JPH0715584B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to light used in a charge storage mode (here, light in a broad sense, which means electromagnetic waves including visible light, X-rays, ultraviolet rays, infrared rays, etc.). The present invention relates to a photoconductor having sensitivity and an electrophotographic photoreceptor.

2. Description of the Related Art As a photoconductor used as a photoconductor for electrophotography, which has sensitivity to light used in a charge storage mode, it has high photosensitivity, no pollution, and high hardness. Amorphous silicon (hereinafter referred to as a-Si) containing 10 to 40 atm% of hydrogen has been attracting attention as a modifier that reduces the amount of hydrogen.

However, the electrophotographic photoreceptor composed of a-Si described above has comprehensive characteristics such as dark resistance value, photoresponsiveness, low charge potential due to charge accumulation, and environmental characteristics such as humidity resistance. Still in need of improvement.

For example, as a first problem, an electrophotographic photoconductor using a-Si has a larger relative dielectric constant (OPC: OPC) than other photoconductor materials such as an organic photoconductor (hereinafter referred to as OPC) or Se. ~ 3,
Se: ~ 6, a-Si: ~ 11), and a large electrostatic capacity requires a large charging current when the surface is charged. For this reason,
Low surface potential (OPC, Se
However, the current situation is that it must be used at around 400V compared to 600-800V. This also makes it possible, for example, in a general copying machine using a two-component developer as an ordinary electrophotographic apparatus, particularly when an image is copied using a toner having a normal charge amount, an image having a high saturation density is continuously formed. It is difficult to get stable.

Further, a photoconductor having a large electrostatic capacity also has a problem in photosensitivity characteristics. For example, since the surface charge amount is larger than that of a photoconductor having a small relative permittivity, surface charges are canceled by photocarriers to lower the surface potential. More photons (photo
n) is required, and there are many practical disadvantages.

Second, when oxygen, carbon, nitrogen or the like is added to a-Si in order to increase the resistance of the photoconductor and improve the surface potential, a large residual potential remains during use. Further, upon repeated use, there is a problem that a ghost phenomenon occurs due to accumulated fatigue, or photoresponsiveness deteriorates.

Further, as a third problem, depending on the structure of the photoconductor, a problem such as "blurring" of the image at high temperature and high humidity cannot be ignored.

Problems to be Solved by the Invention As means for reducing the first capacitance, Japanese Patent Laid-Open No. 54-1
43645 discloses a function-separated type photosensitive member using an organic semiconductor material, and JP-A-56-24355 discloses a function-separated type photosensitive member using an inorganic semiconductor material.

When the former organic semiconductor material is used, it cannot be said to be an effective means because it does not function as a long-life photoreceptor due to the high hardness characteristic of a-Si.

In the latter case, the chalcogen material which is likely to be polycrystallized or the material having a large relative dielectric constant (~ 10 for SiC) is expected to improve the charging voltage by using a material having a large specific resistance. The problems such as the increase in residual potential, which was the second problem, are not solved, and the characteristics of a-Si are long life, high sensitivity, low residual potential, high charge potential and fast photoresponsiveness. There is a problem that it is not possible to obtain a photoconductor having

The present invention solves such problems, and an object thereof is to provide an electrophotographic photosensitive member having a reduced electrostatic capacity and an excellent photoresponsiveness.

Means for Solving the Problems In order to solve the above problems, the present invention provides a photoconductive layer that generates movable carriers by photoexcitation, and a charge that is efficiently injected by effectively injecting the carriers. The charge transfer layer has a structure in which a transfer layer is laminated, and the charge transfer layer contains tin nitride as a main component.

Action Tin nitride has an optical bandgap that greatly changes to ~ 3.0 eV or less depending on the composition ratio of nitrogen, and exhibits n-type conduction even if it is changed to 1.5 to 4.5 eV by adding silicon or germanium. . In addition, even with a material with a large optical band gap, the activation energy is small at 0.9 eV or less, and the electron mobility is high, so that electrons can be efficiently injected from the photoconductive layer into the conduction band of the tin nitride compound. A good photosensitive member can be easily obtained by controlling the respective optical band gaps. Furthermore, the relative permittivity of tin nitride compounds is as small as 5-9 for materials with an optical bandgap of 1.5-3.5 eV.

By using such a tin nitride as a charge transfer layer in a photoreceptor, a-Si, amorphous silicon germanium (hereinafter referred to as a-SiGe), amorphous germanium (hereinafter referred to as a-Ge), etc. Even if a photosensitive layer having a large relative dielectric constant is used as a photoconductive layer, a photosensitive member having a small relative dielectric constant can be obtained as a whole, and a photosensitive member having a high photosensitivity and a high surface potential can be obtained in practical use.

