JPS61250651A - Photosensitive body - Google Patents

Abstract

PURPOSE:To solve a defect about a surface characteristics of a-Si type photosensitive body, and to improve a maintenance of an electric charge potential by providing a surface reforming layer on an electric charge generating layer, and an electric charge transfer layer under the electric charge generating layer respectively. CONSTITUTION:The photosensitive body 39 is constituted by laminating the P-type electric charge blocking layer 44 composed of an oxygen contg. a-SiC:H (a-SiCO:H) heavily dopped with the group IIIa element of the periodic table, the electric charge transfer layer 42 composed of an oxygen contg. a-SiC:H (a-SiCO:H), the electric charge generating layer 43 composed of a-Si:H and the surface reforming layer 45 composed of an oxygen contg. a-SiN:H(a-SiNO:H) on the drum like electroconductive supporting substrate 41. The photoconductive layer 43 has sufficiently large optical sensitivity of a ratio of the resistivity rhoD in a dark place and the resistivity rhoL in a light irradiation, thereby having a good optical sensitivity. In order to obtain a good picture quality after the 200,000 copies are taken, the oxygen content of the surface reforming layer is necessary to be 1-50qt%, and the oxygen content of the electric charge transfer layer is necessary to be 0.05-5at% respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a photoreceptor, such as an electrophotographic photoreceptor.

Conventional technology Conventionally, as an electrophotographic photoreceptor, Se or Se VcA
Photoreceptor doped with ssTe%sb, etc., ZnO or C
Photoreceptors, etc. in which dS is dispersed in a resin binder are known. However, these photoreceptors are environmentally polluting and
There are problems with thermal stability and mechanical strength.

On the other hand, electrophotographic photoreceptors using amorphous silicon (a-8i) as a matrix have been proposed in recent years.

a-8i has a so-called dangling bond in which the bond of 5i-8i is broken, and many localized levels exist within the energy gap due to this defect. For this reason, hopping conduction of thermally excited carriers occurs, resulting in a small dark resistance, and photoexcited carriers are trapped in localized levels, resulting in poor photoconductivity. Therefore, the dangling bonds are filled by compensating the defects with hydrogen atoms (H) and bonding Si KH.

Such amorphous hydrogenated silicon (hereinafter, asi
:Referred to as H. ) resistivity in the dark is 10”~109Ω
- about 1/10,000 times lower than that of amorphous Se. Therefore, a photoreceptor made of a single layer of a-8i:H has problems in that the dark decay rate of the surface potential is high and the initial charging potential is low. But on the other hand,
When irradiated with light in the visible and infrared regions, the resistivity decreases significantly, so it has extremely excellent properties as a photosensitive layer of a photoreceptor.

However, photoreceptors with ast, H surfaces are susceptible to surface chemical stability, such as the effects of long-term exposure to the atmosphere and moisture, and the effects of chemical species generated by corona discharge. sufficient consideration has not been made.

For example, items that have been left for more than a month will be affected by moisture.
It is known that the receptor potential is significantly reduced. on the other hand,
Amorphous hydrogenated silicon carbide (hereinafter referred to as a SiC
Regarding 71io) called :H, its manufacturing method and existence are @P
hi 1. Maj, Vol, 35″ (1978)
As its properties, it is known that it has high heat resistance and surface hardness, and that it changes over a range of 1.6 to 2.8 eV compared to ast:H. However, there is a drawback that the long wavelength sensitivity becomes poor due to the widening of the band gap due to the inclusion of carbon.

An electrophotographic photoreceptor combining such a StC:H and a-8i:H has been proposed, for example, in Japanese Patent Laid-Open No. 127083/1983. According to this, a-8i
A functionally separated two-layer structure was created in which the SH layer was used as a charge generation (photoconductive) layer, and the a5tCSH layer was provided below this charge generation layer as a charge transport layer, and the upper layer aSsaH increased photosensitivity in a wide wavelength range. The charging potential is improved by the lower layer a-8iC:H forming a heterojunction with the a-8i:H layer. However, the dark decay of the asxSH layer cannot be sufficiently prevented, and the charging potential is still insufficient to be practical.
The presence of the layer results in poor chemical stability, mechanical strength, heat resistance, etc.

