JPH02210458A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent the peeling and cracking of a protective layer and to obtain superior durability over a long period of time by regulating the difference in Vickers hardness between an org. photosensitive layer and a high hardness thin film made of carbon or based on carbon as the protective layer to a specified value or below. CONSTITUTION:An underlayer 2, an electric charge generating layer 3, an electric charge transferring layer 4 and a protective surface layer 5 are successively laminated on an electrically conductive support 1. The layer 5 is made of carbon or based on carbon and the difference (DELTAHv) in Vickers hardness between the layer 5 and an org. photosensitive layer consisting of the layers 3, 4 is regulated to <2,500kg/mm<2> so that the adhesive strength of the photosensitive layer to the layer 5 exceeds the mechanical stress of the layer 5. The peeling and cracking of the protective surface layer 5 are prevented, a fine copied image can be formed even after repeated use and the durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor having a surface protective layer on an organic photosensitive layer.

[Prior art]

Conventionally, photoreceptors used in electrophotography include those with a photoconductive layer mainly made of selenium or selenium alloys on a conductive support, and inorganic photoconductive materials such as oxidized zinc and cadmium sulfate. Generally known are those using organic photoconductive materials such as poly-N-onylcarbazole and trinitrofluorenone or azo pigments, and those using amorphous silicon-based materials. ing.

By the way, in general, the "electrophotographic method" means that a photoconductive photoreceptor is first charged in a dark place by, for example, corona discharge, and then imagewise exposed to selectively dissipate the charge only in the exposed area to create an electrostatic latent material. Image formation in which an image is obtained by obtaining an image, and developing and visualizing this latent image area with electrostatic fine particles (toner) made of coloring materials such as dyes and pigments and binders such as polymeric substances to form an image. It is one of the laws.

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 the dark.

(3) Charge can be quickly dissipated by light irradiation.

Examples include.

In addition to these basic characteristics, each of the above-mentioned photoconductors has excellent features and disadvantages in practical use, but in recent years, photoconductors that have low manufacturing costs, little environmental pollution, and are relatively free have been developed. Organic photoreceptors are rapidly developing due to their ease of design.

In general, an organic photoreceptor is a material in which a charge-generating material and a charge-transporting material are dispersed or dissolved in a binder resin and coated on a conductive support. Single layer type with transport function, charge generation layer (CGL) with charge generation function, charge retention and CG
A charge transport layer having a function of transporting charges injected from L (
CTL), and a function-separated type with an M-layer structure including layers with functions such as blocking charge injection from the support or preventing light reflection from the support as necessary. Are known.

These organic photoreceptors have excellent characteristics as mentioned above, but because they are organic materials, their surface hardness is low and they are susceptible to damage from developer, transfer paper, cleaning materials, etc. during actual use in the copying process. Another disadvantage of wood is that it is susceptible to wear and scratches due to mechanical loads.

This abrasion of the photosensitive layer causes a decrease in the charging potential, and local scratches cause streak-like abnormal images to appear on copies, both of which are important problems that affect the life of the photoreceptor.

In order to overcome these drawbacks, a method has been proposed in which a protective layer is provided on the surface of the organic photosensitive layer to improve its durability against mechanical loads received inside and outside the copying machine.

For example, a method of providing an organic film on the surface of a photosensitive layer (
Japanese Patent Publication No. 38-015446), method of providing an inorganic oxide (Japanese Patent Publication No. 43-014517), method of laminating an insulating layer after providing an adhesive layer (Japanese Patent Publication No. 43-027591.),
Or a-5 by plasma CVD method, photo CVD method, etc.
Method of laminating i layer, 5-3i:N:11 layer, a-8i:0:8 layer, etc. (JP-A-57-179859, JP-A-5
9-058437> etc. are disclosed.

Furthermore, in recent years, the application of high-hardness diamond-like carbon films to protective layers has become active.