As the charge transfer layer, 1 to 80 μm, preferably 10 to 50 μm
m, the photoconductive layer is 0.5 to 50 μm, preferably 1 to 5 μm
It is desirable to form and use m.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. For forming an amorphous tin nitride film (hereinafter referred to as a-Sn _1-x N _x , where 0 <x <1 means a film containing hydrogen or halogen atoms) as a charge transfer layer used in the present invention. Is SnCl ₄ ,
Tetramethyl tin [(CH _{3) 4} Sn], tetraethyl tin [(C
₂ H ₅ ) ₄ Sn], a source gas of Sn atoms such as SnF ₂ that has been heated and melted, or a gas obtained by diluting these gases with a gas such as H ₂ , Ar, or He, and N ₂ , NH ₃ , H ₂ NNH ₂ , HN ₃ , HN ₄ N ₃ , F ₃ N, F ₄ N _{2 and} other plasma CVD methods using N atom source gases, Sn or S
_{nF 2, SnI 4, SnI 2} , SnCl 2, SnP, Sn 3 P, Ar of SnS as the _{target, H 2, N 2, NH} 3 reactive sputtering or reactive evaporation method in is employed.

In addition, a-Si as a photoconductive layer includes SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ,
SiF ₄ , SiHF ₃ , SiH ₂ F ₂ , SiH ₃ F, SiCl ₄ , SiHCl ₃ , SiH ₂ C
Plasma CV using source gases of Si atoms such as l ₂ and SiH ₃ Cl or gases obtained by diluting these gases with gases such as H ₂ , Ar and He
It can be formed by a D method or a reactive sputtering method or a reactive vapor deposition method in Ar, H ₂ with Si as a target. Also, a-Ge
Is GeH ₄ , Ge ₂ H ₆ , Ge ₃ H ₈ , GeF ₄ , GeHF ₃ , GeH ₂ F ₂ , GeH
_{3 F, GeCl 4, GeHCl 3} , GeH 2 Cl 2, GeH 3 Cl, plasma raw material gas or these gases Ge atoms such as GeF _2, GeCl ₂ with H _2, Ar, gas diluted with He or the like It is formed by the CVD method, or the reactive sputtering method or the reactive vapor deposition method in Ar, H ₂ using Ge as the target, and a-SiGe is similarly formed of the source gas of the Ge atom and the source gas of the Si atom. Plasma CVD method using a mixed gas, or a gas obtained by diluting this mixed gas with a gas such as H ₂ , Ar, or He, or reaction using a mixed target of Si and Ge or two targets of Si and Ge It is formed by a reactive sputtering method or a reactive vapor deposition method.

Similarly, when adding Si, Ge, or the like to a-Sn _1-x N _z , the source gas of Sn atoms and the source gas of Si or Ge atoms, or the mixed gas thereof is used as H ₂ , Ar, He, or the like. Plasma CVD using gas diluted with gas as source gas of Sn atoms
Or a reactive sputtering method or a reactive vapor deposition method using a target mixed with Si or Ge or a plurality of targets.

Next, an example using the reactive sputtering method will be described in Example 1, and an example using the plasma CVD method will be described in Examples 2 and 3 and Example 4.

Example 1 An explanation will be given with reference to the sectional view of the photoconductor of the present invention shown in FIG. The mirror-polished aluminum (Al) substrate 11 was placed in a magnetron sputtering apparatus, and after evacuation to 2 × 10 ⁻⁶ Torr or less, the substrate temperature was raised to 250 ° C. Using Sn as a target, Ar was introduced into the device at ₁ to 3 mTorr and N ₂ at ₂ to 6 mTorr, and a-Sn _1-x N _x layer 12 as a charge transfer layer was formed by high frequency power 300 to 500 W with a frequency of 13.56 MHz. With a thickness of 15 μm. Then, Ar was introduced at ₁ to 10 mTorr and H ₂ was introduced at 0.3 to 4 mTorr, and an a-Si layer 13 as a photoconductive layer was formed to a thickness of 1 μm at a discharge power of 200 to 800 W with a polycrystal as a target.

At this time, the a-Sn _1-x N _x layer 12 has a relative dielectric constant of 8 to 9 and is a charge generation layer. The a-Si layer 13 was 10-11. Also, the first
When the photoconductor having the structure shown in the figure is used as an electrophotographic photoreceptor and the photoreceptor characteristics are evaluated by negative charging, the saturation charge potential is 900V and the residual potential is 15V or less, even though the total film thickness is 16 μm. An electrophotographic photosensitive member having a very high degree and a small residual potential was obtained.

