JPH02132449A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance the adhesive property of films and to improve the durability of the photosensitive body by constituting a charge transfer layer of carbon or a film essentially consisting of carbon and reducing the thickness in the end part of the film. CONSTITUTION:A charge generating layer 2 and the charge transfer layer 1 are successively laminated via an under coating layer at need on a cylindrical conductive base 3 consisting of Al, etc., to form the photosensitive body. The layer 1 is formed of the C or the film essentially consisting of the C and is formed to have the film thickness smaller in the longitudinal end part than in the central part thereof. This layer 1 is formed by disposing a shielding mesh apart a spacing to cover the end part of the layer 2 of the base 3 carried into, for example, a plasma CVD device and evacuating the inside of the vessel, then introducing a prescribed amt. of H2 and methane into the device and impressing high-frequency electric power. The layer 2 is formed by application of a coating liquid contg. a trisazo pigment, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cylindrical photosensitive drum used in an electrophotographic process.

``Prior Art'' Conventionally, photoreceptors used in electrophotography include those in which an inorganic photoconductive material such as selenium is dispersed in a binder on a conductive support, and Those using organic photoconductive materials such as ruhazol, trini-1-rofluoreon, or azo pigments, and those using amorphous silicon-based materials are generally known.

The "electrophotographic method" referred to here generally refers to a photoconductive photoreceptor that is first charged in a dark place by, for example, corona discharge, and then exposed to image light to selectively dissipate the charge only in the exposed areas. An electric latent image is obtained, and this latent image area is dyed. This is one of the image forming methods in which an image is formed by developing and visualizing electrostatic fine particles (toner) composed of a coloring material such as a pigment and a binder such as a polymeric substance.

The basic characteristics required of the photoreceptor in such electrophotography are (1) the ability to be charged to an appropriate potential in a dark place;

(2) Less charge dissipation in a dark place.

(3) Scales that quickly dissipate charge when irradiated with light.

Examples include.

In addition to these basic properties, each of the above-mentioned photoconductors has excellent features and disadvantages in practical use, but in recent years, they have become particularly popular, with low production costs of 1~1, less environmental pollution, and relatively free use. The development of organic photoreceptors is remarkable due to the ability to design photoconductors.

In general, an organic photoreceptor is one in which a charge transport material is dispersed or dissolved in a binder resin and coated on a conductive support, allowing charge retention and charge generation in one layer. A single layer type with a charge transport function, a charge generation layer (CGL) with a charge generation function, a charge transport layer (CTL) with a function of holding charged charges and transporting charges injected from the CGL, and furthermore, as necessary. Accordingly, a functionally separated type is known, which has a laminated layer having the function of blocking the injection of charge from the support or preventing the reflection of light on the support.

The charge transport layer used in the functionally separated type is a layer whose purpose is to retain electrical charges and to move the charges generated and separated in the charge generation layer upon exposure to combine with the retained electrical charges. . In order to achieve the purpose of retaining the charged charges, a high electrical resistance is required, and in order to achieve the purpose of obtaining a high surface potential with the retained charges,
It is required to have a low dielectric constant and good charge mobility.

In order to satisfy these requirements, a charge transport layer composed of a charge transport substance and a binder resin used as necessary is used.

Charge transport materials include hole transport materials and electron transport materials.

Examples of hole transport substances include poly-N-vinyl ruhazole and its derivatives, poly-γ-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, and oxadiazole derivatives. , imidazole derivative, triphenylamine derivative 9-(p-diethylaminostyryl)anthracene, 1,1-bis-(4-dibenzylaminophenyl)
Propane, styryl anthracene. Styrylpyrazoline, phenylhydrazones. Examples include electron-donating substances such as α-phenylstilbene derivatives.

Examples of electron transport substances include chloranil, promanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-trinitro-9fluorenone,
2,4,5.7-tetranitro-9-fluorenone, 2
,4,5.7-tetranitroxanthone,2,4.8-
}linitrothioxanthone, 2,6.8-trinitro-4-indeno[1.2-b)thiophene-4one, 1,3.7-trinitrodihenzothiophenone 5,
Examples include electron-accepting substances such as 5-dioxide.

A charge transport layer is formed by dissolving or dispersing the above-mentioned substances in a suitable solvent and applying and drying the solution.

