JPS628161A - Photosensitive body - Google Patents

Abstract

PURPOSE:To improve adhesion between a surface modifying layer and an electrostatic charge generating layer and to enhance resistances to mechanical damage and printing by forming between the surface modifying layer and the charge generating layer an interlayer containing an amount of C or the total amount C and 0 smaller than that of the surface modifying layer and increasing from the side of the charge generating layer toward the side of the surface modifying layer. CONSTITUTION:A charge transfer layer 42 made of amorphous silicon hydride and/or fluoride, the charge generating layer 43 made of amorphous silicon hydride and/or fluoride, the interlayer 46 made of amorphous silicon hydride and/or fluoride containing at least C of C and 0, and the surface modifying layer 45 made of amorphous silicon hydride and/or fluoride containing at least C of C and 0 in an amount of at least >=50atom.% are laminated in succession. The content of C or the total content of C and 0 of the interlayer 46 is smaller than that of the surface modifying layer 45, and continuously increases from the side of the charge generating layer 43 toward the side of the surface modifying layer 45.

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, Ss or Se has AS%
Photoconductors doped with Te5Sb or the like, photoconductors in which ZnO or CdS is dispersed in a resin binder, and the like are known. However, these photoreceptors have problems in terms of environmental pollution, thermal stability, and mechanical strength.

On the other hand, electrophotographic photoreceptors using amorphous silicon (a-3i) as a matrix have been proposed in recent years.

a-3i has a so-called dangling bond in which the bond of 5i-3i is broken, and many localized levels exist within the energy gap due to this defect. For this reason, popping 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, we replaced the above defects with hydrogen atoms (
The dangling bonds are filled by bonding H to St by compensating with H).

Such amorphous hydrogenated silicon (hereinafter referred to as a-3
It is called t:H. ) has a resistivity in the dark of 103 to 10
9Ω-b, which is about 1 compared to amorphous Se.
It's even lower than 1/10,000. Therefore, a photoreceptor made of a single layer of a-3i:H has problems in that the dark decay rate of the surface potential is high and the initial charging potential is low.

However, on the other hand, when irradiated with light in the visible and infrared regions, the resistivity is greatly reduced, so it has extremely excellent properties as a photosensitive layer of a photoreceptor.

Figure 5 shows a-3t using the above a-3t:H as a base material.
An electrophotographic copying machine incorporating a system photoreceptor 9 is shown.

According to this copying machine, a glass document mounting table 3 on which a document 2 is placed and a platen cover 4 that covers the document 2 are disposed in the upper part of a cabinet 1. Below the document table 3,
An optical scanning table consisting of a first mirror unit 7 equipped with a light source 5 and a first reflecting mirror 6 is provided so as to be movable linearly in the left-right direction of the drawing, and the optical path length between the document scanning point and the photoreceptor is kept constant. 2nd mirror unit) 20 is the first
The mirror unit moves in accordance with the speed of the mirror unit, and the reflected light from the document table 3 side is incident on the photosensitive drum S as an image carrier through the lens 21 and the reflection mirror 8 in a slit shape. . A corona charger 1 is installed around the drum S.
0, a developing device 11, a transfer section 12, a separation section 13, and a cleaning section 14 are arranged, and the copy paper 1B fed from the paper feed box 15 through the paper feed rollers 16 and 17 is transferred with the toner image on the drum 9. Afterwards, the image is further fixed in the fixing unit 19 and then discharged onto the tray 35. In the fixing section 19, a heater 22
A fixing operation is performed by passing the developed copy paper between a heating roller 23 having a built-in image and a pressure roller 24.

However, photoreceptors with a-5i:H surfaces have problems with surface chemical stability, such as the effects of long-term exposure to the atmosphere or moisture, and the effects of chemical species generated by corona discharge. , has not been sufficiently investigated so far. 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 a-SiC:H
It is called. ), its manufacturing method and existence are “Ph1l.

