JPH08224977A - Thermal transfer recording sheet - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a thermal transfer recording sheet having extremely excellent head durability without causing corrosion of the thermal head even after high-speed recording for a long period of time. SOLUTION: In a thermal transfer recording sheet in which a heat transferable coloring material layer is provided on one surface of a base film and a heat resistant slipping layer is provided on the other surface, an alkali metal ion and an alkali contained in the heat resistant slipping layer are contained. A thermal transfer recording sheet having a total concentration of earth metal ions of 4 μg / cm ² or less.

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 sheet, and more particularly to an OA for printers, facsimiles, copiers and the like.
The present invention relates to a thermal transfer recording sheet that can be advantageously used for color recording in terminals and color recording of television images.

[0002]

Various methods such as electrophotography, ink jet, and heat-sensitive transfer recording have been studied for color recording, but the heat-sensitive transfer method is the maintainability of the apparatus, the ease of operation, and the low price of consumables. In terms of the above, it is more advantageous than other methods. In the thermal transfer recording method, the image receiver is placed on the ink-coated surface of the thermal transfer recording sheet coated with ink containing a color material, and the back surface of the thermal transfer recording sheet is heated by a heat source such as a thermal head. Recording is performed by transferring the color material inside to the image receptor.
Such methods include a melt-type transfer recording method using a heat-meltable ink and a sublimation type transfer recording method using an ink containing a sublimable dye.

[0003]

However, in this type of heat-sensitive transfer recording method, the heat transfer recording sheet is heated to the high temperature of the thermal head, so that the heat resistance of the base film of the heat transfer recording sheet is insufficient. In addition, the base film is fused to the thermal head, and the fusion causes the head to run poorly, causing a sticking phenomenon and a sheet wrinkle or break phenomenon, which makes normal recording impossible. Therefore, conventionally, it has been proposed to provide a protective film of various heat resistant resins in order to improve the heat resistance of the base film (Japanese Patent Laid-Open Nos. 55-7467 and 57-741).
In addition, it has been proposed to add heat-resistant fine particles, a lubricant, a surfactant and the like to the above protective layer in order to further improve the running property (JP-A-56-15).
5794, JP-A-60-184883 and JP-A-3-42282).

However, recently, in the recording method of this system, in order to increase the recording speed, higher energy is applied to the thermal head than in the past, so that the durability of the head becomes more important. There is. Although various factors that deteriorate the function of the head have been recognized, among them, the factors of the corrosion phenomenon are complicated and there is no clear countermeasure, and it is becoming the most serious problem.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to obtain a thermal transfer recording sheet having excellent head durability, and as a result, have found that an alkali contained in the thermal transfer recording sheet, particularly in the heat resistant slipping layer. Metal and alkaline earth metal ions are the main causes of corrosion, and by suppressing the sum of these ions within a certain range, head corrosion does not occur and a very good thermal transfer recording sheet can be obtained. They have found the present invention and reached the present invention.

Further, by controlling the fluorine contained in the thermal transfer recording sheet, particularly in the heat resistant slipping layer, to a certain range or less, it is possible to obtain a good thermal transfer recording sheet in which head corrosion is unlikely to occur. I found it. The thermal head used for thermal transfer recording is generally a thin film type thermal head, and the head heating portion has the structure shown in FIG. 1, for example.

That is, in the head heating portion, the glaze layer 2 is provided on the heat dissipation substrate 1 made of alumina ceramic. The glaze layer 2 is a layer that functions as a heat retaining layer and is usually made of glass. On the glaze layer 2, as a heating resistor layer 3, a nitride of a highly stable metal material such as Ni.Cr (nichrome) or tantalum, or a cermet (Ta-
SiO _2, Cr-SiO ₂ or the like) is provided. On top of this is provided an electrical conductor 4, i.e. this is an electrode, usually made of aluminium. On top of that is a resistor protection layer 5, which consists of oxygen-blocking SiO ₂ . On top of that, as a wear resistant layer 6, Ta ₂
A substance having good wear resistance such as O ₅ , SiC, and SiN is provided.

If the color sheet, especially the heat resistant slipping layer of the color sheet, contains an ionic substance such as Na, K, Mg or Ca, the electrode of the thermal head is negatively charged. As a result, cations such as Na are sucked through the wear resistant layer or the protective layer, so that cracks or pinholes are generated in the wear resistant layer or the protective layer, and corrosion such as electrode oxidation occurs. It is thought that it will be.

