JPH0789231B2 - Amorphous Silicon Electrophotographic Photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application of the Invention> The present invention relates to an amorphous silicon electrophotographic photoreceptor. More specifically, the present invention relates to an amorphous silicon electrophotographic photosensitive member that does not cause image deletion in a high humidity environment.

<Conventional Technology> Conventionally, as electrophotographic photoreceptors, fine powders of CdS, ZnO, etc. dispersed and coated in an organic material, Se photoreceptors, polyvinylcarbazole, or the like, which are formed by adding As or Te and vapor deposition, Organic photo semiconductors (CPCs) such as trinitrofluorene have been used. More recently, plasma of silane gas (Si _n H _{2n + 2} )
The semiconductor physical properties of hydrogenated amorphous silicon (hereinafter a-Si) formed by the CVD method-especially the photoconductivity has attracted attention, and it has been studied as an electrophotographic photoreceptor along with its application to solar cells, optical sensors, image pickup tubes, etc. It is being advanced. Although a-Si is formed by the plasma CVD method using silane gas as the main raw material as described above, it has various characteristics (photoelectric voltage spectral sensitivity, printing durability) as a photoconductor for various purposes (plain paper copier, laser). Various efforts have been made to adapt and improve printers and fax machines. For example, adding diborane, ammonia, oxygen, hydrocarbon, germane (Ge _n H _{2n + 2} ), fluorinated silane, etc. to the source gas, and further changing the film composition on the metal substrate in the film thickness direction. Attempts have been made to form a multilayer structure. (These photoconductors containing silicon hydride as a base are hereinafter referred to as a-Si.) A-Si has the following excellent characteristics as compared with the above-mentioned existing photoconductors.

 It is non-polluting and non-toxic.

Thermally stable (crystallization temperature is 400 ° C or higher, crystallization temperature of Se is 60 ° C, and significantly higher thermal stability than photoreceptors using organic materials, OPC.ZnO, CdS) .

The photosensitivity is high and the photosensitive wavelength range is almost uniform in the entire visible light wavelength range.

High surface hardness (Vickers hardness of 1500 or more) and less susceptible to surface damage such as scratches.

Due to these advantages, a-Si has been attempted to be applied to high-speed PPCs, laser printers, facsimiles, etc. as high-performance electrophotographic photoreceptors, but it has the following problems.

<Problems to be Solved by the Invention> Initially, a-Si exhibited stable photoconductor performance even under various environmental conditions because of its chemical and thermal stability and high surface hardness as described above. It was expected that at the same time it would achieve high printing durability that would withstand copying. However, in reality, when electrophotographic copying is performed under high humidity, specifically, under conditions where the relative humidity exceeds 70%, a clear image cannot be obtained and the contour of the image is blurred, and under high humidity. It was found that a phenomenon in which no image was obtained (hereinafter referred to as "image deletion") occurred. This phenomenon becomes remarkable as the copying is repeated,
Generally, a normal PPC (plain paper copier) is charged several thousand times-
When exposure, development and transfer are performed, image deletion occurs under high humidity. However, it has been confirmed that even if an image deletion occurs in high humidity, a clear image can be obtained when copying is performed in low humidity again. Therefore, in order to prevent image deletion, the relative humidity in the vicinity of the surface of the photoconductor drum is always kept below -50% even if the a-Si photoconductor drum is constantly heated to 40 to 50 ° C and the ambient temperature changes. Measures can be considered,
In this case, the cost of the copying machine and the complication of the copying machine mechanism are inevitable due to the loading of the heater inside the drum and the installation of the temperature adjusting mechanism.

The problem to be solved by the present invention is that a-
It is the image deletion of the Si photoconductor.

<Means for Solving Problems> The present inventors arrived at the present invention through various studies to improve such problems.

The gist of the present invention lies in an amorphous silicon electrophotographic photosensitive member having a center line average roughness of 90 Å or less measured by a coordinate measuring scanning electron microscope and a cross-section measuring device.

The present invention will be described in detail below.

The surface of the a-Si photoconductor formed by the plasma CVD method is
It usually has fine irregularities derived from the manufacturing method and the Al tube. The surface roughness of a-Si photoconductors manufactured by various manufacturing methods was measured with a coordinate measuring scanning electron microscope "EMM-3000" and a cross-section measuring device "PMS-1" by Elionix Co., and the center line average roughness was 130Å. The front and back were general, and 110Å was the minimum.

As a method for reducing the surface roughness of the a-Si photoconductor, it is considered that the surface of the photoconductor after production is polished, the conditions of the film forming method are improved, or the surface roughness of the Al tube is lowered.

The inventors of the present invention have attempted to improve the surface roughness by polishing, and first, by polishing a photoreceptor immediately after production with a polishing substance that undergoes a solid-phase reaction with the surface of an a-Si photoreceptor, image deletion under high humidity can be achieved. We found that it could be prevented and filed a patent application (Japanese Patent Application No. 60).
-72355).

According to this method, the surface of the a-Si photosensitive member was polished into a belt shape with various polishing times. As a result of printing on a photoconductor drum having the polishing section, the non-polishing section caused image deletion at about 10,000 sheets, but the polishing section caused image deletion at high humidity even after exceeding 500,000 sheets. I got no good image quality. Detailed examination of the polishing conditions revealed that the effect of preventing image deletion depends on the surface roughness of the photoconductor.

Further, it has been found that the surface roughness of the photoreceptor due to polishing can be controlled by the polishing time if the polishing conditions such as pressure are constant, and that the surface roughness decreases when the polishing time is long.

Further, as a result of diligent study, the center line average roughness of the photoreceptor surface is 90 Å or less, preferably 60 Å or less, more preferably 30
It became clear that a remarkable effect would be exhibited if Å or less.

The definition of the center line average roughness R (a) is Is. Here, L is a measurement length, and y (x) is an actual measurement value.

In the present invention, an arbitrary 10 points were actually measured with a coordinate measuring scanning electron microscope "EMM-3000" and a cross-section measuring apparatus "PMS-1" manufactured by Elionix, and an average value of 10 points of R (a) calculated from the above definition was calculated. This is called center line average roughness. Furthermore, the measurement condition for obtaining the actually measured value is a magnification of 10,000 times, and the measurement length at this time is 12 μm.

The a-Si photoconductor of the present invention is required to satisfy the above-mentioned requirements for the center line average roughness, and it is further desirable to satisfy the following requirements.

The average value of any 10 points of the variance of the center line average roughness R _δ is
110 Å or less, preferably 80 Å or less, more preferably 50 Å
Being below.

The dispersion R _δ of the center line average roughness referred to here is in accordance with a conventional method, Required by. Here, y _i is the measured value, m is the average value of the measured values, and N is the number of data. If N is large, it is troublesome, and if it is small, the error becomes large.
Measure points.

Any 10-point average value of the maximum amplitude R (t) should be 500 Å or less, preferably 350 Å or less, and more preferably 200 Å or less.

The maximum amplitude R (t) refers to the difference between the maximum value and the minimum value in one measurement. It is preferable that the average value of arbitrary 10 points (measurement points) of the maximum amplitude R (t) is 500 Å or less.

Any 10-point average value of Rz (the difference between the average value of 5 points from the maximum value and the average value of 5 points from the minimum value) is 450 Å or less, preferably 350 Å or less, more preferably 250 Å or less.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded.

Example 1 Two a-Si photoconductor drums (A) were formed under the same manufacturing conditions.
And B), the polishing time was changed to polish the photosensitive drum width of about 5 cm per condition. The photoconductor drum used was a film formed under the following conditions.

A washed 120 mmφ x 340 ml cylindrical (surface roughness 0.1S) Al substrate was set in the reaction vessel, baked in vacuum at 100 ° C or higher for 30 minutes, and then evacuated by an oil diffusion pump for 30 minutes to 2 x 10 -Set the vacuum to ⁵ Torr. The oil rotary pump was switched again to allow the reaction gas to flow, and a film was formed with the following layer structure.

Photosensitive layer _{NH 3 / SiH 4 = 0.2%} B 2 H 6 / SiH 4 = 4.0Vppm, a substrate temperature of 315 ° C. 0.99 min deposition (25.mu.) Plasma Power: DC plasma current density: 0.15 mA / cm ² surface layer a-SiOx : HN ₂ O / SiH ₄ = 1.0: Film formation for 5 minutes (up to 1000Å) Plasma current: AC500Hs Plasma current density: 40 μA / cm ² Barium carbonate was used as the polishing agent, and the photoconductor drum was polished by the polishing apparatus shown in FIG. It is loaded into the machine and the rotation speed is 20 rpm, 6 in the figure.
The load of 6 kg was applied to the part of.

The photoreceptor A was polished for 50 minutes and 120 minutes. The other photoreceptor B was polished for 60 minutes, 300 minutes and 480 minutes. After polishing, the photoconductor drum was repeatedly copied many times using a commercially available copying machine (“U-Bix (trade name) 3300MR” manufactured by Konishi Rokusha Co., Ltd.) under normal humidity at 30 ° C. 85% for every 10,000 sheets. Image deletion was evaluated by copying under high relative humidity (relative humidity).

As a result, the non-polished portion of the photoconductor A caused image deletion after 10,000 sheets, and the 50-minute polishing portion began to cause image deletion after 200,000 sheets.

In the 120-minute polishing section, good image quality was obtained without causing image deletion even when the number of sheets exceeded 500,000.

The unpolished part of the photoconductor B causes image deletion after 10,000 sheets,
The minute polishing section has begun to pass the image flow after passing 240,000 sheets. 30
The parts polished for 0 minutes and 480 minutes did not cause image deletion even when the number of sheets exceeded 1 million, and good image quality was obtained.

The photoconductor drums A and B were cut out, and the surface roughness was measured for a polished part and a non-polished part with a coordinate measuring scanning electron microscope and a cross-section measuring device, respectively. The results are shown in Table 1 below.

<Effects of the Invention> When the a-Si photoreceptor of the present invention is used, electrophotographic copying can be achieved without causing image deletion in a high humidity environment.

[Brief description of drawings]

FIG. 1 shows an example of a polishing apparatus used to obtain the a-Si photosensitive member of the present invention. In the figure, 1 denotes a photosensitive drum, and 4 denotes a container for holding a processing agent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Kamoshita 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd. Research Institute (56) Reference JP-A-60-7433 (JP, A) Kai 60-455 (JP, A) JP 59-146058 (JP, A)

Claims (4)

[Claims] 1. An amorphous silicon electrophotographic photosensitive member having a center line average roughness of 90 Å or less measured by a coordinate measuring scanning electron microscope and a cross-section measuring device. 2. The average value of 10 points of the variance R _δ of the center line average roughness of the surface is 110 Å or less.
2. An amorphous silicon electrophotographic photosensitive member according to the item. 3. The amorphous silicon electron according to claim 1, wherein an arbitrary 10-point average value of the maximum amplitude R (t) of the surface measured by the coordinate measuring scanning electron microscope and the cross-section measuring device is 500 Å or less. Photoreceptor. 4. An average value of 5 maximum values and an average value of 5 minimum values of the coordinates of peak points (maximum points and minimum points) in the height direction measured by the coordinate measuring scanning electron microscope and the cross-section measuring device. The amorphous silicon electrophotographic photosensitive member according to claim 1, wherein the average value of any 10 points of the difference R _Z is 450 Å or less.