JPH0234018B2 - DENSHISHASHINYOKANKOZAIRYO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a ZnO dispersed electrophotographic photosensitive material. More specifically, the present invention relates to the above-mentioned photosensitive material, which can quickly convert the persistent electrically conductive state that occurs in the photosensitive layer upon exposure to a dark non-conductive state, partially or completely, by applying thermal energy. Prior Art ZnO photoreceptors have the advantages of being low cost and non-polluting, and have therefore been widely used as photoreceptors for electrophotography. Furthermore, in recent years, in order to achieve further miniaturization, lower cost, and higher reliability of electrophotographic devices using ZnO photoreceptors, consideration has been given to omitting the use of a corona discharger such as a corotron.
Measures to omit the transfer corotron include transfer using an intermediate, bias roller transfer using a conductive brush or rubber roller, and the like. Furthermore, as a means to omit the use of a charging corotron, there is a charging development method that utilizes the sustained photoconductivity of the ZnO photoreceptor, that is, the property that the conductive state generated by exposure is maintained for a long time even after the exposure is completed. A developing method called . In this development method, a persistent photoconductive photoreceptor is imagewise exposed to form a conductive pattern consisting of a conductive state in exposed areas and a non-conductive state in unexposed areas, and then a conductive pattern is formed on a sleeve to which a bias voltage is applied. A toner image corresponding to a conductive pattern is formed on a photoreceptor by developing it using conductive or semiconductive toner held on the photoreceptor. As is clear from the above description, this development method consists of exposure and development steps, and has the advantage of not requiring a charging step, which is an essential step in ordinary electrophotography. Incidentally, since the ZnO photoreceptor has sustained photoconductivity as described above, it is necessary to return the conductive state to the non-conductive state by some means in order to use the photoreceptor quickly and repeatedly. In an electrophotographic apparatus using a normal ZnO photoreceptor, the photoreceptor is restored from a conductive state to a non-conductive state by corona irradiated from a corona discharger such as a transfer corotron or a charging corotron. Allows rapid repeated use. Thus, in order to realize a system that does not use a corona discharger, it is necessary to provide a function for restoring a sustained photoconductive state to a non-conductive state instead of corona ions. One conceivable way to do this is to heat the photosensitive layer. That is, the photosensitive layer is heated at a predetermined temperature for a predetermined time using external heating means such as an infrared lamp or a heating roller. However, for ZnO photoreceptors commonly used in electrophotography, sufficient recovery is only achieved through slow and slow procedures, such as heating for more than 10 seconds at a temperature of 100°C. It's nothing more than that. Therefore, there is a great demand for a ZnO photosensitive material with rapid recovery performance, and its development is expected. Furthermore, it is conceivable to form a conductive pattern latent image as described below by utilizing the sustained photoconductivity of the ZnO photoconductor and its thermal recovery properties. That is, the entire surface of the ZnO photoreceptor is first exposed to light to make it conductive, and then a thermal pattern is applied image-wise to the photosensitive layer, which is in a sustained conductive state, to restore that area to a non-conductive state, and the thermal pattern is It is conceivable to form a conductive pattern latent image according to the Furthermore, by performing image exposure instead of full-surface exposure, it is possible to synthesize the exposed surface image and the thermal pattern image, which consist of the conductive state of the exposed and non-heated area and the non-conductive state of the non-exposed area and the exposed and heated area. Formation of a conductive pattern latent image is considered. A thermal head, laser beam irradiation, etc. can be considered as means for applying a thermal pattern in forming these latent images, but in order to quickly achieve the above-mentioned latent image formation by these heating means, rapid thermal recovery performance is required. It is desired to develop a ZnO photosensitive material having the following properties. Purpose of the Invention Under these circumstances, the present inventors have conducted intensive research to develop a ZnO photosensitive material with rapid heat recovery properties.
As a result of our studies, we found that the addition of a specific aromatic compound is effective in improving heat recovery properties, and we were able to meet the above requirements. Therefore, the main object of the present invention is to provide a ZnO photosensitive material that has rapid thermal recovery at relatively low temperatures without impairing the sensitivity of the photoreceptor. Structure of the Invention The above and other objects of the present invention can be achieved by incorporating at least one aromatic compound having at least one nitro group into a light-sensitive material. That is, the present invention converts a photosensitive layer made of a ZnO dispersed photosensitive material into a sustained photoconductive state by exposing it to light, and converts it into a non-conductive state by partially or completely applying thermal energy to the photosensitive layer. An electrophotographic photosensitive material used in an electrophotographic method, which comprises a step of restoring the photosensitive layer to a bias voltage and developing the photosensitive layer using a conductive or semiconductive toner held on a sleeve to which a bias voltage is applied. In the photosensitive material, 5-nitrosalicylic acid, 4-
The present invention relates to an electrophotographic light-sensitive material containing at least one aromatic compound selected from nitro-2-chloroaniline, 2,5-dinitrophenol, and 2,4-benzoic acid. The compounds added to the ZnO dispersed photosensitive layer used in the present invention include 5-nitrosalicylic acid, 4-nitro-2-chloroaniline, 2,5-
At least one aromatic compound selected from dinitrophenol and 2,4-dinitrobenzoic acid. These nitro derivatives are added in a total amount of 0.01 to 5.0% by weight, preferably 0.05 to 2.0% by weight, based on the amount of ZnO powder.
It is used in an amount such that it ranges from % to % by weight. Effects of the Invention Thus, according to the present invention, the ZnO dispersed photosensitive material can obtain the following excellent benefits based on the addition of a predetermined amount of an aromatic compound containing at least one nitro group. In other words, it is possible to obtain a ZnO-dispersed photosensitive material that has rapid thermal recovery properties at relatively low temperatures and does not cause a decrease in sensitivity. This makes it possible to omit the use of a corona discharger, making it possible to achieve further miniaturization, lower cost, and higher reliability of the device. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to these Examples in any way. Example The compounds shown in the table below were separately added to the basic components shown below, and mixed thoroughly using a ball mill to prepare a photoconductive layer forming liquid.Then, this dispersion was applied to conductive treated paper. Film thickness after drying is 5~
Coat to a thickness of 7 μm, dry at 70℃ for 1 hour,
A photoreceptor was prepared by leaving it in a dark place overnight. [Basic ingredients] ZnO powder (Sakai Chemical, SEF-100) 45g A-405 (Nippon Reichhold, acrylic resin)
10g Rose Bengal 45mg Butyl acetate 5g Toluene 20g

[Sensitivity measurement]

The prepared photoreceptors No. to No. were subjected to step wedge exposure using an ND filter.
Sensito is created based on the developed density by contacting the conductive toner (10 ⁴ Ωcm) held on a developing roll to which a developing bias of 500 V is applied with the conductive surface on the back of the photoconductor while grounded. Relative sensitivity (based on additive-free photoreceptor No.) was calculated from the measurement curve. [Heat recovery measurement] Each photoreceptor was irradiated with a light amount 10 times the appropriate light amount for each photoreceptor determined from the sensitivity measurement above, and then pressed against a hot plate heated to each temperature for 0.4 seconds.
After cooling, development was carried out in the same manner as in the sensitivity measurement, and the developed density at each heating temperature was plotted on a graph, and the temperature value at which the developed density recovered to 1.0 (Macbeth density indicator) was taken as the target value for heat recovery. Therefore, the lower this temperature value is, the better the heat recovery property is. Table 2 shows the measurement results of the sensitivity and heat recovery properties of each photoreceptor. As can be seen from Table 2, the photoreceptor to which the nitro group-containing aromatic compound of the present invention is added has superior heat recovery properties and sensitivity compared to the photoreceptor without additives, and changes from a sustained conductive state to a non-conductive state. It can be used in systems that utilize heat recovery. On the other hand, it can be seen that the photoreceptor to which copper stearate was added showed an improvement in thermal recovery properties, but at the same time, the sensitivity decreased.

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Claims (1)

[Claims] 1 Including the step of restoring the sustained photoconductive state produced by exposing a photosensitive layer made of a ZnO dispersed photosensitive material to a non-conductive state by partially or fully applying thermal energy to the photosensitive layer. , an electrophotographic photosensitive material used in an electrophotographic method comprising developing the photosensitive layer using a conductive or semiconductive toner held on a sleeve to which a bias voltage is applied; 5-nitrosalicylic acid, 4-nitro-2-
Chloroaniline, 2,5-dinitrophenol,
A light-sensitive material for electrophotography, characterized in that it contains at least one aromatic compound selected from 2,4-dinitrobenzoic acid.