable ink layer 2 and a support 1. <Thermal transfer type ink layer> The melt transfer type ink layer is composed of a colorant and a binder, and is softened and melted by heating to transfer to a transfer target. As the colorant, a pigment such as carbon black can be used. A color tone may be adjusted by mixing an extender or a white pigment. Further, the surface of the colorant may be treated with a surfactant, a silane coupling agent or the like in order to improve the dispersibility in the binder. As the binder, waxes and thermoplastic resins generally used for the thermal transfer ink layer can be used without any particular limitation. As the waxes, carnauba wax, candelilla wax, montan wax, microcrystalline wax, paraffin wax, wood wax, synthetic fat wax and the like can be used according to various uses. Known thermoplastic resins such as ethylene-vinyl acetate resin, polyamide resin, acrylic resin, styrene-acryl resin, polyester resin, and rosin resin can be used. The binder is preferably contained in an amount of 50 to 500 parts by weight based on 100 parts by weight of the colorant. The coating composition for forming a thermal transfer ink layer in the present invention is prepared by adding an organic solvent to each of the above components. There is no particular limitation on the solvent used for preparing the coating material, and it may be appropriately selected in consideration of the solubility, compatibility, dispersion stability, drying efficiency, etc. of the binder, and for example, ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone ,
Diluents or solvents such as aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, alcohols such as isopropanol and butanol, dioxane, tetrahydrofuran, dimethylformamide, hexane and chlorine-substituted hydrocarbons. , A single solvent or a mixture thereof in any ratio, but it is preferable to use a mixed solvent containing a large amount of a solvent having a low boiling point as long as the physical properties of the layer to be coated are not impaired. These organic solvents do not need to be 100% pure, but contain isomers,
Although impurities such as unreacted products, by-products, decomposition products, oxides, and moisture may be contained, these impurities are preferably 5% by weight or less, more preferably 3% by weight or less. If the amount of impurities is large, the dispersibility of the paint, the storage stability of the paint, and the storage characteristics of the medium are adversely affected. FIG. 2 shows a manufacturing process of the thermal transfer ink layer. A step of dissolving thermoplastic resins, a step of dissolving and dispersing waxes in an organic solvent, a step of kneading a resin solution and a color pigment, a step of dispersing a kneaded slurry, and adding a wax solution to the dispersed slurry. It further comprises a dispersing step, a filter circulation step and a coating step. The resin solution is prepared by dissolving a thermoplastic resin in an organic solvent. The ratio of the thermoplastic resin to the organic solvent, the ratio of the thermoplastic resin / organic solvent is 10/100 to 80 by weight.
/ 100. With such a ratio, it is easy to prepare a uniform solution. On the other hand, when this ratio is large, the thermoplastic resin is difficult to dissolve, and it is easy to prepare a uniform solution. On the other hand, when this ratio is small, the viscosity of the kneaded material during kneading, which is a subsequent step, becomes low, and a desired shearing force cannot be obtained. The liquid temperature during dissolution is preferably from 20 to 100C. In the kneading process,
A solid content such as a color pigment is kneaded with the resin solution. The solid content concentration of the kneaded material is preferably 40 to 90% by weight, more preferably 50 to 80% by weight. When the solid content is too low, the viscosity at the time of kneading becomes low, so that a sufficient shearing force cannot be obtained, and the solid content tends to be insufficiently dispersed. On the other hand, when the solid content concentration is too high, the viscosity at the time of kneading becomes too high, and it becomes difficult to obtain an appropriate shearing force. For kneading, open kneader, pressure kneader, high-speed mixer, continuous kneader, 3
It is preferable to use one having a strong kneading force such as a roll mill or a roll mill. In the dispersing step, a solid content such as a coloring pigment in the kneaded material is dispersed. The solid content concentration of the dispersion is 10 to 60% by weight, more preferably 15 to 50% by weight. If the solid content concentration is too low, the viscosity at the time of dispersion becomes low, and the solid content tends to be insufficiently dispersed. On the other hand, when the solid content concentration is too high, the viscosity at the time of dispersion becomes too high, and the dispersion of the solid content also tends to be insufficient. For dispersion, it is preferable to use a media stirring type disperser such as a sand grinder mill, a pin mill, and an agitator mill. For these dispersers, it is desirable to use a dispersion medium having a high specific gravity, and ceramic media such as zirconia is preferable.However, conventionally used glass beads, metal beads, alumina beads, and the like may also be used depending on the composition. Selectable for use. Subsequently, a wax solution is added to the dispersion, mixed, and further dispersed. The wax solution uses an organic solvent as a solvent to disperse waxes. At this time, depending on the type of the solvent used, the solubility of the wax may be low and may not be sufficiently dissolved. However, if the wax is not dissolved, the wax is sufficiently pulverized into fine particles to form a uniform solution, and there is no practical problem. For preparing the wax solution, a disperser such as a ball mill or an attritor is preferable. The solid concentration of the wax solution is preferably 5 to 30% by weight. For the dispersion after mixing the wax solution, it is preferable to use the above-mentioned media stirring type disperser. The solid content concentration of the paint is preferably 5 to 40% by weight, more preferably 10 to 30% by weight. If the solid content is too low or too high, it is difficult to form a uniform coating film. The solid content concentration may be set so that the viscosity of the paint becomes 5 to ¹⁰⁰ cp at a shear rate of 3000 sec to ¹ using a cone plate type or double cylindrical type viscometer at the application stage. It is preferable that the viscosity is appropriately determined in consideration of the type, the specific surface area, the particle size, the dilution stability of the coating material, and the like. In the filtration step, an object to be captured such as a non-dispersed color pigment such as carbon black, a pigment re-aggregate, an undissolved binder and a gelled binder is captured with a filter with high accuracy. For this reason, in the paint finally obtained, a longitudinal streak at the time of application caused by the inclusion of the trapped object and being present as a foreign substance in the coating film, a decrease in the yield due to a missing coating or a swelling, etc., are reduced. It can be greatly improved. In addition, the properties of the coating film are improved, and the physical properties of the coating film are improved. Further, carbon black used as a color pigment in the thermal transfer ink layer is known to have extremely poor dispersibility, but upon filtration by such a filtration means, a strong shearing force acts on the paint. Therefore, the dispersibility is significantly improved. For this reason, the thermal transfer characteristics are further improved. The 95% cut filtration accuracy of the filter in the filtration step is 30 μm or less, preferably 25 μm or less. If it exceeds 30 μm, the above effects cannot be obtained. The thickness of the thermal transfer ink layer can be determined in consideration of the required transfer characteristics, and the preferred range is 0.1 to 10.0 μm, and more preferably 0.3 to 5.0 μm.