Further, if the color sheet contains fluorine, it will corrode the glass of the resistor protective layer and glaze layer of the thermal head, and in this case as well, it is considered that corrosion of the thermal head is induced. The object of the present invention is to drive the thermal head under severe recording conditions,
It is to provide a thermal transfer recording sheet that does not corrode the head.

That is, the gist of the present invention is a heat transfer recording sheet having a heat transferable coloring material layer provided on one surface of a base film and a heat resistant slipping layer on the other surface, and the heat resistant slipping layer is included in the heat transfer recording sheet. The thermal transfer recording sheet is characterized in that the total concentration of alkali metal and alkaline earth metal is 4 μg / cm ² or less. Hereinafter, the present invention will be described in detail.

The heat resistant slipping layer of the present invention usually comprises a binder resin, fine particles, and other additives such as a lubricant. As the binder resin, a thermosetting, photocurable or thermoplastic binder resin is used. Examples of the thermosetting resin include crosslinked products of an isocyanate and a resin containing active hydrogen such as ethyl cellulose resin, cellulose acetate resin, polyvinyl alcohol resin, polyvinyl acetal resin, and polyvinyl butyral resin. Examples of the photocurable resin include polyester acrylate, epoxy acrylate, and polyol acrylate. As the thermoplastic resin, a normal thermoplastic resin having a glass transition temperature of 50 ° C. or higher can be used, and examples thereof include acrylic resin, vinyl chloride copolymer, acrylonitrile-styrene copolymer, polycarbonate resin, polyester resin, Polyvinyl butyral resin,
Examples thereof include polyacetal resin.

Examples of the fine particles include inorganic particles such as silica, alumina and titanium oxide, and organic particles such as silicone resin, urea resin and benzoguanamine resin. As the lubricant, various modified silicone oils, phosphate ester type surfactants and the like are used. As described above, in general, the composition of the heat resistant slipping layer includes a thermosetting, photocurable or thermoplastic binder resin, fine particles, a lubricant, and an interface for the purpose of enhancing running property, antistatic property or cleaning property. An activator, an antistatic agent, or the like is blended, and among these, a cation such as an alkali metal ion or an alkaline earth metal ion is usually contained as an impurity or a counter ion. Fluorine may be contained depending on the inorganic particles and the surfactant.

However, the present inventors have found that when such cations and fluorine are present in the thermal transfer recording sheet, especially on the surface of the heat resistant slipping layer in contact with the thermal head,
It has been found that, particularly under high-speed recording conditions in which high energy is applied for a short time, they are easily diffused and absorbed in the protective film of the thermal head, and eventually reach the electrode portion and cause corrosion. To eliminate these cations,
By performing a refining process or selecting a raw material containing a low amount of these cations, the durability of the thermal head against corrosion can be significantly increased. For fluorine,
It is possible to control by selecting a material having a low fluorine content as the inorganic particles or the surfactant, and it is possible to prevent corrosion of the thermal head.

In addition, silica particles are often used as fine particles for the purpose of improving running property and cleaning property. Alkali metal ions such as sodium and potassium,
Alternatively, alkaline earth metal ions such as calcium and magnesium are contained in an amount of about 1.4% by weight with respect to the particles. For the purpose of improving running property, antistatic property and cleaning property,
Although phosphoric acid esters of polyoxyethylene alkyl ether are often used as the surfactant, sodium is contained in an amount of about 7% by weight with respect to the surfactant.

It has been found that if these additives are used as they are, corrosion will occur in the electrode portion of the thermal head after high-speed recording for a long time. It was found that this corrosion phenomenon could not be sufficiently suppressed unless the total amount of metal ions contained in the heat resistant slipping layer was reduced to 4 μg / cm ² or less and the amount was reduced. In particular, high-speed recording, that is, a pixel recording signal pulse period of 10 msec or less, preferably 8
Under the recording condition of msec or less and the recording condition of high energy application, for example, 0.3 W / dot or more, this corrosion phenomenon becomes remarkable, and the total sum of alkali metal and alkaline earth metal ions is reduced to ² μg / cm ² or less. Is particularly preferred. Especially Na ⁺ and K as alkali metal ions
⁺ , And Mg ²⁺ , Ca as alkaline earth metal ions
It is preferable that the total sum of ²⁺ is within the above range.