On the other hand, in JP-A-57-17952, aSt:H
A first 5tCSH layer is formed on the charge generation layer as a surface modification layer, and a second 5tCSH layer is formed on the back surface (support electrode side).
0a StC:H layer is formed as a charge transport layer. Regarding this known photoreceptor, although effects such as prevention of attenuation and surface chemical stability can be expected by the surface modification layer, it has been found that there are the following problems.

That is, a-8i, which is a constituent material of the surface modified layer as described above,
The specific resistance (dark resistivity) ρ1 of C:H is 1013Ω-cm
is the limit, and since it cannot exceed this limit, the ability to retain the charged potential is insufficient. In addition, when SiO Discharge occurs and image deletion tends to occur. On the other hand, a-8t
C: Adsorption of active species such as H is Sin, is difficult to occur, but
As mentioned above, ρD is insufficient and the charging potential retention ability (particularly the retention ability under high temperature and high humidity conditions) is poor.

In addition, in known photoreceptors, the charge transport ability (carrier range (μτ
)=mobility x lifetime) and charge retention capacity (dark resistance ρD) are sufficient for the time being, but the temperature dependence of ρ is large, and as a result, the charged potential retention characteristics deteriorate at high temperatures, making it impossible to put it into practical use. .

C. Purpose of the Invention The purpose of the present invention is to provide a surface with excellent chemical stability, mechanical strength, heat resistance, etc., good photosensitivity, good ability to hold charged potential, and hardly cause bath surface discharge. Moreover, it is an object of the present invention to provide a photoreceptor that can maintain a stable high charging potential (K%) at high temperatures or high humidity and has excellent optical fatigue properties.

2. Structure of the invention and its effects, that is, the photoreceptor according to the invention has oxygen on the charge generation layer made of amorphous hydrogenated and/or fluorinated silicon in an amount of 1 to so atomic % (however, silicon atoms and nitrogen atoms The total number of atoms of and oxygen atoms is 100a tomi
c%. ) A surface modified layer made of amorphous hydrogenated and/or fluorinated silicon nitride containing 0.05 to 5 atoms of oxygen is provided below the charge generation layer.
= c% (However, the total number of atoms of silicon atoms, carbon atoms, and oxygen atoms is 100100 ato%.) Photoreceptor provided with a charge transport layer made of amorphous hydrogenated and/or fluorinated silicon carbide containing It is.

According to the present invention, since the a-8iN-based surface modified layer (for example, the surface-modified layer made of amorphous hydrogenated silicon nitride (a-8iN:H)) is provided, the a-8i-based adverse photosensitive effect is reduced. Defects regarding surface properties can be overcome. In other words, this surface modification layer improves the surface potential characteristics of A-8I-based adverse photosensitivity, maintains long-term potential characteristics, and maintains environmental resistance (preventing the effects of humidity, atmosphere, and chemical species generated by corona discharge). ), it has functions such as improved printing durability due to its high surface hardness, improved heat resistance when using a photoreceptor, and improved thermal transferability (particularly adhesive transferability).

Moreover, this surface modified layer contains 1 to 50 atoms of oxygen.
c% (hereinafter, "atomic%" is simply referred to as %), the specific resistance of the button and surface modification layer is greatly improved (>10"Ω-cm) 1. Especially at high temperatures or high humidity. Charge injection from the underlying surface is effectively prevented, and the ability to hold the charged potential is significantly improved.

Conversely, if the oxygen atom content is less than 1%, there is no such effect;
%, image blurring will occur due to adsorption of active species. Therefore, the oxygen content in the surface modified layer is 1 to 50%.
It is essential to set it to 5% to 30%.

Further, according to the present invention, there is provided a functionally separated photoreceptor,
Since the charge transport layer contains 0.05 to 5% oxygen, ρD can be effectively increased without reducing the charge transport ability (μτ), and the temperature dependence of ρD (dρD/
dT) can be kept small. Therefore, the charging potential retention characteristics are improved, and the upper limit temperature (and the upper limit humidity) at which the photoreceptor can be used can be increased.
If the above oxygen content is less than 0.05%, the effects of oxygen content (improvement of specific resistance, suppression of temperature dependence) will not be exhibited, and if it exceeds 5%, there will be too much oxygen and carrier mobility will be reduced. , that is, (μτ) decreases significantly, resulting in a decrease in sensitivity and an increase in residual potential. Therefore, it is essential to set the oxygen content to 0.05 to 5%, and it is particularly desirable to set the oxygen content to 0.1 to 3%).

In this way, by containing a predetermined amount of oxygen in both the surface modification layer and the charge transport layer, these synergistic effects are fully exhibited, improving the charging potential and reducing the temperature dependence of the charging potential. In particular, it is possible to improve the charging potential under high temperature and high humidity conditions.

The amorphous silicon nitride used in the present invention has a low coefficient of thermal expansion and high thermal conductivity compared to oxides and carbides, so it is resistant to thermal shock, and its mechanical strength and hardness do not decrease much even at high temperatures. Furthermore, it exhibits extremely high corrosion resistance against chemicals other than molten NaOH and HF.

E, Example Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 1 shows, for example, an a-8i electrophotographic photoreceptor 39 for positive charging according to this embodiment. This photoreceptor 39
A P-type charge blocking layer 44 made of oxygen-containing a-8iC:H (a-8iCO:H) heavily doped with a Group 1a element of the periodic table (for example, boron) is placed on a drum-shaped conductive support substrate 41 made of AI or the like. and oxygen-containing a-8ic:H(
a-8ico:H);
:H and a surface modification layer 45 made of oxygen-containing a-8iN:H (a-8iNo:H). The photovoltaic layer 43 has a ratio of resistivity ρD in the dark to resistivity ρ1 during light irradiation that is sufficiently large as an electrophotographic photoreceptor, and has good photosensitivity (% relative to light in the visible and infrared regions).

In this photoreceptor 39, based on the present invention, the surface modified layer 45 on the charge generation layer 43 contains 1 to 50% oxygen based on the total number of atoms of Si, N, and O. Therefore, remarkable effects such as an increase in specific resistance and an improvement in charging potential retention ability can be obtained. That is, as shown by curve a in FIG. 2, when simply a-8iN:H is used for the surface modification layer,
Its resistivity increases with nitrogen content, but 1013
It is known that it does not exceed Ω-cm. On the other hand, in the case of O content -8iN:H in which oxygen is contained in a-8iNSH based on the present invention (oxygen-containing lid is, for example, 5%), as already shown in the curve, the specific resistance is 1013Ω-c by determining the nitrogen content with a large increase in
It was confirmed that the value far exceeds m.

This 0-containing a-8iN:H layer 45 is indispensable for modifying the surface of the photoreceptor and making the a-Si type photoreceptor practically excellent. That is, it enables the basic operations of an electrophotographic photoreceptor, such as charge retention on the surface and attenuation of the surface potential due to light irradiation.
Therefore, the repetitive characteristics of charging and optical attenuation become very stable, and good potential characteristics can be reproduced even if left for a long period of time (for example, one month or more). On the other hand, in the case of a photoreceptor having an asx:H surface, it is easily affected by humidity, air, ozone atmosphere, etc., and the potential characteristics change significantly over time. In addition, since a-8iN:H has a high surface hardness, it has abrasion resistance during processes such as development, transfer, and cleaning, and it also has good heat resistance, so it can be used in processes that apply heat such as adhesive transfer. be able to.

In addition, oxygen atoms are added to the charge transport layer 42 made of a SiC:H at a total number of atoms of Si+C+O of 100 atomic%.
Oxygen in this content range increases the ρゎ of the charge transport layer 42 even under high temperature (or high humidity), and the ability to retain the charged potential as a photoreceptor decreases. Maintained stably.

In order to achieve the above excellent effects comprehensively, a
-8iN: It is important to select the nitrogen composition of the H layer 45. That is, the nitrogen atom content is Si + N 〇 = Zoo
When expressed as %, it is preferably 10 to 90%, more preferably 10 to 70%. When the N content is 10% or more, the above-mentioned specific resistance becomes the desired value, and the optical energy gap becomes approximately 2.0%. OeV or more, and due to the so-called optically transparent window effect for visible and infrared light, the irradiated light is a
-8i: It becomes easier to reach the H layer (charge generation layer) 43.
However, if the N content is less than 10%, the specific resistance tends to be less than a desired value, and part of the light is absorbed by the surface layer 45, which tends to reduce the photosensitivity of the photoreceptor. In addition, if the N content exceeds 90%, the amount of nitrogen in the layer increases, and the semiconductor properties are likely to be lost, and the deposition rate when forming the PCa S 1 :H film by the glow discharge method is likely to decrease. The N content is preferably 90% or less.