<Undercoat layer> In the present invention, the undercoat layer controls the adhesive force between the melt transfer type ink layer and the support, that is, the undercoat layer forms the melt transfer type ink layer by heating the back surface of the support with a thermal head. It plays a role in enhancing the releasability. Waxes or thermoplastic resins can be used for the undercoat layer without any particular limitation. As the waxes, carnauba wax, candelilla wax, montan wax, microcrystalline wax, paraffin wax, wood wax, synthetic fat wax and the like can be used according to various uses. Known thermoplastic resins such as ethylene-vinyl acetate resin, polyamide resin, acrylic resin, styrene-acryl resin, polyester resin, and rosin resin can be used. If necessary, a coloring pigment or a coloring dye can also be used. The paint for forming an undercoat layer in the present invention is prepared by adding an organic solvent and / or water to each of the above components. There is no particular limitation on the organic solvent used for preparing the coating material, and it may be appropriately selected in consideration of the solubility, compatibility, drying efficiency, and the like of waxes or resins, for example, ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. , Toluene, xylene and other aromatic hydrocarbons, ethyl acetate, esters such as butyl acetate, isopropanol, alcohols such as butanol, dioxane, tetrahydrofuran,
Diluents or solvents such as dimethylformamide, hexane, and chlorine-substituted hydrocarbons may be used as a single solvent or as a mixture of any of these solvents. It is preferable to use as a mixed solvent with a large amount. The thickness of the undercoat layer is
0.1-3.0 μm, preferably 0.3-2.5 μm,
More preferably, it is in the range of 0.5 to 2.0 μm. 0.
If the thickness is less than 1 μm, the effect of the undercoat layer does not appear, and
If it exceeds 0 μm, the effect is saturated.

