JP3057196B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member having a surface protective layer on an organic photosensitive layer.

(Prior art)

Conventionally, as a photoreceptor used in an electrophotographic system, a photoconductive layer mainly composed of selenium or a selenium alloy is provided on a conductive support, and inorganic photoconductive materials such as zinc oxide and cadmium sulfate are used. Are generally known, such as those in which organic photoconductive materials such as poly-N-vinylcarbazole and trinitrofluorenone or azo pigment are used, and those using amorphous silicon-based materials. I have.

By the way, generally, the “electrophotographic method” means that a photoconductive photoreceptor is first charged in a dark place, for example, by corona discharge, and then exposed to an image, and the electric charge of only the exposed portion is selectively dissipated to electrostatic latent image. An image is formed by developing an image and developing the latent image with visualization fine particles (toner) composed of a coloring material such as a dye or a pigment and a binder such as a polymer substance to form an image. It is one of the laws.

The basic characteristics required of the photoreceptor in such an electrophotographic method are as follows: (1) The photoreceptor can be charged to an appropriate potential in a dark place.

(2) Dissipation of electric charge in a dark place is small.

(3) The charge can be quickly dissipated by light irradiation.

And the like.

Each of the above photoreceptors has excellent characteristics and disadvantages in practical use in addition to these basic characteristics. Among them, in recent years, the production cost is low, the environmental pollution is low, and the relatively free photoreceptor is used. Organic photoconductors have been remarkably developed for reasons such as design.

Generally, 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 and charge generation layer (CGL) with charge generation function, charge transport layer (CT with charge retention and transport function of charge injected from CGL)
L), and a function-dispersed type in which a layer having a function of preventing charge injection from the support or preventing reflection of light on the support as necessary is known. Have been.

These organic photoreceptors have excellent characteristics as described above, but because of the organic material, the surface hardness is low,
There is also an essential drawback that abrasion and scratches are likely to occur due to mechanical loads received from a developer, transfer paper, a cleaning member, and the like during actual use in a copying process.

This abrasion of the photosensitive layer causes a decrease in the charging potential,
Local flaws cause streak-like abnormal images on a copy, and are all important problems that affect the life of the photoconductor.

In order to solve such disadvantages, a method has been proposed in which a protective layer is provided on the surface of the organic photosensitive layer to improve the durability against the mechanical load applied 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), a method of providing an inorganic oxide (Japanese Patent Publication No. 43-014517), a method of providing an adhesive layer and then laminating an insulating layer (Japanese Patent Publication No. 43-027591), or plasma CVD method, optical C
A method of laminating an a-Si layer, an s-Si: N: H layer, an a-Si: O: H layer and the like by a VD method or the like (Japanese Patent Laid-Open Nos. 57-179859 and 59-0584).
37) is disclosed. In recent years, the application of a high hardness diamond-like carbon film to a protective layer has been activated.

For example, a photosensitive layer provided with a protective layer made of amorphous carbon or hard carbon (Japanese Patent Application Laid-Open No. 60-249155), and a protective layer provided with a diamond-like carbon protective layer on the outermost surface (Japanese Patent Application Laid-Open No. Sho 61-249155)
-255352), a high-hardness insulating layer containing carbon as a main component formed on a photosensitive layer (Japanese Patent Application Laid-Open No. 61-264355), or a nitrogen atom, oxygen atom, halogen atom, alkali metal atom or the like on an organic photosensitive layer. Provided with a protective layer comprising a plasma organic polymer film containing at least atoms (Japanese Patent Application Laid-Open No. 63-97961)
4), alkogen atom, group III atom, IV
One provided with a protective layer made of an amorphous hydrocarbon film generated by glow discharge containing at least an atom such as a group atom or a group V atom (Japanese Patent Application Laid-Open No. 63-220166-9).

Each of these proposals is based on a carbon-based high-hardness thin film (i-carbon film or i-carbon film) formed on the surface of an organic photosensitive layer by an ion process (sputtering, plasma CVD, glow discharge decomposition, photo CVD, etc.). Diamond-like carbon film).

The photoreceptor obtained by such a method has an improved surface hardness of the organic photosensitive layer and is excellent in durability. However, the adhesion between the protective layer and the organic photosensitive layer is not sufficient, and the Subsequent research revealed that the protective layer and the organic photosensitive layer were separated at the interface, and the durability in practical use was not so much improved.