In addition to the above-mentioned charge transport layer, it is also known that amorphous carbon, that is, carbon or a film containing carbon as a main component, can be used as the charge transport layer. -073261,
Patent application 1986-081360 to 1983-081365
, patent application No. 63-081445 to patent application No. 63-0814
90, Japanese Patent Application No. 63-082425 to No. 63-08
2488, Japanese Patent Application No. 63-218961 - Japanese Patent Application No. 1983-
218963 and the like. Carbon or a film containing carbon as a main component has extremely high hardness, and can be expected to have very good wear resistance when used as a charge transport layer.

As such carbon or a coating mainly composed of carbon, "Composite with Carbon Coating and Method for Preparing the Same" filed by the present inventor (Japanese Patent Application No. 146936/1982 filed on May 17, 1982) is known. The carbon or coating mainly composed of carbon is compatible with organic materials and has good adhesion.This is because the coating mainly composed of carbon is considered to be a type of organic film. This is because it is expected that there is a polymeric bond at the interface between the organic photoreceptor and the coating mainly composed of carbon.

"Problems to be Solved by the Invention" However, when the charge transport layer is formed in contact with the charge generation layer using carbon or a film mainly composed of carbon, the film mainly composed of carbon has an internal stress of 109 dyn/cm2. As described above, although good adhesion with the charge generation layer can be obtained at the initial stage of use, there is a problem in that beering occurs during long-term use.

The present invention has been made for the purpose of eliminating the above-mentioned problems and applying carbon or a film containing carbon as a main component to a charge transport layer in an electrophotographic photoreceptor.

"Means for Solving the Problems" That is, in order to achieve the above object, a charge generation layer having a charge generation function and a charge transport function injected from the charge generation layer are provided on a cylindrical conductive support. An electrophotographic photoreceptor comprising charge transport layers laminated in this order, wherein the charge transport layer is made of carbon or a film containing carbon as a main component, and the thickness of the charge transport layer is equal to that of the cylindrical conductive support. The electrophotographic photoreceptor is characterized in that the thickness of the electrophotographic photoreceptor becomes thinner in the longitudinal direction from the center toward the ends.

The inventors of the present invention repeatedly conducted long-term reliability tests and found that most of the peeling occurred from the edges of the protective film, and the film thickness at the edges was reduced to at least 1 nm from the center of the edges.
+m or more, preferably 5n+m or more, if the film thickness at the edge is one-third or less, preferably one-fifth or less of the film thickness at the center, peeling between the protective film and the base will occur. It was confirmed that this can be reduced to one-tenth or less, leading to the present invention.

"Structure of the invention" FIG. 1 shows a cross-sectional view of an example of the photoreceptor of the present invention.

A charge generation layer (2) and a charge transport layer (1) were formed on a conductive support (3).

As the conductive support in the present invention, a conductor or an insulator treated for conductivity is used.

For example, a thin film of a metal such as AI, Ag, Au, or a conductive material such as Inzo:+, SnOz, etc. on an insulating substrate such as a metal or alloy such as AI, Ni, Fe, Cu, or Au, or polyester, polycarbonate, polyimide, or glass. Examples include paper with conductive treatment, etc.

Further, the shape of the conductive support is not limited to a cylindrical shape, but a plate shape or a belt shape may be used as necessary.

As the charge generation layer (CC; L), an inorganic photoconductive powder such as crystalline selenium or arsenic selenide, or an organic dye and pigment dispersed or dissolved in a binder resin is used.

As an organic dye and pigment as a charge generating substance, for example, C.I. Pigment Blue-25 [Color Index (CI)
21180), CI Pigment Red 4HCI2
1200), Sea Acid Red 52 (Cl
45100), C.I. Basic Red 3 (C4
45210), and cyanide pigments having a porphyrin skeleton, azulenium salt pigments, and squalic salt pigments. Azo pigments having a carbazole skeleton
-95033), azo pigments having a styrylstilbene skeleton (described in JP-A-53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53132547), dibenzothiophine Azo pigments having a skeleton (described in JP-A No. 54-21728), ab pigments having an oxadiazole skeleton (described in JP-A-54-12742), azo pigments having a fluorenone skeleton (described in JP-A-54-12742), -22834), azo pigments with a bisstilbene skeleton (described in JP-A-5417733), azo pigments with a distyryloxadiazole skeleton (described in JP-A-54-212),
9), an azo pigment having a distyryl-rubazole skeleton (described in JP-A-54-2129), an azo pigment having a distyryl-rubazole skeleton (described in JP-A-54-2129),
417734), triazo pigments having a carbazole skeleton (described in JP-A-57-195767 and JP-A-57-195768), and cyanine-based pigments such as C.I. Pigment Blue-16 (c+ 74100). Pigment, Sea Eye Bud Brown 5 (CI 7
3410), Sea Eye Baddie (Cl 73030)
) 9 and other indigo pigments, and perylene pigments such as Argo Scarlet B (manufactured by Hanolet) and Indus Thread Scarlet R (manufactured by Bayer).

These charge generating substances may be used alone or in combination of two or more.

The amount of the binder resin is 0 to 100 parts by weight of the charge generating substance.
It is appropriate to use 100 parts by weight, preferably 0 to 5 parts by weight.
It is 0 parts by weight.

Binding resins used in combination with these organic dyes and pigments include polyimide, polyurethane, polyester epoxy resin,
Condensation resins such as polycarbonate and polyether, and polymers and copolymers such as polystyrene, polyacrylate, polymethacrylate, poly-N-vinyl rubber, polyvinyl butyral, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, etc. Adhesive and insulating resins such as

The charge generation layer contains a charge generation substance, along with a binder resin if necessary, tetrahydrofuran, cyclohexanone,
It can be formed by dispersing using a ball mill, attritor, Santomill, etc. using a solvent such as dioxane or dichloroethane, diluting the dispersion liquid appropriately, and applying the dispersion. Application can be performed using a dip coating method, a spray coating method, a bead coating method, or the like.

The thickness of the charge generation layer is suitably about 0.01 to 5 .mu.m, preferably 0.1 to 2 .mu.m.

When particles of crystalline selenium or arsenic selenide alloy are used as the charge-generating substance, they are used in combination with an electron-donating binder and/or an electron-donating organic compound. Examples of such electron-donating substances include polyvinyl Rubazole and its derivatives (for example, those having substituents such as halogens such as chlorine and bromine, and substituents such as methyl and amino groups in the carhazole skeleton), polyvinylpyrene, and oxadiazole. Biladurine hydrazone, diarylmethane α-phenylstilhene l
- Nitrogen-containing compounds such as liphenylamine compounds, diarylmethane compounds, etc. are included, and polyvinyl ruhazole and its derivatives are particularly preferred. Alternatively, a mixture of these substances may be used. Even when used in combination, it is preferable to add other electron-donating organic compounds to polyvinylcarbazole and its derivatives. The content of this type of inorganic charge generating substance is 30 to 90% by weight of the entire layer.
is appropriate. Further, when an inorganic charge generating material is used, the thickness of the charge generating layer is suitably 0.2 to 5 .mu.m.

FIG. 2 shows an example of an apparatus for producing carbon or a coating mainly composed of carbon used as a charge transport layer in the present invention. In the drawing, the stainless steel container (1") has a lid (1'
), forming a reaction space (1). The substrate (10) on which the coating is to be formed is held between the holders (8) and (8
”) was rotated and held.M(1') on the back side
An exhaust port (7) with a homogenizer (20') is provided on the ``) side, and the cover (1'') is opened upward when mounting the substrate. A high frequency voltage or a DC voltage was applied between one electrode and the other mesh electrode (20) by means of this base holder. Here, a high frequency electric field of 13.56 MHz or with a DC bias is applied from a high frequency or DC power supply (6). One of the characteristics of the film forming method used in the present invention is that the hardness of carbon or a film containing carbon as a main component can be controlled by the value of this DC high ass.

The substrate (10) is positioned in FIG. 2 perpendicular to this electric field. A shield mesh (22) is installed with a space of at least 10 mm, preferably 5 mm or less, from the surface of the base so as to overlap by about 10 mm from the end of the base.

The shield mesh is provided to prevent the space between the base and the mesh near the end from becoming plasma, and is kept at the same potential as the base. The thickness of the film at the end of the substrate can be adjusted by adjusting the degree of overlapping of the meshes. Further, in order to improve the uniformity of the substrate in the circumferential direction, the substrate is rotated in the circumferential direction.

Furthermore, when the left and right direction is long in FIG. 2, the seal mesh and the drum may be rotated and moved at the same time as the coating is formed. A large number of these substrates may be arranged (in the front-rear direction of the drawing) and moved while rotating so as to simultaneously form a large number of films with uniform thickness.

