JP2009258641A - Charging member, and process cartridge and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging member which has excellent surface mechanical durability and oxidation resistance, and with which image defects due to deposition of toner components are suppressed, also, has excellent charging characteristics, further, which can easily keep these characteristics at a high level with time, and to provide a process cartridge and an image forming apparatus using the charging member. <P>SOLUTION: The charging member includes a surface layer, and at least the most outer surface portion of the surface layer contains oxygen and at least one metallic element selected out of a group composed of Ga and In and the oxygen content contained in at least the most outer surface portion of the surface layer is ≥15 atom%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging member, a process cartridge and an image forming apparatus using the charging member.

  In recent years, electrophotographic methods have been widely used for copying machines, printers, and the like. A charging member used in an image forming apparatus using such an electrophotographic method is exposed to various contacts and stress in the apparatus. High reliability is required with digitization and colorization of forming apparatuses.

Under such circumstances, the surface should be coated with a non-adhesive film such as a fluorine-containing resin in order to prevent contamination of the toner and toner external additives, improve the uniformity of charging, and suppress uneven density. Has been proposed (see, for example, Patent Document 1). In addition, a proposal has been made to coat the surface of an elastic body with diamond-like carbon (see, for example, Patent Documents 2 and 3). Furthermore, the surface layer is formed by sputtering, plasma chemical vapor deposition (CVD), ion plating, or the like using TiN, TiAlN, TiC, CrN, SiC, Si ₃ N ₄ , Al ₂ O ₃ , Inorganic substances such as DLC (diamond-like carbon) are exemplified (for example, see Patent Document 2).
On the other hand, a charging roller whose surface layer has a Vickers hardness of 1500 Hv or more has been proposed as a charging device that improves releasability and contamination prevention (see, for example, Patent Document 4).

JP 58-194061 A Japanese Patent Laid-Open No. 1998-18037 JP 2006-258934 A JP 2006-235045 A

  However, since such a charging member is discharged on the surface, the surface gradually deteriorates, and the anti-contamination property and the stability of the resistance value are not sufficient.

This invention is made | formed in view of the said problem, and makes it a subject to achieve the following objectives.
That is, the problems of the present invention are excellent in mechanical durability and oxidation resistance on the surface, can suppress image defects due to adhesion of toner components, are excellent in charging characteristics, and further, these characteristics are improved over time. It is an object to provide a charging member that can be easily maintained at a level, and a process cartridge and an image forming apparatus using the charging member.

  As a result of intensive studies, the present inventor has found that the following invention can solve the problem, and has achieved the above object.

<1>
The surface layer includes at least one selected from the group consisting of oxygen and Ga and In as a metal element at least on the outermost surface portion of the surface layer, and included in at least the outermost surface portion of the surface layer. A charging member having an oxygen content of 15 atomic% or more.

<2>
The charging member according to <1>, wherein the metal element is Ga.

<3>
The charging member according to <1> or <2>, wherein at least an outermost surface portion of the surface layer contains hydrogen.

<4>
Of the elements constituting at least the outermost surface portion of the surface layer, the sum of the constituent ratios with respect to the total element amount of the metal element and oxygen, or the metal element, oxygen and hydrogen is 0.95 or more, and The charging member according to any one of <1> to <3>, wherein a composition ratio (oxygen / metal element) of the oxygen and the metal element is 1.1 or more and 1.5 or less.

<5>
The charging member according to any one of <1> to <4>, wherein a concentration distribution of oxygen contained in the surface layer in a thickness direction of the surface layer decreases toward a lower layer side.

<6>
The charging according to any one of <1> to <5>, wherein a tetrahedral amorphous carbon layer and an elastic layer are sequentially provided on a lower layer side of the surface layer from the surface layer side. Element.

<7>
<1> to <6> The process member characterized by comprising the charging member as described in any one of <6>.

<8>
An image forming apparatus comprising the charging member according to any one of <1> to <6>.

  According to the present invention, the surface has excellent mechanical durability and oxidation resistance, can suppress image defects due to adhesion of toner components, and has excellent charging characteristics. A charging member that can be easily maintained, and a process cartridge and an image forming apparatus using the charging member can be provided.

  Embodiments of the charging member, the process cartridge, and the image forming apparatus of the present invention will be described with reference to FIGS. 1 to 9, but are not limited to the following descriptions.

(Charging member)
The charging member of the present invention has a surface layer, and at least the outermost surface portion of the surface layer includes oxygen and at least one selected from the group consisting of Ga and In as a metal element. The content of the oxygen contained in the outermost surface portion is 15 atomic% or more.
The charging member of the present invention may be a contact-type charging method in which a voltage is applied to the charging member brought into contact with the surface of the photoreceptor to charge the surface of the photoreceptor, and the surface of the photoreceptor and the charging member are brought close to each other. Alternatively, a non-contact charging method in which a voltage is applied to the charging member to charge the photosensitive member may be used.
Further, the voltage applied to the charging member may be only direct current, or alternating current may be superimposed on direct current. When the AC voltage is superimposed, the peak-to-peak voltage is preferably 400 or higher and 1800 V or lower, preferably 800 or higher and 1600 V or lower, and more preferably 1200 or higher and 1600 V or lower. The frequency of the AC voltage is 50 or more and 20,000 Hz or less, preferably 100 or more and 5,000 Hz or less.

The layer structure of the charging member of the present invention is only required to have a surface layer on the substrate, and the substrate may or may not have conductivity. In order to prevent current from flowing into the defective portion of the photoreceptor, a conductive layer or a resistance layer may be provided between the conductive layer and the surface layer. There may also be a conductive substrate or a conductive or semiconductive elastic layer between the conductive layer and the surface layer. Moreover, in order to improve the adhesiveness between the surface layer and the base, there may be a conductive or semiconductive adhesive layer. Note that “conductive” means that the volume resistivity is less than 10 ³ Ωcm, and “semiconductive” means that the volume resistivity is 10 ³ Ωcm or more and 10 ¹⁰ Ωcm or less. Hereinafter, the layer in contact with the surface layer is referred to as a base.
FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of the charging member of the present invention. In FIG. 1, 1 is a conductive substrate, 2 is an elastic layer, or resin layer, and 3 is a surface layer.
FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the charging member of the present invention. In FIG. 2, 4 represents a resistance layer, and the others are the same as those shown in FIG.
FIG. 3 is a schematic cross-sectional view showing another example of the layer structure of the charging member of the present invention. In FIG. 3, 5 represents a substrate, 6 represents a conductive layer, and the others are the same as those shown in FIG. It is the same.
FIG. 4 is a schematic cross-sectional view showing another example of the layer structure of the charging member of the present invention. In FIG. 4, 7 represents a tetrahedral amorphous carbon layer, and the others are the same as those shown in FIG. It is the same.
The shape of the charging member may be any of a film shape, a plate shape, a roller shape, and the like, but a roller-shaped member is particularly preferable.
The roller member is composed of a core material as a conductive substrate, an elastic layer around the core material, and a surface layer. Moreover, when using it non-contacting, a resin layer may be sufficient instead of an elastic layer, and there may be no elastic layer. Further, a resistance layer and / or a tetrahedral amorphous carbon layer may be provided inside the surface layer.
The core material is conductive and generally used is iron, copper, brass, stainless steel, aluminum, nickel, or the like. In addition, a resin molded product in which conductive particles are dispersed can be used.

[Elastic layer]
The elastic layer in the present invention has the aforementioned conductivity or semiconductivity. In general, the rubber material contains conductive particles or semiconductive particles dispersed therein or contains an ionic conductive material. However, it is not always necessary when the rubber material has conductivity. Moreover, a foam may be sufficient. Rubber materials include ethylene-propylene-diene copolymer rubber (EPDM), polybutadiene, natural rubber, polyisobutylene, styrene-butadiene copolymer (SBR), chloroprene rubber (CR), acrylonitrile-butadiene copolymer rubber (NBR), Silicon rubber, urethane rubber, epichlorohydrin rubber, styrene-butadiene-styrene block copolymer (SBS), thermoplastic elastomer, norbornene rubber, fluorosilicone rubber, ethylene oxide rubber or the like, or a copolymer or a mixture thereof is used. Examples of the conductive particles or semiconductive particles include carbon black, zinc, aluminum, copper, iron, nickel, chromium, titanium and other metals, ZnO—Al ₂ O ₃ , SnO ₂ —Sb ₂ O ₃ , In ₂ O ₃ — Metal oxides such as SnO ₂ , ZnO—TiO ₂ , MgO—Al ₂ O ₃ , FeO—TiO ₂ , TiO ₂ , SnO ₂ , Sb ₂ O ₃ , In ₂ O ₃ , ZnO, and MgO can be used. Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; perchlorates and chlorates of alkaline earth metals Can be mentioned. These conductive agents may be used alone or in combination of two or more.