[Problems to be solved by the invention]

The present invention has been made to exactly solve these problems, and its purpose is to improve the adhesion between an organic photosensitive layer and a protective layer composed of a thin film of high hardness containing carbon or carbon as a main component. It is an object of the present invention to provide an electrophotographic photoreceptor having improved durability and excellent durability over a long period of time.

[Means for solving the problem]

According to the present invention, an organic photosensitive layer on a conductive support,
In the electrophotographic photoreceptor having a surface protective layer on the organic photosensitive layer, the surface protective layer is mainly composed of carbon or carbon, and has an absorption coefficient K for light of 480 nm and a thickness d thereof.
(Μm), wherein K ≦ 4.0 × e− ^{0.3 × d} is provided.

The present inventors have proposed that an electrophotographic photoreceptor having a carbon or carbon-based surface protective layer provided on an organic photosensitive layer causes cracks in the surface protective layer or peeling from the photosensitive layer due to repeated use. As a result of diligent studies on the phenomena that occur, such development shows that the extinction coefficient K of the surface protective layer and its thickness d
I found something close to me.

That is, the extinction coefficient K and the thickness d of the protective layer are K ≦ 4.0 ×
e The electrophotographic photoreceptor uses carbon or carbon mainly satisfying the relationship of ^{(−0.3 × d) and} a thin film as a surface protective layer, and the surface protective layer has no crack even after long-term use. The inventors have found that there is no peeling phenomenon at the interface of the protective layer, and have completed the present invention. Here, the extinction coefficient K is defined by the following equation: K = 1nT ^-1 / d [K: extinction coefficient (μm ^-1 ) for light of 480 nm T: transmittance at 480 nm d = film thickness (μm)] Experimental Can be calculated as follows.

The present inventors prepared photoconductors in which the extinction coefficient K and the thickness d of the protective layer were variously changed, and observed the peeling state of the protective layer. As a result, as shown in FIG. 5, K ≦ 4.0 × e
It has been found that carbon or a protective layer containing carbon as a main component that satisfies the relationship of ^{−0.3 × d} does not have cracking or peeling. The extinction coefficient K and the thickness d of the protective layer are K> 4.0 × e.
^If it is ^{−0.3 × d} , the peeling and cracking of the protective layer become remarkable as shown in FIG. 5, and the intended object of the present invention cannot be achieved.

 Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of an electrophotographic photoreceptor of the present invention, in which an undercoat layer 2, a charge generation layer 3, a charge transport layer 4, and a surface protection layer 5 are sequentially provided on a conductive support 1. It has become. 2 (a), (b), (c) and (d) show examples of the configuration of an electrophotographic photoreceptor according to another embodiment of the present invention.

FIG. 2A shows a configuration in which an intermediate layer 6 is provided between the charge transport layer 4 and the surface protective layer 5 in the first receiving.
FIG. 2B shows a single-layer type photosensitive layer 7 instead of the function-separated type photosensitive layer in FIG. FIG. 2 (c) shows the second
FIG. 2 (b) shows an intermediate layer 6 interposed between the single-layer type photosensitive layer 7 and the surface protective layer 5, and FIG. 2 (e) shows the charge transport layer 4 directly on the conductive support 1. , And the charge generation layer 3, the intermediate layer 6, and the surface protection layer 5 are sequentially laminated thereon.

FIG. 2 (d) shows a structure in which the charge transport layer 4 is provided directly on the conductive support 1, and the charge generation layer 3 and the surface protection layer 5 are further provided in this order. FIG. 2 (e) shows a structure in which a charge transport layer 4 is provided directly on the conductive support 1, and a charge generation layer 3, an intermediate layer 6 and a surface protection layer 5 are sequentially laminated thereon.

As the conductive support used in the present invention, a conductor or an insulator subjected to a conductive treatment, for example, Al, Ni, Fe, C
In addition to metals such as u and Au or their alloys, thin films of metals such as Al, Ag and Au or conductive materials such as In ₂ O ₃ and SuO ₂ are formed on insulating substrates such as polyester, polycarbonate, polyimide and glass. Those formed, paper or the like subjected to a conductive treatment can be used.

