JPS635348A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain the titled body having improved dark resistivity and carrier mobility of a carrier transfer layer composed of a-SiC:H by using a-SiC film to every layer comprising a carrier injection preventive layer, the carrier trans fer layer and a carrier generating layer, and by setting up a specific condition to said layers. CONSTITUTION:The titled body is a laminate composed of the carrier injection preventive layer 2a, the carrier transfer layer 5 and the carrier generating layer 3a mounted on a substrate 1. The carrier injection preventive layer 2a is composed of a-SiC, and has a ratio of atomic compositions of C and Si of a range of (1:9)-(9:1). The carrier generating layer 3a is composed of a-SiC, and the carrier transfer layer 5 is composed of a-SiC:H and has the ratio of the atomic compositions of C and Si of the range of (1:9)-(9:1) and has <=1,000 absorption coefficient of 2,860cm<-1>, and >=1,000 absorption coefficient of 2,090cm<-1> at the infra-red absorption spectrum. Thus, the dark resistivity and the carrier mobility of the carrier transfer layer which is composed of a-SiC:H and is formed as a layer of function separation type photosensitive body, may be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor that enables high-speed copying by improving charging ability.

[Prior art and its problems]

,Recently, 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, an a-Si carrier injection blocking layer (2), an a-
A St 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 (
The surface protective layer (4) is formed to prevent injection of carriers from 1) and to lower residual potential, and a highly hard material is used for the surface protective layer (4) to increase the durability of the photoreceptor.

However, according to this a-Si photoconductor, the dark resistivity of the a4i carrier generation layer (3) itself is 101IΩ・
cm or less, which increases the dark decay rate of this photoreceptor and makes it difficult to increase its own charging ability.As a result, when this photoreceptor is used for high-speed copying, it suffers from the optical memory effect. There is a problem in that the previous image remains without being completely removed, and the previous image reappears with the formation of the next image (ghost phenomenon).

In order to solve this problem, a functionally separated type photoconductor as shown in FIG. 1 has been proposed.

That is, according to FIG. 1, the carrier injection blocking layer (
A carrier transport layer (5) is formed between the carrier generating layer (3a) and the carrier transport layer (2a).
5) is made of a material with high dark resistance and high carrier mobility, thereby providing a high-performance photoconductor with excellent surface potential and photosensitivity and low residual potential.

For this carrier transport layer (5), it is recommended to use hydrogenated amorphous silicon carbide, which has high resistance, wide bandgap, and semiconductor properties.
It has been proposed in Publication No. 192046 and the like.

However, when forming a carrier transport layer made of hydrogenated amorphous silicon carbide (hereinafter abbreviated as a-SiC:H) disclosed in this publication, for example, when using a glow discharge decomposition method, the reaction pressure, high frequency power, etc. High quality a-SiC:H with stable characteristics due to various discharge conditions, type of raw material gas, gas flow rate, etc.
It is difficult to form a film, and this film itself tends to generate dangling bonds more easily than a hydrogenated amorphous silicon (hereinafter abbreviated as a-St:H) film. It is difficult to obtain an a-SiC:H film with a dark resistivity of .

Furthermore, in order to form this a-SiC:l{ film under stable conditions with good reproducibility, a detection means that can commonly evaluate the characteristics of both dark resistivity and carrier mobility is desired.

[Purpose of the invention]

Therefore, the present invention was completed in view of the above circumstances, and its purpose is to improve the dark resistivity and carrier mobility of an a-SiC:}l carrier transport layer, thereby producing an electrophotographic material with a large charging ability. The goal is to provide an angry body.

Another object of the present invention is to provide an electrophotographic photoreceptor suitable for high-speed copying.

Still another object of the present invention is to provide an electrophotographic photoreceptor that is easy to set manufacturing conditions for manufacturing an a-SiC:tl carrier transport layer and has excellent reproducibility and stability.

[Means for solving problems]

According to the present invention, there is provided a laminate comprising at least a carrier injection blocking layer, a carrier transport layer, and a carrier generation layer formed on a substrate, the carrier injection blocking layer being a-SiC.
and the atomic composition ratio of C and Si is 1:9 to 9:
1, the carrier generation layer is made of a-SiC, the carrier transport layer is made of a-SiC:H, and the atomic composition ratio of C and Si is in the range of 1:9 to 9:1. Yes and 2860 in the infrared absorption or spectrum
cm-' absorption coefficient is 1000 or less and 20
There is provided an electrophotographic photoreceptor characterized in that the absorption coefficient at 90 cm-' is 1000 or more.

The present invention will be explained in detail below.

As shown in FIG. 1, a typical electrophotographic photoreceptor of the present invention includes a carrier injection blocking layer (2a), a carrier transport layer (5), a carrier generation layer (3a) and a surface protective layer (1) on a substrate (1). There is a laminate in which 4) are sequentially laminated, and a carrier transport layer (5) and a carrier generation ti (3) are added to this laminate.
There is a laminate in which the stacking order of a) is changed.

According to the present invention, an a-SiC film is used for all of the carrier injection blocking layer (2a), the carrier transport layer (5), and the carrier generation layer (3a) used in the functionally separated photoconductor, and these layers It has been discovered that the object of the present invention can be achieved by setting various conditions.

a-SiC used in the carrier transport layer according to the present invention:
The H film is produced, for example, by the glow discharge decomposition method described below, and its dark resistivity and carrier mobility are sensitively affected by the discharge conditions, etc. The present inventors have elucidated the cause of this. As a result of repeatedly conducting various experiments in order to achieve this goal, it was found that the bonding state of C and H and the bonding state of Si and H significantly affect the above-mentioned characteristics.

That is, when the infrared absorption spectrum of the a-SiC:H film is measured, CH2 bonds and cH. An absorption peak indicating the bond stretching mode appears at a wave number of 2860 cm-', and SiH
It was confirmed that an absorption peak indicating the stretching mode of bonds and SiH2 bonds appears at a wave number of 2090 cm-', and the absorption coefficient at 2860 cm-' is 1000 or less, and the absorption coefficient at 2090 cm-' is 1000.
As mentioned above, the absorption coefficient at 2860 cm-' is preferably 500 or less, and the absorption coefficient at 2090 cm-' is preferably 100.
It was found that when the value is 0 or more, the number of dangling bonds decreases, resulting in a large carrier mobility.

According to the present invention, the atomic composition ratio of Si and C in this a-SiC:H film is important, and this ratio is 1:9 to 9:1,
It has been found that when the ratio is suitably set within the range of 2:8 to 8:2, the dark resistivity becomes 1011 Ω·cm or more.

Further, the hydrogen content in the film is related to the Si--C atomic composition ratio, but it may be within the range of 5 to 40 atomic %, preferably 10 to 30 atomic %.

The thickness of the carrier transport layer according to the present invention is 1 to 50 μm,
It is preferably set within the range of 5 to 30 μm,
If it is less than 1 μm, the charge retention ability will be poor and the ghost phenomenon will become noticeable, and if it exceeds 50 μm, the image resolution will deteriorate and the residual potential will increase.

Although this carrier transport layer requires three types of atoms, SISC and H, there is no problem in doping with other atoms as necessary.

For example, doping with a group MA of the periodic table such as B can improve dark resistivity and carrier mobility, and can also shift the Fermi level at the interface between the carrier generation layer and the carrier transport layer. Since photocarriers generated in the carrier generation layer can be smoothly injected into the carrier transport layer, the photosensitivity can be increased and the residual potential can be reduced.

The carrier generation layer (3a) used in the present invention is a-Si
The composition can be determined within the range in which C:}I has photoelectric conversion properties, and according to experiments conducted by the present inventors, the composition is a-
It can be set as Si+-xC x (0<x<1). Furthermore, the present inventors have proposed that the a-SiC:
The composition range of the t-xC x film is O<x<0.5, preferably 0.
It is preferable to set it within the range of <x<0.3, and within this range, a photoreceptor with excellent photouniformity and a small residual potential can be obtained, with a high charging ability.

In addition, in determining the composition of B-Sil-xC x in this way, this composition ratio is
-It is better to make the Si ratio larger than the Si-C composition ratio of the Si-transfer H film, so that the photocarriers generated in the carrier generation layer move smoothly to the carrier transport layer, and as a result, the photosensitivity is further improved. As the value increases, the residual potential decreases.

This carrier generation layer is composed of H and halogen elements (F, CI, B).
r, etc.), and this content is preferably 5 to 40 atom %, preferably 10 to 30 atom %. Elements (BI All Ga, In, etc.)
and group ■a elements (P% As, Sb, etc.) at 0.05
5000ppm to 5000ppm, preferably 0.1 to 2000ppm
m may be contained, thereby compensating the conductivity type of the film or increasing the dark resistance value, and as a result, excellent charging ability can be obtained.

a-SiC carrier injection blocking layer (2) used in the present invention
A) prevents injection of carriers into the carrier transport layer (5), thereby increasing the surface potential of the photoreceptor. This layer (2a) has a content of S1 and C of 1
:9 to 9:1, preferably within the range of 2:8 to 8:2; outside this range, dark decay increases or residual potential increases.

Further, this carrier injection blocking layer (2a) may contain I} or a halogen element (F, Cl, Br, etc.), and the content thereof is related to the Si-C atomic composition, but the present inventors et al. According to experiments, it was found that it is sufficient to set the amount in the film to be in the range of 0.1 to 20 atomic %, preferably 1 to 10 atomic %.

Furthermore, this carrier injection blocking layer (2a) has mth
By introducing small amounts of Group A elements (B, AI, Ga, In, etc.) and Group Va elements (P, As, Sb, etc.), the conductivity type of the film itself is controlled to P° and N'', respectively. , the injection of carriers from the substrate can be further inhibited.For this purpose, the content of these Ma group and Va group elements is 50 to 5000 ppm, preferably 200 to 200 ppm.
It is best to set it to 0 ppm.

Further, the carrier injection blocking layer (2a) can be doped with at least one of oxygen or nitrogen to further enhance the carrier injection blocking effect, and the doping amount is related to other constituent elements, but the amount of doping in the film is 0. 1 to 30 atomic%
, preferably 1 to 20 atomic % G3''.

Furthermore, the thickness of this carrier injection blocking layer (2a) is 0.2 to 5. O Ilm , preferably 0.5 to 3.0,
It is preferable to set the thickness within the range of crm, and if the thickness is within this range, the ability to stop carriers from the substrate will be sufficient and the residual potential will be small.

According to the present invention, when forming a carrier injection blocking layer, a carrier transport layer, and a carrier generation layer using the same film forming apparatus, common constituent elements of Si and C are used, and the atomic composition ratios of each are set within a wide range. This feature makes it possible to use the same gas flow rate control system that uses a common St supply gas and C supply gas when continuously forming a carrier injection blocking layer, a carrier transport layer, and a carrier generation layer. As a result,
It becomes easy to control the flow rate of each gas.

Furthermore, according to the present invention, an a-SiC film or a-SiC:H
In forming the film, glow discharge decomposition method, ion plating method, reactive sotering method, vacuum evaporation method,
A thin film forming technique such as a CVD method can be used, and the raw material used therein may be solid, liquid, or gas. For example, glow discharge? Gaseous raw materials used in the solution include Si-based gases such as SIH4, Siz}I6, Si3Ha, CL, CzHt, CzHz, CJ6, C3
If a C-based gas such as Ha is used, furthermore, H t +
He, N e +Ar, etc. may be used as a carrier gas.

Various materials can be used for the surface protective layer (4) as long as they themselves have high insulation properties, high corrosion resistance, and high hardness characteristics, such as organic materials such as polyimide resin, Si, etc.
O■+ S i O + A 1 z O 2 + S
iC + S 1 3 N 4 1a-Si, a-
Si:H, a-Si:F+ a-SiC, a-S
Inorganic materials such as iC:H + a-SiC:F can be used.

Furthermore, according to the present invention, an a-SiC film or a-SiC:H
If SiHn gas and C2H2 gas are used as raw materials for forming a film by glow discharge decomposition, a high film formation rate (approximately 5 to 20 μm/hour) can be obtained.

Therefore, using both of these gases, a carrier injection blocking layer (
2a), carrier transport layer (5), carrier generation layer (3a)
) and the surface protective layer (4) are a-SiC film or a-SiC
By forming the :II film, the films can be formed continuously using the same film forming apparatus, and the film forming time can be significantly shortened. Incidentally, when an a-SiC film or an a-SiC:H film is produced using SiH4 gas, CH, and gas, the film formation rate is about 0.3 to 1 μm/hour.

Next, a capacitively coupled glow discharge decomposition device used in an embodiment of the present invention will be explained with reference to FIG.

In the figure, the first, second, third, fourth, and fifth tanks (6) (7
)(8)(9)(10), respectively, SiH4+Cz
Hz+BJb+Hz, No gas is sealed, H2
is also used as a carrier gas. These gases correspond to the first, second, . 3rd, 4th, 5th regulating valve (11) (
12)(13)(14)(15), and its flow rate is controlled by mass flow control 1:l-ra(1
6) (17) (18) (19) (20), and the first, second, third, and fourth tanks (6) (
7) The gas from (8) and (9) goes to the first main pipe (21), and the No gas from the fifth tank (1o) goes to the second main pipe (22).
). Note that (23) and (24) are stop valves.

Gas flowing through the first and second main pipes (21) and (22) is sent to the reaction tube (25);
) A capacitively coupled discharge electrode (26) is installed inside the electrode (26), and the appropriate high frequency to be applied thereto is 50W to 3Kw, and the appropriate frequency is IMHz to 10Milz power. Inside the reaction tube (25), a cylindrical film-forming substrate (27) made of aluminum is placed on a sample holder (28), and this holder (28) is connected to a motor (2).
9), and
The substrate (27) is heated to about 50 to 40
The reaction tube (25) is heated uniformly to a temperature of preferably about 150 to 300°C.
During film formation, a high vacuum condition (discharge fflo.t to 2.
Rotary pump (3
o) and a diffusion pump (31).

In the glow discharge decomposition device configured as above,
For example, when forming an a-SiC:H film (containing N, O, and B) on the substrate (27), the first, second, and third
, fourth and fifth regulating valves (11) (12) (13) (14)
Open (15) and calculate SiHa, CzHz+B from each
zHa. Emit Hz+No gas.

Discharge 1 is mass flow controller (16) (17)
(1 8) (1 9) (2 0) and is regulated by S i It. , CzHz, BZH&, H2 through the first main pipe (21), and at the same time a constant flow rate of No gas through the second pipe (22) into the reaction tube (
25). The inside of the reaction tube (25) is 0.1 to 2. A vacuum state of about QTorr, a substrate temperature of 50 to 400°C, a high frequency power of the capacitive discharge electrode (26) of IOW to 3 KW, and a frequency of 1 to 10
Coupled with the fact that the frequency is set to MHz, a glow discharge occurs, and the gas decomposes and contains elements of B, O, and N.
- SiC: H film is formed on the substrate at high speed.

However, in the Examples described later, when measuring the film formation rate, conductivity, and infrared absorption characteristics of the a-SiC:H carrier transport layer, a 3 x 3 cm rectangular flat plate was prepared, and the aluminum cylindrical substrate described above was used. A part of the circumferential surface of is cut out, a flat plate is installed in this notch, and a is placed on this flat plate.
-Produce a SiC:H film.

In addition, when measuring the film formation rate, conductivity, and infrared absorption characteristics, the flat plate materials used were aluminum and NE, respectively.
Made of SA glass and high resistance single crystal silicon.

〔Example〕

Next, embodiments of the present invention will be described in detail.

[Example 1] In this example, an a-SiC:H carrier transport layer was formed on an aluminum flat plate, and the film formation rate was measured.

That is, using the capacitively coupled glow discharge decomposition apparatus shown in FIG. 3, Si}I. The total flow rate of CzHz gas from the second tank (7) is 27
H2 gas was released from the fourth tank (9) as needed to form an a-SiC:H film based on the glow discharge decomposition method.

According to this example, SiHa gas and C.I. H. 200 gas
sccm and 500 sccm, and various measurement samples were prepared.

The measurement results are shown in FIG.

Figure 4 shows the atomic composition ratio of Si and C in the film (C/Si+C
), and the ○ mark, △ mark, and mouth mark indicate the case where H2 gas is not added and the flow rate is ffi200'sc.
cm, and flow rate of 500 sec, and characteristic curves for a, b, and c, respectively.

As is clear from Fig. 4, when H2 gas is not added, (
The deposition rate tends to increase as the C/Si +C) ratio increases. On the other hand, the flow rate of H2 gas is 20
Although the film formation rate tends to decrease as the H2 gas flow rate increases to 0 sccm and 500 sccm, high speed film formation of 6 μm/hour or more can be obtained even when the H2 gas flow rate is 500 seconds.

[Example 2] In this example, by the same manufacturing operation as [Example 1], a
When a -SiC:H carrier transport layer was formed on a NESA glass flat plate and the conductivity of the layer was measured, the results shown in FIG. 5 were obtained.

Figure 5 shows the atomic composition ratio of Si and C in the film (C/Si +
The conductivity for C) is shown, and the ○ mark, △ mark, and mouth mark respectively indicate that 112 gas is not added and ifl200 sc
cm, the plot is for a flow of 1500 sccm,
d+e+f are the respective characteristic curves.

As is clear from FIG. 5, the (C/Si +C) ratio is 0.
If it is within the range of 1 to 0.9, the conductivity is 10-
” It can be seen that it is less than Ω・cm.

[Example 3] An aluminum drum for a substrate finished to a mirror finish using an ultra-precision lathe using diamond vide was cleaned by ultrasonic cleaning and steam cleaning using an organic solvent, and then by drying.
It was installed in the reaction tube (25) of the capacitively coupled glow discharge decomposition apparatus shown in FIG. Then, SiH4 gas is supplied from the first tank (6), C2H2 gas is supplied from the second tank (7), and 821{& gas (UZ diluted 20
00 ppm), H2 gas from the fourth tank (9), and NO gas from the fifth tank (1o), each with a flow rate of 18
0 sccm, 90 sccm, 90 sccm, 200
A carrier injection blocking layer (2a) with a thickness of 2 μm was formed based on the glow discharge decomposition method in which the gas was discharged at 8 sccm, the gas pressure was set to 0.4 Torr, and the RF power was set to 0.2 W/cm2. .

Next, the third and fourth regulating valves (1 3) (1 4) are closed, and the total flow rate of SiH4 gas from the first tank (6) and CtHz gas from the second tank (7) is 2.
H2 gas is released from the fourth tank (9) at 50 sccm, 20 sccm as needed.
0 sccm, 500 sccm, and the gas pressure was set to Q. The thickness of
A carrier transport layer (5) of .mu.m was formed.

Next, by the same operation, SiH4 gas, C2H2 gas, and H2 gas were added at 200 sccm and 40 sccm, respectively.
m and 250 sccffi, and the gas pressure is Q.
．． A carrier generation layer (3a) having a thickness of 5 μm was formed by setting the RF power to 0.4 W/cm” at 5 Torr.

After that, the third regulating valve (11) is closed and the SiH. and gas and CtH! gas at 150 sccm and 10 sccm respectively.
It was discharged at a flow rate of 0 sccm, the gas pressure was set to 0.3 Torr, the RF power was set to 0.4 W/cm'', and the thickness was 0.5 μ.
A surface protective layer of m was formed.

Regarding the photoreceptors A to I obtained in this way, the surface potential,
When we measured the half-life exposure, residual potential, and image quality, we found that
The results shown in the table were obtained.

In the table, the image quality evaluation marked ◎ has high image quality contrast and no ghost phenomenon occurs at all even when copying at high speed (copying at 50 sheets/minute or more), and the mark O indicates that a slight ghost phenomenon occurs when copying at high speed. However, there is no practical problem,
The mark X indicates a case where the residual potential is high and the white background is noticeably blurred, making it unsuitable for practical use.