[Resistance layer]
The material of the resistance layer is one in which conductive particles or semiconductive particles are dispersed in a binder resin and the resistance is controlled. The resistivity is 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less, preferably 10 ⁵ Ωcm or more and 10 ^{It is 12} Ωcm or less, more preferably 10 ⁷ Ωcm or more and 10 ¹² Ωcm or less. The film thickness is 0.01 μm or more and 1000 μm or less, preferably 0.1 μm or more and 500 μm or less, more preferably 0.5 μm or more and 100 μm or less. Binder resins include acrylic resin, cellulose resin, polyamide resin, methoxymethylated nylon, ethoxymethylated nylon, polyurethane resin, polycarbonate resin, polyester resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin, oloethylene perfluoro Polyolefin resins such as alkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyethylene terephthalate (PET), styrene butadiene resin, and the like are used. As the conductive particles or semiconductive particles, the same carbon black, metal, and metal oxide as the elastic layer are used. If necessary, an antioxidant such as hindered phenol and hindered amine, a filler such as clay and kaolin, and a lubricant such as silicone oil can be added. As a means for forming these layers, a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like can be used.

[Tetrahedral amorphous carbon layer]
A tetrahedral amorphous carbon layer (hereinafter, referred to as “ta-C layer” as appropriate) is a carbonaceous material having a high hardness and a high Young's modulus. Excellent suppression of scratches and wear. ta-C is a substance having a volume resistivity suitable for a charging member, which is 10 ⁶ Ω · cm or more and 10 ⁹ Ω · cm or less, while having the same hardness as diamond.
Conventionally, when the charging member is used in a high temperature and high humidity environment for a long period of time, bleeds such as low molecular weight components, softeners, and plasticizers contained in the elastic layer ooze out from the elastic layer. This bleed material chemically alters the photoreceptor to cause cracks in the surface layer, and adheres to the photoreceptor to alter its electrical characteristics. That is, the image is lost and black streaks are generated, and the quality of the image is significantly reduced. In the present invention, even if a crack occurs in the surface layer described later, a charging member is used for a long period of time by providing a ta-C layer between the elastic layer described above and the surface layer described later. Even if a crack or the like occurs, bleeding can be effectively suppressed.

In the present invention, the ta-C layer refers to a layer containing sp3 bonds of 40% or more. Such a ta-C layer has sufficient hardness. Thus, since it has sp3 bonds at a sufficient ratio, a dense tissue structure is established, or excellent adhesion to the above-mentioned elastic layer and the surface layer described later. In addition, when the ta-C layer contains fluorine atoms, it exhibits sufficient water repellency by the action of fluorine atoms scattered near the surface, protects the elastic layer even when moisture enters from the surface layer, and enhances corrosion resistance. It is done. As a result, it is possible to achieve an effect that changes with time in shape and electrical characteristics are small.
Here, as a method for identifying sp3 bond, for example, by using Raman laser (Nicolet Almega XR manufactured by Thermo Fisher), a laser having a wavelength of 633 nm, a peak area A at sp3, 1370 cm ⁻¹ and sp2, 1590 cm ⁻ the area ratio of the peak area a in Sp3,1370cm ^-1 to the total and the area B of a peak in the ¹ and rated determined from (= a / (a + B ) × 100 (%)).

  The thickness of the ta-C layer is preferably 0.2 μm or more and 2.0 μm or less, more preferably 0.5 μm or more and 1.5 μm or less, and 0.7 μm or more and 1.2 μm or less. Is particularly preferred. When the thickness is 0.2 μm or more, a high protection effect from the material forming the elastic layer is maintained, and when the thickness is 2.0 μm or less, there is a tendency that a high bleed suppression effect can be obtained without hindering charging performance. .

Formation of the ta-C layer in the present invention can be performed by a filter-cathode-vacuum-arc (FCVA) method in which carbon plasma is generated by graphite vacuum arc discharge, and ionized carbon is extracted and deposited therefrom. It is preferable to use an FCVA apparatus manufactured by Shimadzu Corporation.
As formation conditions, a film formation temperature of 0 ° C. or higher and 80 ° C. or lower (more preferably 20 ° C. or higher and 80 ° C. or lower, particularly preferably 40 ° C. or higher and 80 ° C. or lower) and a film formation rate of 1.5 nm / s are preferable.

[Surface layer]
The surface layer of the present invention contains oxygen and at least one selected from the group consisting of Ga and In as a metal element, and the content of oxygen contained in at least the outermost surface portion of the surface layer is 15 atomic% or more. It is.
In such a composition, the entire surface layer may have this composition, and at least the outermost surface of the surface layer may have this composition. Here, “at least the outermost surface of the surface layer” means an extremely thin layer having a depth from the surface of at least several nm (specifically, a range of about 1 nm to 50 nm from the surface), The layer substantially corresponds to the measurement range in the depth direction when the solid surface is measured by Rutherford backscattering (RBS). Note that the layer containing oxygen and Ga and / or In as main constituent elements preferably has a thickness of 0.5 nm or more in the depth direction from the surface of the surface layer, and has a thickness of 10 nm or more. More preferably. The composition of the surface layer preferably contains Ga and oxygen from the viewpoint of chemical stability against an oxidizing atmosphere such as ozone or nitrogen oxides generated by discharge due to charging.
Thus, since at least the outermost surface of the surface layer includes an oxide of Ga and / or In, the surface layer is exposed to an oxidizing atmosphere such as ozone or nitrogen oxide generated by discharge due to charging in the image forming apparatus. Since it is difficult to oxidize itself, deterioration due to oxidation can be prevented. In addition, since the adhesion of the discharge product on the surface layer and the adhesion of the toner or the external additive of the toner can be suppressed, the occurrence of image defects can also be suppressed. Moreover, since it is excellent in mechanical durability, it is easy to maintain these characteristics at a high level over a long period of time.

When Ga and / or In atoms are used for the surface layer, the content in the surface layer is preferably in the range of 0.1 atomic% to 50 atomic%, and preferably in the range of 5 atomic% to 40 atomic%. More preferably, it is within. When the content of Ga and / or In atoms is 0.1 atomic% or more, the formation of the surface layer itself is good, and when it is 50 atomic% or less, it is easy to adjust to an appropriate electrical resistance. Excellent current leakage.
The oxygen content is 15 atomic% or more, preferably 20 atomic% or more and 60 atomic% or less, and more preferably 25 atomic% or more and 50 atomic% or less. When the oxygen content is 15 atomic% or more, the moisture resistance and oxidation resistance of the surface are sufficiently exhibited.
Of the above-described elements, the Ga and / or In and oxygen contents are preferably satisfied at least on the outermost surface of the surface layer, and oxygen at least on the outermost surface of the surface layer. The content needs to be 15 atomic% or more. When the oxygen content is less than 15 atomic%, the moisture resistance and oxidation resistance and oxidation resistance of the surface are insufficient.

In the surface layer containing the metal element, oxygen, and hydrogen, the sum of the elemental composition ratios of the metal element, oxygen, and hydrogen is set to 0.95 or more, and the elemental composition ratio of oxygen and the metal element (oxygen) / Metal element) is preferably 1.1 or more and 1.5 or less in order to improve controllability of electric resistance.
When the sum of the constituent ratios of the elements is 0.95 or more, for example, when a group 15 element such as N, P, As or the like is mixed, the influence of bonding with gallium can be ignored. An appropriate range of the metal element composition ratio (oxygen / metal element) can be found.
The sum of the constituent ratios of the metal element, oxygen and hydrogen is preferably 0.99 or more.
When the elemental composition ratio (oxygen / metal element) of the oxygen and the metal element is 1.1 or more, the electric resistance value of the film is sufficiently high, and even if there is a defect in the photoconductor, the current leakage can be prevented. Good resistance. A material of 1.5 or less can be obtained in a stable state as a material containing the metal element, oxygen and hydrogen as constituent elements. The elemental composition ratio (oxygen /) of oxygen and the metal element is preferably 1.1 or more and 1.4 or less, and more preferably 1.1 or more and 1.3 or less. When the elemental composition ratio is 1.4 or less, the conductivity of the film is sufficient, and there is no problem with the residual potential when the film thickness is increased.

  Both Ga and In may be contained in the surface layer.

The content of the element such as the metal element and oxygen in the surface layer is determined by Rutherford backscattering (hereinafter referred to as “RBS”) including the distribution in the film thickness direction as follows.
RBS used NEC 3SDH Pelletron as an accelerator, CE & A RBS-400 as an end station, and 3S-R10 as a system. The analysis used the CE & A HYPRA program.
The RBS measurement conditions are: He ++ ion beam energy is 2.275 eV, detection angle is 160 °, and Grazing Angle is 109 ° ± 2 ° with respect to the incident beam.