The shape of the conductive support is not particularly limited, and any of a plate shape, a drum shape, and a belt shape can be used.

An undercoat layer provided as needed between the conductive support and the photosensitive layer further improves the effects of the present invention, and is provided for the purpose of improving adhesiveness.
l ₂ O ₃ , silane coupling agent, titanium coupling agent,
Inorganic materials such as chromium coupling agents and polyamide resins,
An alcohol-soluble polyamide resin, water-soluble polyvinyl butyral, polyvinyl butyral, a binder resin having good adhesiveness such as PVA, and the like are used. In addition, those obtained by dispersing ZnO, TiO ₂ , ZnS, and the like in the resin having good adhesiveness can also be used. As a method for forming the undercoat layer, a method such as sputtering or vapor deposition is used when an inorganic material is used alone, and a usual coating method is used when an organic material is used. The thickness of the undercoat layer is suitably 5 μm or less.

As the organic photosensitive layer provided directly or via an undercoat layer on the conductive support, either a single layer type or a function separation type can be applied.

Examples of the single-layer type photosensitive layer include dye-sensitized photoconductive powders such as zinc oxide, titanium oxide, and zinc sulfate, selenium powder, amorphous silicon powder, squaric salt pigment, phthalocyanine pigment, azulhenium salt. Pigments, azo pigments and the like, if necessary, together with a binder resin and / or an electron-donating compound described below, or a eutectic chain formed from a pyrylium dye and a bisphenol A-based polycarbonate Examples include a composition using a composition to which an electron donating compound is added. As the binder resin, the same resin as the function-separated type photosensitive layer described later can be used. The thickness of the single-layer type photosensitive layer is suitably from 5 to 30 μm.

On the other hand, a charge generation layer (CG
L) and a charge transport layer (CTL) are exemplified.

The charge generation layer (CGL) for generating and separating latent image charges by image exposure is prepared by dispersing or dissolving inorganic photoconductive powders such as crystalline selenium and arsenic selenide or organic dyes and pigments in a binder resin. Is used.

Examples of organic dyes and pigments as charge generating substances include, for example, C.I. Pigment Blue 25 (color index (CI) 21180) and C.I. Pigment Red 41 (CI 2120).
0), CI Acid Red 52 (CI 45100), CI Basic Red 3 (CI 45210), phthalocyanine pigments having a porphyrin skeleton, azulhenium salt pigments, squaric salt pigments, and azo pigments having an arazole skeleton (JP-A-53 95033), an azo pigment having a styrylstilbene skeleton (JP-A-53-138229).
Azo pigments having a triphenylamine skeleton (described in JP-A-53-132547), azo pigments having a dibenzothiophene skeleton (described in JP-A-54-21728), oxadiazole Azo pigments having a skeleton (described in JP-A-54-12742), azo pigments having a fluorenone skeleton (described in JP-A-54-22834), and azo pigments having a bisstilbene bone (described in JP-A-54-12742) 17733), azo pigments having a distyryloxadiazole skeleton (described in JP-A-54-2129), and azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-1734).
And triazo pigments having a carbazole skeleton (described in JP-A-57-195767 and JP-A-57-195768), and CI Pigment Blue 16 (CI 741).
Phthalocyanine-based pigments such as 00), indigo-based pigments such as C-I Bad Brown 5 (CI 73410), C-I Bad Dye (CI 73030), Argo Scarlet B (manufactured by Bio Red), Indus Scarlet R (manufactured by Bayer), etc. And the like can be used.

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

The binder resin is used in an amount of 0 to 1 based on 100 parts by weight of the charge generating substance.
It is suitable to use 00 parts by weight, preferably 0 to 50 parts by weight.

Examples of the binder resin used in combination with these organic dyes and pigments include condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polycarbonate, and polyether, and polystyrene, polyacrylate, polymethacrylate, poly-N-vinylcarbazole, and polyvinyl butyral. , Styrene-butadiene copolymer, styrene-
Adhesive and insulating resins such as polymers and copolymers such as acrylonitrile copolymers are included.

The charge generation layer, if necessary, with a binder resin, together with a binder resin, using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, or dichloroethane to be dispersed by a ball mill, an attritor, a side mill, or the like.
It can be formed by appropriately diluting the dispersion and applying it. The coating can be performed by 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 μm, and preferably 0.1 to 2 μm.