<Heat-resistant lubricating layer> The heat-resistant lubricating layer is generally made of silicone resin, epoxy resin, melamine resin, phenol resin, fluorine resin, polyamide resin, polyimide resin,
Polyamide-imide resin, polyvinyl acetal resin,
And a heat-resistant resin such as a cellulose resin. In addition, silicone oil,
Higher fatty acids, higher fatty acid esters, various surfactants, lubricants such as fluorine compounds, melamine resin particles, silicone resin particles, and the like may be blended. The heat-resistant lubricating layer can be formed by applying and drying a material obtained by dissolving and dispersing the above-mentioned heat-resistant resin, lubricant, and if necessary, a curing agent and other compounding agents in an appropriate solvent. The solvent is the same as the organic solvent used for preparing the thermal transfer ink layer and the undercoat layer-forming coating material, for example, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, toluene, aromatic hydrocarbons such as xylene, Diluents or solvents such as esters such as ethyl acetate and butyl acetate, alcohols such as ethanol, isopropanol and butanol, dioxane, tetrahydrofuran, dimethylformamide, hexane, and chlorinated hydrocarbons, in a single solvent or in any ratio However, it is preferable to use a mixed solvent containing a large amount of a low boiling point solvent as long as the physical properties of the layer to be applied are not impaired. The thickness of the heat-resistant lubricating layer is in the range of 0.01 to 0.5 μm, preferably 0.1 μm.
The range of 01 to 0.3 μm is preferred. If it is less than 0.01 μm, the heat resistance is insufficient, and if it exceeds 0.5 μm, the coating film is shaved and the shaved powder adheres to the thermal head.

<Support> For the support, for example, plain paper,
Paper sheets such as condenser paper, laminated paper and coated paper, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefins, polyamides, polyimides, polyamide imides, polysulfone cellulose triacetate, and polycarbonates. And PET, PEN, and aromatic polyamide are preferable among them. The thickness of the support is 0.5 to 10.0 μm
It is preferred that If it is less than 0.5 μm, the strength of the thermal transfer recording medium is insufficient, and if it exceeds 10.0 μm, heat conduction from the thermal head deteriorates and thermal transfer characteristics deteriorate.

<Coating Method> The method of applying the coating material prepared as described above to a support is not particularly limited, and any of wire bar coating, reverse coating, gravure coating, or extrusion nozzle coating may be used. . Among them, extrusion nozzle coating is most preferable. For example, when a multi-layer coating film including a heat transferable ink layer is formed, a so-called wet coating method in which an undercoat layer and a heat transferable ink layer are overlaid on a support in a wet state.
Either an on-wet coating method or a so-called wet-on-dry coating method in which an undercoat layer is applied and dried followed by application of a thermal transferable ink layer can be used. The heat-resistant lubricating layer may be applied before or after the undercoat layer and the thermal transfer ink layer are applied, or may be applied simultaneously. The support transfer speed is 50
A range of -700 m / min is preferred. Each coating is dried in a drying oven. The drying temperature is in the range of 25 to 100C, preferably 25 to 90C, more preferably 25 to 80C.
What is necessary is just to select suitably. If the temperature is lower than 25 ° C., drying becomes insufficient. If the temperature is higher than 100 ° C., melting and fusing of a molten component in the coating film occur, and transfer characteristics deteriorate. Further, a temperature gradient may be provided in the drying furnace, and general air or an inert gas may be used as a gas atmosphere in the drying furnace.

[0010]