Also, the film thickness of a S I N: H1m 45 is 4
Within the range of 00X≦t≦500OA (especially 400A≦t≦
It is also important to select 200OA). That is,
If the film thickness exceeds 500OA, the residual potential vR
becomes too high and also causes a decrease in photosensitivity, making it easy to lose the good characteristics of the a-8i-based photosensitive material. Furthermore, if the film thickness is less than 400 Å, charges will no longer be charged on the surface due to the tunnel effect, resulting in an increase in dark decay and a decrease in photosensitivity.

The carbon atom content of the charge transport layer 42 is 30% or less, preferably 10 to 30% (the total number of Si+C+O atoms is 1001
00ato%. ), and the appropriate film thickness is 10 to 30 μm.

Further, the thickness of the charge generation layer 43 is preferably 1 to 10 μm.

If the thickness of the charge generation layer 43 is less than 1 μm, the photosensitivity will not be sufficient, and if it exceeds 10 μm, the residual potential will increase, which is insufficient for practical use.

Furthermore, in order to sufficiently prevent the injection of electrons from the substrate 41, the charge blocking layer 44 is for positive charging, and in order to sufficiently prevent the injection of electrons from the substrate 41, an element of Group 11a of the periodic table (for example, boron) is used at a flow rate of B2H/
S 1H4 = It is preferable to dope with 100 to 5000 fermentations to convert it into P type (or even P+ type). Further, for negative charging, it may be heavily doped with a Group Va element of the periodic table (for example, phosphorus) to make it N type (or even N'' type).

The charge blocking layer 44 does not necessarily need to be provided when used for negative charging, but if provided, it may contain 0.05 to 5% oxygen, or even 0.
．． It is preferable to form the a StC:H containing 1 to 3%. The carbon content of this a SiC:H may be 30% or less, preferably 10 to 30%.

If the blocking layer 44 has a thickness of less than 500 A, the blocking effect will be weak, and if it exceeds 2 μm, the charge transport ability will tend to deteriorate.

Note that each of the above layers needs to contain hydrogen.

In particular, the hydrogen content in the photoconductive layer 43 is essential to compensate for dangling bonds and improve photoconductivity and charge retention, and is preferably 10 to 30%. This content range also applies to the surface modification layer 45, the blocking layer, and the charge transport layer 42. Further, as impurities for controlling the conductivity type of the blocking layer 44, in addition to boron, A/, Ga, In,
Periodic table Ha group elements such as TI can be used, and periodic table Va group elements other than phosphorus such as As and Sb can be used as impurities for N-type conversion.

The layer structure of the photoreceptor of this example is summarized as follows depending on the mode of use.

[When using positive charging]

Charge blocking layer 44: Heavy doping with group MA elements of the periodic table.

For example, B, H, /SiH, = 100 to 5000 P (
Glow discharge decomposes under the following conditions (capacity ratio).

Charge transport layer 42: Lightly doped with NLA group elements of the periodic table.

For example, B, H, /8 tH4=o, 1~20 rp
Glow discharge decomposes under the following conditions (capacity ratio).

Surface modified layer 45: Nitrogen content and oxygen content may have a concentration gradient in the thickness direction of the photoreceptor.

Charge generation layer 43: Does not need to be doped in any way. In order to improve the charging potential and sensitivity, it may be lightly doped with an element of group 11a of the periodic table, depending on the case. For example, BoH, /SiH4≦20
Glow discharge decomposition under fermentation (capacity ratio) conditions.

[When using negative charge]

Charge blocking layer 44: There is no particular need to provide a charge blocking layer. In order to improve the charging ability, a charge blocking layer made of a-8iCO:H or a-8iCO:F doped with a group Va element of the periodic table may be provided as the case may be. For example, P.H.
, /SiH,≦2000 (capacity ratio).

Charge transport layer 42: Does not need to be doped in any way. In order to improve the charging potential and sensitivity, light doping with an element of Group Ma of the periodic table may be performed in some cases. For example, glow discharge decomposition is performed under the condition that B2H,/SiH4≦20 (capacity ratio).

