JP2002278223A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image quality such as lowering of resolution, image flowing, an uneven image, etc., from deteriorating under high humidity surroundings, to heighten durability of a photosensitive body, and further to prevent ozone and nitrogen oxide from being generated in an image forming device. SOLUTION: The photosensitive body 11 with a coating layer comprising dispersed inorganic particulates, an electrifying member 13 mainly comprising a material with catalytic activity and electrical conductivity and a surface adjusting member 21 to clean a surface of the photosensitive body 11 are provided on an image forming part of the image forming device. Preferably the electrifying member 13 is chiefly constructed with activated carbon fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a facsimile,
The present invention relates to an image forming apparatus such as a laser printer and a digital copying machine that forms an image by an electrophotographic method. In particular, it relates to the characteristics and materials of the photoreceptor, charging member and surface property adjusting member.

[0002]

2. Description of the Related Art In an image forming apparatus such as a facsimile, a laser printer, a digital copying machine, etc., which forms an image by an electrophotographic system, various devices for charging, exposing, developing, transferring, cleaning, removing electricity, etc., centering on a photosensitive member. Is provided, and an image is formed by sequentially operating these devices. Photoreceptors include selenium-based, silicon-based, and organic-based photoconductors.In recent years, organic photoconductors are mainly used because they are easy to obtain high sensitivity, easy to manufacture, and low in cost. Is done.

[0003] However, the organic photoreceptor has a problem that the photoreceptor itself has low hardness because the photosensitive layer is mainly composed of resin, and is liable to wear due to low tensile strength and high friction coefficient, and low durability. There is. In addition, the photoreceptor is charged when forming an image, but the charging means generally used at present is accompanied by discharge, so that the corona product which becomes a contaminant to the photoreceptor such as ozone and nitrogen oxide at the time of charging. Occurs. When this corona product is generated, it reduces the surface resistance by adhering to the photoreceptor surface,
Causes a decrease in resolution. In addition, by impregnating the photosensitive layer, the mechanical durability and the image forming characteristics are reduced, and the toner composition and paper powder are easily attached to the photoreceptor, thereby lowering the cleaning performance and the transfer efficiency. And the uniformity of the formed image is impaired. Further, if the coefficient of friction of the photosensitive layer on the surface of the photoconductor increases due to the adhesion of a corona product or the like, the image forming apparatus using the cleaning blade not only accelerates the abrasion of the photosensitive layer, but also increases the photoconductor and the cleaning blade. Problems such as blade squealing caused by rubbing against each other also occur.
In particular, in an image forming apparatus that performs negative charging, the amount of corona product generated is large, and the more durable photoreceptor is, the more difficult it is to scrape, so that the corona product accumulates and the effect on image quality is increased.

[0004] Since these problems are wide-ranging, an improvement method according to the situation is required, and many improvement methods have been disclosed. Methods for improving the durability of the photoreceptor against corona products are roughly classified into the following four methods. (A) The wear resistance of the photoconductor itself is increased. (B) The surface friction coefficient of the photoreceptor is controlled to reduce the wear of the photosensitive layer. (C) Corona products that adversely affect the photoreceptor depending on the type and configuration of the charging device are eliminated or suppressed. (D) Eliminating or mitigating the influence of image-causing substances adhering to the photoreceptor surface. There are four.

[0005] Each of these will be described below. (A) Method for Enhancing Abrasion Resistance of Photoreceptor As a method generally adopted to improve the durability of the photoreceptor, a method of laminating a coating layer for enhancing durability on a surface layer of the photoreceptor is exemplified. Can be Examples of a method for forming a wear-resistant coating layer or a protective layer include a method for forming a thin film having a volume resistivity of about 10 ¹⁰ to 10 ¹⁴ Ω · cm by vapor deposition, a plasma CVD method, or the like; There is a method in which a resin liquid in which fine particles such as an oxide or a granular resin are dispersed is coated on the surface of the photoreceptor by dip coating or spray coating.

For example, as a method for forming an amorphous carbon film (a-C film) on a photosensitive layer by using a CVD method, there is a photoreceptor having a surface protective layer made of an alkali-treated a-C film. Japanese Patent Application Laid-Open No. Hei 1-292756 discloses an electrophotographic photoreceptor having a surface protective layer formed of an amorphous carbon nitride film (amorphous carbon film). The formed electrophotographic photoreceptor is disclosed in JP-A-4-66954. There are the following disclosure examples of those in which conductive fine particles (filler) are dispersed in a protective layer or a surface layer of a photoreceptor and an image is formed by a contact charging method.

[0007] 1) JP-A-6-35220 As the conductive fine particles, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide,
A layer in which fine particles such as tin-doped indium oxide are dispersed is formed on the outermost surface of the photoconductor. 2) JP-A-8-123053 0.02 to 5 μm (preferably 0.
07-2.0 μm) of a butadiene-based charge transport material containing inorganic compound particles (eg, metal oxides such as silica, aluminum oxide, zinc oxide, and aluminum nitride, metal sulfides, and metal nitrides). Formed on the outermost surface of the photoconductor.

3) JP-A-8-234455 A charge-transporting layer having a thickness of 12 μm or less is provided as the conductive fine particles with silicone resin, phenol resin, SiO ₂ , Al ₂ O ₃ , TiO _{2 having} a particle size of 1 to 3 μm. , ZnO are formed on the outermost surface of the photoconductor. 4) JP-A-8-234469 A layer in which a metal oxide composed of tin oxide, tin oxide and antimony oxide or both of them are dispersed in a thermosetting resin (thermosetting polyurethane) as conductive inorganic fine particles is exposed to light. Form on the outermost surface of the body.

5) JP-A No. 8-146641 One or two types of polycarbonate resins using inorganic compound fine particles such as titanium oxide, aluminum oxide and silicon oxide having an average particle diameter of 0.02 to 5.0 μm as conductive inorganic fine particles. A layer dispersed therein is formed on the outermost surface of the photoconductor. 6) Japanese Patent Application Laid-Open No. H8-248663 A surface layer having a surface roughness of 0.1 to 0.5 μm formed on a conductive support having a surface roughness of 0.01 μm to 2.0 μm has an average particle size of 0 μm. A photosensitive member having a protective layer thickness of 0.05 to 15 μm, in which inorganic fine particles of 0.05 to 0.5 μm (hydrophobized silica) are dispersed as conductive inorganic fine particles.

(B) A method of controlling the surface friction coefficient of the photoreceptor to reduce the abrasion of the photosensitive layer 1) Japanese Patent Application Laid-Open No. 8-202226 Japanese Patent Application Laid-open No. 8-202226 A device for applying the carrier to the carrier via a brush is installed in the cleaning unit. 2) Japanese Patent Application Laid-Open No. 8-305233 An image forming apparatus having a control device for detecting a toner image formed on an image carrier and applying a lubricant in accordance with the reference value, wherein zinc stearate is used as the lubricant. Is used. 3) JP-A-6-342236 A lubricant (such as zinc stearate) is applied to an image carrier via a charging roller.

4) JP-A-53-133439, JP-A-54-1630, and JP-A-54-143142.
JP-A-64-35448, JP-A-63-35448
No. 244039, etc. A silicone-based or fluorine-based lubricant is contained or applied to the outermost layer of the photosensitive layer, or a layer containing these lubricants is provided on the photosensitive member. 5) Japanese Patent Application Laid-Open No. 9-251263 A solid lubricant applied to the peripheral surface of the application roller by bringing the solid lubricant into contact with the peripheral surface of the application roller and swinging the solid lubricant in a direction perpendicular to the axial direction. The material is applied to the photoreceptor surface via a rotating application brush.

(C) A method for eliminating or suppressing corona products which adversely affect the photoreceptor by the method and configuration of the charging device. it can. The discharge electrode has a needle electrode structure. Ion absorption of shield case and grid of charging device,
It is composed of a material having a decomposition function (catalysis). A contact charging system is used in which a charge is applied to the photoconductor by bringing the charging member into contact with the photoconductor.

In the method (1), the discharge area is reduced by using a nickel-plated needle-like electrode as the discharge electrode, the discharge efficiency is increased, and as a result, the generation of corona products is suppressed. For example, a corona discharge device having a saw-tooth, comb-tooth or multi-needle discharge member is disclosed in Japanese Patent Application Laid-Open No. 7-5 / 1995.
Japanese Unexamined Patent Publication No. Hei.
JP-A-160711 discloses a corona discharge device including a plurality of linear conductive members and an electrode member commonly connected to at least a part of a non-discharge end thereof. A charging device having a flat grid electrode having an opening is disclosed in Japanese Patent Application Laid-Open No. 8-171257. The discharge amount can be reduced by arranging the needle electrodes to be discharged at intervals of, for example, 2 mm and making the surface to be discharged not continuous but dotted. Furthermore, the discharge efficiency can be increased by using a needle-shaped electrode as the discharge electrode. Therefore, even if there is a grid provided for uniform charging, the amount of corona products generated can be reduced to one-tenth of the conventional value, which is a significant environmental improvement. Nevertheless, its production is large.

The method includes a method in which the shield case and the grid of the charging device are made of activated carbon fibers, a method in which the grid is nickel-plated, and a method in which a catalyst is disposed in the shield case. Documents that disclose these methods include, for example, the following. (1) JP-A-63-31365 A shield member and a grid member are integrally formed of activated carbon fiber, and further, a powder of Ti, Fe, Sn, MnO or the like is carried thereon to adsorb and decompose a corona product, Corona charger that reduces the effect on the photoconductor.

(2) JP-A-1-210974 A corona discharge device in which a sheet made of activated carbon fibers is adhered to the inner wall surface of the charger, and the generated corona product is adsorbed and decomposed to reduce the influence on the photoreceptor. In addition, the charge wire, grid, and shield case of the corona charger
g, AuNi, Ni ₂ O ₃ , MnO, or the like, and a method of absorbing and decomposing the generated corona product to reduce the influence on the photoreceptor. Activated carbon fiber, Ti, Fe, Sn, Mn,
Ag, Au, Ni, Ni ₂ O ₃ , MnO, and the like have a catalyst and a decomposing action on the corona product. Therefore, these are formed into a charge wire, a grid, a shield case, etc. of a corona charger, coated or coated. By plating, it is possible to suppress the influence of the corona product on the photoconductor.

In the method (1), a contact charging method which generates less ozone and nitrogen oxides is used instead of the corona charging method. This method is described in, for example, 1. Toshiharu Nakamura: "Contact charging method" Journal of the Electrophotographic Society of Japan Vol.30 No.3 (1991) 2. Shinji Tetsuya: “Electrification Technology Using Conductive Roller and Brush Electrification Method Contact Electrification Technology Without Corona Electrifier”, Journal of the Institute of Electronics Photography, Vol. 27, No. 4, (198)
8). Examples of the disclosure in the patent gazette include the following, for example. (1) JP-A-63-149668 A uniform charging is performed over the entire photosensitive member by applying a pulsating voltage having a peak-to-peak voltage that is twice or more the charging start voltage to a roll-shaped charging member. Contact charging method. (2) Japanese Patent Application Laid-Open No. 1-267667 By applying an AC voltage and a DC voltage controlled by a constant current to a roller-shaped or blade-shaped charging member, the photosensitive member is exposed to light even if the resistance or capacity of the charging member changes in the environment. A charging device capable of performing stable charging over the entire body.

(D) Method for Eliminating or Reducing the Effect of Image Flow-Causing Substances Adhered to the Photoreceptor Surface To cope with the reduction in resolution and the phenomenon of image deletion, contaminants adhered or fixed on the photoreceptor are dried. How to use it,
Several methods have been proposed, such as a method of improving the adhesion by cleaning. Examples of these disclosures include, for example, the following. (1) A method of heating the photosensitive member to prevent a decrease in surface resistance and suppress a decrease in resolution is disclosed in JP-A-63-40181, JP-A-62-296180, and JP-A-51-1981.
No. 65941, JP-A-60-95467 and the like.

(2) Japanese Patent Application Laid-Open No. 60-173570 discloses an image forming apparatus for wiping the surface of a photoreceptor to remove corona products adhering to the surface and preventing deterioration of resolution. (3) U.S. Pat. No. 5,264,903 and JP-A-3-92882 disclose a method of cleaning the photosensitive layer with a brush made of activated carbon fiber or nylon to remove corona products. (4) Japanese Patent Laid-Open No. 5-15069 discloses a method of cleaning the surface of a photoreceptor with a nonwoven fabric of ultrafine fibers to remove corona products.
No. 3, JP-A-5-134585, JP-A 8-
No. 248820. Among these,
The heating method has the greatest effect on image deletion, followed by water wiping, activated carbon fibers, and nonwoven fabric of ultrafine fibers. However, the effect differs depending on the type of the photoreceptor, the member used, the method of use, and the like.

[0019]

As described above, when a corona product, a toner component, paper dust, or the like adheres to a photoreceptor, in the photoreceptor layer, the electrical resistance decreases, the mechanical characteristics deteriorate, and the surface friction decreases. Phenomena such as an increase in the coefficient occur. For this reason, the resolution of the formed image is reduced, and when the image is further advanced, image deletion occurs. In addition, problems such as reduction in durability of the photoconductor due to promotion of wear of the photosensitive layer, promotion of wear due to increase in frictional resistance between the cleaning blade and the photoconductor, and blade squealing also occur. As shown in the above-mentioned disclosure example, the use of a needle-shaped electrode for the charging member, or the shield case, the grid or the like may be made of activated carbon fiber, it is possible to suppress the generation of corona products. .

However, even in the contact charging method which is said to generate the least amount of corona product, a considerable amount of corona product is generated. For example, although the amount is very small, such as 0.1 ppm or less for ozone and 0.01 ppm or less for nitrogen oxides, even a small amount hardly scatters, so that the corona product generated is almost 100% photosensitive. Acts on the body. In addition, since the corona products accumulate without being removed as the photoreceptor is less abraded, the surface resistance of the photoreceptor is more likely to decrease, and the problem becomes greater depending on the operating time of the charging device. Therefore, it is necessary to prevent corona products, paper powder, toner components, and the like from remaining on the photoconductor, or to take measures before the surface layer of the photoconductor increases the friction coefficient or fog even if it adheres. Desirably, in the above disclosed examples, it is possible to suppress the influence of ozone and nitrogen oxides, but it is almost impossible to eliminate the influence.

In order to maintain high image quality and further increase the durability of the photoreceptor, at least the friction coefficient of the photoreceptor is reduced, and the corona product, which is a factor of increasing the friction coefficient,
It is necessary to sufficiently remove binders, toner components, and the like contained in paper powder. The easiest way to avoid image bleeding due to corona products is to heat the photoreceptor to 45-60 ° C, as seen in the aforementioned disclosure. However, in the case of this method, a new heating means is required, and electric power for the heating source is also required. In addition, there is a problem that the temperature is restricted depending on the photoconductor material or the toner, and it is difficult to install the photoconductor having a small diameter in terms of space. In addition, in this case, since the corona product is not removed, there is a high possibility that the problem will recur due to moisture in the atmosphere when the heating temperature is lowered.

The image deletion can also be improved by wiping an organic photoreceptor or a photoreceptor having a coating layer in which inorganic fine particles are dispersed with water. However, in the case of an a-Si photoreceptor on which an oxide film is easily formed, or a photoreceptor coated with an amorphous carbon (DLC = Diamond-LikeCarbon) film on which a corona product is easily adsorbed, the photoreceptor must be completely recovered. It is difficult. In addition, the water wiping method always requires replenishment of water and replacement of members, which is not an effective method from the viewpoint of handling properties. Activated Carbon Fiber (ACF)
Fiber) as a cleaning material, contaminants such as corona products can be efficiently removed when a member of a suitable form is used in an appropriate manner, but when strongly pressed, activated carbon fiber Easily breaks into a powdery form, so that the damaged powder enters the cleaning member and the developing section, and the surface of the photoreceptor has a resin layer in which inorganic fine particles are dispersed or D.
Even a thin film having high hardness such as an LC film may damage the film or cause an abnormal image phenomenon. Therefore, depending on the application method, the life of the photoconductor may be shortened.

When the non-woven fabric of ultrafine fibers is used as a surface property adjusting member for restoring the surface property by removing contaminants adhering to the surface layer of the photoreceptor, the non-woven fabric is removed as seen in the above-mentioned disclosed examples. Since the contaminants on the photoreceptor are taken into the nonwoven fabric and there is little risk of recontamination, a method using a nonwoven fabric of ultrafine fibers is effective. However, if a photoreceptor to which contaminants easily adhere is used, it is difficult to sufficiently perform the removal function. Therefore, the photoreceptor is always in contact with the photoreceptor so that the contaminants are removed in each copy cycle. It is desirable. In this case, however, the removal ability is enhanced by rubbing strongly, but the organic photoreceptor is soft, so local abrasion is likely to occur, which may cause image defects or reduced durability. However, in the case of an ordinary organic photoreceptor, even if the corona product is removed, the coefficient of friction does not decrease so much, so that it cannot be used as a means for suppressing abrasion and does not contribute much to the high durability of the photoreceptor.

If the DLC film is coated on the photoreceptor, the photoreceptor can be made highly durable. However, since the contaminant has a high fixing power, the contaminant can be easily removed only by using a nonwoven fabric of ultrafine fibers. This is difficult, and in order to obtain long-term stability, it is necessary to use it in combination with other means (for example, heat treatment of the photoconductor). As described above, when corona products such as ozone and nitrogen oxides generated as by-products upon charging act on the photoreceptor, they absorb moisture in the atmosphere and reduce the surface resistance of the photoreceptor in a relatively short time, This causes image deletion.
Also, when the corona product seeps into the photosensitive layer,
Since the bulk resistance is reduced, the structural defects are increased, or the intermolecular bond is broken, it causes image deletion and sensitivity reduction.

Further, when the corona product adheres to the surface of the photoreceptor, a phenomenon occurs in which the friction coefficient with the cleaning blade is increased in order to increase the friction coefficient, and the abrasion of the photosensitive layer is accelerated. In particular, in the case of an organic photoreceptor that has been used as a mainstream recently, the mechanical strength is originally low, and it is susceptible to corona products. On the other hand, by forming a resin layer in which fine particles (high hardness) are dispersed on the surface of the photosensitive layer, the abrasion resistance can be improved and the life of the photosensitive member can be extended. Generally, the fine particles are 10 to 50% of the resin.
When such a photoreceptor is used in a contact charging system, if the amount of the inorganic fine particles is small, fine powder such as SiO ₂ or TiO ₂ added as a flow control agent in the toner may be added. In some cases, the layer may bite into the surface of the layer, resulting in non-uniformity due to film abrasion, white spots, bleeding, and the like.

When the surface of the photoreceptor is hardly abraded, the corona product tends to remain on the surface of the photoreceptor, so that the resolution gradually decreases. There is a problem that the image flow occurs.
Further, there is a problem that the light transmittance is reduced, the image potential level is increased, and the image density is reduced. Further, in the contact charging method, the charging member is always in contact with the photoreceptor even when the charging member is not in operation, so that fine powder such as toner easily adheres to the charging member and is in a state of being easily stained. Therefore, not only the life of the charging member itself is shortened, but also the attached toner powder or the like becomes a wear accelerator, and the life of the photoconductor may be shortened. Therefore, it is desirable to perform charging in a non-contact manner. That is, it is desirable to eliminate the influence of corona products, paper powder, toner components, and the like during charging, and to keep the photoconductor surface layer in a clean state at all times.

The present invention has been made in view of the above-described problems in the conventional image forming apparatus, and has been made to reduce the resolution, image deletion, and image quality such as uneven images even in a high humidity environment. It is another object of the present invention to provide an image forming apparatus that prevents the occurrence of ozone and nitrogen oxides and prevents environmental pollution.

[0028]

According to the present invention, there is provided an image forming apparatus for forming an image by an electrophotographic method, in order to achieve the above object, a photoreceptor having a coating layer in which inorganic fine particles are dispersed, and a catalyst having a catalytic action. And a charging member mainly composed of a conductive material and a surface property adjusting member for cleaning the surface of the photoreceptor. Here, the material having the above-mentioned catalytic action and having conductivity is preferably activated carbon fiber. The surface property adjusting member has a structure in which at least a region in surface contact with the photoreceptor has a structure in which an elastic member is included in a non-woven fabric of a microfiber alone or the non-woven fabric of the microfiber, and acts on the photoreceptor constantly or intermittently. The charging member, which is preferably a member for cleaning the surface of the photoreceptor, is provided at least in a non-contact state with the image forming area of the photoreceptor. It is good to make it a member which charges electric charge.

Further, it is preferable that the charging member is a member for charging the photoreceptor with a charge required for image formation by applying a DC voltage on which an alternating voltage is superimposed.
The inorganic fine particles dispersed in the coating layer of the photoreceptor may be fine particles of any of alumina and titanium oxide, or a mixture of alumina and titanium oxide. Here, the dispersion amount of the inorganic fine particles is preferably set to 10 to 35% with respect to the low molecular charge transporting material for improving the mobility of the binder resin and the holes of the photoconductor. The thickness of the coating layer is preferably 1 μm or more and 8 μm or less. Alternatively, the inorganic fine particles dispersed in the coating layer of the photoreceptor are alumina or titanium oxide, the charging member is mainly composed of activated carbon fibers, and the surface property adjusting member is mainly composed of a nonwoven fabric of ultrafine fibers. And
It is preferable that the surface friction coefficient of the photoconductor is 0.1 or more and 0.5 or less when an image is formed by causing the charging member and the surface property adjusting member to act on the photoconductor.

[0030]

As described above, in order to achieve the object of the present invention, 1) a photoreceptor having a coating layer in which specific inorganic fine particles are added in a suitable range on an organic photoreceptor, 2) ozone or nitrogen A charging member configured to have a function of eliminating corona products such as oxides from acting on the photoreceptor at the time of charging, or excluding them from changing the characteristics; 3) adhering to the photoreceptor surface It is preferable that a surface property adjusting member for reducing the coefficient of friction and maintaining a good level by removing the contaminants and restoring the surface property is disposed in the image forming apparatus and operated.

When a coating layer containing inorganic fine particles is formed on the photosensitive layer of the photosensitive member, the wear resistance of the photosensitive member is improved,
Life can be extended. In addition, if a coating layer containing inorganic fine particles is formed on the outermost layer of the photoconductor, the nonwoven fabric of microfibers is used, so that a large amount of force is not required and only the wiping is performed on the photoconductor layer (coating layer) of the photoconductor. It is possible to easily remove contaminants adhering to the device.
The reason for eliminating corona products such as ozone and nitrogen oxides generated during charging is that the adhesion of the corona products absorbs moisture in the atmosphere and lowers the surface resistance of the photoreceptor, resulting in a uniform image. This is to prevent the deterioration of the characteristics and resolution from occurring.

In order to charge the photoreceptor, the charging member needs to be conductive or semiconductive. Further, in order to prevent corona products from being generated at the time of electric discharge or to keep the amount of generation so as not to affect the photoreceptor, it is desirable to constitute the material having a function of detoxifying at the same time as the generation. . As this material, a material having a catalytic function is preferable. Therefore, by forming the charging member as a material having conductivity and a catalytic function, for example, from activated carbon fiber, charging and removal of corona products can be achieved at the same time. Here, by performing non-contact charging in which the charging member is not brought into contact with the photoreceptor, contamination of the charging member by toner or the like is reduced as much as possible, wear of the charging member is avoided as much as possible, and the catalyst constituting the charging member is removed. A decrease in function can be suppressed, and durability can be increased.

Incidentally, the cleaning blade and the developer are greatly involved in the abrasion of the photosensitive layer of the photosensitive member. In particular, since the frictional resistance between the cleaning blade and the photoconductor is extremely large, the photoconductive layer is easily worn,
This contributes to the short durability of the photoconductor. The most effective means for extending the durability of the photoreceptor is to lower the friction coefficient of the surface without damaging the photosensitive layer and to reduce the frictional resistance between the photosensitive layer and the cleaning blade. In this way, the durability of the photoconductor can be increased,
In addition, it is possible to suppress a decrease in image quality.

The reduction of the friction coefficient can be achieved by wiping the surface layer of the photoreceptor constantly or intermittently with a surface-adjusting member mainly composed of a nonwoven fabric of ultrafine fibers. However, this effect is sufficiently exhibited when a photoreceptor having a coating layer (resin layer) in which inorganic fine particles are dispersed is provided on the photosensitive layer. Here, the surface property adjusting member is a member for recovering (decreasing) the friction coefficient of the photoconductor surface by removing the corona product, paper powder, toner component, and the like attached to the photoconductor surface by rubbing. . This member is opposed to the photoreceptor, and the surface of the photoreceptor is wiped while being brought into surface contact (usually, a width of 3 to 10 mm is sufficient), so that paper powder, toner components, and corona products adhering to the photoreceptor surface are removed. Etc. can be removed. Therefore, the surface of the photoconductor is always kept in a clean state, and it is possible to prevent the photoconductor from being contaminated by paper dust, toner components, corona products, and the like, thereby suppressing an increase in the coefficient of friction. be able to. Further, since the friction coefficient can be suppressed to a low level, the wear of the photosensitive layer is reduced, and the durability of the photosensitive member can be increased.

[0035]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. First, a copying (image forming) process in a copying machine according to an embodiment of the image forming apparatus of the present invention will be described with reference to FIGS. FIG. 1 is a schematic sectional view showing a configuration of an image forming unit in the copying machine. FIG. 2 is a partial cross-sectional view illustrating a configuration near a surface layer of a photoconductor provided in the image forming unit.
FIG. 3 is a partial cross-sectional view showing another configuration example.

In this copying machine, an image of a document is read by a CCD (Charge Coupled Device) and converted into digital image data.
(780 nm) to form a latent image by scanning over the charged photoreceptor, and form the latent image with toner (developer).
This is a digital image forming apparatus that forms an image in an electrophotographic system by visualizing the image. However, since the feature of the present invention is the configuration of the image forming unit, description other than this point will be omitted below.

The image forming section of the copying machine includes a photosensitive member 11,
The image forming apparatus includes a charging device 12, an image exposure device 14, a developing device 15, a transfer device 16, a separating device 17, a fixing device 18, a cleaning device 19, a surface property adjusting device 20, a static elimination device 22, and a paper feeding device 23. The photoconductor 11 is a member that is charged by the charging device 12 and is scanned by the image exposure device 14 to form an electrostatic latent image. As the photoconductor 11, a selenium-based, silicon-based, or organic-based photoconductor can be used. In the present invention, an organic photoconductor (OPC) is used. However, other photoconductors may be used. A photoconductor in which a coating layer containing inorganic fine particles is formed on the surface layer of the photoconductor 11 is effective for improving durability and maintaining image quality.

The structure of the photoreceptor 11 is as shown in FIG.
The undercoat layer 11b, the charge generation layer 11c, the charge transport layer 11d, and the coating layer 11e are sequentially stacked on the conductive support 11a. The charge generation layer 11c and the charge transport layer 11d
Thus, the photosensitive layer 11f is formed. Charge generation layer 11c
This structure, in which the charge transport layer 11d is provided separately, is called a function-separated type photoreceptor, and is a hole transfer type in which minus is usually used as a charging potential. In addition, as shown in FIG. 3, a photoconductor 11 having a configuration in which a charge generation layer 11c and a charge transport layer 11d are integrated into a photosensitive layer 11g can also be used. In the case of the photoconductor 11 having such a configuration, plus is used as the charging potential. In either case, a coating layer 11e is formed on the outermost surface of the photoconductor.

The coating layer 11e contains inorganic fine particles (metal oxide fine particles) in an amount of 10 to 40%, preferably 15 to 35%.
% To 1 to 8 which are transparent from visible light to infrared light.
It is a thin film of about μm. Unless otherwise noted, the following description is based on the configuration shown in FIG. The reason why the coating layer 11e in which inorganic fine particles are further dispersed is laminated on the photosensitive layer 11f is to improve the durability of the photoreceptor, and when a contaminant such as a corona product adheres, a specific member, for example, a very fine material. This is because it is easy to remove with a fiber non-woven fabric. In particular, since the coefficient of friction can be maintained at a low level by facilitating removal of contaminants, wear of the photoconductor 11 can be suppressed, and deterioration of image quality can be minimized even in a high-humidity environment. It becomes possible to do.

The photosensitive member 11 is charged to about -400 to -1000 V by a charging member 13 provided in a charging device 12. A material having a catalytic function is used for the charging member 13 provided in the charging device 12, and the charging member 13 is installed in a non-contact state with at least the image forming area of the photoconductor 11. The body 11 is charged. By configuring the charging member 13 mainly with a member that suppresses the generation of the corona product, the influence of the corona product on the photoconductor 11 can be suppressed. A characteristic of the charging member 13 is that activated carbon fibers having a catalytic action and conductivity are used. By using such a material for the charging member 13, it is not necessary to separately add a conductive member, and the corona product generated at the time of charging is immediately absorbed before affecting the photoreceptor 11, and only the charge is removed. Since the corona product moves to the photoconductor 11, the corona product does not affect the photoconductor 11. Although the charging device 12 is illustrated as having a roll-shaped charging member 13, a plate-shaped or block-shaped or brush-shaped charging device may be used.

The image exposure device 14 is a device for forming a latent image of an image to be formed on the photoreceptor 11, and is provided with a polygon mirror, The photosensitive member 11 is scanned using a cylindrical mirror and a lens to form an electrostatic latent image. The developing device 15 is a device for visualizing a latent image formed on the photoreceptor 11, and there are a one-component system and a two-component system for toner, and any of them can be used in the present invention. The transfer device 16 is constituted by rollers,
This is a device for transferring a visible image by toner to recording paper fed from the printer. The separating device 17 is provided with a separating claw and separates the transfer paper on which the visualized image is transferred from the photoconductor 11. The fixing device 18 is a device for fixing the image by toner by heating and pressing the transfer paper.

The cleaning device 19 is provided with a cleaning blade 19a, and removes residual toner on the photosensitive member 11 after transfer by a cleaning blade method. As a method for cleaning the residual toner on the photoconductor 11, there are a fur brush method, a cleaning blade method, a magnet brush method, a method combining a fur brush and a cleaning blade method, and these methods may be used. The surface property adjusting device 20 includes a surface property adjusting member 21, and removes toner components and paper dust attached to the surface of the photoconductor 11 by the surface property adjusting member 21.
It is a device for cleaning. In this copier,
In order to remove contaminants by cleaning the surface of the photoconductor 11 and to suppress an increase in the friction coefficient of the surface of the photoconductor 11 and maintain a low friction coefficient,
Is provided. In the surface property adjusting device 20, the surface property adjusting member 21 is disposed so as to face the photoconductor, and the cleaning operation is performed by constantly or intermittently making surface contact. The static eliminator 22 is a device that neutralizes the residual latent image on the photoconductor 11.
Here, a lubricant applying device may be provided after the cleaning device 19 in order to further reduce the friction coefficient of the surface of the photoconductor 11.

In such an image forming section, the photoconductor 11 is charged by the charging device 12, an electrostatic latent image is formed on the photoconductor 11 by the image exposure device 14, and this is visualized by the developing device 15, The image is transferred to the recording paper by the transfer device 16, the recording paper is separated by the separation device 17, and the cleaning device 19 is separated.
After cleaning the toner remaining on the surface of the photoreceptor 11 with the above, and further cleaning the surface of the photoreceptor 11 with the surface property adjusting device 20,
By removing the residual latent image by the charge removing device 22,
A series of image forming processes is completed. The separation device 1
The recording paper separated in 7 is discharged to a paper discharge section after an image is fixed by the fixing device 18.

The charge transport layer 11d of the photoreceptor 11
As a material of the, a polycarbonate-based resin is mainly used. On the other hand, a polyurethane rubber blade is mainly used as the cleaning blade 19a provided in the cleaning device 19 from the viewpoint of durability. In the case of such a combination, if the coating layer 11e is not provided, the frictional resistance when the blade comes into contact with the photoconductor 11 becomes extremely large, and the hardness of the photosensitive layer 11f is low.
1f is easily worn. Even if the coating layer 11e is provided, a high-frequency noise is generated due to its high surface friction coefficient, the photosensitive member 11 is scratched, and in a severe case, a large load is applied to the drive system, and the gears and In some cases, mechanical damage occurs to belts and the like. Therefore, in order to avoid this phenomenon, a powdery lubricant may be applied to the tip of the photoconductor and the cleaning blade 19a to reduce the frictional resistance between the photoconductor 11 and the cleaning blade 19a. However, even in this case, depending on the type of the photoconductor 11 or the toner, a scratch or a high-frequency sound may be generated during use.

On the other hand, a method for applying a charge to the photoreceptor 11
In addition to the non-contact charging method described with reference to FIG.
Generally, a contact charging method and a corona charging method are employed. Photoconductor 1
Contact charging method for charging by bringing the charging member 13 into contact with the charging member 13
And between the photosensitive member 11 and the charging member 13 by 100 μm
In the non-contact charging method in which charging is performed by providing a subsequent space, 10 ²
-10¹²Brushes and rolls with a resistance of about Ωcm
DC voltage of about 1000 V to 2000 V
Or alternating voltage of 1 to 3 KV / 1 to 2 KHz
Charging is performed by applying a DC voltage. On the other hand, corona charging
According to the law, 40-80 μm suspended in a shield case
40 for metal wire such as nickel plated wire and tungsten wire
Charges the photoconductor 11 by applying a voltage of 00V to 8000V
I do.

As a phenomenon common to both of them, both are accompanied by a discharge phenomenon.
Corona products such as ozone (O ₃ ) and nitrogen oxide (NO _x ) that deteriorate the characteristics of the photoconductor 11 are generated. A comparison of the amount of corona product generated between the corona charging method and the contact charging method and the non-contact charging method shows that the amount of the latter is smaller due to the lower applied voltage, and the amount of ozone generated is Of 1
/ 100 to 1/200, the amount of generated nitrogen oxides is 1 /
It is about 50 to 1/100. As described above, it is advantageous to use the contact charging method and the non-contact charging method with respect to the amount of the corona product, but as described above, the corona product is also generated in these methods, Since it is produced very close to 11, the corona product produced immediately affects the photoreceptor.

Among these corona products, nitrogen oxides absorb moisture in the atmosphere to become nitric acid. Since the function of the antioxidant hardly works for nitric acid, the nitric acid lowers the resistance of the surface layer and the bulk layer of the photoreceptor 11, and lowers image quality such as image deletion. Ozone is also specified as an environmentally dangerous gas, and its chemical properties include bleaching action and strong oxidizing action. 11 lowers the transport capacity and the photosensitive function. Therefore, the photosensitive layer 11f may have 2,6-di-t-butyl-
Monophenol compounds such as p-cresol and butylated hydroxyanisole; 2,2'-methylene-bis- (4
-Ethyl-6-t-butylphenol) and 1,3,5-trimethyl-2,4,6-
An antioxidant or an antioxidant such as tris- (3,5-di-t-butyl-4-hydroxybenzyl) benzene or a high molecular weight phenolic compound such as hydroquinone or an organic phosphorus compound or a plasticizer is added in a weight ratio. May be added in an amount of 1 to 20%.

By this treatment, the permeation of ozone into the photoreceptor 11 can be suppressed. However, since the surface layer of the photoreceptor 11 is constantly exposed to ozone, if the function of the antioxidant decreases or disappears, The surface resistance is reduced, and the moisture in the air is easily adsorbed, which leads to a reduction in image quality. Further, the corona product increases the friction coefficient by adhering to the surface layer of the photoreceptor 11, so that the frictional resistance increases, causing local transfer failure of the image, a decrease in cleaning performance, generation of high-frequency noise, and the like. When it becomes severe, the blade may be involved and the photoconductor 11 may be locked, and the wear of the photoconductor 11 is promoted.

Therefore, in order to maintain a high-quality image for a long period of time, it is important to eliminate the influence from the charging device 12 as much as possible. Factors that increase the coefficient of friction include, in addition to the above-described photoreceptor material and corona product, a developer, a constituent material of a toner (such as a coating agent such as a charge control agent), a binder contained in paper, Since there are shavings on the photoconductor 11 and gas components emitted from the fixing device, the surface of the photoconductor 11 is cleaned not only by removing the corona products but also by removing the corona products. It can be said that this is desirable for improving durability and maintaining image quality.

The following two methods are available to eliminate the influence of the corona product generated by the charging device 12 during charging.
There are two ways. The corona product attached to the surface layer of the photoconductor 11 is promptly removed. The corona product generated by the charging device 12 is removed before adhering to the photoconductor 11 or is not generated.

In the method (1), it is desirable to remove only contaminants such as corona products from the viewpoint of durability (maintaining film thickness) of the photoconductor 11, but in reality, the photoconductor 11 has irregularities. It is difficult to uniformly remove only the deposits.
In the image forming apparatus, since the cleaning blade of the cleaning device 19 and the developing device 15 are constantly rubbing the photoconductor 11 during operation, contaminants such as corona products adhered to the photoconductor 11 are constantly shaved. Although the influence on the photoconductor 11 is suppressed, if the contaminant is completely removed by only this method, there is a problem that the photoreceptor 11 is scraped more and the life is shortened.

The method of charging the photoreceptor 11 without generating a corona product is not limited to the triboelectric charging method or the induction charging method, but it is actually quite difficult. There is no practicality. In addition, as a method of suppressing corona generation by a charging method capable of stably charging at present, there is a method of arranging a catalyst or a member having a decomposing action around the charging device 12, but in this method, scattering of corona products is almost impossible. The effectiveness is extremely low for no charging method.

On the other hand, as in the present invention, ozone
Catalyst with excellent absorption and decomposition functions for nitrogen and nitrogen oxides
If the charging member 13 itself is made of a material having a function,
High effectiveness can be obtained. Ozone and nitrogen oxides
Catalysts that adsorb or decompose include:
Materials are known. For ozone, for example, silica gel
, Activated zirconia, zeolite, activated alumina, active
Charcoal, activated carbon fiber, Ti-Ni-Zr-based oxide, diacid
Titanium-calcium aluminate-manganese oxide system, Cu-
Mn type, alumina-silica gel type, terpenoid, etc.
You. Regarding nitrogen oxides, for example, activated carbon, activated carbon fiber
Fiber, titanium dioxide-lime aluminate-manganese oxide
System, slaked lime-activated carbon-calcium carbonate system, Pt-Al ₂
O₃There are systems.

One or more of the above-mentioned materials are added to a rubber such as an acrylic resin, a nitrile, or a polyurethane, and carbon or a metal oxide is added as necessary to impart conductivity. Charging member 13 of charging device 12
It can be used as However, most materials other than the activated carbon fibers shown above lose their function as a catalyst by making them into fine powder. Furthermore, when it is used as the charging member 13 by adding it to a resin or rubber material, the photoconductor 11 may be damaged depending on the use condition. Activated carbon fiber, on the other hand, is harmless,
It has an effective removal function for both nitrogen oxides, is itself conductive, can be used alone, and can be processed if necessary.
It is the most preferred member for the present invention.

Next, each member and device of the image forming section of the copying machine will be described in detail. First, the photoconductor 11 will be described. This copying machine uses an organic photoconductor as the photoconductor 11. This is because the organic photoreceptor can be designed with high sensitivity, can be manufactured at low cost, is easy to manufacture, and has no pollution compared to other photosensitive materials such as selenium and amorphous silicon. However, the durability of the organic photoreceptor is short as described above. In order to increase the durability, a method of forming a coating layer of high hardness and high transmissivity having high durability and satisfying the electrical characteristics on the photoreceptor is generally performed. Coating layer 11 in which inorganic fine particles are dispersed
e is formed on the surface of the organic photoreceptor.

Polyester resin, polyurethane resin, polycarbonate resin and the like, which are known as the material of the coating layer 11e, have high electric resistance, extremely low charge injecting property, and extremely low hole mobility. Is rarely used. In this copying machine, a coating layer 11e is formed as an extension of the photosensitive layer 11f. The coating layer 11e is formed by adding 10 to 35% of alumina (Al ₂ O ₃ ) or / and titanium oxide (Ti) in a polycarbonate resin binder resin constituting the photosensitive layer 11f.
O ₂ ) or other inorganic fine particles are dispersed and formed together with the donor,
The mechanical strength and electrical characteristics are improved or maintained.

Each layer constituting the photoreceptor 11 will be described in detail below. First, regarding the conductive support 11a,
As a material, aluminum which has been subjected to processing such as super finishing and mirror finishing is generally used.
Any material that does not cause deformation at a temperature of about ℃ can be used. In addition to metals such as stainless steel, copper, and brass, compressed paper, resin, or glass, conductive layers formed by vapor deposition or sputtering of gold, aluminum, platinum, chrome, etc. Further, a conductive layer in which fine particles such as carbon and tin are dispersed may be applied. Electrical resistance is 10 ⁶ Ω in volume resistivity
-There is no problem if the value is not more than cm. The shape is a drum shape, and the thickness depends on the diameter and the material. In the case of an aluminum tube, a thickness of about 0.5 to 3 mm is usually used.

The undercoat layer 11b maintains the charging characteristics by preventing charge injection from the conductive support 11a, prevents the latent image from being disturbed by irregular reflection of the scanning beam from the image exposure device 14 in the photosensitive layer, In addition, it is formed in order to improve the coating properties and adhesion of both the conductive support 11a and the charge generation layer 11c. The undercoat layer 11b is made of alumina (A
l ₂ O ₃ ) In addition to a vapor-deposited film, a metal oxide such as TiO ₂ or SnO ₂ may be mixed with an alkyd resin, an alkyd-melamine resin,
It is formed by dispersing in polyvinyl alcohol, casein, or the like, and coating the conductive support 11a to a thickness of 1 to 10 μm using a dipping method, a spray method, a ring coating method, or the like.
If the undercoat layer 11b is too thick, the residual potential is likely to increase repeatedly. If the undercoat layer 11b is too thin, the S / N ratio deteriorates and noise increases when used for a long time. Therefore, the undercoat layer 1 having a volume resistance of usually about 10 ⁹ to 10 ¹² Ω · cm is used.
By forming 1b uniformly with a film thickness of 3 to 8 μm, good electrophotographic characteristics can be maintained. In addition, the undercoat layer 11b
May be a semiconductor film that blocks holes and allows electrons to pass therethrough.

The charge generation layer 11c is obtained by dispersing a charge generation material in a binder resin. In the case of an organic photoreceptor, as the charge generating material, metal phthalocyanine, phthalocyanine based metal-free phthalocyanine, carbazole, triphenylamine, fluorenone, azo pigment having a skeleton such as oxadiazole, perylene-based pigment, anthranthrone, etc. Quinone pigments, perylene pigments, benzoquinone and naphthoquinone pigments, polycyclic quinone pigments, quinone imine pigments, and the like can be used alone or as a mixture of two or more. Moreover, you may add a low molecular transport material as needed. As the binder resin, polyamide resin, polyester resin, polycarbonate resin, polyurethane resin,
Acrylic resin, polyacrylamide resin, phenol resin and the like can be used.

As the hole transport substance, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, thiazole derivatives, triazole derivatives, styryl anthracene, styryl pyrazoline and the like are used alone or in combination.
Used as a mixture of more than one species. These charge generating materials and the binder resin are dispersed uniformly in a ball mill, a sand mill, a vibration mill, or the like using tetrahydrofuran, toluene, cyclohexanone, dichloroethane, or the like as a dispersion, and the undercoat layer is formed using a spray coating method, a dipping method, or the like. 0.05 above
-5 μm, preferably 0.2-1 μm. If the thickness is more than necessary, the space charge increases, which affects the light attenuation characteristics, the residual potential, and the like.

The charge transport layer 11d is obtained by dispersing a charge transport material in a binder resin. As a charge transport material,
Low molecular oxazole derivatives and oxadiazole derivatives (JP-A-52-139065, JP-A-52-1)
No. 39066), imidazole derivatives, triphenylamine derivatives, α-phenylstilbene derivatives (JP-A-58-198425, JP-B-2-248).
No. 64), toniphenylmethane derivatives (described in JP-B-51-10983), anthracene derivatives (described in JP-A-51-94829) and the like can be used. As the binder resin, polycarbonate resin (bisphenol A type, bisphenol C type, bisphenol Z type or a copolymer thereof), polyarylate resin, polyester resin, polystyrene resin, vinyl acetate resin or the like alone or
A mixture of more than one species can be used.

In the present invention, an antioxidant may be added in order to improve environmental resistance and to suppress a decrease in sensitivity and a rise in residual potential. As the antioxidant, for example, 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t
Monophenolic compounds such as -butyl-4-ethylphenol and 2,2'-methylene-bis- (4-methyl-
Bisphenol compounds such as 6-t-butylphenol) and 2,2'-methylene-bis- (4-ethyl-6-t-butylphenol); 1,1,3-tris- (2-
Methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris-
(3,5-di-t-butyl-4-hydroxybenzyl)
Benzene, tetrakis- [methylene-3- (3 ', 5'
-Di-t-butyl-4'-hydroxyphenyl) propionate] phenolic compounds such as methane;
Hydroquinones such as 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, and 2- (2-octadecenyl) -5-methylhydroquinone can be used.

The resolution of the formed image is as follows.
The resolution of the electrostatic latent image is set as high as possible because it is also affected by the carrier particle size, the developing method, the dot diameter of the original image, the transfer conditions, the surface resistance of the charge transport layer 11d, the bulk resistance, and the like. It is desirable to keep. But,
Light and charges tend to diffuse as the photosensitive layer 11f becomes thicker, and the resolution of the electrostatic latent image on the photoconductor 11 tends to gradually decrease as the film thickness increases. Therefore, the thinner the thickness of the charge transport layer 11d, the more advantageous in terms of resolution. However, since the photosensitive layer 11f is a dispersion layer, if it is too thin, non-uniformity of electric resistance becomes conspicuous, and the S / N ratio and electric durability decrease in the long term, and the mechanical durability limit has been awaited. This causes a problem such as a sudden down.
Furthermore, if the charge transport layer 11d is made thin, the contrast potential required for image formation cannot be obtained, resulting in an image having low contrast and gradation. Therefore, the charge transport layer 1
If the film thickness of 1d is set to a uniform value of about 5 to 25 μm,
A high-resolution electrostatic latent image of 600 to 2400 dpi can be formed, and both contrast and resolution can be achieved.

The coating layer 11e is formed on the photosensitive layer 11f in order to improve the mechanical and electrical durability of the photosensitive member, and includes a high-hardness amorphous carbon film and an amorphous silicon film. A thin film such as a high-resistance tin oxide film having a thickness of about 1 to 10 μm by a vacuum deposition method, a plasma CVD method, a sputtering method, an ion plating method or the like, and a particle size of 0.05 to 5 μm. There is a method in which fine particles of a certain degree are dispersed in a binder resin and a thin film is coated on the photosensitive layer 11f. In this copying machine, the durability of the photoconductor 11 is improved by dispersing an appropriate amount of inorganic fine particles in a binder resin. However, even with the same amount of dispersion, the abrasion performance varies depending on the dispersion state, particle size, and the like of the fine particles. As the inorganic fine particles, titanium oxide, silica, alumina, zirconium oxide, indium oxide, silicon nitride, and the like can be used. Among them, particularly, titanium oxide and alumina have good environmental stability and are suitable as the inorganic fine particles used in the present invention.

These inorganic fine particles can be used alone or as a mixture of two kinds. Further, it is also possible to perform a water-repellent treatment using a silane coupling material, a fluorine-based silane coupling agent or the like. These inorganic fine particles can be used by dispersing them in a polycarbonate resin, a polyethylene resin, a polyurethane resin, an acrylic resin, a polyamide resin or the like as a binder resin. As the binder resin, a high-resistivity polycarbonate resin having a transparency of about 10 ¹⁶ to 10 ¹⁷ Ω · cm, which has no polarity dependence and good transparency, is preferable. When dispersing inorganic fine particles in a binder resin, it is possible to improve water repellency, lubricity, and improve environmental characteristics and wear resistance by dispersing an appropriate amount of fluororesin fine particles such as polytetrafluoroethylene. It is.

The amount of the inorganic fine particles to be dispersed depends on the kind of the material to be added.
Add 50%. In consideration of the residual potential, maintenance of light sensitivity, image quality, and the like, it is preferable to add 10% or more and 40% or less, and a more preferable range is 15 to 35%. Abrasion resistance increases as the amount of addition increases, but on the other hand, light transmittance decreases or diffuses, charge mobility decreases, etc., resulting in lower resolution, higher residual potential, lower sensitivity, etc. More likely to occur. When the addition amount of the inorganic fine particles is small, the friction coefficient of the surface layer of the photoconductor 11 increases, so that mechanical deterioration is likely to occur. For this reason, toner filming by the developer, adhesion of silica or the like (piercing) is apt to occur, and white spots and unevenness may occur. On the other hand, the thickness of the coating layer 11e to be formed is usually 1 μm
It is set to at least 8 μm. As the coating layer 11e is made thinner, the image quality is improved, but the durability is lowered. on the other hand,
As the thickness increases, the durability increases, but the image quality such as resolution decreases. Therefore, it is more preferable to set the thickness to 2 to 6 μm.

The inorganic fine particles are dispersed in the coating layer 11e.
It affects the residual potential, mechanical durability, etc. Therefore, it is desirable that the inorganic fine particles in the coating layer 11e be substantially uniformly dispersed in the layer. It is preferable that the total thickness of the photosensitive layer 11f and the coating layer 11e is set within a range of 10 to 30 μm. When the film thickness is large, the charge tends to spread when the charge moves toward the surface layer in the photosensitive layer 11f, or the light is diffused at the time of exposure, so that the resolution is easily lowered. If the thickness is too small, the photosensitive layer becomes apt to cause unevenness and discharge breakdown.

Next, the charging device 12, particularly the charging member 13 provided therein, will be described. The charging member 13 provided in the charging device 12 is made of activated carbon fiber as described above. The main activated carbon fibers used here are:
Polyacrylonitrile (PAN) fiber [(C ₃ N
H ₃ ) _n ] and cellulosic fibers [(C ₆ H
₁₀ O ₅ ) _n ], phenolic resin fiber [(C ₆₃ H
₅₅ O ₁₁ ) _n ], pitch-based fiber [(C ₁₂₄ H ₈₀ N)
O) _n ].

When producing these activated carbon fibers,
Using ultra-fine fibers having a diameter of 5 to 15 μm as raw materials,
Flame resistance is applied at a temperature of about 00 to 500 ° C. In this state, there is almost no adsorption performance, and it is a mere carbon fiber. When the carbonized fiber is further heated (activated) to 600 to 1000 ° C. in an activation gas atmosphere such as carbon dioxide gas,
Fine pores (micropores) with a diameter of about 10 to 40 mm in the fiber wall
Is formed. Because these micropores have a close relationship with the adsorption function and have a pore size suitable for the size of the molecules to be adsorbed,
It has better adsorption characteristics than an adsorbent with many macropores such as activated carbon. Therefore, the pore diameter of the fiber is 100 mm.
If the molecular weight is larger than the above range, the molecular diameter of nitrogen oxide, which is a corona product, is too large, so that the adsorption performance is reduced. Most of the components of the activated carbon fiber having this adsorption function are carbon (approximately 90% or more), others are slightly hydrogen and / or nitrogen, and the rest is ash. It is most preferable to use the activated carbon fiber alone for the charging member 13 in order to maximize the effect.

By the way, activated carbon fiber is used for wastewater, drinking water,
In addition to environmental materials such as purification of exhaust gas and smoke from cigarettes, deodorization of refrigerators, etc., they are also recently used for ozone treatment of copiers. The removal function by the activated carbon fiber is exerted when molecules of the chemical substance enter and are adsorbed or decomposed (adsorption and decomposition functions) into ultrafine pores formed on the wall surface of the activated carbon fiber. Activated carbon fiber is NO
x, SOx, ozone, toluene gas, mercaptan, chlorine, ammonia, hydrogen sulfide, methyl sulfide, etc. can be effectively adsorbed. Is even better. As described above, typical activated carbon fibers are those starting from 4 to 5 types of fibers such as cellulose and phenol, and among them, formed from polyacrylonitrile (PAN) fibers. The activated carbon fiber contains about 2 to 5% of nitrogen atoms.

The nitrogen-carbon ratio (N / C) of the activated carbon fibers and the adsorption characteristics of nitrogen oxides (NOx) are substantially correlated. In the case of (%) or more, since the NOx adsorption characteristics are improved, it is considered that this nitrogen atom contributes to NOx adsorption. That is, activated carbon fibers made of polyacrylonitrile-based fibers containing nitrogen atoms are more sensitive to the photosensitive device 12 than activated carbon fibers made of cellulosic or phenol-based fibers containing no nitrogen atoms. It shows excellent adsorption and decomposition characteristics for NOx and the like generated when the body 11 is charged. In addition, since the activated carbon fiber has a high mechanical strength, it is particularly effective to use a polyacrylonitrile-based fiber as a starting material as the charging member of the photoreceptor.

Here, the charging member 13 in this copying machine
Will be described with reference to FIGS. 4 to 9. FIG. 4 is a sectional view and a side view showing the shape of the charging member in the copying machine of this embodiment, FIG. 5 is a side view showing the arrangement position of the charging member, and FIGS. 6 and 7 are modifications of the shape of the charging member. FIG. 8 is a graph showing the relationship between the amount of activated carbon fiber added to the charging member and the operation time up to the detection of ozone, and FIG. 6 is a graph showing a relationship with the operating time up to the present time.

As the form of the activated carbon fiber, there are 6 to 10 kinds of forms such as felt, tow, woven fabric and non-woven fabric according to the use, and it is possible to use it alone, but as the charging member 13 of this copying machine, The fiber is about 120μm in length
FIG. 4 (a) is a side view and FIG. 4 (b) is a cross-sectional view taken along the line AA of a sheet obtained by uniformly pulverizing the material as described below and processing it into a sheet by dispersing it in paper, resin, rubber or the like. Code 13
As shown by b, it is wound around a core bar 13a and used in a roll shape. These activated carbon fibers are manufactured by Kanebo, Unitika, Asahi Kasei Kogyo, Toho Rayon, Toho Veslon, Toyobo, Gunei Chemical and others. In this copying machine, a space member 13c is provided on the charging member 13 in order to perform non-contact charging. When the photoconductor 11 and the charging device 12 are arranged, as shown in FIG. 5, at least in the image forming area W of the photoconductor 11, the space member 13 c is provided between the photoconductor 11 and the charging member 13. A gap is provided so as to be in a non-contact state, and the width of the gap is usually set to about 50 to 150 μm.

As the shape of the charging member 13, besides the roll shape shown in FIG. 4, a plate shape as shown in FIGS. 6 (a) and 6 (b) or a corrugated shape as shown in FIG. 7 is used. be able to. In these figures, 13d, 1
Reference numerals 3f and 13h denote supports, respectively, and 13e and 13h.
g and 13i represent activated carbon fibers, respectively. When the charging member is formed in such a shape, the activated carbon fiber may be processed as it is, or may be pulverized to a length of 120 μm or less, preferably about 5 to 50 μm, and the acrylic resin described above may be used. It is also possible to add 60% or more to a binder resin made of a rubber material or a rubber material, mold and process into a desired shape. Also, when the roll-shaped charging member 13 shown in FIG. 4 is used, it may be formed in this manner.

Here, when the activated carbon fiber is added to the binder resin, the amount of addition affects the adsorption function. The activated carbon fibers are dispersed in a binder resin at various ratios, and are arranged and operated under the same conditions as in the case of assembling in the apparatus, and the photoconductor 11 is subjected to DC contact charging, DC non-contact charging and DC + AC superimposed non-contact charging. Each method was charged to -800 V, and the presence / absence of ozone was detected by a detector tube manufactured by Gastech Co., Ltd .. It became as shown in. As can be seen from this graph, as the amount of activated carbon fibers constituting the charging member 13 increases, the operating time until ozone detection, that is, the period during which the charging member 13 can sufficiently absorb the ozone generated, increases. In this graph, for example, when 80% is added, the durability is about 200 hours, but when it is 100%, generation of ozone can be completely eliminated for 500 hours or more. Further, when the charging voltage is set to -600 V, the time until ozone detection in the case of 80% addition is 200 hours or more, and when the charging voltage is reduced, the durability period of the activated carbon fiber becomes longer. Further, the time until ozone is generated also depends on the charging method. In the case of DC contact charging, the time until ozone is generated becomes longer, and the influence on the photoconductor is reduced. However, in the case of DC contact charging, the charging member 1
3 is in contact with the photoconductor 11, so that the charging member 13 is liable to be contaminated and easily abraded. Also,
In the case of DC non-contact charging, dirt on the photoreceptor is reduced, but there is a problem that the image is easily affected by the environment, and when the humidity is high, image unevenness is likely to occur. On the other hand, DC + A
In the C superimposed non-contact charging, the contamination of the charging member 13 is reduced,
This is an effective charging method according to the present invention because image deterioration hardly occurs in high humidity. In particular, when activated carbon fibers are used for the charging member 13, it is important to make the charging member 13 hard to wear and to increase durability. The result when the presence or absence of nitrogen oxides was detected under the same conditions using a Dyerec-made chemiluminescent nitrogen oxide measuring device (DY-108400) is also equivalent to the graph of FIG. Can be said that the generation of corona products can be completely eliminated.

Further, when a plurality of sheets (addition amount: 100%) consisting only of activated carbon fibers were stacked and the operation time until the detection of ozone was measured in the same manner as above, the result was as shown in the graph of FIG. . As can be seen from this graph, when the sheets with the added amount of 100% are used repeatedly, the durability period can be further extended. In the above experiment, the time until the generation of ozone and nitrogen oxides was detected was measured, but in fact, even if the generation of corona products was confirmed, the amount of If it is about 1/100 or 1/1000, the image is not immediately affected. Even if an amount of influence occurs, the image is not immediately affected because the surface property adjusting device 20 is operating.

Next, the surface property adjusting member 21 provided in the surface property adjusting device 20 will be described with reference to FIGS. FIG. 10 is a cross-sectional view showing a configuration of a surface property adjusting member of the copying machine according to this embodiment, FIG. 11 is a cross-sectional view showing another configuration example of the surface property adjusting member, and FIG. It is. The surface property adjusting member 21 increases the frictional resistance between the cleaning blade and the photoreceptor 11 in order to remove the corona product adhering to the coating layer 11e in which the inorganic fine particles are dispersed to prevent the image quality from being deteriorated. In order to suppress the acceleration of abrasion caused by this, it is installed in a copying machine. In this copying machine, the photoconductor 11 is attached to the surface property adjusting device 20 so as to always or intermittently make surface contact with the photoconductor 11, but it may be provided alone in a state where the photoconductor 11 is always in surface contact. In the case where the image is reproduced while eliminating the image deterioration of the photoconductor in which the image deletion has occurred, the photoconductor is used alone as described above.

The mounting position of the surface property adjusting member 21 in the image forming apparatus is preferably immediately after the completion of the toner cleaning, and is installed between the cleaning device 19 and the charge removing device 22 or the charging device 12 as shown in FIG. Is preferred. In this embodiment, a blade-shaped member as shown in FIG. 10 is used as the shape of the surface property adjusting member 21 mounted in the image forming apparatus. However, other shapes may be used. For example, a roller shape as shown in FIGS. 11 and 12 may be used.

The surface adjusting member 21 having the shape shown in FIG.
Is formed by wrapping an elastic member 21b having a density of 30 to 80 (kg / m ³ ), a tensile strength of 1.5 to 2 (kg / cm ² ) and an elongation of 60% or more with a nonwoven fabric 21a of ultrafine fibers. . As the elastic member 21b, for example,
Urethane foam MF-80, ESW, manufactured by INOAC
LE-20, malt plane SM55, SF, SMK,
Felt or the like can be used. The roller-shaped surface property adjusting member 31 shown in FIG. 11 and FIG.
φ Metal core, paper core, resin core pipe 31a
One layer is formed of an elastic member 31b having a thickness of 1 to 5 mm as a buffer material, and one to three nonwoven fabrics 31c of ultrafine fibers are formed thereon.

The roller-shaped surface property adjusting member 31 may be continuously rotated, or may be intermittently rotated so as to change its position every time a fixed number of images are formed. When rotating, it is desirable to rotate the photosensitive member 11 with a linear velocity difference or to rotate in the opposite direction (rotate in the same direction as the photosensitive member) on the contact surface. Alternatively, each time a predetermined number of images are formed, the photosensitive member 11 may be brought into contact with the photosensitive member 11 to be operated intermittently. Among the surface property adjusting members 21 and 31 for removing the corona product, at least the photosensitive member 1
The portion that comes into contact with 1 may be made of a nonwoven fabric of ultrafine fibers. Microfibers generally have a thickness of about 0.5d to 0.2d, and those having a thickness of 0.2d or less are called ultrafine fibers. Here, d is a unit called denier, and when the weight of a fiber having a length of 9000 m is 1 g, the thickness of the fiber is 1d (denier). When this is converted into a unit of thickness, the thickness of one ultrafine fiber is approximately 5 μm.
１1 μm, and the thickness of the ultrafine fibers is about 1 μm or less. As the material of the ultrafine fibers, chemical fibers such as polyester, polyurethane, and nylon are often used. It should be noted that the distinction between the ultrafine fibers and the ultrafine fibers is not strict, and in this specification, the term “fine fibers” includes the ultrafine fibers.

The fiber formed in the form of a non-woven fabric having such a diameter has no looseness, is hard to produce lint, has extremely good contaminant removal performance, and adheres to the coating layer 11e in which inorganic fine particles are dispersed. Contaminants such as corona products can be removed easily and well. Further, since there is little recontamination from contaminants once taken into the nonwoven fabric, the coefficient of friction of the surface of the photoconductor 11 can be reliably reduced.
Examples of such a non-woven fabric of ultrafine fibers include Tracy, Exaine (60% polyester, 40% polyurethane, about 0.2 d) manufactured by Toray Industries, Inc., Sabina Minimax, Klaussen (polyester, nylon, about 0.1%) manufactured by Kanebo. 3d), Miemier (acrylic 4) manufactured by Mitsubishi Rayon
5%, polyester 52%, polyurethane 3%, 0.3
d), Microstar (polyester, nylon, 0.2d) manufactured by Teijin Limited and the like can be used.

Here, if the fiber diameter of the nonwoven fabric is large, the effect of removing contaminants is reduced. For example, 30 μm or 60 μm
When a fiber cloth having a fiber diameter of the order of magnitude is used, the effect of removing contaminants hardly occurs. Further, when an unused photoreceptor having no coating layer 11e is wiped with a nonwoven fabric of ultrafine fibers, the friction coefficient of about 0.4 to 0.5 is reduced to 0.25.
It can be reduced to about 0.3. However, once the photoconductor 11 is used, it is almost impossible to reduce the friction coefficient only by wiping. On the other hand, in the case of the photoconductor 11 provided with the coating layer 11e in which the inorganic fine particles are dispersed by about 15 to 35%, even when used, 20 to 30 g
By wiping with a light force, the friction coefficient can be easily reduced to about 0.2 to 0.3.

In a situation where the corona product generated at the time of charging by the charging member 13 does not adhere to the photoreceptor 11, once the friction coefficient is reduced, a state where the friction coefficient is low for several tens to 100 sheets can be maintained. Since the adhesion of paper dust and toner components occurs gradually, it is inevitable that the coefficient of friction increases during copying many sheets. Therefore, in such a situation, the surface property adjusting member 21 for reducing the friction coefficient of the photoreceptor 11 and keeping it low is indispensable. When the charging member 13 is used for a long period of time and the generated corona product cannot be completely absorbed and decomposed and slightly affects the photoconductor 11, the surface property adjusting member 21 is particularly effective. Function.

Next, the friction coefficient of the surface of the photoconductor 11 will be described. In the photoreceptor 11 in which the coating layer 11e in which inorganic fine particles are dispersed is formed on the photosensitive layer 11f, the coefficient of friction of the surface is about 0.4 to 0.5 when nothing is performed. This is probably because the binder resin covers the inorganic fine particles. When the photosensitive member 11 is mounted on an image forming apparatus to form an image, the friction coefficient on the surface further increases. This is presumably because contaminants such as corona products, paper dust, and toner components adhere to the surface during image formation. The photosensitive member 11 in this state is replaced with the surface property adjusting member 21 described above.
, The coefficient of friction of the surface decreases to about 0.2 to 0.25. It is considered that this is because the contaminants attached to the coating layer 11e are removed and the inorganic fine particles are partially exposed and polished. It is also considered that the absolute contact area with the blade is reduced, and the lubricating action of the added silicone oil as a leveling material is also a factor.

The degree of decrease in the coefficient of friction when the surface property adjusting member 21 is used also depends on the amount of the inorganic fine particles added. When the preferred addition amount of 15 to 35% is added, the friction coefficient decreases to 0.2 to 0.25, but when it is further added, it may be 0.2 or less.
By reducing the friction coefficient of the surface of the photoconductor 11, wear of the photoconductor layer 11f and the protective layer 11e is suppressed, and at the same time, uneven wear and scratches of the photoconductor 11 are eliminated, and the durability of the photoconductor 11 is improved. Can be. Furthermore, since the adhesive force of the toner and the like is reduced, the cleaning property is improved,
Deterioration of image quality is eliminated. In addition, blade squeal disappears to reduce the load on the cleaning blade,
Image formation can be performed quietly.

As described above, there is a great advantage in reducing the friction coefficient of the surface of the photoconductor 11. In the present invention, since there is no generation of corona products, which is a main factor of image deletion, even if the friction coefficient of the surface of the photoreceptor 11 is reduced, image deletion does not occur, and there is no influence on the image. The lower the coefficient of friction, the longer the durability of the photoconductor 11 can be. However, if the temperature is too low, there is a possibility that a problem of development characteristics, for example, a problem that a trailing edge of an image becomes white, a character becomes thin, or the like may occur. It is good to be 0.5 or less.

The coefficient of friction described in this specification was calculated by the following measuring method. That is,
A photoconductor for measurement was fixed, and high-quality paper (type 6200 paper, manufactured by Ricoh Company) cut to a width of 30 mm and a length of 290 mm was prepared as a belt, and the high-quality paper was placed on the photoconductor and placed on one end of the belt. Attach a 100 g weight.
Then, attach a digital force gauge to the other end to measure the weight, pull it slowly, read the weight at the moment when the belt starts to move, and calculate the coefficient of static friction by the following equation. μs = 2 / π × ln (F / W) Here, μs: coefficient of static friction F: reading load W: weight of weight π: pi Note that this measuring method (Euler belt method) It is also disclosed in Japanese Unexamined Patent Publication No. Hei 9-166919. Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 <Preparation of Photoconductor for Evaluation> First, a photoconductor for evaluation was prepared by the following steps. φ30mm, length 340m
m, an aluminum drum having a wall thickness of 1.0 mm, using an undercoat layer (UL) coating liquid, a charge generation layer (CGL) coating liquid, and a charge transport layer (CTL) coating liquid having the following compositions. Dip coating was performed in this order, and a 3.5 μm-thick undercoat layer, a 0.2 μm-thick charge generation layer, and a 25 μm-thick charge transport layer were formed by heating and drying to prepare a photoreceptor. . Further, a binder resin, a donor, inorganic fine particles (metal oxide) and a solvent were placed on the photoreceptor in a glass pot and dispersed with a ball mill for 24 hours.
Make a coating solution of about 0.45 to 0.55 μm and apply it 1 to 3 times (about 1.5 to 2.
0 μm / time) and dried by heating to form a coating layer, thereby completing a photoconductor for evaluation. Here, the thickness of the coating layer was prepared with three stages of about 2.0 μm, 5.0 μm, and 8.0 μm as targets depending on the number of coatings.