Specifically, the RBS measurement was performed as follows.
First, a He ++ ion beam is incident on the sample perpendicularly, a detector is set at 160 ° with respect to the ion beam, and the backscattered He signal is measured. The composition ratio and the film thickness are determined from the detected energy and intensity of He. In order to improve the accuracy of obtaining the composition ratio and the film thickness, the spectrum may be measured at two detection angles. The accuracy is improved by measuring and cross-checking at two detection angles with different depth resolution and backscattering dynamics.
The number of He atoms back-scattered by the target atom is determined only by three factors: 1) the atomic number of the target atom, 2) the energy of the He atom before scattering, and 3) the scattering angle. The density is assumed by calculation from the measured composition, and this is used to calculate the film thickness. The density error is within 20%.

Further, the amount of hydrogen contained in the surface layer is obtained as follows by hydrogen forward scattering (hereinafter sometimes referred to as “HFS”).
HFS used NEC 3SDH Pelletron as an accelerator, CE & A RBS-400 as an end station, and 3S-R10 as a system. For the analysis, the CE & A HYPRA program was used. The measurement conditions of HFS are as follows.
-He ++ ion beam energy: 2.275 eV
Detection angle: Grazing Angle 30 ° with respect to 160 ° incident beam

The HFS measurement can pick up the hydrogen signal scattered in front of the sample by setting the detector at 30 ° to the He ++ ion beam and the sample at 75 ° from the normal. At this time, the detector is preferably covered with a thin aluminum foil to remove He atoms scattered together with hydrogen. The quantification is performed by comparing the hydrogen counts of the reference sample and the sample to be measured after normalization with the stopping power.
As a reference sample, a sample obtained by ion implantation of H into Si and muscovite were used. It is known that muscovite has a hydrogen concentration of 6.5 atomic% ± 1 atomic%. Note that H adsorbed on the outermost surface can be obtained by subtracting the amount of H adsorbed on the clean Si surface.

The surface layer may be microcrystalline, polycrystalline, or amorphous, but is preferably amorphous from the viewpoint of improving surface smoothness. The crystallinity / amorphous property can be determined by the presence or absence of a point or a line in a diffraction image obtained by RHEED (reflection high energy electron diffraction) measurement.
Although the details will be described later, the surface layer is laminated on the conductive substrate by using a vapor phase film forming method, so that the cross section may have a columnar structure depending on the film forming conditions and the like.

  Various dopants can be added to the surface layer in order to control the conductivity type. When the conductivity is controlled to be n-type, for example, one or more elements selected from Si, Ge, and Sn can be used. When the conductivity is controlled to be p-type, for example, Be, Mg, Ca, One or more elements selected from Zn and Sr can be used.

  The surface layer tends to contain many bonding defects, dislocation defects, crystal grain boundary defects, etc. in its internal structure in any case of microcrystal, polycrystal or amorphous. For this reason, hydrogen and / or a halogen element may be contained in the surface layer in order to inactivate these defects. Hydrogen and halogen elements in the surface layer are taken into bond defects in the crystal, defects at the grain boundaries, etc., and have a function of eliminating the reactive sites and performing electrical compensation.

  When hydrogen is used, the amount of hydrogen contained in the surface layer ranges from 0.1 atomic% to 60 atomic% with respect to the entire two main elements (the metal element and oxygen) constituting the surface layer. Preferably, it is in the range of 1 atomic% or more and 50 atomic% or less. This hydrogen amount can be measured in absolute value by HFS (Hydrogen Forward Scattering), and can also be estimated from an infrared absorption spectrum.

In the charging member of the present invention, the entire surface layer may be a metal element composed only of oxygen and Ga and / or In, but the surface layer requires other elements such as nitrogen and hydrogen. It may be included accordingly. By using such a third element, the composition, structure, and various physical properties of the surface layer can be controlled more easily and flexibly, so that the above-described effects can be easily achieved at a higher level.
In particular, as the third element, the surface layer preferably contains nitrogen. In this case, high hardness and transparency can be obtained by the bond between the metal element and nitrogen, and sufficient mechanical durability can be obtained. Furthermore, as will be described later, it is also preferable that the surface layer contains hydrogen from the viewpoint that structural defects in the surface layer can be suppressed.

Further, the composition in the thickness direction of the surface layer may have an inclined structure or may be composed of two or more multilayer structures.
Further, the oxygen concentration distribution in the surface layer thickness direction may be uniform or non-uniform, but preferably decreases toward the lower layer side of the charging member.
By having such an oxygen concentration distribution, it is possible to achieve a higher level of mechanical durability, oxidation resistance, and contamination resistance and to easily maintain these characteristics over a longer period of time. In particular, such an effect is further exhibited when the element other than oxygen is nitrogen. In addition, the distribution profile of the oxygen concentration in the surface layer thickness direction is not particularly limited, and may be, for example, linear, curved, or stepped.

  In addition, when nitrogen is contained in the surface layer, the content thereof is preferably 60 atomic% or less, and more preferably 50 atomic% or less with respect to the surface layer. When the nitrogen content exceeds 60 atomic%, the water resistance of the surface layer becomes insufficient, so that it may lack practicality. Further, the nitrogen concentration distribution in the surface layer thickness direction may be uniform or non-uniform, but is preferably not substantially contained in the outermost surface.

-Surface layer and formation method thereof-
Next, a method for forming the surface layer will be described. In the formation of the surface layer, there is no particular limitation as long as at least the outermost surface can be formed so as to contain oxygen and Ga and / or In, and the entire surface layer is directly formed on the base with oxygen and Ga and / or In. It can be formed so as to contain In. In the case where the surface layer is formed by stacking two or more layers having different compositions on the base, at least a layer containing oxygen and Ga and / or In is formed when the uppermost layer is formed. For example, a layer containing Ga and / or In and nitrogen and a layer containing Ga and / or In and oxygen can be stacked over the base in this order.

Alternatively, a surface layer can be formed by once forming a film containing Ga and / or In and an element other than oxygen as a main component on a base and then oxidizing the film from the surface. . In this case, in particular, a film containing Ga and / or In and nitrogen as main components is formed on the base, and this film is oxidized, so that at least the outermost surface layer has oxygen and Ga and / or In. A surface layer containing can be formed.
As an oxidation treatment method in this case, any method of natural oxidation by leaving it in the atmosphere or forced oxidation using ozone or the like may be used, but it is used by being incorporated in an image forming apparatus as a charging member. It is necessary to carry out sufficient oxidation treatment beforehand. The oxidation treatment is particularly preferably performed under intentional and controlled conditions in order to suppress variation in the surface layer characteristics within the surface of the charging member and variation in quality between the charging members.

For example, when natural oxidation is used, the oxidation process is more likely to proceed in a high humidity environment. Therefore, the leaving environment when natural oxidation is performed is preferably 40% or higher, and 50% or higher. Is more preferable, and it is still more preferable that it is 70% or more.
In addition, when the time of natural oxidation is short, if the layer near the outermost surface is not sufficiently oxidized and is used as a photoreceptor, the original performance cannot be exhibited, and the surface layer is significantly worn away. And may not be practical. From such a viewpoint, the time for performing the natural oxidation treatment is preferably 3 hours or more, preferably 10 hours or more, and more preferably 24 hours or more.

  In addition to natural oxidation, for example, forced oxidation using ozone or plasma in an oxygen atmosphere can be used as the oxidation treatment method. Such oxidation treatment can be performed in a shorter time than natural oxidation, and by selecting the oxidation conditions, a position deeper than natural oxidation (more on the photosensitive layer side) in the depth direction of the film thickness. It is easy to perform forced oxidation up to the position). Further, since the oxidation treatment can be completed in a short time, it is also useful when a film containing Ga and / or In and nitrogen as main components is likely to be deteriorated by reacting with moisture in the atmosphere.

Next, the method for forming the surface layer will be described more specifically. In forming the surface layer, a known vapor deposition method such as a plasma CVD method, a metal organic chemical vapor deposition method, or a molecular beam epitaxy method can be used. Hereinafter, a specific example will be described with reference to a drawing of an apparatus used for forming the surface layer.
FIG. 5 is a schematic diagram showing an example of a film forming apparatus used for forming the surface layer of the photoreceptor of the present invention, and FIG. 5A is a schematic cross-sectional view when the film forming apparatus is viewed from the side. FIG. 5B is a schematic cross-sectional view taken along line A1-A2 of the film formation apparatus illustrated in FIG. In FIG. 5, 10 is a film forming chamber, 11 is an exhaust port, 12 is a substrate rotating unit, 13 is a substrate holder, 14 is a substrate, 15 is a gas introduction unit, 16 is a shower nozzle, 17 is a plasma diffusion unit, and 18 is a high frequency. A power supply unit, 19 is a plate electrode, 20 is a gas introduction tube, and 21 is a high-frequency discharge tube unit.

