JPS599904B2 - Electrophotographic materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an electrophotographic photosensitive material having a cadmium sulfide/resin dispersion photoconductive layer.

Cadmium sulfide is known as a photoconductor with fast photosensitivity, but when it is used together with a binding resin as a photoconductive layer of an electrophotographic photosensitive material, its electrophotographic properties deteriorate significantly due to environmental changes. If CdS is contained in a larger amount than the binder resin, the particle size of the binder cannot be made fine, resulting in a severely rough surface.Although the sensitivity improves, charge application becomes very poor. Adhesion to the support becomes poor. It is difficult to obtain a practical electrophotographic material, as the mechanical strength decreases and, on the other hand, if the CdS content is relatively small, the sensitivity becomes extremely poor. Furthermore, in either case, there is a risk that CdS may be exposed on the surface, which poses a toxicity problem, and there are also problems such as discharge breakdown being likely to occur and fatigue remaining. In any case, Cd5-resin dispersion systems have many drawbacks as electrophotographic light-sensitive materials for ordinary Carlson processes, and the excellent photosensitivity of CdS cannot be effectively utilized. In order to improve these drawbacks, proposals have been made to change the layer structure of the photosensitive material as well as the latent image forming process (for example, Japanese Patent Publications Nos. 42-23910 and 48-2965).
However, if the layer structure is changed, for example, a protective layer is provided on the Cd5~resin dispersion photoconductive layer and the photosensitive material is considered to be reusable, providing the protective layer itself does not pose much of a problem in terms of cost, but the process (which is generally more complicated than the charging-imagewise exposure-developing steps of the Carlson process) will complicate various aspects of the copying machine, resulting in increased costs and is industrially disadvantageous. The present invention improves the above-mentioned drawbacks of Cd5~resin dispersion photosensitive materials.
The present invention provides an electrophotographic light-sensitive material that can be directly applied to the ordinary Carlson process.

Further, the present invention provides a new electrophotographic light-sensitive material that can be copied without impairing the high photosensitivity inherent to CdS.

Therefore, the present invention provides an electrophotographic material that is highly sensitive, has excellent weather resistance and durability, and is free from toxicity.

Such a photosensitive material is prepared by sequentially providing a cadmium sulfide-resin dispersion layer and a 2,5-bis(p-dialkylaminophenyl)-1,3,4-oxadiazole-resin dispersion layer on a conductive support. It is what it is.

This oxadiazole derivative used in the present invention has good resin dispersibility and solvent solubility, and is effective as a charge transfer layer. In the present invention, the CdS-containing layer functions to generate conductive carriers upon irradiation with light, and the oxadiazole-containing layer functions to store charges and transport carriers generated in the CdS-containing layer.

In this case, the photosensitive material exhibits high sensitivity only when negatively charged.
The following may be the reason why the photosensitive material of this combination exhibits high sensitivity. This will be explained using drawings. In the figure, when the photosensitive material 1 is negatively charged and subjected to imagewise exposure,
A hole-electron pair is generated near the surface of the CdS-containing layer 3 by the light irradiation. Since CdS is an n-type semiconductor and has the property of allowing electrons to move easily, the hole-electron pair dissociates and only the electron immediately moves to the conductive support 4 on the ground side, leaving behind a hole. On the other hand, oxadiazole (2 is the oxadiazole-containing layer) is an electron-donating substance in which holes move easily, so C
The holes remaining near the surface of the dS-containing layer move through the oxadiazole and neutralize the negative charges on the surface of the CdS-containing layer.
In this way, the CdS-containing layer only has to function to generate carriers, so the CdS-containing layer only needs to be thick enough to generate carriers, can be made quite thin, and can contain a large amount of CdS. can be set. Therefore, the CdS-containing layer of the present invention can produce a large amount of effective carrier. If an electrophotographic photosensitive material is formed using only a thin layer containing a large amount of CdS, the sensitivity will be improved, but it will be extremely difficult to apply a charge, making it impractical, and the thickness of the layer will increase considerably. However, the application of charge is not so easy, and moreover, carrier traps are more likely to occur inside, and the sensitivity tends to decrease. In any case, C
An electrophotographic light-sensitive material formed only of a layer containing a large amount of dS is not practical due to its reduced mechanical strength, poor surface properties, and poor rutting resistance. The present invention has discovered that a thin layer containing a large amount of 0dS makes it difficult to apply a charge, but has very good sensitivity. Furthermore, by providing an oxadiazole-containing layer on top of the thin layer, it is possible to easily apply a charge. becomes, and Cd
This is based on the discovery that oxadiazole is extremely effective for injection and transfer of carriers produced with S content.

