JPS584152A - electrostatic recorder - Google Patents

Abstract

PURPOSE:To enhance whiteness, naturalness, and contrast, by heat treating zinc oxide together with sulfur added in manufacturing a conductive zinc oxide powder. CONSTITUTION:A conductive zinc oxide powder usable for the conductive layer of an electrostatic recording material is obtained ordinarily by mixing zinc oxide with a dopant, such as aluminum oxide, and heat treating them in a reducing atmosphere, but the obtained zinc oxide powder develops color, lowering and impairing the whiteness and the naturalness of the recording material. Addition of sulfur in the heat treatment permits the obtained zinc oxide powder to color very little, and exhibits excellent conductivity even though heat treatment temperature as low as 600-900 deg.C. An electrostatic recording material is obtained by forming a conductive layer consisting of the obtained highly white conductive zinc oxide powder and a binder on a support and providing a dielectric layer on it.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic recording medium, and more particularly to an electrostatic recording medium that is capable of recording under all temperature and environmental conditions, and has high whiteness and excellent natural properties.◎ Electrostatic recording medium The recording method involves applying voltage pulses from the front, both sides, or back of an electrostatic recording medium, which has a dielectric layer mainly made of insulating resin on a conductive-treated support. This is a recording method in which an electrostatic latent image is formed and developed with toner to make it visible, and is widely used in facsimiles, printers, etc.

Electrostatic recording materials used in such electrostatic recording methods have conventionally been produced by depositing a polymer electrolyte with a cation cap or anion cap on a support.
A conductive layer is formed by m cloth or impregnated, and a dielectric layer mainly made of resin is provided on top of the conductive layer.
* Good records were obtained under certain conditions. However, since a polymer electrolyte is used as the conductive material, the electrical resistance of the conductive layer is greatly affected by the surrounding environmental conditions, and it is difficult to obtain a good record under low humidity conditions. Under conditions of high humidity, the conductive layer's function as a conductive agent deteriorates, resulting in problems such as an extreme drop in recording density and the occurrence of background stains.On the other hand, under humid environmental conditions, the electrical resistance of the conductive layer decreases too much, resulting in poor recording density. This method has disadvantages such as a decrease in resolution due to a decrease in image quality and the occurrence of blurring.

Therefore, in order to overcome the drawbacks of the conventional electrostatic recording material using a polymer electrolyte for the conductive layer, a conductive layer made of a metal oxide semiconductor powder such as conductive zinc oxide powder and a binder is placed on a support. The electrostatic recording material formed and provided with a conductive layer on the conductive layer is disclosed in JP-A-55-33133 Bulletin, JP-A-1@55-33.
134, etc., and methods for producing conductive zinc oxide powder used in such electrostatic recording materials have also been proposed in Japanese Patent Publications No. 5S-19896, Japanese Patent Publication No. 1155-19897, etc. However, in order to obtain conductive zinc oxide powder with a resistivity that can be used for electrostatic recording media that can record under the wide range of temperature and environmental conditions seen in these proposals, it is usually necessary to use a doping agent such as zinc oxide and aluminum. had to be mixed and fired at a fairly high temperature in a reducing yIIH atmosphere, and coloring of the l*zinc oxide powder was unavoidable.

As a result, when zinc oxide powder was used in the conductive layer of an electrostatic recording material, the whiteness decreased significantly compared to an electrostatic recording material using a conventional polymer electrolyte, and the contrast of the electrostatic recording image decreased. deterioration and electrostatics - has the disadvantage of impairing the naturalness of the body.

The present invention aims to solve the above-mentioned drawbacks and provide an electrostatic recorder with high whiteness, naturalness, and excellent contrast.

The present inventors investigated various methods for increasing the whiteness of #zinc oxide powder in order to improve the whiteness of electrostatic recording materials using conductive zinc oxide powder in the conductive layer. It was discovered that highly white conductive zinc oxide powder can be obtained by a method different from the manufacturing method of conductive zinc oxide powder, and an electrostatic recording material using the thus obtained highly white conductive zinc oxide powder for the conductive layer can be produced using a method different from that of conventional polymer polymers. It has been found that the whiteness is equal to or higher than that of an electrostatic recording material using an electrolyte in the conductive layer, and stable recording can be obtained under a wide range of humid environmental conditions.

That is, the present invention provides an electrostatic recording material in which a conductive layer made of conductive zinc oxide powder and a binder and a conductive layer are sequentially provided on a support, wherein the conductive zinc oxide powder is zinc oxide,
At least one of aluminum oxide or an aluminum compound that produces aluminum oxide when fired at high temperature
The seeds and sulfur were heated at 600°C to 9°C in a reducing atmosphere.
This electrostatic recording material is characterized in that it is heated and fired at a temperature of 00°C.

The specific resistance of the conductive zinc oxide powder used in the present invention W14 is ll
1G-” to 1♂Ω” under 5OKf/clI pressure
If a is appropriate and the specific resistance is 10'Ω for removing scratches, the surface electrical resistance value necessary to obtain an electrostatic recording image can be obtained when used in combination with a binder to form a conductive layer. Zu, again 1
Products with a resistivity of O-10 or less require the addition of a large amount of doping agent and firing at a high heating temperature, which cannot be obtained by mixing m-kun and firing. Since the conductive zinc oxide powder has a gray to black color, it does not meet the purpose of the present invention, which is to obtain an electrostatic recording material with high whiteness and excellent naturalness.

Regarding the manufacturing method of the highly white conductive zinc oxide powder used in the electrostatic recording material of the present invention, it is possible to use flujnium oxide powder with an average particle size of 20 s or less for zinc oxide and 100 mol of zinc oxide, or aluminum oxide powder during high temperature firing. 5 to 7 mole percent of aluminum hydroxide, aluminum chloride, flunirum bromide, aluminum acetate, aluminum nitrate, fluminiram sulfate, etc., which produce a solid carbon, such as powder, granules, or Heating and firing at a temperature of 60'Ω°C to 900°C for 0.5 to 10 hours in the presence of the main legs or in a furnace with a reducing atmosphere made of sulfurized water gas, carbon oxide, etc.,
When it is cooled to room temperature, it can be obtained from k. The conductive zinc oxide powder obtained by adding sulfur and heating and firing is hardly colored and has excellent conductivity even at low firing temperatures. Sintering of zinc oxide powder hardly occurs during firing. Therefore, the particle size of conductive zinc oxide is almost determined by the zinc white that is the raw material before firing. The particle diameter is preferably 10 μm or less, and most preferably the average particle size II is 2.0 to 0.1 μm.

To specifically describe the method for manufacturing an electrostatic recorder of the present invention, first, the highly white conductive zinc oxide powder obtained by the above method, methyl cellulose, polyvinyl alcohol, tenbun, carboxymethyl cellulose, Alginic acid sorter, sodium salt of styrene-maleic acid copolymer, polyvinylpyrrolidone, water-soluble resin of polyvinylbenzyltrimethylansoniF mucoulide, vinyl acetate resin Emma I resin, acrylic resin resin, 8BR latex, etc. water-dispersible resin or polyvinyl butyral,
5 to 50 parts by weight of a binder such as Nido-Celluse S vinyl chloride Itm, 7-acrylic acid ester resin, acetate-butyric acid CELPS, and Sudelenstadiene copolymer resin per 100 parts by weight of the zinc oxide powder. A coating solution mixed and dispersed in a blending ratio of parts by weight, preferably 10 to 40 parts by weight, is coated on one side of a support such as paper, film synthetic paper, etc. using a bar coater, blade coater, air knife coater, etc. and dried to form a conductive layer. form. In addition, high white oxidation! m1)X! It is free to add additives normally contained in a coating solution consisting of a binder and a binder, such as an inorganic pigment, a polymer fine particle dye, an antifoaming agent, etc.@Also, the surface electrical resistance value of the conductive layer is 5. X 1G'~5
Since X 10”Ω is common for obtaining electrostatically recorded images,
The coating amount can also be selected within the range of 3 to 20 e/i as required. In addition to the above-mentioned polyvinylbenzyltrimethylammonium chloride, the binder also contains cationic polymer electrolytes such as polyethylene isohydrotapride, poly(glycidyl trigyl phosphonium coolite), polystyrene sulfonate, and polyvinyl chloride. Of course, a 5-7-ion type polymer electrolyte such as sulfonate can also be used.

Next, on the conductive layer of the conductive support prepared by the above method, acrylic resin, methacrylic resin, vinyl acetate resin, silicone resin, vinyl acetate/vinyl chloride copolymer resin,
An electrostatic recording material can be obtained by coating one or more dielectric resins such as polyester resin, polyvinyl styral resin, and styrene resin as a mixture to form a dielectric layer. In this case, the imprintability of the electrostatic recording medium,
In order to enhance the natural appearance, auxiliary agents such as white pigments such as calcium carbonate, silica, clay, and titanium oxide, fluorescent dyes, dispersants, and antifoaming agents may be mixed with the dielectric resin. In general, the thickness of the dielectric layer is generally 4 to 10 μm due to the relationship between withstand voltage and dielectric constant.Furthermore, a conductive layer may be provided on the opposite side of the dielectric layer of the electrostatic recording medium, if necessary.
The present invention is no exception. At that time, a conductive layer made of the highly white conductive zinc oxide powder and a binder may be provided, or a conductive layer made of a polymer electrolyte may be provided.

The electrostatic recording material of the present invention obtained in this way is not only capable of stable recording under all temperature and environmental conditions, but is also equivalent to or equivalent to conventional electrostatic recording materials in which a conductive layer is formed using a polymer electrolyte. It has a whiteness higher than that, and the contrast and naturalness of electrostatically recorded images are excellent. Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is of course not limited to these.

(Example) After uniformly mixing No. 1 zinc white (manufactured by Hakusui Kagaku Co., Ltd.) in a dry method by changing the type and amount of doping agent added and the amount of sulfur added to sO04, this mixture was poured into a container. The crucible was then placed in a Matsufuru furnace lined with powdered wood and fired at temperatures of 800°C and 950°C for 90 minutes. After firing, deposit the fired product in Ruri d, leave it in a glass container through which nitrogen gas is passed, and let it cool to room temperature.
Two types of conductive zinc oxide powders were obtained.

The conductive zinc oxide powder thus obtained was heated at 20°C and 65%RH.
After seasoning indoors for 12 hours, the specific resistance, color tone, and average particle size of each conductive zinc oxide powder under a pressure of 150 Jll/- were as shown in Table 1-1. The resistance was low, and the specific resistance was lower when sulfur was added and fired than when no sulfur was added, and highly white conductive zinc oxide powder was obtained.

Next, using each of the 12 types of conductive zinc oxide powder obtained above, 100 parts by weight of conductive zinc oxide powder, 30 parts by weight of polyvinyl alcohol (Kuraray Co., Ltd. 11117K) and 100 parts by weight of water were placed in a ball mill for 30 minutes. A conductive layer coating solution was prepared by mixing and dispersing for a minute. Apply this conductive layer coating solution to one side of 50r/- high-quality paper using a wire bar until the dry weight is 1.
Twelve types of conductive supports were prepared by drying a 5Kjlk cloth to give a ratio of ly/y. Further, as a comparative example, a conductive support of an electrostatic recording medium (Sanfax FM-45 manufactured by Tamako Paper Co., Ltd.) was prepared using a polymer electrolyte.

The surface electrical resistance values of the conductive layers of the 13 types of conductive supports thus obtained were measured under different temperature and environmental conditions. The results are shown in Table 2. In contrast, the surface electrical resistance of a conductive layer made of conductive zinc oxide powder remains almost constant under various temperature conditions. Next, on the conductive layer of the four types of conductive supports prepared above, acrylic resin (Mitsubishi Sea 5F Co., Ltd. [LRlGB)
90 parts by weight and calcium carbonate (Shiraishi Calcium Co. 1) N
Mix and disperse 30 parts by weight of CCP) in a toluene solvent and use a wire bar to give a dry weight of 6 g/w/51C.
n types of electrostatic recording bodies were created by drying the electrostatic recording bodies in this way.
Attached to a factor 4 receiver with same-plane control system, linear density @t/wm, pulse width 12μ■, C1 pin electrode -5oo
After recording under the conditions of application of +300V to the control electrode, and then developing and fixing using a carrierless donor, the optical density of the image area and the whiteness of the non-image area were measured for recording samples with each of these electrostatically recorded images. are shown in Table 3. Electrostatic cones made of conductive zinc oxide powder produce clear electrostatic recording images under a wide range of humid environmental conditions. All of the electrostatic recording materials using zinc oxide powder had a whiteness of 73 or higher, which was equivalent to or higher than that of the electrostatic recording materials using conventional polymer electrolytes.・

Claims (1)

[Claims] a) An electrostatic recording material in which a conductive layer and a dielectric layer each comprising a conductive zinc oxide powder and a binder are provided on a support, wherein the conductive zinc oxide powder contains zinc oxide, alkaline oxide, etc. aluminum or at least one aluminum compound that produces aluminum oxide when fired at high temperatures and sulfur at 600°C to 900°C in a reducing atmosphere.
An electrostatic recording material 0 (2) characterized in that the conductive zinc oxide powder has a specific resistance of 1.
10-1 to 104Ω under a pressure of 50Kf/-
Claim HIIE (1) characterized in that it is sub-
Electrostatic recording medium 0 described in section 0