JPH0797226B2 - Electrophotographic photoreceptor and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used in electrophotographic copying machines, optical printers and the like.

2. Description of the Related Art Se and organic photo-semiconductors (hereinafter referred to as OPCs) are used as photoconductors in electrophotographic photoreceptors, but recently, they contain 10 to 40 atm% hydrogen as a modifier that reduces the localized density of states. Amorphous silicon (hereinafter referred to as a-Si: H) has been noted and used because of its high photosensitivity, pollution-free property, and high hardness.

However, the electrophotographic photosensitive member composed of a-Si: H has many problems. First, a-Si: H has a dielectric constant of about 11, which is larger than about 3 for OPC and about 6 for Se, and therefore has a large capacitance and requires a large charging current in the charging process of the electrophotographic process. Becomes Secondly, the surface charge density is high at a practical surface potential (up to 400 V) for obtaining a sufficient black density in an image, and the amount of light required to photo-eliminate the charges is large. Therefore, the feature of high quantum efficiency in carrier generation has not been utilized. Third, the plasma CVD method using a silane gas (hereinafter referred to as SiH ₄ ) used as a source gas for forming an a-Si: H film has a low deposition rate of 10 μm / h or less and SiH ₄ gas is also expensive. Therefore, it is difficult to reduce the manufacturing cost.

As means for solving these problems, JP-A-54-143645
A function-separated type photoreceptor using an organic semiconductor material is proposed in JP-A-56-24355, and a function-separated type photoreceptor using an inorganic semiconductor material is proposed in JP-A-56-24355. Also we
A function-separated type photoreceptor in which a layer containing amorphous carbon as a main component is used as a charge transport layer and a charge generation layer is made of amorphous silicon is proposed.

However, when the first organic semiconductor is used, although the charging current decreases due to the decrease in the dielectric constant, the mobility is generally low and the carrier life is short, so that the photosensitivity deteriorates.
In addition, since the hardness is low, the high hardness of the a-Si: H film makes it impossible to take advantage of its characteristics as a long-life photoreceptor. In the second inorganic semiconductor, since a chalcogen material that is easily polycrystallized or SiC having a large dielectric constant is used, it is not possible to expect a decrease in temperature characteristics or a significant improvement in photosensitivity. When the third amorphous carbon is used as the charge transport layer, the dielectric constant is small, which leads to a decrease in charging current, a decrease in surface charge density and improvement in characteristics. It imposes a major constraint on speed. When the plasma CVD method is used for forming the amorphous carbon film, inexpensive gas such as CH ₄ , C ₂ H ₄ , C ₂ H ₂ and C ₆ H ₆ can be used as a source gas, Maximum film deposition rate of 10 μ / h
However, there remains a difficulty in drastically reducing the manufacturing cost of the photoconductor.

Problems to be Solved by the Invention In a function-separated electrophotographic photoreceptor, in order to obtain a highly sensitive photoreceptor, it is necessary to realize a charge transport layer having a smaller dielectric constant or a larger mobility. is there.

The dielectric constant of the charge transport layer is 3 to 6 for amorphous carbon and about 3 for OPC. It is difficult to achieve a dielectric constant lower than this, and there is little merit.

On the other hand, the condition imposed on the mobility of the charge transport layer is μτV> d ² , where (μ mobility, τ is carrier lifetime, d is the thickness of the charge transport layer, and V is the charge transport layer. When μ is large, the time for carriers to run through the film thickness of the charge transport layer is T _r = d ² / μV. A charge transport layer with higher mobility has a faster process speed. The optical printer can be realized.

Amorphous carbon, which has a small dielectric constant, satisfies the condition that it can travel a distance equivalent to the film thickness of the charge transport layer as the μτ product that represents the travel distance of carriers, and it must reduce the surface potential with a low light intensity. However, since μ is small and it takes time for carriers injected into the charge transport layer to run through the layer,
Puts a big limitation on the process speed.

Means for Solving the Problems In a function-separated electrophotographic photosensitive member including a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transports the carriers, the charge transport layer has P-phenylene,
A linear compound polymer layer having a VIb group element in the para position, which contains at least one of S, Se, and Te as a VIb group element, and further contains an O atom separately from the VIb group. Included outside the chain.

