JPS5828574B2 - electrostatic recorder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic recording medium used for facsimile IJ or high-speed printing, etc., and its purpose is to provide an electrostatic recording medium that has excellent humidity resistance, high whiteness, and is excellent as a recording medium. The object of the present invention is to provide an electrostatic recording medium that has natural properties.

Conventionally, as an electrostatic recording material, as is already clear from many literatures, 10" to 1"
It is known that a conductive layer having a surface resistivity ρ8 of 0.11Ω is provided, and a dielectric layer made of a high dielectric material having a specific resistance ρ of 1012Ω or more is further provided thereon.

Conventionally, this conductive layer is made of high-quality paper impregnated with an electrical electrolyte such as lithium chloride, a cationic polymer electrolyte such as a polymer quaternary ammonium salt, or an anionic polymer such as a polymer sulfonate. Generally, a molecular electrolyte was coated on a support.

However, in such a conductive layer that utilizes ionic conduction of an electrolyte, its ρ8 is greatly affected by the surrounding atmospheric humidity, especially relative humidity (-hereinafter expressed as %RH).
When the humidity is low, such as 20% RH or less, ρ8 increases rapidly, which has a fatal drawback that makes recording almost impossible.

This is because, in a low-humidity atmosphere, water necessary for ion conduction is evaporated, making electrical conduction by ions impossible.

In order to solve this drawback of ionic conduction, an example has been disclosed in which an electronically conductive material such as cuprous iodide or silver iodide is used for the conductive layer (Japanese Patent Application Laid-Open No. 159339-1982).
No. 4830936, USP3245
833).

In other words, by using an electronically conductive material,
It is possible to record even in low humidity without being affected by atmospheric humidity.

However, cuprous iodide and silver iodide are colored, and their electronic conductivity comes from excess iodine.
It is thermally unstable and has unfavorable properties such as liberating iodine when an electrostatic latent image is developed with toner and heat is used for fixing.

In view of such prior art, the present inventors investigated the application of metal oxide semiconductors to electrostatic recording materials as thermally stable electronically conductive conductive materials. By dispersing n-type metal oxide semiconductor powder, whose resistance has been lowered through contact treatment with tin or antimony trihalide, in a binder to form a conductive layer, an extremely excellent electrostatic recording material can be produced. I found out what I can get.

That is, the present invention applies the method for lowering the resistance of n-type metal oxides disclosed in Japanese Patent Application No. 134191/1980 to electrostatic recording materials, thereby producing a recording material that has high whiteness and excellent naturalness as a recording material. Furthermore, the present invention provides an electrostatic recording medium with extremely excellent moisture resistance.

Hereinafter, the present invention will be explained in more detail using examples.

Here, for comparison, an electrostatic recording material using an n-type metal oxide semiconductor powder as a conductive material that is not subjected to contact treatment with tin-7-halide or antimony trihalide is given as a comparative example. The following examples will be described.

Many n-type metal oxide semiconductors are known, but when the electrostatic recording material of the present invention is used as electrostatic recording paper, the whiteness of the recording paper is high and it does not look like ordinary paper. colorless or light-colored metal oxides are preferred for this application.

Specifically, tin dioxide, indium oxide, zinc oxide, etc. are optimal for this purpose.

Comparative Example 1 An electronically conductive metal oxide semiconductor powder was prepared as follows.

commercially available tin dioxide was doped with antimony pentoxide at a concentration of 0.3 mole percent using conventional doping techniques;
Low resistance tin dioxide was obtained.

Similarly, indium oxide was doped with tin dioxide at a concentration of 10 mol percent, and zinc oxide was doped with aluminum oxide at a concentration of 0.5 mol percent.

The obtained powder 0.6'if was put into an insulating cylinder with an inner diameter of 5 mm, and a pressure of 70 kg/cr7t was applied from both sides using platinum electrodes.
The specific resistance ρ of the powder was measured while pressurizing at a pressure of .

The results are summarized in Table 1.

Polyvinyl alcohol (
PVA), hydroxyethyl cellulose (HEC), styrene-butadiene copolymer latex (SBR), etc. were added as a binder and pulverized and dispersed with water in a ball mill to obtain a conductive layer coating.

Table 1 also shows the surface resistivity ρ8 of a conductive layer obtained by applying this paint onto high-quality paper using a wire bar.

