JPH02148040A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance electrostatic charge holding ability and photosensitivity by laminating an a-SiGe layer obtained by adding germanium Ge to amorphous silicon (a-Si), and an a-Si layer. CONSTITUTION:The a-SiGe layer of formula I and the a-Si layer of formula II are laminated in this order on a conductive substrate. In formula II, the content of both of H and X amounts to at least about 40 atomic %, where X is halogen, thus permitting electrostatic charge holding ability and photosensitivity to be enhanced and light absorption in the a-Si layer to be decreased and image forming light to be effectively utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Al Industrial Field of Application) The present invention relates to an electrophotographic photoreceptor used in an electrophotographic image forming apparatus, and more particularly to a photoreceptor for a laser printer using a semiconductor laser as a light source (b) Conventional technology In recent years, some image forming apparatuses using electrophotography use semiconductor lasers as light sources.Currently in practical use, semiconductor lasers can provide stable high output in the wavelength range of 780 to 830 nm. Therefore, it is desirable to use a laser device in this wavelength range in terms of image forming efficiency.However, on the other hand, the sensitivity wavelength of general electrophotographic photoreceptors currently in practical use is at most 700 to 800 nm.
It is low, less than 0.00 nm. Therefore, it is expected that a photoreceptor having photosensitivity in the above-mentioned wavelength range will be put to practical use.

In fact, a-Si (amorphous silicon: Sill) is a photoreceptor that has photosensitivity in this wavelength band.
There is a-3iGe (amorphous silicon germanium: Si-Ge-H) which is added with Ge. When Ge is added to a-3i, the optical bandgap for 780 to 830 nm becomes smaller, making it compatible with laser equipment for this wavelength and acid.

Problems to be solved by the fc1 inventionHowever, a-3i with Ge added has a 780-830
Although it has the advantage of a smaller optical bandgap for nm, the dark specific resistance and gate conductivity are lower than that of the a-3i, resulting in an unclear image with poor contrast when forming an image. There was a problem.

Further, since a-3iGe has more carriers excited by heat than a-3i, when used as a photoreceptor, there is a problem that the charge retention ability is further deteriorated. That is, a photoreceptor included in an image forming apparatus is usually heated with a heater provided therein to prevent a moisture layer from forming on the surface. However, in a SiGe, excited carriers are generated by this heat and cancel the charge on the surface of the photoreceptor, so that the charge retention ability of the photoreceptor becomes worse.

In view of these problems, the present invention forms a photoreceptor by laminating an a-3iGe layer and an a-3i layer, and
An object of the present invention is to provide an electrophotographic photoreceptor with improved charge retention ability and photosensitivity by providing a -SiGe layer on the substrate side of the photoreceptor.

Another purpose is to increase the amount of H or halogen (X) contained in the a-3i layer to 4Qat% or more.
An object of the present invention is to provide an electrophotographic photoreceptor capable of effectively utilizing image forming light by reducing the amount of light absorbed in the -3i layer. By gradually changing the change toward the Si layer side, electrical and structural mismatches at layer boundaries are alleviated, charge traps are reduced, and charge retention after image formation is reduced. It is about providing.

(Means for Solving Problem d1) The electrophotographic photoreceptor of the present invention has amorphous Si-Ge-H-X (X: Haloken) laminated on a conductive substrate,
Furthermore, it is characterized by laminating amorphous Si-H-X (X: halogen).

Further, in the amorphous layer, at least the Si
-11-In the X layer, the total content of I'' and X is approximately 4
0 at$ or more, and furthermore, the a-3iG
In the e layer, the Ge content may be gradually decreased from the base side to the a-3i layer side.

(In the electrophotographic photoreceptor of the invention according to the f41 action, an a-3iGe layer and an a-3i layer are laminated, and a-3i is an a-8iGe layer.
The dark specific resistance is larger than that of e, and when the surface of the photoreceptor is charged by a charger, the charged charges are retained on the surface of the photoreceptor due to the presence of the a-Si layer. Then, when laser light is irradiated, carriers are excited in the a-3iGe layer, which move through the a-8i layer and cancel the charge on the surface of the photoreceptor. At this time, the a-3iGe layer with low gate charge is thin, and the distance that carriers travel through the a-3i layer is short, so that the carriers are less likely to be trapped on the way, and the generated carriers are This can be used effectively to cancel surface charges. As described above, in the photoreceptor of the present invention, the a-SiGe layer functions as a charge generation layer, and the a-3i layer functions as a charge retention layer and a charge transport layer.

Further, by providing the a-3i layer on the surface side and the a-SiGe layer on the side far from the surface (substrate side), the following effects can be observed. In the a-3iGe layer, carriers are excited by a heater provided on the photoreceptor. However, since these carriers are generated near the substrate of the photoreceptor, it is necessary for electrons or holes to move to the surface to cancel the charge on the photoreceptor surface. It is difficult for the photoreceptor to move, and the charges on the surface are difficult to cancel, which prevents the charge retention ability of the photoreceptor from deteriorating.

Furthermore, according to experiments conducted by the present inventors, it has been found that in an a-Si photoconductor, as the content of I (or H) increases, the optical hand gap, dark specific resistance, and gate conductivity increase. It was also found that these changes increase after approximately 40atχ.

In claim 2 of the present invention, since the total amount of 1 (and X (halogen) contained in the a-3i layer is approximately 40.lt% or more) The l gap increases and the light absorption rate of this layer decreases.For this reason, the amount of light reaching the a-3iGe layer on the T side increases, and when looking at the photoreceptor as a whole, the light is used effectively and the photosensitivity decreases. Also, ■1 halogen amount is reduced to approximately 40a.
By setting tZ or more to -■-, the dark specific resistance and bright conductivity are improved as mentioned above.

In addition, the total amount of F (and X) contained in the a-SiGe layer is 4
If the content is 0 a1% or more, the dark specific resistance and light conductivity of the a-SiGe layer itself will improve, resulting in an effect of improving charge retention ability and photosensitivity.

Furthermore, in claim 3 of the present invention, since the amount of Ge contained in the a-3iGe layer is gradually reduced from the substrate side to the a-Si layer side, the boundary between the a-Si layer and the aSiGe layer electrical and structural mismatches at Therefore, the amount of charge L, ramp, etc. at the boundary is reduced, and the amount of charge remaining on the photoreceptor is reduced.

(f) Example <Description of film forming apparatus> FIG. 9 shows an ECR (electron cyclot
1 is a diagram showing the configuration of a film forming apparatus using a ron resonance method. An a-SiGe layer, an a-3i layer, etc. are formed on a conductive substrate using this apparatus.

This film forming apparatus includes a plasma chamber 1 that generates plasma,
It has a deposition chamber 2 in which film formation is performed.

The plasma chamber 1 and the deposition chamber 2 are evacuated by an oil diffusion pump and an oil rotary pump (not shown).

The plasma chamber 1 has a cavity resonator configuration, and a waveguide 4
2.45GHz μ-waves are introduced through the channel.

Note that the μ-wave introduction window 5 is made of quartz glass through which μ-waves can pass. In the plasma chamber 1, there is a hydrogen gas introduction pipe 7 to 1.
12 gases are introduced. Further, a magnetic coil 6 is arranged around the plasma chamber 1, and a divergent magnetic field is applied to draw out the plasma generated here into the deposition chamber 2. The plasma is drawn out into the deposition chamber 2 through the plasma extraction window 3. A photoreceptor base 8 is located approximately in the center of the deposition chamber 2.
will be installed. The substrate 8 is a conductive phase, for example A7! In this embodiment, a drum-shaped one is used.

The drum-shaped base 8 is rotatably supported by a support mechanism (not shown) so that a film can be uniformly formed on the surface. The deposition chamber 2 is provided with a raw material gas introduction pipe 9 for introducing a raw material gas such as Sil14.

To explain the film forming operation in this apparatus, first, the plasma chamber 1 and the deposition chamber 2 are evacuated, and then 11° gas is introduced into the plasma chamber 1 and source gas is introduced into the deposition chamber 2.

For example, as the raw material gas, S i If 5Sizl16
．． SiF4. Silicon compounds containing hydrogen or halogen such as SiCIa and SiH□C12, and Get+
4. Gel Manila J is a compound containing hydrogen or halogen such as GeFaGeC14, GeFz, GeC1z. The gas pressure at this time is 10-3 to 10-'j, or
It is set to about r. Then, a μ wave is introduced into the plasma chamber 1 and a voltage is applied to the magnetic coil 6 to excite the plasma. This plasma flows from plasma extraction window 3 to 1.
(2) The raw material gas is guided to the deposition chamber 2, and the raw material gas is excited to form a film of the raw material gas on the substrate 8. At this time, since the base 8 is rotated, uniform film formation is performed. Furthermore, the uniformity of the film can be improved by setting the position and size of the plasma extraction window 3.

<Characteristics of a-3iGe and a-3i> First, the a-SiGe layer will be explained.

S i H4 and Ge114 are used as source gases, sil
+4. / (Sitl, (Ge114) =0.8
1, and the mixed gas flow rate was 120 se.
cm into the deposition chamber, and the gas pressure in the chamber was set at 2 to 5 m.
A photoreceptor having an a-SiGe layer was prepared by shaking between t and orr. Note that the μ wave output was 2.5 kW.

Figure 2 (A) shows the aSiGe formed in this way.
It is a diagram showing the amount of hydrogen contained in the layer, and the same figure (B)
and (C) are diagrams showing the dark specific resistance and bright conductivity of this photoreceptor, respectively. Note that the bright conductivity represents the results of an experiment using a laser beam of 830 nm as a light source. Furthermore, the ratio of Si to Ge in the formed a-8iGe layer is
was approximately 45 to 61 atχ with respect to Si.

As can be seen from these figures, the amount of hydrogen contained in the film changes at about 3.5 mtorr, and changes can also be seen in the dark specific resistance and bright conductivity. That is, when the gas pressure is approximately 2.5 to 3.5 mtorr, the amount of hydrogen contained in the film exceeds approximately 40 atχ, and both the dark resistivity and bright conductivity increase rapidly.

This improvement in darkening resistance and bright conductivity is due to the fact that
By adding more than t% of 11, the combination of Ge and 1 causes G.
This is thought to be due to a decrease in the dangling bonds of e. However, according to experiments conducted by the present inventors, 1
When the amount of 1 exceeds approximately 65 atχ, the optical band gap increases due to the addition of H, which cancels out the effect of the addition of Ge, resulting in poor sensitivity. Therefore, a
-3 The amount of I-1 contained in the iGe layer is approximately 40 to 65 at
It is desirable to set it to χ.

Next, the amount of Ge added in the a-3iGe layer will be described. Ge addition to a-8i is approximately 780-830 nm
This has the effect of reducing the number of optical hand gears,
On the other hand, there is a problem of a decrease in dark specific resistance and bright conductivity. Therefore, the amount of Ge added needs to be set to an appropriate value.

An a-SiGe layer was formed by varying the amount of Ge contained in the film formed by changing the mixing ratio of 8 Si and GeH 4 as raw materials. At this time, the raw material gas pressure was set to 2.5 to 3.5 mtorr to regulate the amount of H contained in the film (43 to 48 atχ). When the relationship between the amount of Ge in the formed film and the sensitivity to laser light of 780 to 830 nm was investigated, it was found that when the amount of Ge relative to Si is 5.3 at% or more IJ,
The addition had little effect and the sensitivity was poor. Also, Habo15
When it exceeded 0aLX, the dark specific resistance became too small to be used as a photoreceptor. Zunawara, a-3iG
The amount of Ge in the e layer is 53.3 to 150a relative to Si.
tχ, preferably 18-82 atL most preferably 4
It was 3-67a1χ.

In the above example, since hydrogen compounds of Si and Ge are used, only H is contained in the formed film, but halogens do not have the same effect as H, so halogens of Si and Ge are When a compound is used, the total content of halogen and )] may be approximately 40 to 55 atχ.

Next, the a-3i layer will be described.

When forming the a-8i layer, Si)(
4 was introduced into the deposition chamber 2, 112 gas was introduced into the deposition chamber 1, and a film was formed on the substrate of /J to form a photoreceptor. Further, the experiment was conducted while changing the gas pressure between 2 and 5 mtorr. Figure 3 (A) shows a-3 formed in this way.
It is a diagram showing Ill contained in the i film, and the same figure (B)
, (C) represent the dark specific resistance and bright conductivity of this photoreceptor, respectively. Note that for the bright conductivity, a 565 nm I-B D light source in which the a-3i layer has photosensitivity was used.

As can be seen from the same figure (B) and (C), Habo 2 to 3
．． Hi contained in the a-Si layer is 40at at 5mtorr
% or more, and the dark specific resistance increases accordingly.

That is, when the amount of H contained in the a-3i layer is 40 at% or less, the dark resistivity is at most 10"0 cm, but from around 40 atx or more, the dark resistivity increases to 10+2 Ωcm or more. , becomes.Zunawarako's 40 a
An a-81 photoreceptor containing 11 of tX or more has an extremely excellent charge retention ability. In addition, in the same figure ((As can be seen from the figure, this a-3i ill-sensitivity light has a high bright conductivity for light around 565 nm, and image formation is performed using a light source in the wavelength band near this a). In a device, it can be used as a photoreceptor having good photosensitivity.

Such an improvement in dark specific resistance is achieved when H is 40 at% or more.
This is believed to be because when it is contained, dangling bonds of Si atoms in the film can be reduced. In this example, since a hydrogen compound of Si is used as the source gas, only H is contained in the a-8 layer formed, but when a halide of Si is used as the source gas, A halogen is contained in the -8 layer, and as mentioned in the description of the a-SiGe layer, this halogen acts in the same way as H, and makes the characteristics of the a-3i layer similar.

As mentioned in Section 2 below, aSiG is
When forming the e layer and the a-Si layer, the pressure of the raw material gas is kept within a predetermined range (2.5-3.5 mt for the aSiGe layer).

By setting 11 and halogen contained in the layer to approximately 40 to 65 atχ, it is possible to form a film with good dark resistivity and gate electric conductivity. . Moreover, when the gas pressure is set to two consecutive gas pressures, both the film formation speed and the gas utilization efficiency are good. Furthermore, the film formation speed was 6 to 10 times faster than that of the plasma CV I) system used as a film formation system when creating A-3I photoreceptors for boat fishing. and the speed of
Film formation could be performed at a fairly high speed. In addition, when a film is formed using this ECR film forming apparatus (Sill□), no powder is generated, and on top of that, the powder adheres to the substrate of the photoreceptor and causes film formation defects. It was possible to form a photoreceptor of good quality without the problem of drying.

The a-3iGe layer and the a-3i layer can be formed as described above. a- containing approximately 40 to 65 atχ and halogen formed as described above;
The characteristics of the 3iGe layer and the a-Si layer are summarized as follows.

■a-3iGe layer Ge having photosensitivity to 780 to 830 nm
Soso power 11 effect. The amount of old Haloken is almost 40 atZ or more.
- By containing the a-Si layer, it is possible to improve both the dark specific resistance (approximately 10"Ωcm) and the gate electrical conductivity, although they are inferior to the a-Si layer.Also, as described in the prior art, the a-Si layer can be improved.
-The SiGe layer has more thermally excited carriers than the a-Si layer, so in order to improve the charge retention ability of the photoreceptor, it is desirable not to provide the a-8iG (] layer on the surface layer of the photoreceptor. .