In addition, since oxadiazole is used together with a binder resin that has excellent film performance, the unevenness of the underlying CdS surface is hidden.
Therefore, the surface of the photosensitive material of the present invention is smooth, mechanical strength is improved, toner can be easily transferred to paper, and CdS
Since the material is completely shielded, weather resistance is improved, and an electrophotographic light-sensitive material with excellent repeatability in all aspects can be obtained.

As mentioned above, the CdS-resin dispersed layer of the present invention preferably has a larger amount of CdS than the resin (50% by weight or more) and is relatively thin (about 1 to 10 microns).

In the oxadiazole-resin dispersed layer, the oxadiazole content is preferably about 1/3 to 3/1 weight ratio to the resin, and the thickness is preferably about 5 to 100 microns. C
dS ~ Polyester, styrene resin, acrylic resin, polyethylene, polyvinyl chloride, polyvinyl fluoride, epoxy resin, polyurethane, etc. are effective as the binder resin for the resin dispersion layer, and polyester is effective as the resin for the oxadiazole-containing layer. , styrene resin, polyvinylcarbazole, polyamide, polyisobutyl methacrylate, polymethylenepyrene, polyethylene, etc. are effective.

Note that the resins used for these layers may be the same or different. The present invention will be explained in more detail below using examples using 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole.
The present invention is not limited to these.

A solution having the composition according to the example was dispersed for 1 hour using an ultrasonic disperser, and the dispersion was applied with a doctor blade onto an aluminum-deposited polyester film.
It was dried at ℃ for 1 hour to form a 4μ thick CdS-containing layer.

Further, a solution having the following formulation was applied thereon using a doctor blade and dried at 100° C. for 10 minutes to form an oxadiazole-containing layer having a thickness of 11 μm, thereby obtaining an electrophotographic light-sensitive material.
Polyester (Polyester Adhesive 48000 manufactured by DuPont, USA) 7.5t The rolled photosensitive material had excellent flexibility and could be tightly wrapped.

On the other hand, for comparison, a film with a thickness of 15 μm was placed on the same conductive support.
An electrophotographic material having a CdS-containing layer having the same formulation as above was prepared.

Next, these photosensitive materials were negatively charged by -6.0 KV corona discharge, and after being irradiated with 20 lux white tungsten light, the exposure amount E1/ was applied to reduce the surface potential to 1/2.
2 (lux/second) Exposure amount E1 which also attenuates to 1/10
/10 (lux/second) was measured.

The results are shown in the table below. As can be seen from this table, the exposure amount (sensitivity) of the photosensitive material of the present invention is almost the same as that of the CdS-containing layer only, and it can be seen that the surface potential is increased. Next, the dry-developed or wet-developed image was electrostatically transferred to high-quality paper using a known method, and when fixed, a positive image faithful to the original image without background stains was obtained. Even after repeating the above steps and copying 50,000 copies, the photosensitive material of the present invention having an oxadiazole-containing layer did not show any decrease in sensitivity or image disturbance. Even when the same process was repeated in a high humidity atmosphere, no image bleeding or bleeding was observed. On the other hand, in the case of the comparative light-sensitive material without the oxadiazole-containing layer, the image density obtained was very low and blurry, and the CdS-containing layer peeled off from the support after the process was repeated several times. .

[Brief explanation of the drawing]

The figure is an explanatory diagram showing the state of charge when an electrostatic latent image is formed on the photosensitive material of the present invention. 1... Electrophotographic photosensitive material, 2... Oxadiazole containing layer, 3... CdS containing layer, 4
... Conductive support.

Claims (1)

[Claims] 1 Sequentially cadmium sulfide to resin dispersion layer and 2,5-bis(p-dialkylaminophenyl) on a conductive support.
-1,3,4-oxadiazole - An electrophotographic light-sensitive material provided with a resin dispersion layer.