In the film forming apparatus shown in FIG. 5, an exhaust port 11 connected to a vacuum exhaust device (not shown) is provided at one end of the film forming chamber 10, and the side on which the exhaust port 11 of the film forming chamber 10 is provided. On the opposite side, a plasma generator comprising a high-frequency power supply unit 18, a plate electrode 19 and a high-frequency discharge tube unit 21 is provided.
This plasma generator is disposed in a high-frequency discharge tube portion 21, a high-frequency discharge tube portion 21, a flat plate electrode 19 provided with a discharge surface on the exhaust port 11 side, and disposed outside the high-frequency discharge tube portion 21. The high-frequency power supply unit 18 is connected to the surface of the electrode 19 opposite to the discharge surface. The high-frequency discharge tube portion 21 is connected to a gas introduction tube 20 for supplying gas into the high-frequency discharge tube portion 21, and the other end of the gas introduction tube 20 is a first not shown. Connected to the gas supply.

  Note that the plasma generator shown in FIG. 6 may be used instead of the plasma generator provided in the deposition apparatus shown in FIG. FIG. 6 is a schematic diagram showing another example of a plasma generator that can be used in the film forming apparatus shown in FIG. 5, and is a side view of the plasma generator. In FIG. 6, 22 represents a high frequency coil, 23 represents a quartz tube, and 20 is the same as that shown in FIG. This plasma generator comprises a quartz tube 23 and a high-frequency coil 22 provided along the outer peripheral surface of the quartz tube 23. One end of the quartz tube 23 is formed with a film forming chamber 10 (not shown in FIG. 6). It is connected. The other end of the quartz tube 23 is connected to a gas introduction tube 20 for introducing gas into the quartz tube 23.

A rod-shaped shower nozzle 16 that is substantially parallel to the discharge surface is connected to the discharge surface side of the flat plate electrode 19, and one end of the shower nozzle 16 is connected to the gas introduction portion 15. A second gas supply source (not shown) provided outside the film forming chamber 10 is connected.
In addition, a substrate rotating unit 12 is provided in the film forming chamber 10, and the substrate holder 13 is arranged so that the cylindrical substrate 14 faces the longitudinal direction of the shower nozzle and the axial direction of the substrate 14 substantially in parallel. It is adapted to be attached to the base rotating part 12 via During film formation, the substrate 14 can be rotated in the circumferential direction by rotating the substrate rotating unit 12. In addition, as the base 14, a member formed up to the base in advance is used.

The formation of the surface layer can be performed, for example, as follows. First, N ₂ is introduced from the gas introduction tube 20 into the high-frequency discharge tube 21, and a 13.56 MHz radio wave is supplied from the high-frequency power supply unit 18 to the plate electrode 19. At this time, the plasma diffusion portion 17 is formed so as to spread radially from the discharge surface side of the flat plate electrode 19 to the exhaust port 11 side.
Next, trimethylgallium gas diluted with hydrogen using hydrogen as a carrier gas is introduced into the film forming chamber 10 through the gas introduction part 15 and the shower nozzle 16, thereby hydrogen, nitrogen and gallium are introduced into the surface of the substrate 14. A containing film can be formed.

Here, in order to introduce oxygen into the film, a method of incorporating oxygen atoms during film formation or a method of oxidizing with oxygen after film formation can be used.
In the former case, a surface layer containing oxygen, nitrogen, and a group 13 element can be formed by mixing nitrogen gas with oxygen-containing gas such as oxygen gas or N ₂ O or H ₂ O. . In addition, oxygen gas or a gas containing oxygen such as N ₂ O or H ₂ O is mixed with a rare gas such as He or Ar to generate plasma, which is reacted with an organometallic gas such as trimethylgallium gas. It is also possible to form a film containing
In the latter case, it can be performed in a vacuum or in the atmosphere. In the case of performing in vacuum, for example, oxygen can be taken into the film by performing high frequency discharge using oxygen gas diluted with a rare gas or the like. Furthermore, as another method for incorporating oxygen into the film, a known method such as a thermal diffusion method or an ion implantation method can be employed. Alternatively, the substrate 14 on the surface of which a film containing hydrogen and containing nitrogen and gallium is formed can be oxidized by simply exposing it to air in the atmosphere or exposing it to an oxygen atmosphere at atmospheric pressure.

The formation temperature of the surface layer during film formation is not particularly limited, but it is preferably formed at 20 ° C. to 200 ° C. The substrate temperature at the time of forming the surface layer is preferably 150 ° C. or less, and more preferably 100 ° C. or less. Even if the substrate temperature is 150 ° C. or lower, the substrate temperature may be damaged by heat if the temperature is higher than 150 ° C. due to the influence of plasma. preferable.
The substrate temperature may be controlled by a method not shown, or may be left to a natural temperature rise during discharge. When heating the substrate 14, a heater may be installed outside or inside the substrate 14. When the substrate 14 is cooled, a cooling gas or liquid may be circulated inside the substrate 14.
In order to avoid an increase in the substrate temperature due to the discharge, it is effective to adjust the high-energy gas flow that strikes the surface of the substrate 14. In this case, conditions such as the gas flow rate, discharge output, and pressure are adjusted so as to achieve the required temperature.

When hydrogen is added to the surface layer, hydrogen gas can be introduced from the gas introduction part 15 and the gas introduction pipe 20. In this case, it can be mixed and introduced together with a gas containing an essential component constituting the surface layer such as nitrogen or trimethylgallium gas.
As the gas containing a group 13 element, an organic metal compound containing indium or aluminum or a hydride such as diborane can be used instead of trimethylgallium gas, and two or more of these may be mixed.
For example, in the initial stage of forming the surface layer, trimethylindium is introduced into the film formation chamber 10 through the gas introduction part 15 and the shower nozzle 16, thereby forming a film containing nitrogen and indium on the substrate 14. In this case, this film can absorb ultraviolet rays that are generated when the film is continuously formed and deteriorate the base or the like. For this reason, damage to the substrate or the like due to generation of ultraviolet rays during film formation can be suppressed.

In addition, a dopant can be added to the surface layer in order to control the conductivity type.
As a dopant doping method at the time of film formation, SiH ₃ and SnH ₄ are used for n-type, and biscyclopentadienyl magnesium, dimethyl calcium, dimethyl strontium, dimethyl zinc, diethyl zinc, and the like are used for p-type. Can be used in the gas state. In order to dope the dopant element into the surface layer, a known method such as a thermal diffusion method or an ion implantation method may be employed.
Specifically, a surface layer of any conductivity type such as n-type or p-type is introduced by introducing a gas containing at least one dopant element into the film formation chamber 10 through the gas introduction unit 15 and the shower nozzle 16. Can be obtained.

Note that when an organometallic compound containing hydrogen atoms is used as a supply material for Ga and / or In and a film mainly containing Ga and / or In, hydrogen atoms, and nitrogen atoms is formed, active hydrogen activated by plasma is used. And active nitrogen can be obtained as described below.
For example, in the film forming apparatus shown in FIG. 5, when hydrogen gas and nitrogen gas are introduced into the film forming apparatus from different positions, the hydrogen gas activation state and the nitrogen gas activation state are A plurality of plasma generators may be provided so that each can be controlled independently. In contrast to this, as a supply material for hydrogen and nitrogen, a gas containing both nitrogen atoms and hydrogen atoms, such as NH ₃ , or a mixture of nitrogen gas and hydrogen gas is used. It may be activated by plasma.
Furthermore, as a hydrogen source of hydrogen activated by plasma, it is also possible to use hydrogen produced free by activating an organometallic compound containing hydrogen atoms once introduced into the film forming apparatus.

By the method as described above, activated hydrogen, nitrogen, and Ga and / or In are present on the substrate, and the activated hydrogen is a methyl group, an ethyl group, or the like constituting the organometallic compound. It has the effect of desorbing hydrogen of the hydrocarbon group as a molecule. Therefore, a surface layer made of a hard film in which hydrogen, nitrogen and Ga and / or In constitute a three-dimensional bond is formed on the surface of the substrate.
Unlike the sp2-bonding carbon atoms contained in silicon carbide, such a hard film is transparent because Ga and N form sp3 bonds like the carbon atoms constituting the tiremond. In addition, this hard film can be made into a film containing oxygen by natural oxidation or an oxidation treatment such as oxygen or ozone after the film is formed. This film is transparent and hard, and the surface of the film is water repellent or slippery. High friction and low friction.

The plasma generating means of the film forming apparatus shown in FIG. 5 uses a high-frequency oscillation device, but is not limited to this. For example, a microwave oscillation device, an electrocyclotron resonance method, or a helicon plasma is used. You may use the apparatus of a system. In the case of a high-frequency oscillation device, it may be inductive or capacitive.
Furthermore, two or more of these devices may be used in combination, or two or more of the same types of devices may be used.