For example, a protective layer made of amorphous carbon or hard carbon is provided on the photosensitive layer (Japanese Patent Application Laid-Open No. 6O-249155),
A diamond-like carbon protective layer is provided on the outermost surface (
Japanese Unexamined Patent Publication No. 61-255352), a photosensitive layer in which a high hardness insulating layer mainly composed of carbon is formed (Jikai U (76)
264355) or a protective layer formed of a plasma organic polymer film containing at least m(m) atoms such as nitrogen atoms, oxygen atoms, halogen atoms, alkali metal atoms, etc. is provided on the organic photosensitive layer (JP-A-63-97961-4). , a protective layer consisting of an amorphous hydrocarbon film generated by glow discharge containing at least chalcogen atoms, group II atoms, group II atoms, group II atoms, etc. is provided on an organic photosensitive layer (Japanese Patent Application Laid-open No. 63
-220166 to 9).

In all of these proposals, a highly hard thin film (i-carbon film or It belongs to what is collectively called a diamond-like carbon film.)

The photoreceptor obtained by this method has an organic photosensitive layer with improved surface hardness and is excellent in durability. Subsequent research has revealed that if an excessively hard surface protective layer is laminated on the surface protective layer, the surface protective layer may peel off.

[Problem to be solved by the invention]

The present invention was made precisely to solve these problems, and its purpose is to improve the Vickers hardness difference between an organic photosensitive layer and a protective layer consisting of carbon or a highly hard thin film mainly composed of carbon. By limiting the value to below a certain value,
It is an object of the present invention to provide an electrophotographic photoreceptor that exhibits excellent durability over a long period of time without peeling of a protective layer or generation of cracks.

[Means to solve the problem]

According to the present invention, the above-mentioned object is an electrophotographic photoreceptor having a structure in which at least an organic photosensitive layer and a surface protective layer are laminated on a conductive support, the surface protective layer containing carbon or carbon as a main component; This is achieved by an electrophotographic photoreceptor characterized in that the difference in Vickers hardness between the surface protective layer and the organic photosensitive layer is 2500 Kg/mm2 or less.

Generally, it is said that the durability of an electrophotographic photoreceptor having a structure in which a surface protective layer is laminated on an organic photosensitive layer is greatly influenced by the mechanical strength, particularly the hardness, of the surface protective layer. Therefore, it is usually desirable for the hardness of the surface protective layer to be as high as possible, but according to the research of the present inventors, a surface protective layer consisting of carbon or carbon as a main component is It was found that when the protective layer was laminated, the protective layer unexpectedly peeled off and cracked, and the durability was not necessarily improved.

Further research revealed that the cause of this was that the Vickers hardness was approximately 2.
When a surface protective layer with extremely high hardness consisting of carbon or carbon as a main component is laminated on an organic photosensitive layer with a low hardness of 0 kg/mm2, the adhesive strength between the organic photosensitive layer and the surface protective layer is stronger than the surface protective layer. It was found that this is because the mechanical stress of

In order to solve this problem, the present inventors conducted further research and found that the difference in Vickers hardness Δ)1ν between the surface protective layer laminated on the organic photosensitive layer and this layer was 2500 kg/
mm" or less, the adhesive force between the organic photosensitive layer and the surface protective layer is stronger than the mechanical stress of the surface protective layer, so the protective layer does not peel or crack, making it a highly durable electronic film. It was discovered that a photographic photoreceptor could be obtained, and the present invention was completed.

That is, the present invention is characterized in that the difference in Pinkers hardness between the organic photosensitive layer and the surface protective layer, Hv, is defined to be 2500 Kg/mm'', preferably 2000 Kg/mm'' or less.

If the Vickers hardness difference Hv exceeds 2500 Kg/mm'', fine cracks will occur in the surface protective layer and peeling will occur in the circumferential direction, making it impossible to achieve the intended purpose of the present invention.

The Vickers hardness of the organic photosensitive layer and the surface protective layer can be arbitrarily determined within the range that satisfies the above relationship, but usually,
The Vickers hardness of the organic photosensitive layer is 1 (v(I) is 10-1
00Kg/mm2, preferably 10-50Kg'/mm
2, the Vickers hardness Hv (II) of the surface protective layer is 10
0-2500Kg/mm2, preferably 500-100
It is desirable to set it within the range of 0Kg/mm''.

=8 FIG. 1 is a schematic cross-sectional view of the electrophotographic photoreceptor of the present invention, in which a subbing layer N2, a charge generation layer 3, a charge transport layer N4, and a surface protection layer 5 are sequentially provided on a conductive support 1. It is of composition.