Although ρ varies depending on the type of metal oxide, a conductive layer having approximately the desired ρ8 can be obtained by changing the coating amount.

Next, on this conductive layer, a dielectric layer paint having the following composition was applied using a wire bar adjusted so that the average thickness after drying was 3 to 4 microns.

When the fabric density of the electrostatic recording material thus obtained was measured using a Macbeth reflection densitometer, it was 0.13 to 0.14, and some coloring was observed depending on the color of the conductive material.

In addition, a recording test of this electrostatic recording medium was conducted at 20°C and a humidity of 2% R.
When the test was carried out in an atmosphere ranging from H to 95% RH, almost satisfactory recording was possible in all humidity ranges.

Example 1 Similar to the comparative example, 0.1 mole percent of antimony pentoxide to tin dioxide, 1 mole percent of tin dioxide to indium oxide, and 0.2 mole of aluminum oxide to zinc oxide using conventional doping techniques. Doped at a concentration of %.

The obtained metal oxide semiconductor powder was immersed in an aqueous solution containing 1 mol percent of stannous fluoride based on the metal oxide.

Thereafter, the mixture was stirred for several minutes, the metal oxides** were separated by filtration, and the mixture was dried at 60°C for 2 hours.

The metal oxide powder thus obtained had a much higher degree of whiteness than the comparative example, as the amount of dopant was small.

However, looking at the specific resistance, as shown in Table 2, a powder with much lower resistance than that in the comparative example was obtained.

Although stannous fluoride was used here as a reagent for immersion treatment of metal oxides, other tin halides, antimony trihalides, and the like also had a similar effect of lowering resistance.

A binder was added to these low-resistance metal oxide powders, and the mixture was ground and dispersed with water in a ball mill to form a conductive layer coating.

Table 2 also shows the surface resistivity ρ8 of the conductive layer obtained by applying this paint onto high-quality paper using a wire bar.

Next, the dielectric layer paint shown in the comparative example was applied onto this conductive layer to obtain an electrostatic recording material.

The fabric density of this electrostatic recording material is 0.11 to 0.1.
2, and the whiteness was much higher than that of the comparative example.

Furthermore, as is clear from Table 2, ρ of about 107Ω
Approximately half of the coating amount of the comparative example was sufficient to obtain No. 8, and therefore, the naturalness as a recording medium, that is, the thickness, texture, etc., were also extremely excellent.

Also, in recording tests, all humidity ranges (2%
RH to 95% RH), clear recording was possible at the same recording density.

Example 2 In Example 1, PVA,
Although HEC, SBR, etc. were used, here, by using a polymer electrolyte, an even better electrostatic recording material is provided.

Polymer electrolytes broadly refer to those in which lithium chloride or the like is dissolved in a binder such as PVA, but in that they themselves have binding properties, they are different from the aforementioned cationic and anionic ones. Polyelectrolytes are suitable.

Specifically, the cationic polymer electrolyte was polyvinylbenzyltrimethylammonium chloride (ECR from Dow Chemical Company), and the anionic polymer electrolyte was polystyrene sulfonate sodium (Arayo Kagaku Co., Ltd.).
AEP-1) and others.

Furthermore, it is of course possible to use not only such a polymer electrolyte but also SBR, PVA, etc. in order to improve the binding property.

When a conductive layer was formed using such a polymer electrolyte as a binder, as shown in Table 3, it was possible to obtain 1.
A conductive layer having ρ8 of about 0.07Ω could be obtained.

The electrostatic recording material obtained by coating this conductive layer with a dielectric layer had excellent recording properties similar to those in Example 1, and had even better naturalness as a recording material. Ta.

This is due to the complementary action of the electronic conductivity of the n-type metal oxide semiconductor and the ionic conductivity of the polymer electrolyte.

In the previous examples, the metal oxide doped with Dopan I was immersed in an aqueous solution of stannous fluoride and then dried.
An electrostatic recording material having similar characteristics can also be obtained by adding tin or the like to the dispersion.

However, in this case, the above-mentioned cationic polymer electrolyte tends to gel if tin fluoride is present in the aqueous solution, so it is preferable to use an anionic polymer electrolyte here.

Example 3 As shown in Example 1, the n-type metal oxide semiconductor powder with reduced resistance has a very low ρ.