Charge generation layer 43: Does not need to be doped in any way. In order to improve the charging potential and sensitivity, light doping with an element of group U[a of the periodic table may be performed depending on the case. For example, B, H, /SiH4≦20
Glow discharge decomposition under fermentation (capacity ratio) conditions.

Surface modified layer 45: Nitrogen content and oxygen content may have a concentration gradient in the thickness direction of the photoreceptor.

Next, a method for manufacturing the above-mentioned photoreceptor (for example, drum-shaped) and an apparatus therefor (glow discharge apparatus) will be explained with reference to FIG.

A drum-shaped substrate 41 is set rotatably vertically in a vacuum chamber 52 of this device 51, and a heater 55 is used to rotate the substrate 41.
can be heated from the inside to a predetermined temperature.
A cylindrical high frequency electrode 57 with a gas outlet 53 is disposed around and facing the substrate 41, and a glow discharge is generated between the electrode 57 and the substrate 41 by a high frequency power source 56. In addition, 62 in the figure is a source of SiH4 or a gaseous silicon compound, 63 is a source of Ol or a gaseous oxygen compound, and 64 is a source of a gaseous silicon compound.
is a hydrocarbon gas supply source such as CH4, 65 is NH,, N2
66 is a carrier gas supply source such as Ar, 67 is an impurity gas (e.g. B, H, PH)
3) Supply source 68 is each flow meter. In this glow discharge device, first, a support, for example, an AIl substrate 41
After cleaning the surface of the substrate 41, the substrate 41 is placed in a vacuum chamber 52, and the gas pressure in the vacuum chamber 52 is adjusted to 10" Torr and evacuated. The substrate 41 is heated to a predetermined temperature, particularly 100 to 350
C. (preferably 150 to 300 C.).
Next, using a high purity inert gas as a carrier gas, S
iH4 or gaseous silicon compound, CH,, N2 or N
Hl, 08, B, H, (or PH,) as appropriate in the vacuum chamber 52
A high frequency voltage (for example, 13.56
MHz) is applied. As a result, each of the reaction gases described above is decomposed by glow discharge between the electrode 57 and the substrate 41,
0-containing P-type a SIC: H, 0-containing a-8iC: H,
a-8i: H10-containing a SIN: H in the above layer 44
．． 42, 43, 45 on the substrate in succession (ie, corresponding to the example of FIG. 1).

In the above manufacturing method, the temperature of the support is set at 100 to 350° C. in the step of forming the Ka-8i layer on the support, so that the film quality (particularly the electrical properties) of the photoreceptor can be improved.

In addition, when forming the above a-8i photoreceptor photosensitive layer,
In order to compensate for dangling bonds, fluorine is introduced in the form of SiF, etc. in place of the above H or in combination with H, and a-8i: F, a-8i: H: F
, a-8iN:F, a-8iN:H:F, a-8ic
:F.

It is also possible to use a-8iC:H:F. In this case, the amount of fluorine is preferably 0.5 to 10%.

The above manufacturing method is based on the glow discharge decomposition method, but there are also sputtering methods, ion blating methods, and methods in which Si is evaporated while introducing activated or ionized hydrogen in a hydrogen discharge tube. (In particular, Japanese Patent Application Laid-Open No. 56-78413 (Patent Application No. 54-152) filed by the present applicant)
The above photoreceptor can also be manufactured by the method of No. 455).

Next, the present invention will be explained using a specific example.

An electrophotographic photoreceptor having the structure shown in FIG. 1 was prepared on a drum-shaped M support by a glow discharge decomposition method.

That is, first, the surface of the support, eg, a drum-shaped M substrate 410 having a smooth surface, is cleaned and then subjected to K.

The substrate 41 is placed in a vacuum chamber 52 shown in FIG. -300°C). Next, high-purity Ar gas was introduced as a carrier gas, and 0.5To
Preliminary discharge was performed for 10 minutes by applying high frequency power at a frequency of 13.56 MHz under a back pressure of rr. Next, a reaction gas consisting of SiH and B2H was introduced, and the flow rate ratio was 4:1:1:(1,0X10):(1,5X
10””) of (Ar+SiH4+CH4+O□+B,H
,) By glow discharge decomposition of the mixed gas, a P-type O-containing a StC:H layer 44 having a charge blocking function was formed to a predetermined thickness at a deposition rate of 6 μm/hr.