Action The movement of carriers in a polymer is carried out by hopping conduction between electron orbits along the main chain direction of the polymer, and the mobility of the carrier increases as the overlap between adjacent orbits increases, To increase. In a polymer having a structure having P-phenylene in the main chain direction and a VIb group element in the para position, when the VIb group element is in a neutral state, adjacent P-phenylenes have spatial π electron orbits. , Is in a direct coordination state and has low mobility. However, when the VIb group element is positively charged by the added O atom and ionized, P
-The spatial twist of phenylene is eliminated, the π electron orbits are arranged in the same plane, and the mobility is improved as the hopping probability increases.

Example FIG. 1 schematically shows a cross section of an example of a basic electrophotographic photosensitive member according to the present invention.

The electrophotographic photosensitive member shown in the figure has a charge transfer layer 2 composed of a polymer layer and a photoconductive layer 3 on a support 1 as an electrophotographic photosensitive member, and the photoconductive layer 3 is a free surface on the one hand. Have four.

In the present invention, an amorphous material containing silicon having a high hardness is used as the photoconductive layer, and for example, a-Si (: H: X), a
-Si _1-y C _y (: H: X) (0 <y <1), a-Si _1-y O _y (: H:
X) (0 <y <1), a-Si _1-y N _y (: H: X) (0 <y <
1), a-Si _1-z Ge _z (: H: X) (0 <z <1), a- (Si
_1-z Ge _z ) _1-y N _y (: H: X) (0 <y, z <1), a- (Si _1-z G
e _z ) _1-y O _y (: H: X) (0 <y, z <1), or a- (Si _1-z G
e _z ) _1-y C _y (: H: X) (0 <y, z <1), or a single layer of these layers. It can also be used when y is continuously changed.

At this time, the thickness of the charge transfer layer is 5 to 50 μm, preferably 10 to
25 μm, and the thickness of the photoconductive layer is 0.5 to 10 μm, preferably 1
It may be set to ˜5 μm.

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

As the 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 , C
r ₂ O ₃ , CuO, Cu ₂ O, FeO, PbO, MgO, SrO, Ta ₂ O ₃ , ThO ₂ ,
ZrO ₂ , HfO ₂ , TiO ₂ , TiO, SiO ₂ , GeO ₂ , SiO, GeO or other metal oxides or TiN, AlN, SnN, NbN, TaN, GaN or other metal nitrides, or WC, SnC, TiC, Carbide such as Si or Si
Insulators such as C, SiN, GeC, GeN, BC, and BN, and heat-resistant organic compounds such as polyimide, polyamideimide, and polyacrylonitrile are used.

Further, in order to improve the cleaning property, abrasion resistance or corona resistance, a surface coating layer is formed on the free surface 4 in the figure. Suitable materials 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 (0 <x <1), inorganic substances such as carbon and layers containing hydrogen or halogen therein .

For forming 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 , Si is used.
A plasma CVD method using a source gas of Si atoms such as H ₂ F ₂ , SiH ₃ F, SiHCl ₃ , SiH ₂ Cl ₂ , and SiH ₃ Cl, or using polycrystalline silicon as a target, Ar and H ₂ (further F ₂ Alternatively, a reactive sputtering method in a mixed gas of Cl ₂ may be used) is used. In addition, a-Si _1-y C _y (: H: X) (0 <y <1), a
-Si _1-y O _y (: H: X) (0 <y <1), a-Si _1-y N _y (: H:
X) (0 <y <1) is prepared by further adding C as a carbon source.
_{H 4, C 2 H 6,} C 3 H 8, C 4 H 10, C 2 H 4, C 3 H 6, C 4 H 8, C 2 H 2, C 3 H
Hydrocarbons such as ₄ , C ₄ H ₆ , C ₆ H _6, etc., CH ₃ F, CH ₃ CI, CH ₃ I, C ₂ H ₅
Allyl halides such as Cl, C ₂ H ₅ Br, CClF ₃ , CF ₄ , CH
_{F 3, C 2 F 6,} C 3 chlorofluorocarbon such as _{F 8, C 6 H 6-} m F m (m-1~
6) C atom source gas such as fluorinated benzene is plasma CV
Mixed with silicon source gas used in method D, or
The reactive sputtering method is used by mixing with a sputtering gas such as Ar. Also, as the oxygen source, O ₂ , CO, CO ₂ , NO, NO _2, etc.,
As the nitrogen source, N ₂ , NH ₃ , NO or the like is mixed and used.