FIG. 2(a) and FIG. 2(b) respectively show structural examples of other electrophotographic photoreceptors of the present invention, and FIG. 2(a)
2(b) shows a single-layer type organic photosensitive layer N6 provided on a conductive support 1 via an undercoat layer 2, and a surface protection layer N5 sequentially provided on the second layer. A charge transport M4 is provided directly on the magnetic support 1, and a charge generation layer 3 is further provided thereon. and a surface protective layer 5 are sequentially provided.

The conductive support used in the present invention may be a conductor or an insulator treated for conductivity, such as AQ, Ni, F
In addition to metals such as E, Cu, and Au, or their alloys, thin films of metals such as An, Ag, and Au, or conductive materials such as In and 03.5ue2 are deposited on insulating substrates such as polyester, polycarbonate, polyimide, and glass. It is possible to use paper that has been formed or has been treated with electrical conductivity.

There are no particular restrictions on the shape of the conductive support, and any of the shapes of a plate, drum, or belt can be used.

An undercoat layer provided between the conductive support and the photosensitive layer as necessary is provided for the purpose of further improving the effects of the present invention and improving adhesion, and its material is SS10.
Inorganic materials such as 1AQ20, silane coupling agents, titanium coupling agents, chromium coupling agents, and binder resins with good adhesive properties such as polyamide resins, alcohol-soluble polyamide resins, water-soluble polyvinyl butyral, polyvinyl butyral, and PVA are used. Ru. others,
It is also possible to use a resin in which ZnO, Ti, 0□, ZnS, etc. are dispersed in the resin with good adhesive properties. As a method for forming the undercoat layer, methods such as sputtering and vapor deposition are used when an inorganic material alone is used, and when an organic material is used, a normal coating method is used. Note that the thickness of the undercoat layer is suitably 5 μm or less.

The organic photosensitive layer provided directly or via an undercoat layer on this conductive support may be either a single layer type or a functionally separated type as long as it satisfies the above-mentioned Peakers hardness Hv (1,). Also applicable.

Examples of single-layer photosensitive layers include dye-sensitized zinc oxide,
Photoconductive powder such as titanium oxide and zinc sulfate, selenium powder,
Amorphous silicon powder, Squaric salt pigment, phthalocyanine pigment, azulenium salt pigment, azo pigment, etc. are coated together with a binder resin and/or an electron-donating compound as described below, as required, and biryllium dyes. Examples include those using a composition in which an electron-donating compound is added to a eutectic complex formed from a bisphenol A-based polycarbonate and a bisphenol A-based polycarbonate. As the binder resin, the same resin as that used in the functionally separated photosensitive layer described later can be used. The thickness of this single-layer type photosensitive layer is suitably 5 to 30 μm.

On the other hand, an example of a functionally separated photosensitive layer is a charge generation layer (CG
An example is a structure in which a charge transport layer (CTL) and a charge transport layer (CTL) are laminated.

As a charge generation layer (CGL) for generating and separating latent image charges by image mist light, an inorganic photoconductive powder such as crystalline selenium or arsenic selenide or an organic dye or pigment is dispersed or dissolved in a binder M resin. The one that was made is used.

Examples of organic dyes and pigments as charge-generating substances include:
CI Pigment Blue 25 [Color Index (
CI) 21180), CI Pigment Red 41 (
CI 21200), Sea Eye Acid Red 52 (C
I451.00), CI Basic Red 3 (CI
45210), phthalocyanine pigments having a porphyrin skeleton, azulenium salt pigments, squalic salt pigments, azo pigments having a carbazole skeleton (described in JP-A-53-95033), and azo pigments having a styrylstilbene skeleton (described in JP-A-53-95033). Azo pigments having a triphenylamine skeleton (described in JP-A-53-132547), azo pigments having a dibenzothiophene skeleton (described in JP-A-54-217)
28), an azo pigment having an oxadiazole skeleton (described in JP-A No. 54-12742), an azo pigment having a fluorenone skeleton (described in JP-A-54-2283)
4), azo pigments having a bisstilbene skeleton (described in JP-A-54-17733), azo pigments having a distyryloxadiazole skeleton (described in JP-A-54-17733),
-2129), azo pigments with a distyrylcarbazole skeleton (described in JP-A-54-17734), triazo pigments with a carbazole skeleton (JP-A-57-195767, JP-A-57-195768). In addition, CI Pigment Blue 1
Phthalocyanine pigments such as 6 ((A 74100), indigo pigments such as C.I. Pad Brown 5 (CI73410) and C.I. Bud Dye (CI 73030),
Perylene pigments such as Argo Scarlet B (manufactured by Violet) and Indus Thread Scarlet R (manufactured by Bayer) can be used.

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 polyamide, polyurethane, polyester, epoxy resin,
Condensation resins such as polyether-1-, polyether, and polymers such as polystyrene, polyacrylate, polymethacrylate, poly-N-vinylcarbazole, polyvinyl butyral, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, and Examples include adhesive and insulating resins such as copolymers.

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, sand mill, etc. using a solvent such as dioxane or dichloroethane, diluting the dispersion excessively, 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 tones, preferably 0.1 to 2/j111.

Further, in the present invention, when particles of crystalline selenium or arsenic selenide alloy are used as the charge generating substance, an electron-donating binder and/or an electron-donating organic compound are used together. Examples of such electron-donating substances include polyvinylcarbazole and its derivatives (for example, those having a halogen such as chlorine or bromine, or a substituent such as a methyl group or an amino group in the carbazole skeleton), polyvinylpyrene, oxadiazole, pyrazoline, and hydrazone. , diarylmethane, α-phenylstilbene, and triphenylamine compounds, and diarylmethane compounds, among which polyvinylcarbazole and its derivatives are particularly preferred.

These substances can also be used as a mixture, but in this case it is preferable to add another electron-donating organic compound to polyvinylcarbazole and its derivatives. The content of this type of inorganic charge generating substance is 30 to 9 in the entire layer.
0% weight is the weight. Further, when an inorganic charge generating material is used, the thickness of the charge generating layer is suitably 0.2 to 5 .mu.m.

The charge transport layer (CTL) is a layer whose purpose is to hold electric charges and to move the electric charges generated and separated in the charge generation layer by exposure and combine them with the held electric charges. In order to achieve the purpose of retaining charged charges, it is required to have high electrical resistance, and in order to achieve the purpose of obtaining a high surface potential from the retained charges, it is necessary to have a low dielectric constant and good charge mobility. required.

A charge transport layer that satisfies these requirements is composed of a charge transport substance and a binder resin used as necessary. That is, the charge transport layer can be formed by dissolving or dispersing the above-mentioned substances in a suitable solvent and applying and drying the solution.

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

As hole transport substances, poly-N-vinylcarbazole and its derivatives, poly-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9-(p-diethylaminostyryl)anthracene, 1, 1bis-(4-dibenzylaminophenyl)
Examples include electron-donating substances such as propane, styryl anthracene, styryl pyrazoline, phenylhydrazones, and α-phenylstilbene derivatives.

Examples of the electron transport substance include chloranil, bromoanil, tetracyanoethylene, te-1-lacyanoquinone dimethane, 2,4.7-tri-1-rho-9 fluorenone, 2,4,5.7-tetranitro-9- Fluorenone, 2,4,5.7-titranitroxanthone, 2,4°8-trinidrothioxanthone, 2,6.8-trinitro-4H-indenol:1,2-b) Thiophenone-
Examples include electron accepting substances such as 4-one, 1,3°7-trinitrodibenzothiophenone-5,5-dioxide.

These charge transport materials may be used alone or in combination of two or more.

Binder resins that may be used as necessary include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, Polymer, polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, phenoxy resin, polycarbonate 1-1 cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyltoluene, poly-N-vinylcarbazole, acrylic resin, silicone Examples include thermoplastic resins or thermosetting resins such as resins, epoxy resins, melamine resins, urethane resins, phenol resins, and alkyd resins.

As a solvent, tetrahydrofuran, dioxane, 1-
Luene, monochlorobenzene, dichloroethane, methylene chloride, etc. are used.

The appropriate thickness of the charge transport layer is about 5 to 100 μm.

Furthermore, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the appropriate amount to be used is about 0 to 30 parts by weight based on the binder resin. Silicone oils such as dimethyl silicone oil and methylphenyl silicone oil are used as leveling agents, and the amount used is () relative to the binder resin.
-1 double star% is appropriate.

