JP2595536B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used for an electrophotographic copying machine, an optical printer and the like.

Conventional technology 10 to 40 atm as photoconductor in electrophotographic photoreceptor
% Of hydrogen as a modifier to reduce the localized state density (hereinafter referred to as a-Si: H) has been noticed and used because of its high photosensitivity, pollution-free properties, and high hardness. ing.

However, there are still many problems to be solved in the electrophotographic photosensitive member composed of a-Si: H.

For example, as a first problem, a-Si: H has a dielectric constant as large as about 11 as compared with other photoconductor materials such as organic optical semiconductor (hereinafter referred to as OPC) or selenium (Se) (OPC: (Approximately 3, Se: approximately 6) Since the capacitance is large, a very large charging current is required when the surface is charged.

In addition, to obtain a practical surface potential (up to 400 V), the charge density of the surface charge is high, and a large amount of light energy is required to remove the charge with light. Therefore, it can be said that the actual light sensitivity is sufficiently high. Absent.

Further, as a second problem, in a plasma CVD method using a silane (hereinafter referred to as SiH ₄ ) gas as a source gas, which is most often used in forming an a-Si: H film, a deposition rate is as low as 10 μm / h or less, and a silane gas is used. Is also expensive, so it is difficult to reduce the manufacturing cost.

The third problem is that the film thickness is often less than 30 μm, and the charging electric field strength is about 30 V / μm.
Since a practical surface potential is used at a lower potential of 500 V or less than 800 V of the Se photoreceptor, there is a problem that a copy with a sufficient image density cannot be obtained with a normal two-component developer.

As means for solving such problems, Japanese Patent Laid-Open No.
No. 143645 discloses a configuration of a function-separated type photoconductor using an organic semiconductor material.

Problems to be Solved by the Invention When a photoconductive layer using this organic semiconductor material is used as an image forming material, an improvement in the charging potential due to a decrease in the dielectric constant can be expected, but since the organic semiconductor material has a small hardness, Si is used. The feature as a long-life photoreceptor having high hardness possessed by an amorphous photoconductive film containing the same cannot be utilized. In addition, temperature on conventional organic semiconductors
In order to form a high-quality a-Si: H film at 150 ° C. or higher, a good electrophotographic photosensitive member cannot be obtained because of poor heat resistance. Alternatively, heat treatment of polyacrylonitrile (PAN) having heat resistance has also been proposed, but since sufficient carrier mobility and carrier lifetime have not been obtained,
There was a problem that the residual potential was high and the sensitivity was not sufficient.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a photographic photoreceptor having a high residual potential and sufficient sensitivity.

Means for Solving the Problems In order to achieve the above object, the photographic photoreceptor of the present invention comprises:
It has a photoconductive layer that generates carriers that can move by photoexcitation, and a charge transfer layer formed of poly (P-phenylenevinylene) or polyphenylene sulfide having a crystallinity of 10 to 70%.

When the charge transfer layer is formed of poly (P-phenylene vinylene) or polyphenylene sulfide, if the crystallinity is too high, that is, if it exceeds 70%,
The resistance value is lowered, the charge retention ability in the dark required for an electrophotographic photoreceptor is lowered, and the mechanical strength is reduced, so that the film forming property is remarkably reduced. Further, those having a crystallinity lower than 10% have a sufficient resistance value, but the trap density increases, and the injected charge is not efficiently transported. When the charge transfer layer is formed of poly (P-phenylenevinylene) or polyphenylene sulfide, the crystallinity of the charge transfer layer is set to 10 to 70%, so that the electrophotographic photoreceptor having a small residual potential, a high sensitivity and a large charge potential. Is obtained.

Embodiment FIG. 1 schematically shows a cross section of an embodiment of the most basic electrophotographic photosensitive member according to the present invention.

The electrophotographic photoreceptor shown in FIG. 1 has a charge transfer layer 2 composed of a polymer layer having a ring structure and a photoconductive layer 3 on a support 1.
The photoconductive layer 3 has a free surface 4 on the one hand.

In the present invention, an amorphous layer containing silicon having high hardness is used as the photoconductive layer 3, and the photoconductive layer 3 is made of a-S
i (: H: X), a-Si _1-y C _y (: H: X) (O <y <1), a-Si
_1-y O _y (: H: X) (O <y <1), a-Si _1-y N _y (: H: X) (O
<Y <1), a-Si _1-z Ge _z (: H: X) (O <z <1), a-
(Si _1-z Ge _z ) _1-y N _y (: H: X) (O <y, z <1), a− (Si
_1-z Ge _z ) _1-y O _y (: H: X) (O <y, z <1) or a-
It consists of a single layer of (Si _1-z Ge _z ) _1-y C _y (: H: X) (O <y, z <1) or a laminate of these. Further, it is also possible to use a case where y is continuously changed.

At this time, the thickness of the charge transfer layer is 5 to 50 μm, preferably 10 μm.
The thickness of the photoconductive layer may be 0.5-10 μm, preferably 1-5 μm.

In the present invention, in order to further improve the electrophotographic characteristics, in FIG. 1, between the support 1 and the charge transfer layer 2, carriers injected from the support 1 into the charge transfer layer 2 are effectively blocked. Therefore, a barrier layer may be provided.

As a material for forming the barrier layer, Al ₂ O ₃ , BaO, BaO ₂ , Be
O, Bi ₂ O ₃ , CaO, CeO ₂ , Ce ₂ O ₃ , La ₂ O ₃ , Dy ₂ O ₃ , Lu ₂ O ₃ , Cr ₂ O ₃ , Cu
O, Cu ₂ O, FeO, PbO, MgO, SrO, Ta ₂ O ₃ , ThO ₂ , ZrO ₂ , HfO ₂ , TiO ₂ , T
Metal oxides such as iO, SiO ₂ , GeO ₂ , SiO, GeO, or TiN, AlN,
Metal nitrides such as SnN, NbN, TaN, and GaN; metal carbides such as WC, SnC, and TiC; insulators such as SiC, SiN, GeC, GeN, BC, and BN; polyimide, polyamideimide, and polyacrylonitrile Organic compounds are used.

Further, a surface coating layer may be formed on the free surface 4 in order to improve the cleaning property, the wear resistance or the corona resistance. Materials suitable for the surface coating layer include Si _x O _1-x , Si _x C _1-x , Si _x N _1-x , Ge _x O _1-x , Ge _x C _1-x , Ge _x N
_1-x , B _x N _1-x , B _x C _1-x , Al _x N _1-x (O < _x <1), and inorganic substances such as a layer containing hydrogen or halogen therein.

For producing a-Si (: H: X), which is a photoconductive layer containing silicon, SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , SiF ₄ , SiCl ₄ , SiHF ₃ , SiH
_{2 F 2, SiH 3 F,} SiHCl 3, SiH 2 Cl 2, SiH 3 plasma CVD method using a source gas of Si atoms, such as Cl, or polycrystalline silicon as a target, Ar and H ₂ (more F ₂ or A reactive sputtering method in a mixed gas of (Cl ₂ may be mixed) is used. Also, a-Si _1-y C _y (: H: X) (O <y <1), a-Si
_1-y O _y (: H: X) (O <y <1), a-Si _1-y N _y (: H: X) (O
In preparing <y <1), CH ₄ , C ₂ H ₆ , C
_{3 H 8, C 4 H 18} , C 2 H 4, C 3 H 6, C 4 H 8, C 2 H 2, C 3 H 4, C 4 H 6, C 6 H 6 or the like hydrocarbons, CH ₃ Allyl halides such as F, CH ₃ Cl, CH ₃ I, C ₂ H ₅ Cl, C ₂ H ₅ Br, and CFC gases such as CClF ₃ , CF ₄ , CHF ₃ , C ₂ F ₆ , and C ₃ F ₈ ;
C ₆ H _6-m F _m (m = 1 to 6) C atom source gas such as benzene fluoride is mixed with silicon source gas used for plasma CVD, or Ar etc. is used for reactive sputtering. Used in combination with the sputtering gas. O ₂ , CO,
CO ₂ , NO, NO _{2 and the} like are used, and N ₂ , NH ₃ , NO and the like are mixed and used as a nitrogen source.

Also, when Ge is added to a-Si (: H: X), GeH ₄ , Ge ₂
H ₆ , Ge ₃ H ₈ , GeF ₄ , GeCl ₄ , GeHF ₃ , GeH ₂ F ₂ , GeH ₃ F, GeHCl ₃ , GeH ₂
A gas such as Cl ₂ , GeH ₃ Cl or the like can be mixed with the above-mentioned source gas of the Si atom to form by a plasma CVD method.

Further, in the present invention, the above-mentioned a-Si (: H: X), a-
Si _1-y C _y (: H: X) (O <y <1), a-Si _1-y O _y (: H: X)
(O <y <1), a-Si _1-y N _y (: H: X) (O <y <1),
Alternatively, conductivity can be controlled by adding impurities to these films to which Ge is added, and desired electrophotographic characteristics can be obtained. Examples of the p-type impurity imparting p-type conductivity include B, Al, Ga, In and the like belonging to Group III b of the periodic table, and B, Al, Ga is preferably used to impart n-type conductivity. As n-type impurities, N, P, A belonging to Group V b of the periodic table
There are s, Sb and the like, and P and As are preferably used.

Further, as a method for adding these impurities, field of the p-type impurity _{Iaido, B 2 H 6, B 4} H 10, B 5 H 9, B 5 H 11, B 6 H 12, B 6 H 14, BF
_{3, BCl 3, BBr 3,} AlCl 3, (CH 3) 3 Al, (C 2 H 5) 3 Al, (i-C 4 H
₉ ) ₃ Al, (CH ₃ ) ₃ Ga, (C ₂ H ₅ ) ₃ Ga, InCl ₃ , (C ₂ H ₅ ) ₃ In
In the case of an n-type impurity, N ₂ , NH ₃ , NO, N ₂ O, NO ₂ , PH ₃ , P ₂ H ₄ , P
H ₄ I, PF ₃ , PF ₅ , PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ , PI ₃ , AsH ₃ , AsF ₃ , AsCl
₃ , AsBr ₃ , SbH ₃ , SbF ₃ , SbF ₅ , SbCl ₃ , SbCl ₅ , or a gas obtained by diluting these gases with H ₂ , He, Ar In some cases, it may be used by mixing with the above-mentioned raw material gas such as C atom and Si atom to be used. In the reactive sputtering method, Ar or H ₂ or F ₂ , C
l ₂ may be mixed and used.

As the charge transfer layer 2 formed of a polymer substance,
Poly (P-phenylene vinylene) or polyphenylene sulfide is used. These crystallinities or the crystallinity after the heat treatment are 10 to 70%.

Hereinafter, embodiments of the present invention will be described.

Example 1 Poly (xylylene-α-diethylsulfolium bromide), one of polymer sulfonium salts, was coated on a mirror-polished aluminum substrate and formed into a film at 30 ° C. under reduced pressure to obtain a polymer layer. This polymer layer is placed in nitrogen gas for 20 minutes.
Heat treatment was performed at 0 to 400 ° C. for 1 to 15 hours. Thereby, at the same time as Br or (C ₂ H ₅ ) ₂ S of poly (xylylene-α-diethylsulfonium bromide) is dissociated, the degree of polymerization between these polymers is advanced and the length of the conjugated chain is increased. In addition, the optical bandgap was reduced and was initially transparent (2.7 eV) without absorption in the visible region, but an absorption peak appeared at about 430 nm and yellow (2.1 to 2.4 eV) poly (P- Phenylene vinylene) is obtained.

This poly (P-phenylenevinylene) has the following structure.

The measured crystallinity of this poly (P-phenylenevinylene) was about 10-70%.

A substrate formed with the above polymer layer as a charge transfer layer and having a thickness of 25 μm after heat treatment is arranged in a parallel plate type capacitively coupled plasma CVD apparatus having a 6-inch discharge electrode,
After evacuating the reaction vessel to 5 × 10 ^-6 Torr or less, the substrate is
Heated to 00 ° C. Next, 10-40 sccm of SiH ₄ was introduced, and the pressure was increased.
0.2 to 1.0 Torr, high frequency power 20 to 100 W, non-doped (non
-Doped) An a-Si: H layer is formed as a photoconductive layer in a thickness of 0.5 to 5 μm, SiH ₄ is introduced in an amount of 10 to 30 sccm, C ₂ H ₄ is introduced in an amount of 20 to 40 sccm, a pressure of 0.2 to 10 Torr, and a high frequency power of 50 to 150 W With Si _1-x C _x : H
(O <x <1) was formed as a surface coating layer in an amount of 0.08 to 0.3 μm to prepare an electrophotographic photosensitive member.

The electrophotographic photosensitive member thus obtained was corona-charged at +6.0 KV, and a surface potential of +2200 V was obtained. When exposed with white light, the residual potential was less than +50 V and the half-reduction potential exposure amount was 1 lux. _-Very high sensitivity of less than _sec was obtained. When the photoreceptor was charged to +900 V and exposed to white light, the half-reduction potential exposure was 0.2 lux.
・ Sensitivity is very high at less than _sec . This is called conventional a-Si:
The sensitivity is 3 times higher than when the photoreceptor composed of 20 μm of H is charged to + 400V and exposed with white light. When only visible light is re-exposed and compared, the sensitivity is 4 times or more. Was. Also, in charging at the same corona potential, a
This shows that a photosensitive member having high sensitivity can be obtained with a charging current that is as small as 4 times or more the charging potential as compared with -Si: H alone.

Further, oxygen is added to the a-Si: H photoconductive layer of 0.2 to 2 μm for 200 to 200 μm.
An electrophotographic photoreceptor having the same characteristics as described above was formed both when 3,000 ppm was added and when B was added in an amount of 0.5 to 5 ppm.