Mag, Vol. 35” (1978), etc., and its characteristics include high heat resistance and surface hardness;
a-3i: High dark resistivity (10” to 1
It is known that the optical energy gap changes over a range of 1.6 to 2.8 eV depending on the amount of carbon. However, there is a drawback that the band gear expands due to the inclusion of carbon, resulting in poor long wavelength sensitivity.

An electrophotographic photoreceptor combining such a-3iC:H and a-3t:H has been proposed, for example, in Japanese Patent Laid-Open No. 127083/1983. According to this, a-3isH
The layer is a charge generation (photoconductive) layer, and below this charge generation layer is a
-3iC:H layer is provided, the upper layer a-3i:H obtains photosensitivity in a wide wavelength range, and the lower layer a-5iC:H layer forms a heterojunction with a-St:HN; more charged Efforts are being made to improve the potential. However, the dark decay of the a-3i:H layer cannot be sufficiently prevented, and the charging potential is still insufficient to be practical.
The presence of the sH layer results in poor chemical stability, mechanical strength, heat resistance, etc.

On the other hand, JP-A-57-17952 discloses a-3i:
A first a-5iC:H layer is formed as a surface modification layer on the charge generation layer made of H, and a second a-5iC:H layer is formed on the back surface (support electrode side).
a-5iC:H layer is formed.

In addition, as related to this known technology,
As seen in Japanese Patent No. 23543, a gradient layer (a-S i , -XCx:H) is provided between the charge generation layer and the first and second a-5iC:HFi, and the gradient layer In a-5t:H side, set X=O, a-3i
A photoreceptor in which X=0.5 on the CsH layer side is known.

However, when the present inventor conducted a study on the above-mentioned known photoreceptor, it was found that the effect of providing the surface modification layer is not so pronounced, especially in continuous repeated use. That is, during continuous running of 200,000 to 300,000 times, the a-3iC layer on the surface is mechanically damaged after about 70,000 to 80,000 times, and this causes white streaks and white spots as image defects, resulting in poor rigidity. Not enough. Furthermore, light resistance fatigue occurs during repeated use, image blurring occurs, and the electrical and optical characteristics are not always stable, and the effects of the use environment (temperature, humidity) cannot be ignored. Furthermore, it is necessary to further improve the adhesion between the surface modified layer and the charge generation layer.

C.9 Purpose of the Invention The purpose of the present invention is to provide excellent adhesiveness between the surface number f layer and the charge generation layer, strong resistance to mechanical damage, and excellent rigidity resistance.
Stable image quality without image blurring is obtained, there is little optical fatigue during repeated use (and the residual potential is low), and the characteristics are compatible with the usage environment (
The purpose of the present invention is to provide a photoreceptor that is stable regardless of temperature and humidity.

20 Structure of the invention and its effects, that is, the present invention provides a charge transport layer made of amorphous hydrogenated and/or fluorinated silicon containing carbon atoms;
A charge generation layer made of amorphous hydrogenated and/or fluorinated silicon, an intermediate layer made of amorphous hydrogenated and/or fluorinated silicon containing at least carbon atoms and oxygen atoms, and carbon atoms and oxygen atoms. At least 50 atomic% of carbon atoms in
(However, the total number of silicon atoms and carbon and/or oxygen atoms is 100 atomic%.)
Amorphous hydrogenated and/or fluorinated silicon containing surface modified layers are sequentially stacked, and the carbon atom content or the total content of carbon atoms and oxygen atoms in the intermediate layer is the same as the surface modified layer. This relates to a photoreceptor in which the number of layers is smaller than that of the quality layer and continuously increases from the charge generation layer side to the surface modification layer side.

According to the present invention, the surface modified layer has at least a carbon atom content fx of carbon and oxygen of X > 50 atomic%.
(hereinafter simply referred to as %), it is resistant to mechanical damage and does not deteriorate image quality due to white streaks, etc.
, the printing durability is excellent. Further, if oxygen is included, the charging ability is improved, the film strength is also increased, and image quality can be stabilized. In order to fully exhibit the effect of this surface modification layer, 50%〈X590%, furthermore 55%≦X≦
It is desirable to set it to 70%. Furthermore, in the present invention,
Between the surface modified layer and the charge generation layer, the content of carbon atoms or the total content of carbon and oxygen is lower than that of the surface modified layer, and these contents increase from the charge generation layer side to the surface modified layer side. Since the intermediate layer is provided, the adhesion between the surface modified layer and the charge generation layer is improved.