In addition, in this example, the manufacturing conditions of the a-SiC:H carrier transport layer set for each of photoreceptors A to (2),
That is, with the same (C/Si+c) ratio and H2 gas flow rate, only an a-SiC:H carrier transport layer was produced on a silicon single crystal flat plate by the same manufacturing operation as [Example 1], and a wave number of 2090 cm was produced. The infrared absorption coefficients at wave numbers of and 2860 cm-' were measured, and the results are shown in Table 1.

As is clear from Table 1, photoreceptors A to E and G are excellent photoreceptors suitable for practical use with large surface potentials, and can be provided as photoreceptors for high-speed copying. Since C has high photosensitivity and excellent charging ability, no ghost phenomenon occurred even during high-speed copying.
However, the ghosts F, H, and I were unsuitable for practical use because of the pronounced ghost phenomenon.

According to this example, the evaluation means for determining the superiority or inferiority of the photoreceptor is that the infrared absorption coefficient of the carrier transport layer has an absorption coefficient within a predetermined range for a predetermined wave number, and from Table 1, As revealed, its absorption coefficient is 2090 cm
− 1000 or more and 286 for the wavenumber of '
It can be seen that the photoreceptor of the present invention can be obtained if the wave number is 1000 or less with respect to the wave number of 0 cm-'.

In addition, in forming the carrier transport layer (5) in this example, the third regulating valve (13) was opened and the B. }l. 10 gas
The same image quality evaluation was obtained for each of the nine types of photoconductors corresponding to the photoconductors A to I obtained by emitting B at secm to form a layer (5) containing B.

〔Effect of the invention〕

As described above, according to the electrophotographic photoreceptor of the present invention, the dark resistivity and carrier mobility of the a-SiC:}l carrier transport layer formed as a functionally separated photoreceptor can be improved; As a result, the dark decay rate of the photoreceptor can be reduced and the charging ability can be increased, and as a result, an electrophotographic photoreceptor suitable for high-speed copying is provided.

Further, according to the electrophotographic photoreceptor of the present invention, the ratio of Si to C in a-SiC used in the carrier injection blocking layer, carrier transport layer, and carrier generation layer can be set within a large range, and the Si supply gas and C supply can be set within a large range. Each of the gases can be used in common for forming both layers, which makes it easier to control individual gas flow rates because the same gas flow control system can be used, and as a result, manufacturing control is easier. As a result, manufacturing efficiency can be improved. Furthermore, Si}la gas and C2H. Carrier injection blocking layer,
The carrier transport layer, the carrier generation layer, and the surface protection layer can be formed continuously and at high speed using the same film forming apparatus, thereby increasing manufacturing efficiency and significantly reducing manufacturing costs.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the layer structure of a functionally separated electrophotographic photoreceptor, Fig. 2 is a cross-sectional view showing the layer structure of a general amorphous silicon photoreceptor, and Fig. 3 is a cross-sectional view showing the layer structure of a general amorphous silicon photoreceptor. Capacitively coupled glow discharge decomposition device, FIG. 4 is a diagram showing the film formation rate of the carrier transport layer of the photoreceptor according to the present invention, and FIG. 5 is a diagram showing the conductivity of the carrier transport layer of the photoreceptor according to the present invention. FIG. l...Substrate 2, 2a...Carrier injection blocking layer 3, 3a...Carrier generation layer 4...Surface protection layer 5...Carrier transport layer (C/S*4/C month: Figure 5 (c/St + L procedure amendment (voluntary) August 8, 1986

Claims (1)

[Claims] A laminate comprising at least a carrier injection blocking layer, a carrier transport layer, and a carrier generation layer formed on a substrate,
The carrier injection blocking layer is made of amorphous silicon carbide, and the atomic composition ratio of carbon and silicon is 1:
The carrier generation layer is made of amorphous silicon carbide, the carrier transport layer is made of hydrogenated amorphous silicon carbide, and the atomic composition ratio of carbon and silicon is in the range of 1:9 to 9:1.
1 and 2 in the infrared absorption spectrum
An electrophotographic photoreceptor characterized in that an absorption coefficient at 860 cm^-^1 is 1000 or less and an absorption coefficient at 2090 cm^-^1 is 1000 or more.