In the present invention, when particles such as 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 in combination. Examples of such an electron donating substance include polyvinyl carbazole and derivatives thereof (for example, those having a carbazole skeleton having a halogen such as chlorine or bromine, a substituent such as a methyl group or an amino group), polyvinyl pyrene, oxadiazole, pyrazoline, and hydrazone. And nitrogen-containing compounds such as diarylmethane, α-phenylstilbene, and triphenylamine compounds, and diarylmethane compounds, and polyvinyl carbazole and its derivatives are particularly preferable. These substances can be used even if they are mixed. In this case, it is preferable to add another electron donating organic compound to polyvinyl carbazole and its derivative. The content of such an inorganic charge generating substance is suitably from 30 to 90% by weight of the whole layer. When using an inorganic charge generation material, the thickness of the charge generation layer is 0.2 to
5 μm is appropriate.

The charge transport layer (CTL) is a layer for retaining a charged charge and moving the charge generated and separated in the charge generation layer by exposure to combine with the held charged charge. High electrical resistance is required to achieve the purpose of retaining the charged electric charge, and in order to achieve the purpose of obtaining a high surface potential with the retained charged electric charge, a low dielectric constant and good charge mobility are required. Required.

The charge transport layer for satisfying these requirements is composed of a charge transport material and a binder resin used as needed. That is, a charge transport layer can be formed by dissolving or dispersing the above substances in an appropriate solvent, and applying and drying the same.

The charge transport materials include a hole transport material and an electron transport material.

Examples of the hole transport material include poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethylglutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, and oxazine. Azole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazolin, phenylhydrazones, α- Electron donating substances such as phenylstilbene derivatives;

Examples of the electron transporting material include chloranil, bromanil, tetracyanoethylene, tetracyanoquinonedimethane, 2,4,7-trinitro-9-fluorenone,
2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-
Tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b]
Electron accepting substances such as thiophenone-4-one and 1,3,7-trinitrodibenzothiophenone-5,5-dioxide are exemplified.

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

The binder resin used as needed includes 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, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy Thermoplastic resins or thermosetting resins such as resins, melamine resins, urethane resins, phenolic resins, and alkyd resins.

As the solvent, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride and the like are used.

The thickness of the charge transport layer is suitably about 5 to 100 μm.
Further, 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 amount of the plasticizer is suitably about 0 to 30% by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methyl phenyl silicone oil are used.
A suitable amount is about weight%.

These CGL and CTL are placed on the support from the support side.
Or CTL and CGL in this order.

In the present invention, the protective layer provided on the outermost surface is made of carbon or carbon as a main component, and the above K ≦ 4.0 ×
e, satisfying the relationship of ^{−0.3 × d} , more preferably having a CC bond similar to diamond having an SP ³ orbit, a Vickers hardness of 100 to 3000 kg / cm ² , and a specific resistance (specific resistance). It is formed of a thin film having a value of 1 × 10 ⁷ to 1 × 10 ¹³ Ω · cm, and having an optical energy bandwidth (Eg) of 1.0 eV or more, and having a light-transmitting property in the infrared or visible region. .

Such films are generally prepared by sputtering, plasma CV
D, formed by glow discharge decomposition method, photo-CVD method, etc., the film forming method is not particularly limited, plasma CV
A protective layer having good characteristics can be obtained by a method in which the film is formed with a sputtering effect while being the D method. As a typical example, a patent application filed by the present inventor “Composite having a carbon coating and a method for producing the same” (Japanese Patent Application No. 56-146929, filed on September 17, 1981, Japanese Patent Application Laid-Open No. 58-4960)
9).

In this method, a substrate is arranged on one electrode (cathode side) of a parallel plate type plasma CVD apparatus, and is deposited on the upper surface of a flat surface by using a self-bias. Strongly excites a high-hardness carbon film.

The above method is preferably applied when the substrate has a sheet shape. For example, according to a plasma CVD apparatus as shown in FIG. 3, a similar protective layer is formed without being formed in a support shape. It is possible.

