JP2565314B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electrophotographic photoreceptor having negative charging ability, maintaining stable electrophotographic characteristics for a long period of time and having excellent durability. is there.

[Prior art and its problems]

In recent years, development of ultra-high speed copying machines and laser beam printers has been actively promoted, and along with this, electrophotographic photosensitive drums mounted in this equipment are required to have stable operation characteristics and durability.

In response to this requirement, hydrogen-exchanged amorphous silicon has been attracting attention because it is excellent in wear resistance, heat resistance, pollution-free property, photosensitivity and the like.

Amorphous silicon (hereinafter abbreviated as a-Si)
As the electrophotographic photosensitive member comprising, a laminated photosensitive member as shown in FIG. 3 has been proposed.

That is, according to FIG. 3, an a-Si carrier injection blocking layer (2) and an a-Si carrier (1) are formed on a conductive substrate (1) such as aluminum.
A photoconductive layer (3) and a surface protective layer (4) are sequentially laminated, and this carrier injection blocking layer (2) is formed to block carrier injection from the substrate (1) and reduce the residual potential. The surface protection layer (4) is made of a high hardness material to enhance the durability of the photoconductor.

However, according to this a-Si photoconductor, the dark resistivity of the a-Si photoconductive layer (3) itself is 10 ¹¹ Ω · cm or less, which increases the dark decay rate of the photoconductor. At the same time, it becomes difficult to increase the chargeability of itself, and as a result, when this photoconductor is used for high-speed copying, the previous image remains without being completely removed due to the optical memory effect, and the next image is formed. Along with that, the previous image appears (ghost phenomenon)
There is a problem.

In order to solve this problem, a function-separated type photoreceptor as shown in FIG. 1 has been proposed.

That is, according to FIG. 1 and FIG. 2, as a basic constitution, a carrier transport layer (5) and a carrier generation layer (3a) are sequentially laminated on a conductive substrate (1), and if desired, the conductive layer is formed. A carrier injection blocking layer (2a) is provided between the substrate (1) and the carrier transport layer (5), or a surface protective layer (4) is provided on the carrier generation layer (3a). The carrier transport layer (5) is formed of a material having a large dark resistance and a large carrier mobility, respectively, whereby a high-performance photoconductor having a high surface potential, an excellent photosensitivity, and a small residual potential can be obtained.

For this carrier transport layer (5), it is preferable to use hydrogen exchange amorphous silicon carbide having high resistance, wide bandgap and semiconductor characteristics.
It is proposed in the 192046 publication.

However, in the above-mentioned prior art, the positive or negative chargeability has not been sufficiently studied, and it is almost impossible to put it into practical use in view of the electrophotographic characteristics with the negative chargeability.

[Object of the Invention]

Therefore, an object of the present invention is to provide a durable electrophotographic photoreceptor having excellent negative charging ability and electrophotographic characteristics, that is, excellent dark decay and light decay characteristics.

Another object of the present invention is to provide an electrophotographic photosensitive member suitable for a laser printer having a spectral sensitivity to wavelengths in the near infrared region.

[Means for solving problems]

That is, according to the present invention, in an electrophotographic photosensitive member in which at least a carrier transport layer and a carrier generation layer are formed on a conductive substrate, the carrier transport layer and the carrier generation layer have a V a of 0 to 10,000 ppm in the periodic table. Provided is an electrophotographic photosensitive member which is composed of amorphous silicon carbide containing a group element and which is characterized in that the addition amount of the group Va element of the periodic table of the carrier generation layer is smaller than that of the carrier transport layer. It

 Hereinafter, the present invention will be described in detail.

The electrophotographic photosensitive member of the present invention is a function-separated layered photosensitive member based on the structure shown in FIGS. 1 and 2.