When two or more types of different plasma generators (plasma generating means) are used, it is necessary to be able to generate discharges simultaneously at the same pressure. In addition, a pressure difference may be provided between the discharge region and the film formation region (the portion where the base is installed). These apparatuses may be arranged in series with respect to the gas flow formed in the film forming apparatus from the part where the gas is introduced to the part where the gas is discharged. You may arrange | position so that it may oppose.
For example, when two types of plasma generating means are installed in series with respect to the gas flow, the film forming apparatus shown in FIG. 5 is taken as an example, and a discharge is caused in the film forming chamber 10 using the shower nozzle 16 as an electrode. 2 can be used as a plasma generator. In this case, a high-frequency voltage can be applied to the shower nozzle 16 via the gas introduction part 15 to cause discharge in the film forming chamber 10 using the shower nozzle 16 as an electrode.
Alternatively, instead of using the shower nozzle 16 as an electrode, a cylindrical electrode is provided between the base 14 and the lithographic electrode 19 in the film forming chamber 10, and this film is used to form the film forming chamber 10. It is also possible to cause discharge inside.
In addition, when two different types of plasma generators are used under the same pressure, for example, when using a microwave oscillator and a high-frequency oscillator, the excitation energy of the excited species can be greatly changed, and the film quality can be controlled. It is valid. The discharge may be performed near atmospheric pressure.

In forming the surface layer, in addition to the above-described methods, a normal metal organic vapor phase epitaxy method or molecular beam epitaxy method can be used. However, in the film formation by these methods, active nitrogen and / or Alternatively, it is effective to use active hydrogen. In this case, as the nitrogen raw material, a gas or liquid such as N ₂ , NH ₃ , NF ₃ , N ₂ H ₄ , methyl hydrazine or the like vaporized or bubbled with a carrier gas can be used.
Also, O ₂ gas and H ₂ gas are mixed and introduced into the discharge electrode, and at the same time, active species are generated to decompose the trimethylgallium gas, and Ga and / or In containing hydrogen on the substrate and oxygen It is preferable to form a film with a compound of By simultaneously activating hydrogen gas and oxygen gas in plasma and reacting an organometallic compound containing Ga and / or In, a methyl group or an ethyl group contained in the organometallic gas by active hydrogen generated by plasma discharge, etc. Thus, a film of a compound containing Ga and / or In and oxygen having the same film quality as that at the time of high temperature growth even at a low temperature can be obtained on the surface of the organic substance (organic photosensitive layer). It can be formed satisfactorily without damaging the organic matter.

The electrical resistance of the charging roll thus formed is preferably in the range of 1 × 10 ⁵ or more and 1 × 10 ¹⁰ Ω or less when 500 V is applied, and preferably 1 × 10 ⁵ or more and 1 × 10 ⁹ Ω. More preferably, it is in the following range. If the electric resistance is less than 1 × 10 ⁵ Ω, current leakage (so-called leakage) may be likely to occur. If the electric resistance of the conductive roll exceeds 1 × 10 ¹⁰ Ω, charge accumulation (so-called charge-up) may occur. May be likely to occur. The electrical resistance is set by placing a charging roll on the surface of a metal plate such as a copper plate so that a load of 500 g is applied to both ends of the roll, and using a minute current measuring instrument (R8320 manufactured by Advanced Test), using a conductive roll (core material). When it has, it is the value measured by applying a voltage of 500 V between the core material) and the metal plate.

(Process cartridge and image forming apparatus)
Next, a process cartridge and an image forming apparatus using the photoreceptor of the present invention will be described.
The process cartridge of the present invention is not particularly limited as long as it uses the charging member of the present invention. Specifically, the process cartridge includes a group consisting of the charging member of the present invention, a photoreceptor, a developing unit, a cleaning unit, and a discharging unit. It is preferable that at least one selected from the above is integrally formed and can be attached to and detached from the main body of the image forming apparatus.
The image forming apparatus of the present invention is not particularly limited as long as it uses the charging member of the present invention. Specifically, the charging member of the present invention, a photoreceptor charged by the charging member, An exposure unit that exposes the surface of the photoreceptor to form an electrostatic latent image; a developing unit that develops the electrostatic latent image with a developer containing toner to form a toner image; and a transfer that transfers the toner image to a recording medium. It is preferable that it has a structure provided with a means. The image forming apparatus of the present invention may be a so-called tandem machine having a plurality of photoconductors corresponding to the toners of the respective colors. In this case, it is preferable that all the charging members are the charging members of the present invention. The toner image may be transferred by an intermediate transfer system using an intermediate transfer member.
The process cartridge and the image forming apparatus of the present invention can have a cleaning member for cleaning the surface of the charging member. By cleaning the surface of the charging member with the cleaning member, dirt on the charging member can be removed, so that the life of the process cartridge and the image forming apparatus can be extended. The cleaning member has a film shape, a plate shape, a pad shape, a roll shape, or the like, and a member such as a film, a brush, or a sponge can be used. In particular, a sponge-like member is preferable in terms of cleaning performance, and examples of the material of the sponge include ether-based urethane foam, polyethylene foam, polyolefin foam, melamine foam, and micropolymer.
Hereinafter, an example of an image forming apparatus and a process cartridge will be described in detail with reference to the drawings.

[Image forming apparatus]
FIG. 7 is a schematic configuration diagram showing a four-drum tandem full-color image forming apparatus. The image forming apparatus shown in FIG. 7 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter simply referred to as “units”) 10Y, 10M, 10C, and 10K are juxtaposed at a predetermined distance close to each other in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the main body of the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20a as an intermediate transfer member is extended through each unit. The intermediate transfer belt 20a is provided by being wound around a driving roller 22a and a support roller 24 that are in contact with the inner surface of the intermediate transfer belt 20a, spaced apart from each other from the left to the right in the drawing. It is designed to travel in the direction toward 10K. The support roller 24 is urged away from the drive roller 22a by a spring or the like (not shown), and a predetermined tension is applied to the intermediate transfer belt 20a wound around the support roller 24. An intermediate transfer member cleaning device 30a is provided on the side of the image carrier of the intermediate transfer belt 20a so as to face the drive roller 22a.
Further, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K includes yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The four color toners can be supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first unit that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction. 10Y will be described as a representative. Note that the second to fourth units are denoted by reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y) in the same parts as the first unit 10Y. Description of 10M, 10C, 10K is omitted.

The first unit 10Y has a photoreceptor 1Y that functions as an image holding member. Around the photoreceptor 1Y, an electrostatic charge image is formed by exposing the surface of the photoreceptor 1Y to a predetermined potential with a charging roller 2Y and the charged surface with a laser beam 3Y based on the color-separated image signal. An exposure device 3; a developing device (developing means) 4Y for supplying the charged toner to the electrostatic image to develop the electrostatic image; a primary transfer roller 5Y (primary) for transferring the developed toner image onto the intermediate transfer belt 20a; A transfer unit), and a photoconductor cleaning device (cleaning unit) 6Y for removing toner remaining on the surface of the photoconductor 1Y after the primary transfer.
The primary transfer roller 5Y is disposed inside the intermediate transfer belt 20a, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rollers 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roller under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of about −600V to −800V by the charging roller 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less). This photosensitive layer usually has a high resistance (a resistance equivalent to that of a general resin), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3a in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow print pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic image formed on the photoreceptor 1Y in this way is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) by the developing device 4Y.

  In the developing device 4Y, for example, yellow toner having a volume average particle diameter of 7 μm including at least a yellow colorant, a crystalline resin, and an amorphous resin is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. . The photoreceptor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer, a predetermined primary transfer bias is applied to the primary transfer roller 5Y, and the electrostatic force directed from the photoreceptor 1Y to the primary transfer roller 5Y generates a toner image. The toner image on the photoreceptor 1Y is transferred onto the intermediate transfer belt 20a. The transfer bias applied at this time is a (+) polarity opposite to the polarity (−) of the toner, and is controlled to about +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rollers 5M, 5C, and 5K after the second unit 10M is also controlled according to the first unit.
Thus, the intermediate transfer belt 20a onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner.

  The intermediate transfer belt 20a on which the toner images of four colors are transferred in multiple numbers through the first to fourth units is disposed on the intermediate transfer belt 20a, the support roller 24 that contacts the inner surface of the intermediate transfer belt 20a, and the image holding surface side of the intermediate transfer belt 20a. The secondary transfer roller (secondary transfer means) 26 is connected to a secondary transfer portion. On the other hand, a recording sheet (transfer object) P is fed at a predetermined timing into a gap where the secondary transfer roller 26 and the intermediate transfer belt 20a are pressed against each other via a supply mechanism, and a predetermined secondary transfer bias is supported. Applied to the roller 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20a toward the recording paper P is applied to the toner image, and the transfer bias is applied to the intermediate transfer belt 20a. The toner image is transferred onto the recording paper P. Note that the secondary transfer bias at this time is determined according to the resistance detected by a resistance detecting means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

Thereafter, the recording paper P is sent to a fixing device (fixing means) 28, where the toner image is heated, and the color-superposed toner image is melted and fixed on the recording paper P. The recording paper P on which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.
The image forming apparatus exemplified above is configured to transfer the toner image onto the recording paper P via the intermediate transfer belt 20a. However, the present invention is not limited to this configuration, and the toner image can be directly transferred from the photoreceptor. It may be a structure that is transferred to a recording sheet.