In the figure, (7) is a vacuum chamber of the plasma CVD apparatus, and a load / unload spare chamber (7 ') is operated by a gate valve (9).
It is divided. The inside of the vacuum chamber (7) is evacuated by an exhaust system (20) [consisting of a pressure regulating valve (21), a turbo molecular pump (22), and a rotary pump (23)], and is maintained at a constant pressure. ing. A reaction tank (50) is provided in the vacuum tank (7). The reaction tank was formed so as to cover a frame structure (2) (having a square or hexagonal shape as viewed from the electrode side) as shown in FIGS. 4 (A) and 4 (B) and openings at both ends thereof. A hood (8) (8 '), and a pair of first and second electrodes (3) (3') having the same shape and disposed on the hood (8) (8 ') (a metal mesh such as aluminum). Is used).
Reference numeral (30) denotes a gas line to be introduced into the reaction tank (50). Various gas containers as shown below are connected to the reaction tank (50) through the flow meter (29) and the nozzle (25).
0) is introduced.

Carrier Gas: H _2, Ar, etc. material gas: hydrocarbons gas (methane, ethylene, etc.) Additives _{Gas: NF 3, NH 3, PH} 3, B 2 H 6 or the like etching gas: O _2, etc. frame structure (2 3), the support (1) [(1-1), (1-2),... (1-n)] on which the organic photoconductive layer is formed is provided as shown in FIGS. 3 (A) and 3 (B). Be placed. The respective supports are arranged as third electrodes as described later.

A pair of electrodes (15) [(15-1) and (15-) for applying a first alternating voltage to the electrodes (3) and (3 '), respectively.
2)] is facilitated. The frequency of the first alternating voltage is 1
~ 100MHz.

Each of these power supplies has a matching transformer (16-
1) Connect to (16-2). The phase in this matching transformer is adjusted by a phase adjuster and can be supplied 180 ° or 0 ° from each other. That is, it has a symmetric 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. The output middle point (5) of the transformer is kept at the ground level. Further, the midpoint (5) and the third electrode, ie, the support (1) [(1-1), (1-2),.
_n )) or a power supply (17) for applying a second alternating voltage between the holders (2) electrically connected to them. The frequency of this second alternating voltage is 1-500KHz
It is.

Thus, a plasma is generated between the first and second electrodes (3) and (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 emitted to the outer space (6) outside, and the plasma potential in the reaction space is uniform. It has become. The reaction gas introduced into the reaction space through the nozzle (25) is decomposed by the energy of the plasma and accelerated by a negative self-bias (−10 to −600 V) applied to the support by the second alternating voltage, Since the film is formed while being sputtered on the support, 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 1 kW in the case of a frequency of 13.56 MHz, and the output of the second alternating voltage applied to the third electrode or the support is 15
At a frequency of 0 KHz, it is about 100 W.

The reaction gas to be used typically includes the ratio is ethylene and NF ₃ is _{NF 3 / C 2 H 4 =} 1 / 20~4 / 1, the vacuum chamber pressure during reaction is 0.01~1.0torr .

By such a method, ethylene or NF ₃ is decomposed in a plasma to form a diamond-like thin film to which N and F are added on a support (also referred to as DLC. Alternatively, a coating containing carbon as a main component is obtained.

Further, in this film forming method, physical properties (hardness, light transmittance, specific resistance, etc.) of the obtained film can be relatively freely changed by changing film forming conditions such as a reaction pressure and a mixing ratio of a reaction gas. . In particular, the hardness can be greatly changed by the negative self-bias applied to the support and the reaction pressure. In addition, this method does not require any special heating of the support, and can form a coating containing carbon or carbon as a main component at a low temperature of 150 ° C or less, thus protecting the organic photosensitive layer with low heat resistance without any problem. It is possible to deposit a layer.

The thickness of the protective layer mainly composed of carbon or carbon is 10
It is from 0 ° to 10 µm, preferably from 1000 ° to 2 µm.

Additives such as fluorine, halogen, nitrogen, phosphorus, and boron can be added to the protective layer containing carbon or carbon as a main component, if necessary, and its concentration is uniform in the depth direction of the film. Alternatively, a gradient may be provided.

〔Example〕

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

Example 1 An undercoat layer-forming solution prepared by dispersing a mixture having the following composition ratio on an aluminum cylindrical support (outer diameter 40 mmφ, length 250 mm) by a ball mill for 12 hours has a thickness of about 2 μm after drying.
Was applied by an immersion method to form an undercoat layer.