According to the present invention, in the above structure, amorphous silicon carbide (hereinafter abbreviated as a-SiC) is a main constituent element of the carrier transport layer, and for example, H or F is used to terminate the dangling bond of Si and C. , N, Cl, Br, I, and the like, and a V a group element in the periodic table within a predetermined range, can impart excellent negative charging ability as a photoreceptor. That is, Periodic Table V
By adding the group a element, the carrier transport layer becomes an n-type semiconductor.

This will be described with reference to FIGS. 4 (a) and 4 (b) by taking the photoconductor having the structure shown in FIG. 1 as an example. When the photoconductor is negatively charged by a charging means such as corona discharge (see FIG. 4).
(See FIG. (A)). Next, when exposure is performed, electrons and holes are generated in the carrier generation layer (3a), the holes are neutralized with the negative charges on the surface of the photoconductor, and the electrons are transferred to the transport layer and injected to the substrate side and grounded. , The electric charge of the entire exposed portion becomes zero. (See FIG. 4 (b)).

The carrier transport layer in the electrophotographic photosensitive member of the present invention is basically composed of a-SiC as described above,
Specifically, it is represented by the following formula (1) Si _(1-X ) Cx (1), and by setting 0.01 ≦ X ≦ 0.9, particularly 0.05 ≦ X ≦ 0.5, the dark resistance is 10 ¹¹ Ω.・ Can be more than cm.

In addition, as elements of Group V a of the periodic table to be added, P, N, As,
Sb can be raised, and P is particularly desirable. These are contained in the carrier transport layer in an amount of 0 to 10,000 ppm, particularly 0.1 to 1000 ppm.

The content of H and halogen elements for terminating the a-SiC dangling bond in the carrier transport layer is preferably 5 to 40 atom%, more preferably 10 to 30 atom% in the total composition.

Further, the thickness of the carrier transport layer is preferably set in the range of 1 to 100 μm, preferably 5 to 50 μm.
If it is less than m, the charge retention ability is poor and image formation becomes difficult, and if it exceeds 100 μm, the resolution of the image tends to deteriorate and the residual potential tends to increase.

The carrier injection blocking layer (2a) is provided to prevent carrier injection into the carrier transport layer (5), and is made of, for example, an organic material such as a polyimide resin, SiO ₂ , SiO, A.
l ₂ O ₃ , SiC, Si ₃ N ₄ , amorphous carbon, a-Si or a
-SiC is formed by using an inorganic material whose resistance value is controlled by doping hydrogen, fluorine, oxygen, nitrogen or the like into SiC. When Si-based or SiC-based is used, the group IIIa element of the periodic table such as boron and the Group Va element such as P are added within the range of 50 to 5000ppm to further enhance the carrier injection inhibition. You can In the electrophotographic photosensitive member of the present invention, since the carrier transport layer having the above-described composition can obtain a sufficiently large dark resistance, it is not always necessary to form this carrier injection blocking layer, According to experiments conducted by the inventors of the present invention repeatedly, the dark resistivity of the carrier transport layer is 10 or less.
It was confirmed that if the resistance is ¹³ Ω · cm or more, it can be sufficiently put into practical use as an electrophotographic photoreceptor without forming a carrier injection blocking layer.

In addition, various materials can be used for the surface protective layer (4) as long as they have high insulation properties, high corrosion resistance and high hardness characteristics, for example, the same as used for the carrier injection blocking layer described above. Inorganic materials and organic materials can be used, which can enhance the durability and environmental resistance of the photoconductor.

The thickness of each layer other than the carrier transport layer is 0.1 to 10θ for the carrier injection blocking layer and 0.1 to 10μ for the carrier generation layer.
m, and the surface insulating layer is preferably set to 0.1 to 10 μm.

With the above-mentioned structure, the function-separated electrophotographic photoreceptor of the present invention can be made to have a negative polarity on the surface by corona discharge, and according to the experiments of the present inventors, a charging ability of -600 V or more was obtained. As a result, it is possible to provide a photoreceptor having no practical problems.

