JP2006154565A - Contact electrification system and image forming device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact electrification system which will not cause leakage of photoreceptor, even when the maximum diameter of particles contained in the photoreceptor is larger than 1 μm. <P>SOLUTION: This contact electrification system has a photo receptor, made by forming a photosensitive layer on the primer layer made on the front or rear surface of a conductive support, a charging roller disposed to turn keeping its surface, in contact with the photosensitive layer and having a conductive elastic layer between its shaft and the surface, and a power source for apply a dc charging voltage between the conductive support of the photoconductor and the shaft of the charging roller. The conductive elastic layer is made conductive, by dispersing an electron conductive material and an ion conductive material in the elastic material and has conductivity of the extent of not breaking down the insulation of the photoconductive layer with the current concentrated at the curved section, when a current flows between the charging roller and the photosensitive layer by the charging voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a contact charging device and an image forming apparatus including the contact charging device.

  Conventionally, as a charger of an electrophotographic image forming apparatus used for a copying machine, a laser printer, a facsimile, etc., a corotron charger using a wire and a case, a surface of a photoreceptor using a wire and a case, and a grid electrode. Many scorotron chargers that stabilize the potential have been used. In particular, the scorotron charger has an advantage that the surface potential of the photoreceptor can be stably controlled by using a grid disposed between the wire and the photoreceptor surface, and has been widely used as a charger.

  However, these chargers have a drawback that a high voltage of 5 to 8 kV needs to be applied and the amount of generated ozone is large. In order to eliminate such drawbacks, in recent years, a charger for bringing a charging member into contact with or close to a photosensitive member has been developed. Contact roller chargers, non-contact roller chargers, brush chargers, magnetic brush chargers, and the like. These chargers use a charging method based on micro-gap discharge except for some injection charging methods. These chargers have become mainstream chargers as chargers that can solve the problems of high-voltage power supply and ozone, which were the disadvantages of scorotron chargers. However, compared with the conventional scorotron charger, the uniformity of charging is slightly inferior, and there is a drawback that dielectric breakdown is likely to occur due to photoreceptor leakage, that is, local current concentration of the photoreceptor layer.

  Regarding the charging uniformity of contact charging, a voltage obtained by superimposing an AC voltage component having a peak-to-peak voltage more than twice the charging start voltage on a DC voltage corresponding to the surface potential of the desired photoreceptor is applied to the contact charging member. A contact charging method using an AC charging method has been proposed (see, for example, Patent Document 1). However, a charger that superimposes an AC voltage flows a larger current than a charger that uses a DC voltage. That is, the air discharge current generated between the charger and the photoreceptor is large. For this reason, the film thickness of the photoconductor is larger than that of a charger using a DC voltage, and therefore, photoconductor leakage is likely to occur. Further, the durability of the charging member tends to be low. Furthermore, in order to superimpose a high-voltage AC voltage that is a peak-to-peak voltage that is twice or more the charging start voltage when a DC voltage is applied, an AC power source is required in addition to the DC power source, which increases the cost of the device itself. There was a problem.

  The photoreceptor leak is caused by overlapping various phenomena. As mentioned above, it may be caused by a decrease in the pressure resistance of the photoconductor due to a decrease in the film thickness of the photoconductor. The current may concentrate on a defective portion such as adhesion of foreign matter on the surface of the body, dirt, or fine holes, which may cause a photoconductor leak. This photoconductor leakage causes black spot or white spot-like spot defects. In the case of remarkable defects, the charging performance of the charger itself is reduced, or charging failure is caused over the entire axial direction of the photoconductor. It was.

  In particular, in recent years, there has been an increase in the number of color image forming apparatuses or cleaner-less image forming machines that do not have a dedicated photoconductor cleaner mechanism, and accordingly, the problem of photoconductor leakage has attracted attention. This is because the amount of fine external additives such as silica increases in the color toner used in the color image forming apparatus as compared with the conventional monochrome toner. This is because the fine external additive easily passes through the cleaner blade, adheres to the charging member, and easily creates a situation where current is concentrated. Also, in cleaner-less image forming apparatuses, since no cleaner is provided in front of the charger, the toner and carrier remaining on the surface of the photoconductor after the transfer enters the nip between the charging member and the photoconductor, and current is concentrated. It is because it is easy to produce.

In order to prevent such photoconductor leakage, the cleaning of the charging member and the undercoat layer of the photoconductor, that is, the layer provided between the photoconductive layer and the lower conductive support is made as thick as possible. It is effective to improve the concealability of the irregularities on the surface of the support. However, if the undercoat layer of the photoreceptor is too thick, there is a problem that the residual potential increases remarkably and cannot be used. Therefore, in an image forming apparatus using a contact charger, the surface of the conductive support of the photoconductor is anodized as a technique for preventing photoconductor leakage without increasing the thickness of the undercoat layer of the photoconductor. Has been proposed (see, for example, Patent Document 2). In addition, it has been proposed to provide an undercoat layer made of polyimide, polyamide, polyurea, or polyurethane formed by vapor deposition polymerization on a photoreceptor (for example, see Patent Document 3). In addition, in an electrophotographic photoreceptor containing a specific crystal type titanyl phthalocyanine as a charge generation material, an undercoat layer made of a thermosetting resin such as a phenol resin, an epoxy resin, a melamine resin, an unsaturated polyester resin, or a polyimide resin is provided. It has been proposed to provide (see, for example, Patent Document 4).
Thus, at present, in an image forming apparatus using a contact charger, a photoconductor subjected to a conductive support treatment is often used.

On the other hand, regarding a technique for preventing leakage of the photoreceptor due to foreign matter, it has been proposed that the maximum diameter of particles contained in the photoreceptor is 1 μm or less (see, for example, Patent Document 5). Discharge breakdown of the photoreceptor due to contact charging is caused by particles having a maximum particle size exceeding 1 μm contained in the photoreceptor, that is, aggregates of charge generating materials such as azo pigments and phthalocyanine pigments dispersed in the photosensitive layer. Or agglomerates of solid lubricants such as tetrafluoroethylene resin powder and vinylidene fluoride resin powder, or solid impurities and chips by cutting a support in an intermediate layer such as an undercoat layer, etc. Since solid impurities and the like occur as nuclei, the maximum diameter of the particles contained in the photoreceptor is 1 μm or less.
JP-A 63-149668 Japanese Patent Laid-Open No. 5-34964 JP-A 64-6962 JP-A-3-33856 Japanese Patent Laid-Open No. 2-67575

  However, as described above, in order to reduce the maximum diameter of the particles contained in the photoreceptor to 1 μm or less, the coating liquid must be filtered and centrifuged many times in the pre-coating process. This leads to a cost increase in the previous process. Further, even if the coating liquid is sufficiently filtered and centrifuged, depending on the material, the charge generation material aggregates during the coating, which causes a problem that the selection range of the charge generation material is narrowed.

  In order to prevent leakage of the photosensitive member, use a photosensitive member that has been subjected to a conductive substrate treatment as described above, for example, an alumite treatment or a thermosetting resin coating applied to the conductive substrate of the photosensitive member. ing. Formation of the undercoat layer of the photoreceptor by such treatment is not preferable from the viewpoint of productivity because it requires vapor deposition or high-temperature heating. In particular, when a polyimide resin that is insoluble or hardly soluble in an organic solvent is used for the undercoat layer, because of poor coating suitability, a layer is formed by vapor deposition polymerization, or a polyamic acid solution is applied and heated for polymerization. However, these methods require a process of heating to a high temperature of 250 ° C. or higher, resulting in poor productivity and an increase in product cost.

  The present invention has been made in view of such circumstances, and we have investigated a contact charging device that does not cause photoconductor leakage even when the maximum diameter of particles contained in the photoconductor is larger than 1 μm. As a result, excellent characteristics and good results were obtained. Further, a system that does not cause photoconductor leakage without performing a special conductive substrate treatment was examined.

  According to the present invention, a photosensitive member in which a photosensitive layer is formed on the surface of a conductive support or an undercoat layer formed on the surface of the conductive support, and the surface rotates while being in contact with the photosensitive layer. A charging roller having a conductive elastic layer disposed between the shaft and the surface, and a charging power source for applying a DC charging voltage between the conductive support of the photosensitive member and the shaft portion of the charging roller. Since the conductive elastic layer is made conductive by dispersing the electronic conductive material and the ion conductive material in the elastic material, the current flowing between the charging roller and the photosensitive layer is bent by the charging voltage. Provided is a contact charging device for an electrophotographic process, characterized by having a conductivity that does not cause partial breakdown and cause dielectric breakdown of a photosensitive layer.

  In the contact charging device of the present invention, the conductive elastic layer of the charging roller is made conductive by dispersing the electronic conductive material and the ionic conductive material in the elastic material so as to have conductivity. Since the current flowing between the photosensitive layers is concentrated in a curved portion and has a conductivity that does not cause dielectric breakdown of the photosensitive layer, the occurrence of photosensitive member leakage is suppressed, and the photosensitive member film is compared with an AC voltage. A charging characteristic with good uniformity can be obtained by applying a DC voltage to the charging roller with a small amount of reduction, a long life of the charging roller, and a low power supply cost.

  In order to solve the above-mentioned problems, the inventors have studied and in order to avoid the photoconductor leakage, it is effective to apply only a DC voltage to the charging member in order to reduce the electric field difference between the charging member and the photoconductor. The knowledge that it is. However, when a power source having a relatively slow rise time is used, a photoreceptor leak occurs. Therefore, as a result of further studies, the maximum diameter of the particles contained in the photoconductor is obtained by changing the conductive method of the base layer of the charging member to a hybrid method that combines two types of materials, an electronic conductive material and an ionic conductive material. It has been found that good images can be obtained for a long time without causing photoconductor leakage to about 50 μm or less.

  The contact charging device of the present invention comprises a photosensitive member formed with a photosensitive layer on the surface of the conductive support or an undercoat layer formed on the surface of the conductive support, and a rotating member while the surface is in contact with the photosensitive layer. A charging roller that is arranged to move and has a conductive elastic layer between the shaft and the surface, and a charging roller that applies a DC charging voltage between the conductive support of the photosensitive member and the shaft of the charging roller A power source, and the conductive elastic layer is made conductive by dispersing an electronic conductive material and an ionic conductive material in the elastic material, so that the charging roller and the photosensitive layer are electrically charged. It is characterized in that the flowing current is concentrated in a curved portion so that the dielectric breakdown of the photosensitive layer does not occur.

Here, the electronic conductive material means a material in which an electronic conductive agent such as carbon is added and dispersed in a binder material, and when a voltage is applied, electrons are tunneled between the electronic conductive agents. It shows conductivity by moving by.
The ion conductive material means a material in which a conductive agent having ionic conductivity is dispersed in a binder material. When voltage is applied, the ion is propagated between the molecular chains to make the conductivity. Show.
The binder material may be, for example, natural rubber, synthetic rubber, polyamide resin, polyurethane resin, silicon resin, or the like.
In addition, as the electronic conductive agent, for example, carbon black, graphite, conductive metal oxide, or the like can be used. More specifically, the conductive metal oxide may be ZnO.Al ₂ O ₃ , SnO ₂ .Sb ₂ O ₅ , TiO.TiO ₂ or the like.
As the ionic conductive agent, for example, an alkali metal salt or a quaternary ammonium salt can be used. Here, the alkali metal salt may be, for example, a sodium salt, a potassium salt, a lithium salt, or the like. Further, the quaternary ammonium salt is, for example, lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, modified fatty acid / dimethylethylammonium salt perchlorate, chlorate , Borofluoride salts, sulfate salts, ethosulfate salts, benzyl halide salts such as benzyl bromide salts, benzyl chloride salts, and the like.

  In the case of an electronic conductive type charging member, the electrical conductivity varies greatly due to the tunnel effect in which electrons are transferred between carbon in the binder resin (or binder polymer) by a high voltage. . In addition, since the electronic conductive agent is difficult to uniformly disperse in the binder resin, the electric resistance varies greatly. For this reason, when a high voltage power supply having a slow voltage rise characteristic is used, the time for electrons to move through the binder resin having a large variation in the conductive agent becomes long. Since electrons move in an unstable state, it is considered that the current concentrates at a certain point of the roller where the resistance is relatively low, causing a photoreceptor leak. For this reason, it is considered that a photoconductor leak that did not occur with a high-voltage power supply with a fast rise characteristic will also occur when a high-voltage power supply with a slow voltage rise characteristic is used.

In the case of an ion conductive type charging member, a relatively good result was obtained with respect to the photoreceptor leakage, but there was a problem that the ion conductive material oozes out and contaminates the photoreceptor.
On the other hand, in the case of a hybrid type charging member, since the ion conductive material is dispersed, uniform dispersion in the binder resin is possible, and variation in electric resistance is small. For this reason, current concentration is unlikely to occur as in the case of an electronic conductive type charging member, and even if electrons move in an unstable state, current does not concentrate at a certain point, and no photoconductor leakage occurs. Conceivable. Further, since the content of the ionic material is small, it is possible to reduce the bleeding of the ionic conductive material, which is a problem with the ionic conductive type charging member, by providing a thin surface layer.
Therefore, the conductive elastic layer adds the electron conductive material in a ratio of 5 to 50 parts by weight with respect to the weight 100 of the elastic material, and further adds the ion conductive material to the weight 100 of the elastic material. It is preferable to add at a ratio in the range of 0.1 to 10 parts by weight.
If the weight ratio of the electronic conductive material is smaller than the above range, the resistivity of the conductive elastic layer is too high to obtain a sufficient charging potential. On the other hand, when the weight ratio of the electronic conductive material is larger than the above range, the load resistance when the photoreceptor side is viewed from the output of the power source to which the charging voltage is applied is too small and the photoreceptor is likely to leak.
On the other hand, since the ion conductive material has a small effect of lowering the resistance value, if the weight ratio is smaller than the above range, the effect of adding the ion conductive material is insufficient and a sufficient charging potential cannot be obtained. On the contrary, even if the addition amount of the ion conductive material is larger than the above range, not only does the resistance of the conductive elastic body decrease in proportion to the addition amount of the ion conductive material, but also the bleedout ( Bleeding) is a problem.

  The photosensitive layer may be a layer containing particles having a maximum diameter in a range of more than 1 micrometer and not more than 45 micrometers. As described above, in an image forming apparatus that charges a photosensitive member by applying a DC voltage to a charging member disposed in contact with or close to the photosensitive member, the particle size contained in the photosensitive member is less than 1 micrometer. In addition, by setting it within a range of 45 micrometers or less, it is possible to prevent photoconductor leakage even for long-term use.

In the contact charging device of the present invention, the particle diameter of the photosensitive layer is controlled to 1 micrometer or less as in the prior art, even if the particle diameter includes particles in the range of 1 micrometer to 45 micrometers or less. Even if it is not necessary, the occurrence of leakage of the photoreceptor is avoided, so that it is not necessary to remove the aggregated particles from the photosensitive layer material in the production process of the photoreceptor, and the production process can be simplified. As a result, production efficiency can be improved and costs can be reduced.

  Further, the conductive support may have a surface roughness of 0.5 to 2.0 micrometers on the surface on which the photosensitive layer is formed. If the maximum height Rmax (JIS standard B 0601-1982) among the parameters representing the surface roughness of the conductive support is in the range of 0.5 to 2.0 micrometers, the exposure irradiated to the photoreceptor. The light does not interfere with the reflection from the surface of the conductive support, and the photoconductor leakage can be avoided.

  Furthermore, the photosensitive layer may comprise a charge generation layer formed on a conductive support and a charge transport layer having a thickness of 15 to 38 micrometers formed on the charge generation layer. If the layer pressure of the charge transport layer is within the range of 15 to 38 micrometers, the photoreceptor leak does not occur and image quality deterioration due to carrier diffusion does not occur.

  The conductive support may be a support formed by applying a thermoplastic resin to the surface of aluminum. In the prior art, an alumite process or a process of coating a thermosetting resin has been performed on the conductive support of the photoreceptor, and expensive equipment was necessary for the process. For example, the surface treatment of the support is performed by applying a thermoplastic resin, which is cheaper than the above-mentioned treatment, and over a long period of time, black spots or white spot-like spot defects due to photoreceptor leakage, and image degradation due to an increase in residual potential Can be prevented.

  The charging roller may have a surface roughness of 0.5 to 14.5 micrometers on the surface in contact with the photosensitive layer. When the surface roughness of the charging roller is 0.5 to 14.5 micrometers, a stable charging potential can be secured. Also, good characteristics can be obtained in terms of the cleaning property for cleaning the surface of the charging roller.

  The charging power source may have a rise time of 0.02 to 90 milliseconds from the start of charging voltage application until the charging roller shaft voltage reaches the target voltage. Here, the rise time refers to the time from when the charging shaft roller shaft voltage rises from 0 V to the target voltage until it reaches the target voltage of 10 percent until it reaches the target voltage of 90 percent. If the rising time of the charging voltage is in the range of 0.02 to 90 milliseconds, the occurrence of photoconductor leakage can be avoided.

The image forming apparatus of the present invention includes any one of the contact charging devices.
The image forming apparatus includes a plurality of photoconductors for forming images of different colors to form a color image, and the contact charging device arranged corresponding to each photoconductor to charge the photoconductor The image forming apparatus may be provided.

  Alternatively, the image forming apparatus of the present invention includes a developing unit having a function of cleaning the photosensitive member by adsorbing charged particles on the surface of the photosensitive member to the developing unit side, and any one of the contact charging devices. In this way, in an image forming apparatus that employs a so-called cleaner-less system that does not have a dedicated cleaning unit, the charging roller is electronically conductive even if foreign matter enters the nip between the photoconductor and the charging roller. Since the conductive elastic layer is made conductive by dispersing the conductive material and the ion conductive material, the photosensitive member is not leaked and good image quality can be maintained over a long period of time.

  The image forming apparatus may further include a charging roller cleaning unit that cleans the surface of the charging roller, so that the contact charging device may have a photoconductor cleaning function. In this way, the charged particles charged to the opposite polarity to the charging voltage are cleaned by the charging roller, and the charged particles charged to the same polarity as the charging voltage are cleaned by the developing unit. More stable cleaning is possible for charged particles.

  Further, a toner disturbing member for disturbing the toner remaining on the surface of the photosensitive member after the transfer is disposed in front of the contact charging device in the image forming apparatus, and the residual toner passes through the contact charging device after being disturbed by the toner disturbing member. It may be configured to. In this way, since the residual toner is agitated before the contact charging device, cleaning of the residual toner by the developing portion or the developing portion and the charging roller is further facilitated, and good cleaning properties can be obtained and good image quality can be obtained. Is obtained.

Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings.
In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.
(Embodiment)
An image forming apparatus to which the present invention is applied is an electrophotographic image forming apparatus. It has the function of forming a toner image on a photoconductor and transferring it to a recording paper (sheet) by an electrophotographic process having charging, exposure, development, transfer, cleaning, fixing, and static elimination steps. It is applied to electrophotographic apparatuses such as copying machines, laser printers and facsimiles. Also, it can be applied to a monochrome machine and a color machine.

  First, a monochrome printing type image forming apparatus to which the present invention is applied will be described with reference to FIG. FIG. 1 is an explanatory view showing an embodiment of the contact charging device of the present invention. As shown in FIG. 1, a monochrome printing type image forming apparatus 10 (monochrome machine) forms a monochrome image on a predetermined recording sheet in accordance with image data input from the outside. As shown in FIG. 1, the photoconductor 1, the charger 20, the exposure unit 30, the development unit 40, the transfer unit 50, the fixing unit 60, and the cleaning unit 70 are provided.

  The photoreceptor 1 and the charger 20 are disposed in contact with each other. The charger 20 uniformly charges the surface of the photoreceptor 1 with power supplied from a power source. Details of the photoreceptor 1 and the charger 20 will be described later.

  For the exposure unit 30, for example, a laser scanning unit (LSU) provided with light emitting elements arranged in an array, for example, an EL or LED writing head, a laser irradiation unit, and a polygon mirror is used. The photosensitive member 1 charged by the charger 20 is exposed according to input image data, thereby forming an electrostatic latent image corresponding to the image data on the surface of the photosensitive member 1.

  The developing unit 40 includes a developing roller 4 for supplying toner to the photoreceptor 1 and develops the electrostatic latent image formed on the photoreceptor 1 with toner. As a result, a toner image corresponding to the image data is formed on the surface of the photoreceptor 1. In this example, a two-component developer composed of a nonmagnetic toner and a magnetic carrier is used as a developer used for development. Note that not only the two-component developer but also a one-component developer may be used.

  The transfer unit 50 transfers a toner image onto the recording paper P that is supplied from a paper feeding device (not shown) and is conveyed in the Y direction. As a transfer method, there are a charger method and a roller method. After the transfer of the toner image, the fixing unit 60 fixes the toner image on the recording paper P by heat melting.

  The cleaning unit 70 scrapes and collects the toner remaining on the photosensitive member 1 after the transfer of the toner image by the transfer unit 50. Instead of providing the cleaning unit 70, a charging / cleaning device and a developing / cleaning device may be provided as described later (see FIG. 7).

  Next, the photoreceptor 1 will be described in detail. FIG. 2 is a cross-sectional view showing the layer structure of the photoreceptor 1 shown in FIG. As shown in FIG. 2, the photoreceptor 1 has a conductive support 1a (for example, a metal drum such as aluminum) as a base, and an undercoat layer 1b is formed on the outer peripheral surface thereof. A photosensitive layer 1b is formed on the undercoat layer 1b. The photosensitive receiving layer 1e as a layer is applied and formed. The photosensitive receiving layer 1e is formed of a charge generation layer 1c and a charge transport layer 1d. Thus, in the photoreceptor 1, the undercoat layer 1b, the charge generation layer 1c, and the charge transport layer 1d are formed in this order on the conductive support 1a.

The conductive support 1a plays a role as a support for the undercoat layer 1b and the photosensitive receiving layer 1e at the same time as the electrode of the photoreceptor 1, and has a cylindrical shape, a plate shape, a film shape, Any of a belt shape may be sufficient. The conductive support 1a is made of a metal material such as aluminum, stainless steel, copper, or nickel, or a polyester film provided with a conductive layer such as aluminum, copper, palladium, tin oxide, or indium oxide on the surface, or a phenol resin. Examples include insulating materials such as pipes and paper tubes. Those having a volume resistance of 10 ¹⁰ Ωcm or less are preferred, and the surface may be oxidized to adjust the volume resistance.

  The undercoat layer (coat layer) 1b is formed from, for example, polyamide, polyurethane, cellulose, nitrocellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, anodized aluminum film, gelatin, starch, casein, N-methoxymethylated nylon, etc. Is done. Further, titanium oxide, tin oxide, and aluminum oxide particles may be dispersed in these. The undercoat layer 1b has a thickness of about 0.1 to 10 μm and serves as an adhesive layer between the conductive support 1a and the photosensitive receiving layer 1e. In addition, it also serves as a barrier layer that suppresses the flow of charges from the conductive support 1a to the photosensitive receiving layer 1e. In this way, the undercoat layer 1b maintains the charging characteristics of the photoconductor 1, so that the life of the photoconductor 1 itself can be extended. This undercoat layer is not always necessary. By appropriately surface-treating the conductive support 1a, the following charge generation layer can be obtained with good adhesion, and when the life of the photoreceptor is sufficiently obtained, the undercoat layer is omitted and the manufacturing process is omitted. It can be simplified.

  The charge generation layer 1c is formed including a known charge generation material. As the charge generation material of the charge generation layer 1c, any of inorganic pigments, organic pigments, and organic dyes can be used as long as they absorb visible light and generate free charges. Inorganic pigments include selenium and its alloys, arsenic-selenium, cadmium sulfide, zinc oxide, amorphous silicon, and other inorganic photoconductors. Examples of organic pigments include phthalocyanine compounds, azo compounds, quinacridone compounds, polycyclic quinone compounds, and perylene compounds. Examples of organic dyes include thiapyrylium salts and squarylium salts. Among them, a preferable quinone-based generator is a phthalocyanine compound, and it is particularly preferable to use a titanyl phthalocyanine compound. Particularly good sensitivity characteristics, charging characteristics, and repetition characteristics can be obtained.

  In addition to the above-mentioned pigments and dyes listed above, as a chemical sensitizer, an electron accepting substance, for example, a cyano compound such as tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane, anthraquinone, p- Quinones such as benzoquinone, nitro compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitrofluorenone, or xanthene dyes, thiazine dyes triphenylmethane as optical sensitizers A dye such as a dye may be added to the charge generation layer 1c. Preferably, the above organic photoconductive compounds such as organic pigments and organic dyes are used. In the charge generation layer 1c, a charge generation material is dispersed in a suitable solvent together with a binder resin to prepare a coating solution. The coating liquid is filtered using a filter, or the particle size is controlled by centrifugation or the like. The coating liquid is applied to the conductive support 1a and dried or cured to form a film. The film thickness of the charge generation layer 1c is about 0.05 to 5 μm, preferably about 0.1 to 1 μm. In general, the charge generation layer 1c is formed by vapor deposition such as vacuum deposition, sputtering, or CVD, or by pulverizing a charge generation material with a ball mill, sand grinder, paint shaker, ultrasonic disperser, etc. In the case where the conductive support 1a is a sheet, a spray method is used when the conductive support 1a is a cylindrical body, such as a baker applicator, a bar coater, casting, or spin coating. A method of forming by a vertical ring method, a dip coating method or the like is known.

Specific examples of the binder resin used for the charge generation layer 1c include resins such as polycarbonate, polyarylate, polyvinyl butyral, polyester, polystyrene, polyvinyl chloride, phenoxy, epoxy, silicon, and polyacrylate.
Examples of the solvent include isopropyl alcohol, cyclohexanone, cyclohexane, toluene, xylene, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, dioxolane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, and ethylene glycol dimethyl ether. In addition, those other than those listed here may be used, and alcohol-based, ketone-based, amide-based, ester-based, ether-based, hydrocarbon-based, chlorinated hydrocarbon-based or aromatic solvents may be used singly or blended. Good. However, when considering reduction of sensitivity due to crystal transition during milling and milling of charge generating materials, and deterioration of properties due to pot life, cyclohexanone, 1,2-dimethoxyethane, methyl ethyl ketone, tetrahydroquinone that hardly cause such crystal transition Either of these is preferably used.

  The charge transport layer 1d is formed including a known charge transport material. The charge transport material may be any organic photoconductive compound that can transport the charge generated in the charge generation layer 1c. Hydrazone derivatives, pyrene derivatives, pyrene-formaldehyde condensates and derivatives thereof, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, stilbene derivatives, enamine derivatives, α-phenylstilbene derivatives, benzidine derivatives, A diarylmethane derivative, a triarylmethane derivative, an anthracene derivative, a pyrazoline derivative, an indene derivative, a butadiene derivative, a polysilane compound, a polygermane compound, and the like can be given, but the charge transport material is not limited thereto.

  The charge transport layer 1d may contain an electron transport material. Specifically, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, diphenyl derivatives, benzoquinone derivatives, etc. Although it is mentioned, it is not limited to these. Moreover, stabilizers, such as antioxidant, a leveling agent, and a plasticizer can also be added to the charge transport layer 1d as necessary. As the antioxidant, generally, an antioxidant that is added to a resin or the like and used can be used as it is. For example, vitamin E, hydroquinone, hindered amine, hindered phenol, paraphenylenediamine, arylalkane and derivatives thereof, organic sulfur compounds, organic phosphorus compounds, and the like may be used. As the leveling agent, silicone oils, polymers or oligomers having a perfluoroalkyl group in the side chain can be used, and the amount used is suitably 1 part by weight or less with respect to 100 parts by weight of the binder resin.

  The charge transport layer 1d is formed using the same method and apparatus as the charge generation layer 1c described above. The charge transport layer 1d is formed by dissolving or dispersing a charge transport material in a suitable solvent together with a binder resin, coating the conductive support 1a on which the charge generation layer 1c is formed, and drying or curing the film. Form. In the coating liquid for the charge transport layer 1d, one or several kinds of charge transport materials, binder resins, and additives are measured and dissolved in a predetermined amount of an organic solvent. At this time, the method may be prepared by simultaneously dissolving, but preferably, the method is prepared by first dissolving the binder resin in a solvent and then introducing and dissolving the charge transport material. According to this method, the molecular dispersibility of the charge transport material in the binder resin is improved, and crystallization of a potential and local charge transport material in the film is suppressed, thereby improving the initial sensitivity and repeating. Potential stability during use, good image characteristics, and the like are imparted. As a method for forming the charge transport layer 1d, a bakery applicator, bar coater, casting, spin coating or the like is used when the conductive support 1a is a sheet, and a spray method is used when the conductive support 1a is a drum. A vertical ring method, a dip coating method, or the like is used. In particular, the dip coating method is preferable from the viewpoint of productivity and cost.

  Examples of the binder resin used for the charge transport layer 1d include those similar to the binder resin used for the charge generation layer 1c described above, and are not particularly limited. For example, vinyl polymers such as polycarbonate, polymethyl methacrylate, polystyrene, polyvinyl chloride, and copolymers thereof, polyester, polyester carbonate, polyarylate, polysulfone, polyimide, phenoxy, epoxy, silicone resin, or partial cross-linking curing thereof. Known binder resins such as products are used.

  At this time, it is important to control the maximum diameter of the particles contained in the photoreceptor. If the contained particles are 50 μm or less, it is possible to design a system that does not cause photoconductor leakage for a long time by using a hybrid charging member conductive system.

  It is important to set the initial film thickness of the charge transport layer 1d to 15 to 38 μm. When the film thickness is 12 μm or less, although high resolution can be obtained by reducing the diffusion of traveling charges in the charge transport layer 1d, dielectric breakdown occurs due to application of a high electric field to the photosensitive receiving layer 1e, and image defects frequently occur. It tends to be easier. In addition, there is little margin for film abrasion due to the cleaning process during use, and the life of the photoreceptor is relatively short in design. In general, a photoconductor used for a contact charger is formed thicker than a photoconductor used for scorotron charging. However, when the film thickness is 41 μm or more, the life of the photoreceptor can be extended, but in the process in which the charge injected from the charge generation layer 1c travels through the charge transport layer 1d, the charge diffusion that deviates from the electric field direction becomes large. The resolution tends to decrease. The charge transport layer 1d may contain additives such as known plasticizers, antioxidants, ultraviolet absorbers, and leveling agents in order to improve film formability, flexibility, coatability, and the like. Good.

  A specific example in which the initial film thickness of the charge transport layer 1d is set to 10 to 41 μm is shown in Example 8 to be described later. Thus, by setting the thickness of the charge transport layer 1d to 15 μm or more, the photosensitive member can be used without using an expensive photosensitive member in which the conductive support of the photosensitive member is coated with an alumite treatment or a thermosetting resin. An image defect such as a black spot or white spot-like spot defect due to a leak does not occur, and a good image quality can be stably obtained over a long period of time. Further, by setting the thickness of the charge transport layer 1d to 38 μm or less, it is possible to prevent image quality deterioration due to carrier diffusion.

  Next, the charger 20 will be described in detail. The charger 20 is provided to uniformly charge the surface of the photoreceptor 1 with electric power supplied from a power source. As the charger 20, a charger using a minute gap discharge such as a contact roller charger, a non-contact roller charger, a brush charger, or a charger using an injection charging method can be used. A charger of the type that applies only a DC voltage to a charging member such as a charging roller is optimal.

  Hereinafter, an example in which a contact roller charger is used as the charger 20 will be described. FIG. 3 is a cross-sectional view showing the structure of the charger 20 shown in FIG. As shown in FIG. 3, in the charger 20, it is important that the conductive material of the charging roller 2 as a charging member is a mixture of both an electronic conductive material and an ionic conductive material. For this reason, it is not specifically limited to factors, such as the material which forms the charging roller 2, the quantity ratio of the material to be used, the mixed state of the material to be used. The charging roller 2 has an electroconductive support 2a as a base, an elastic layer 2b formed on the outer peripheral surface thereof, and a resistance layer 2c formed on the elastic layer 2b. As described above, the charging roller 2 has a coating layer such as the elastic layer 2b and the resistance layer 2c on the conductive support 2a.

  Further, by using the hybrid charging roller 2, a conventional thermoplastic resin coating can be used without using an expensive photoconductor in which the conductive support 1a of the photoconductor 1 is coated with an alumite treatment or a thermosetting resin. Even when the photosensitive member having a conductive support subjected to the above is used and the maximum particle size of the particles contained in the photosensitive member is 45 μm or less, the occurrence of leakage of the photosensitive member can be prevented, A good image can be obtained.

  As the conductive support 2a, a round bar made of a metal material such as iron, copper, stainless steel, aluminum, or nickel can be used. Furthermore, these metal surfaces may be subjected to a plating treatment in order to provide rust prevention and scratch resistance. However, it is necessary not to impair the conductivity.

  The elastic layer 2b has appropriate conductivity and elasticity in order to supply power to the photosensitive member 1 as a member to be charged and to ensure good uniform adhesion of the charging roller 2 to the photosensitive member 1. In order to ensure uniform adhesion between the charging roller 2 and the photosensitive member 1, the elastic layer 2b is polished so that the central portion is the thickest and becomes thinner from the central portion toward both ends (so-called crown shape). It is preferable to form. Generally, the charging roller 2 is brought into contact with the photoreceptor 1 by applying a predetermined pressing force to both ends of the conductive support 2a. For this reason, the pressing force is small at the central portion and is larger at both end portions. Therefore, there is no problem when the straightness of the charging roller 2 is sufficient, but there is a problem that density unevenness occurs in the images corresponding to the center and both ends when it is not sufficient. In addition, since the charging area has been expanded due to an increase in A3 Nobi compatible models and color machines, the charging roller 2 itself is easily deflected by the pressing force only on both ends of the conductive support 2a. There is a problem that there is a gap. For this reason, the elastic layer 2b is preferably crown-shaped.

The elastic layer 2b is a conductive agent having an electron conduction mechanism such as carbon black, graphite, or a conductive metal oxide in an elastic material such as rubber, and a conductive material having an ion conduction mechanism such as an alkali metal salt or a quaternary ammonium salt. It is formed by adding a suitable agent.
And it is good to adjust so that volume resistance may show the electroconductivity below ¹⁰ < ¹⁰ > ohm-cm. Examples of the elastic material of the elastic layer 2b include natural rubber, ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), silicon rubber, urethane rubber, epichlorohydrin rubber, isoprene rubber (IR), butadiene rubber (BR), Synthetic rubbers such as nitrile butadiene rubber (NBR) and chloroprene rubber (CR), as well as polyamide resin, polyurethane resin, silicon resin and the like can be mentioned.

  The resistance layer 2c is formed in contact with the elastic layer 2b and prevents bleed-out (bleeding) of the softening oil or plasticizer contained in the elastic layer 2b to the surface of the charging roller 2, and the entire charging roller 2 It is provided to adjust the electrical resistance.

  Examples of the material forming the resistance layer 2c include epichlorohydrin rubber, NBR, polyolefin-based thermoplastic elastomer, urethane-based thermoplastic elastomer, polystyrene-based thermoplastic elastomer, fluororubber-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polyamide-based materials. Examples thereof include thermoplastic elastomers, polybutadiene thermoplastic elastomers, ethylene vinyl acetate thermoplastic elastomers, polyvinyl chloride thermoplastic elastomers, and chlorinated polyethylene thermoplastic elastomers. These materials may be used alone, may be a mixture of two or more, or may be a copolymer.

  The resistance layer 2c needs to be conductive or semiconductive. For this reason, a conductive agent (electroconductive carbon, graphite, conductive metal oxide, copper, aluminum, nickel, iron powder, etc.) having an electron conduction mechanism or a conductive agent (alkali metal) having an ionic conduction mechanism is added to the above-described materials. Salt, ammonium salt, etc.) are added as appropriate. In this case, in order to obtain a desired electric resistance, two or more kinds of the above various conductive agents may be used in combination. However, in consideration of environmental fluctuations and contamination of the photoreceptor 1, it is preferable to use a conductive agent having an electronic conduction mechanism.

  A specific example in which the surface roughness Rz (ten-point average roughness, JIS standard B 0601-1982) of the surface of the charging roller 2 is 15 μm or less is shown in Example 9 to be described later. As described above, by setting the surface roughness Rz of the charging roller 2 to 15 μm or less, it is possible to always ensure a stable charging potential and to ensure a level of toner cleaning that is free from problems. Thereby, an image with good initial image quality can be obtained. In particular, when only a DC voltage is applied to the charging roller 2, the convex portion on the surface of the charging roller 2 serves as an appropriate discharge point, and a stable charging potential can always be secured.

  Next, a color printing image forming apparatus to which the present invention is applied will be described with reference to FIG. FIG. 4 is an explanatory view showing the structure of a color printing type (color tandem type) image forming apparatus provided with the contact charging device of the present invention. As shown in FIG. 4, a color printing type image forming apparatus 100 (color machine) forms multicolor and single color images on a predetermined recording sheet (sheet) in accordance with image data input from the outside. To do. As shown in FIG. 4, the apparatus includes a photoreceptor 101, a charger 120, an exposure unit 130, a development unit 140, a fixing unit 160, a cleaning unit 170, a transfer conveyance belt unit 150, and the like. A paper feed tray 180, paper discharge trays 190 and 191 and the like are provided, and a substantially S-shaped paper transport path S is provided between the paper feed tray 180 and the paper discharge tray 190.

  Note that image data handled in the image forming apparatus 100 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, the photosensitive members 101a, 101b, 101c, and 101d for the respective colors of KCMY, the chargers 120a, 120b, 120c, and 120d for the respective colors of KCMY, the exposure units 130a, 130b, 130c, and 130d for the respective colors of KCMY, and the respective colors of KCMY. Four developing units 140a, 140b, 140c, 140d, and four cleaning units 170a, 170b, 170c, and 170d for each color are provided so as to form four types of latent images corresponding to the respective colors. Four image stations (image forming units) for each color are arranged side by side along the sheet conveyance path S.

  The photoconductors 101 a to 101 d for the respective colors are arranged substantially horizontally in a substantially central portion of the image forming apparatus 100. The photoconductors 101a to 101d are formed in the same manner as the photoconductor 1 of the monochrome machine described above.

  Each of the chargers 120a to 120d is provided as a charging unit that uniformly charges the surfaces of the photoreceptors 101a to 101d disposed in contact with or close to the chargers 120a to 120d. The charging members (charging rollers 102a to 102d) of the chargers 120a to 120d are formed in the same manner as the charging member (charging roller 2) of the charger 20 of the monochrome machine described above. As the chargers 120a to 120d, as shown in FIGS. 4 and 5, in addition to a contact roller charger provided with charging rollers 102a to 102d as charging members, a small gap such as a non-contact roller charger, a brush charger, etc. A charger using a discharge or a charger using an injection charging method can be used.

  For each of the exposure units 130a to 130d, for example, a laser scanning unit (LSU) including light emitting elements arranged in an array, for example, an EL or LED writing head, a laser irradiation unit, and a reflection mirror is used. Then, by exposing the photoconductors 101a to 101d charged by the charging member according to the input image data, electrostatic latent images corresponding to the image data are formed on the surfaces of the photoconductors 101a to 101d.

  Each of the developing units 140a to 140d includes a developing roller for supplying toner to the photoconductors 101a to 101d, and the electrostatic latent images formed on the photoconductors 101a to 101d are (K, C, M, Y). Develop with toner to visualize. As a result, toner images corresponding to the image data are formed on the surfaces of the photoreceptors 101a to 101d.

  The transfer / conveying belt unit 150 disposed below the photoreceptors 101a to 101d will be described. The transfer conveyance belt unit 150 includes a transfer belt 155, a transfer belt driving roller 151, a transfer belt tension roller 153, transfer belt driven rollers 152 and 154, transfer rollers 105a, 105b, 105c, and 105d, a transfer belt cleaning unit 157, and the like. Yes.

  The transfer belt drive roller 151, the transfer belt tension roller 153, the transfer rollers 105a to 105d, the transfer belt driven rollers 152 and 154, and the like stretch the transfer belt 155 and rotate the transfer belt 155 in the arrow B direction. is there.

  Each of the transfer rollers 105 a to 105 d is rotatably supported by a transfer roller mounting portion of the housing of the transfer conveyance belt portion 150. Then, a transfer bias is applied to transfer the toner images of the respective photoconductors 101a to 101d onto the recording paper that is attracted onto the transfer belt 155 and conveyed.

  The transfer belt 155 is provided in contact with each of the photoreceptors 101a to 101d. In other words, the photosensitive member 101a and the transfer roller 105a, the photosensitive member 101b and the transfer roller 105b, the photosensitive member 101c and the transfer roller 105c, and the photosensitive member 101d and the transfer roller 105d are arranged to face each other with the transfer belt 155 interposed therebetween. . Then, the color toner images (multicolor toner images) are formed by sequentially superimposing and transferring the toner images of the respective colors formed on the photoconductors 101a to 101d onto the recording paper. The transfer belt 155 is formed endlessly using a film having a thickness of about 100 to 150 μm.

  Transfer of the toner image from each of the photoreceptors 101a to 101d to the recording paper is performed by transfer rollers 105a to 105d that are in contact with the inner side of the endless transfer belt 155. To the transfer rollers 105a to 105d, a high voltage transfer bias (a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner) is applied to transfer the toner image. The transfer rollers 105a to 105d are based on a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm, and a surface thereof is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the recording paper. Although the transfer rollers 105a to 105d are used as the transfer electrodes, a brush or the like may be used.

  Further, the toner adhering to the transfer belt 155 due to contact with the photoreceptors 101a to 101d causes the back surface of the recording paper to be stained. For this reason, the transfer belt cleaning unit 157 removes and collects. The transfer belt cleaning unit 157 is provided with, for example, a cleaning blade 157a as a cleaning member that comes into contact with the transfer belt 155. The cleaning blade 157a is disposed to face the transfer belt driven roller 154 with the transfer belt 155 interposed therebetween. Has been.

  The fixing unit 160 includes a heat roller 161, a pressure roller 162, and the like. The heat roller 161 and the pressure roller 162 are configured to rotate with a recording sheet interposed therebetween. The heat roller 161 is controlled by the control unit 110 to have a predetermined fixing temperature based on a signal from a temperature detector (not shown), and recording is performed by thermocompression of the recording paper together with the pressure roller 162. It has the function of fusing, mixing, and pressing the multicolor toner image transferred to the paper, and thermally fixing the recording paper. After fixing the multicolor toner image, the recording paper is conveyed to the reverse paper discharge path of the paper conveyance path S by the conveyance roller 185, and is discharged in a reversed state (with the multicolor toner image facing downward). It is discharged face down on the paper tray 190.

  The paper feed tray 180 is a tray for storing recording paper used for image formation, and is provided below the four image stations of the image forming apparatus 100. The paper discharge tray 190 is a tray on which image-formed recording paper is placed face down, and is provided on the top of the image forming apparatus 100. On the other hand, the paper discharge tray 191 is a tray for placing image-formed recording paper face up, and is provided on the side of the image forming apparatus 100.

  In order to send recording paper from the paper feed tray 180 to the paper discharge tray 190 via the transfer conveyance belt unit 150 and the fixing unit 160, a substantially S-shaped paper conveyance path S is provided. Along the sheet conveyance path S, a pickup roller 181, a registration roller 182, a fixing unit 160, a conveyance direction switching guide 184, a conveyance roller 185, and the like are arranged.

  The transport roller 185 is a small roller for promoting and assisting the transport of the recording paper, and a plurality of the transport rollers 185 are provided along the paper transport path S. The pickup roller 181 is a drawing roller that is provided at the end of the paper feed tray 180 and that feeds recording paper from the paper feed tray 180 to the paper transport path S one by one.

  Further, the registration roller 182 is provided to temporarily hold the recording paper conveyed through the paper conveyance path S. The recording paper is transported in a timely manner in accordance with the rotation of the photoconductors 101a to 101d so that the toner images on the photoconductors 101a to 101d can be well transferred onto the recording paper. Specifically, the registration roller 182 aligns the leading edge of the toner image on each of the photoconductors 101a to 101d with the leading edge of the image forming range on the recording paper based on a detection signal output from a pre-registration detection switch (not shown). Thus, the recording paper is set to be conveyed.

  The conveyance direction switching guide 184 is rotatably provided on the side cover 186. By rotating the transport direction switching guide 184 from the state indicated by the solid line to the state indicated by the broken line, the recording paper can be separated from the middle of the paper transport path S and discharged onto the paper discharge tray 191. It has become. In the state indicated by the solid line, the recording sheet passes through the conveyance unit S ′ (a part of the sheet conveyance path S) formed between the fixing unit 160, the side cover 186, and the conveyance direction switching guide 184, and passes through the upper part. The paper is discharged to a paper discharge tray 190.

  Even in the color machine configured as described above, the conductive system of the base layer of the charging rollers 102a to 102d is contained in the photoreceptor by adopting a hybrid system that combines two types of electronic conductive material and ion conductive material. Even when the maximum particle diameter is 50 μm, no photoconductor leakage occurs, and a good image can be obtained for a long time. For this reason, it is possible to reduce the cost of manufacturing the photosensitive member.

  In addition, a conductive material coated with a conventional thermoplastic resin can be used without using an expensive photosensitive material obtained by coating an alumite treatment or a thermosetting resin on the conductive supports of the photosensitive members 101a to 101d, which has been conventionally required. Even when a photoconductor having a photosensitive support is used, the occurrence of photoconductor leakage can be prevented and a good image can be obtained.

  Next, an image forming apparatus (an image forming apparatus employing a charging / cleaning system and a developing / cleaning system) to which the present invention is applied and adopts a cleaner-less system will be described. In an image forming apparatus adopting a cleaner-less method, a conventional cleaning device that cleans toner remaining on the photoconductor with a blade or a brush after the transfer is omitted, and the residual toner on the photoconductor is transferred to a developing device or a charger. Since the toner is collected, waste toner can be reduced and the apparatus can be downsized. This image forming apparatus can be applied to both a monochrome machine and a color machine. Below, the example applied to the color machine is demonstrated in detail using FIG. 5, FIG.

  FIG. 5 is an explanatory view showing an image forming apparatus of a color printing method adopting a charging / cleaning method and a developing / cleaning method. FIG. 6 is an explanatory diagram showing the configuration of the photosensitive member and the devices arranged around it in order to form the image of each color in FIG. The image forming apparatus 200 shown in FIG. 5 is provided with a foreign substance disturbing device 280a, 280b, 280c, 280d as a charge adjusting member instead of the cleaning units 170a to 170d. And different. Further, with the provision of the foreign substance disturbing devices 280a to 280d, the configurations of the chargers 220a to 220d and the developing units 240a to 240d are slightly changed from the image forming apparatus 100 shown in FIG. Therefore, the foreign matter disturbing devices 280a to 280d and the chargers 220a to 220d and the developing units 240a to 240d related to the foreign matter disturbing devices 280a to 280d will be described with reference to FIG. . In addition, although the letters a, b, c, and d are attached to the end of the reference numerals corresponding to the respective colors in the chargers of each color in FIG. To represent all colors.

  First, the foreign matter disturbing device 280 as the charge adjusting member shown in FIG. 6 will be described. The foreign matter disturbing device 280 improves the efficiency of attracting foreign matters by the charger 220 (charging roller 202) and the developing unit 240 (developing roller 241) by disturbing (stirring) the aggregates of foreign matters on the photoconductor 101 and loosening them. It is provided for. Here, the foreign matter on the photosensitive member 101 is, for example, toner (residual toner; negative residual toner and positive residual toner) remaining on the photosensitive member 101 without being transferred to the recording paper after the transfer process, Residual foreign matter such as paper dust attached to the surface.

  As shown in FIG. 6, the foreign matter disturbance device 280 includes a conductive brush (toner disturbance member) 281 and a disturbance voltage power source 282. Further, it is disposed downstream of the transfer roller 105 and upstream of the charger 220. The conductive brush 281 is a brush disposed so that the tip thereof is in contact with the surface of the photoconductor 101, and disturbs agglomerates of foreign matters on the photoconductor 101. The disturbance voltage power supply 282 applies a disturbance voltage in which an alternating voltage is superimposed on a direct current having the same polarity (+) as the transfer bias to the conductive brush 281. By such a foreign matter disturbing device 280, the charge of the foreign matter on the photosensitive member 101 is adjusted.

  Specifically, in the image forming apparatus 200, the surface of the photoreceptor 101 negatively charged by the charger 220 is exposed to form an electrostatic latent image, and the charge disappearing portion of the latent image is negatively charged by the developing unit 240. Reversal development is performed to attract the toner that has been absorbed. For this reason, almost all of the toner is negatively charged up to the transfer region (a portion where the photoconductor 101 and the transfer roller 105 face each other). However, when the toner remains on the photoconductor 101 beyond the transfer area, a high voltage transfer bias (for example, +2 kV) is applied in the transfer area, so that the charge amount of the residual toner has a wide distribution. As a positive charge. In other words, the residual toner immediately after exceeding the transfer region is a state in which some negative residual toner (negatively charged residual toner) and a large amount of positive residual toner (positively charged residual toner) are mixed. It has become.

  In the foreign matter disturbing device 280, by applying a positive disturbing voltage to the conductive brush 281, the residual toner is further shifted to the positive charging side to increase the positive residual toner on the photosensitive member 101, and a charging roller described later. The foreign matter adsorption efficiency by 202 is improved. In addition, foreign matter (for example, paper dust) other than toner is positively charged by the DC disturbance voltage in the conductive brush 281. Note that an alternating voltage (alternating voltage) may be applied to the conductive brush 281 by the disturbance voltage power supply 282.

