JPH10297106A - Thermal transfer recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent phenomena such as bleeding and tailings in printing from occurring by specifying a residual solvent amount for a thermal transfer recording medium. SOLUTION: A residual solvent for the thermal transfer recording medium can be arbitrarily set by coating speed to be influenced by parameters such as a thermal transferable ink layer, the solid matter concentration of a heat- resistance lubrication layer, solvent species, solvent mixing ration and drying conditions. In addition, for the residual solvent amount, the smaller the batter, but it cannot be substantially 0 g/m<3> changes over time. The lower limit is not controllable, so that it is set substantially more than 0 g/m<3> and 400 g/m<3> or less. When the residual solvent amount is in excess, a blocking phenomenon occurs between the thermal transferable ink layer and the heat-resistant lubrication layer during the keeping of the solvent and print is unclear due to bleeding or tailings. Thus is possible to ensure the outstanding keeping quality of the thermal transfer recording medium and realize the clear print free from bleeding and tailings.

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 used when performing heating printing according to information by a heating means such as a thermal head.

[0002]

2. Description of the Related Art A thermal transfer recording medium in which a thermal transfer ink layer is provided on one surface of a support such as polyethylene terephthalate is heated from the back of the support by a thermal head, and the thermal transfer ink layer is transferred onto a transfer receiving body. In recent years, a thermal transfer method has been widely used.

As the above-mentioned thermal transfer recording medium, a method of mixing a coloring agent such as a pigment with a hot-melt material such as wax and forming a thermal-transferable ink layer on a substrate by a hot-melt coating method, or a method using an aqueous emulsion. Although a method of applying on a material is known, recently, a solvent coating method of dispersing and applying these materials in an organic solvent has been studied.

[0004]

When these thermal transfer recording media are used, if the amount of the residual solvent is too large, there occurs a problem that blocking occurs during storage and bleeding or tailing occurs in printing. No prior art is disclosed at this time.

[0005]