Next, the present inventors have found that the negative charging ability can be further improved by selecting amorphous silicon carbide as a carrier generation layer compatible with the carrier transport layer having the above-described composition.

The a-SiC used in the carrier generation layer (3a) is represented by the following formula (2) Si _(1-Y) C _Y ··· (2), in which 0.01 ≦ Y ≦ 0.9, particularly 0.05 ≦ Y ≦ 0.5. Is desirable.

Even when this carrier generation layer is generated, a-SiC
As described above, it is necessary to use H or a halogen element for terminating the dangling bond, and the content of these elements is within the range of 5 to 40 atom%, preferably 10 to 30 atom% in the total composition. It should be.

As described above, the photoconductor of the present invention described above has a light wavelength of 300 to 900 nm.
However, according to the present invention, in the carrier generation layer made of a-SiC described above, V
By adding the a-group element, the photosensitivity can be enhanced especially in the near-infrared region, which enables application as a photoconductor for a laser printer. The amount of the Group Va element of the periodic table in the carrier generation layer is 10,000 ppm or less, especially
Although it can be blended in the range of 1000 ppm, it is important that the amount is small as compared with the amount of the Group Va element added in the periodic table in the carrier transport layer. When the amount added to the carrier generation layer exceeds the amount added to the carrier transport layer, injection of excited carriers from the carrier generation layer to the carrier transport layer is hindered, sensitivity decreases, and the residual potential increases. This is because, in the energy bands of the carrier generation layer and the carrier transport layer, the energy level of the carrier generation layer shifts to a lower energy side than that of the carrier transport layer, so that an energy barrier is created at the interface during injection of electrons into the carrier transport layer. This is because it is formed.

The elements of Group V a of the periodic table used include P, N, As, Sb and the like, which is the same as in the case of the carrier transport layer, and P is particularly preferable.

In producing the photoconductor of the present invention, a thin film forming technique such as a glow discharge decomposition method, an ion plating method, a reactive sputtering method, a vacuum vapor deposition method or a CVD method can be used for producing the inorganic photoconductor.

For example, when forming the carrier transport layer as described above in the photoreceptor of the present invention, glow discharge decomposition method is desirable,
SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , SiF ₄ , and SiCl as the gas source used
Si-based gas such as ₄ , SiH ₂ Cl ₂ , CH ₄ , C ₂ H ₄ , C ₂ H ₂ , C ₂ H ₆ , C ₃ H ₈ , C
A C-based gas such as F ₄ CCl ₄ may be used, and H ₂ , He, Ne, A
You may use r etc. as a carrier gas. As gas containing Group Va element of the periodic table, PH ₃ , N ₂ , NH ₃ , AsH ₃ , AsF ₃ , Sb
H _{3 and the} like can be mentioned. According to experiments by the present inventors, it has been found that an extremely large film forming rate (about 5 to 20 μm / h) can be obtained by using C ₂ H ₂ as the C-containing gas among the above-mentioned gases. Therefore, at least C ₂ H ₂ gas, Si-containing gas, and 10 ^{−6 to} 1 mol% group V a element-containing gas of the periodic table are selected as preferable reaction gases when forming the carrier transport layer. The specific composition of the reaction gas is (C ₂ H ₂ gas: Si-containing gas)
It is desirable that the composition ratio is 0.05: 1 to 3: 1.

According to the present invention, a-SiC is used as the carrier generating layer for the purpose of further improving the negative charging ability. Even in the formation of this carrier generating layer, at least C ₂ H ₂ gas and Si-containing gas are selected. Then, this may be used in the same composition ratio as when forming the carrier transport layer, and the reaction gas may be decomposed by glow discharge to form it on the carrier transport layer.