Alkali metals and alkaline earth metals
Among the ions, alkali metal ions cause corrosion.
The total sum of alkali metal ions is 1 μg / c
m²The following is desirable. Furthermore, alkali metal
Of the on-ions, sodium ions are the most prone to corrosion
Easy to use, so the concentration of sodium ion is 2μg / cm ² 
The following is preferable, and more preferably 0.1 μg / cm² Since
Below. Also for fluorine, 0.5 μg / cm² Since
It is preferable to set it below.

On the other hand, if the cationic substance is completely removed, the antistatic property will be inconvenient. Therefore, it is not preferable because another static eliminator is required. Therefore, it is preferable that the total amount of metal ions contained in the heat resistant slipping layer is 0.1 μg / cm ² or more, depending on the recording conditions. Further, in order to improve the antistatic property, a generally used antistatic agent may be appropriately used.

The method for quantifying the alkali metal, alkaline earth metal and fluorine contained in the surface of the thermal transfer recording sheet and the heat resistant slipping layer is not particularly limited, but the surface is analyzed by fluorescent X-ray for elemental analysis. It is easily obtained by measuring by. That is, alkali metal ions and alkaline earth metal ions such as Na, K,
First, a solution containing a fixed concentration of Mg, Ca ions and F is dropped on a filter paper in a fixed amount, dried, and then measured by X-ray fluorescence analysis to prepare a calibration curve. Using this, fluorescent X-ray measurement is actually performed from the heat resistant slipping layer side of the color sheet under the same conditions, and the amount of these metal ions detected per unit area can be quantitatively determined.

The coating method used for forming the heat resistant slipping layer of the present invention is, for example, a gravure coater, a reverse coater or an air doctor described in "Coating Method" by Yuji Harazaki (1979, published by Maki Shoten). There are various methods such as a method using a coater. The thickness of the heat resistant slipping layer formed on the base film is usually 0.1 to 10 μm, preferably 0.3 to 5 μm.

The base film provided with the heat resistant slipping layer in the thermal transfer recording sheet of the present invention is not particularly limited,
Examples thereof include polyethylene terephthalate film, polyamide film, aramid film, polyimide film, polycarbonate film, polyphenylene sulfide film, polysulfone film, cellophane, triacetate film and polypropylene film. Among them, polyethylene terephthalate film is
From the viewpoints of mechanical strength, dimensional stability, heat resistance, cost, etc., biaxially stretched polyethylene terephthalate film is more preferable. The thickness of these base films is 1 to
It is 30 μm, preferably 2 to 10 μm.

The heat transferable coloring material layer provided on the surface of the base film opposite to the heat resistant slipping layer can be formed by a usual method. For example, in the case of a sublimation heat transfer recording sheet, an ink is prepared by dissolving or dispersing a sublimation or heat diffusible dye and a binder resin having good heat resistance in an appropriate solvent, and coating the ink on a base film. Then, in the case of the melt-type thermal transfer recording sheet, a coloring material such as a pigment or a dye is dissolved or dispersed in a heat-meltable substance by using a solvent as necessary to form an ink. It may be adjusted, the ink is applied to the base film and dried.

Examples of sublimation or heat diffusible dyes used in the above sublimation type thermal transfer recording sheet include azo type, anthraquinone type, nitro type, styryl type, naphthoquinone type, quinophthalone type, azomethine type, coumarin type and condensed polycyclic type. Various nonionic dyes such as are used, and as the binder resin, polycarbonate resin, polysulfone resin, polyvinyl butyral resin, phenoxy resin, polyarylate resin, acrylate resin, polyamide resin, polyaramid resin, polyimide resin, polyether. Examples include imide resins, polyester resins, acrylonitrile-styrene resins and cellulosic resins such as acetyl cellulose, methyl cellulose, ethyl cellulose and the like. Examples of the solvent include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; alcohol solvents such as isopropanol, butanol and methyl cellosolve; Ether-based solvents such as dioxane and tetrahydrofuran; amide-based solvents such as dimethylformamide and N-methylpyrrolidone are used.