The content of carbon atoms and/or oxygen atoms in this intermediate layer is desirably 0%≦y≦90%, particularly 40%≦y≦50%.

In addition, since the surface modification layer and intermediate layer are provided on the charge generation layer, in addition to the above, it has excellent resistance to light fatigue during repeated use, and there is no image fading, and electrical and optical properties are always stable. It has been confirmed that the product does not change and is not affected by the environment in which it is used.

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

FIG. 1 shows an a-3i electrophotographic photoreceptor 3 according to this embodiment.
9. This photoreceptor 39 is mounted on a drum-shaped conductive support substrate 41 made of Aβ or the like.
Charge blocking 1i44 consisting of C-containing a-3i:H heavily doped with group elements (e.g. boron or phosphorus) is optionally provided, and furthermore,
A charge transport layer 42 made of a-5i:H which is light-doped with an a-group element (for example, boron) to make it intrinsic and contains C, and a charge generation layer made of a-3i:H (without impurity doping or made intrinsic). 43, an intermediate layer 46 made of amorphous hydrogenated silicon (a S i +-y (CO)y:H) with a total content of carbon and oxygen atoms of 90% or less, and a total of carbon and oxygen atoms. Content is 50
% (for example, 60%) of amorphous hydrogenated silicon (a-si+-11(Co)X:H).

Charge generation 1143 has dark resistivity ρ.

The ratio of resistivity ρ when irradiated with light is sufficiently large as an electrophotographic photoreceptor, and the photosensitivity (particularly to light in the visible and infrared regions) is good.

The above-mentioned layer 45 is indispensable for modifying the surface of the photoreceptor and making the a-3i-based photoresistance 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 a-3i:H as its surface, it is easily affected by humidity, air, ozone atmosphere, etc., and the potential characteristics change significantly over time.

In addition, since the layer 45 has a high surface hardness, it has abrasion resistance during processes such as development, transfer, and cleaning, and also has good heat resistance, so a process that applies heat such as adhesive transfer can be applied. .

It is important to select the composition of the layer 45 in order to achieve the above-mentioned excellent effects comprehensively.

That is, carbon and oxygen atom content X;')<Si+C+0
= 100%, it is desirable that the value is 50 to 90%.

It is essential that the (C+O) content exceeds 50% for the reasons mentioned above, and also that the specific resistance will be the desired value and the optical energy gap will be approximately 2.5 eV or more, making it suitable for visible and infrared light. On the other hand, the irradiated light easily reaches the a-3i:Hllij (charge generation layer) 43 due to the so-called optically transparent window effect.

However, if the (C+O) content is less than 50%, disadvantages such as mechanical damage occur, and the specific resistance tends to fall below a desired value, and part of the light is absorbed by the surface layer 45, resulting in the photoreceptor's photosensitivity. tends to decrease. In addition, if the content exceeds 90%, the amount of carbon in the layer increases, and the semiconductor properties are likely to be lost, and the deposition rate when forming the a-3iCO:H film by the glow discharge method is likely to decrease. The content is preferably 90% or less.

Also, when the layer 45 contains only C among C and 0, 50% [C]≦90% (furthermore, 55%≦(C)5
70%) is good.

Further, it is preferable to continuously increase the carbon and/or oxygen content in the surface modified layer from the intermediate layer 46 side to the surface side.

In order to improve the charging ability, the surface modified layer 45 may have a high resistance. For this purpose, the surface modified layer may be made intrinsic.

When used with positive or negative charging, in order to facilitate the injection of electrons or holes from the intermediate layer into the surface-modified layer and to minimize the residual potential, the surface-modified layer may be of P or N type. good.

The amount of impurity doped in each case (at the time of glow discharge decomposition described later) may be as follows.