Means for Solving the Problems In order to solve such a problem, the present inventors have made intensive studies and as a result, the above object can be achieved by reducing the residual solvent of the thermal transfer recording medium to a specific amount or less. After confirming this, the present invention has been achieved. That is, the present invention provides (1) a thermal transfer recording medium having at least a heat-sensitive transferable ink layer on one surface of a support and a heat-resistant lubricating layer on the other surface of the support. residual solvent is more than 0 g / m ^3, a thermal transfer recording medium characterized in that it is 400 g / m ³ or less, (2) preferably a residual solvent ^{0g / m 3 ~350g / m 3} , more preferably 0 g / m The thermal transfer recording medium according to (1), which has a weight of ^{3 to} 300 g / m ³ . 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 transferable ink layer> The thermal transferable ink layer is composed of a colorant and a binder, and is softened and melted by heating to transfer to a transfer target. Pigments such as carbon black and various dyes can be used as the colorant. These pigments and dyes may be used alone or in combination of two or more. Further, the 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 or thermoplastic resins commonly 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. As the thermoplastic resins, known resins such as polyamide resins, acrylic resins, styrene-acrylic resins, polyester resins, rosin resins, and ethylene-vinyl acetate resins 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. If necessary, inorganic or organic fine particles can be added as an additive. For example, silica, talc, alumina,
Inorganic fine particles such as silicon dioxide, chromium oxide, calcium carbonate, barium sulfate, polyester, polyethylene,
Organic fine particles such as polypropylene and melamine resin are used, but are not limited thereto, and may be a mixture of two or more kinds. 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 paint, and it may be appropriately selected in consideration of the binder solubility, compatibility, dispersion stability, drying efficiency, and the like. For example, ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, alcohols such as isopropanol and butanol, dioxane, tetrahydrofuran, dimethylformamide and hexane , A diluent or solvent such as chlorine-substituted hydrocarbons, a single solvent or a mixture of any of these may be used, but a mixture 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. It is preferably used as a solvent. These organic solvents do not need to be 100% pure, and may contain impurities such as isomers, unreacted materials, by-products, decomposition products, oxides, and moisture in addition to the main components. Is 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. These organic solvents have a shear rate of 3000 sec using a cone plate type or double cylindrical type viscometer at the stage of application when the viscosity of the paint is applied.
It is used so that it becomes 5 to ¹⁰⁰ cp in c- ¹ . As the usage ratio of the solvent in the entire coating material, the concentration of the non-volatile
%, Preferably about 5 to 40% by weight. The solvent type, the mixing ratio, and the use amount are determined based on the type, specific surface area, particle size,
Further, it is preferable to determine the viscosity as high as possible in the above-mentioned viscosity range in consideration of the dilution stability of the paint and the like, in order to adjust the residual solvent. Further, the organic solvent addition operation is preferably performed stepwise in each step of the coating material production, and an operation such as a flow rate regulation and sequential addition with stirring in a tank or a gradual mixing with the coating material through piping is performed. Good to do. And if possible, it is more preferable to carry out filtration and / or dispersion treatment at the time of adding a solvent or at the time of dilution. By performing these operations, the stability of the coating material is improved, and the generation of aggregates and foreign substances can be suppressed. The thickness of the heat transferable ink layer can be determined in consideration of required transfer characteristics, and the preferred range is 0.1 to 10.0 μm, and more preferably 0.3 to 10.0 μm.
It is 5.0 μm. <Undercoat layer> Undercoat layer in the present invention, the role of adjusting the adhesive force between the heat transferable ink layer and the support,
That is, the thermal head plays a role of enhancing the releasability of the heat transferable ink layer by heating the back surface of the support.
Waxes or thermoplastic resins can be used for the undercoat layer without any particular limitation. As 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. As the thermoplastic resins, known resins such as polyamide resins, acrylic resins, styrene-acrylic resins, polyester resins, rosin resins, and ethylene-vinyl acetate resins can be used. If necessary, a coloring pigment or a coloring dye can also be used. The undercoat layer forming paint in the present invention is prepared by adding an organic solvent and / or water to each of the above components, similarly to the thermal transfer ink layer. The organic solvent used for preparing the coating material is not particularly limited, and may be appropriately selected in consideration of the solubility, compatibility, drying efficiency, and the like of waxes or resins. For example, methyl ethyl ketone, methyl isobutyl ketone, ketones such as 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. The undercoat layer has a thickness of 0.1 to 3.0 μm, preferably 0.3 to 2.5 μm.
μm, more preferably in the range of 0.5 to 2.0 μm. If the thickness is less than 0.1 μm, the effect of the undercoat layer does not appear, and if it exceeds 3.0 μm, the effect is saturated. <Heat-resistant lubrication layer> The heat-resistant lubrication layer is generally made of silicone resin,
A heat-resistant resin such as a melamine resin, an epoxy resin, a phenol resin, a fluororesin, a polyamide resin, a polyimide resin, a polyamideimide resin, a polyacetal resin, a polyurethane resin, and an acrylic resin is used. In addition, silicone oil,
Lubricants such as higher fatty acids, higher fatty acid esters, various surfactants, and fluorine compounds, or 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 a curing agent and other compounding agents in an appropriate solvent as required in addition to the heat-resistant resin and the lubricant. The solvent is the same as the organic solvent used for the heat transferable ink layer and the undercoat layer forming paint preparation, for example, methyl ethyl ketone,
Methyl isobutyl ketone, ketones such as cyclohexanone, aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, alcohols such as ethanol, isopropanol and butanol, dioxane, tetrahydrofuran, dimethylformamide, hexane, Diluents or solvents such as chlorine-substituted hydrocarbons may be mixed in a single solvent or in any ratio, but a mixed solvent containing a large amount of low-boiling solvents as long as the physical properties of the layer to be coated are not impaired It is preferable to use them. The thickness of the heat-resistant lubricating layer is in the range of 0.01 to 0.5 μm, preferably in the range of 0.01 to 0.3 μm. 0.01
If it is less than μm, the heat resistance is insufficient, and if it exceeds 0.5 μm, the coating film is shaved, and shaving powder adheres to the thermal head. <Support> Supports include, for example, paper sheets such as plain paper, condenser paper, laminated paper and coated paper, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefins, polyamides, Known films such as polyimide, polyamide imide, polysulfone cellulose triacetate, and polycarbonate can be used, and among these, PET, PEN, and aromatic polyamide are preferable. The thickness of the support is preferably 0.5 to 10.0 μm. 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> There is no particular limitation on the method of applying the paint prepared as described above to the support, and wire bar coating,
Any of river roll coating, gravure coating, and extrusion nozzle coating may be used. Among them, extrusion nozzle coating is most preferable. For example, when forming a multi-layer coating film including a heat transferable ink layer, a so-called wet-on-wet coating method in which an undercoat layer and a heat transferable ink layer are applied in a wet state on the support in a multilayered manner, or Applying a thermal transfer ink layer after applying and drying an undercoat layer
Any of the on-dry coating method and the like 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 conveyance speed is 50 to 7
A range of 00 m / min is preferred. Each coating is dried in a drying oven. A temperature gradient may be provided in the drying oven, and general air or an inert gas may be used as the gas atmosphere in the drying oven. Residual solvent If the amount of the residual solvent in the thermal transfer recording medium is too large, blocking occurs between the thermal transfer ink layer and the heat-resistant lubricating layer during storage, and bleeding or tailing occurs in printing, resulting in blurring. The residual solvent can be arbitrarily set according to the application speed, such as the solid content concentration of the thermal transfer ink layer and the heat-resistant lubricating layer, the type of solvent, the solvent mixing ratio, and the drying conditions. The smaller the amount of residual solvent, the better, but it does not substantially become 0 g / m ^3, and changes with time and the lower limit cannot be controlled. Therefore, the residual solvent of the thermal transfer recording medium is more than 0 g / m ³ and 400 g / m ^{3. 3} or less, preferably more than ^{0g / m 3, 350g / m} 3 or less, more preferably more than 0 g / m ^3, it is desirable that 300 g / m ³ or less. As a method for reducing the residual solvent, the method is not limited to these, but can be performed as follows. Select the drying temperature. If the drying temperature is too high, the molten components in the coating film are melted and fused to deteriorate the transfer characteristics. If the drying temperature is too low, a large amount of high boiling point solvent remains.
To 100 ° C, preferably 25 to 95 ° C, more preferably 25 to 80 ° C. Increase the proportion of fast-drying (low boiling) solvent in the solvent formulation. It is better to use a quick-drying solvent if it is only to dry it. It is advisable to use a large amount of quick-drying solvent in accordance with the degree of dispersion to be performed. For example, the fast-drying solvent accounts for 40 to 90% of the total solvent. If the amount of such a quick-drying solvent is too large (more than 90%), the ink layer will float due to bumping of the solvent during drying. Increase the solid content concentration of the thermal transfer ink layer. In general, the higher the solid content, the higher the viscosity of the coating. However, since the amount of the solvent in the coating is small, the residual solvent can be reduced.
However, on the other hand, if the solid content is too high, the suitability for application is deteriorated.
The solid content concentration is set as high as possible in a range where c- ¹ is 5 to 100 cp.