(Undercoat layer forming liquid)

TiO ₂ (Taipage manufactured by Ishihara Sangyo Co., Ltd.) 1 part by weight Polyamide resin (CM-8000 manufactured by Toray Co., Ltd.) 1 part by weight Methanol 25 parts by weight Dip coating of the underlayer with a charge generation layer coating solution having the following formulation, After drying at 120 ° C. for 10 minutes, a charge generation layer having a thickness of about 0.15 μm was formed.

(Charge generation layer coating solution)

A 15 cmφ glass pot was charged with 1% φ alumina sintered ball of 溶 of the volume, 300 g of a 2.7 wt% cyclohexanone solution of a polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) and the following azo pigment, and milled for 72 hours. . Further, additional 500 g of methyl ethyl ketone was added and milling was further performed for 24 hours to obtain a charge generating layer coating liquid.

Next, a charge transport layer coating solution having the following formulation was applied onto the charge generation layer by dip coating so that the film thickness after drying was about 20 μm, thereby providing a charge transport layer.

Thereafter, the above-described plasma shown in FIG. 3 is applied to the organic photosensitive layer.
Using a CVD apparatus, carbon and carbon as main components (a-C:
(N: F: H type) The protective layer was formed under various film forming conditions shown in Table 1 to prepare various photoconductors.

At this time, in order to measure the extinction coefficient K and the thickness d of the protective layer,
A quartz glass (manufactured by Daiken Quartz Co., Ltd.) having an outer dimension of 10 × 30 × 0.5 ton was placed on the frame structure (2) in the same manner as the organic photosensitive layer, and a film was formed at the same time.

The film forming conditions were as follows. First, the inside of the vacuum chamber (7) was evacuated to a high vacuum of 1 × 10 ⁻⁵ torr or less, then the gas valve (28) was opened, and the flow rates of C ₂ H ₄ gas and NF ₃ gas were 150 SCCM and 50 SCCM, respectively. The flowmeter (29) was set so as to be, and introduced into the reaction tank (50).

Thereafter, under the conditions of the reaction chamber pressure, the film formation time, and the bias voltage (DC component) applied to the substrate shown in Table 1, carbon and a film containing carbon as a main component were formed on the organic photosensitive layer and the quartz glass plate. A film was formed.

However, the reaction chamber pressure is adjusted by the pressure adjustment valve (21),
The applied first alternating power was 200 W and the frequency was 13.56 MHZ.
z, the frequency of the second alternating voltage for applying a bias to the substrate was 150 KHz.

The extinction coefficient K and the thickness d of the protective layers of the 15 comparative samples thus prepared were measured as follows.

Absorption coefficient K = 1nT ^-1 / d [T is the transmittance at 480 nm and is measured by a spectrophotometer (Hitachi: Hitachi Double Beam 228). d is a film thickness (μm), which is measured by a stylus type film thickness meter (DENTAK IIA manufactured by SLOAN). Further, the adhesive strength of the surface protective layer of the obtained photoreceptor was evaluated by the following method.

That is, an adhesive tape (manufactured by Sumitomo 3M Ltd .: Scotch Mending Tape 810) was applied to the surface of the photoreceptor, and then peeled off.

 The results are shown in Table 1.

FIG. 5 shows the result as a graph.

From this, even if the extinction coefficient is the same, peeling of the protective layer occurs due to the increase in the film thickness d, and even if the film thickness is the same, the peeling occurs with the increase in the extinction coefficient. K
And the extinction coefficient K
(480 nm) and the thickness d (μm) are K ≦ 4.0 × e.
^{When −0.3 × d} is satisfied, it can be seen that peeling does not occur on the surfaces of the aC: N: F: H-based protective layer and the organic photosensitive layer.

Example 2 An undercoat layer-forming liquid prepared by dispersing a mixture having the following composition ratio on an aluminum cylindrical support (outer diameter 40 mmφ, length 250 mm) by a ball mill for 12 hours has a thickness of about 2 μm after drying.
Was applied by an immersion method to form an undercoat layer.

