JPH0217101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an electrophotographic photoreceptor having a photosensitive layer made of a material containing selenium as a main component, and a method for manufacturing the same.

[Prior art and its problems]

As for the characteristics of a selenium photoreceptor for electrophotography, it is desirable that the surface charge (electrostatic potential) applied to the photosensitive layer be sufficiently retained in the dark, and that the surface charge be quickly dissipated during light exposure. It is required that the potential of the photoreceptor after exposure, that is, the residual potential (fatigue characteristics), does not increase when exposure is repeated. This is because, if the residual potential is high, development such as scumming, density reduction, and ghosting will appear in actual images, resulting in deterioration of image quality due to continuous copying. The cause of fatigue is that carriers generated during light irradiation are captured in a trap level during transport. The higher the trap level density of the photosensitive layer, the higher the residual potential, and during the process of repeated image formation, this residual potential is accumulated, leading to a decrease in image quality.

[Purpose of the invention]

In contrast, it is an object of the present invention to provide a selenium photoreceptor for electrophotography that exhibits excellent fatigue characteristics and exhibits little increase in residual potential even during repeated image formation.

[Key points of the invention]

The present invention originates from the recognition that trap levels are based on structural defects in selenium, and in order to reduce structural defects, that is, dangling bonds, by forming a photosensitive layer rich in cyclic selenium among selenium allotropes. It crushes the terminal group. According to the present invention, 60% of the photosensitive layer is a layer involved in carrier transport.
It has the above cyclic selenium content. The layers involved in carrier transport include the entire photosensitive layer in the case of a single layer photosensitive layer;
In the functionally separated photosensitive layer, it means a carrier transport layer. A layer with a cyclic selenium content of 60% or more is
It can be produced by vapor depositing a selenium material having a cyclic selenium content of 75% or more as an evaporation raw material.

[Embodiments of the invention]

Selenium material used for vapor deposition Pure selenium or a selenium alloy with a specified composition is transferred from a melting tank to a low-temperature liquid.
For example, it may be dropped into pure water, rapidly solidified, and made into granules. Figure 1 shows the relationship A between the cyclic selenium content of the selenium vapor deposition material and the quenching temperature (selenium melt temperature immediately before quenching and solidification), and the relationship between the cyclic selenium content and the glass transition point B and the residual potential of the manufactured photoreceptor. Relationship C is shown. The photosensitive layer of the photoreceptor has a carrier transport layer with a thickness of 55 μm made of Se-Te alloy containing 5.5% Te on an aluminum cylindrical substrate, and a carrier transport layer with a thickness of 13.5 μm.
% of Te and a 5 μm thick carrier generation layer made of Se-Te alloy, each of which was evaporated from an evaporation source heated to 320°C on a substrate heated to 50°C in a vacuum chamber at 10 ^-5 Torr. Formed by vapor deposition of material. The residual potential shows the value after repeated copying 1000 times.

FIG. 2 shows the relationship between the cyclic selenium content in the evaporated raw material and the cyclic selenium content in the vapor deposited layer. Figure 1c
As is clear from the above, as the cyclic selenium content in the evaporated raw material increases, the residual potential decreases, and this is due to the second
As is clear from the figure, the cyclic selenium content in the deposited layer also increases. The residual potential of the photoreceptor
In order to achieve a voltage of 40 V or less, the cyclic selenium content in the evaporation raw material must be 75% or more, and the cyclic selenium content in the vapor-deposited photosensitive layer must be 60% or more.

As is clear from FIG. 1A, a selenium raw material having such a high cyclic selenium content must be produced by rapidly cooling and solidifying a selenium material melted at a temperature of 300° C. or less.

FIG. 3 shows a conventional evaporation raw material manufacturing apparatus, in which a Se-Te alloy 2 is placed in a melting tank 1, and while the atmosphere inside the tank is stirred by a fan 3, a heater 4 is used to heat the Se-Te alloy.
-Te alloy 2 is melted. The Se-Te alloy 2 is melted at 400°C by controlling the input to the heater 4 using a thermocouple (temperature detector) 5. When the temperature reaches 370°C, it is dropped into pure water 7 from a nozzle 6 to form granules. Selenium evaporation raw material is obtained. In this case, the temperature of the alloy gradually decreases to about 320°C. When producing evaporated raw materials using such an apparatus, it is difficult to lower the quenching temperature because if the temperature of the melt 5 is set to 250° C., the portion of the nozzle neck 61 in contact with the wall will solidify.

FIG. 4 shows an example of an apparatus for producing evaporative raw materials according to the present invention, and parts common to those in FIG. 3 are given the same reference numerals. In this case, the fan 3 is immersed in the molten alloy 2 and can stir the molten alloy to make the temperature uniform. A thermocouple (temperature detector) 5a is also attached to the nozzle 6, and the input to the heater 41 wound around the nozzle neck 61 is controlled to prevent the alloy 2 from solidifying within the nozzle neck 61. As a result, the alloy is melted at 400° C., then lowered to 250° C., and dropped into pure water from the nozzle 6 to obtain an evaporated raw material with a high cyclic selenium content. Note that setting the atmosphere in the melting tank 2 and the atmosphere between the nozzle 6 and the pure water 7 to be a nitrogen atmosphere is effective in reducing the oxygen content in the evaporation raw material and the photosensitive layer and lowering the residual potential. .

FIG. 5 shows the fatigue characteristics of photoreceptors in which photosensitive layers were deposited using the evaporation materials produced by the apparatuses shown in FIGS. 3 and 4, respectively. Dashed lines 11 and 12 indicate the photoreceptor of the embodiment of the present invention in which the carrier transport layer as described above was formed using the Se-Te alloy manufactured by the apparatus shown in FIG. The solid lines 21 and 22 indicate the charged potential before exposure, and the solid lines 21 and 22 represent the photoconductor of a comparative example in which the carrier transport layer was formed using a Se-Te alloy manufactured by the apparatus shown in FIG.
1 indicates the residual potential, and line 22 indicates the pre-exposure charge potential.

〔Effect of the invention〕

The present invention provides a photosensitive layer made of a selenium material with a cyclic selenium content of 0% or more, thereby making it possible to obtain images with low fatigue and free from background smudges, ghosts, etc., and to reduce density loss due to continuous repeated image formation for use in electrophotography. A photoreceptor is obtained. Such a photoreceptor can be easily formed by increasing the cyclic selenium content of the evaporation raw material used for vapor deposition of the photosensitive layer to 75% or more, and is used as a photoreceptor with good fatigue characteristics in PPC copying machines,
It can be used extremely effectively in printers, intelligent copying machines, etc.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the molecular structure of selenium materials, quenching temperature, glass transition point, and residual potential.
Figure 2 is a diagram showing the cyclic selenium content in the evaporation raw material and the deposited film, Figure 3 is a conventional evaporation raw material manufacturing apparatus, and Figure 4 is an example of the evaporation raw material manufacturing apparatus for implementing the present invention. The cross-sectional view and FIG. 5 are fatigue characteristic diagrams of a photoreceptor according to an embodiment of the present invention and a conventional example.

Claims (1)

[Scope of Claims] 1. Electrophotography having a photosensitive layer made of a material containing selenium as a main component, characterized in that a layer involved in carrier transport in the photosensitive layer contains 60% or more of cyclic selenium. Photoreceptor for use. 2 Among the photosensitive layers, the layer involved in carrier transport is
1. A method for producing an electrophotographic photoreceptor, characterized in that the electrophotographic photoreceptor is formed by vapor deposition using a selenium-based evaporation raw material containing 75% or more of cyclic selenium.