JPH0210368A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a film to be used for a photosensitive body having low dark conductivity and high photosensitivity at even a high film-forming velocity by forming a photoactive area by the decomposition of a radically polymerizable Si compd. having unsatd. bonds in a molecule by the effect of electric discharge. CONSTITUTION:In an electrophotographic sensitive body having a photoactive area and a carrier transfer area, said photoactive area is formed by the decomposition of a radically polymerizable Si compd. having unsatd. bonds in a molecule by the effect of electric discharge. The Si compd. is a specified silane compd., pref., for example, Si compds. such as vinyl silane, divinyl silane, trivinyl silane. The plasma decomposition is carried out by the plasma CVD process using glow discharge decomposition, etc. Thus, a film for a photosensitive body having low dark conductivity and high photosensitivity is obtd. at even a high film-forming velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a thin film of amorphous silicon carbide (hereinafter abbreviated as a-5iCx:H) as a photoactive layer. Regarding.

[Background technology]

Amorphous silicon has high frictional strength and has better printing durability than selenium photoreceptors, so it has begun to be put into practical use as electrophotographic photoreceptors for high-speed 4ILAT. However, the electrical resistance value of amorphous silicon is basically not low enough to be used as an electrophotographic photoreceptor.
This point still remains as a problem to be solved.

For this purpose, attempts have been made to mix elements such as carbon, oxygen, and nitrogen. However, mixing of these elements is done by decomposing compounds containing these elements together with silane, but these compounds have different decomposition properties with respect to silane, which is the raw material for silicon, so it is difficult to form a film. The proportion introduced into the thin film varies greatly depending on the conditions, making it difficult to control the composition. Furthermore, the introduction of these elements resulted in the photoelectric properties themselves being lower than that of amorphous silicon. On the other hand, attempts have been made to reduce the electrical conductivity by using organic silanes containing alkyl groups, allyl groups, etc. in the molecule, but in this case, the reduction in photosensitivity is more important than the reduction in electrical conductivity. This is more remarkable, and it is difficult to obtain practical performance as an electrophotographic photoreceptor. This is presumed to be because alkyl groups, allyl groups, etc. are difficult to incorporate into the silicon-silicon bonds constituting the photoreceptor thin film, and silicon-carbon bonds are not effectively formed.

In view of this point, the inventors of the present invention have made extensive studies and found that by using a silicon compound having a radically polymerizable unsaturated bond in the molecule as a raw material for forming a photoreceptor thin film,
The inventors have discovered that the above problems can be solved and have completed the present invention.

[Disclosure of the invention]

That is, the present invention provides an electrophotographic photoreceptor having a photoactive region and a carrier transport region, in which the photoactive region is formed by decomposing a silicon compound having a radically polymerizable unsaturated bond in the molecule by discharging. A photoreceptor for electrophotography, characterized in that the photoactive region is a non-containing photoreceptor formed by decomposing a silicon compound having a radically polymerizable unsaturated bond in the molecule by electric discharge. The gist is an electrophotographic photoreceptor made of a crystalline silicon carbide thin film.

The silicon compound (hereinafter abbreviated as U-silane) having a radically polymerizable unsaturated bond in the molecule used in the present invention has the general formula R11S ia H! ms! -a (However, R is an unsaturated hydrocarbon group having about 2 to 10 carbon atoms that is capable of radical polymerization, m and n are natural numbers. m is 1 or 2, and when m = 1, n = 1.2, 3° or 4, and when m-2, n=1.2.34.5. or 6).

Specific examples of this U-silane include vinylsilane, divinylsilane, trivinylsilane, vinyldisilane, divinyldisilane, trivinyldisilane, 1-propenylsilane, 2-propenylsilane, isopropenylsilane, 1-butenylsilane, -butenylsilane, 2-
Preferred examples include silicon compounds such as pentenylsilane and ethynylsilane.

The plasma decomposition method used in the present invention is as follows:
Any method that can generate various radical species containing silicon during the decomposition reaction can be effectively used. In terms of the R-body, plasma CVD (plasma chemical deposition method) using glow discharge decomposition, microwave CVD or ECRCVD (electron cyclotron resonance chemical deposition method) using microwaves for decomposition, etc. can be used.