As the coloring material used for the melt type thermal transfer recording, for example, an inorganic pigment such as carbon black as a pigment; various organic pigments of azo type and condensed polycyclic type are used.
Further, as the pigment, for example, an acid dye, a basic dye, an oil-soluble dye, a metal complex salt dye or the like is used. As the heat-melting substance, a solid or semi-solid substance having a melting point of 40 to 120 ° C. is preferable, and paraffin wax, microcrystalline wax, carnauba wax, montan wax,
Examples include wood wax and oil-based synthetic wax. As the solvent, the same ones as in the case of the above-mentioned sublimation type thermal transfer recording sheet can be mentioned.

In each of the above inks, in addition to the above components,
Organic or inorganic non-sublimable particles, a dispersant, an antistatic agent, an antiblocking agent, an antifoaming agent, an antioxidant, if necessary.
Additives such as viscosity modifiers can be added. The coating method of these inks can be carried out in the same manner as described for the coating of the heat resistant slipping layer, and the coating film thickness is preferably 0.1 to 5 μm in dry film thickness.

In the production of the thermal transfer recording sheet of the present invention, in order to improve the adhesiveness between each layer formed by the above coating and the base film, the surface of the base film is subjected to corona discharge treatment, Alternatively, an undercoating treatment with a polyester resin, a cellulose resin, a polyvinyl alcohol resin, a urethane resin, a polyvinylidene chloride resin, or the like may be performed.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples, but the Examples are not intended to limit the present invention unless the gist thereof is exceeded. Examples 1 to 5 (a) Production of thermal transfer recording sheet A biaxially stretched polyethylene terephthalate film (thickness 5 μm) was used as a base film, and the basic composition (A) and (B) described in Table 1 was provided on one surface thereof. Alternatively, a coating solution having the composition of (C) is applied to a wet film thickness of about 10 μm,
It was dried at ℃ for 1 minute to form a heat resistant slipping layer.

The cation contents of the silica fine particles (aerosil silica) and the phosphate ester surfactant used in the compositions (A), (B) and (C) are shown in Table 2. Purified or unpurified as in Example 1 was prepared according to the formulation shown in Table-3, respectively.
It was used as a coating liquid for forming the heat resistant slipping layer used in Nos. 5 to 5. Table-2
In (1), the aerosil silica (commercially available product) is regarded as an unpurified product, and the purified aerosil silica is a 1% by weight toluene dispersion of the aerosil silica washed with ion-exchanged water, subjected to liquid separation treatment, and purified by removing water-soluble ions. Obtained. As the phosphate ester surfactant, a commercially available product is used as an unpurified product, and a 5% by weight aqueous solution of this is added to a polyethylene ultrafiltration membrane (NTU-200: NTU-200).
6) and an ultrafiltration device (manufactured by Nitto Denko: UW-1), and then purified by evaporation of water to obtain a purified phosphate ester surfactant.

Sublimable dye (CI Solvent Blue 95) 5 was formed on the back surface of the heat resistant slipping layer of the above film.
Parts, polysulfone resin 10 parts, and chlorobenzene 85 parts were applied and dried to form a coloring material layer having a thickness of about 1 μm, to obtain thermal transfer recording sheets of Examples 1 to 5, respectively.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

(B) Method for measuring alkali metal and alkaline earth metal ions and fluorine Using 3370E manufactured by Rigaku Denki as a fluorescent X-ray analyzer,
The measurement conditions are as follows: Rh tube: 50 kV-40 mA, X
Line passage: He gas, X-ray irradiation diameter: measured at 30 mmφ,
The absolute value (μg /
It was calculated in terms of cm ² ). As a method for creating a calibration curve, aqueous solutions of Na, K, Mg, and Ca (concentration: 200 ppm) were prepared, and 0.25, 50, 100, and 250 μl were dripped and dried on Rigaku Denki filter paper (microcarry). Then, 0, 10, 20, and 50 μg of standard samples were prepared, and the standard samples were measured under the above conditions to obtain a calibration curve.

(C) Preparation of image receptor Saturated polyester resin (Nippon Gosei Co., Ltd .: trade name TR
-220) 10 parts, amino-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF393) 0.5 part, methyl ethyl ketone 15 parts, xylene 15 parts, a synthetic paper (manufactured by Oji Yuka Synthetic Paper Co., Ltd.) : Product name YUPO FPG150)
On the wire bar with a wire bar and dry (dry film thickness of the coating layer is about 5
.mu.m) and further heat-treated in an oven at 100.degree. C. for 30 minutes to prepare an image receptor.