(2) A-8i layer Sensitivity to 780 to 830 nm is low, but even when boron is not added, the dark specific resistance is very good as 1012 Ωcm, and the charge retention ability is excellent. According to experiments conducted by the present inventors, when boron is added, the dark specific resistance increases to 10'4Ωc.
It rises to about m. In addition, the gate electricity rate is also ■1. By containing approximately 40 at% or more of Haloken,
Moreover, the carrier has excellent transportation ability. Furthermore, since the optical band gap is also increased by adding H and halogen, the originally low sensitivity to 7803 to 830n becomes even lower, and the amount of light absorbed in that wavelength band decreases.

For these reasons, the present inventors used the a-SiGe layer as a charge generation layer and provided it near the substrate away from the surface layer of the photoreceptor, and the a-3i layer was used as a charge retention layer and a charge transport layer on the surface of the photoreceptor. It was set up in the department. FIG. 3 is a cross-sectional view of a photoreceptor according to an embodiment of the present invention, in which an intermediate layer 22, a photoconductive layer 23, and a surface layer 24 are arranged in this order on a conductive base 21 made of Aff or the like. Laminated. The feature of the present invention lies in the photoconductive layer 23, which has an a-SiGe layer 23a formed on the side closer to the base 21 and an a-3i layer 23b formed above the a-SiGe layer 23a.

<Experimental Example 1> First, film formation was performed under the conditions shown in FIG. 4 to create a photoreceptor. In this example, B216 was mixed with the raw material gas to add boron to make the photoreceptor p-type.

In the a-SiGe layer of the photoreceptor formed (Ge/
When the Si) value was measured, it was 51 atZ and HN was 4.
6 atZ. Further, the H content in the a-Si layer was 48 atZ. When image formation was performed using the photoreceptor thus formed using a laser beam of 830 nm as a light source, it was possible to obtain a high charge retention ability and a high quality image.

In addition, in order to change the amount of H contained in the a-3iGe layer and the a-3i layer, a photoreceptor was created by forming a film by changing only the gas pressure of the raw material gas while keeping other conditions the same. An image formation experiment was conducted using this method. FIG. 7 is a diagram showing the results. As you can see from the figure, the gas pressure is approximately 3.5 m.
When the temperature was below torr, both the charging characteristics and the quality of the formed image were very good. Note that at this time a-SiGe
The Hl contained in the a-3i layer was within the range of 40 to 65 atZ, and the ce amount (Ge/Si value) in the a-3iGe layer was 45-64 atZ.

<Experimental Example 2> Also, as shown in Figure 5Q, by changing the S itl and Get+4 meteors when forming the a-3iGe layer, the G in the formed a-8iGe layer is
The film was formed so that the e-content was as low as 11 layers.

FIG. 8 is a diagram showing an example of a change in the Ge-containing lid in the formed a-SiGe layer, in which 'ro is the substrate side, Tl-7
J<a-81 layer side. As shown in the figure, 4"I a-3i is formed by changing the raw material gas flow rate.
The amount of Ge contained in the Ge layer gradually decreases from ll1aX on the base side. Note that the raw material gas flow rate is such that the Ge content in the a-3i layer is 5.3 to 150a relative to Si.
It changes within a range such that Lχ.

When image formation was performed using a photoreceptor in which the Ge1 of the a-SiGe layer was gradually changed in this way, it was found that We were able to obtain even higher quality images, which is due to a
-3Ge near the boundary between the iGe layer and the a-Si layer
This is thought to be because the electrical and structural mismatch at the boundary between the two layers is alleviated because the content changes gradually. That is, the a-SiGe layer and the a-3i
When the Gc concentration changes drastically at the boundary between the two layers (as in Experimental Example 1), the charge at the boundary changes due to the difference in optical bandgap and structure between the two layers. 1-
Wrapping occurs, and even if static electricity is removed using a static eliminator or the like in each image forming process, charges remain inside the photoreceptor 7, which adversely affects the formed image. However, if the Ge content is gradually changed as in this example, these mismatches are alleviated, and the amount of charge remaining after image formation is reduced, making it possible to perform the next image formation favorably.

