JPH0241742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and more particularly to a high-sensitivity electrophotographic photoreceptor using a lamination of amorphous silicon hydride and microcrystalline silicon hydride.

Conventionally, electrophotographic photoreceptors have been made by forming a layer of selenium, selenium-tellurium alloy, zinc oxide, or an organic photoconductor on a conductive substrate, or by laminating a layer of cadmium sulfide or a transparent insulating layer on the substrate. It has been put into practical use. However, each of the above-mentioned photoreceptors had the following drawbacks and was not satisfactory. Selenium and cadmium sulfide are toxic and pose problems in terms of pollution, organic photoconductors do not have sufficient mechanical strength and are easily damaged during handling, and zinc oxide has an extremely short service life. There were flaws.

Amorphous silicon used in the present invention has been applied to solar cells, but in recent years it has also been applied to electrophotographic photoreceptors.

Conventionally, the dark resistance of amorphous silicon was 2 to 3 orders of magnitude lower than that of selenium, zinc oxide, or organic photoconductors, and it had problems with its charge retention properties, which are an essential condition for electrophotographic photoreceptors, making it unsuitable for practical use. . In recent years, amorphous hydrogenated silicon has been developed and has begun to be put to practical use in electrophotographic photoreceptors, but there are still issues in its development. For example, an amorphous hydrogenated silicon layer typically
It is manufactured by decomposing silane gas (SiH ₄ ) using a high-frequency glow discharge method and depositing it on a conductive substrate, but the formation rate of the amorphous hydrogenated silicon layer is extremely slow at approximately 4 Å/sec.
Therefore, it takes several hours to manufacture one practical photoreceptor drum. The manufacturing efficiency is thus low, making it unsuitable for mass production.

Furthermore, the photosensitivity of long-wavelength photoreceptors compatible with semiconductor laser light sources is required up to around 850 nm, but amorphous hydrogenated silicon has the disadvantage that it does not have sufficient sensitivity in this long wavelength region due to its light absorption coefficient. ing.

The inventors of the present invention believe that it is difficult to overcome the above drawbacks with a photoreceptor in which only an amorphous silicon hydride layer is used as a photoconductive layer, and have conducted research with the intention of eliminating the drawbacks while taking advantage of the advantages of amorphous silicon hydrides. As a result, the present invention was completed.

That is, an object of the present invention is to develop a new photosensitive layer to replace the conventional electrophotographic photoreceptor, which has strong mechanical strength and excellent wear resistance, is safe, does not cause any pollution, and is made of amorphous amorphous material. It is an object of the present invention to provide an electrophotographic photoreceptor that can be manufactured at a higher manufacturing speed than a photoreceptor having only silicon hydride as a photoconductive layer and has high sensitivity up to a long wavelength region.

The present invention is an electrophotographic photoreceptor comprising an amorphous hydrogenated silicon layer and a microcrystalline hydrogenated silicon layer stacked on a conductive substrate.

The present invention increases manufacturing speed by replacing part of the amorphous hydrogenated silicon layer with a microcrystalline hydrogenated silicon layer, and compensates for long wavelength sensitivity with the wide optical absorption coefficient (up to around 1100 nm) of the microcrystalline hydrogenated silicon. It is something.

The amorphous hydrogenated silicon layer is formed, for example, by a high-frequency glow discharge decomposition method using silane gas (SiH ₄ ) in a hydrogen stream. At this time, under manufacturing conditions such as substrate temperature of 200 to 300°C, gas pressure of 0.01 to 2 Torr, and silane gas flow rate of 0.1 to 100 c.c./min, a high frequency voltage of 0.1 to 30 MHz is usually applied to decompose the gas. Form a film. The amount of hydrogen contained in the amorphous hydrogenated silicon layer is 15 to 30 atomic
% is desirable. Within this range, the dark resistance and dark-light resistance ratio are balanced, resulting in even better photoconductivity. The film thickness is set appropriately, but in most cases it is 3.
A range of 30μ to 30μ is desirable.

On the other hand, a microcrystalline hydrogenated silicon layer can be easily formed by a reactive sputtering method or a vacuum evaporation method.
For example, in the reactive sputtering method, a film can be formed on a substrate at room temperature by using high frequency sputtering (13.56MHz) in a hydrogen stream using silicon as a target.The film thickness is 0.1
The thickness is preferably in the range of 10 μm to 10 μm, and is preferably thinner than the amorphous hydrogenated silicon layer. This is because amorphous silicon hydride has a higher dark resistance than microcrystalline silicon hydride, so it is intended to have a charge retention ability.

Further, the microcrystalline hydrogenated silicon layer can also be formed by a high frequency glow discharge decomposition method as in the case of the amorphous hydrogenated silicon layer. In that case, the temperature of the support is higher than when forming an amorphous silicon layer, specifically 300 to 350
℃, preferably 320℃ to 350℃, and high frequency power
It may be 0.5 to 5 W/cm ² , preferably 1 to 3 W/cm ² . Furthermore, the gas pressure is 0.01~10torr, preferably
The flow rate may be 0.02 to 0.2 torr and 100 to 1000 c.c./min. In this way, by increasing the supporting substrate temperature and increasing the power, the raw material gas (silane, etc.)
It is also possible to increase the flow rate of , and as a result, the film formation rate can be significantly increased. In this way, a layer of microcrystalline hydrogenated silicon is deposited for approximately 20~
Although the film can be formed at a high speed of 100 Å/sec, no deterioration in photoconductive properties is observed even with this increase in film formation speed, and an excellent photoconductive layer can be obtained.