This led to the excellent effect of reducing the coating amount of the conductive layer, but on the other hand, it also had the effect of making it possible to use a filler by taking advantage of the extremely low ρ of the powder.

That is, by using not only an n-type metal oxide semiconductor as a conductive material in the conductive layer but also a white pigment such as calcium carbonate, talc, or titanium oxide as a filler,
Furthermore, an electrostatic recording medium with high whiteness can be obtained.

-fl, the specific resistance shown in Example 1 is 3.8 x 10-
IOO parts by weight of tin dioxide of 1Ω and 20 parts by weight of calcium carbonate were pulverized and dispersed together with sodium polystyrene sulfonate (AEP-1, manufactured by Arayo Kagaku Co., Ltd.) as a binder and water was added thereto.

This paint was applied to form a conductive layer, and a dielectric layer was further applied thereon to obtain an electrostatic recording material.

The coating amount of the conductive layer is 7.3? /m'', its ρ8 is 3.6
It was 107Ω.

When the fabric density of this electrostatic recording material was measured, it was 0.10, and the whiteness was extremely high.

As with Example 1.2, the recording characteristics were also extremely excellent over a wide humidity range.

In indium oxide and zinc oxide of tin dioxide powder,
It is of course possible to use fillers in exactly the same way.

Example 4 Among the metal oxides used in the previous examples, a particularly excellent conductive material can be obtained when tin dioxide is synthesized by calcination of tin oxalate.

Dissolve 0.46f of antimony trichloride in 50ml of ethanol, and add 103g of tin oxalate (Kanto Chemical Co., Ltd.) to this solution.
Co., Ltd.), and after stirring, the ethanol was evaporated and removed.

The obtained powder was heated in an electric furnace to a temperature of 500°C for 5 hours to perform oxidative decomposition, and then the temperature was raised to 1200°C and fired for 5 hours.

The tin dioxide powder thus obtained is a pale blue powder doped with antimony pentoxide at a concentration of 0.2 mole percent.

This powder was immersed in an aqueous solution of stannous fluoride in the same manner as in Example 1 to lower the resistance. high,
Tin dioxide powder was obtained.

In addition, the tin dioxide powder obtained here has a uniform particle size of approximately 1μ, so it can be made into a conductive layer coating simply by mixing it with a binder, without the need for a pulverization and dispersion process using a ball mill or the like. .

When this conductive layer paint and dielectric layer paint were applied in the same manner as in Example 1, the amount of conductive layer coated was even smaller (
Coating amount: 4.7? /m'', ρ8; 31×10 7 Ω), and an electrostatic recording medium with extremely excellent naturalness as a recording medium was obtained.

In addition, the fabric density was 0.10, which was an extremely high degree of whiteness, and the moisture resistance was also excellent in the recording test.

As is clear from the above description, in the present invention, by using an n-type metal oxide whose resistance has been lowered by contact treatment with tin halide or antimony trihalide as the conductive material of the conductive layer. , it is possible to obtain an electrostatic recording medium with extremely excellent humidity resistance characteristics.

In addition, since metal oxides are extremely thermally stable,
Naturally, there is no inconvenience such as generation of corrosive gas during heat fixing, unlike in conventional examples using iodized steel.

As n-type metal oxide semiconductors, tin dioxide, indium oxide, and zinc oxide have excellent stability and whiteness.
By lowering the resistance using tin halide or the like, it is possible to obtain an electrostatic recording material with high whiteness and excellent naturalness.

Claims (1)

[Scope of Claims] 1. An electrostatic recording material in which a conductive layer and a dielectric layer are sequentially provided on a support, wherein the conductive layer contains... stannous chloride or antimony trihalide in a binder. 1. An electrostatic recording material comprising dispersed powder of an n-type metal oxide semiconductor whose resistance has been reduced by a contact treatment. 2. The electrostatic recording material according to claim 1, which is at least one selected from the group consisting of the n-type gold metal oxide semiconductor, silver dioxide, indium oxide, and zinc oxide. 3. The electrostatic recording material according to claim 1 or 2, wherein the binder contains at least a polymer electrolyte. 4. The electrostatic recording material according to claim 2, wherein the silver dioxide is silver dioxide obtained by firing tin-oxalate. 5. The electrostatic recording material according to claim 3, wherein the polymer electrolyte is an anionic polymer electrolyte.