JPS63165857A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a high-contrast image by incorporating group IIIa elements within a specified range in a photoconductive layer made of a-SiGeC installed in an electrophotographic sensitive body. CONSTITUTION:The photosensitive body is obtained by successively laminating on the conductive substrate 1 a first layer 5, the photoconductive a-SiGeC layer 6, and a second layer 7, and this layer 6 has a Ge/Si atomic ratio of 1:2-1:100, and a C/Si atomic ratio of 1:1-1:100, and the layer 6 contains group IIIs elements in an amount of 1-1,000ppm, thus permitting photosensitivity to be enhanced and residual potential to be lowered, and interference fringes to be prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor having a photoconductive amorphous silicon germanium carbide layer, and specifically relates to an electrophotographic photoreceptor having a photoconductive amorphous silicon germanium carbide layer. The present invention relates to an electrophotographic photoreceptor with improved photoconductivity.

[Prior art and its problems]

In recent years, progress in electrophotographic photoreceptors has been remarkable, and the development of ultra-high-speed copying machines and laser beam printers is actively underway.The photoreceptors used in these devices are used at high speeds for long periods of time, so their operation is slow. Stability and durability are required. In response to this demand, hydrogenated amorphous silicon is attracting attention because it has excellent heat resistance, wear resistance, non-pollution properties, and photosensitivity characteristics.

Such amorphous silicon (hereinafter abbreviated as a-Si)
As an electrophotographic photoreceptor, a laminated type photoreceptor as shown in FIG. 2 has been proposed.

That is, according to FIG. 2, a conductive substrate such as aluminum (
1) A-3T carrier injection blocking layer (2) on top, a-S
A carrier generation layer (3) and a surface protection layer (4) are sequentially laminated, and this carrier injection blocking layer (2) is formed on the substrate (1).
) is formed to increase the surface potential by blocking the injection of carriers from the surface (4), and a highly hard material is used for the surface protective layer (4) to increase the durability of the photoreceptor.

On the other hand, germanium element (
A photoreceptor has also been proposed that contains Ge) to increase the photosensitivity in the wavelength range of 600 to 850 nm, thereby making it suitable for semiconductor laser beam printers.

However, with the latter i-photon, the photosensitivity peak shifts to the longer wavelength side, but on the other hand, the carrier generation layer (
The problem of 3) is that the dark conductivity increases rapidly, which lowers the surface potential, and as a result, it becomes difficult to obtain a high-density image.

In order to solve this problem, a photoconductive layer was developed in which carbon was contained in the amorphous silicon germanium layer, and hydrogen and fluorine were also constituent elements.
It is proposed in the above publication, and it is stated that with such a photoconductive layer, the dark resistivity can be set to 10'2 Ω·cm or more.

However, when such an amorphous silicon germanium carbide layer (hereinafter amorphous silicon germanium carbide is abbreviated as a-3iGeC) is formed as a photoconductive layer, the dark conductivity is 10-" (Ω・c
m) can be set to a low value below -', but on the other hand, the bright conductivity also tends to decrease, which causes the bright conductivity (hereinafter abbreviated as σph) to dark conductivity (hereinafter abbreviated as σd). As a result, the light sensitivity is reduced and the image does not have good contrast.
Furthermore, there is a problem in that the residual potential becomes large and fogging tends to occur on the image.

[Purpose of the invention]

In view of the above circumstances, the present inventors have conducted extensive research, and as a result,
When the a-SiGeC layer contains elements of Group Ma of the periodic table within a predetermined range, σd decreases and σph increases.
We found that it is possible to increase the

Therefore, the present invention was completed based on the above findings, and its purpose is to increase σph/σd, thereby
It is an object of the present invention to provide an electrophotographic photoreceptor that has increased photosensitivity and reduced residual potential, thereby producing fog-free and high-contrast images.