In the present invention, the conditions for forming a thin film are not particularly limited and can be determined as appropriate;
Points that can serve as effective guidelines are listed below. First, the inventors have discovered that when U-silane is decomposed alone, a-SiCx with a wide optical bandgap and a high carbon content: HrfJ A membrane can be obtained. Furthermore, by mixing hydrogenated silicon such as monosilane or disilane with U-silane, it is possible to change the carbon content in the a-3iCxJ thin film, and the optical band gap can be changed arbitrarily. can. Furthermore, hydrogen,
Decomposition of U-silane and a mixed gas of U-silane and silicon hydride in a diluted state using a diluent gas such as helium or argon can also be said to be a film forming condition that can be effectively used in the present invention. By using a diluent gas, the stability of the decomposition conditions is improved, and the resulting a-3iC
The reproducibility of the film characteristics of the x:H thin film is improved, which is preferable for practical use. In addition, p-type or n-type semiconductor properties can be imparted by doping with impurities. To impart p-type and n-type properties, boron- or phosphorus-containing compounds such as diborane or phosphine are added to U
- It can be plasma decomposed together with silane. In addition, diborane poles (weight addition, diborane/bisilane-0,0
1-11000pp, more preferably 0.1-110
A major advantage of the present invention is that the photosensitivity of the resulting a-3iCx:H thin film increases significantly at an addition amount of 0 pp, more preferably 1 to sop, making the film more suitable as an electrophotographic photoreceptor. This is one of its characteristics.

The operating factors such as substrate temperature, reaction pressure, raw material gas flow rate, and discharge power employed in the present invention during thin film production are as follows: The optimum conditions differ somewhat depending on the plasma decomposition method used, and may be appropriately determined depending on the decomposition method.

The substrate temperature is from room temperature to about 500°C, preferably from 100°C to about 400°C. The zero reaction pressure, in which the optical bandgap decreases as the substrate temperature rises and the sensitivity to long wavelength light increases, is achieved by plasma CVD (plasma chemical deposition) using glow discharge decomposition or by microwaves using microwaves for decomposition. In the CVD method, the pressure is in the range of about 0.01 torr to 10 torr, preferably 0.02 torr to 2.0 torr.
The range is about Qtorr. Even in the method that uses microwaves for decomposition, in the ECRCVD method that uses electron cyclotron resonance for excitation, even lower pressure conditions are sufficient, and 0. About 01 mtorr to 50 mtorr is sufficient. The raw material gas flow rate and discharge power are appropriately selected depending on the size of the film forming chamber of the film forming apparatus, the size of the substrate, the target carbon content, the film forming rate, etc. Regarding the raw material gas flow rate, for U-silane, a flow rate of about 1 to 1000 sccs is sufficient, and when silicon hydride or diluent gas is used, a flow rate of about 0.1 to 100 times that of U-silane is used.

[Effect]

It is recognized that various silicon-related radical species are formed during plasma decomposition of silicon compounds. This is thought to be because the related radicals and the unsaturated hydrocarbon groups in the U-silane of the present invention can undergo a radical reaction, so fewer hydrocarbon groups remain as pendants. In other words, it is presumed that this is because carbon is incorporated into the silicon network and silicon-carbon bonds are effectively generated.

Therefore, in the case of the decomposition method using U-silane of the present invention, the discharge power may vary depending on the equipment used, but it is usually in the range of about IW to 50W, and the discharge power is usually in the range of about IW to 50W. Compared to hydrogen decomposition,
It can be lowered much further. However, most electrophotographic photoreceptors are made of electrodes and several types of thin film semiconductors, and under formation conditions where the discharge power is high, plasma damage may be caused to the electrodes and semiconductor thin films that have already been formed. , is a well-known fact to those skilled in the art. For this reason, various attempts are being considered to reduce the power required for decomposition, and being able to greatly reduce the discharge power required for film formation provides extremely favorable conditions when forming electrophotographic photoreceptors. This is because it is possible.

Furthermore, another noteworthy effect of the present invention is that the film formation rate does not decrease even under film formation conditions with low discharge power. However, since electrophotographic photoreceptors usually require a fairly thick film of at least 0.1 μm or more, it takes a considerable amount of time to form the film.
The fact that the film formation rate is so high even under low discharge power is because
This is because it is extremely preferable and meaningful in practical terms, that is, when this is implemented on an industrial scale.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example 1] The thin film forming apparatus includes (1) a raw material supplying means having a raw material flow rate control means, (2) a means for generating electric discharge to decompose the raw material, and (2) maintaining a thin film forming atmosphere at a pressure of not more than lot, orr. Vacuum evacuation means for
At least a means for inserting a substrate on which a Cx:H thin film is formed into a thin film forming chamber, ■ a means for holding the substrate, ■ a means for heating the substrate, and ■ a means for measuring formation conditions such as pressure and temperature. A-3iCx:Hf1tll was formed using the apparatus having a thin film forming chamber. Monovinylsilane was used alone as the raw material gas. For optical bandgap measurements, quartz glass was used as the substrate. Furthermore, a silicon single crystal substrate was used for measurement of infrared absorption spectra. Thin film formation temperature is 250
It was set to °C. While monovinylsilane was supplied to the thin film forming chamber at a flow rate of Rosecll, the pressure in the thin film forming chamber was maintained at 0.1 torr by a vacuum evacuation means. The discharge power was IOW. The thin film was formed to a thickness of 1 μm. The film formation rate was 10 persons/second or more, and the optical band gap was 2.7e■ or more. Dark conductivity is 1
x 10-13 S/em or less, and the thin film had performance suitable for use in electrophotographic photoreceptors. Furthermore, it was confirmed from the Akaku line absorption spectrum that there were few pendant alkyl groups.