Furthermore, according to the present invention, a-SiC containing an element of Group V a of the periodic table is used as the carrier generation layer for the purpose of improving the spectral sensitivity to near infrared light. Also, as in the case of forming the carrier transport layer, a C ₂ H ₂ gas, a Si-containing gas, and a group V a element-containing gas of the periodic table are used, and the group V a element-containing gas of the periodic table is 1 mol% or less. Although it is mixed in a ratio, for the reasons described above, the periodic table V in the reaction gas during the formation of the carrier generation layer
It is important that the proportion of the group a element-containing gas is smaller than that when the carrier transport layer is formed.

When a carrier injection blocking layer or a surface protection layer is provided as shown in FIG. 1 or 2 in the photoreceptor of the present invention, the material thereof is SiC, a-Si; H, a-SiC, amorphous. When carbon or those doped with impurities are used, they can be continuously formed by using the same film forming apparatus, and the film forming time can be remarkably shortened.

In the layer structure of the photoreceptor of the present invention, when an organic material is used, any of them can be formed by a known means. Specifically, a polymer material, an organic pigment, an organic dye or the like is used in a volatile solvent. It can be provided by a dipping method, a doctor blade method or the like using a coating solution dissolved or dispersed in.

Next, the capacitively coupled glow discharge decomposition apparatus used in the embodiment of the present invention will be described with reference to FIG.

In addition, PH ₃ gas is used as an example of the group V a element-containing gas of the periodic table.

In the figure, the 1st, 2nd, 3rd, 4th, 5th tanks (6) (7)
(8) (9a) and (9b) are sealed with SiH ₄ , C ₂ H ₂ and PH ₃ (PH ₃ is diluted to 33 ppm in H ₂ gas), H ₂ and NO gas, respectively. ₂ is also used as a carrier gas.
These gases are released by opening the corresponding 1st, 2nd, 3rd, 4th and 5th regulating valves (10) (11) (12) (13a) (13b), and their flow rates are determined by the mass flow controller. (14)
(15) (16) (17a) (17b) is controlled and sent to the main pipe (18). Incidentally, (19) is a stop valve.

The gas flowing through the main pipe (18) is
0), the capacity coupling type discharge electrode (21) is installed inside the reaction tube, and the power applied to this is 50W to 3kW, and the frequency is 1MHz to 10MHz. . Inside the reaction tube (20), a cylindrical conductive substrate (22) for film formation made of aluminum is provided as a sample holder (23).
It is mounted on the holding table (23), and the holding table (23) is rotatably driven by a motor (24), and
The substrate (22) is uniformly heated by a suitable heating means to a temperature of about 50 to 400 ° C, preferably about 150 to 300 ° C. Furthermore, the inside of the reaction tube (20) requires a high vacuum state (discharge voltage 0.1 to 2.0 Torr) when forming an a-Si film or an a-SiC film, so that the diffusion pump (25) and the rotary pump ( 2
6) connected to.

In the glow discharge decomposition apparatus configured as above, for example, a P-doped a-SiC film is used as a substrate (2
2) At the time of forming on top, the 1st, 2nd, 3rd and 4th regulating valves (10) (11) (12) (13a) are opened and the 1st, 2nd, 3rd and 4th tanks ( 6) (7) (8) (9a) releases SiH ₄ gas, CH ₂ H ₂ gas, PH ₃ gas and H ₂ gas, respectively, and the released amount of these is mass flow controller (14) (15) (16)
It is regulated by (17a) and fed into the reaction tube (20) through the main pipe (18), and the inside of the reaction tube (20) is in a vacuum state of 0.1 to 2.0 Torr and the substrate temperature is 50 to 400.
At the same time, a high frequency power of 1MHz to 10MHz was applied to the capacitive discharge electrode (21) at a frequency of 50W to 3kW, and a glow discharge occurred, the gas was decomposed, and the P-containing a-SiC film was formed on the substrate. Formed at high speed on top.

〔Example〕

Hereinafter, comparative examples will be described with reference to (Example 1), (Example 2) and (Example 3), and examples of the present invention will be described with reference to (Example 4) and (Example 5).