When the toner recycling means is provided, the system is not particularly limited. For example, the toner collected by the cleaning unit is supplied to a replenishing toner hopper, a developing device, or a replenishing toner by a transporting conveyor or a transporting screw. And a method of mixing them in the intermediate chamber and supplying them to the developing device. Preferably, a method of returning directly to the developing unit or a method of mixing and supplying the replenishing toner and the recycled toner in the intermediate chamber can be given.
When the toner is recycled as described above, it is necessary that the strength of the toner particles is high and the dispersibility inside the toner of the release agent is good and the toner is not exposed to the surface. Therefore, even when used for a long period of time, the image quality is not deteriorated.

[Process cartridge]
FIG. 8 is a schematic configuration diagram showing a preferred example of a process cartridge containing the electrostatic charge image developer of the present invention. In the process cartridge 200, a charging roller 108, a developing device 111, a photoconductor cleaning device (cleaning means) 113, an opening 118 for exposure, and an opening 117 for static elimination exposure are attached to a rail 116 together with the photoconductor 107. Are combined and integrated with each other.
The process cartridge 200 is detachable from an image forming apparatus main body including a transfer device 112, a fixing device 115, and other components (not shown). It forms a forming apparatus. Reference numeral 300 denotes a recording sheet.

  The process cartridge shown in FIG. 8 includes a charging roller 108, a developing device 111, a cleaning device (cleaning means) 113, an opening 118 for exposure, and an opening 117 for static elimination exposure. Can be selectively combined. In the process cartridge of the present invention, in addition to the photosensitive member 107, the charging roller 108, the developing device 111, the cleaning device (cleaning means) 113, the opening 118 for exposure, and the opening 117 for static elimination exposure. It comprises at least one selected from the group consisting of.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
(Example 1)
In order to form an elastic layer, the following mixture is kneaded with an open roll, coated on the surface of a conductive support made of SUS416 with a diameter of 8 mm so as to have a thickness of 3 mm, and a cylindrical shape with an inner diameter of 14.0 mm The base roll 1 in which a cylindrical elastic layer is formed by vulcanizing at 170 ° C. for 30 minutes, taking out from the mold, and polishing to form a cylindrical elastic layer whose central layer is thinner than the end layer. Obtained. The difference in the outer diameter between the central portion and the end portion was 85 μm.
・ Rubber material: 100 parts by weight (epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber: Gechron 3106: manufactured by Nippon Zeon Co., Ltd.)
-Conductive agent (Carbon Black Asahi Thermal: Asahi Carbon Co., Ltd.) ... 25 parts by weight-Conductive agent (Ketjen Black EC: Lion Corp.) ... 8 parts by weight-Ionic conductive agent (lithium perchlorate) -1 part by weight-Vulcanizing agent (sulfur) (200 mesh: manufactured by Tsurumi Chemical Co., Ltd.) ... 1 part by weight-Vulcanization accelerator (Noxeller DM: manufactured by Ouchi Shinsei Chemical Co., Ltd.) 0 parts by weight, vulcanization accelerator (Noxeller TT: Ouchi Shinsei Chemical Co., Ltd.) ・ ・ ・ 0.5 parts by weight

-Formation of surface layer-
A surface layer was formed using a film forming apparatus (hereinafter referred to as “plasma CVD apparatus” as appropriate) having the structure shown in FIG. 9 with the elastic layer of the base roll 1 as a base.
-Formation of surface layer-
A surface layer was formed using a film forming apparatus having the configuration shown in FIG. 9 with the elastic layer of the base roll 1 as a base.
First, a Si substrate (5 mm × 10 mm) for preparing a reference sample is attached to the base with an adhesive tape, introduced into the plasma CVD apparatus shown in FIG. 9, and the pressure inside the vacuum chamber 32 is 1 × 10 ⁻² Pa. It was evacuated until. Next, 200 sccm of hydrogen gas and 100 sccm of nitrogen gas are supplied from the gas supply pipe 34 via the mass flow controller 36, and 1 sccm of hydrogen diluted trimethylgallium (about 10 vol%) is supplied from the gas introduction pipe 64 via the source gas supply source 62. The pressure in the vacuum chamber 32 is set to 40 Pa by supplying the vacuum chamber 32 and adjusting the conductance valve (not shown), and the radio wave of 13.56 MHz is set to the output 80 W by the high frequency power source 58 and the matching box 56. Then, matching was performed with a tuner, and discharge was performed from the discharge electrode 54. The reflected wave at this time was 0 W. In this state, a film was formed while rotating at a speed of 20 rpm for 100 minutes to obtain a charging member with a surface layer. The hydrogen-diluted trimethylgallium gas was supplied by bubbling hydrogen into a trimethylgallium kept at 0 ° C. using hydrogen as a carrier gas.

A film having a thickness of 0.2 μm was formed on the elastic layer. Note that the base was not heat-treated during film formation. In addition, when the color of a temperature measurement sticker (manufactured by Wahl, Temp Plate P / N101) previously attached to the surface of the base before film formation under the same conditions was confirmed after film formation, it was at 35 ° C. there were.
Subsequently, the substrate after film formation is left in a normal room temperature and normal humidity environment (temperature of about 25 ° C., humidity of about 50%) for 24 hours, and is subjected to an oxidation treatment by natural oxidation to provide a surface layer on the elastic layer. The obtained roll-shaped charging member (charging roll 1) was obtained.

-Analysis and evaluation of surface layer-
Rutherford backscattering (RBS) and hydrogen forward scatter after leaving the surface of the film formed on the Si substrate for about 24 hours after film formation in the same room temperature and humidity environment as in the above-mentioned environment where contamination is difficult to adhere. When the composition of the film was measured by a ring, oxygen was 60 atomic% and Ga was 40 atomic% at 5 nm from the outermost surface, and nitrogen was not recognized. On the other hand, at 50 nm from the surface, oxygen was 3 atomic%, Ga was 30 atomic%, nitrogen was 31%, and hydrogen was 36 atomic%. From this result, the outermost surface of the surface layer is in an oxygen-rich and nitrogen-poor state, and the concentration of oxygen atoms in the surface layer thickness direction decreases toward the base side (the concentration of nitrogen atoms toward the base side). Increased).

Furthermore, no dots or lines were found in the diffraction image obtained by RHEED (reflection high-energy electron diffraction) measurement, indicating that the film was amorphous.
The film formed on the Si substrate immediately after the film was dissolved when immersed in water, but the film after being left in a normal room temperature and humidity environment for 1 week did not dissolve even when immersed in water. There was no damage even when rubbed with steel.
From the above analysis and evaluation results, the surface layer formed through film formation and oxidation treatment is amorphous and has a composition containing oxygen in addition to hydrogen, nitrogen, and gallium. It was found that the film had a distribution in which the concentration of oxygen atoms relative to the direction was the richest on the outermost surface and decreased toward the base side.

  A peeling test was conducted to peel off the attached adhesive tape on the surface of the charging roll 1 provided with the surface layer, but it was found that the surface layer did not peel at all and the adhesiveness was good.

<Evaluation of Charging Characteristics and Surface State of Charging Roll 1>
[Charging characteristics of charging roll 1]
The charging property of the charging roll 1 is attached to a DocuCentre Color a450 manufactured by Fuji Xerox Co., Ltd. with the cleaning brush of the charging member removed. ) Were printed one by one, and the uniform charging performance was evaluated by evaluating the image quality of blank images and halftone images obtained at the initial printing and after printing 10,000 sheets.
The results are listed in Table 1.

-Evaluation criteria for uniform charging performance-
The uniform charging performance was evaluated according to the following criteria with respect to the initial image quality and the image quality after printing 50,000 sheets.
○: There is no defect in image quality.
Δ: Black spots or black streaks appear on the blank paper image, and / or black spots, white spots, streaks appear slightly on the halftone image.
X: Black spots or black streaks appear on the blank paper image, and / or black spots, white spots, streaks appear on the halftone image.
XX: Remarkably many black spots, black streaks, and / or black spots, white spots, streaks, etc. appear in the blank image.
Note that the charging performance is stable and maintained when there is no deterioration in the image quality based on the image quality evaluation after the initial printing in the low-temperature / low-humidity and high-temperature / high-humidity environment and after printing 10,000 sheets. Judged to be excellent.

[Evaluation of surface condition]
The surface state of the charging member produced as described above was visually observed.
The results are listed in Table 1.

-Surface condition evaluation criteria-
○: There is no scratch on the surface of the charging member, and there is no dirt.
(Triangle | delta): A crack and / or dirt are weak, and it exists in a part.
X: Scratches and / or dirt is weak and is present on the entire surface.
XX: Scratches and / or dirt is severe and is on the entire surface.

(Example 2)
A surface layer was formed by plasma CVD on the elastic layer of the base roll 1 produced in the same manner as in Example 1.
A Si substrate (5 mm × 10 mm) for preparing a reference sample is attached to the base with an adhesive tape, introduced into the plasma CVD apparatus shown in FIG. 9, and the pressure in the vacuum chamber 32 is 1 × 10 ⁻² Pa. Evacuated. Next, 200 sccm of hydrogen gas, 5 sccm of He diluted oxygen (4 vol%) are supplied from the gas supply pipe 34 via the mass flow controller 36, and 1 sccm of hydrogen diluted trimethylindium (about 2 vol%) is supplied via the source gas supply source 62. By supplying the gas from the gas introduction pipe 64 to the vacuum chamber 32 and adjusting the conductance valve, the pressure in the vacuum chamber 32 is set to 20 Pa, and the radio wave of 13.56 MHz is output 80 W by the high frequency power source 58 and the matching box 56. The discharge electrode 54 was discharged by matching with a tuner. The reflected wave at this time was 0 W. In this state, a film was formed while rotating at a speed of 20 rpm for 80 minutes to obtain a charging member with a surface layer. The hydrogen-diluted trimethylindium gas was supplied by bubbling hydrogen into a trimethylindium maintained at 20 ° C. using hydrogen as a carrier gas. The temperature at the time of film formation was found to be about 40 ° C. or less from the color of the temperature measurement sticker (Wahl, Temp Plate P / N101). The obtained charging member was allowed to stand for 24 hours in an environment at a temperature of 20 ° C. to obtain a roll-shaped charging member (charging roll 2).
The charging roll 2 thus obtained was evaluated in the same manner as in Example 1.

-Analysis and evaluation of surface layer-
When the cross section obtained by cleaving the Si reference sample was observed with a scanning electron microscope (SEM), the film thickness was 0.25 μm.
Further, composition analysis of the film formed on the Si reference sample was performed by Rutherford backscattering (RBS) and hydrogen forward scattering (HFS). In: 38 atomic%, O: 42 atomic%, H: The atomic composition ratio (O / In) of oxygen and indium was 1.10.

(Example 3)
-Formation of surface layer-
A surface layer was formed by plasma CVD on the elastic layer of the base roll 1 produced in the same manner as in Example 1. A Si substrate (5 mm × 10 mm) for preparing a reference sample is attached to the base with an adhesive tape, introduced into the plasma CVD apparatus shown in FIG. 9, and the pressure in the vacuum chamber 32 is 1 × 10 ⁻² Pa. Evacuated. Next, 200 sccm of hydrogen gas, 5 sccm of He diluted oxygen (4 vol%) are supplied from the gas supply pipe 34 via the mass flow controller 36, and 1 sccm of hydrogen diluted trimethylgallium (about 10 vol%) are supplied via the source gas supply source 62. By supplying the gas from the gas introduction pipe 64 to the vacuum chamber 32 and adjusting the conductance valve, the pressure in the vacuum chamber 32 is set to 20 Pa, and the radio wave of 13.56 MHz is output 80 W by the high frequency power source 58 and the matching box 56. The discharge electrode 54 was discharged by matching with a tuner. The reflected wave at this time was 0 W. In this state, a film was formed while rotating at a speed of 20 rpm for 73 minutes to obtain a charging member with a surface layer. The hydrogen-diluted trimethylgallium gas was supplied by bubbling hydrogen into a trimethylgallium kept at 0 ° C. using hydrogen as a carrier gas. It was found from the color of the affixed thermo tape that the temperature during film formation was about 40 ° C. or lower. The obtained charging member was allowed to stand for 24 hours in an environment at a temperature of 20 ° C. to obtain a roll-shaped charging member (charging roll 3).
The charging roll 3 thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

-Analysis and evaluation of surface layer-
When the cross section obtained by cleaving the Si reference sample was observed with a scanning electron microscope (SEM), the film thickness was 0.31 μm.
Further, when composition analysis of the film formed on the Si reference sample was performed by Rutherford backscattering (RBS) and hydrogen forward scattering (HFS), Ga: 36 atomic%, O: 44 atomic%, H: The atomic composition ratio (O / Ga) of oxygen and gallium was 1.22.

Example 4
In the production of the charging member of Example 3, an electrophotographic photosensitive member with a surface layer was prepared in the same manner as in Example 3 except that the amount of oxygen supplied during formation of the surface layer was 3 sccm and the film formation time was 85 minutes. Obtained.
When this photoconductor was observed by SEM of the cross section in the same manner as in Example 3, the film thickness was 0.32 μm. When elemental analysis was performed in the same manner, the elemental composition was Ga: 38 atomic%, O: 41 atomic%, H: 21 atomic% (sum of the composition ratio of the three elements: 1.0), oxygen And the elemental composition ratio (O / Ga) of gallium was 1.08.
The charging roll 4 thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

(Example 5)
In the production of the charging member of Example 3, a charging member with a surface layer was obtained in the same manner as in Example 3 except that the amount of oxygen supplied during formation of the surface layer was 20 sccm and the film formation time was 60 minutes. .
With respect to this charging member, when a cross-sectional SEM observation was performed in the same manner as in Example 3, the film thickness was 0.30 μm. When elemental analysis was performed in the same manner, the elemental composition was Ga: 35 atomic%, O: 50 atomic%, H: 15 atomic% (sum of the composition ratio of the three elements: 1.0), oxygen And the elemental composition ratio (O / Ga) of gallium was 1.43.
The charging roll 5 thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

(Comparative Example 1)
With respect to the elastic layer produced in the same manner as in Example 1, a surface layer was formed by the following procedure using an apparatus having the same configuration as in Example 1 and shown in FIG.
First, a Si substrate (5 mm × 10 mm) for preparing a reference sample is attached to the base with an adhesive tape, introduced into the plasma CVD apparatus shown in FIG. 9, and the pressure inside the vacuum chamber 32 is 1 × 10 ⁻² Pa. It was evacuated until. Next, 200 sccm of hydrogen gas and 100 sccm of nitrogen gas are supplied from the gas supply pipe 34 via the mass flow controller 36, and 1 sccm of hydrogen diluted trimethylaluminum (about 10 vol%) is supplied from the gas introduction pipe 64 via the source gas supply source 62. By adjusting the conductance valve while supplying to the vacuum chamber 32, the pressure in the vacuum chamber 32 is set to 40 Pa, and a radio wave of 13.56 MHz is set to an output of 80 W by the high frequency power source 58 and the matching box 56, and the tuner is used. Matching was performed and discharge was performed from the discharge electrode 54. The reflected wave at this time was 0 W. In this state, a film was formed while rotating at a speed of 20 rpm for 100 minutes to obtain a charging member with a surface layer. The hydrogen-diluted trimethylaluminum gas was supplied by bubbling hydrogen into a trimethylaluminum kept at 20 ° C. using hydrogen as a carrier gas. In the film formation, the heat treatment was not performed as in Example 1.

After forming a surface layer having a thickness of 0.2 μm in this way, a mixed gas of helium and oxygen (100 sccm helium, 10 sccm oxygen) is supplied from the gas supply pipe 34 to the vacuum chamber 32 via the mass flow controller 36. In addition, by adjusting the conductance valve, the pressure in the vacuum chamber 32 is set to 40 Pa, the radio wave of 13.56 MHz is set to an output of 100 W by the high frequency power source 58 and the matching box 56, matching is performed by the tuner, and the discharge electrode 54 Discharge was performed. The reflected wave at this time was 0 W. In this state, the oxidation treatment was performed by rotating at a speed of 20 rpm for 10 minutes. Thereafter, the comparative charging roll 1 on which the surface layer having been subjected to the oxidation treatment was formed was taken out from the film forming chamber 32.
The comparative charging roll 1 thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

-Analysis and evaluation of surface layer-
When the surface of the film formed on the Si substrate was measured by Rutherford backscattering (RBS), the composition of 5 nm from the outermost surface was oxygen 70 atom%, Al 30 atom%, and nitrogen was not recognized. It was found that aluminum oxide was formed on the outermost surface of the film. On the other hand, at 50 nm from the surface, oxygen was 9 atomic%, Al was 34 atomic%, nitrogen was 28%, and hydrogen was 29 atomic%. From this result, the outermost surface of the surface layer is in a state where there is much oxygen and nitrogen is low, and the concentration of oxygen atoms in the surface layer thickness direction decreases toward the base side (the concentration of nitrogen atoms on the base side). It was found that it was increasing).

Furthermore, no dots or lines were found in the diffraction image obtained by RHEED (reflection high-energy electron diffraction) measurement, indicating that the film was amorphous. The film formed on the Si substrate was transparent and was not damaged even when rubbed with stainless steel.
From the above analysis and evaluation results, the surface layer formed through film formation and oxidation treatment is amorphous and has a composition containing oxygen in addition to hydrogen, nitrogen, and aluminum. It was found that the film had a distribution in which the concentration of oxygen atoms relative to the direction was highest on the outermost surface and decreased toward the base side.