These CGL and CTL are placed on the support from the support side.
They may be laminated in the order of L, C:TL, or (:TL, CGL).

In the present invention, the protection /W provided on the outermost surface is carbon or carbon-based as a main component, and has a Vickers hardness Hv (II) of 100-2500 kg/m as described above.
m, preferably 500 to 2000 Kg/mm", but preferably has a C-C bond similar to that of diamond having an SP" orbit and a specific resistance (specific resistance) IX] , 07-IX]
, 013Ω·σ and optical energy band width (referred to as Eg)]−, (LeV or more, and is formed of a thin film that is transparent in the infrared or visible region.

Such films are generally produced by sputtering or plasma CVD.
, formed by glow discharge decomposition method, photo-CVD method, etc.
Although the film forming method is not particularly limited, a protective layer having good properties can be obtained by forming the film using a plasma CVD method with a sputtering effect. A representative example of this is the patent application filed by the present inventor titled “Composite with Carbon Coating and Method for Manufacturing the Same” (
Patent application 1982-146929, filed on September 17, 1981,
JP-A-58-49609).

This method is a film forming method in which a substrate is placed on one electrode (cathode side) of a parallel plate plasma CVD device, and the active species are deposited on the top surface of the flat surface using a self-bias method. By strongly exciting the carbon film, a carbon film with high hardness can be obtained.

The above method is preferably applied when the substrate is in the form of a sheet, but for example, if a plasma CVD apparatus as shown in FIG. It is possible to do so.

In the figure, (7) is the vacuum chamber of the plasma CVD equipment, and the loading/unloading preliminary chamber (7°
). Inside the vacuum chamber (7) is the exhaust system (20)
[Pressure adjustment valve (21), turbo molecular pump (22)
, =20= rotary pump (23)] to evacuate and maintain a constant pressure.

A reaction tank (50) is provided within the vacuum tank (7).

The reaction tank has a frame structure (2) as shown in Figure 4 (A) and (B).
(has a square or hexagonal shape when viewed from the electrode side) and a foot (8) (8') that covers the openings at both ends.
), furthermore, a pair of first and second electrodes (3) (3) having the same shape are disposed on this hood (8) (8').
') (using metal mesh such as aluminum). (30) indicates a gas line introduced into the reaction tank (50), to which various gas containers as shown below are connected, each passing through a flow meter (29) and passing through a nozzle (25) into the reaction tank (50). ).

Carrier gas: 1 (2, Ar, etc. Material gas: Hydrocarbon gas (methane, ethylene, etc.) Additive gas: Nli, , N) 13. pH3, +3.
+1. Etching gas 20□ In the frame structure (2), a support m ((1-1), (1,-2), -(1-n)) on which an organic photoconductive layer is formed is contained. are arranged as shown in FIGS. 3(A) and 3(B). Note that each of these supports is arranged as a third electrode as described later.

A pair of power supplies (15) C (15-1,), (
15-2)] are available. The frequency of the first alternating voltage is 1 to 100 MIlz.

These power supplies each have a matching transformer (16-1
, ) (+6-2). The phase in this matching transformer is adjusted by a phase adjuster, and the phase is 180 degrees from each other.
Can be supplied with a deviation of 0° or 0°. That is, it has a symmetrical or in-phase output.

One end (4) and the other end (4') of the matching transformer are connected to the first and second electrodes (3) (3'), respectively. Further, the midpoint (5) on the output side of the transformer is held at the ground level. Further, between this midpoint (5) and the third electrode, that is, the support (1) [(1-1), (1-2), =
(1-n)) or a holder electrically connected to them (
2) Power supply (1) for applying the second alternating voltage
7) is provided. The frequency of this second alternating voltage is 1 to 500 KHz.

2] In this way, plasma is generated between the first and second electrodes (3) (3') by the first alternating voltage. Since this plasma is surrounded by the upper and lower hoods (8) (8') and the frame structure (2), it is not released into the external space (6), and the plasma potential within the reaction space is homogeneous. It has become. The reaction gas introduced into this reaction space through the nozzle (25) is decomposed by the energy of the plasma and accelerated by the negative self-bias (-1.0 to 600V) applied to the support by the second alternating voltage. ,
Since the film is formed on the support while sputtering, a film having a dense structure can be obtained.