The charge transport layer 42 was also formed in the same manner. continuation,
B.H.

and CH4 were stopped, and 5i) (4 was discharge decomposed to form an ast:H layer 43 of a predetermined thickness. Ar+S
iH4+N2+0,) was decomposed by glow discharge together with a mixed gas, and a 0-containing a StN:H surface protective layer 45 of a predetermined thickness was further provided to complete an electrophotographic photoreceptor. The following measurements were performed using this photoreceptor.

Charged potential■. (■): Surface potential just before development measured with a 360 SX type electrometer (manufactured by Toretsuk) using a modified U-Bix 2500 machine (manufactured by Konishi Roku Photo Industry ■), with a photoconductor inflow current of 150 μA and no exposure. .

Half-reduced exposure amount EL/2()u)H-sec): Exposure amount required to reduce the surface potential by half from 500 V to 250 ■ using the above device. In image exposure, long wavelength components of 620 nm or more were cut using a dichroic mirror.

(The exposure amount was measured using a 550-1 type photometer (manufactured by EG and G)) Residual potential vR (v): After charging 500 vVc using the above device, 400
Surface potential after shallow irradiation with 30 lux of static eliminating light with a peak at nm.

200,000 copies live-action: A modified U-Bix 2500 machine (manufactured by Konishiroku Photo Industry Co., Ltd.) was used. The image quality evaluation is as follows.

◎ The image density is sufficiently high, the resolution and gradation are good, and the image is clear with no white lines or white spots. In other words, the image is extremely good.

○ Good image.

Δ Can be used for practical purposes ×　Image cannot be used for practical purposes.

Ru.

(1) If the oxygen content of the surface-modified layer is less than fat % or if the oxygen content of the charge transport layer is less than 0.05 at %, the charging potential will not be sufficient in a high-temperature environment.

(2) If the oxygen content of the surface-modified layer is more than 50 at%, or if the oxygen content of the charge transport layer is more than 50 at%, the photosensitivity will deteriorate and the residual potential will increase.

(3) If the oxygen content of the surface-modified layer exceeds 50a%, the resolution of the image after 200,000 copies will deteriorate.

Therefore, in order to obtain good image quality even after 200,000 copies are made at 50°C, the oxygen-containing lid of the surface-modified layer must be set at lat%≦[O
]≦50at%, and the oxygen content of the charge transport layer is 0.
It is necessary to satisfy 05at%≦[O]≦Sat%.

[Brief explanation of drawings]

1 to 4 show examples of the present invention, in which FIG. 1 is a cross-sectional view of an a-8i photoreceptor, FIG. 2 is a graph showing a comparison of a-8i CO resistivity, FIG. 3 is a schematic sectional view of the glow discharge device, and FIG. 4 is a diagram showing a comparison of the characteristics of the photoreceptor. In addition, in the symbols shown in the drawings, 39...... a-8i type photoreceptor 41...
......Support (substrate) 42...Charge transport layer 43...Charge generation layer 44...Charge blocking layer 45...
......Surface modified layer. Agent: Patent Attorney Hiroshi Aisaka Figure 1 Figure 2! ′! A content t (OtOm+C%) Figure 3

Claims (1)

[Claims] 1. 1 to 50 atomic% oxygen on a charge generation layer made of amorphous hydrogenated and/or fluorinated silicon.
(However, the total number of atoms of silicon atoms, nitrogen atoms, and oxygen atoms is 100 atomic%.) A surface modification layer made of amorphous hydrogenated and/or fluorinated silicon nitride containing the charge generating layer is provided. At the bottom, add 0.05 to 5 atomic% oxygen (however, the total number of silicon atoms, carbon atoms, and oxygen atoms is 100 atomic%).
c%. ) A photoreceptor provided with a charge transport layer comprising amorphous hydrogenated and/or fluorinated silicon carbide. 2. Add 0.05 to 5 atomic oxygen under the charge transport layer.
% (however, the total number of atoms of silicon atoms, carbon atoms, and oxygen atoms is 100 atomic %). A photoreceptor as described in item 1 of the scope.