[0006]

EXAMPLES The present invention will be described more specifically with reference to examples, but it goes without saying that the present invention is not limited to these examples. Example <Thermal transferable ink layer> The following formulation was charged into a ball mill and dispersed for 24 hours to prepare a paint for forming a thermal transferable ink layer. 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 600 parts by weight Methyl ethyl ketone 600 parts by weight A 95% cut filtration accuracy of the obtained paint is 15.0 μm.
Circulating filtration was performed using a depth filter. <Undercoat layer> The following components were charged into a hypermixer and mixed and stirred for 1 hour to prepare a paint for forming an undercoat layer. 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.
Circulating filtration was performed using a depth filter. <Heat-resistant lubricating layer> The following components were charged into a hypermixer, and mixed and stirred for 1 hour to prepare a heat-resistant lubricating layer forming paint. 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. <Preparation of thermal transfer recording medium> A 3.5 μm polyethylene terephthalate support (K5, manufactured by Diafoil Hoechst)
80-3.5 W), an undercoat layer-forming paint is applied and dried on one surface of the undercoat layer to form a 0.8 μm-thick undercoat layer coating film, and the thermal transfer ink layer is formed on the undercoat layer. The coating for forming is applied and dried, and the film thickness is 1.8 μm.
m was formed. 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, thereby preparing a thermal transfer recording medium. By changing the respective conditions, samples having different amounts of residual solvent were produced in the thermal transfer recording medium. Table 1 shows the residual solvent and transfer characteristics of each sample. The characteristics were evaluated according to the following methods. <Residual solvent> The sample was sealed in a 20 ml vial bottle, and held at 120 ° C for 1 hour.
Spacer gas chromatograph (HH manufactured by Shimadzu Corporation)
S-2A, GC-9A). <Transfer characteristics> Each of the thermal transfer recording media obtained above was
It was cut to a width of 4 inches to obtain a thermal transfer recording medium (ink ribbon) for word processing. This ink ribbon is loaded in a cassette, and a word processor (WD-C50 manufactured by SHARP) is used.
In 0), printing was performed under the following conditions, and the transferability was visually determined. Printing density: 7 Printing speed: High speed A: No bleeding or tailing of printing is observed. ：: Almost no bleeding or tailing of the print was observed. Δ: Part of print bleeding or tailing was observed. ×: Bleeding or tailing of the print is observed throughout. What is bleeding: The outline of the print is blurred. Tail: A bleeding like a tail in the print profile along the head running direction <Storage characteristics (blocking)> An environment of 40 ° C. and 80% RH with the thermal transfer recording medium wound up. After standing for 24 hours, 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.

[0007]

[Table 1]

[0008]

According to the present invention, in a thermal transfer recording medium having a thermal transferable ink layer on one surface of a support, the residual solvent in the thermal transfer recording medium is controlled to be more than 0 g / m ³ and 400 g / m ³ or less, thereby preserving. It is possible to obtain a thermal transfer recording medium having excellent characteristics and capable of clear printing without bleeding or tailing.

[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.

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 side of a support and a heat-resistant lubricating layer on the other side of the support, wherein the residual solvent of the thermal transfer recording medium is 0 g. / M ³ , and 400 g / m ³ or less.