JPS5945983B2 - Electrostatic recording method and electrostatic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic recording method such as facsimile, high-speed printing, electrostatic transfer, etc., and an electrostatic recording medium suitable for carrying out the method.

As is well known, the normal electrostatic recording method involves applying a voltage in an imagewise manner to an electrostatic recording medium, which has a recording layer made of a highly insulating resin on a base treated with low resistance to form an electrostatic latent image. This is a method of visualizing this using colored toner.

Conventionally, as a substrate for low-resistance treatment of electrostatic recording materials, polymer electrolytes, inorganic salts, metal powders, etc. are coated alone or together with binders such as starch and polyvinyl alcohol on supports such as paper, synthetic paper, and plastic films. It has been used with its surface resistance adjusted to 10 5 to 10 10 Ω. Among these low-resistance processing agents, polymer electrolytes, inorganic salts, etc. obtain conductivity through ionic conduction due to moisture absorption, so their resistance value changes greatly due to changes in relative humidity, and when the relative humidity is 20%
If the surface resistance is less than 1011Ω, the image will fade, and if the humidity is 90% or higher, the surface resistance will be less than 105Ω, causing a problem called "white spots."Also, when using low-resistance materials such as metal powder as a binder, it will become less than 105Ω. When used in a dispersed state, the resistance value changes significantly depending on the blending ratio, dispersion conditions, etc., and it is difficult to always obtain a constant resistance value.Furthermore, according to the conventional method, the resistance value changes significantly depending on the blending ratio, dispersion conditions, etc. There were drawbacks such as deterioration over time, stickiness especially at high humidity, and peeling of the recording layer when water was attached.

The present invention eliminates the above-mentioned drawbacks and provides an electrostatic recording material having a low resistance layer with little humidity dependence.

The present invention also provides a method for obtaining a stable low-resistance layer with little humidity dependence by irradiating ultraviolet rays or white light onto an electrostatic recording material having a photoconductive zinc oxide layer to an insulating resin layer as a low-resistance layer. It is something.

That is, the present invention has a low resistance layer on one or both sides of the support,
Further, in an electrostatic recording material having a recording layer mainly composed of an insulating resin on the low resistance layer or on the opposite side of the support from the low resistance layer, the low resistance layer is made of photoconductive zinc oxide and an insulating resin. It is an electrostatic recording material characterized by having as a main component.

Such electrostatic recording materials produce images by irradiating the low-resistance layer with ultraviolet rays or white light and then applying a voltage between the recording electrode and the counter electrode to form a silent charge image on the recording layer. can be formed.

Generally, the photosensitive materials used in electrophotographic electrofaxing are made of photoconductive zinc oxide and binders such as polystyrene, acrylic resins, alkyd resins, silicone resins, vinyl chloride-vinyl acetate copolymers, etc. on a conductive support. Sensitizing dyes such as rose bengal, methylene blue,
This paper has a photoconductive layer with a thickness of about 3 μm by dispersing methyl orange, acrylic orange, etc. (electrofax paper), and does not have a recording layer like the electrostatic recording material of the present invention. When such a photosensitive material is exposed using a light source such as a halogen lamp, the surface resistance of the photoconductive layer becomes 10
The resistance value is 8 to 10 9 Ω (original surface resistance is 10 12 Ω), which coincides with the optimum resistance value of the low resistance layer of the electrostatic recording material.

Based on these results, the present inventors believed that photoconductive zinc oxide could be used in a low resistance layer of an electrostatic recording medium, and as a result of various experiments, they completed the present invention.

．． 'The electrostatic recording medium of the present invention will be explained with reference to the drawings. The low-resistance layer 2 is provided on one side of the support 1 as shown in FIG. 1, and the recording layer 3 is provided on the opposite side, and FIG. As shown in FIG. 3, a low resistance layer 2 is provided on one side of the support 1 and a recording layer 3 is further provided thereon, and as shown in FIG. In some cases, a recording layer is further provided on one of the low resistance layers. Note that the structure itself of these electrostatic recording bodies is completely the same as the conventional one. As the support, as mentioned above, all conventionally known supports such as paper, synthetic paper, and plastic film can be used.

The ratio of zinc oxide and insulating resin in the low resistance layer is 2/1 ~
A range of 9/1 (weight ratio) is suitable.

Examples of insulating resins include organic solvent-based resins used in the photoconductive layer of conventional electrophotographic photosensitive materials as mentioned above, as well as emulsion types such as polyvinyl acetate, styrene-butadiene rubber, and acrylonitrile-butadiene rubber. Water-soluble types such as starch and polyvinyl alcohol can be used. A sensitizing dye may or may not be added, but if it is not added, an ultraviolet lamp with emission characteristics of 385 mμ, which is the characteristic absorption wavelength of zinc oxide, e.g. For example, mercury lamps, fluorescent lamps, xenon lamps, etc. must be used.

In addition to these lamps, white light lamps such as halogen lamps can be used in cases where sensitizing dyes are added. The thickness of the low-resistance layer varies depending on the ratio of zinc oxide and resin, but is generally 5 to 209/I (3 to 20μ) in terms of coating amount.
It is.

The insulating recording layer is formed by applying an insulating resin solution.

As the insulating resin used here, all conventionally known insulating resins can be used, such as polystyrene, acrylic resin, vinyl chloride-vinyl acetate copolymer, polyacetal, epoxy resin, polyester, etc. In the case of a structure as shown in Figure 3, it is desirable to use a solvent that does not dissolve the binder resin used for the lower low resistance layer 2 or 2'; It is desirable to surface-treat the side to which the recording layer is applied in advance with a solvent-resistant substance such as starch or polyvinyl alcohol. In addition, inorganic pigments such as titanium oxide and tare can be added to the recording layer to provide writability.In addition, when forming an electric image on an electrostatic recording medium with a structure as shown in Figure 3, exposure to light is necessary. It is desirable to perform this from both the recording layer surface and its back surface.

The present invention will be explained below with reference to Examples.

Example 1 100 parts by weight of photoconductive zinc oxide, 1 part by weight of 5% methanol solution of rose bengal, and 150 parts by weight of toluene were added to 40 parts by weight of a 70% xylene solution of silicone resin, and dispersed in a ball mill for 10 hours. The liquid was coated with a bar coater on one side of a polyvinyl chloride film having a basis weight of 509/7rI so that the solid content was 159/771, respectively, to form a low resistance layer.

On the other hand, 100 parts by weight of a 20% methanol solution of polyvinyl acetate and 5 parts by weight of titanium oxide were dispersed for 1 hour using a homomixer, and this dispersion was coated on the low resistance layer to a coating weight of 59/m2 and recorded. An electrostatic recording medium was created by providing layers. Example 2 40% toluene solution of polymethyl methacrylate 100
100 parts by weight of photoconductive zinc oxide, 20 parts by weight of toluene
0 parts by weight was added and dispersed in a ball mill for 10 hours, and this dispersion was coated in a coating weight of 109/T on a base paper with a basis weight of 709/7rI.
A low-resistance layer was formed by coating with a bar coater so as to have a coating film of fl.

A 10% aqueous solution of polyvinyl alcohol was coated with a bar coater on the side opposite to the low resistance layer of this base paper to a coating weight of 29/I to form a precoat layer. A dispersion consisting of 100 parts by weight of solution and 5 parts by weight of clay (dispersion was carried out in a homomixer for 1 hour) was coated with a bar coater to give a coating weight of 59/I to form a recording layer to prepare an electrostatic recording medium. Example 3 100 parts by weight of photoconductive zinc oxide, 60 parts by weight of carboxyl-modified vinyl acetate emulsion (solid content 50%), 1 part by weight of a 5% methanol solution of rose bengal, and 240 parts by weight of water.
Parts by weight were added and dispersed in a ball mill for 10 minutes, and this dispersion was coated on both sides of high-quality paper with a basis weight of 509/ml using a bar coater to form a low resistance layer at a coating weight of 79/ml.

This low-resistance base paper is supercalendered, and a dispersion of 100 parts by weight of a 20% polystyrene toluene solution and 5 parts by weight of titanium oxide (dispersion is carried out in a homomixer for 1 hour) is coated on one side using a bar coater. An electrostatic recording paper was prepared by applying a recording layer so as to give a coating ratio of 59/A. Example 4 200 parts by weight of a 10% aqueous solution of polyvinyl alcohol and 200 parts by weight of water were added to 100 parts by weight of photoconductive zinc oxide,
The mixture was dispersed in a ball mill for 10 hours, and then coated on both sides of a high-quality paper with a basis weight of 509/l to a coating weight of 109/l on each side and dried using a bar coater.

The obtained low-resistance base paper was supercalendered, and a recording layer was provided thereon in the same manner as in Example 3 to produce an electrostatic recording paper. On the other hand, in Example 4, ECR-34 (33% aqueous solution of polyvinylbenzyltrimethylammonium chloride manufactured by Tau Chemical Co., Ltd.) 15
parts by weight and 50 parts by weight of a 10% aqueous solution of polyvinyl alcohol, and the adhesion amount was 39/7rI.
Comparative electrostatic recording paper was prepared in the same manner as above.

Next, images were formed on the above electrostatic recording paper using a commercially available facsimile machine at 20° C. under environmental conditions of 10%, 65% and 90% RHO.

Incidentally, development was carried out using the developer attached to the same device. In addition, for Examples 1 and 4, the xenon lamp, Example 2
and 3 before image formation using a halogen lamp,
That is, immediately before voltage application, both sides were exposed with an exposure amount of 1001 ux-Sec. The results are shown in the table below. As can be seen from this table, the image density of the product of the present invention is higher than that of the comparative product by about 1.5 at low humidity and by more than 0.2 at high humidity.
The products of the present invention are also superior to comparative products in terms of white spots at high humidity.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of an electrostatic recording medium of the present invention and a conventional electrostatic recording medium, respectively. 1...Support, 2,2t...Low resistance layer,
3...Recording layer.

Claims (1)

[Claims] 1. A low-resistance layer containing photoconductive zinc oxide and an insulating resin as main components on one or both sides of the support, and furthermore, what is the low-resistance layer on this low-resistance layer or on the support? After irradiating ultraviolet rays or white light to the low resistance layer of an electrostatic recording medium that has a recording layer mainly composed of an insulating resin on the opposite side, the recording layer is formed by applying a voltage between the recording electrode and the counter electrode. An electrostatic recording method characterized by forming an electrostatic charge image on the surface. 2. An electrostatic recording material having a low resistance layer on one or both sides of a support, and further having a recording layer mainly composed of an insulating resin on the low resistance layer or on the opposite side of the support from the low resistance layer. An electrostatic recording medium according to claim 1, wherein the low resistance layer is mainly composed of photoconductive zinc oxide and an insulating resin.