In addition, 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
A gas such as ₃ , GeH ₂ Cl ₂ or GeH ₃ Cl may be mixed with the above Si atom source gas to form the plasma CVD method.
Further, in the present invention, the above-mentioned a-Si (: H: X), a-Si
_1-y C _y (: H: X) (0 <y <1), a-Si _1-y O _y (: H: X)
(0 <y <1), a-Si _1-y N _y (: H: X) (0 <y <
1), or by adding impurities to these films in which Ge is added, the conductivity can be controlled and desired electrophotographic characteristics can be obtained. P-type impurities that give p-type conductivity include B, Al, and G belonging to Group IIIb of the periodic table.
a, In, etc., preferably B, Al, or Ga are used, and as the n-type impurity imparting n-type conductivity, Group V group b of the periodic table is used.
There are N, P, As, Sb, etc., which are preferably used.

As a method for adding these impurities, in the case of p-type impurities, 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 , B
_{Cl 3, BBr 3, AlCl 3} , (CH 3) 3 Al, (C 2 H 5) 3 Al, (iC 4 H 9) 3 A
_{l, (CH 3) 3 Ga} , (C 2 H 5) 3 Ga, InCl 3, a _{(C 2 H 5) 2 In} , the case of n-type _{impurity, N 2, NH 3, NO} , N 2 O, NO ₂ , PH ₃ , P ₂ H ₄ , PH
₄ I, PF ₃ , PF ₅ , PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ , PI ₃ , AsH ₃ , A
sF ₃ , AsCl ₃ , AsBr ₃ , SbH ₃ , SbF ₃ , SbF ₅ , SbCl ₃ , SbCl ₅
In the plasma CVD method, a gas obtained by diluting these gases with H ₂ , He, or Ar is mixed with the above-mentioned raw material gas such as C atom or Si atom used in forming each film in the plasma CVD method. In the reactive sputtering method, Ar, H _2, F ₂ , or Cl ₂ may be mixed and used. Examples will be described below.

Example 1 A film-shaped PPS (poly-p-phenylene sulfide) having S as a VI group was attached on a mirror-polished aluminum substrate, and a fluororesin sheet was wound from the upper side of the film and heated in a heat treatment furnace to form a PPS film. Was fused on an aluminum substrate. The heating temperature is PP
S is 290 ° C., which is higher than the melting temperature of 285 ° C., and the heating atmosphere is the atmosphere. After taking out the substrate from the heat treatment furnace, the fluororesin sheet was removed, the substrate was placed again in the heat treatment furnace, and heat treatment was performed in an oxygen atmosphere. The heating temperature is
Controlled within the range of 285 ℃ -350 ℃, heat treatment time is 3
The time was fixed. After this treatment, the thickness of PPS film is 1
It was set to 0 to 25 μm. This layer was used as a charge transport layer, and as a charge generation layer, a-Si: H, which has a large quantum efficiency and a good sensitivity over the entire visible light range, was adopted. The film formation of a-Si: H was performed by the plasma CVD method. The substrate on which the PPS film was attached was placed in a parallel plate type capacitively coupled plasma CVD apparatus having a 6-inch discharge electrode, the reaction vessel was evacuated to 5 × 10 ⁻⁶ Torr or less, and the substrate was heated to 150 to The heating was controlled to a constant temperature in the temperature range of 200 ° C. SiH ₄ gas in the reaction vessel,
Introduce 50 sccm, H ₂ gas mixed at 250 sccm, and set the container pressure to 0.2
A high frequency of ˜1.0 Torr, 13.56 MHZ was formed under the condition of an electric power of 40 to 80 W, and an a-Si: H layer was formed as a photoconductive layer to form a 0.5 to 5.0 μ swallow.

When this electrophotographic photosensitive member was corona-charged at 6.0 kV, a surface potential of +1500 V could be obtained with a charge transport layer having a thickness of 20 μm, and when exposed to white light, the residual potential was +50 V or less, half the potential. The exposure amount was 1.01 x · s or less, which showed very excellent electrophotographic characteristics. When the composition of this electrophotographic photosensitive member was analyzed, C of O atoms contained in the charge transport layer was analyzed.
The composition ratio to the atoms was 12 atm%.

As a comparison, heat treatment after fusion of PPS film was 0.1 Torr.
Performed under the following reduced pressure, O atom number is 1 atm% to C atom
The following charge transport layer was obtained, and the a-Si; H layer was formed as the charge generation layer as described above. The characteristics of this electrophotographic photoreceptor are
The residual potential was +400 V or more, and the half-exposure amount was 1501x · s or more, which was inferior. Further, when the number of O atoms in the film was changed to 50 atm% by the heating time of the heat treatment in the oxygen atmosphere, the number was 1 to 35 atm%
Up to 50 V, the residual potential was less than +50 V, showing electrophotographic characteristics with no practical problems.

Example 2 When forming the charge generation layer, TCNQ (7,7,8,8, -tetracyanoquinodimethane) was added as an electron acceptor simultaneously with the fusion treatment. A charge transport layer was formed by heat treatment in an oxygen atmosphere under the same conditions as in Example 1 with a film thickness of 25 μm added to the PPS film as the raw material at a content of 5% by weight. An a-Si: H layer and an a-SiCx: H (amorphous silicon carbide) layer were adopted as the charge generation layer, and the electrophotographic characteristics were evaluated. As a result, when the charge generation layer was an a-Si: H layer, the residual potential was +30 V or less, and the half-exposure amount was 0.61 x · s or less, which showed favorable characteristics. Even when the charge generation layer was an a-SiCx: H layer, the same electrophotographic characteristics were obtained. The film formation of the a-SiCx: H layer was performed by using plasma CV with the introduction gas being a mixture of C ₂ H ₂ and SiH _4.
D method was used.

EFFECTS OF THE INVENTION According to the present invention, in a function-separated electrophotographic photosensitive member including a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transports the carriers, the charge transport layer is P-
A linear compound polymer layer having phenylene and a VIb group element in the para position, containing at least one of S, Se, and Te as a VIb group element, and further containing an O atom Thus, an electrophotographic photoreceptor having high sensitivity and low residual potential can be obtained. Further, by providing an amorphous layer having high hardness on the surface, high printing durability can be obtained. Furthermore, since the charge transport layer layer can be produced by fusing a polymer, an inexpensive electrophotographic photoreceptor can be provided.

[Brief description of drawings]

The drawing is a cross-sectional view of an electrophotographic photosensitive member according to an embodiment of the present invention. 1 ... Support, 2 ... Charge transport layer, 3 ... Charge generation layer,
4 ... Free surface.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Koji Akiyama 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masanori Watanabe 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 56) References JP-A-60-59353 (JP, A) JP-A-55-90954 (JP, A) JP-A-59-224846 (JP, A) JP-A-62-113156 (JP, A)

Claims (4)

[Claims] 1. A function-separated electrophotographic photosensitive member comprising a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transports the carriers, wherein the charge transport layer is P-.
A linear compound polymer layer having phenylene and a VIb group element in the para position, containing at least one of S, Se, and Te as a VIb group element, and further containing an O atom in the VIb group.
An electrophotographic photoreceptor characterized in that it is contained outside and above the polymer chain separately from the group. 2. The electrophotographic photoreceptor according to claim 1, wherein the ratio of the number of O atoms to the number of C atoms in the charge transport layer is 1 to 35 atm%. 3. A function-separated electrophotographic photosensitive member comprising a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transports the carriers, wherein the charge transport layer is P-.
A linear compound polymer layer having phenylene and a VIb group element in the para position, containing at least one of S, Se, and Te as a VIb group element, and further containing an O atom in the VIb group.
In the method for producing an electrophotographic photosensitive member which is contained outside the polymer chain in addition to the polymer group, the step of forming the charge transport layer includes a heat treatment in an oxygen atmosphere. Method. 4. The method for producing an electrophotographic photosensitive member according to claim 3, wherein the heating temperature of the heat treatment in an oxygen atmosphere is in the range of 250 to 350 ° C.