JPH03182761A - Electrostatic recording body - Google Patents

Abstract

PURPOSE:To stably obtain high-density recorded images even under an extremely low humidity condition by providing conductive layers contg. smectite clay and a moisture retaining agent on one or both surfaces of a base and forming a dielectric layer on the surface of either of the conductive layers. CONSTITUTION:The excellent characteristics of the smectite clay, i.e. good electrical conductivity, are more than sufficiently exhibited even under the extremely low humidity condition if a material having an excellent moisture retaining property is used in combination. The recording medium is eventually hardly affected by the installation environment of a recorder and, therefore, the conductive layers contg. the smectite clay and the moisture retaining agent are provided on one or both surfaces of the base. The dielectric layer is formed on the surface of either of the conductive layers. The moisture retaining agent is exemplified by, for example, polyethylene glycol, chitin, chitosan, sodium pyrrolidone carboxylate, etc. The compounding ratio of the moisture retaining agent and the smectite clay is preferably adjusted within the range of 1:100 to 100:1 solid content ratio. The recorded images which have the excellent electrical conductivity even under the extremely low humidity conditions and are stable in the wide environment condition range are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an electrostatic recording medium used in electrostatic recording type plotters and printers using multi-needle electrodes.

``Prior art'' Electrostatic recording methods using multi-needle electrodes have been used in various industrial fields because they are capable of outputting wide, high-speed recorded images due to advances in CAD technology such as computer-aided design and simulation in recent years. It is being

Methods for conductive treatment of electrostatic recording materials used in electrostatic recording methods include using conventionally known polymer electrolytes, sputtering or vapor deposition of metals, and using metals such as tin oxide, indium oxide, and conductive zinc oxide. Methods are known in which conductive powders are kneaded into a support or these conductive powders are coated on the surface of the support together with a binder.

However, since the conductivity of polymer electrolytes changes depending on the environmental humidity, they have drawbacks such as the inability to produce images at low humidity. Also,
Conductive powders such as conductive zinc oxide and conductive tin oxide and vapor deposition treatments reduce whiteness and increase costs.

To solve these problems, a conductive layer using smectite clay, which is ionic conductive but relatively unaffected by environmental humidity, has been proposed, but it still cannot be used under extremely low humidity conditions. At present, conductivity cannot be obtained.

``Problems to be Solved by the Invention'' In view of the current situation, the present inventors have conducted extensive research into improving electrostatic recording materials consisting of a conductive layer using smectite clay, and have found that when a humectant is added to the conductive layer, The present inventors have discovered that recorded images of high density can be stably obtained even under extremely low humidity conditions, and have completed the present invention.

"Means for Solving the Problems" The present invention provides an electrostatic recording material in which a dielectric layer mainly composed of an insulating resin and a pigment is formed on a conductive support, on one or both sides of the support. The electrostatic recording material is characterized in that a conductive layer containing at least smectite clay and a humectant is provided, and a dielectric layer is formed on either surface of the conductive layer.

"Function" In the present invention, examples of the smectite clay contained in the conductive layer include montmorillonite, beidellite, nontrolite, sabonite, iron sabonite, sauconite, stevensite, and hektonite.

These smectite clays are pale yellow or white plate-shaped fine powders, and in an aqueous solution, they form a so-called card house structure because there are positive ions and negative ions on the surface of the smectite clays. Therefore, when these are coated on a smooth support surface and dried, they exhibit conductivity due to the chain of ions.

The conductivity of smectite clay has a characteristic of being less dependent on humidity than that of conventional ionic conductive polymer electrolytes. However, according to the tests conducted by the present inventors, 13℃2
It has become clear that good conductivity is not exhibited under extremely low humidity conditions such as 0% RH or less.

As a result of further investigation into the cause of this, it became clear that the conductivity of smectite clay does not change in proportion to the water content, but when the water content falls below a certain value, it rapidly loses its conductivity.

As a result of further intensive research into this improvement, we found that when combined with a substance that has excellent moisture retention properties, the excellent features of smectite clay can be fully demonstrated even under extremely low humidity conditions, resulting in a suitable environment for recording equipment. It was discovered that an electrostatic recording medium capable of stable and good recording can be obtained with almost no influence, and the present invention was completed.

In the present invention, examples of humectants used in combination with smectite clay include polyethylene glycol, chitin, chitosan, sodium pyrrolidone carboxylate, glycerin, turbitz, acidic mucopolysaccharides such as hyaluronic acid and chondroitin, chondroitin 4-sulfate, and chondroitin 6. - Sulfated mucopolysaccharides such as sulfuric acid, dermatan sulfate, heparin and heparan sulfate, keratosaccharides such as keratosulfate, and the like.

All of these humectants are capable of retaining excess water molecules within their molecules, so they have the property of not reducing the ion mobility of smectite clay even in low humidity environments. The blending ratio of these humectants and smectite clay is desirably adjusted within the range of 1:100 to 100:1 in terms of solid content.

The effects of the present invention can be most effectively obtained when a highly smooth film or the like is used as the support. Examples of the film support include polyethylene terephthalate film, polycarbonate film, polypropylene film, acrylic resin film, polyvinyl chloride film, and polyethylene film. When these film supports are used, the coating amount of the conductive layer coating liquid is generally adjusted in the range of about 0.5 to 10 g/rrr in terms of dry weight.