(Example 2) In Example 1, monovinylsilane,
Disilane was used and hydrogen was used as the diluent gas. Monovinylsilane was supplied at a ratio of 35 ccya, disilane at 7 sec+e, and hydrogen at 59 sec. The pressure in the thin film forming chamber was maintained at 0.5 torr by vacuum evacuation means. The film formation rate was 10 people/second or more, which was clearly higher than the film formation rate of disilane alone, which was 9 people/second. The optical bandgap of the thin film is approximately 2. leV, the photoconductivity was 5 x 10-''S/C1 or more, and the dark conductivity was 1 x 10-1''S/cm or less, demonstrating extremely excellent photoelectric properties. That is,
i! has the ability to be used as is in the photoactive layer of an electrophotographic photoreceptor using an amorphous thin film. It has been certified.

(Example 3) In Example 2, it became clear that the formed thin film had performance that could be used as a photoactive layer of an electrophotographic photoreceptor. I tried.

In Example 2, an aluminum plate was used as the substrate,
In addition to the raw material gas of Example 2, 50 ppm of diborane relative to monovinylsilane was added as a raw material gas to form a thin film. The film thickness was 0.3 μm. With the introduction of diborane, the photoconductivity is 1 x 10-”S/
cva or higher, the dark conductivity is 5 x 10-143
/CI or less, and the photosensitivity was further improved. An organic thin film was formed on this thin film as a carrier transport layer. The organic YI film was formed by dissolving a hydrazone compound in chloroform at a weight ratio of 11 to polycarbonate, and applying the solution by a dip method. The film thickness after drying was 20μ. The material was negatively charged by corona discharge, and the attenuation of the charge due to light irradiation was measured.

The half-life of decay was 0.51 ux-sec and the residual potential was IOV. The results showed that the material exhibited extremely excellent properties as a photoreceptor for electrophotography.

[Comparative Example 1] Instead of monovinylsilane in Example 1, a mixed gas of equal volume of monosilane and methane was used. The photoconductivity of the thin film was 2 x 10-'S/cm or more, but the dark conductivity was 1 x 10-'S/em or more, indicating properties that are not suitable for electrophotographic photoreceptors. Met. The optical bandgap was about 1.8e■, which was about the same as that of amorphous silicon containing no carbon. This is probably because monosilane decomposition mainly occurred because the discharge power was as low as 10 W, and the proportion of methane incorporated into the thin film decreased.

[Comparative Example 2] In Comparative Example 1, since the optical bandgap was small, only the discharge power was changed to 40 W, and the experiment was carried out. By setting the discharge power to 40W, the dark conductivity is 1 x
Although it decreased to about 10-13 S/cta, the photoconductivity also decreased and the photosensitivity decreased. Further, the film forming speed was 3 people/second, which was less than 1/3 of that of the present invention. As described above, it has been difficult to form an a-3iCx:H thin film for electrophotography using conventional techniques.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, U
- By using silane as a raw material and subjecting it to discharge decomposition, a thin film for electrophotographic photoreceptors with low dark conductivity and excellent photosensitivity can be obtained at a high film formation rate. Furthermore, since the discharge power can be much lower than in the past, plasma damage during discharge decomposition can be further reduced. In this way, the U used in the present invention
- It is clear that silane is excellent as a raw material gas for forming electrophotographic photoreceptors and the like.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor having a photoactive region and a carrier transport region, the photoactive region is formed by decomposing a silicon compound having a radically polymerizable unsaturated bond in the molecule by electric discharge. A photoreceptor for electrophotography characterized by the following. (2) Claim 1 in which the photoactive region is made of an amorphous silicon carbide thin film formed by decomposing a silicon compound having radically polymerizable unsaturated bonds in its molecules by electric discharge.
The electrophotographic photoreceptor described above.