However, a photoreceptor having such a photoconductive layer formed on the surface tends to have a reduced charging potential in proportion to repeated charging. This is considered to be because the surface oxidation of a-Si in the photoconductive layer on the free surface is rapidly accelerated by the influence of ozone and the like, and the trap level in the oxide layer promotes the injection of electric charges on the surface.

Therefore, as shown in FIG. 2, a new surface coating layer 14 is formed on the free surface of the photoconductive layer 13 as Si _1-x N _x , Si _1-x C _x , Ge _1-x C _x , A
By forming a coating layer of l ₂ O ₃ , Al _1-x N _x , (0 <x1), aC: H (amorphous carbon) or the like in a thickness of 0.05 to 1 μm, the change in charging potential is reduced, and It was possible to prevent the occurrence of "blur" in the image when the temperature and humidity were high.

Example 2 FIG. 3 is a sectional view of the photoconductor in this example. Mirror-polished 90mm x 310mm Al drum substrate 21 with 55m distance between electrodes
One of them is placed in a capacitively coupled plasma CVD apparatus of m, and the inside of the reaction chamber is evacuated to 5 × 10 ⁻⁶ Torr or less, and then the Al substrate 21 is set to 150 to 2
Heat to 50 ° C. SnF ₂ 0.1 to 1 sccm, GeF _{4 1} to 5 scc
m, the NH ₃ is introduced 190～220Sccm, the pressure in the reaction vessel 0.2
After adjusting to ~ 1.0 Torr, a- (Sn _1-y Ge
_y ) _1-x N _x (0 ≦ y, x <1) layer 22 is formed with a thickness of 15 to 30 μm, and
Introduce 0.5 to 10 sccm of GeF ₄ , 100 to 200 sccm of SiH _4, and ₅ to 50 sccm of B ₂ H ₆ of 10 ppm concentration diluted with hydrogen, 0.2 to 2.0 Torr
The amorphous silicon-germanium (hereinafter referred to as a-SiGe: H: F) layer 23 containing fluorine and having B added at a discharge power of 150 to 500 W is formed to a thickness of 1 to 3 μm, and SiH ₄ is added to a thickness of ₅ to 10 scc.
m, the NH ₃ is introduced 100～200Sccm, pressure 0.2～1.0Torr, the discharge power 150～600W, the Si _1-x N _x layer 24 as a surface coating layer 0.1
.About.0.2 .mu.m was formed to obtain an electrophotographic photoreceptor.

This photoconductor is used by negative charging, and its photosensitivity
It has high sensitivity over a wide range of 400 to 850 nm, and by using the a-SiGe: H: F layer 23 as a charge generation layer as compared with the a-Si layer,
The photosensitivity was improved even in the infrared region, and this photosensitive member was mounted on a laser beam printer using a semiconductor laser of 800 nm as a light source, and clear printing was confirmed. In this case, the a- (Sn _1-y Ge _y ) _1-x N _x layer 22 has a narrow optical band gap, has a relative dielectric constant of 8 to 9, and can be used only as a hole blocking layer. Instead, it also functions as an absorption layer for laser light, thereby preventing a reduction in resolution due to reflection from the Al substrate 21. In addition, a- (Sn _1-y Ge _y ) with a relatively large dielectric constant
_1-x N _x is a tendency dark resistivity is small at room temperature. In this case, it can be increased by adding B or carbon to the a- (Sn _1-y Ge _y ) _1-x N _x layer 22. For example, a- (Sn _1-y Ge _y ) _1-x N _x with a relative permittivity of 8 is small at ~ 10 ⁹ Ω · cm, but 10 to 0.01 atm% C or B or both should be added. The resistance can be increased to ~ 10 ¹³ Ω · cm. As a result, the gradation can be reproduced further, and the printing excellent in the reproduction of the halftone can be achieved.

Example 3 a- (Sn _1-y Ge _y ) _1-x N _x (0 <y, x <1) layer as in Example 2
22 was formed by the plasma CVD method. At this time, tetramethyltin [(CH ₃ ) ₄ Sn] was used as a source gas of Sn atoms to obtain a film having a thickness of 15 to 30 μm. Since these films already contain carbon, the dark resistivity at room temperature is 10 ¹² to 10 ¹³ Ωcm.
And a high film was obtained, and printing excellent in halftone reproduction was possible. Here, tetraethyltin [(C ₂ H ₅ ) ₄ Sn] is replaced with Sn.
The same result was obtained when used as the atomic source gas. In addition, hydrogen is contained in the a- (Sn _1-y Ge _y ) _1-x N _x (0 <y, x <1) layer 22,
An electrophotographic photosensitive member containing fluorine and stable at 1 to 50 atm% even after repeated use was obtained.

