JPS61243459A - Photosensitive body - Google Patents

Abstract

PURPOSE:To reduce change of acceptance potential by forming an electrostatic charge blocking layer made of amorphous silicon carbide hydride and/or fluoride on a substrate, and laminating on this layer a charge transfer layer, a charge generating layer, a surface modified layer in succession. CONSTITUTION:The charge blocking layer 5 made of amorphous silicon carbide hydride and/or fluoride (a-SiC:H,F) doped with an element of group IIIa or Va of the periodic table, the charge transfer layer 2 made of a-SiC:H,F doped with an element of group IIIa, the charge generating layer 3 made of a-Si:H,F doped with an element of group IIIa, and further, the surface modified layer 4 made of a-SiN:H,F doped with an element of group IIIa are laminated on the substrate 1 in succession to form the photosensitive body. The use of the blocking layer made of a-SiC:H,F permits injection of charge to be prevented, acceptance potential to be held, and dark decay to be reduced.

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 Ss is
Photoreceptors doped with s T e SS h, etc., photoreceptors in which ZnO or CdS is dispersed in a resin binder, and the like 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 (hereinafter referred to as 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 incised, 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 H to St.

Such amorphous hydrogenated silicon (hereinafter referred to as a-3
It is called i:H. ) has a resistivity of 198 to 109 in the dark.
Ω-B, which is about 1/10,000 times lower than that of amorphous Se. Therefore, a photoreceptor made of a single layer of a-3i:H has a high dark decay rate of the surface potential and a low initial charging potential. There is a problem with this. However, on the other hand, when irradiated with light in the visible and infrared regions, the resistivity increases (decreases), so it has extremely excellent characteristics as a photosensitive layer of a photoreceptor.

In addition, photoreceptors with a-3i: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. , 0 For example, 1 has not been sufficiently studied so far.
It is known that batteries left unused for more than a month are affected by humidity and their receptive potential drops significantly. On the other hand, regarding amorphous silicon carbide (hereinafter referred to as a-3iC:H), its manufacturing method and existence are disclosed in “Ph11.Mag, Vol.
35'' (197B), etc., and its characteristics include high heat resistance and surface hardness, and high dark resistivity (10゛2 to 10'3 Ω-am) compared to a-5i:H.
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.

Electrophotographic photoreceptors in which such a-3iC:H and a-3i:H are combined are disclosed in, for example, JP-A-58-219559 and JP-A-58-2195605. No. 59-212840, No. 5
It is described in various publications such as No. 9-212842.

C. Purpose of the Invention The purpose of the present invention is to reduce changes in charging potential during repeated use, reduce dark decay and residual potential, improve photosensitivity,
An object of the present invention is to provide a photoreceptor, such as an electrophotographic photoreceptor, which has improved environmental resistance, stability over time, and durability.

D. Structure of the invention and its effects, namely: - The photoreceptor according to the invention includes (a) a charge generation layer made of amorphous hydrogenated and/or fluorinated silicon and doped with a group IIIa element of the periodic table; (b) a surface modification layer formed on the charge generation layer and made of amorphous hydrogenated and/or fluorinated silicon nitride and doped with a group IIIa element of the periodic table; (c) the charge generation layer; (d) a charge transport layer formed under the charge transport layer and made of amorphous hydrogenated and/or fluorinated silicon carbide and doped with an element of group IIIa of the periodic table; and a doped charge blocking layer.

The photoreceptor of the present invention is of a functionally separated type in which a charge generation layer and a charge transport layer are separated, and in particular, an amorphous hydrogenated and/or fluorinated silicon carbide layer is present as a blocking layer on the substrate side. It is possible to effectively prevent the injection of carriers from
Dark decay can be reduced. Further, since the charge transport layer is also formed of the same silicon carbide layer, the charge transport ability is improved, and the presence of the amorphous silicon nitride surface modification layer on the outermost surface improves durability, stability, etc.

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 The invention will now be illustrated in detail with reference to the drawings.

The photoreceptor according to the present invention includes, for example, as shown in FIG. doped a-3iC:H charge transport layer 2, doped a-3 of group IIIa element of the periodic table
A charge generation layer 3 made of 3t:H and an a-3iN:1 (surface modified layer 4) doped with a group IIIa element of the periodic table are laminated in sequence.

The a-3iC:H layer 5 greatly contributes to preventing the injection of carriers from the substrate 1 and maintaining a sufficient surface potential, and therefore has N-type conductivity due to the inclusion of a Va group element or a IIIa group element. It is important to exhibit P-type conductivity by containing . In addition, its thickness is 400 ~ 2 μm
It is desirable that

The a-3iC:H layer 2 mainly has potential retention and charge transport functions, and is preferably formed to have a thickness of 10 to 30 μm.

The charge generation layer 3 generates charge carriers in response to light irradiation, and preferably has a thickness of 1 to 10 μm. Furthermore, a-3iN:H4 improves the surface potential characteristics of this photoreceptor, maintains long-term electrical characteristics, maintains environmental resistance (prevents the effects of humidity, atmosphere, and chemical species generated by corona discharge), and improves the surface potential of the photoreceptor. It has the functions of improving printing durability due to its high hardness, improving heat resistance when using a photoreceptor, and improving thermal transferability (especially adhesive transferability), and acts as a surface modification layer. The thickness of this surface modified layer 4 is desirably made as thin as 400 to 5000 people.

What should be noted about this photoreceptor is that a-3iN/a
-3t:H/a-3iC stacked structure, a-3iC:H blocking layer is P-type or N-type by doping with group 1 [[a or Va of the periodic table]. Therefore, carrier (electron or hole) injection from the substrate side is effectively prevented during positive or negative charging. Moreover, in addition to this, a charge transport layer 2,
The fact that the charge generation layer 3 and the surface modification layer 4 are made intrinsic or have a high dark resistance by doping with Genraku from group IIIa of the periodic table greatly contributes to improving each electrostatic property as described later. are doing.

Furthermore, since the photoreceptor shown in Figure 1 has the above-mentioned laminated structure, it maintains a higher potential with a thinner film than the conventional Se photoreceptor, and is excellent against light in the visible and infrared regions. It is possible to provide an a-3i photoreceptor (for example, for electrophotography) which exhibits high sensitivity, good heat resistance, stiffness resistance, and stable environmental resistance.

Next, an apparatus (glow discharge device W) that can be used to manufacture a photoreceptor according to the present invention will be described with reference to FIG.

In a vacuum chamber 62 of this device 61, a drum-shaped substrate 1 is set so as to be vertically rotatable, and a heater 65 can heat the substrate 1 from the inside to a predetermined temperature. A cylindrical high frequency power source 67 with a gas outlet 63 is arranged around and facing the substrate 1.
6 causes a glow discharge. In addition, 7 in the figure
2 is a source of SiH4 or gaseous silicon compound, 73
is 02 or a gaseous oxygen compound supply source, 74 is a hydrocarbon gas such as CH4 or a nitrogen compound gas supply source such as NH3, N2, etc., 75 is a carrier gas supply source such as Ar, and 76 is an impurity gas (for example, B2H6 or PIIIa) Source, 7
7 is each flow needle. In this glow discharge device, first, the surface of the support, for example, the AI substrate 1, is cleaned and then placed in a vacuum chamber 62, and the gas pressure in the vacuum chamber 62 is set to 10
-' Torr and exhaust the air, and keep the substrate 1 at a predetermined temperature, particularly 100 to 350°C (preferably 150°C).
Heat and maintain at a temperature of 0 to 300°C. Then, using a high purity inert gas as a carrier gas, SiH4 or a silicon compound on gas, B2H6 (or PH3), CH4 or N
2 is appropriately introduced into the vacuum chamber 62, for example, 0.01 to 10
A high frequency voltage (for example, 13.56 MHl) is applied by a high frequency power supply 66 under a reaction pressure of Torr. As a result, each of the above-mentioned reaction gases is decomposed by glow discharge between the electrode 67 and the substrate 1, and boron- or phosphorus-doped a-3iC:H,
Boron-doped a-3iC:H.

Boron doped aSl:Hs boron doped a-3tN:H is deposited successively (i.e. corresponding to the example of FIG. 1) on the substrate as layer 5.2.3.4 above.

Regarding the above a-3iNsH layer 4, it has been found that it is also important to select its nitrogen composition in order to exhibit the above-described effects. If the composition ratio is expressed as a-3ii XNX:H, especially 0.1≦X≦0.7 (3L +
When N = 100 atomic%, it is desirable that the nitrogen atom content is 10 atomic% to 70 atomic%. That is, if 0.1≦X, the optical energy gap will be approximately 2.3 eV or more, and it will be substantially photoconductive to visible and infrared light (where ρD is the resistivity in the dark and ρL is the The resistivity at the time of light irradiation is calculated as ρ0/
The smaller the ρL, the lower the photoconductivity), and most of the irradiated light reaches the a-3t:H layer (charge generation layer) 3 due to the so-called optically transparent window effect. Conversely, x<Q,
If X exceeds 0.7, most of the layer becomes nitrogen and semiconductor properties are lost. outside, a
-3iN:H film When formed by glow discharge method, the deposition rate is reduced, so it is preferable to set X≦0.7. The photosensitive layer 3
It is possible to efficiently inject charge carriers generated in response to light irradiation without creating a barrier. Therefore, this a-5iC:H layer 2 maintains a high surface potential at a practical level, efficiently and quickly transports the charge carriers generated in the a-St:H layer 3, and forms a photoreceptor with high sensitivity and no residual potential. - It has the function of When this a-3iC:H layer 2 is expressed as a-3i 1- x Cx : H, 0.05≦X≦0.3 (carbon atom content is 5 atoms
ic%~30a ton ic%: However, S i +
C-100 atomic%), preferably 0.1≦
It is desirable that X≦0.2, and a-3iC:H
The carbon content of charge blocking layer 5 is also the same as layer 2 < 5
~30 atomic%, preferably 10-20 atomic%
It is preferable to set it as ic%.

Both the a-SiC:H layer and the a-5iN:H layer described above must contain hydrogen, but if they do not contain hydrogen, the charge retention characteristics of the photoreceptor will not be practical. It is from. Therefore, the hydrogen content is 1 to 40a
tomic% (furthermore, 10 to 30 atoa+ic%). The hydrogen content in the charge generation layer 3 is essential to compensate for dangling bonds and improve high conductivity and charge retention, and is usually 1. ~4
0atoa+ic%, 3.5-20atoa+i
More preferably, it is c%.

When forming each layer by glow discharge decomposition in this way, it is necessary to appropriately select the flow rate ratio of diborane or phosphine gas and silicon compound (for example, monosilane). a
- When the flow rate ratio of PH3 (phosphine) and 5iH4 (monosilane) is changed when forming the 3iC:H layer 5, the PH
, PIIIa/
The flow rate ratio of S i H4 is preferably 1 to 1000 ppm by volume. In addition, in the case of P-type conversion by boron doping,
It is preferable to perform glow discharge decomposition with B2He/SiH4=20 to 5000 ppm in capacity. It is preferable that ρ0 of the charge blocking layer satisfies ρp≦10 7 Ω-value.

On the other hand, the amount of boron doping performed during the formation of layer 2.3.4 above needs to be appropriately selected in order to obtain the desired dark resistance value. 2 He/S i H4-1~20
It is desirable that the capacitance is ppm (ρD≧1012Ω−3), and in layer 3, B2H6/SiH+=0.1 to 10
Capacitance ppa+ (ρO≧1010Ω-am) In layer 4, BzHs/SiH+=1 to 1000 capacitance ppm (ρ
It is preferable that p≧10 Ω−Ca1).

However, the optimal range of the above-mentioned impurity doping amount depends on the N, C, and H contents of the layer, and therefore is not necessarily limited to the above-mentioned range.

In the example explained above, in order to compensate for dangling bonds, fluorine is introduced into a-3t instead of the above-mentioned H or in combination with H, and a-3i:
F% a-3i:H:FSa-3iC:FSa-3i
It can also be set as C:H:F. In this case, the amount of fluorine is preferably 0.01 to 20 atomic%, 0.5 to 10
Atomic% is more desirable.

Although the above manufacturing method is based on a glow discharge decomposition method, the photoreceptor can also be manufactured by a vapor deposition method, a sputtering method, an ion blating method, or the like. In addition to SiH4, the reaction gases used include Si 2 H6,
3i HF 3, SiF4 or its derivative gas, CH4
Other lower hydrocarbon gases such as C2H6 and C3He can be used. In addition to the above-mentioned boron and aluminum, other impurities to be doped include other elements of group N[A of the periodic table, such as gallium and indium, and other group Va elements of the periodic table, such as arsenic and antimony other than phosphorus. .

Next, an example in which the present invention is applied to an electrophotographic photoreceptor will be specifically described.

An electrophotographic photoreceptor having the structure shown in FIG. 1 was prepared on an Al support by a glow discharge decomposition method. First, a clean Al support with a smooth surface was placed in a reaction (vacuum) chamber of a glow discharge device. After evacuating the reaction tank to a high vacuum level of 10-6 Torr and heating the support to 200°C, high purity A
r gas was introduced, and high frequency power with a frequency of 13.56 MHz and a power density of 0.04 W/- was applied under a back pressure of 0.5 Torr to perform a preliminary discharge for 15 minutes. Next, a reaction gas consisting of SiH4 and CH4 was introduced and the flow rate ratio was 3:1:0.5 to 0.05 (Ar+Si
By glow discharge decomposition of H4+CH4) mixed gas and PH3 or BzIIIa gas, an a-3iC:H layer that prevents carrier injection and an a-3iCsH layer that plays a potential holding and charge transport function are deposited at a rate of 1000 people/ll1n. The film was formed at high speed. After evacuating the reaction tank, CH4
SiH4 and B were not supplied and Ar was used as a carrier gas.
z Hs release'l1 decomposed, boron doped a-S
After forming the t:H photosensitive layer, N2 is supplied, and (Ar+SiH++Nz) mixed gas and B2H6 at a flow rate ratio of 5:1:4 to 0.5 are decomposed by glow discharge to form a-3iN:H.
A surface modification layer was further provided to complete the electrophotographic photoreceptor.

The optical energy gap of this a-3iN:H surface modification layer is 2.5-2. It was OeV. Further, analysis revealed that the nitrogen composition was 40 to 60 atomic%.

Regarding such a photoreceptor, the composition of each layer was changed as shown in FIG. 3, and the following measurements were carried out.

Charged potential Vo (V): U-Old
Surface potential immediately before development measured with a 360SX type potential needle (manufactured by Torefuku Co., Ltd.) under conditions without μA1 exposure.

Half-reduced exposure amount E 1/2 (lux -5ec)
: Using the above device, sharply cut the long wavelength component of 620 nm or more of the image exposure wavelength using a guichroic mirror (manufactured by Kotai Kogaku Co., Ltd.), and the exposure necessary to halve the surface potential from 500 V to 250 V. amount. (The exposure amount is 55
Residual potential Vg (V): 500V using the above device
The surface potential after being charged to , and then irradiated with static eliminating light having a peak at 400 nm for 301 ux-sec.

200,000 copies live action: U-Bix 2500 modified machine (
(manufactured by Konishiroku Photo Industry ■), and the image quality was evaluated 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.

O image is good.

8. Can be used for practical purposes.

×　Image cannot be used for practical purposes.

As shown in FIG. 3, the photoreceptor according to the present invention had a small amount of half-decreased exposure during exposure (low residual potential), and very good charging/exposure repetition characteristics.

[Brief explanation of drawings]

The drawings illustrate the present invention, in which FIG. 1 is a cross-sectional view of a portion of an electrophotographic photoreceptor, FIG. 2 is a schematic cross-sectional view of a glow discharge apparatus for manufacturing the photoreceptor, and FIG. 3 is an electrophotographic photoreceptor. FIG. 3 is a diagram showing a comparison of characteristics of photoreceptors. In addition, in the symbols shown in the drawings, 1...
...Support (substrate) 2 ..... a-3iC doped with impurities
:H charge transport layer 3...Impurity doped a-3i:H charge generation layer 4...Impurity doped a-3iN:H surface modified layer 5... . . . Impurity-doped a-3iC:H charge profking layer.

Claims (1)

[Claims] 1. (a) a charge generation layer made of amorphous hydrogenated and/or fluorinated silicon and doped with an element of group IIIa of the periodic table; (b) on this charge generation layer; (c) a surface modification layer formed under the charge generation layer and comprising amorphous hydrogenated and/or fluorinated silicon nitride and doped with a Group IIIa element of the periodic table; (d) a charge transport layer formed under the charge transport layer and made of amorphous hydrogenated and/or fluorinated silicon carbide; and a charge blocking layer doped with a Group IIIa or Group Va element of the periodic table.