In addition, in the case of supports with low surface smoothness such as high-quality paper, glossy paper, and nonwoven fabrics, one or more undercoat layers mainly composed of pigments or resins are provided, and then supercalendering is applied after applying the undercoat layer. It is desirable to form the conductive layer of the present invention after smoothing the coated surface by mirror casting or the like.

In the case of such a support, the coating amount of the conductive layer coating liquid is
It is preferable to adjust it within a range of about 3 to 15 g/m. Note that since both smectite clay and humectant have high ionic concentrations, they may aggregate or cause an extreme increase in viscosity when mixed. Therefore, a method of separately providing a layer mainly composed of smectite clay and a layer mainly composed of a humectant is one of the preferred embodiments of the present invention.

In addition, to improve practical properties such as blocking resistance and barrier properties, it is possible to use other resins and pigments, and to prevent repellency, it is possible to use various auxiliary agents such as surfactants. It is.

Furthermore, a conductive layer made of a polymer electrolyte, a conductive metal oxide semiconductor powder, or the like may be used in combination, as long as the conductivity of the conductive layer made of the smectite clay and humectant is not impaired.

The conductive coating liquid is applied onto the support using various coating devices such as a wire bar coater, an air knife coater, and a roll coater/gravure coater.

Pigments constituting the dielectric layer are not particularly limited, but include, for example, heavy or light calcium carbonate, amorphous silica, calcined amorphous silica, silane-treated amorphous silica, plastic pigments, calcined clay, alumina, and water. aluminum oxide, clay, magnesium hydroxide,
Examples include titanium oxide.

In addition, examples of the insulating resin forming the dielectric layer include acrylic acids such as methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, isobutyl methacrylate, and 2-ethylhexyl methacrylate. Ester copolymers, methacrylic acid ester copolymers, vinyl acetate, ethylene-vinyl acetate copolymers, butyral resins, polyester resins, nitrocellulose, polystyrene, styrene-acrylic copolymers, styrene-methacrylic acid copolymers, phenol Examples include resin.

Generally, the dielectric layer coating liquid is prepared by dissolving and dispersing the pigments and insulating resins in an organic solvent such as toluene, methyl ethyl ketone, or isopropyl alcohol.
For example, a dielectric layer is formed by coating onto a conductive support using a coating device such as a bar coater, gravure coater, curtain coater, or champlex coater.

"Examples" Examples of the present invention will be described below, but of course the present invention is not limited thereto. Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Example 1 After washing one side of a 70 micron thick polyester sheet with alcohol, smectite clay [trade name: VEEG]
A conductive coating liquid prepared by mixing and dispersing 100 parts of UM (manufactured by Vanderbilt) and 20 parts of polyethylene glycol in 1000 parts of water was coated and dried to give a dry weight of 5 g/rrr to obtain a conductive support. .

Next, a dielectric layer coating solution having the composition shown below was coated on the conductive support at a dry weight of 3.5 g/nl and dried to obtain an electrostatic recording material.

[Dielectric layer coating liquid]

35 parts of methyl methacrylate resin, 35 parts of butyl methacrylate resin, and 30 parts of calcium carbonate were added to 200 parts of toluene.
Coating liquid prepared by mixing and dispersing the liquid.

Example 2 A coating solution prepared by mixing and dispersing 10 parts of smectite clay (trade name: Smecton 5A-1, manufactured by Kunimine Kogyo Co., Ltd.) in 200 parts of water was applied to one side of a 70 micron thick polyester sheet.
After coating and drying at 2.5 g/rrr in terms of dry weight, 0.0 g of a coating solution prepared by dissolving 1 part of hyaluronic acid [trade name: Denka Hyaluronic Acid, manufactured by Denki Kagaku Kogyo Co., Ltd.] in 1000 parts of water was applied on top.
A conductive support was obtained by coating at 5 g/mr and drying. An electrostatic recording material was obtained in the same manner as in Example 1 except that this conductive support was used.

Comparative Example 1 An electrostatic recording material was obtained in the same manner as in Example 1 except that polyethylene glycol as a humectant was not used in preparing the conductive coating liquid.

The three types of electrostatic recording bodies obtained in this way were pasted together,
Recordings were made using a practical electrostatic printer (trade name: CE-3424, manufactured by Xerox Corporation) under various environmental conditions as described in the table. The surface resistance values and image densities of the conductive layers under various environmental conditions are listed in the table.

Table "Effects" As is clear from the results in the table, the electrostatic recording materials obtained in each example of the present invention have excellent conductivity even under extremely low humidity conditions and are stable over a wide range of environmental conditions. I was able to obtain a good recorded image.

Claims (3)

[Claims] (1) In an electrostatic recording material in which a dielectric layer mainly composed of an insulating resin and a pigment is formed on a conductive support, the conductive material contains at least smectite clay and a humectant on one or both sides of the support. 1. An electrostatic recording material comprising a plurality of layers and a dielectric layer formed on one of the surfaces of the conductive layer. (2) The electrostatic recording material according to claim (1), wherein a conductive layer mainly composed of smectite clay and a layer containing a humectant are separately provided on one or both sides of the support. (3) Claim (1) or (2) wherein the support is a film.
The electrostatic recording medium described above.