Example 4 As in Example 2, a film was formed by the plasma CVD method. Substrate heating is controlled at 150-250 ℃, as shown in Fig. 4.
100 to 200 sccm of SiH ₄ on Al drum substrate 31, 100 to 200 sccm of 400 ppm concentration of BF ₃ diluted with hydrogen, gas pressure of 0.2 to 1.0 T
orr, discharge power of 100 to 400 W, and P-type a-Si layer 32 with B added to 0.
2-1 μm was formed. Subsequently, SiH ₄ is 100 to 200 sccm, 400 ppm BF ₃ diluted with hydrogen is ₁ to 10 sccm, and gas pressure is 0.2 to 1.
0 Torr, discharge power 100-400W, and B-doped i-type a-Si layer 33 1
˜2 μm formed. Furthermore, SnF ₂ is ₁ to 0.5 sccm, SiH ₄ is 1 to ₂ sccm, N ₂ is 150 to 200 sccm, and gas pressure is 0.2 to 1.0 Torr.
r, discharge power 300 to 600 W, a- (Sn _1-y Si _y ) _1-x N _x (0 <x, y <
1) A layer 34 having a thickness of 10 to 20 μm was formed to form an electrophotographic photoreceptor. The relative permittivity of a-Si: H is ~ 11, while a- (Sn _1-y
Si _y ) _1-x N _x layer 34 is as small as 5 to 7 and has an optical band gap of 2.3.
It is a big ~ 3.0ev with little loss due to light absorption.

Further, as in Example 2, a- (Sn containing 0.1 to 10 atm of carbon added)
_{By using the 1-y} Si _y ) _1-x N _x layer, an electrophotographic photoreceptor having a characteristic that the dark resistivity at room temperature was further increased and the halftone reproduction was excellent was obtained. This photoreceptor has a saturated charge potential of 1000 when positively charged.
When it was mounted on a commercial copying machine and tested, a good image was obtained and a printing durability of 200,000 or more was confirmed. In addition, a- (Sn _1-y Si _y ) _1-x N _x (0 <x, y <1)
It is clear that the layer contains hydrogen or fluorine at the same time as nitrogen, and an electrophotographic photoreceptor having a long life in the range of 1 to 50 atm% was obtained.

EFFECTS OF THE INVENTION As described above, the photoconductor according to the present invention has a- (Sn _1-x N _x (0 <x <1), a- (Sn _1-y Si _y ) as the charge transfer layer.
_1-x N _x (0 <x, y <1), a- (Sn _1-y Ge _y ) _1-x N _x (0 <y, x <
By using a layer containing 1) or the like as a main component, the electrostatic capacity of the electrophotographic photosensitive member used in the charge storage mode is reduced, and an excellent photosensitive member capable of high voltage operation with excellent optical response is provided. be able to.

[Brief description of drawings]

1 is a sectional view of a photosensitive member according to an embodiment of the present invention, FIG. 2 is a sectional view of another embodiment in which a surface coating layer is further formed on the photosensitive member of FIG. 1, and FIG. 3 is a laser beam printer. FIG. 4 is a cross-sectional view of a photoconductor of a preferred embodiment, and FIG. 4 is a cross-sectional view of a photoconductor of another embodiment suitable for positive charging. 11 …… Aluminum substrate, 12 …… a-Sn _1-x N _x layer, 13 …… a
-Si layer, 14 …… Surface coating layer, 21 …… Al substrate, 22 …… a- (Sn
_1-y Ge _y ) _1-x N _x layer, 23 …… a-SiGe: H: F layer, 24 …… Si _1-x N _x layer
Layer, 31 ... Al substrate, 32 ... P-type a-Si layer, 33 ... i-type a-Si
Layer, 34 …… a- (Sn _1-y Si _y ) _1-x N _x layer

Claims (5)

[Claims] 1. A photoconductive layer that generates movable carriers by photoexcitation, and a charge transfer layer into which the carriers are efficiently injected and effectively transported are laminated on a support, and the charge transfer is performed. An electrophotographic photosensitive member whose layer is mainly composed of tin nitride. 2. The electrophotographic photosensitive member according to claim 1, wherein the charge transfer layer contains at least one of germanium and silicon. 3. The electrophotographic photosensitive member according to claim 1, wherein the charge transfer layer contains at least either hydrogen or a halogen atom. 4. The photoconductive layer contains at least either hydrogen or a halogen atom, and is mainly composed of any one of amorphous silicon, amorphous germanium, and amorphous silicon germanium. The electrophotographic photosensitive member according to claim 1. 5. The electrophotographic photosensitive member according to claim 1, having a surface coating layer on the free surface.