(D) Transfer recording result The color material layer surface of the thermal transfer recording sheets of Examples 1 to 5 prepared as described above and the resin coated surface of the image receptor are overlapped to form the heat resistant slipping layer surface of the thermal transfer recording sheet. Using a partial Grace type line thermal head with a heating resistor density of 8 dots / mm, a pulse period of 8 msec, 0.4 W / dot of power is applied, and a density of 8 lines / mm is 25 ° C. and humidity. 5
Transfer recording was performed at 0% (under normal temperature and normal humidity) for 1 km. However, Example 5 was also performed in an environment of 40 ° C. and 80% humidity. The evaluation results are shown in Table-3. As a result of observing the surface of the head with a microscope, no corrosion of the head was observed and the running property was good. It should be noted that in Example 5, slight corrosion of the head was observed under high temperature and high humidity.

Comparative Examples 1 to 4 Comparative Examples 1 to 4 were carried out in the same manner as in Examples 1 to 5 except that various coating liquids shown in Table 3 were used as the coating liquid for forming the heat resistant slipping layer. A thermal transfer recording sheet was manufactured. Transfer recording was performed on the thermal transfer recording sheets of Comparative Examples 1 to 4 under the same conditions as in the examples. The evaluation results are shown in Table-3.

As a result of microscopic observation of the head surface, when the total amount of Na and metal ions was 4 μg / cm ² or more, a blistering phenomenon occurred due to corrosion of the electrode portion of the head. When the amount was 0.1 μg / cm ² or less, the corrosion phenomenon of the head was not recognized, but since the particles were charged during running, dust in the environment was collected, which caused head contamination and caused inconvenience.

[0037]

According to the thermal transfer recording sheet of the present invention, the thermal head does not corrode even after high-speed recording for a long period of time, and a thermal transfer recording sheet having extremely excellent head durability can be obtained.

[Brief description of drawings]

FIG. 1 is an example (cross-sectional view) of a head heating portion of a thermal head used in the present invention.

[Explanation of symbols]

 1 Heat Dissipation Board 2 Glaze Layer 3 Heating Resistor Layer 4 Electric Conductor 5 Resistor Protective Layer 6 Abrasion Resistant Layer

Claims (10)

[Claims] 1. A thermal transfer recording sheet having a heat transferable coloring material layer provided on one surface of a base film and a heat resistant slipping layer provided on the other surface thereof, wherein an alkali metal ion contained in the heat resistant slipping layer and A thermal transfer recording sheet, characterized in that the total concentration of alkaline earth metal ions is in the range of 4 μg / cm ² or less. 2. A thermal transfer recording sheet in which a heat transferable color material layer is provided on one surface of a base film and a heat resistant slipping layer is provided on the other surface, and alkali metal ions contained in the entire thermal transfer recording sheet and A thermal transfer recording sheet, characterized in that the total concentration of alkaline earth metal ions is in the range of 4 μg / cm ² or less. 3. The total sum of alkali metal ions and alkaline earth metal ions contained in the heat resistant slipping layer is 0.1 to 10.
^2. It is 2.0 μg / cm ² .
2. The thermal transfer recording sheet according to 2. 4. The thermal transfer recording sheet according to claim 1, wherein the alkali metal ions are Na ⁺ and K ⁺ and the alkaline earth metal ions are Ca ²⁺ and Mg ²⁺ . 5. The thermal transfer recording sheet according to claim 1, wherein the total concentration of alkali metal ions contained in the heat resistant slipping layer is 0.1 to 1.0 μg / cm ² . 6. The thermal transfer recording sheet according to claim 1, wherein the heat-resistant slipping layer has a fluorine concentration of 0.5 μg / cm ² or less. 7. The thermal transfer recording sheet according to claim 1, which is a thermal transfer recording sheet used for recording in which a recording signal pulse period per pixel of thermal transfer is 10 msec or less. 8. A thermal transfer recording sheet according to claim 1, wherein a recording signal pulse period per pixel is 10 m.
A thermal transfer recording method characterized by performing thermal transfer recording in seconds or less. 9. A thermal transfer recording sheet according to claim 1, wherein the color material layer side surface of the thermal transfer recording sheet is superposed on the image receptor, and the back surface of the thermal transfer recording sheet is heated via a Grace type thermal head. A recording method, wherein the dye of the sheet is transferred to an image receptor. 10. The recording method according to claim 9, wherein the glaze layer of the thermal head is made of glass.