The output of the first alternating voltage applied to the first and second electrodes is 0.1 to IKW at a frequency of 13.56 MHz, and the output of the second alternating voltage applied to the third electrode, that is, the support The output power is approximately 100W at a frequency of 150KHz.

The reaction gases typically used are ethylene and NF3, the ratio of which is NF3/C2H4 = 1/20 to 4/1, and the pressure inside the vacuum chamber during the reaction is 0.001 to 1.0 torr.
It is r.

By this method, ethylene and NF3 are decomposed in plasma to form a diamond-like thin film (also called DLC) containing N and F added to the support. In the present invention, a film (referred to as carbon or a film mainly composed of carbon) is obtained.

Additionally, this film-forming method allows the physical properties (hardness, light transmittance, specific resistance, etc.) of the resulting film to be relatively freely changed by changing film-forming conditions such as reaction pressure and reaction gas mixture ratio. . In particular, the hardness can be greatly varied by the negative self-bias and reaction pressure applied to the support. In addition, this method does not require any particular heating of the support, and can form carbon or carbon-based films at low temperatures below 150°C, so it can protect organic photosensitive layers with low heat resistance without any problems. It is possible to deposit layers.

The film thickness of this carbon or carbon-based protective layer is 10
0 to 10 μm, preferably 1000 to 2 μm
It is.

Additives such as halogen elements such as fluorine, nitrogen, phosphorus, and boron can be added to carbon or a protective layer mainly composed of carbon, and the concentration is uniform in the depth direction of the film. However, a gradient may be provided.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 Aluminum cylindrical support (outer diameter 4.0 nmφ
, length 250 mm) by dispersing a mixture with the following composition ratio in a ball mill for 12 hours, and then drying the undercoat layer forming liquid. /: A subbing layer was formed by applying the coating using a dipping method so as to form J2 units.

[Subbing layer forming liquid]

TiO2 (Tie Bake manufactured by 6 Hara Sangyo Co., Ltd.) 1 part by weight Polyamide resin (CM-8000 manufactured by Toshisha Co., Ltd.) 1 Methanol 25 A charge generation layer coating solution having the following formulation was dip coated on this subbing layer and heated at 120°C. 10
It was dried for a minute to form a charge generation layer with a thickness of about 0.15 μm.

[Charge generation layer coating liquid]

Trisazo pigment with the following structure: 30 parts by weight cyclohexanone 360 After dispersing the above mixture in a ball mill for 72 hours, a mixed solvent of cyclohexanone:methyl ethyl ketone-1=1 (weight ratio) 5
00 parts by weight.

Next, a charge transport layer was provided by dip coating a charge transport layer coating solution having the following formulation on this charge generating J-containing soil so that the film thickness after drying was approximately 20 μm.

[Charge transport layer coating liquid]

Tetrahydrofuran 80 The Vickers hardness Hv (I) of the charge transport layer thus prepared was measured and found to be approximately 20 Kg/mm2.

Further, on this charge transport layer, the above-mentioned plasma C shown in FIG.
A protective layer containing carbon or carbon as a main component was formed using a VD apparatus under the following conditions.

[Protective layer forming conditions]

NF3 flow rate: 50 SCCMC,H
4 Flow rate: 150 SCCM reaction pressure
: 0.02torr first alternating voltage output :
4001113.56 AHz bias voltage (DC component)
: -80V The Vickers hardness Hv (II) of carbon or a protective layer mainly composed of carbon thus obtained is 50.
The film thickness was 1 μm.

The electrophotographic photoreceptor of Example 1 was produced by the above operations.

Example 2 An electrophotographic photoreceptor of Example 2 was produced in the same manner as in Example 1, except that the film forming conditions for carbon or a protective layer containing carbon as a main component were changed to the following.

[Protective layer forming conditions]

NF3 flow rate: 50SC, CAC2■14 flow rate: 150 SCCMCC property
: 0,05torr first alternating voltage output:
400W (1, 3, 56MHz) Bias voltage (DC component) knee 150V Vickers hardness of the protective layer under these film forming conditions) 1V (■
) was about 1500 Kg/mm2, and the film thickness was about 1 μm.