The hydrogen content of microcrystalline hydrogenated silicon is 15~
30 atomic% is preferred. (Reason) Hydrogen content
If it is less than 15 atomic %, the number of voids in the microcrystalline hydrogenated silicon layer will increase and the dark resistance will be low, while if it exceeds 30 atomic %, there will be disadvantages such as not being able to obtain the desired photosensitivity.

The microcrystalline hydrogenated silicon used in the present invention is
It is not an amorphous material with no X-ray diffraction peak; it has an X-ray diffraction peak at a position of 27 degrees, and it is not a polycrystal, which is commonly referred to as having a dark resistance of 10 ⁶ Ω・cm or less. It is characterized by having a dark resistance of 10 ¹¹ Ω·cm or more. Therefore, from this fact, although there is crystallinity, the crystal grain size is unmeasurable, that is, a few
It can be said that it is a collection of fine crystals of 10 Å.

In the electrophotographic photoreceptor of the present invention, the amorphous hydrogenated silicon layer and the microcrystalline hydrogenated silicon layer may be stacked in either order, but from the viewpoint of photosensitivity and electrostatic charge retention, the microcrystalline hydrogenated silicon layer is preferred. A configuration that is an upper layer is preferable.

The conductive substrate used in the present invention is not particularly limited, but stainless steel, aluminum, or glass coated with an ITO film can be used, and its shape can be sheet, sheet, etc.
Drum or belt can be selected as desired.

As described above, the present invention makes it possible to fabricate a long-wavelength photoreceptor that can be manufactured quickly and is also sensitive to semiconductor lasers using an amorphous hydrogenated silicon material.

Next, the present invention will be explained with reference to examples.

Example 1 An aluminum substrate with a diameter of 50 mm and a thickness of 1 mm was placed on a heating holder in a deposition apparatus. The pressure inside the deposition tank was once reduced to 2×10 ^-7 Torr using a vacuum evacuation device, and then silane (SiH ₄ )/hydrogen mixed gas (silane content 15 Vol.
%) was held at 0.4Torr. The temperature of the aluminum substrate is raised to 200℃, and a high frequency of 13.56MHz is generated.
A glow discharge was generated by applying 50 W to form an amorphous hydrogenated silicon layer on the aluminum substrate. The film formation rate at this time was about 7 Å/sec,
An amorphous hydrogenated silicon layer with a thickness of about 12μ was obtained.

Next, the aluminum substrate was slowly cooled and left at room temperature, and the silane/hydrogen mixed gas flow rate was increased five times to 100 c.c./min.

In addition, the high-frequency glow discharge power was increased to 100 W to cause glow discharge again, and the substrate temperature was set to 320° C. to form a microcrystalline hydrogenated silicon layer on the amorphous hydrogenated silicon layer. The film formation rate in this case was about 30 Å/sec, and a microcrystalline hydrogenated silicon layer with a thickness of about 3 μm was laminated to produce an electrophotographic photoreceptor. The microcrystalline hydrogenated silicon film was confirmed by the presence of an X-ray diffraction peak and by measurement of dark resistance of 10 ¹¹ Ω·cm or more.

The photoreceptor was subjected to corona discharge at minus 6.0 KV for 10 seconds to be negatively charged, then left in a dark place for 5 seconds, and the surface potential at that time was measured. Next, it was exposed to 850 nm light made monochromatic by an interference filter from a 300 W xenon light source, and the time T1/2 until the surface potential was halved was determined. The result is
For the electrophotographic photoreceptor of the present invention, T1/2=
7.0sec, whereas for the amorphous hydrogenated silicon single layer photoreceptor prepared for comparison, T1/2=
It was a very large value of 15.0sec.

Example 2 Glass plate 100 coated with ITO film as a transparent electrode
x100 x 1 (mm) was placed on the cathode of a reactive sputtering device. On the other hand, after fixing 5 nines of silicon crystals to the target electrode, the tank was evacuated and the pressure inside the deposition tank was reduced to 8×10 ^-7 Torr. Mixed gas of hydrogen and argon (hydrogen content,
20Vol%) was used, and the gas pressure was adjusted to 2×10 ⁻² Torr. The glass substrate temperature is heated and maintained at 300℃.
Sputtering was performed by applying a high frequency of 13.56MHz. The deposition rate was extremely fast at 100 Å/sec, and a microcrystalline hydrogenated silicon layer with a thickness of 5 μm was obtained.
The microcrystalline hydrogenated silicon film was confirmed by the presence of an X-ray diffraction peak and by measurement of dark resistance of 10 ¹¹ Ω·cm or more. The application of the high frequency voltage was temporarily stopped, the glass substrate temperature was raised to 200°C, and sputtering was performed again. At this time, the mixed gas flow rate was halved and the deposition rate was set to 8 Å/sec to form an amorphous hydrogenated silicon layer on the microcrystalline hydrogenated silicon layer. The thickness of the amorphous hydrogenated silicon layer was 15 μm.

When the electrophotographic photoreceptor was subjected to a corona discharge of +6.0 KV and exposed to monochromatic light of 850 nm from the transparent electrode side as in Example 1, a high photosensitivity of T1/2 = 6.0 sec was observed.

As described above in detail, the present invention is not only capable of increasing the manufacturing speed of an electrophotographic photoreceptor by laminating an amorphous silicon hydride layer and a microcrystalline silicon hydride layer, but also a single layer of amorphous silicon hydride. Even in the long wavelength region (850 nm), where photosensitivity is poor, we were able to obtain a remarkable sensitizing effect.

Claims (1)

[Claims] 1 Laminated on a conductive substrate are an amorphous hydrogenated silicon layer and a microcrystalline hydrogenated silicon layer that has a crystal diffraction peak determined by X-ray diffraction and has a dark resistance of 10 ¹¹ Ω cm or more. An electrophotographic photoreceptor characterized by: