JP2008180937A - Electrophotographic photoreceptor, method for manufacturing electrophotographic photoreceptor, and electrophotographic apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having high sensitivity to an exposure light source of a short-wavelength region, a method for manufacturing this electrophotographic photoreceptor, and an electrophotographic apparatus using this electrophotographic photoreceptor. <P>SOLUTION: The electrophotographic photoreceptor 50 is configured such that a nitrogen-containing metal oxide film is used as a charge generating layer 2 formed on a conductive support 1. The metal oxide constituting the charge generating layer 2 is formed by an aerosol deposition method optionally in an atmosphere of nitrogen or oxygen. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member using a metal oxide, and more particularly, an electrophotographic photosensitive member suitable for exposure with a short-wavelength laser light source capable of increasing the resolution of an image, and a method for producing the electrophotographic photosensitive member. And an electrophotographic apparatus using the same.

  As a photoconductive material for forming a photosensitive layer in an electrophotographic photosensitive member, it has a high sensitivity, a high S / N ratio, an absorption spectrum suitable for the spectral characteristics of an electromagnetic wave to be irradiated, a fast photoresponsiveness, and a desired dark resistance. Characteristics such as having a value and being harmless to the human body at the time of use and disposal are required.

  Various materials and configurations have been proposed for a long time to satisfy these performances and characteristics, but currently, organic photoconductors based on organic photoconductive substances and amorphous silicon-based materials are used for photoelectric materials. Two inorganic photoreceptors are mainstream. Briefly explaining the characteristics of these two types of electrophotographic photoreceptors, the former organic photoreceptor is highly productive and can be reduced in cost, but it cannot be said that the durability is sufficient. The latter amorphous silicon photoconductor has a very high durability, but requires an expensive vacuum apparatus and a complicated film forming technique, which increases the cost. Therefore, these electrophotographic photoreceptors are classified according to their price and performance, and organic photoreceptors are mainly used for medium and low speed machines, and amorphous silicon is mainly used for high speed machines. .

  In conventional electrophotographic apparatuses, a red semiconductor laser having an oscillation wavelength near 800 [nm] or 680 [nm] has been mainstream. This is because the red semiconductor laser to be used is excellent in characteristics and has been stably supplied at low cost. In recent years, there has been an accelerated demand for higher image quality of output images due to higher resolution, and one effective way to achieve this goal is to narrow the beam spot diameter using a short-wavelength laser. Since then, it has been desired to introduce an electrophotographic apparatus using this. However, to achieve this, two major problems must be solved. One is development of a short wavelength, that is, a blue semiconductor laser, and the other is development of an electrophotographic photosensitive member having high sensitivity at the wavelength.

  Short-wavelength semiconductor lasers are slower in development than long-wavelength semiconductor lasers in the red to near-infrared region, and have been far from practical use until recently. It has been put into practical use after 1150 hours continuous oscillation has been reported in semiconductor lasers, and is now being put into practical use by being mounted on products such as DVDs. For example, 400-415 [nm], 440-450 [nm], etc. Blue semiconductor lasers having a wavelength range have been mass-produced. Also, engineering samples of about 370 to 390 [nm], for example, are supplied, but they are very expensive and lack stability, and are currently mounted on an electrophotographic apparatus as an exposure light source. It ’s difficult.

  On the other hand, the development of an electrophotographic photosensitive member having a spectral absorption band (sensitivity range) at a wavelength of slightly over 400 [nm], which has already been mass-produced as described above, or a wavelength in the vicinity thereof is delayed compared to the development of a blue semiconductor laser. As described above, the electrophotographic photosensitive member is roughly classified into an organic photosensitive member and an inorganic photosensitive member, but due to the spectral absorption band, the electrophotographic photosensitive member for a blue semiconductor laser having a wavelength range of slightly over 400 [nm]. Therefore, it is difficult to use conventional materials as they are, and various devices have been made for the electrophotographic photosensitive member to cope with the blue semiconductor laser.

  In the organic photoreceptor, for example, by using a charge transport layer having a structure disclosed in (Patent Document 1), the energy of light absorbed by the charge transport layer is reduced, and sufficient energy is irradiated to the charge generation layer. To improve the sensitivity. Further, for example, gallium phthalocyanine or oxytitanium phthalocyanine disclosed in (Patent Document 2) or the like is used for the charge generation layer, thereby improving sensitivity at a short wavelength.

On the other hand, the amorphous silicon photoconductor, which is an inorganic photoconductor, has a lower photosensitivity than the long wavelength region, but has a higher photosensitivity in the short wavelength region than the organic photoconductor. It corresponds to a blue semiconductor laser by improvement in the process disclosed in (Patent Document 3) and the like. In addition to the above organic photoreceptors and amorphous silicon photoreceptors, there is a possibility that zinc oxide having high sensitivity characteristics at short wavelengths can be applied. Zinc oxide has been hardly seen at present as an electrophotographic photosensitive material, but it is inexpensive and non-toxic, such as plain paper electrophotographic photosensitive member or electrofax paper, in a structure dispersed with a resin binder. In the past, it was widely used as a photoconductor for electrophotographic photoreceptors. Since the electrophotographic photosensitive member in a dispersion system using zinc oxide is a binary material composed of zinc oxide and a resin, it has a drawback that it is severely deteriorated during the process and is easily influenced by the environmental atmosphere. At that time, short-wavelength semiconductor lasers were not put into practical use, and only long-wavelength semiconductor lasers were used, so in order to use zinc oxide having a spectral absorption band near 380 [nm] It is necessary to shift the spectral absorption band (sensitivity range) to the longer wavelength side by performing sensitization, chemical sensitization, dye sensitization, etc., and there are problems in characteristics and reliability. However, nowadays blue semiconductor lasers and blue light emitting diodes have been put into practical use, as disclosed in, for example, (Patent Document 4) and the like, by limiting the crystal structure of zinc oxide, it can be used alone without being dispersed. The charging characteristics and photosensitivity can be improved, and it can function as an electrophotographic photosensitive member.
JP 2000-105475 A JP 2000-105479 A JP 2002-311693 A JP 2001-022110 A

  As described above, in order to be compatible with the electrophotographic apparatus using an exposure light source in the blue region, that is, a short wavelength, each electrophotographic photosensitive member has been improved uniquely, but still in various respects. Issues remain.

  In the organic photoreceptor, it is possible to have a spectral absorption band (sensitivity range) at a short wavelength by the techniques disclosed in (Patent Document 1) and (Patent Document 2), and an electron using a short wavelength exposure light source. Although it can be applied as a photoconductor for a photographic apparatus, since an organic material is used, it is more susceptible to external factors such as ozone, oxygen and moisture than an inorganic material, and has a problem in terms of durability.

  The amorphous silicon photoreceptor can improve sensitivity at a short wavelength by the technique disclosed in (Patent Document 3), and can be applied as a photoreceptor for an electrophotographic apparatus using a short wavelength exposure light source. In order to obtain an amorphous silicon film suitable for an electrophotographic photosensitive member, the process for accurately controlling the doping concentration is very complicated, and the source gas used in plasma CVD is silane, diborane or the like. Since it is a poisonous gas and an exhaust gas treatment system for detoxifying them is required, the associated increase in equipment costs is a problem.

  In an electrophotographic photoreceptor using zinc oxide, it is possible to achieve both charging characteristics and sensitivity by controlling the composition ratio and crystal structure of zinc oxide by the technique disclosed in (Patent Document 4). However, the spectral characteristics of zinc oxide itself have not been improved, and it cannot be said that it exhibits a sufficient function as a photoconductor for an electrophotographic apparatus using a mass-produced blue semiconductor laser.

  In addition to the above zinc oxide, metal oxides such as titanium oxide are semiconductor materials having an excellent photoelectric effect and have properties comparable to amorphous silicon in practical use. It can be applied as a charge generation layer or a charge transport layer of a photographic photoreceptor. However, these metal oxides have a wide band gap and a spectral absorption band only on the short wavelength side (as described above, near 380 [nm]), and thus have been generally used as an exposure light source for an electrophotographic apparatus so far. It was impossible to expose with the red semiconductor laser. In addition, it is difficult to obtain sufficient sensitivity even with a blue semiconductor laser having a peak wavelength of around 405 [nm] that is mass-produced. In order to apply the metal oxide having a wide band gap to the photosensitive layer of the electrophotographic photosensitive member, the spectral absorption characteristics must be improved, but it has been difficult with the conventionally disclosed techniques.

  In addition, when an inorganic material such as amorphous silicon or a metal oxide is used for an electrophotographic photosensitive member, there is a significant problem regarding the manufacturing method in addition to the characteristics of the film. As described above, in the case of amorphous silicon, plasma CVD is generally used. However, with this method, the film formation rate is at most several [μm / h], which is necessary for constituting an electrophotographic photosensitive member. Considering the film thickness to be about 20 [μm], a process time of about 10 hours is required. Further, there are various methods for forming a metal oxide, such as sputtering and ion plating, but these methods can only obtain a film formation rate comparable to that of the plasma CVD method. Therefore, even if a semiconductor laser having a shorter wavelength than the current 405 [nm] is put into practical use and the metal oxide can be sufficiently exposed, the problem regarding the manufacturing method that productivity is low remains. .

  As described above, with the conventional technology, it has been difficult to obtain an electrophotographic photosensitive member by an easy manufacturing process that has high sensitivity at a short wavelength, is excellent in durability, and is easy to manufacture.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrophotographic photosensitive member having high sensitivity to a light source having a short wavelength. Furthermore, the present invention provides a method for producing an electrophotographic photosensitive member that can be produced by a simple process in a short time. It is another object of the present invention to provide an electrophotographic apparatus that can obtain high resolution image quality by using this electrophotographic photosensitive member.

  The electrophotographic photoreceptor of the present invention comprises a support having at least a surface layer having conductivity and a charge generation layer composed of a metal oxide containing nitrogen on the support.

  According to the present invention, by adding nitrogen to a metal oxide having a wide band gap and having spectral sensitivity only on the short wavelength side such as 380 [nm], the spectral absorption characteristics on the short wavelength side are improved. It is possible to obtain an electrophotographic photosensitive member having sufficiently high sensitivity to the output light of a mass-produced blue semiconductor laser (the peak wavelength is slightly over 400 nm as described above).

  Also, in an electrophotographic apparatus using this electrophotographic photosensitive member, it is possible to use an exposure light source having a shorter wavelength than that of a conventional red semiconductor laser, so that high-resolution image quality can be obtained.

  Furthermore, by using an aerosol deposition method that can obtain an extremely high film formation rate compared to conventional film formation methods such as sputtering and ion plating, no complicated film formation process is required, In addition, the charge generation layer for the electrophotographic photoreceptor can be formed in a short process. This aerosol deposition method is a film formation method suitable for ceramics such as metal oxides, and can sufficiently derive the excellent performance of metal oxides. The photographic photoreceptor can exhibit excellent performance.

  The electrophotographic photoreceptor of the present invention comprises a support having at least a surface layer having conductivity and a metal oxide containing nitrogen as a charge generation layer on the support. As a result, the spectral absorption of the metal oxide (for example, having a sensitivity peak in the wavelength region of about 380 [nm]) serving as the charge generation layer can be shifted to the long wavelength side (for example, 405 [nm]). An electrophotographic photosensitive member having a high sensitivity to blue semiconductor lasers can be obtained.

  In the present invention, the main component of the metal oxide serving as the charge generation layer is zinc oxide or titanium oxide. High sensitivity can be realized by including nitrogen in a metal oxide having an excellent photoelectric effect such as zinc oxide or titanium oxide.

  The present invention also provides an electrophotographic photosensitive member having a structure in which a sufficient spectral absorption is given to an exposure light source having a blue wavelength. As a result, high sensitivity can be obtained even for a blue short wavelength light source.

  In the present invention, a protective film mainly composed of carbon is formed on the outermost surface of the electrophotographic photosensitive member. As a result, the carbon-based protective film having excellent wear resistance is arranged on the outermost surface, so that the durability is improved.

  In the method for producing an electrophotographic photoreceptor of the present invention, a metal oxide serving as a charge generation layer formed on a support having at least a surface layer having conductivity is formed in a nitrogen atmosphere. Thereby, nitrogen can be easily contained in the metal oxide film.

  In the method for producing an electrophotographic photosensitive member of the present invention, a metal oxide serving as a charge generation layer formed on a support having at least a surface layer having conductivity is formed by an aerosol deposition method. Accordingly, high productivity can be obtained with a simple process while maintaining excellent characteristics as the charge generation layer.

  In the present invention, oxygen is contained in the introduced gas used in the aerosol deposition method. As a result, oxygen deficiency due to reduction of the metal oxide can be prevented, and a decrease in charge generation capability can be prevented.

  In the present invention, nitrogen is contained in the introduced gas used in the aerosol deposition method. This has an effect that nitrogen can be easily contained in the metal oxide film.

  In the present invention, oxygen and nitrogen are contained in the introduced gas used in the aerosol deposition method. As a result, it is possible to easily achieve both prevention of oxygen deficiency due to reduction of the metal oxide film and nitrogen content in the film.

  In the present invention, the introduction gas used for the aerosol deposition method is divided into a first gas containing at least nitrogen and a second gas containing at least oxygen, and are switched alternately, so that the metal oxide of the same base material is changed. It is intended to be laminated. Although the same material is used, films with different performance can be obtained by switching the introduced gas. Therefore, a multilayer electrophotographic photosensitive member can be easily produced by simply switching the introduced gas in one chamber. High productivity can be obtained.

  In the present invention, after the charge generation layer and the charge transport layer are formed, heat treatment is further performed. Since stress relaxation by heat treatment and diffusion at the interface of each layer occur, characteristics such as charging property and carrier mobility are improved, and adhesion between layers (mechanical strength) is improved.

  The electrophotographic apparatus of the present invention is an electrophotographic apparatus having the above-described electrophotographic photosensitive member. Since the electrophotographic apparatus employing the electrophotographic photosensitive member according to the present invention can use a short wavelength light source as an exposure light source, high-resolution image quality can be obtained.

(Example 1)
Hereinafter, the present invention will be described in detail.

  FIG. 1 is a schematic diagram showing a layer structure of a laminated electrophotographic photoreceptor (hereinafter simply referred to as “photoreceptor”) 50 according to Embodiment 1 of the present invention. Note that the photoconductor 50 is usually configured in a drum shape or a belt shape, for example, and FIG.

  In the figure, 1 is a conductive support, 2 is a charge generation layer, 3 is a charge transport layer, and the charge generation layer 2 of Example 1 is composed of a metal oxide containing nitrogen. As the support 1, the support 1 itself has conductivity, for example, aluminum is representative, but other than that, aluminum alloy, copper, stainless steel, chromium, titanium, nickel, magnesium, indium, gold, Platinum, silver, iron or the like can be used. In addition, aluminum, indium oxide, tin oxide, gold, etc. are formed into a film by vapor deposition etc. on a dielectric substrate such as plastic, and conductive fine particles are mixed into plastic or paper. A thing etc. can be used. These conductive supports 1 are required to have uniform conductivity, and smooth surface properties are also important. The smoothness of the surface of the support 1 has a great influence on the uniformity of the charge generation layer 2 and the charge transport layer 3 formed thereon, so that the surface roughness is 0.5 [μm] or less. preferable.

  In many cases, the support 1 itself is made of a conductive metal material or the like to form a drum-shaped photoconductor 50. A resin material such as PET is used as the support 1, and a metal film is formed thereon. In many cases, the belt-shaped photoreceptor 50 is formed. For the sake of simplicity, the latter metal film is omitted in FIG. 1, but this metal film is also included in the support 1.

  In FIG. 1, the structure in which the charge generation layer 2 is formed directly on the support 1 is shown. However, an undercoat layer having an injection preventing function and an adhesion function is provided between the support 1 and the charge generation layer 2. (Not shown). As the undercoat layer, a material that exhibits a predetermined insulating performance and can control charge injection can be appropriately selected. Examples include casein, polyvinyl alcohol, nitrocellulose, polyvinyl butyral, phenol resin, polyamide, polyurethane, and gelatin. It is mentioned as a general material.

  As the charge transport layer 3, there are a material having an ability to transport electrons or a material having an ability to transport holes, which are used as appropriate. Examples of the hole transporting material include pyrene, carbazole, hydrazone, oxazole, oxadiazole, pyrazoline, arylamine, arylmethane, benzidine, thiazole, stilbene, and butadiene. Examples of low molecular organic compounds such as poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, pyrene-formaldehyde resin, ethyl Examples thereof include carbazole-formaldehyde resin, triphenylmethane polymer, polysilane, and the like.

  As an electron transport material, for example, organic compounds such as benzoquinone, tetracyanoethylene, tetracyanoquinodimethane, fluorenone, xanthone, phenanthraquinone, phthalic anhydride, diphenoquinone, Examples include inorganic materials such as amorphous silicon, zinc oxide, titanium oxide, and tin oxide.

  From the aspect of characteristics, various organic and inorganic materials can be used as the charge transport layer 3 as mentioned above as an example. From the viewpoint of reliability, as described above, It is preferable to use an inorganic material that is superior in mechanical strength.

In Example 1, a metal oxide containing nitrogen is used for the charge generation layer 2. Except for exceptional metal oxides such as lead oxide (PbO) and cadmium oxide (CdO), metal oxide materials are stable in the atmosphere, rich in resources, and are non-polluting materials. In addition, many materials have excellent semiconductor characteristics. Therefore, there are many merits in using this metal oxide as a main material of the photo-functional film of the photoconductor. In particular, zinc oxide (ZnO) and titanium oxide (TiO ₂ ) have the photoelectric effect necessary as a charge generating material of the photoconductor. Since it is a semiconductor material, the merit of using it for the charge generation layer 2 for the photoreceptor 50 is very large.

  Conventional metal oxides, for example, zinc oxide and titanium oxide described above have large band gaps of 3.3 eV and 3.2 eV, respectively, and a red semiconductor laser that has been used in the past and a blue semiconductor that has begun to be put into practical use. At the wavelength of the laser, the photoelectric effect that absorbs light energy and generates charges does not appear, and cannot be used for the charge generation layer 2 of the photoreceptor 50. However, as a result of various studies on the wavelength increase of the spectral absorption band of metal oxides, the present inventors have found that it is very effective to contain nitrogen.

  Regarding zinc oxide, it has been conventionally known that a certain length of wavelength can be achieved by adding Li, Pd, Cd, Cu, or the like (for example, JP 2000-321803). It is difficult to precisely control the additive elements with high reproducibility. This is because in the sputtering method and plasma spraying method using plasma, the composition of the target base material and the film to be formed do not necessarily match and a deviation occurs. The aerosol deposition method requires fine particles to form a film, but various restrictions are imposed on the production of fine particles to which additive elements such as Li, Pd, Cd, and Cu are added. The method of adding nitrogen that we found this time does not cause such problems, and it is easy and accurate to include a predetermined amount in the film by incorporating nitrogen into the gas introduced during film formation. Can be included.

  In the above description, the structure in which the charge generation layer 2 and the charge transport layer 3 are provided on the support 1 is described. However, the charge transport layer 3 is provided on the support 1 and the charge generation layer 2 is provided thereon. Even if the configuration is provided, good characteristics as the photoreceptor 50 can be obtained without any problem.

Conventionally, a method of forming a high-hardness protective layer on the outermost surface of the photoreceptor 50 is known, but it can be applied to the configuration of Example 1 as a matter of course. A suitable example is a case where carbon or a thin film composed mainly of carbon, especially diamond or diamond-like carbon film (DLC film) is used as a protective film. The DLC film is an amorphous structure in which diamond bonds and graphite bonds are mixed. Hydrocarbon gases such as methane, ethane, propane, and butadiene, hydrogen, fluorine (NF ₃ ), nitrogen (N ₂ ), It is manufactured using a vacuum film formation method such as a plasma CVD method, a photo CVD method, or a sputtering method while flowing boron (BF ₃ ) gas or the like. When a DLC film (not shown) is formed on the charge transport layer 3 as a protective film, the film formation rate, the substrate heating temperature, and the bias are considered in consideration of damage to the metal oxide film that becomes the charge transport layer 3. What is necessary is just to set optimal conditions in consideration of various film forming conditions such as voltage and the introduced gas to be used. In addition, the thickness of the protective film required is not particularly specified, but if it is too thick, the sensitivity as the photoreceptor 50 is generally lowered, and good image quality cannot be obtained. The film thickness is preferably 1 [μm] or less.

  FIG. 2 is a characteristic diagram showing the results of measuring the spectral absorption characteristics of zinc oxide in Example 1 of the present invention. For comparison, the spectral absorption characteristics of a zinc oxide film not containing nitrogen are also shown.

  Hereinafter, the zinc oxide film containing nitrogen, which constitutes the charge generation layer 2 which is the main element of the photoreceptor 50 in Example 1, will be described in detail.

In Example 1, zinc oxide constituting the charge generation layer 2 of the photoreceptor 50 was produced by sputtering under the following film formation conditions. The sample used for the measurement is made of quartz glass in order to avoid short-wavelength absorption, and a zinc oxide film is formed thereon under the following conditions.
Target: Purity 99.99% Zinc oxide introduction gas: Mixed gas of argon and nitrogen (nitrogen concentration 10%)
High frequency power density: 2.5 [W / cm ² ]
Substrate heating: Room temperature film thickness: 1 [μm]
Note that a zinc oxide film as a comparative example not containing nitrogen was produced under the same conditions as described above except that 100% argon gas was used as the introduced gas. In the following description, a zinc oxide film containing nitrogen is referred to as an “example”, and a zinc oxide film not containing nitrogen is referred to as a “comparative example”.

As is clear from FIG. 2, the zinc oxide film of the example produced in the mixed gas atmosphere of argon and nitrogen, which is an inert gas, is compared with the comparative example produced in the atmosphere of only the inert gas. It can be seen that the absorption in the long wavelength region is increased. In the figure, the horizontal axis represents the wavelength of the incident light, the vertical axis represents the logarithm, and is expressed as log (E _i / E _o ) with the incident light energy E _i and the transmitted light energy E _o . nm], light energy is absorbed with a high efficiency of 90% or more in this embodiment. On the other hand, it can be seen that the zinc oxide film prepared in an atmosphere of only an inert gas as a comparative example has almost no sensitivity to this wavelength.

  FIG. 3 is a characteristic diagram showing the results of measuring the energy state of electrons by X-ray photoelectron spectroscopy in Example 1 of the present invention.

  By this method, the amount of nitrogen contained in the zinc oxide film can be measured. The sample used for the measurement was the same as the example and comparative example shown in FIG. As can be seen from FIG. 3, the zinc oxide film of the example prepared in an inert gas + nitrogen atmosphere has a peak in the vicinity of a binding energy of 399 eV indicating the presence of nitrogen, but the atmosphere of only the inert gas of the comparative example No peak is observed in the vicinity of this binding energy in the zinc oxide film formed therein. That is, the zinc oxide film formed in an inert gas + nitrogen atmosphere contains nitrogen. Although the detailed mechanism by which the spectral absorption band shifts by adding nitrogen to zinc oxide has not been elucidated in detail, the effect of the nitrogen content in this film is due to the long spectral absorption characteristics shown in FIG. It is expected to contribute to wavelength conversion.

  FIG. 4 is a characteristic diagram showing the results of observing crystal structures of a zinc oxide film containing nitrogen and a zinc oxide film not containing nitrogen by X-ray diffraction.

  The crystal structure of the zinc oxide film of the example and the zinc oxide film of the comparative example are clearly different. In the comparative example, the (002) plane is predominantly oriented in the zinc oxide film, whereas in the examples, the (100) plane and the (110) plane are oriented in the (002) plane. This difference in orientation is considered to be one of the causes of the difference in spectral absorption characteristics between the two.

  As described in (Patent Document 4), the crystal structure of zinc oxide affects the sensitivity and the characteristics of the chargeable photoconductor. Naturally, such a change in crystal structure due to the inclusion of nitrogen greatly affects characteristics such as specific resistance and carrier mobility which influence the characteristics of the photoreceptor.

  As shown above, in the zinc oxide film containing nitrogen, the spectral absorption band shifts to the longer wavelength side, but on the other hand, it also affects the chargeability and carrier mobility. By optimizing the film formation conditions such as the nitrogen concentration, it is possible to obtain the photoconductor 50 having excellent performance that has not been conventionally available.

  The characteristics of the zinc oxide film containing nitrogen have been described for the case where the film is formed by the sputtering method, but it has been confirmed that the zinc oxide film formed by the aerosol deposition method described later has the same effect. Therefore, nitrogen can be contained in the film by adding nitrogen to the introduced gas.

  In addition, we confirmed the effect of nitrogen content on metal oxides other than zinc oxide, especially titanium oxide, as well as on zinc oxide. By incorporating nitrogen, it was possible to increase the wavelength of spectral absorption even in titanium oxide films. is made of. Therefore, a titanium oxide film containing nitrogen can also be applied to the charge generation layer of the photoreceptor.

(Example 2)
FIG. 5 is a schematic diagram showing a layer structure of a single-layer electrophotographic photoreceptor 50 according to the second embodiment of the present invention.

  The photoconductor 50 according to the present invention is not limited to the multilayer photoconductor 50 shown in the first embodiment, and it has been confirmed that the single layer photoconductor 50 has the same effect. .

  The single-layer type photoreceptor 50 must have both characteristics of charge generation ability and charge transport ability at the same time. The photosensitive layer 4 in Example 2 is obtained by mixing a metal oxide film containing nitrogen and a metal oxide film not containing nitrogen at the same time to obtain characteristics of both charge generation ability and charge transport ability. .

  In order to form the above two types of metal oxide films “simultaneously”, for example, when the nitrogen concentration of the introduced gas (mixed gas of inert gas and nitrogen) introduced into the film forming apparatus is relatively lowered Good. By doing in this way, the film | membrane formed as the photosensitive layer 4 is formed in the state in which the metal oxide containing nitrogen and the metal oxide which does not contain nitrogen were mixed.

  Also in Example 2, for example, zinc oxide or titanium oxide can be suitably used as the metal oxide.

  Now, “a metal oxide containing nitrogen” will be described.

  For example, zinc oxide forms a hexagonal (wurtzite) crystal structure by combining the basic structure in which the zinc and oxygen atoms are tetrahedrally coordinated by the other four atoms. When nitrogen is contained in the structure, a structure in which some of the four atoms bonded to each other are replaced with nitrogen atoms, or a structure in which nitrogen enters the hexagonal crystal structure. It is guessed that.

  Nitriding can be promoted at the level of the above-described crystal structure by increasing the concentration of nitrogen or bringing it into an active state, but naturally the physical properties of zinc oxide change due to nitriding. For spectral absorption, promotion of nitriding is a preferable state, but other physical properties such as photoelectric characteristics and wear properties required for the photoconductor 50 do not always provide preferable characteristics. Therefore, for example, the characteristics suitable for the photoreceptor 50 can be obtained by controlling the nitrogen concentration as described above to control the nitriding state and creating a film in which an oxide and an oxide containing nitrogen are mixed. Is possible.

  Note that the above-described two types of metal oxide films may be alternately formed. For this purpose, a cylinder filled with a plurality of introduced gases may be connected to the film forming chamber, and the introduced gases may be switched appropriately. For example, if argon gas is always flowed as the introduction gas and nitrogen gas is allowed to flow at regular intervals and periods, an oxide containing nitrogen can be obtained only during the period in which nitrogen flows. In this method, a laminated structure of oxide and nitrogen containing oxide can be obtained continuously, and the interval and period of introducing nitrogen and the flow rate can be controlled easily. In addition, the film characteristics can be controlled, and characteristics suitable for the photoreceptor 50 can be obtained.

  Note that the method of obtaining the single-layer type photoreceptor 50 is not limited to the above-described mixing and film formation. Since the nitrogen content affects the physical properties of the metal oxide, such as the absorption wavelength, mobility, and specific resistance, nitrogen was included if optimization was made while taking into consideration the nitrogen content and the characteristics of the metal oxide. Even if a metal oxide and a metal oxide that is not so are not mixed, it is possible to obtain the performance as the photoreceptor 50 only with a metal oxide containing nitrogen.

  Further, as shown in Example 1, it has been confirmed that the same effect can be obtained even when carbon or a thin film mainly composed of carbon is used as a protective film.

(Example 3)
FIG. 6 is a schematic view of a film forming apparatus 60 using an aerosol deposition method according to Example 3 of the present invention.

  Hereinafter, a method for manufacturing the photoreceptor 50 using an aerosol deposition method suitable as a method for forming a metal oxide will be described with reference to FIG.

  A film forming apparatus 60 used in Example 3 includes an aerosol generator 7 for dispersing material particles 5 in an introduced gas to form an aerosol 6, and a film forming chamber 8 for ejecting the aerosol 6 from a nozzle and attaching it to a substrate. An exhaust pump 9 is connected to the film forming chamber 8.

  Gas cylinders 10a, 10b, and 10c for introducing introduction gas are connected to the aerosol generator 7 through introduction pipes 11, and by selecting the gas cylinders 10a, 10b, and 10c that supply introduction gas, the aerosol is generated. Different introduction gases are supplied to the generator 7, and the supply amount of each introduction gas is controlled independently, and the introduction gases supplied from the gas cylinders 10a, 10b, 10c are mixed and supplied to the aerosol generator 7. It is possible. Here, for example, the gas cylinder 10a is filled with argon gas, which is an inert gas, the gas cylinder 10b is filled with nitrogen, and the gas cylinder 10c is filled with oxygen.

  The leading end of the introduction tube 11 is located in the vicinity of the bottom surface inside the aerosol generator 7 and is disposed so as to be buried in the material particles 5. By sending the introduction gas from the gas cylinders 10 a, 10 b, 10 c, the material particles 5 The aerosol 6 is generated by being blown up. The generated aerosol 6 is supplied to the ejection nozzle 12 through the introduction pipe 11.

  The substrate 13 is mounted on the substrate holder 14. The substrate 13 becomes the support 1 of the photoconductor 50 described in the first embodiment.

  In the aerosol deposition method, an inert gas such as helium, argon, or krypton is usually used as the introduced gas. In the third embodiment, the above-described gas cylinders 10a, 10b, and 10c are selected or each gas is supplied. By adjusting the amount, nitrogen gas or oxygen gas is added to the inert gas as necessary.

  Nitrogen can be contained in the metal oxide film by adding nitrogen gas to the inert gas. That is, the manufacturing method shown in Example 3 forms the charge generation layer 2 by forming a metal oxide film in an atmosphere in which nitrogen is present.

  In addition, the reason for adding oxygen gas is that metal oxide is the object of film formation, so that oxygen deficiency during film formation, that is, reduction is difficult to occur, and characteristic deterioration due to insufficient oxygen in the film. Is to prevent.

  Hereinafter, the description will be continued using FIG. 1 and FIG.

  According to the configuration of FIG. 6, the gas supplied to the film forming chamber 8 includes inert gas and nitrogen gas, inert gas and oxygen gas, inert gas and nitrogen gas and oxygen gas, and nitrogen gas and oxygen gas. Combinations are conceivable, and the charge generation layer 2 having characteristics suitable for the photoreceptor 50 can be obtained by optimizing the composition ratio in these gases.

  Further, if an appropriate heat treatment is performed after forming the charge generation layer 2, the charge transport layer 3 (see FIG. 1), or the photosensitive layer 4 (see FIG. 5) of the photoreceptor 50 by the aerosol deposition method, more stable photosensitivity is obtained. A body 50 is obtained. Not only the aerosol deposition method but also the sputtering method and the plasma CVD method have an internal stress in the produced film, which causes the characteristics to deteriorate or become unstable. Heat treatment improves this, and it can be expected to improve characteristics by stress relaxation and to improve adhesion by appropriate diffusion.

  Various mechanisms can be mounted on the substrate holder 14 depending on the substrate shape and the substrate size. For example, when the charge generation layer 2, the charge transport layer 3 or the photosensitive layer 4 is formed on a cylindrical substrate 13 such as a drum-shaped photoreceptor 50, a mechanism for rotating the substrate holder 14 is provided. Good. Further, when the substrate 13 is flat and requires a large area as in the case of manufacturing the belt-like photosensitive member 50, a mechanism for moving the substrate holder 14 back and forth and right and left (X, Y axes) is provided. That's fine. Further, a rotation mechanism and an X and Y axis movement mechanism may be combined. Further, by arranging a large number of ejection nozzles 12, it is possible to cope with film formation of a large area, or these mechanisms may be used in combination.

  Now, the aerosol deposition method is a method of forming a desired film on the surface of the substrate 13 by spraying and colliding with the substrate 6 at a high speed the aerosol 6 in which ultrafine material is dispersed in a gas. It is disclosed in Japanese Patent Laid-Open No. 2001-181859. The film obtained by this method generates fine fragment particles by crushing ultrafine particles by collision, or causes ultrafine particles to collide and cause deformation by impact, thereby forming a new surface on a part thereof. Then, by bonding the fine fragment particles to the substrate 13 or bonding the fine fragment particles to each other, a high-density and excellent film with high density can be formed on the substrate 13 without firing. In particular, it is suitable as a method for forming a ceramic film such as an oxide. Moreover, the film formation rate is orders of magnitude faster than the conventional film formation methods such as sputtering and ion plating. We have found that if this aerosol deposition method is used to form the charge generation layer 2 used for the photoreceptor 50, the photoreceptor 50 having excellent performance can be obtained with high productivity.

  That is, there are two major problems in putting a metal oxide film such as zinc oxide into practical use using the charge generation layer 2 of the photoreceptor 50.

  One is that it has been difficult to obtain high sensitivity because the wavelength of the light source used for exposure is long in conventional semiconductor infrared lasers.

  The other is that a method for forming a film in a short time by a simple process while maintaining high performance could not be found.

  For the former problem, the short wavelength semiconductor laser is put to practical use, the wavelength is further shortened in the future, and further, as described in Example 1 and the like, the peak of spectral absorption in the blue region by containing nitrogen. In other words, the problem is being solved by shifting the sensitivity peak to the longer wavelength side.

  The latter problem can be solved by using the aerosol deposition method of the present invention to form a metal oxide to be the charge generation layer 2.

  That is, the aerosol deposition method described in detail in Example 3 is used for a metal oxide that can be sufficiently photosensitized with a short-wavelength semiconductor laser having a wavelength of about 405 [nm] that is currently mass-produced. For the metal oxide that can improve the latter problem and does not exhibit sufficient spectral absorption unless the wavelength is shorter than 405 [nm], the spectral absorption band can be lengthened by adding nitrogen to the charge generation layer 2. It is possible to obtain sufficient sensitivity even with a light source having a wavelength of about 405 [nm] by shifting to a wavelength. If the wavelength of the semiconductor laser is further shortened in the future and an ultraviolet laser or the like is put into practical use, the metal oxide to be the charge generation layer 2 is efficiently formed by using the aerosol deposition method shown in Example 3. I will do it.

  The aerosol deposition method is a film forming method that does not require a high vacuum, unlike the sputtering method and the plasma CVD method, and has a characteristic merit that it does not require complicated processes and increased capital investment. In the case of a laminated photoreceptor 50 in which both the charge generation layer 2 and the charge transport layer 3 are made of an inorganic material, in order to maximize the advantages of the aerosol deposition method, the charge generation layer 2 and the charge generation layer 2 can be made of the same base material. It is preferable to constitute the charge transport layer 3. That is, after the charge generation layer 2 is formed by mixing nitrogen that is effective in increasing the wavelength into the introduced gas, and then the film is formed by stopping the nitrogen gas, the film becomes the charge transport layer 3. The photoconductor 50 can be formed by a process, and a highly efficient production method can be obtained.

  In addition, as described in Example 2 by the aerosol deposition method, by controlling the nitrogen concentration in the introduced gas, for example, zinc oxide and zinc oxide containing nitrogen can be mixed and formed. Furthermore, by alternately switching the introduction gas, it is possible to alternately form zinc oxide and zinc oxide containing nitrogen. More specifically, the introduction gas used in the aerosol deposition method is a first introduction gas containing at least nitrogen (the introduction gas is supplied from both the gas cylinder 10a filled with inert gas and the gas cylinder 10b filled with nitrogen). The second introduction gas containing at least oxygen (supplied with the introduction gas from the gas cylinder 10c) may be alternately switched to stack metal oxides of the same base material (for example, zinc oxide or titanium oxide). The combination of gases to be introduced, the concentration of the gas, and the individual film thickness to be laminated differ depending on the characteristics of the material and the required characteristics, but may be optimized as necessary.

Example 4
FIG. 7 is a schematic configuration diagram of an electrophotographic apparatus 70 according to Embodiment 4 of the present invention.

  The electrophotographic apparatus 70 shown in FIG. 7 includes, as four cylindrical or columnar image forming bodies, for example, the photoconductors 15, 16, 17, and 18 described in detail in the first and second embodiments, and straddling these. And an intermediate transfer unit 20 having a belt-like transfer body 19 that extends. Around the photosensitive members 15, 16, 17, and 18, there are charging devices (here, charging rollers) 21, 22, 23, and 24, an exposure device 25, and developing units 26 and 27 each having a developer storage portion above. 28, 29, and photoreceptor cleaners 30, 31, 32, 33 are disposed. The intermediate transfer unit 20 is provided with a belt cleaner 35 for cleaning so-called residual toner that is not transferred onto the recording paper 34 but remains on the surface of the belt-shaped transfer body 19. Further, the belt-like transfer member 19 of the intermediate transfer unit 20 is a final member necessary for transferring the toner image formed and transferred by the respective photosensitive members 15, 16, 17, and 18 to the recording paper 34. The transfer roller 36 abuts or faces the transfer roller 36. The fixing device 37 is means for fixing the toner image transferred to the recording paper 34.

  Next, details of image formation will be described. First, the photosensitive member 15 according to the present invention is uniformly charged by the charging device 21, then exposed by the exposure device 25, and the electrostatic latent image formed thereby is developed by the developing device 26. The exposure apparatus 25 is equipped with a semiconductor laser having a wavelength of 400 to 415 [nm] (not shown).

  The toner image in which the electrostatic latent image is visualized is transferred to the belt-shaped transfer body 19 at a position facing or in contact with the belt-shaped transfer body 19 of the intermediate transfer unit 20. The toner image of the other color formed on the surface of the photoconductor 16 becomes the second toner image of the first toner image in accordance with the timing at which the first toner image advances to the position where it contacts the photoconductor 16. It is transferred on top of it. Similarly, the third and fourth toner images are transferred in a superimposed manner to complete a four-color superimposed image. The superimposed image formed on the belt-shaped transfer member 19 of the intermediate transfer unit 20 is then collectively transferred to the recording paper 34 at a portion in contact with the final transfer roller 36 and fixed to the recording paper 34 by the fixing device 37. A color image is formed on the recording paper 34.

  In the series of image forming processes, toner that has not been transferred from the photoconductors 15, 16, 17, and 18 to the belt-like transfer body 19 is scraped off by the photoconductor cleaners 30, 31, 32, and 33. The body cleaners 30, 31, 32, and 33 are configured by blades or the like, and the photoreceptor cleaners 30, 31, 32, and 33 are transferred by contacting (sliding) with the photoreceptors 15, 16, 17, and 18, respectively. Remove the toner that was not used.

  Since the photoconductors 15, 16, 17, and 18 described in detail in the first embodiment and the like have high wear resistance (durability), for example, when the process speed of the electrophotographic apparatus 70 is set to a higher speed, or so-called It can also be suitably used in equipment in a field that requires high throughput such as a heavy duty machine.

  FIG. 8 is a perspective view showing another example of an exposure apparatus applied to the electrophotographic apparatus 70 according to Embodiment 4 of the present invention.

  The exposure apparatus 80 shown in FIG. 8 is an organic electroluminescence element (organic EL element array 39) configured in an array as an exposure light source. The organic EL element array 39 has a light emission wavelength from red to blue, and an organic material can be selected according to the characteristics of the photoconductors 15, 16, 17, and 18.