The reactive gas is supplied from the doping system (13) via (18) to the resonance space (2) using microwaves made of a quartz tube (29). Air-core magnet coils (5) and (5') are placed on the outside of this resonance space to apply a magnetic field. At the same time, the microwave oscillator (3) passes through the analyzer (4) and a microwave of, for example, 2.45 GHz is transmitted to the resonant space (2).
supplied to In this space, in order to cause Whistler mode resonance, reactive gases include hydrocarbons such as methane, ethane, ethylene, and acetylene, or carbon fluorides such as carbon tetrafluoride, dicarbon hexafluoride, and Hensen hexafluoride. Carbide gases such as fluorocarbon hydride such as trifluorohydrocarbon (
32) Add more.

Furthermore, diborane (BZH6) or phosphin (pna) diluted with hydrogen, or a nitrogen compound such as nitrogen trifluoride or ammonia is used as a doping gas (32)
Further, hydrogen carrier gas is added from (31).

The pressure is controlled by the control hub (14) of the exhaust system (11).
The displacement of the vacuum pump (9) which is also used with a turbo molecular pump was adjusted according to the following.

Furthermore, 50 W to IKW was applied as high frequency power and 0.03 to 3 W/cm2 as plasma electric field. Unless a DC bias is particularly applied, a large amount of hydrogen is contained in the carbon film, and 2.5 to 3.5 eV can be obtained even during optical energy handing.

When a positive bias is applied to the substrate side, hydrogen ions are repelled, resulting in a decrease in the hydrogen content in the film, and the optical energy band also decreases from 1.0 to 2. It becomes OeV.

Further, if necessary, in the drawing, one electrode (20) can also use the effect of a reactive gas homogenizer (20) in order to sufficiently spread electron or resonance excited argon into the reaction space. That is, in order to form a film uniformly over a wide area on the surface of the substrate with the gas (21) released from the holes of the homogenizer, and to obtain better uniformity in the thickness over a large area other than the ends of the substrate, it is of course preferable to use a homogenizer. When this happens, collisions of electrons and active gases on this surface are unavoidable, resulting in energy consumption there and a reduction in the growth rate. Therefore,
In order to obtain a high growth rate in the entire space,
High frequency excitation by microwave is more effective than plasma CVD alone.

Substrate surface temperature is -100 to +150°C, preferably -1
00 to +IOO'C, and even if the heat resistance of the charge generation layer is not sufficiently high, there will be no damage, melting, or deterioration during coating with this carbon film.

Furthermore, if preliminary excitation with microwaves is performed, a film formation rate of 500 to IOOOA/min can be obtained in this case, and extremely high-speed film formation is possible. However, without this pre-excitation, a deposition rate of only 100 to 200 persons/min can be obtained.

Carbon or a coating mainly composed of carbon produced by the above-mentioned production method forms C-C bonds similar to those of diamond, has a Vickers hardness of 100 to 3000 Kg/cm2, and a specific resistance (specific resistance 'I I I XIO”Ωc
m, and the optical energy band width (referred to as E.) is 1. OeV or more, preferably 1.5 to 5.5e
It has properties similar to those of diamond, which is transparent in the infrared or visible region.

In order to function as a charge transport layer, a film thickness of at least 5 μm or more, preferably 10 μm or more is required, so as shown in FIG.
11) The film thickness is 2 μm to 5 μm.8 The film thickness of the central part (12) that is actually used is 10 μm to 15 μm, and the film thickness of the part (13) that is 5 to 10 mffl from the end is gradually increased as it gets closer to the center than the end. The structure was designed so that the film thickness was increased.

In addition, mechanical strength improvement or? Carbon or a coating mainly composed of carbon may be provided as a protective layer to improve water resistance. Of course, in that case, it goes without saying that the end portions should be made thinner than the center portion.

The present invention will be illustrated below with reference to Examples.

〔Example〕

In this example, hydrogen and methane are used as the charge transport layer at 1=
1, an amorphous carbon film containing diamond bonds or diamond microcrystals is formed.

Aluminum cylindrical support (outer diameter 40mmφ, length 2
A subbing layer forming solution prepared by dispersing a mixture having the composition ratio shown below in a 50 mm film for 12 hours using a ball mill was applied by dipping to form an undercoat layer so that the thickness after drying would be about 2 μm.