81 Example 3 An electrophotographic photoreceptor of Example 3 was produced in exactly the same manner as in Example 1, except that the film forming conditions for carbon or a protective layer containing carbon as a main component were changed to the following.

[Protection M film forming conditions]

NF3 flow rate: 50 SCCMC2■1
4 Flow rate: 150 SCCMCC property
: 0.03 torr first alternating voltage output :
400u (13,56Mtlz) bias voltage (DC) knee 300V Vickers hardness of the protective layer 1 (v (I
I) is approximately 2000Kg/mm'', and the film thickness is approximately 1μm
Met.

Example 4 An electrophotographic photoreceptor of Example 4 was produced in exactly the same manner as in Example 1, except that the film forming conditions for carbon or a protective layer containing carbon as a main component were changed to the following.

[Protective layer forming conditions]

NF3 flow rate: 50 SCCMC,,H
4 Flow rate: 150 SCCMCC property
:O, O], torr first alternating voltage output:
400W (13,56M1(z) bias voltage (DC component) knee 500V Vickers hardness of the protective layer under these film forming conditions Hv(n)
was about 2500 Kg/mm2, and the film thickness was about 1 μm.

Comparative Example An electrophotographic photoreceptor of Comparative Example 1 was prepared in exactly the same manner as in Example 1, except that the film forming conditions for carbon or a protective layer containing carbon as a main component were changed to the following.

[Protective layer forming conditions]

NF3 flow rate: 50 SCCMC, H4
Flow rate: 150 SCCMCC
:0.05torr first alternating type extrusion crab 40
0W (13,56M) Iz) bias voltage (DC component) 2 to 600V Vickers hardness Hv (II
) is about 3000Kg/mm2, and II! A thickness is approximately 1
It was μm.

The adhesive strength of the surface protective layer of the photoreceptor thus produced was evaluated by the following method (tape peel test 1~).

That is, an adhesive tape (Scotch Mending Tape 810, manufactured by Jujutsu 3M Co., Ltd.) was applied to the surface of the photoreceptor and then peeled off to evaluate whether the surface protective layer would peel off. The results are shown in Table-].

As is clear from the above results, the Vickers hardness difference Δltv between the organic photosensitive layer and the surface protective layer is 2500 kg/m.
It can be seen that when the thickness exceeds m2, the adhesiveness of the surface protective layer decreases.

Furthermore, as a result of mounting these photoreceptors in an actual copying process (laser printer) and repeatedly taking images,
In the photoreceptor of Comparative Example 1, fine cracks appeared in the protective layer after 2000 sheets were printed, and peeling gradually became observed in the circumferential direction. In addition, abnormal images such as black stripes began to appear, making it unsuitable for practical use.

On the other hand, no peeling or cracking was observed in the photoreceptors of Examples 4 to 4, and good image quality was maintained even after more than 20,000 sheets were printed.

The amount of decrease in the thickness of the surface protective layer after 20,000 sheets was evaluated using a precision level difference meter, and the results are shown in Table 2.

Table 2 [Effects of the Invention] The electrophotographic photoreceptor of the present invention is characterized by the fact that the difference in Vickers hardness between the organic photosensitive layer and the carbon or carbon-based protective layer is limited to 2500 Kg/mm2' or less. Unlike conventional products, the protective layer does not peel off or cracks occur, so good copy images can be formed even after repeated use, and its durability is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the structure of the electrophotographic photoreceptor of the present invention, and FIGS. 2(a) and 2(b) are schematic sectional views showing the structure of another embodiment. FIG. 3 is an explanatory diagram of an example of a plasma CVD apparatus used in forming a surface protective layer, and FIG. 4 is a plan view of a frame structure (2) of the plasma CVD apparatus. DESCRIPTION OF SYMBOLS 1... Support, 2... Undercoat layer, 3. Charge generation layer, 4... Charge transport layer, 5. Surface protective layer, 6. Photosensitive layer (single layer type).

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor having a structure in which at least an organic photosensitive layer and a surface protective layer are laminated on a conductive support,
The surface protective layer contains carbon or carbon as a main component, and the difference in Vickers hardness between the surface protective layer and the organic photosensitive layer ΔHv is 2.
A photoreceptor for electrophotography, characterized in that it is 500Kg/mm^2 or less.