On the other hand, in the charge transfer layer having a crystallinity of less than 10%, the residual potential was increased and a sufficient image density was not obtained. On the other hand, when the crystallinity exceeds 70%, the mechanical strength of the film sample is reduced, the film is frequently peeled off during heating, and the film forming property is significantly reduced.

Example 2 A powder of polyphenylene sulfide (hereinafter referred to as PPS) was formed on an aluminum drum whose surface was polished by hot pressing at 300300 ° C. in an inert gas at 2020 μm, and then the surface was slightly polished to a mirror surface to form a charge transfer layer. PPS in this state
Is a slightly yellowish and nearly transparent film.

PPS was a polymer having X: S and n = 10 to 30 in the following structure.

The drum is further dried in air at 150-250 ° C for 0.1-5
Heat treatment is performed for a time. The resulting drum was brownish and had an optical bandgap of ~ 2.4 eV.

Using a sample prepared for X-ray measurement in the same manner as above, the crystallinity was measured.
Has a crystallinity of about 10-40%.

This was placed in a capacitively coupled plasma CVD apparatus having a cylindrical discharge electrode having a length of 45 cm and an inner diameter of 16 cmφ. After evacuation of the reaction vessel to 5 × 10 ⁻⁶ Torr or less, the aluminum drum was heated to 150 to 200 ° C. Heated. The SiH ₄ 50~150sccm, C ₂ H ₂
5~100ppm the 2～10Sccm, the B ₂ H ₆ to SiH _4, the pressure 0.2
A-Si _1-x C _x : H layer is formed at _{1 to 5} μm at 1.01.0 Torr and high frequency power of 100 to 250 W, and then C ₂ H ₂ is added to SiH ₄ for 20 to 50 μm.
The thickness increased to sccm, and an a-Si _1-x C _x layer of 0.05 to 0.5 μm was formed to obtain an electrophotographic photosensitive member. At this time, the optical band gap of the a-Si _1-x C _x : H layer is 1.7 to 1.9 eV, and the photoconductor is 670 nm L.
Mounted on an optical printer using ED as a light source, and +
Clear printing was confirmed at a surface potential of 500 to 800 V.

Also, a- (Si _1-z G G) obtained by adding Ge to a-Si _1-x C _x : H
e _z ) The sensitivity was further improved by using _1-x C _x : H.

In addition, although a sulfide polymer layer was used as the charge transfer layer,
Similar characteristics can be obtained with e or Te-modified polymers.

As a material to replace the a-Si _1-x C _x layer as a surface coating layer
When a-Ge _1-x C _x : H (O <x <1) of 0.1 to 0.5 μm was formed by a plasma CVD method and mounted on an optical printer in the same manner, the electrophotographic photosensitive member having this configuration showed heat resistance, It was found that it has excellent moisture resistance and has a printing durability of 500,000 sheets.

When the crystallinity of the charge transfer layer is less than 10%, the residual potential increases as in Example 1, and the mobility decreases.

Effect of the Invention The electrophotographic photoreceptor according to the present invention has a photoconductive layer that generates a movable carrier by photoexcitation, and a crystallinity of 10 to 70.
% Of poly (P-phenylenevinylene) or polyphenylene sulfide, so that a charge transport layer having a large resistance value in the dark and a large carrier mobility can be formed. Becomes

By the above synergistic effect, an electrophotographic photosensitive member having a small residual potential, a high sensitivity and a large charging potential can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electrophotographic photosensitive member according to one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Support, 2 ... Charge transfer layer, 3 ... Photoconductive layer, 4
…… free surface.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Koji Akiyama 1006 Kadoma Kadoma Matsushita Electric Industrial Co., Ltd. JP-A-62-187353 (JP, A)

Claims (4)

(57) [Claims] 1. A photoconductive layer that generates carriers that can move by photoexcitation, and a charge transfer layer that transports the carriers, wherein the charge transfer layer has a crystallinity of 10 to 70%.
An electrophotographic photoreceptor made of (phenylene vinylene) or polyphenylene sulfide. 2. The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer is an amorphous layer containing a modifying substance for reducing the density of localized states. 3. The charge transfer layer comprises arsenic fluoride (AsF ₅ ), sulfur oxide (SO ₃ ), antimony fluoride (Sb) as an electron acceptor.
F ₅ ), bromine (Br ₂ ), iodine (I ₂ ), or 7,7,8,8-
2. The electrophotographic photoreceptor according to claim 1, wherein said electrophotographic photoreceptor contains at least one of tetracyanoxinodimethane (TCNQ) in an amount of 0.01 to 0.4% by weight. 4. The electrophotographic photosensitive member according to claim 1, wherein the photoconductive layer contains at least one of hydrogen and a halogen element.