[Means for solving problems]

The present invention is an electrophotographic photoreceptor comprising a photoconductive a-SiGeC layer, in which the atomic composition ratio of germanium and silicon is within the range of 1:2 to 1:100, and the atomic composition of carbon and silicon is within the range of 1:2 to 1:100. The layer is characterized in that the ratio is in the range of 1=1 to 1:100, and the layer contains 1 to 11,000 pp of the Group IIIa element of the periodic table.

The present invention will be explained in detail below.

In the electrophotographic photoreceptor of the present invention, the photoconductive a-5iGeC layer contains an element of group 1 of the periodic table (hereinafter abbreviated as Iota group element) within a predetermined range, whereby σph/
It is characterized by increasing σd.

That is, according to the photoconductive a-3iGeC layer according to the present invention,
If the content of the Ma group element is less than 1 ppm, σph/σd becomes small and the photosensitivity decreases, resulting in a decrease in image contrast.
When it exceeds 000pp, σd increases and σ
ph/σd becomes small, which deteriorates the electrophotographic properties.

The ma group elements include B, A1. There are Ga, In, etc., but B is particularly desirable because it has excellent covalent bonding properties and can sensitively change semiconductor characteristics.

Furthermore, according to this a-SiGeCJg, St, Ge, and C
It is necessary to set the composition ratio of each element within the following range.

The atomic composition ratio of Ge and Si is 1:2 to 1:10.
It is preferable to set the ratio within the range of 0, preferably within the range of 1:3 to 1:30, and within this range, the absorption rate for long wavelength light increases and the photosensitivity can be increased.

The atomic composition ratio of C and St is l;1 to 1:100.
It is preferable to set the ratio within the range of 1:3 to 1:100, and within this range, σd can be sufficiently reduced to improve the charging ability.

Hydrogen element (H) is included as an element for terminating dangling bonds so that this a-3iGeC layer has photoconductivity.
and halogen elements, and the content of these elements is 5 to 50 atom%, preferably 5 to 40 atom%, most preferably 10 atom%.
The content is preferably from 30 atomic %, and 11 elements are usually used.

Since this H element is easily taken into the terminal portion, the localized level density in the band gap is reduced, thereby providing excellent semiconductor characteristics.

Further, a part of this H may be replaced with a halogen element,
This makes it possible to lower the localized level density and improve photoconductivity and heat resistance (temperature characteristics). This halogen element includes F, CI, Br, I+At, etc., but F is particularly desirable because its large electronegativity increases the bonding between atoms, resulting in excellent thermal stability. .

According to the present invention, there is provided an electrophotographic photoreceptor including a photoconductive a-SiGeC layer with a large σph/σd.

Therefore, when manufacturing such an electrophotographic photoreceptor, various laminated structures will be described with reference to FIGS. 1 and 3.

According to FIG. 1, a first layer (5) is formed on a conductive substrate (1).
, photoconductive a-3iGeC layer (6) and second layer (7)
It is a photoreceptor in which layers are sequentially laminated, and the first layer (5) is a-5.
It has the function of transporting carriers generated in the iGeC layer (6) and retaining charges, and also carries a-
It has the function of preventing carriers from being injected into SiGeCII (6).

Such a first layer (5) includes, for example, a-5i, a
There are inorganic semiconductors such as -SiC, a-SiO, and a-5iN.

When forming this first N(5) from a semiconductor material, its conductivity type is controlled to P type when the photoreceptor is charged to positive polarity, and controlled to N type when charged to negative polarity. This further improves the carrier injection blocking effect. For example, this P-type semiconductor material has B
For the N-type semiconductor material, 50 to 10. OOOppm
There is a-3i or a-5iC contained within the range of .

On the other hand, the second layer (7) is formed to prevent the electrophotographic characteristics from deteriorating due to various external physical or chemical influences on the photoreceptor, and is generally highly insulating, The film is formed using a material that has high corrosion resistance, high hardness, and has a surface protection effect. Such materials include, for example, organic materials such as polyimide resin, SiO
□+ S s O+ A 120 :l 1SiC,S
There are inorganic materials such as i, N, + a-3i, and a-5iC.

Regarding the laminated type photoreceptor, there are various types of laminated type photoreceptors other than the photoreceptor shown in Fig. 1. For example, as shown in Fig. 3,
A laminated type photoreceptor may be used in which the second layer (7) is excluded from the photoreceptor shown in the figure.

In such a photoreceptor, since the a-SiGeC layer (6) is the surface layer of the photoreceptor, it has excellent charging ability and environmental resistance by itself, and is a surface protective layer made of non-photoconductive a-SiC. As a result, even if the surface is repeatedly polished and regenerated with an abrasive or the like, the initial characteristics of the photoreceptor can be maintained without being limited in the amount of polishing. For example, even if the surface deteriorates due to exposure to corona discharge or filming on the surface of the photoreceptor due to the resin component of the developer, good images can be stably supplied over a long period of time by this polishing regeneration.

Further, according to the laminated photoreceptor according to the present invention, the a-SiGeC layer (6) is formed in the lamination order shown in FIG. 1 or FIG.
When this layer (6) is formed, this layer (6) can be effectively used as a light carrier generation layer in the photoreceptor, and as a result, incident light does not reach the substrate (1), and as a result, image interference occurs. The problem of stripes is resolved.

In other words, since the light source of the photoreceptor installed in a semiconductor laser beam printer is coherent light, interference fringes are likely to occur in the image.The cause of this is that the coherent light reaches the substrate and the substrate This is because reflected light and incident light interfere with each other. To solve this problem, it has been proposed to treat the surface of the substrate to a desired surface roughness, thereby causing the light that reaches the substrate to be diffusely reflected. ing.

On the other hand, if the a-3iGeC layer (6) is a layered photoreceptor in which the layer is substantially a photocarrier generating layer, the substrate (1)
The incident light does not reach this point, and therefore no interference fringes occur in the image.

In the case of such an a-SiGeC layer (6), the thickness of the layer can be appropriately determined so that this layer can substantially serve as a photocarrier generation layer, but the inventors have determined the thickness in several ways. As a result of experimenting with different layers, we found that this a-SiGeC layer (
If the thickness of the substrate (6) is set so that the transmittance to the incident light is 30% or less, preferably 20% or less, the substrate (
The transmittance of this layer (6), which serves to prevent light from reaching 1) at all, can be reduced as its thickness is increased, but on the other hand, the residual potential of this photoreceptor tends to increase. Therefore, the thickness of the a-3iGeC layer (6) is determined by the transmittance and residual potential of that layer.
According to experiments repeatedly conducted by the inventors, 1 to 10
0μm, preferably l to 30μm, optimally l to 5μm
It was found that it is sufficient to set it within the range of -.

Further, according to the present invention, the first layer (5) and the a-SiGeC
(6) Bonding ri! which improves electrophotographic properties by bonding both layers at the interface! (The thickness of this layer is preferably 3 μm or less) may be interposed in this bonding layer.

For example, after forming the first layer (5) as a thin film with an a-5i layer, carbon (C) and/or germanium (Ge)
The content of each is gradually increased in the layer thickness direction, and when the formation of the bonding layer is completed, the content of each is increased to a-
There is a layer of SiGe (layer (6)) that is set to match the required amount of C and Ge.

Further, according to the present invention, the carbon (C) content and germanium (Ge) content of the a-5iGeC layer (6) are varied in the layer thickness direction, thereby making it possible to obtain photoreceptors with various embodiments. I discovered that.

That is, according to FIGS. 4 to 11, the horizontal axis represents a-SiG
The layer thickness from the interface (a) with the a-3i layer of the eC layer (6) to the opposite surface (b) is shown, and the vertical axis represents the C content and Ge content. The contents are also relative amounts. In addition, in these figures, a solid line and a broken line indicate C content and Ge content, respectively.

As is clear from these figures, a-SiGeCN (6
), the Ge content is relatively low or the C content is relatively high in the Ji% 1 region near the b side on the incident light side, thereby increasing the band in the layer region on the incident light side. The gap becomes larger and there is higher photoconductivity, and as a result, incident light is photoelectrically converted with high efficiency and photosensitivity can be increased.

On the other hand, in the layer region close to the a-plane, the Ge content is relatively high or the C content is relatively low. Light is completely absorbed within this layer area.

Therefore, by forming both of the layer regions as described above, it is possible to obtain an electrophotographic photoreceptor having high photosensitivity characteristics and further suppressing the generation of interference fringes.

Next, a method for manufacturing the electrophotographic photoreceptor of the present invention will be described.

a-3iGeC11(6), the first M(5) and the second
For the layer (7), a thin film forming method such as glow discharge decomposition method, ion blating method, reactive sputtering method, vacuum evaporation method, thermal CVD method, etc. can be used, and the raw materials used for this can include solids, It can be either liquid or gas.

In addition, when forming layers other than the a-5iGeC layer (6), it is preferable that these layers be formed of a-St or a-3iC because similar thin film forming means can be used. Furthermore, when the same film forming apparatus is used, there is an advantage that the thin film can be continuously laminated by a common thin film forming means.

For example, using a glow discharge decomposition device, a-5i layer, a-S
When producing a photoreceptor consisting of an iC layer or an a-5iGeC layer, SiH4, Si! I(a+
5i31 (Si-based gas such as s, CHゎCxHg, Ct
C-based gases such as Hi, CtHi, C+Hs, GeH*+
There is a Ge-based gas such as GexHi, and He gas, 3, gas, etc. may be used as a carrier gas.

According to this glow discharge decomposition method, when an a-SiC layer or an a-5iGeC layer is formed using a mixed gas in which acetylene (cant) gas is added to a Si-based gas and/or Ge-based gas, the speed is significantly higher. It is desirable in that it can achieve good film formability.

Next, the electrophotographic photoreceptor described in the embodiments of the present invention was processed into B-5i, a-SiC, or a-
In the case of forming 3iGeC, the manufacturing method will be explained using a capacitively coupled glow/discharge decomposition device shown in FIG.

In the figure, tanks (8) (9) (10) (11) (
12) (13) has 5iHa and GeH*+C, respectively.
tHt+BzHi (contains 0.2χ with Ht gas dilution).

H! , NO gas is sealed, and H2 is also used as a carrier gas. These gases are connected to the corresponding regulating valves (14) (15) (16) (17) (1B)
(19) is released by opening the mass flow controller (20) (21) (22).
(23) (24) (25), gas from tanks (8) (9) (10) (11) (12) goes to main pipe (26), and NO gas from tank (13) goes to main pipe (26). 27). Furthermore, (28) (29)
is a stop valve. The gas flowing through the main pipes (26) and (27) is sent into the reaction tube (30), and a capacitively coupled discharge electrode (31) is installed inside this reaction tube (30), and the gas is applied to it. The high frequency power is 50-
to 3) [w, and the frequency is IMHz to 50MH
z is appropriate. Inside the reaction tube (30), a cylindrical film-forming substrate (32) made of aluminum is mounted on a sample holding stand (30).
3), and this holding stand (33) is rotatably driven by a motor (34).
Then, the substrate (32) is heated to about 200 mL by suitable heating means.
It is heated uniformly to a temperature of from 400°C to 400°C, preferably from about 200 to 350°C. Furthermore, inside the reaction tube (30) there is a
- High vacuum state B for SiC film formation (gas pressure during discharge 0.
1 to 2.0 Torr) and is connected to a rotary pump (35) and a diffusion pump (36).

In the glow discharge decomposition device configured as above,
For example, a substrate (32
), the regulating valves (14) (15) (
16) (17) Open (1B) and add SiH4,
GeHa, CzHz, BgHi+H8 gases are released.

The amount of release is determined by the mass flow controller (20) (21)
(22), (23), and (24), these mixed gases are flowed into the reaction tube (30) via the main pipe (26). Then, the inside of the reaction tube (30) is 0.1
A vacuum state of about 2.0 Torr and a substrate temperature of 200
to 400°C, the high frequency power of the capacitively coupled discharge electrode (31) is 50 to 3 KW, and the frequency is 1 to 50 MH2
Coupled with this setting, glow discharge occurs,
The gas is decomposed and an a-SiGeC film containing B element is formed on the substrate at high speed.

〔Example〕

Next, examples of the present invention will be described.

(Example 1) In the present invention, a-3i of a single composition is used throughout the layer thickness direction.
A GeC film was formed, and the spectral sensitivity characteristics were measured for cases in which the element boron (B) was contained or not contained.

That is, a 3 x 3 cm square aluminum flat plate was prepared, and the aluminum cylindrical substrate (32) shown in Fig. 12 was prepared.
A part of the circumferential surface of the tank is cut out, and this flat plate is installed in the cutout, and SiH and gas are supplied from the tank (8), and Ge1. Ctf gas from tank (10)! It gas, H gas from the tank (12), and further BAH gas from the tank (11) as needed at the gas flow rate shown in Table 1, and 5 μm of it was deposited on the above flat plate by glow discharge decomposition method.
Samples A and B were manufactured in which an a-SiGeC film with a thickness of - was formed. In producing both samples, the gas pressure was set to 0.45↑orr, the high frequency power was set to 150 -, and the substrate temperature was set to 300°C.

Table 1 When the composition ratios of the elements of Samples A and B thus obtained were measured using an X-ray microanalyzer and a secondary ion mass spectrometer, the results shown in Table 2 were obtained.

Table 2 In addition, when the spectral sensitivity characteristics of samples A and B were measured using the comb electrode method, the results shown in Figure 13 were obtained. In Figure 0, the horizontal axis is the emission wavelength of the light source, and the vertical axis is the conductivity, and the exposure amount was set at 50 μ-/c-2 in both measurements. The * and ○ marks are the plots of the sample ASB, and the curves a and b are the respective characteristic curves.

As is clear from this result, it can be seen that the conductivity of sample B is approximately one order of magnitude higher than that of sample A.

In addition, when measuring the dark conductivity of each sample, sample A was 2. I
was 1.7 Xl0-+3 (Ω·cm)-', and the dark conductivity of sample B was about one order of magnitude smaller than that of sample A.

(Example 2) Next, when manufacturing sample B of (Example 1), B, H,
Various samples were fabricated by changing the gas flow rate and other fabrication conditions, and their σph and σd were measured, and the results shown in FIG. 14 were obtained.

In the figure, O mark and ・ mark are σph and σd, respectively.
C and d are respective characteristic curves.

As is clear from this figure, the B content ranges from 1 to 1000.
It can be seen that within the range of ppn+, the ratio of σph/σd becomes significantly large, and in particular, when the B content is between 5 and 500 ppm, the ratio becomes significantly large.

(Example 3) In this example, the substrate (32) was prepared using the glow discharge decomposition apparatus shown in FIG.
A first layer (5), an a-5iGeC layer (6), and a second layer (7) were sequentially formed thereon to produce an electrophotographic photosensitive drum. Note that during the formation of the first layer (5), NO gas is introduced to dope oxygen and nitrogen to improve adhesion to the substrate.

[Margin below]

When the surface potential, photosensitivity and residual potential of the photosensitive drum thus obtained were measured, the following results were obtained. This result was obtained by charging in a +5.6 KV corona charge and then projecting a laser beam with an emission wavelength of 780 n-.

Surface potential...+850v Photosensitivity (half exposure)...1.40μJ/cm"Residual potential...30V This drum is connected to a semiconductor laser beam printer (wavelength 7
When installed and printed at a printing speed of 40 sheets/min (B0nm, printing speed: 40 sheets/min), high-quality images were obtained with high image density, high contrast, and no ghost phenomenon, and also no interference fringes or capri. .

(Example 4) In this example, when manufacturing the electrophotographic photoreceptor of (Example 3), mass flow controllers (20) (21) (22) were used to form the a-3iGeC layer (6).
(24), thereby 5iH1 gas, Ge
Hh gas, C! By varying the flow rates of Ht gas and H8 gas, eight types of photoreceptors (photoreceptors A to H) with different atomic composition ratios of %S1, Ge, and C were manufactured. Image evaluation was performed.

The results are shown in Table 4. According to the image evaluation in the table, each photoreceptor drum was mounted on a semiconductor laser beam printer (wavelength 780n1, printing speed 40 sheets/min) and printed. The images obtained were classified into three types: ◎, ○, and X.

In other words, the mark ◎ indicates that the image density is high, the contrast is high, there is no ghost phenomenon, and the image has no interference fringes or fog, and the mark ○ is the case that the image has high density, excellent contrast, and , when there are almost no image interference fringes, the fog is extremely small, and a high-quality image is obtained without causing any practical problems. This is a case where the fog has become noticeable due to a decrease in the brightness.

[Margin below]

As is clear from Table 4, photoconductors C to F had excellent image density and contrast, and good images were obtained without ghost phenomena, interference fringes, or fog. Photoconductor E was particularly evaluated for image evaluation. The top was also excellent.

However, photoconductors A and H have the same Ge/St ratio as photoconductor B.

In G, the C/Si ratio was outside the range of the present invention, and interference fringes and fog occurred in the image.

〔Effect of the invention〕

As described above, according to the electrophotographic photoreceptor of the present invention, the photoconductive a-5iGeC layer contains the Ma group element within a predetermined range, thereby increasing σph/σd. , it was possible to increase the photosensitivity and reduce the residual potential.

Further, according to the electrophotographic photoreceptor of the present invention, a-SiGeC
The layer can be a carrier generation layer for long wavelength light, making the photoreceptor suitable for semiconductor laser beam printers. Furthermore, according to this photoreceptor, since the incident light does not reach the substrate, interference fringes do not occur in the image, and there is no need to roughen the surface of the substrate to increase its surface roughness. A low-cost electrophotographic photoreceptor is provided.

Furthermore, according to the electrophotographic photoreceptor of the present invention, the surface layer is a-S.
It is also possible to use a photoconductor with an iGeC layer, and when such a photoconductor is used, a clear image without fog can be obtained with a high black background density. Even if this process is repeated, the characteristics do not deteriorate in terms of the amount of polishing, and thus the initial characteristics of the photoreceptor can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the laminated structure of an electrophotographic photoreceptor according to the present invention, FIG. 2 is a cross-sectional view showing the layer structure of a conventional general amorphous silicon photoreceptor, and FIG. 4, 5, 6, 7, 8, 9, 10, and 11 are cross-sectional views showing other laminated structures of electrophotographic photoreceptors according to the present invention. Diagram 1 showing the carbon content and germanium content in the layer thickness direction of the amorphous silicon germanium carbide layer of the electrophotographic photoreceptor.
Fig. 2 is a schematic diagram of a capacitively coupled glow discharge decomposition device used in an embodiment of the present invention, Fig. 13 is a diagram showing a spectral sensitivity curve of an amorphous silicon germanium carbide layer, and Fig. 14 is a diagram showing a spectral sensitivity curve of an amorphous silicon germanium carbide layer. FIG. 2 is a diagram showing drawing conductivity and dark conductivity. l... Conductive substrate 5... First layer 6... Amorphous silicon germanium carbide layer 7... Second layer Patent applicant (663) Kyocera Corporation
Takao dirt material

Claims (1)

[Claims] An electrophotographic photoreceptor comprising a photoconductive amorphous silicon germanium carbide layer, the layer having an atomic composition ratio of germanium and silicon of 1:2 to 1:100.
and the atomic composition ratio of carbon and silicon is 1:
1 to 1:100, and the layer is in the range of 1 to 100
An electrophotographic photoreceptor comprising 0 ppm of Group IIIa elements of the periodic table.