  The organic EL element array 39 is held in a long housing 40. The positioning pins 41 provided at both ends of the long housing 40 are inserted into the opposing positioning holes of the long housing 40 and fixed through the screw insertion holes 42 provided at both ends of the long housing 40, whereby The organic EL element array 39 corresponding to the bodies 15, 16, 17, and 18 can be fixed at a predetermined position as exposure means.

  Each organic EL element constituting the organic EL element array 39 is driven by a TFT (Thin Film Transistor) 44 formed on the same glass substrate 43. The gradient index rod lens array 45 is an imaging optical system provided in front of the organic EL element array 39, and is configured by stacking gradient index rod lenses 46.

  The housing 40 covers the periphery of the glass substrate 43, and the side facing the photoreceptor not shown is opened. In this manner, light is emitted from the gradient index rod lens 46 to the photosensitive member to perform exposure. A light-absorbing member (paint) is provided on the surface of the housing 40 that faces the end surface of the glass substrate 43.

  In the fourth embodiment, the exposure device 25 using a laser light source as an exposure light source or the exposure device 80 using an organic EL element array is exemplified. However, a so-called LED head using an LED as an exposure light source may be used as the exposure device. Good.

  As a result of mounting and operating the photoconductor according to the present invention in the electrophotographic apparatus 70 configured as described above, the image quality of the obtained image is an organic photoconductor or amorphous silicon using a conventional red semiconductor laser as an exposure light source. It was confirmed that a higher resolution was obtained than that produced using a photoconductor, and that the outermost surface was an inorganic material, so that it had higher durability than an organic photoconductor.

  According to the present invention, an electrophotographic photosensitive member having high durability can be obtained. Therefore, the present invention can be suitably applied to a multi-function machine such as a copying machine, a printer, a facsimile machine, and an MFP (Multi Function Printer) using the electrophotographic photosensitive member.

Schematic diagram showing the layer structure of a multilayer electrophotographic photoreceptor according to Example 1 of the present invention. The characteristic view which shows the result of having measured the spectral absorption characteristic of the zinc oxide in Example 1 of this invention The characteristic view which shows the result of having measured the energy state of the electron by X-ray photoelectron spectroscopy in Example 1 of this invention Characteristic diagram showing the results of observing crystal structures by X-ray diffraction of a zinc oxide film containing nitrogen and a zinc oxide film not containing nitrogen Schematic diagram showing the layer structure of a single-layer electrophotographic photoreceptor according to Example 2 of the present invention Schematic of the film-forming apparatus using the aerosol deposition method based on Example 3 of this invention Schematic configuration diagram of an electrophotographic apparatus according to Embodiment 4 of the present invention. FIG. 7 is a perspective view showing another example of an exposure apparatus applied to an electrophotographic apparatus according to Embodiment 4 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 2 Charge generation layer 3 Charge transport layer 4 Photosensitive layer 5 Material particle 6 Aerosol 7 Aerosol generator 8 Deposition chamber 9 Exhaust pump 10a, 10b, 10c Gas cylinder 11 Introducing pipe 12 Ejection nozzle 13 Substrate 14 Substrate holder 15, 16 , 17, 18 Photoconductor 19 Belt-shaped transfer body 20 Intermediate transfer unit 21, 22, 23, 24 Charging device (charging roller)
25 Exposure device 26, 27, 28, 29 Developer 30, 31, 32, 33 Photoconductor cleaner 34 Recording paper 35 Belt cleaner 36 Final transfer roller 37 Fixing device 39 Organic EL element array 40 Housing 41 Positioning pin 42 Screw insertion hole 43 Glass substrate 44 TFT
45 Rod lens array 46 Refractive index distribution type rod lens 50 Photoconductor (electrophotographic photoconductor)
60 Film forming apparatus 70 Electrophotographic apparatus 80 Exposure apparatus

Claims (12)

A support having at least a surface layer having conductivity;
An electrophotographic photosensitive member provided with a charge generation layer composed of a metal oxide containing nitrogen on the support. The electrophotographic photosensitive member according to claim 1,
An electrophotographic photoreceptor in which the charge generation layer is mainly composed of zinc oxide or titanium oxide. The electrophotographic photosensitive member according to claim 1,
An electrophotographic photosensitive member, wherein the charge generation layer is sensitive to light having a blue wavelength. The electrophotographic photosensitive member according to claim 1,
An electrophotographic photosensitive member in which a protective film mainly composed of carbon is formed on the outermost surface. On a support having at least a surface layer having conductivity,
A method for producing an electrophotographic photosensitive member, wherein a charge generation layer is formed by forming a metal oxide film in an atmosphere containing nitrogen. On a support having at least a surface layer having conductivity,
A method for producing an electrophotographic photosensitive member, wherein a charge generation layer is formed by forming a metal oxide containing nitrogen by an aerosol deposition method. It is a manufacturing method of the electrophotographic photosensitive member of Claim 6, Comprising:
A method for producing an electrophotographic photoreceptor in which oxygen is contained in an introduced gas used in the aerosol deposition method. It is a manufacturing method of the electrophotographic photosensitive member of Claim 6, Comprising:
A method for producing a photoreceptor for electrophotography, wherein nitrogen is contained in an introduced gas used in the aerosol deposition method. It is a manufacturing method of the electrophotographic photosensitive member of Claim 6, Comprising:
A method for producing a photoreceptor for electrophotography, wherein oxygen and nitrogen are contained in an introduced gas used in the aerosol deposition method. It is a manufacturing method of the electrophotographic photosensitive member of Claim 6, Comprising:
The introduction gas used in the aerosol deposition method is an electron in which a first introduction gas containing at least nitrogen and a second introduction gas containing at least oxygen are alternately switched, and metal oxides of the same base material are stacked. A method for producing a photographic photoreceptor. It is a manufacturing method of the electrophotographic photosensitive member of Claim 6, Comprising:
A method for producing an electrophotographic photosensitive member, wherein a layer constituting the photosensitive member is formed and then further heat-treated. An electrophotographic apparatus equipped with the electrophotographic photosensitive member according to claim 1.

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