The composition of each of the above coating liquids is as follows. Here, "parts" represents parts by weight.・ Coating solution for undercoat layer Alkyd resin (Beccosol 1307-60-EL, manufactured by Dainippon Ink and Chemicals, Inc.) 6 parts Melamine resin (Super Beckamine G-821-60, manufactured by Dainippon Ink and Chemicals, Inc.) 4 parts Titanium oxide (CR-EL manufactured by Ishihara Sangyo) 40 parts Methyl ethyl ketone 200 parts

Coating solution for charge generation layer Oxo titanium phthalocyanine pigment 2 parts Polyvinyl butyral (UCC: XYHL) 0.2 parts Tetrahydrofuran 50 parts

Coating solution for charge transport layer Bisphenol A-type polycarbonate (Z-Polyka manufactured by Teijin Chemicals Limited) 10 parts Low molecular charge transport material having the structure shown in Chemical Formula 1 12 parts Methylene chloride 100 parts Methyl phenyl silicone oil (50cs) One copy

[0092]

Embedded image

Coating Liquid for Inorganic Fine Particle Layer (Coating Layer) The coating liquid for the inorganic fine particle layer has a weight ratio of the inorganic fine particles to the binder resin and the low molecular charge transport material (Chemical Formula 2) of 25.
%, The ratio of the low molecular charge transport material to the binder resin is 7:10
And a mixture of cyclohexanone 2.5 and tetrahydrofuran 7.5 is used as a solvent. Binder resin: Polycarbonate resin (Z Polyka, Mv50,000 manufactured by Teijin Chemicals Ltd.) Inorganic fine particles: Alumina powder (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.)

[0094]

Embedded image

<Production of surface property adjusting member> The surface property adjusting member was 0.2 mm thick, 300 mm × 15 mm × 8.
mm L-shaped stainless steel plate, thickness 300 μm, length 30
0 mm polyethylene terephthalate (PET) film, 2 mm thick, 300 mm × 18 mm urethane foam (MF-80, manufactured by Inoac), 300 mm × 1
8mm ultra-fine fiber non-woven fabric (Kanebo, Super Multi Cloth using Clausen fabric, fiber diameter 2
Using a double-sided tape and a Teflon (registered trademark) tape, a surface property adjusting member having a configuration shown in FIG. 10 and fixed to the blade cleaning device section of FIG. 1 was produced.

<Preparation of Charging Device> First, activated carbon fibers pulverized to a length of 30 to 80 μm in an acrylic resin were mixed with 90 μm.
% Was applied onto a brass core metal having a diameter of 7.8 mm, and a charging member cut to a diameter of 13.7 to 14 mm was prepared. Both ends of the charging member have a width of 1
A PET (polyethylene terephthalate resin) film having a thickness of 0 mm and a thickness of 95 μm was adhered, and this was attached to a charging device as a space member. The volume resistance of the charging member is
When 100 V is applied between the metal core and the charging member, 2 to 5
× 10 ⁴ Ω · cm. The gap between the charging member and the photoconductor was 85 to 120 μm.

<Evaluation Method> The evaluation photoconductor, surface property adjusting member, and charging device produced by the above-described method were mounted on an evaluation machine (electrophotographic copying machine: modified aficio250, manufactured by Ricoh Company). Confirmation was made. The evaluation machine incorporates a circuit that uses a solenoid that periodically cleans the charging roller. In this experiment, this circuit was cut off. The charging roller was connected to a high voltage power supply via a 1 KΩ protection resistor. High voltage power supply is 1.5KV / 1K as AC voltage
As an offset DC voltage, an electric field (about 2 × 10 ⁵ V / cm) was applied so that the surface potential after charging became −600 V with a photoconductor having a coating layer of 5 μm. Yokogawa's Function Generator FG-300 is used as the power supply for applying high voltage.
And HV-255 manufactured by Nagano Aichi Electric Co., Ltd. were used.

The evaluation items were a coefficient of friction before and after the paper-passing running (formation of 50,000 sheets), an abrasion amount of the coating layer (a photosensitive layer when no coating layer was provided), a normal humidity environment (22 ° C./65%). R
H) and image quality and appearance of the photoreceptor in a high humidity environment (30 ° C./90% RH). For measuring the film thickness of the photosensitive layer, an eddy current film thickness meter (Fisher scope MMS) manufactured by Fisher was used. Use a self-made device to measure the coefficient of friction, 30mm x 297mm high quality paper,
Using a weight of 100 g and a digital force gauge (FGC-2 manufactured by Shinpo Kogyo Co., Ltd.), the above-mentioned Euler belt method was used. Image quality is specified by the specified standard test chart
A sheet to which an S-standard bamboo shoot chart was attached was evaluated as a manuscript. The evaluation results were as shown in Table 1.

[0099]

[Table 1]

Since activated carbon fibers are used for the charging member, ozone is not detected even after the formation of an image of 50,000 sheets, and adheres to the surface layer of the photoreceptor due to the effect of the surface property adjusting member made of a nonwoven fabric of ultrafine fibers. The coefficient of friction was also maintained at a low level of the order of 0.2 because the contaminants could be effectively removed. As a result, even in a high humidity environment, there was almost no image deterioration, and abrasion of the photosensitive layer could be suppressed to a low level. It was confirmed that the configuration of the present invention could increase the durability.

[Comparative Example 1] An evaluation photoconductor was prepared in the same manner as in Example 1, but with respect to the coating layer, an evaluation photoconductor without a coating layer and 25% of alumina dispersed therein. An evaluation photoconductor having a coating layer having a thickness of 2 μm was prepared. The charging member is formed by dispersing carbon on a stainless steel core of φ7.8 mm and having an electric resistance of 3 to 6 × 10 ⁵ Ω.
· A roller coated with epichlorohydrin rubber adjusted to have a diameter of 13.7 to 14 mm and a length of 320 mm by cutting was used. A PET film having a width of 10 mm and a thickness of 95 μm was attached to both ends in a circumferential direction, and was attached to a charging device as a space member. The gap between the charging member and the photoconductor is 95 to 1
It was 05 μm.

The evaluation photoreceptor and the charging device are mounted on an evaluation machine, and an offset voltage (DC) such that the charging potential of the photoreceptor becomes -600 V, as in the first embodiment,
An alternating voltage (AC) of 1.5 KV / 1 KHz was superimposed and applied. In Comparative Example 1, no surface property adjusting member was used. Under these conditions, the characteristics before and after the image formation of 50,000 sheets were evaluated in the same manner as in Example 1, and the results are as shown in Table 2.

[0103]

[Table 2]

When the coating layer was not formed, there was no problem in image quality, but significant wear was observed on the photosensitive layer of the photosensitive member. On the other hand, when the coating layer is formed, the abrasion amount is as small as about 1/3 of the case without the coating layer, but a filming phenomenon (a phenomenon in which the toner component is thinly formed on the photosensitive layer to form a film) occurs locally. In a high humidity environment, the resolution was significantly degraded. The filming phenomenon is a phenomenon that occurs when a contaminant remains on the photosensitive layer because the photosensitive layer is not uniformly worn, and absorbs moisture in the air to lower the electric resistance. This is because the fixation of components, paper powder, etc. could not be eliminated.

[Comparative Example 2] An evaluation photoconductor was prepared in the same manner as in Example 1, except that a coating layer was formed on the evaluation photoconductor without the coating layer and a film thickness in which 25% of alumina was dispersed. Evaluation photoconductors each having a coating layer of 5.3 μm, 8.2 μm, and 10.0 μm were prepared. As in the case of Example 1, the charging device in which activated carbon fibers were dispersed by 90% was applied to both ends of a charging member having a width of 10 mm and a thickness of 95 μm.
An ET (polyethylene terephthalate resin) film was attached and prepared. The gap between the charging member and the photoconductor is 83 to 125 μm.

The evaluation photoreceptor and the charging device are mounted on an evaluation machine, and an offset voltage (DC) such that the charging potential of the photoreceptor becomes -600 V as in the first embodiment.
, An alternating voltage (AC) of 1.5 KV / 1 KHz was superimposed and applied. In Comparative Example 2, no surface property adjusting member made of a nonwoven fabric of ultrafine fibers was used. Under these conditions, the characteristics before and after the image formation of 50,000 sheets were evaluated in the same manner as in Example 1, and the results are as shown in Table 3.

[0107]

[Table 3]

Even when the thickness of the coating layer was increased, a slight dulling occurred, but no defect in appearance was observed. Was seen. However, regarding the resolution, the image in a high humidity environment was generally good even in this state if the coating layer was 8 μm or less. However, since the surface property adjusting member was not provided, the friction coefficient was increased and the wear of the photosensitive layer was increased, and even with the coating layer, there was a problem in durability. Also, comparing Comparative Example 2-2 shown in Table 3 with Comparative Example 1-2 shown in Table 2, Comparative Example 2-2 shows that Comparative Example 1
Unlike -2, no degradation of resolution and no filming of the photoreceptor occurred in a high humidity environment. In these two examples, the thickness of the coating layer was almost the same, and only the material of the charging member was different. Since Comparative Example 2-2 using the charging member in which the fibers are dispersed shows good characteristics, the use of the activated carbon fiber for the charging member is effective in improving the durability of the photoreceptor and the image forming quality. You can see that.

Example 2 A photoconductor for evaluation was prepared in the same manner as in Example 1, except that the coating layer was made of alumina or titanium oxide (CR97, manufactured by Ishihara Sangyo) or a ratio of alumina to titanium oxide of 7 Each of the evaluation photoreceptors having a coating layer in which 25% of inorganic fine particles having a ratio of / 3 were dispersed was prepared. Such a coating layer was formed by coating the inorganic fine particles in the coating liquid for the inorganic fine particle layer described in Example 1 with a coating liquid in which each of the above compositions was changed. The same members as in Example 1 were used as the charging member and the surface property adjusting member made of the nonwoven fabric of the fine fibers. These members were set in the same evaluation machine as in Example 1, and the characteristics before and after image formation of 50,000 sheets were evaluated in the same manner as in Example 1, and the results are as shown in Table 4. .

[0110]

[Table 4]

When a photoreceptor having a coating layer in which alumina and titanium oxide were dispersed was used, the resolution was slightly lowered, but other characteristics were almost good, and the coefficient of friction was kept at a low level. As a result, the abrasion of the photosensitive layer was low, and three times the durability was confirmed as compared with the result of Comparative Example 2. In addition, the image quality was also a result with good uniformity.

Example 3 A photoconductor for evaluation was produced in the same manner as in Example 1, but the coating layer was formed by dispersing 25% of alumina in a thickness of 2.2 μm, 5.1 μm, and 7.8.
A photoconductor for evaluation having a coating layer of μm was prepared. The charging member has a thickness of 8 m with the central part expanded by about 1 mm.
m, a width of 13 mm, and a length of 300 mm as an aluminum plate, on which a woven 100% activated carbon fiber (F
W-210 made by Toho Rayon), fold it in three, and attach it so that there is no swelling while pressing the end with an acrylic plate,
The structure shown in FIG. 6A was manufactured. This was set and fixed on a charging device for evaluation, and a charging device was completed.
The gap between the center of the charging member and the photoconductor is 150 to
It was 200 μm. The same member as in Example 1 was used as a surface property adjusting member made of a nonwoven fabric of ultrafine fibers.