EXAMPLES The present invention will be described below with reference to examples, but it goes without saying that the present invention is not limited to these examples. <Thermal transferable ink layer> (1) (Example) The following formulation was charged into a hyper mixer, and the liquid temperature was set to 80.
The mixture was heated to ℃ and dissolved by stirring. This solution is referred to as a resin solution. 130 parts by weight of ethylene vinyl acetate copolymer (manufactured by Sumitomo Chemical Co., Ltd .: KF-11) Toluene 520 parts by weight The following components were charged into a pressure kneader and kneaded for 2 hours. 100 parts by weight of carbon black (manufactured by Mitsubishi Chemical Corporation: # 25B) 100 parts by weight of resin solution To the slurry after kneading, 550 parts by weight of the above resin solution was added, and then dispersion treatment was performed using a sand mill. Carnauba wax (manufactured by Cera Rica NODA) 20 parts by weight Paraffin wax (manufactured by Nippon Seiwa Co., Ltd .: HNP-9) 50 parts by weight Toluene 340 parts by weight Methyl ethyl ketone 340 parts by weight The above composition was charged into a ball mill and mixed and dispersed for 24 hours. This was performed to obtain a wax solution. 750 parts by weight of the wax solution was added to 750 parts by weight of the slurry after the dispersion treatment, and the mixture was further mixed and further subjected to a dispersion treatment by a sand mill. The obtained paint was circulated and filtered using a depth filter having a 95% cut filtration accuracy of 15.0 μm to prepare a heat transferable ink layer forming paint. (2) (Comparative Example) Conventional Dispersion Method The following compound was charged into a ball mill and dispersed for 24 hours. Carbon black (Mitsubishi Chemical Corporation: # 25B) 100 parts by weight Carnauba wax (Ceralica NODA) 20 parts by weight Paraffin wax (Nippon Seiwa Co., Ltd .: HNP-9) 50 parts by weight Ethylene vinyl acetate copolymer (Sumitomo) KF-11) 130 parts by weight Toluene 860 parts by weight Methyl ethyl ketone 340 parts by weight A 95% cut filtration accuracy of the obtained paint is 15.0 μm.
The resulting mixture was subjected to circulation filtration using a depth filter, to prepare a heat transferable ink forming paint. <Undercoat layer> The following components were charged into a hypermixer and mixed and stirred for 1 hour. Water-based wax emulsion (manufactured by Konishi Corporation: WE, solid content concentration = 40 wt%) 50 parts by weight Isopropyl alcohol 50 parts by weight A 95% cut filtration accuracy of the obtained paint is 15.0 μm.
Was circulated and filtered using a depth filter of No. 1 to prepare a coating material for forming an undercoat layer. <Heat-resistant lubricating layer> The following components were charged into a hypermixer and mixed and stirred for 1 hour. Polyamideimide resin (manufactured by Toyobo Co., Ltd .: HR-14ET) 1 part by weight Silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF-860) 0.07 part by weight Ethanol 50 parts by weight Toluene 50 parts by weight The obtained paint is 95% Circulation filtration was performed using a depth filter having a cut filtration accuracy of 5.0 μm to prepare a coating for forming a heat-resistant lubricating layer. 3.5 μm polyethylene terephthalate support (manufactured by Diafoil Hoechst: K58)
0-3.5 W) on one surface of the undercoat layer-forming coating material, and dried to form an undercoat layer film having a thickness of 0.8 μm. The coating material for forming a thermal transfer ink layer was applied on the undercoat layer and dried to form a coating film having a thickness of 1.8 μm. The coating material for forming a heat-resistant lubricating layer was applied on the other surface of the support and dried to form a coating film having a thickness of 0.1 μm. The coated raw roll was cut into a 1/4 inch width to obtain a thermal transfer recording medium (ink ribbon) for word processing.

Table 1 shows the characteristics of the obtained thermal transfer recording medium. The evaluation method of each characteristic is as follows. <Blocking> With the thermal transfer recording medium wound up,
After standing for 24 hours in an environment of 40 ° C. and 80% RH, blocking evaluation between the heat transferable ink layer and the heat-resistant lubricating layer was performed according to the following criteria. ：: No sticking between the thermal transfer ink layer and the heat-resistant lubricating layer. X: NG state because the heat transferable ink layer and the heat-resistant lubricating layer were stuck. <Coefficient of friction> A tape friction tester manufactured by Shimada Giken Co., Ltd. was used. The diameter of the thermal transfer ink layer side of the thermal transfer recording medium is 4
The tape was wound 180 ° so as to be in contact with a stainless steel pin having a diameter of 1.0 mm, a constant back tension was applied to the tape, and an arbitrary constant portion of 50 mm was reciprocated 50 times at a running speed of 11 mm / sec. The coefficient of friction was determined. <Table 1> Blocking Example of running friction coefficient ○ 0.30 Comparative example × 0.55 As shown in Table 1 above, the examples are superior in both the blocking characteristics and the running friction coefficient. This is because kneading and dispersing with a thermoplastic resin first, and then adding waxes, the resin acting as an adhesive component is first adsorbed to the coloring pigment, and the presence of waxes around it, blocking properties and The running friction coefficient has been improved.

[0012]

By producing a thermal transfer recording medium according to the production method of the present invention, the physical properties, particularly the running friction coefficient and the blocking characteristics can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a thermal transfer recording medium, in which (a) has no undercoat layer and (b) has an undercoat layer.

FIG. 2 is a manufacturing process diagram of a thermal transferable ink layer of the present invention.

Continuation of front page (72) Inventor Hiroshi Nakajima 1-1-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation

Claims (1)

[Claims] 1. A thermal transfer recording medium having at least a thermal transferable ink layer on one surface of a support and a heat-resistant lubricating layer on the other surface of the support, wherein a coating material for forming the thermal transferable ink layer is provided. A composition comprising a colorant, a wax, a thermoplastic resin and an organic solvent, and a composition comprising a colorant, a thermoplastic resin and an organic solvent were kneaded and dispersed, and then, in this composition, the waxes were pulverized and dissolved in an organic solvent. A thermal transfer recording medium, which is a paint obtained by mixing a solution and further performing a dispersion treatment.