(Example 1) An aluminum drum for substrates, which was mirror-finished by an ultra-precision lathe using diamond vide, was cleaned by ultrasonic cleaning using an organic solvent and steam cleaning, followed by drying, and the capacity shown in FIG. It was installed in the reaction tube (20) of the combined glow discharge decomposition apparatus.

Then, 100 sccm of SiH ₄ gas from the first tank (6),
20 sccm of C ₂ H ₂ gas from the 2nd tank (7), 100 sccm of PH ₃ gas from the 3rd tank (8), and H ₂ from 4th tank (9a)
300 sccm gas and 2.5 NO gas from the 5th tank (9b)
Emit at a flow rate of sccm, gas pressure 0.5 Torr, high frequency power 1
The carrier injection blocking layer made of a-SiC: H: P: N: O was formed on the basis of the glow discharge decomposition method while setting the substrate temperature to 00 W and the substrate temperature to 300 ° C.

Further, using the same apparatus, a carrier transport layer (5) made of a-SiC, a carrier generation layer (3a) made of a-Si, and a surface protective layer (4) made of SiC were sequentially formed under the conditions shown in Table 1. Then, a photoreceptor having a thickness of 30 μm was obtained.

The surface potential of the electrophotographic photosensitive member thus obtained,
When the characteristics of dark decay and light decay were measured, the results shown in FIG. 6 were obtained. This was negatively charged by −5.6 kV corona discharge in the dark, and the change of surface potential with time in the dark and 650 n
This is a graph showing the change over time in the surface potential immediately after irradiation with m monochromatic light (exposure amount: 0.3 μW '/ cm ² ). In the figure, A is a dark decay curve and B is a light decay curve.

As is clear from Fig. 6, the surface potential after 2 seconds of charging is as high as practical at about -600 V. From the result of light attenuation, the surface potential becomes smaller immediately after exposure, and the residual potential is remarkably high. It is getting smaller.

Incidentally, when a positive charge of +5.6 kV was applied to the same photoreceptor, it was only practically +70 V and not practical.

(Example 2) then Example 1 and SiH ₄ in a similar manner, H _2, using C ₂ H _2, PH ₃ and NO each gas, at a flow rate shown in Table 2 a-Si: H: P: N: O
A carrier injection blocking layer made of a, a carrier transport layer made of a-SiC (X≈0.3) (5), a carrier generation layer made of a-SiC (Y≈0.15) (3a), and a surface protection layer made of SiC (4). Was formed to obtain a photoconductor having a thickness of 30 μm.

The obtained photoconductor was charged by -5.6 kV corona discharge in the same manner as in (Example 1), and dark decay and light decay were measured.
The results shown in the figure were obtained.

As is clear from FIG. 7, it showed an excellent negative charging property of −680V.

(Example 3) Next Example 1 SiH in the same manner as in _4, using _{H 2, C 2 H 2,} PH 3 and NO each gas, a-Si at a flow rate shown in Table 3: H: P: N: O
A carrier injection blocking layer made of a, a carrier transport layer made of a-SiC doped with about 20 ppm of P (5), a carrier generation layer made of a-Si doped with about 10 ppm of P (3a)
And a surface protection layer (4) made of SiC are formed, and the thickness is 30μ
m photoconductor was obtained.

The obtained photoreceptor was charged by -5.6 kV corona discharge in the same manner as in (Example 1), and dark decay and light decay were measured.
The results shown in the figure were obtained.

As is clear from FIG. 8, it showed an excellent negative charging property of −650V.

(Example 4) In the same manner as in Example 1, using each gas of SiH ₄ , H ₂ , C ₂ H ₂ , PH ₃ and NO at the flow rates shown in Table 4, a-Si: H: P: N A carrier injection blocking layer made of: O, a carrier transport layer made of a-SiC doped with about 20 ppm of P (5), a carrier generation layer made of a-SiC (3a), and a surface protection layer made of SiC (4). Then, a photoconductor having a thickness of 30 μm was obtained.