Each of these members was set in the same evaluator as in Example 1, and as an applied voltage condition, a voltage obtained by superimposing an alternating voltage of 1.8 KV / 1 KHz on a DC voltage (offset voltage) was used. , A protection resistor of 1 KΩ was connected. The surface potential of the photoreceptor was set to −2 × 10 ⁵ V / cm, and the characteristics before and after image formation on 50,000 sheets were evaluated in the same manner as in Example 1. The results were as shown in Table 5.

[0114]

[Table 5]

In this embodiment 3 in which the activated carbon fiber in the form of a woven fabric is used for the charging member, the experimental results are almost the same as those in the embodiment 1 in which the roller type charging member is used. Although slight occurrences occurred, the reproducibility of character images and photographs was almost good, and there was no problem with the friction coefficient or wear of the photoreceptor. However, when the film thickness is 7.8 μm, the amount of increase in the image potential is as large as 140 V, so that the contrast for forming an image is compressed, and the image margin is slightly reduced. If the amount of increase in the image potential is large, background contamination is likely to occur, and if the film thickness is larger than this, the image quality is degraded.

Comparative Example 3 An evaluation photoconductor was prepared in the same manner as in Example 1, except that a coating layer having a thickness of 0.90 μm in which alumina was dispersed by 25% was formed. A photoreceptor was prepared. The same charging device and surface adjustment member as in Example 3 were used. Each of these members was set in the same evaluator as in Example 1, and the characteristics before and after image formation of 50,000 sheets were evaluated in the same manner as in Example 3. The results were as shown in Table 6.

[0117]

[Table 6]

If the thickness of the coating layer is smaller than 1 μm as in Comparative Example 3, the coating layer will not be worn out during the formation of 50,000 sheets of images. In this comparative example, the toner is fixed because the coating layer has been locally worn. Since the durability of the coating layer also depends on the film thickness, if it is too thin, the durability is not sufficient, and it is necessary to secure a certain thickness.

Example 4 A photoconductor for evaluation was prepared in the same manner as in Example 1, except that the coating layer was 4.5 μm in which alumina was dispersed as inorganic fine particles by 10, 15, 20, and 35%. Each of the evaluation photoconductors on which the target coating layer was formed was prepared. As the charging device and the surface property adjusting member, the same members as in Example 1 were used. These members were set in the same evaluation machine as in Example 1, and the characteristics before and after image formation on 50,000 sheets were evaluated in the same manner as in Example 1, and the results are as shown in Table 7. .

[0120]

[Table 7]

The coefficient of friction showed a tendency to decrease in accordance with the amount of alumina added, and the amount of abrasion of the photosensitive layer tended to be in accordance therewith. When the dispersion amount of alumina was as small as 10%, the amount of abrasion was slightly increased, and a problem occurred in durability.
There is no problem in actual use. From this experiment, it was found that in the photoreceptor having the coating layer to which the inorganic fine particles were added, when the amount of the inorganic fine particles was in the range of 10% to 35%,
It was found that when the charging member and the surface property adjusting member in which the activated carbon fibers are dispersed act, the abrasion resistance and the image quality can be favorably maintained.

Comparative Example 4 A photoconductor for evaluation was produced in the same manner as in Example 1, except that a coating layer having a target thickness of 4.5 μm in which alumina was dispersed at 8% and 50% was used. Each of the formed photoconductors for evaluation was prepared. The same charging device and surface adjustment member as in Example 4 were used. Each of these members was set in the same evaluator as in Example 1, and the characteristics before and after image formation of 50,000 sheets were evaluated in the same manner as in Example 4. The results were as shown in Table 8.

[0123]

[Table 8]

When the dispersion amount of alumina was as small as 8%, the amount of abrasion of the coating layer was very large, and all the abrasion occurred before 50,000 sheets of image were formed. Although the photosensitive layer below the coating layer still remained, the toner adhered to the photosensitive member, and the image quality was significantly deteriorated. Conversely, when the dispersion amount is as large as 50%, the abrasion resistance is excellent, but a serious problem has occurred in the residual potential and the reproducibility of the resolution. As described above, if the dispersion amount of the inorganic fine particles is too small or too large, the image quality deteriorates. Therefore, the range of 10% to 35% shown in Example 4 is preferable.

In the above description, an example in which the present invention is applied to a copying machine has been described. However, the present invention is not limited to this, and is also applicable to an image forming apparatus such as a printer, a facsimile apparatus, and a digital multifunction peripheral. Can be. Further, the present invention can be applied to an analog type copying machine which projects a document image on a photosensitive member surface using a mirror and a lens.

[0126]

As is apparent from the above description, the image forming apparatus according to the present invention mainly comprises a photoreceptor having a coating layer in which inorganic fine particles are dispersed, and a catalytically conductive material. Charging member, and a surface property adjusting member for cleaning the surface of the photoreceptor, so that the corona product generated at the time of charging by the catalytic action of the charging member is effectively removed, so that the corona product Can eliminate the influence of the toner on the photoreceptor and efficiently remove contaminants adhering to the photoreceptor during the image forming cycle by the surface property adjusting member, so that stable image quality can be maintained for a long time, and High durability of the photoconductor can be achieved.

Here, if activated carbon fibers are used as the material of the charging member, ozone and nitrogen oxides, which are by-products generated at the time of charging, can be efficiently treated, and since they are conductive, The charging member can be formed without adding another conductive substance, and the catalyst function can be effectively exhibited. If at least the area of the surface adjustment member that comes into surface contact with the photoreceptor is made to have a structure in which the elastic member is included in a nonwoven fabric of ultrafine fibers, the contact with the photoreceptor is maintained, and contaminants adhering to the photoreceptor are efficiently removed. It is possible to reduce the coefficient of surface friction of the coating layer containing the inorganic fine particles, which has a great effect on stabilizing the image quality and increasing the durability of the photoconductor.

The charging member was placed in a non-contact state with the image forming area of the photoreceptor, and the photoreceptor was charged by non-contact charging, whereby the contamination of the charging member from toner and the like was reduced, and the catalyst was added. This can reduce the wear of the brittle charging member. For this reason, the adsorption / decomposition of the corona product by the charging member is unlikely to be reduced, and the effect can be maintained for a long period of time, so that a stable image can be formed. The voltage to be applied to the charging member is not only DC, but a DC voltage in which an alternating voltage is superimposed, so that even if the gap between the photoconductor and the charging member is not uniform, stable charging is performed, and Even when the charging member is made of a non-uniform material such as a woven fabric, the charging is corrected and a good charging state is obtained, so that stable image quality can be obtained.

By using alumina and / or titanium oxide as the inorganic fine particles dispersed in the coating layer, an appropriate hardness can be obtained, and contaminants adhering to the surface can be relatively easily removed. Not only is it small, but the coefficient of friction can be kept at a low level, which is effective in increasing the durability of the photoreceptor and stabilizing the image. If the thickness of the coating layer is set to 1 μm or more and 8 μm or less, good resolution can be obtained, and a charging member having catalytic action and conductivity;
Also, by using the surface property adjusting member together, even if the film thickness of the coating layer is 1 μm, the durability can be maintained more than before. Extending the durability of the photoconductor in accordance with the friction coefficient by adjusting the surface friction coefficient when the charging member and the surface property adjusting member act on the photoconductor within a range of 0.1 to 0.5. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of an image forming unit in a copying machine that is an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a partial cross-sectional view illustrating a configuration near a surface layer of a photoconductor provided in the image forming unit.

FIG. 3 is a partial cross-sectional view showing another configuration example.

FIG. 4 is a cross-sectional view and a side view showing a shape of a charging member in a copying machine according to an embodiment of the present invention.

FIG. 5 is a side view showing an arrangement position of the charging member.

FIG. 6 is a side view showing a modification of the shape of the charging member.

FIG. 7 is a side view showing another modification of the shape of the charging member.

FIG. 8 is a graph showing the relationship between the amount of activated carbon fiber added to the charging member and the operation time until ozone detection.

FIG. 9 is a graph showing the relationship between the number of stacked activated carbon fiber sheets used for the charging member and the operation time until ozone detection.

FIG. 10 is a sectional view showing a configuration of a surface property adjusting member of the copying machine according to the embodiment of the present invention;

FIG. 11 is a sectional view showing another configuration example of the surface property adjusting member.

12 is a perspective view of the surface property adjusting member shown in FIG.

[Explanation of symbols]

 11: Photoconductor 11a: Conductive support 11b: Subbing layer 11c: Charge generation layer 11d: Charge transport layer 11e: Coating layer 11f, 11g: Photosensitive layer 12: Charging device 13: Charging member 13a: Core metal 13b, 13e , 13g, 13i: activated carbon fiber 13c: space member 13d, 13f, 13h: support member 14: image exposure device 15: developing device 16: transfer device 17: separating device 18: fixing device 19: cleaning device 20: surface property adjustment Apparatus 21: Surface property adjusting member 21a: Nonwoven fabric of microfiber 21b: Elastic member 22: Static eliminator 31: Surface property adjusting member 31a: Core metal 31b: Elastic member 31c: Nonwoven fabric of microfiber

Continued on front page F-term (reference) 2H068 AA04 AA08 AA21 CA29 CA33 FC15 2H134 GA01 GB02 HD05 HD19 HE02 HE12 KD03 KG01 KG08 KH01 KH06 2H200 FA01 FA07 GA23 GB12 HA13 HA28 HB12 HB45 HB46 HB47 HB48 MA05 MB01 MC20 NA06

Claims (9)

[Claims] 1. An image forming apparatus for forming an image by electrophotography, comprising: a photoreceptor having a coating layer in which inorganic fine particles are dispersed; and a material having a catalytic action and being conductive. An image forming apparatus comprising: a charging member; and a surface property adjusting member for cleaning a surface of the photoconductor. 2. The image forming apparatus according to claim 1, wherein the material having a catalytic action and having conductivity is activated carbon fiber. 3. The surface property adjusting member has a structure in which at least a region that comes into surface contact with the photoreceptor has a structure in which an elastic member is included in a nonwoven fabric of ultrafine fibers alone or in the nonwoven fabric of ultrafine fibers. The image forming apparatus according to claim 1, wherein the image forming apparatus is a member that cleans a surface of the photoconductor by acting on the photoconductor. 4. The image forming apparatus according to claim 1, wherein the charging member is a member that is installed in a non-contact state with at least an image forming area of the photoconductor, and charges the photoconductor with a charge required for image formation by non-contact charging. The image forming apparatus according to claim 1, wherein: 5. The image forming apparatus according to claim 1, wherein the charging member is a member that charges the photosensitive member with an electric charge necessary for image formation by applying a DC voltage on which an alternating voltage is superimposed. The image forming apparatus according to claim 1. 6. The method according to claim 1, wherein the inorganic fine particles dispersed in the coating layer of the photoreceptor are fine particles of one of alumina and titanium oxide, or a mixture of alumina and titanium oxide. The image forming apparatus according to claim 1. 7. The dispersion amount of the inorganic fine particles is 10 to 35% by weight based on the binder resin and the low-molecular charge transport material of the photoreceptor.
The image forming apparatus as described in the above. 8. The image forming apparatus according to claim 1, wherein the coating layer has a thickness of 1 μm or more and 8 μm or less. 9. The inorganic fine particles dispersed in the coating layer of the photoreceptor are alumina or titanium oxide; the charging member is mainly composed of activated carbon fibers; and the surface property adjusting member is ultrafine fibers. The non-woven fabric is mainly composed of, the surface friction coefficient of the photoconductor when forming an image by applying the charging member and the surface property adjusting member to the photoconductor is 0.1 or more and 0.5 or less The image forming apparatus according to claim 1, wherein