In the above example, the photoreceptor formed is made to be p-type by mixing B 2 H6 with the raw material gas, but in order to make the photoreceptor p-type, other , BCl3, B11. A boron compound such as or a compound of aluminum, gallium, or indium may be used.

<Experimental Example 3> An n-type photoreceptor can be formed by doping the a-SiGe layer or the a-si layer with phosphorus, nitrogen, antimony, oxygen, or the like. FIG. 6 is a diagram showing the manufacturing conditions for forming the n-type photoreceptor, in which a circle 13 is mixed with raw material gas G to dope doping. Other materials for phosphorus doping include Pct, Pct, and the like. Image formation was performed using the photoreceptor formed by mixing P in this way, and a good image could be formed as in the case of Bore I-1 doping.

As described above, the electrophotographic photoreceptor of the present invention has the a-3i layer laminated on the aSiGe layer, so that the aSiGe layer serves as a charge generation layer, and the a-Si layer serves as a charge retention layer and charge transport layer. Since it acts as a layer, the advantages of each layer are utilized, resulting in a photoreceptor with excellent photosensitivity and charge retention ability. In addition, since the a-Si layer is provided on the surface side and the aSiGe layer is provided on the side far from the surface (substrate side), even if thermally excited carriers are generated in the a-3iGe layer, which has many thermally excited carriers, the surface charge of the photoreceptor is The probability of cancellation is reduced, and a decline in the charge retention ability of the photoreceptor can be further prevented, resulting in a good photoreceptor.

Further, when the photoreceptor is configured as shown in claim 2, the amount of light absorbed by the a-Si layer is reduced, and the photoreceptor as a whole has the advantage of being able to effectively utilize light and increase photosensitivity. be. Further, dark specific resistance and bright conductivity are also improved.

Furthermore, by configuring the photoreceptor as shown in claim 3, electrical and structural mismatches at layer boundaries can be alleviated and residual charges can be reduced, resulting in improved image quality. There are advantages that can be improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a photoreceptor according to an embodiment of the present invention, and FIGS. 2 (A) to (C) show the gas pressure during the formation of the a-SiGe layer, the amount of H in the film, and the amount of H in the film. A diagram showing the relationship between the dark specific resistance and the bright conductivity of the film. Figures 3 (A) to (C) show the relationship between the gas pressure during a-8i film formation, the amount of [■] in the film, and the dark specific resistance of the film. , a diagram showing the relationship between the bright conductivity of the film, and Figures 4 to 6 are for a-3iGe.
Figure 7 shows the relationship between the gas pressure (hydrogen content) during film formation and the quality of the photoreceptor, and Figure 8 shows the lamination conditions for the a-8i layer. FIG. 9 is a diagram showing changes in the Ge content in the a-3iGe layer, and FIG. 9 is a diagram showing the configuration of a film forming apparatus using the ECR method. 3a Conductive substrate, intermediate layer, photoconductive layer, surface layer, a-SiGe layer, a-3il? 1. .

Claims (3)

[Claims] (1) On the conductive substrate, in amorphous state Si-Ge-H-X (X: halogen) Laminated, and further, in amorphous state Si-H-X (X: halogen) An electrophotographic photoreceptor characterized by being laminated with. (2) At least in the Si-H-X layer, H and
The electrophotographic photoreceptor according to claim 1, characterized in that the total content of is approximately 40 at% or more. (3) The Ge content in the Si-Ge-H-X layer is gradually decreased from the conductive substrate side to the Si-H-X side. Electrophotographic photoreceptor.