The obtained photoreceptor was charged by corona discharge of -5.6 kV in the same manner as in (Example 1), dark decay and light decay were measured, and the results shown in FIG. 9 were obtained.

As is clear from FIG. 9, it showed excellent negative charging property of −750 V, and it was confirmed that the use of a-SiC as the carrier generation layer improves the negative charging ability.

(Example 5) Example 1 and using _{SiH 4, H 2, C 2} H 2, PH 3 and NO each gas in the same manner, at a flow rate shown in Table 5 a-Si: H: P: N : O carrier injection blocking layer, about 20 ppm P-doped a-SiC carrier transport layer (5), about 10 ppm P
Carrier generation layer (3a) consisting of a-SiC doped with
And a surface protection layer (4) made of SiC are formed, and the thickness is 30μ
m photoconductor was obtained.

The obtained photoreceptor was charged by a corona discharge of -5.6 kV in the same manner as in (Example 1), and dark decay and light decay were measured and the results shown in Fig. 10 were obtained.

As is clear from FIG. 10, it showed an excellent negative chargeability of −760V.

Next, the spectral sensitivity of the photoconductors manufactured in (Example 1) to (Example 5) was measured with light having a wavelength of 770 nm.
(Example 1) 0.18 cm ² / erg, (Example 2) 0.15 cm ² / erg, (Example 3) 0.20 cm ² / erg, (Example 4) 0.16 cm ² / erg, (Example 5)
Was 0.26 cm ² / erg. From these results, it was confirmed that the layer structure of (Example 5) significantly improved the sensitivity.

〔The invention's effect〕

As described above in detail, the electrophotographic photosensitive member of the present invention has an amorphous silicon carbide doped with an element of Group V a of the periodic table as a carrier transport layer, and further an amorphous silicon carbide or a periodic table with the amorphous silicon carbide as a carrier generation layer. By doping the group V a elements in a specific relationship, they show practically excellent negative charging ability and electrophotographic characteristics, and also have excellent sensitivity in the near-infrared region. The application can be expanded even as the above.

[Brief description of drawings]

FIG. 1 is a sectional view showing the layer structure of a photoconductor used in an embodiment of the present invention, FIG. 2 is a sectional view showing the layer structure of a photoconductor used in another embodiment of the present invention, and FIG. Sectional views showing a general layer structure of the photoconductor, FIGS. 4 (a) and 4 (b) are diagrams for explaining electrophotographic characteristics of the electrophotographic photoconductor of the present invention, and FIG. 5 is an embodiment of the present invention. Explanatory diagrams, 6, 7, 8, 9 and 10 of the capacitively coupled glow discharge decomposition apparatus used in the examples are the dark decay curve and light decay curve of the electrophotographic photoreceptor of the present invention. It is the figure which each showed. 1 ... Substrate 2,2a ... Carrier injection blocking layer 3,3a ... Carrier generation layer 4 ... Surface protection layer 5 ... Carrier transport layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hitoshi Takemura Hitoshi 6-16, Haseno, Jamizo-cho, Yokaichi-shi 6 Kyocera Co., Ltd. Shiga Yokaichi factory (72) Inventor Kokichi Ishikura, 1166, Haseno, Hachimi-cho, Yokaichi-shi 6 Kyocera Corporation Shiga Yokaichi Factory (56) References JP-A-61-126557 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member comprising a conductive substrate on which at least a carrier transporting layer and a carrier generating layer are formed,
The carrier transport layer and the carrier generation layer are 0 to 10,000.
The periodic table V of the carrier generation layer, which is composed of amorphous silicon carbide containing an element of Group V a in ppm of the periodic table V
An electrophotographic photosensitive member capable of being negatively charged, characterized in that the added amount of the group a element is smaller than that of the carrier transport layer.