(Undercoat layer forming liquid)

TiO ₂ (Taipage manufactured by Ishihara Sangyo Co., Ltd.) 1 part by weight Polyamide resin (CM-8000 manufactured by Toray Co., Ltd.) 1 part by weight Methanol 25 parts by weight Dip coating of the underlayer with a charge generation layer coating solution having the following formulation, After drying at 120 ° C. for 10 minutes, a charge generation layer having a thickness of about 0.15 μm was formed.

(Charge generation layer coating solution)

After the above mixture is dispersed in a ball mill for 72 hours, the mixture is further diluted with 500 parts by weight of a mixed solvent of cyclohexanone: methyl ethyl ketone = 1: 1 (weight ratio).

Next, a charge transport layer coating solution having the following formulation was applied onto the charge generation layer by dip coating so that the film thickness after drying was about 20 μm, thereby providing a charge transport layer.

(Charge transport layer coating solution)

Further, carbon and carbon as a main component (a-C: N: F: H) are formed thereon by a plasma CVD method using the apparatus shown in FIG.
System) A protective layer was formed to obtain a photoreceptor of Example 2. Also, to measure the thickness and absorbance of the protective layer, the outer dimensions are 10 × 30 × 0.5t
A protective layer was formed on quartz glass (manufactured by Daiken Quartz Co., Ltd.) under exactly the same conditions as for the organic photosensitive drum to monitor the film thickness and the extinction coefficient.

The conditions were exactly the same as in Example 1 except that the film forming conditions were as follows: internal pressure: 0.01 Torr, bias voltage: -400 V, and film forming time: 50 minutes. Further, the method of measuring the extinction coefficient and the film thickness of the protective layer formed on quartz glass was the same as in Example 1.

The photoreceptor of Example 2 thus produced was mounted on an actual electrostatic copying process (laser printer) and repeatedly imaged, and as a result, a good initial image was obtained.
No abnormalities such as cracks and peeling were observed even after 100,000 sheets of images were collected, indicating that good image quality was maintained.

The film thickness and extinction coefficient of the film on the quartz glass, which is a film thickness and extinction coefficient monitor, were measured. As a result, the film thickness d: 1.0 μm, the absorption coefficient K: 1.7 (μm) ⁻¹ , The coefficient K is K ≦ 4.0 × e− ^{0.3 × d}
I was satisfied with the relationship.

〔The invention's effect〕

In the electrophotographic photoreceptor of the present invention, carbon or a thin film containing carbon as a main component whose extinction coefficient K and film thickness d satisfy the relationship of K ≦ 4.0 × e ^{(−0.3 × d)} are used as the surface protective layer. Therefore, unlike the conventional product, the protective layer does not peel off, so that a good copied image can be formed even when used repeatedly, and the durability is remarkably excellent.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of an electrophotographic photoreceptor of the present invention, and FIGS. 2 (a), (b), (c), (d) and (e) show other embodiments. FIG. 2 is a schematic cross-sectional view showing a configuration. FIG. 3 shows a plasma CV used for forming the surface protective layer.
FIG. 4 is an explanatory view of an example of the D apparatus, and FIG. 4 is a plan view of a frame structure (2) of the plasma CVD apparatus. FIG. 5 is a graph showing the relationship between the extinction coefficient K of the protective layer—the film thickness d and the peeling state of the protective layer. DESCRIPTION OF SYMBOLS 1 ... Support, 2 ... Undercoat layer, 3 ... Charge generation layer, 4 ...
... charge transport layer, 5 ... surface protective layer, 6 ... intermediate layer, 7 ...
... Photosensitive layer (single-layer type).

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Nagame 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Mitsuru Seto 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (72) Inventor Shunpei Yamazaki 398 Hase, Atsugi City, Kanagawa Prefecture Inside Semiconductor Energy Laboratory Co., Ltd. (72) Inventor Shigenori Hayashi 398 Hase, Atsugi City, Kanagawa Prefecture Inside Semiconductor Energy Laboratory Co., Ltd. (56) References JP-A-64-20558 (JP, A) JP-A-1-130663 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member having an organic photosensitive layer on a conductive support and a surface protective layer on the organic photosensitive layer, wherein the surface protective layer contains carbon or carbon as a main component,
And the absorption coefficient K for light of 480 nm and its thickness d (μ
An electrophotographic photoconductor, wherein the relationship of m) is K ≦ 4.0 × e−3.0 ^{× d} .