[Subbing layer forming liquid]

TiO■ (Tie Bake manufactured by Ishihara Sangyo Co., Ltd.) 1 part by weight Polyamide resin (CM-8000 manufactured by Toray Industries) 1 part by weight methanol 25 parts by weight Dip a charge generation layer coating liquid (I8) of the following formulation onto this subbing layer. Coat and dry the tube at 120"C for 10 minutes until the film thickness is about 0.
．． A charge generation layer of 15 μm was formed.

[Charge generation layer coating liquid]

Trisazo pigment with the following structure: 30 parts by weight Polyester resin (Toyobo Hylon) 12 parts by weight cyclohexane 360 parts After dispersing the above mixture in a ball mill for 72 hours, 500 parts by weight of a mixed solvent of cyclohexane:methyl ethyl ketone = 1=1 (weight ratio) Adjust the dilution in 1 part.

Next, carbon or a film containing carbon as a main component was provided on this charge generation layer.

The pressure in the reaction space was set to Q, l torr, and 2003 CCM of hydrogen was supplied from (31) as a non-product gas. In addition, methane was fed from (32) at 2005 CCM.

The microwave has a frequency of 2.45G}lz and an output of 5
Adjusted with 00ri. The resonance intensity of the magnetic fields (5) and (5') was set to 875 Gauss.

13.56MtlzO high frequency power of 500W was applied. After starting the discharge, the exhaust system was adjusted.

Place the shield mesh (22) approximately 10mm from the end of the base.
When the base and shield mesh were installed so that they overlapped with the base and the distance between the base and the shield mesh was 3 mm, the space between the base and the shield mesh was not turned into plasma, and no coating was left on the edges of the base. not formed,
The film thickness is 0.01μm to 10mm from the end to 10mm.
It varied down to μm. The film thickness at the center excluding 10+yun from both ends was approximately 10 μM and uniform.

When the substrate temperature was room temperature, a film formation speed of 30 people and 7 seconds could be achieved, and the film formation time was about 60 minutes. This speed is 20 times faster than the 1.5 persons/second obtained by plasma CVD alone. An example of the electrical properties of this amorphous carbon is that it has a specific resistance of 10'3 Ωcm, a Vickers hardness of 2300 Kg/mm2, and an optical energy band width of 1.8.
It was eV.

[Comparative example]

After forming a subbing layer in the same manner as on the same aluminum cylindrical support as in the example and forming a charge generation layer in the same manner, a carbon or carbon-based layer was formed in the case where the film thickness was not made thinner at the edges. A film containing the components was formed as a charge transport layer.

[Experimental Example 1] For the photoreceptors manufactured according to this example and experimental examples, -
60°C → room temperature → -60'C temperature/recycle 10
The results of 0 tests are shown in Tables 1 and 2. Table 1 shows the results of the Example samples, and Table 2 shows the results of the Comparative Example samples. As shown in Table 1, in the samples of Examples, the coating did not crack, peel or peel from the substrate, and the yield was 100%.

In comparison, as shown in Table 2, about 90% of the comparative samples had cracks in the coating, peeled off from the substrate, or peeled. It can be seen how excellent the adhesion of the charge transport layer made of the film is.

Table 1 Table 2 [Experimental Example 2] Sample was actually attached to an electrostatic copying machine and copies were made repeatedly to check for peeling from the edges of the charge transport layer, which is made of carbon or a film mainly composed of carbon. Observed.

The size of the paper used was A4 size.

In the photoreceptor produced in the experimental example, 104 to 7×104
Although peeling was observed in some sheets, there was no change in the photoreceptor fabricated in the experimental example even when copying 105 to 106 sheets.

It was also confirmed here that the charge transport layer made of carbon or a film mainly composed of carbon to which the present invention was applied had excellent adhesion.

"Effects" In the present invention, the charge transport layer in the photoreceptor is composed of carbon or a film containing carbon as a main component, and the end portions of the film are made thinner to improve adhesion. This made it possible to significantly improve the durability of the photoreceptor.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view of an embodiment of a photosensitive drum using the present invention. FIG. 2 shows a plasma CVD apparatus for producing a carbon film used in the present invention.

Claims (1)

[Claims] An electrophotographic photoreceptor in which a charge generation layer having a charge generation function and a charge transport layer having a function of transporting charges injected from the charge generation layer are laminated in this order on a cylindrical conductive support, The transport layer is made of carbon or a film containing carbon as a main component, and the thickness of the charge transport layer becomes thinner along the length of the cylindrical conductive support as it gets closer to the ends than the center. An electrophotographic photoreceptor characterized by: