JPH073596B2 - Electrophotographic photoreceptor and method for manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor using amorphous selenium or an amorphous selenium alloy as a photoconductive material, and a method for producing the same.

[Prior Art and its Problems] As for the performance of an electrophotographic photoreceptor (hereinafter, also simply referred to as a photoreceptor) used as an image forming member of an electrophotographic apparatus, it has a high ability to accept electric charges and is sufficiently high in a dark place. It can be charged to the required potential, and in the dark there is little leakage of charge and the charge decay rate is small, so that the charged position can be maintained.When light is irradiated, the charged charge on the surface is quickly discharged and the charged position is It is required to be attenuated so that the residual potential is sufficiently small, fatigue is negligibly small when charging and exposure are continuously repeated, dark decay is increased, and residual potential is less accumulated.

In order to satisfy such a demand, a function-separated type photoconductor has recently attracted attention. This is a photoconductor obtained by laminating a carrier transport layer mainly contributing to charging in the dark and carrier transport at the time of exposure, and a carrier generating layer mainly contributing to generation of carriers at the time of exposure. By pursuing the optimum design according to the function of each separated layer, it is possible to obtain a photoreceptor having excellent characteristics as compared with a single layer type photoreceptor in which one layer has these functions.

A function-separated type has also been developed in a photoconductor that uses a selenium-based material as a photoconductive material.For example, a carrier transport layer made of amorphous selenium or an amorphous selenium-tellurium alloy and an amorphous material are formed on a substrate made of an aluminum alloy. A photoreceptor having a carrier generation layer made of a selenium-tellurium alloy or an amorphous selenium-tellurium-arsenic alloy is known. However, when continuous image formation is carried out with such a photoreceptor, residual potential is accumulated as shown in FIG. 3, and as a result, scumming occurs on the image, and so far the residual potential is accumulated. A satisfactory photoconductor having a small number of particles has not been obtained.

[Object of the Invention]

The present invention has been made in view of the above points, and the residual potential is less accumulated even when image formation is continuously repeated,
An object of the present invention is to provide a photoconductor having less image background stain and a method for producing the photoconductor.

[Main points of the invention]

The object of the present invention is to evaporate selenium or a selenium alloy in a vacuum chamber to form a charge transport layer on a conductive substrate and simultaneously evaporate the oxide of tungsten to generate 50 × oxygen in the charge transport layer. It is achieved by doping 10 ^-6 atomic% to 200 × 10 ^-6 atomic% and tungsten with 15 × 10 ^-6 atomic% to 110 × 10 ^-6 atomic.

Example of Invention

 Examples of the present invention will be described below.

FIG. 1 is an explanatory view showing a vapor deposition method of a charge transport layer at the time of manufacturing a photoreceptor according to the present invention, in which a cylindrical conductive substrate made of an aluminum alloy is placed in a vacuum chamber (not shown). 1 is rotatably arranged in the direction of an arrow, a vapor deposition boat 2 filled with a selenium-tellurium alloy 4 is installed below it, and a flash vapor deposition boat 5 is juxtaposed in close proximity to the vapor deposition boat 2. The flash evaporation boat 5 is a system in which the boat is directly energized and heated. Pressure in vacuum chamber 1 × 10
A vacuum of ^-5 Torr is applied, the substrate 1 is kept at a temperature of 65 ° C., and the vapor deposition boat 2 is heated to about 300 ° C. while rotating by a heater 3.
Then, the selenium-tellurium alloy 4 containing 5.5% by weight of tellurium is evaporated. At the same time, the flash vapor deposition boat 5 is energized to raise its temperature to 1000 ° C. or higher, and tungsten oxide WO ₃ fine powder (shown on the grains for convenience in the figure) is supplied little by little to flash vaporize, and the vapor is selenium. Co-evaporated on the substrate 1 with tellurium vapor to form a charge transport layer with a thickness of about 60 μm at a deposition rate of about 1 μm / min. WO ₃
Is 500 ppm by weight in proportion to the amount of selenium-tellurium alloy.
Supplied. The content of oxygen and tungsten in this way the charge transport layer formed by were examined by neutron activation analysis, oxygen is 100 × 10 ^-6 atomic%, tungsten 40 × 10 ^-6
It was atomically doped. Next, a charge generating layer made of an amorphous selenium-tellurium-arsenic alloy and having a film thickness of 5 μm was formed on the charge transporting layer to obtain a photoreceptor.

Images were continuously and repeatedly formed on the photoconductor of this example, and the residual potential of the photoconductor at that time was examined. The results are shown in FIG. As shown in Fig. 2, the residual potential is very small, about 10V at the beginning, and the increase thereafter is very small, and it saturates at about 20V within the first few repetitions, and then the residual potential up to 250 times. No accumulation of is seen. In addition, the background stain on the image was not recognized.

In Comparative Example 1, a photoreceptor was prepared in the same manner as in Example 1 except that WO ₃ was not flash-deposited in the formation of the charge transport layer, and the photoreceptor of this Comparative Example was subjected to continuous repeated image formation and remained. When the electric potential was examined, the initial value was about 30
It was as large as V, then increased to 80V at 50 times and 100V at 100 times, and increased to 25
A large accumulation of about 130V was seen at 0 times, and the background stain on the image occurred. Moreover, the two cases with the addition of tungsten alone 10,150 × 10 ^-6 at% without flash evaporation of WO ₃ in Example Comparative Example 2, only oxygen without flash evaporation of WO ₃ in Example Comparative Example 3 50,200 × 10 as selenium oxide
^A total of 4 cases of photoconductors were prepared, including 2 cases in which ^-6 at% was added. Table 1 shows the residual potential and the charge retention ratio in the dark as a result of continuously and repeatedly forming images with these photoreceptors.

From Table 1, even if the addition amount of tungsten alone was changed, the charge retention ratios in the dark were all good, but the residual potentials were all high, and the background stain on the image occurred. Also, the result of repeated imaging with only oxygen by doping in the form of selenium oxide shows that the point of residual potential does not rise much,
It was found that the charge retention rate in the dark became too small.
From these comparative examples, it can be seen that the co-evaporation of WO ₃ in this example described above is extremely effective.

The saturation value of the residual potential when images are continuously and repeatedly formed depends on the oxygen content in the charge transport layer. When the oxygen content is low, the saturation value is high, and when it is high, the saturation value is low. At that time, as is clear from the results shown in Table 1, the coexistence of tungsten is important, and the coexistence of tungsten uniformly and stably dopes oxygen into the amorphous selenium or the amorphous selenium-tellurium alloy. As a result, a photosensitive member having stable characteristics can be obtained. When the amount of oxygen in the charge transport layer is about 50 × 10 ^-6 atom% and the amount of tungsten is about 15 × 10 ^-6 atom%,
The saturation level of the residual potential is about 80 V, and when it is smaller, the saturation value becomes too large and the background stain on the image becomes a practical problem.
Further, FIG. 4 showing the relationship between the number of times of continuous image formation and the residual potential with the composition ratio of tungsten and oxygen as a parameter, and FIG. 5 showing the relationship between the respective concentrations of tungsten and oxygen and the charge retention ratio in the dark. As you can see, the amount of oxygen is about 200 × 10 ^-6 atom%, and the amount of tungsten is 110 × 10 6.
^{At -6} atom%, the saturation value is around 10 V and no background stain is observed on the image, but on the other hand, the dark decay becomes large, and if the content of these increases further, the charge amount becomes lower and the charging Attenuation also becomes large and becomes a practical problem.

The reason why the residual potential of the photoconductor is less accumulated when the charge transport layer is doped with appropriate amounts of oxygen and tungsten has not been fully clarified. It is presumed that the level becomes shallow and the hole trap density is also reduced.

In this embodiment, WO ₃ was used as the doping material, but WO ₃ and W ₄ O ₁₁ can be effectively used as well.

〔The invention's effect〕

According to the present invention, when selenium or a selenium alloy is evaporated in a vacuum chamber to form a charge transport layer on a conductive substrate, tungsten oxide is evaporated at the same time, and oxygen is added to the charge generation layer at 50 ×. Dopant of 10 ^-6 atomic% to 200 × 10 ^-6 atomic% and tungsten of 15 × 10 ^-6 atomic% to 110 × 10 ^-6 atomic%. The electrophotographic photoconductor thus manufactured,
It is possible to stably provide a good image free from background stain, because residual electric potential is less accumulated even when continuous image formation is performed.

[Brief description of drawings]

FIG. 1 is an explanatory view of one embodiment of vapor deposition of a charge transport layer of the present invention, FIG. 2 is a diagram showing accumulation of residual potential of a photoreceptor of one embodiment, and FIG. FIG. 4 is a diagram showing the accumulation of residual potential, FIG. 4 is a diagram showing the relationship between continuous repetition and residual potential, and FIG. 5 is a graph showing the respective concentrations of tungsten and oxygen and the charge retention ratio in the dark (at 5 seconds after charging). It is a figure which shows a relationship. 1 ... Conductive substrate, 2 ... Deposition boat, 3 ... Heater, 4 ... Selenium alloy, 5 ... Flash deposition boat,
6 ... Tungsten oxide.

Claims (5)

[Claims] 1. An electrophotographic photoreceptor having a charge transport layer made of amorphous selenium or an amorphous selenium alloy and a charge generation layer made of an amorphous selenium alloy on a conductive substrate.
Electrons characterized in that the charge transport layer is doped with oxygen at 50 × 10 ⁻⁶ atomic% to 200 × 10 ⁻⁶ atomic% and tungsten is doped at 15 × 10 ⁻⁶ atomic% to 110 × 10 ⁻⁶ atomic%. Photoreceptor for photography. 2. When a selenium or selenium-tellurium alloy is evaporated from an evaporation source in a vacuum chamber to form a charge transport layer on a conductive substrate, an oxide of tungsten is simultaneously evaporated to form a charge transport layer in the charge transport layer. Oxygen to 50 × 10 ^-6 atom% to 200 × 1
0 ^-6 atom%, tungsten 15 x 10 ^-6 atom% ~ 110 x 10 ^-6
A method for producing a photoconductor for electrophotography, which comprises doping at an atomic percentage. 3. The method for producing an electrophotographic photoreceptor according to claim ₂ , wherein the oxide of tungsten is WO ₂ . 4. The method for producing an electrophotographic photoreceptor according to claim 2, wherein the oxide of tungsten is WO ₃ . 5. The method for producing an electrophotographic photosensitive member according to claim 2, wherein the oxide of tungsten is W ₄ O ₁₁ .