Next, the uniform charging performance of the comparative charging roll 1 was evaluated in the same manner as in Example 1.
The results are shown in Table 1.
However, cracks in the surface layer were observed in the surface observation, fine image quality defects were generated under high temperature and high humidity conditions, and the maintainability was inferior to a certain degree of practical problem.
From the above results, it was found that the comparative charging roll 1 provided with a surface layer containing an Al element has a problem in terms of maintainability under high temperature and high humidity conditions, although it is at a level where there is no practical problem under low temperature and low humidity conditions.

(Comparative Example 2)
A surface layer was formed by using 99.99% purity alumina as a target by RF sputtering. The sputtering conditions were Ar gas flow rate of 50 sccm, pressure of 0.5 Pa, RF power of 200 W, film formation time of 3 minutes, and film formation was performed while rotating the roll formed with the same elastic layer as in Example 1 at 100 rpm. .
The comparative charging roll 2 thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

(Comparative Example 3)
In order to form a resistance layer on the elastic layer of the roll on which the elastic layer of Example 1 was formed, a dispersion obtained by dispersing the following mixture in a bead mill was diluted with methanol to obtain a coating solution for the resistance layer. It was. This coating solution was applied to the surface of the elastic layer by a dip coating method, and then heated and dried at 150 ° C. for 15 minutes to form a 10 μm resistance layer, whereby a comparative charging roll 3 was obtained.
The comparative charging roll 3 thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.
-Polymer material (copolymer nylon) Alamine CM8000: 100 parts by weight manufactured by Toray Industries, Inc.-Conductive agent (carbon black) MONARCH1000: 12 parts by weight manufactured by Cabot Corporation-Solvent (methanol) 500 parts by weight-Solvent (butanol) 240 parts by weight

(Comparative Example 4)
With respect to the elastic layer of the base roll 1 produced in the same manner as in Example 1, a surface layer was formed by the following procedure using an apparatus having the same configuration as in Example 1 and shown in FIG.
First, a Si substrate (5 mm × 10 mm) for preparing a reference sample is attached to the base with an adhesive tape, introduced into the plasma CVD apparatus shown in FIG. 9, and the pressure inside the vacuum chamber 32 is 1 × 10 ⁻² Pa. It was evacuated until. Next, by supplying 100 sccm of methane gas from the gas supply pipe 34 to the vacuum chamber 32 via the mass flow controller 36 and adjusting the conductance valve, the pressure in the vacuum chamber 32 is set to 13 Pa, and the high frequency power source 58 and the matching box 56 are used. A 13.56 MHz radio wave was set to an output of 300 W, matching was performed by a tuner, and discharge was performed from the discharge electrode 54. The reflected wave at this time was 0 W. In this state, the film was formed while rotating at a speed of 10 rpm for 60 minutes to obtain a charging member with a diamond-like carbon film having a thickness of 0.2 μm.
In the film formation, the heat treatment was not performed as in Example 1.
The comparative charging roll 4 thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

  As described above, the charging member of the present invention is excellent in oxidation resistance and contamination resistance, and has mechanical durability, that is, excellent uniform charging performance in any environment of low temperature / low humidity and high temperature / high humidity. I found out.

(Example 6)
In the same manner as in Example 1, after producing the base roll 1 having an elastic layer formed on the substrate, a ta-C layer was formed on the elastic layer using an FCVA apparatus (Shimadzu Corporation). The conditions were a film forming temperature of 40 ° C. and a film forming speed of 1.5 nm / s. In order to form a uniform layer, a roll composed of a substrate and an elastic layer was rotated at 30 rpm. In this way, a ta-C layer having a thickness of 1.2 μm was formed. As described above, the binding state was evaluated by Raman spectroscopy, and as a result, it was found that the ratio of sp3 bonds was 47%. A surface layer was formed on such a ta-C layer in the same manner as in Example 1 to obtain a charging roll.

[Evaluation of the presence or absence of bleeding]
The charging roll was assembled in a drum cartridge of a Fuji Xerox color copier DocuCenter Color a450 and brought into contact with the photoreceptor, and left for 7 days under severe conditions of a temperature of 50 ° C. and a relative humidity of 95%. After that, the aircraft was pictured and inspected. Halftone, black, and white images were produced, and “◯” if there was no effect on the image, “Δ” if there was a local or minor effect, and “X” if there was a significant effect.
The results are shown in Table 2.

[Evaluation results after printing 10,000 sheets]
In the same manner as in Example 1, 10,000 sheets were printed under low temperature / low humidity conditions and high temperature / high humidity conditions, respectively, and the image quality of blank images and halftone images obtained after the initial printing and after printing 10,000 sheets were evaluated. Thus, the uniform charging performance was evaluated.
The results are shown in Table 2.

(Examples 7 to 9, Comparative Example 5)
In Example 6, a charging roll was produced in the same manner as in Example 6 except that the thickness of the ta-C layer and the thickness of the surface layer were as shown in Table 2, and the presence or absence of bleeding was evaluated.
The results are shown in Table 2.

  As described above, the charging member of the present invention can draw a high-quality image while suppressing bleeding even when left for a long period of time in a high humidity environment.

It is a schematic cross section showing an example of a layer structure of the charging member of the present invention. It is a schematic cross section which shows the other example of the layer structure of the charging member of this invention. It is a schematic cross section which shows the other example of the layer structure of the charging member of this invention. It is a schematic cross section which shows the other example of the layer structure of the charging member of this invention. It is a schematic diagram showing an example of a film forming apparatus used for forming the surface layer of the charging member of the present invention. FIG. 6 is a schematic diagram showing another example of a plasma generator that can be used in the film forming apparatus shown in FIG. 5. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention. It is a schematic block diagram which shows an example of the process cartridge of this invention. It is a schematic diagram showing an example of a film forming apparatus used for forming the surface layer of the charging member of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive base | substrate 2 Elastic layer or resin layer 3 Surface layer 4 Resistance layer 5 Base | substrate 6 Conductive layer 7 Tetrahedral amorphous carbon layer 10 Deposition chamber 11 Exhaust port 12 Base | substrate rotation part 13 Base | substrate holder 14 Base | substrate 15 Gas introduction part 16 Shower nozzle 17 Plasma diffusion unit 18 High frequency power supply unit 19 Flat plate electrode 20 Gas introduction tube 21 High frequency discharge tube unit 22 High frequency coil 23 Quartz tube 30 Film forming apparatus (plasma CVD apparatus)
32 Vacuum chamber 34 Gas supply pipe 36 Mass flow controller 38 Pressure regulator 40 Gas supply source 42 Exhaust pipe 48 Motor 50 Non-coated photoreceptor 54 Discharge electrode 56 Matching box 58 High frequency power supply 60 Carrier gas supply source 62 Raw material gas supply source 64 Gas introduction pipe 1Y, 1M, 1C, 1K, 107 photoconductor (image carrier)
2Y, 2M, 2C, 2K, 108 Charging roller 3Y, 3M, 3C, 3K Laser beam 3a Exposure device 4Y, 4M, 4C, 4K, 111 Developing device (developing means)
5Y, 5M, 5C, 5K Primary transfer rollers 6Y, 6M, 6C, 6K, 113 Photoconductor cleaning device (cleaning means)
8Y, 8M, 8C, 8K toner cartridges 10Y, 10M, 10C, 10K unit 112 transfer device 116 mounting rail 117 opening 118 for static elimination exposure opening 100 for exposure 100 image forming apparatus 200 process cartridge,
P, 300 Recording paper (transfer object)

Claims (8)

  The surface layer includes at least one selected from the group consisting of oxygen and Ga and In as a metal element at least on the outermost surface portion of the surface layer, and included in at least the outermost surface portion of the surface layer. A charging member having an oxygen content of 15 atomic% or more.   The charging member according to claim 1, wherein the metal element is Ga.   The charging member according to claim 1, wherein at least an outermost surface portion of the surface layer contains hydrogen.   Of the elements constituting at least the outermost surface portion of the surface layer, the sum of the constituent ratios with respect to the total element amount of the metal element and oxygen, or the metal element, oxygen and hydrogen is 0.95 or more, and The charging member according to any one of claims 1 to 3, wherein a composition ratio (oxygen / metal element) of the oxygen and the metal element is 1.1 or more and 1.5 or less.   5. The charging member according to claim 1, wherein a concentration distribution of oxygen contained in the surface layer in a thickness direction of the surface layer decreases toward a lower layer side.   The charging member according to any one of claims 1 to 5, wherein a tetrahedral amorphous carbon layer and an elastic layer are sequentially provided on the lower layer side of the surface layer from the surface layer side.   A process cartridge comprising the charging member according to claim 1.   An image forming apparatus comprising the charging member according to claim 1.

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