Intrinsicization: BtHh/s i H42-50 volume ppn
+P type: Bz)Ii/S i Ha 1-10
00 (preferably 50-500) Capacity ppm N type: P Hs/ S f Ha 1-100
0 (preferably 50 to 500) Capacity ppm It is also important to select the film thickness of the layer 45 within the range of 400 people≦t≦5000 people (particularly 400 people≦t<2000 people. If the thickness exceeds 5000 mm, the residual potential V becomes too high and the photosensitivity decreases, and the good characteristics of the a7si photoreceptor are likely to be lost.

Furthermore, if the film thickness is less than 400, charges will not be charged on the surface due to the tunnel effect, resulting in an increase in dark decay and a decrease in photosensitivity.

The intermediate layer 46 may be made intrinsic for the same reason as described above. In addition, in order to lower the residual potential, it is necessary to use a P or N intermediate layer to enable charge injection from the charge generation layer.
It can also be used as a mold. The doping amount for controlling the conductivity type may be the same as that for the surface modification layer.

The thickness of this intermediate layer is preferably 50 to 5,000 people, but if it exceeds 5,000 people, the same phenomenon as described above tends to occur, and if it is less than 50 people, the effect as an intermediate layer becomes poor.

Total content of carbon and oxygen in this intermediate layer 46 (C+0)
As shown in FIG. 2, can be increased continuously from the charge generation layer (0%) side to the surface modified layer (70%) side, for example, as shown by line a. Further, it may be changed like lines and C, or it may be changed in the area between these double-sided lines. C+0 on the charge generation layer side does not necessarily have to be zero.

Regarding the charge generation layer 43, in order to improve the charging ability,
The resistance of the charge generation layer may be increased.

For this purpose, the charge generation layer may be made intrinsic. For this purpose, BzHh/S i Ha = 1 to 20 capacitance pp
It is better to set it to m. It also improves sensitivity and lowers residual potential.
For the following reasons, it may be changed to P or N type as necessary, but in the case of P type, BzH6/S i H4 = 20 to 100 capacitance pptas, and in the case of N type, PH3/5iH4-1 to
It is assumed that the capacity is 100 ppst.

Further, the charge generation layer has a thickness of 1 to 10 μm, preferably 5 to 7 μm.
It is better to set it to m. 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.

Regarding the charge transport layer 42, in order to optimize charging ability and sensitivity, the charge transport layer may be made intrinsic, P-type, or N-type depending on the carbon content and charging polarity used.

Further, the thickness of the charge transport layer is preferably 10 to 30 μm.

Specifically, the charge transport layer 42 may be as follows.

SiC: Intrinsic BZHI, /S i H, 2 to 20 capacitance ppm P type B, Hh/S iH420 to 1000 llN type PH, /SiH41 to 1000 In addition, the composition of the charge transport layer is 5% <[01630%, Preferably, 10%≦(C)520%.

a-3iC:H When providing the charge blocking layer 44, 5% < 01630%, preferably 10%≦(C)5
It shall be 20%.

The conductivity type of the blocking layer may be P type (or even P' type) or N type (or N' type) depending on the sensitivity, charging ability, and charging polarity used. The doping amount is controlled according to the composition as follows.

SiC: Intrinsic BzHi/S i Ha 2-20 Capacity ppm
P type (P゛) B z Hb/ Si Ha 100-5000
(For positive charging) N type (N P H: I/S i Ha -100 to 1000)
(For negative charging) Also, the thickness of the blocking layer is 500~
The thickness is preferably 2 μm, but if it is less than 500, 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 charge generation 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, bronking layer 44, and charge transport layer 42. Also, as impurities for controlling the conductivity type of the blocking 844, in addition to boron, AI, Ga, In%
Group ma elements of the periodic table, such as Tjl, can be used. In addition to phosphorus, in order to make it N-type, As, Sb, etc.
Group elements can be used.

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 to a predetermined temperature from the inside. A cylindrical high frequency electrode 57 with a gas outlet 53 is arranged around and facing the substrate 41, and a reglow 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 supply source of SiH4 or a gaseous silicon compound, 63 is a supply source of a hydrocarbon gaff such as CH, 64' is a supply source of a nitrogen compound gas such as 1N2, and 65 is a supply source of a nitrogen compound gas such as 1N2.
66 is a carrier gas supply source such as Ar, 67 is an impurity gas (for example, BzH&) supply source, and 68 is each flow meter. In this glow discharge device, first, a support such as A
7! After cleaning the surface of the substrate 41, the substrate 41 is placed in a vacuum chamber 52, the gas pressure in the vacuum chamber 52 is adjusted to 10-' Torr, and the air is evacuated. C. (preferably 150 to 300 C.). Then, using a high purity inert gas as a carrier gas, Si Ha or a gaseous silicon compound, C
Ha, O□, etc. are appropriately introduced into the vacuum chamber 52, for example, 0
．． A high frequency voltage (for example, 13.56 MHz) is applied by a high frequency power supply 56 under a reaction pressure of 0.01 to 10 Torr. This allows each of the reaction gases to be transferred between the electrode 57 and the substrate 41.
P-type a-3iC:H,P-
Type a-3iC:H, a-3t:H, a-3iCO:H,
a-3iCO:H as above 1144.42.43.46
．． 45 (i.e., eg, corresponding to the example of FIG. 1).

In the above manufacturing method, the support temperature is set at 100 to 350°C in the step of forming the a-3t layer on the support, so the film quality (especially electrical properties) of the photoreceptor can be improved. .

In addition, when forming each layer of the above a-3i photoreceptor,
In order to compensate for dangling bonds, fluorine is introduced in the form of SiF4, etc., instead of or in combination with H, and a-3i:F, a-Si:H:F, a-3i:F, a-Si:H:F, a-
3iCO:F, a-3iCO:H:F, a-
3iC:FSa-3iC:H:F can also be used. 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 methods such as sputtering method, ion blating method, and evaporation of S'i under the introduction of activated or ionized hydrogen in a hydrogen discharge tube. (In particular, the method of
The above photoreceptor can also be manufactured by the method of No. 52455).

Hereinafter, the present invention will be described with reference to specific examples.

By glow discharge decomposition method, the first
An electrophotographic photoreceptor having the structure shown in the figure was manufactured.

That is, first, after cleaning the surface of a support, for example, a drum-shaped AJ substrate 41 having a smooth surface, it is placed in a vacuum chamber 52 shown in FIG.
Torr, and exhaust the air, and keep the substrate 41 at a predetermined temperature, particularly 100 to 350°C (preferably 150 to 350°C).
Heat and maintain at 300°C. Next, high-purity Ar gas was introduced as a carrier gas, high-frequency power with a frequency of 13.56 MHz was applied under a back pressure of 0.5 Torr, and preliminary discharge was performed for 10 minutes. Then, S i H
4 and BzHb was introduced, and the flow rate ratio was 1.
: 1 : 1 : (1,5Xl0-') of (Ar
+S i Ha + CHa + BzHi ) By glow discharge decomposition of the mixed gas, the P-type a-SiC:H layer 44 and the a-3iC:H charge transport layer 42, which play a charge pronking function, are heated at 6 pm/hr ( 7) Films were sequentially formed to a predetermined thickness at a deposition rate. Subsequently, the supply of B z Hb and CH was stopped, and S i H4 was decomposed by discharge to form an a-3i:H layer 43 with a thickness of 5 μm. Subsequently, glow discharge decomposition is performed by changing the flow rate ratio to form an a-3i C0:H intermediate layer 46 in which the amount of CO is continuously changed, and a
-3iCO:H surface protective layer 45 was further provided, and the electrophotographic photoreceptor was charged.

The structure of the photoreceptor thus produced was summarized as follows. .

(3) a-3t: H charge generation N (film thickness = 5 μm) (4)
a - S i C: H charge transport layer (5) a
-S i C: H charge blocking layer (6), support Al cylinder (mirror polished finish) Next, various tests were conducted using each of the above photoreceptors as follows.

■ As shown in Figure 4, the 0,
A load W is applied to the 3R diamond needle 70, and the photoreceptor is moved by the motor 71.
Rotate it with and scratch it. Next, the electrophotographic copying machine U-
An image is produced using a modified B ix 1600 (manufactured by Konishiroku Photo Industry Co., Ltd.), and the scratch strength (g) of the photoreceptor is determined by the load at which white streaks appear on the image.

After acclimatizing the photoconductor in a modified electrophotographic copying machine U-Bix 4500 (manufactured by Konishiroku Photo Industry Co., Ltd.) for 24 hours in an environment with a temperature of 33° C. and a relative humidity of 80%, the developer, paper,
After 1000 copies were made without contact with play and do, images were output and the degree of image blurring was determined based on the following criteria.

◎There is no image flow at all, and the reproducibility of 5.5 point English letters and fine lines is excellent.

○: 5.5 point alphabetic characters are slightly thicker.

△: 5.5 point letters are crushed and difficult to read.

X: 5.5 points of unreadable letters.

Potential measurement using a modified U-B ix 2500,
Static neutralizing light with a peak at 400 nm 301 ux-sec
The surface potential of the photoreceptor that remains even after irradiation.

It was measured with a 360 SX type electrometer (manufactured by Trek) using a modified U-Bix 2500 machine (manufactured by Konishiroku Photo Industry Co., Ltd.) with a photoconductor inflow current of 200 μA and no exposure. Surface potential just before development.

half' El/2 (j! ux-sec) Using the above device, the long wavelength component of 620 nm or more of the image exposure wavelength was sharply cut using a guichroic mirror (manufactured by Koshinko Co., Ltd.), and the surface potential was adjusted from 500 V. The amount of exposure required to reduce the voltage by half to 250V.

(The exposure amount was measured with a 550-1 light meter (manufactured by ECandG)) The image quality was evaluated as follows.

Image quality ◎: The image density is sufficiently high, the resolution and gradation are good, the image is clear and there are no white lines or white spots, that is, the image is extremely good.

○: Good image.

△: Can be used for practical purposes.

×: Impossible to use for practical purposes.

The results are summarized in Figure 5. These results show that if a photoreceptor is prepared according to the present invention, a photoreceptor with excellent performance for electrophotography can be obtained.

[Brief explanation of drawings]

1 to 5 show examples of the present invention.
Figure 3 is a schematic cross-sectional view of a glow discharge device, Figure 4 is a schematic diagram of a scratch strength tester, Figure 5 is a table showing the characteristics of each photoreceptor, Figure 6 is a conventional 1 is a schematic cross-sectional view of an electrophotographic copying machine. In addition, in the reference numerals shown in the drawings, 39-1--------------a-3t-based ill-sensitivity 4
1------------ Support (substrate) 42
−・−1−−−−・−・−・Charge transport layer 43−−−−
−−−−・−・−Charge generation layer 44−−−−−−−・−
--11 Charge profking layer 45...---1---
−・−・Surface modified layer 46−−−−−−−−−−−−・
It is the middle class. Agent Patent Attorney Hiroshi Aisaka Figure 4

Claims (1)

[Claims] 1. A charge transport layer made of amorphous hydrogenated and/or fluorinated silicon containing carbon atoms, a charge generation layer made of amorphous hydrogenated and/or fluorinated silicon, and at least carbon atoms among carbon atoms and oxygen atoms. an intermediate layer consisting of amorphous hydrogenated and/or fluorinated silicon containing at least 50 atomic% of carbon atoms and oxygen atoms (provided that the sum of silicon atoms and carbon and/or oxygen atoms (The number of atoms is 100 atomic%.) Surface modified layers made of amorphous hydrogenated and/or fluorinated silicon are laminated in sequence, and the carbon atom content of the intermediate layer or the ratio of carbon atoms and oxygen atoms is A photoreceptor in which the total content is less than that of the surface modified layer and increases continuously from the charge generation layer side to the surface modified layer side.