  Next, the charger 220 will be described. In addition to the function of uniformly negatively charging the photoconductor 101, the charger 220 has a function of removing positively charged foreign substances remaining on the photoconductor 101 after the transfer from the photoconductor 101. Have. Here, the positively charged foreign matter includes positive residual toner and positively charged paper powder. That is, the charger 220 is a charging and cleaning device that removes positively charged foreign matter (and its aggregated soul) from the surface of the photoreceptor 101 by adsorbing it on the surface of the charging roller 202.

  The charging roller 202 is pressed against the photoconductor 101 to form a charging nip, and rotates together with the photoconductor 101. However, in order to prevent the toner from being mixed into the charging nip, it may be rotated in the same direction as the rotation direction of the photosensitive member 101 by the driving system.

  The charging roller 202 negatively charges the surface of the photoconductor 101 with a charging bias applied by a charging bias power source (not shown), and electrically charges the positively charged foreign matter remaining on the photoconductor 101. Adsorbs.

  The cleaning member (recovery member) 221 is provided so as to come into contact with the charging roller 202 in order to scrape foreign matter adsorbed on the charging roller 202 and clean the surface of the charging roller 202. As a material of the cleaning member 221, for example, polyethylene terephthalate can be used. The image forming apparatus 200 also has a function of transporting (collecting) foreign matter scraped off by the cleaning member 221 into the developing tank of the developing unit 240, and includes a cleaning blade and a toner transport screw.

  Next, the developing unit 240 will be described. In addition to the function of developing the electrostatic latent image on the photoconductor 101 to form a toner image, the developing unit 240 is a negatively charged foreign substance remaining on the photoconductor 101 after transfer. It has a function of removing and collecting from the photoreceptor 1. Here, the negatively charged foreign matter is, for example, negative residual toner or paper powder. That is, the developing unit 240 is a developing and cleaning device that removes negatively charged foreign matter (and its aggregated soul) from the surface of the photosensitive member 101 by adsorbing it on the surface of the developing roller 241.

  The developing roller 241 supplies toner to the photosensitive member 101 to develop the electrostatic latent image in a developing region (a portion where the photosensitive member 101 and the developing roller 241 face each other), while developing the electrostatic latent image on the photosensitive member 101 upstream of the developing region. The remaining negatively charged foreign matter is electrostatically removed. Note that negatively charged foreign matter (particularly negative residual toner) adsorbed on the developing roller 241 is scraped off by the toner supply roller 242 provided behind the developing roller 241 as the developing roller 241 rotates. And sufficiently charged by stirring.

  FIG. 7 is an explanatory diagram showing an example of a configuration in which the charging / cleaning method and the developing / cleaning method are applied to a monochrome machine. The configuration example shown in FIG. 7 differs from the image forming apparatus of FIG. 5 in that the development portion is a two-component development system, but there is no significant difference in other configurations.

  In an image forming apparatus that employs a cleanerless system that employs a development and cleaning system (and a charging and cleaning system), a hybrid that combines two types of electroconductive material and ion conductive material as the base layer of the charging roller. By adopting this method, even when the maximum diameter of the particles contained in the photosensitive member is 45 μm, a good image can be obtained for a long period without causing leakage of the photosensitive member. For this reason, it is possible to reduce the cost of manufacturing the photosensitive member.

In addition, a conductive support that has been coated with a conventional thermoplastic resin without using an expensive photoconductor in which an alumite treatment or a thermosetting resin is coated on the conductive support of a photosensitive member that was conventionally required. Even when a photoconductor having the above is used, the occurrence of photoconductor leakage can be prevented and a good image can be obtained.
Further, by arranging the conductive brush 281 downstream of the transfer roller 105 and upstream of the charger 220, that is, between the transfer region and the charging nip, the toner disturbance effect can be ensured. And stable image quality can be obtained over a long period of time.

(Example)
Hereinafter, Examples 1 to 9 of the present invention and Comparative Examples 1 to 5 with the conventional ones will be shown. Preparation of charging member, preparation of photoreceptor, confirmation of leakage of photoreceptor, surface roughness of charging member The results of the measurement, image quality confirmation test, etc. are shown.

Example 1
<Production of charging member>
An ionic material and carbon are dispersed on a Φ9 conductive support to form a semiconductive NBR layer, and a carbon is dispersed on the semiconductive NBR layer to form a Φ14 charging member. It was created. The composition of the material is described below.
-Elastic layer-
NBR 100 parts by weight Ester plasticizer 25 parts by weight Carbon black 45 parts by weight Quaternary ammonium salt 1 part by weight Calcium carbonate 25 parts by weight Zinc oxide 1 part by weight Stearic acid 1 part by weight Dibenzothiazole disulfide 1 part by weight Tetramethylthiuram monosulfide 1 part by weight Sulfur 1 part by weight -surface layer-
NBR latex 50 parts by weight SBR latex 50 parts by weight Sulfur-based vulcanizing agent 5 parts by weight Carbon black 5 parts by weight

<Surface roughness measurement>
The 10-point average roughness (Rz) of the charging roller was measured using a surface roughness meter (Kosaka Lab: SE-30H). In the case of the above charging roller, it was 6.5 μm.

<Measurement of dynamic resistance>
The dynamic resistance of the charging member (charging roller) was measured in an environment at a temperature of 25 ° C. and a humidity of 50%. FIG. 8 is an explanatory diagram for explaining a state when the dynamic resistance of the charging roller is measured. The measurement procedure was as follows. First, the charging member 302 and the photoreceptor 303 were pressed against each other under actual conditions. Then, the photosensitive member was rotated and moved under actual conditions, and the charging member was rotated, fixed, and moved under actual conditions. In order to charge the photosensitive member to an actual charging potential (in this experiment, −620 V), a voltage Va was applied to the charging member using the power source 301. Under this condition, the current value Ia (μA) flowing into the photosensitive member was measured with an ammeter 304.
Next, instead of the photoconductor, a conductive cylindrical electrode (made of stainless steel) having the same shape as the photoconductor was inserted. Except that the photosensitive member was replaced with a drum-shaped cylindrical electrode, the pressing force (10.3 gf / cm) to the cylindrical electrode of the charging roller was all applied in the same manner as in the above experiment, and a voltage was applied from an external power source. The same Ia (μA) as the current flowing into the photosensitive member was passed through the cylindrical electrode, and the resistance value was calculated from the voltage value applied at this time. This value was defined as the dynamic resistance R (Ω) of the charging member. The charging roller had a dynamic resistance R of 2.74 × 10 ⁶ (Ω).

<Measurement of water contact angle of charging member>
The water contact angle of the charging roller was measured using a water contact angle meter (Kyowa Interface Chemistry: CA-VP).
The water contact angle of the charging roller was 94 °.

<Dynamic friction coefficient measurement>
A dynamic friction coefficient was measured when a tape material having a width of 10 mm produced by applying the surface material of the photosensitive drum to the surface of the charging roller 1 was applied to a PET sheet and moved by applying a load of 100 g. A surface property measuring machine (Shinto Kagaku: HEIDON-14D) was used as the measuring equipment. As a result, the dynamic friction coefficient of the charging roller was 0.4.

Example 2
An ionic material and carbon are dispersed on a Φ9 conductive support to form a semi-conductive epichlorohydrin layer, and a carbon rubber is dispersed thereon to form a semi-conductive fluororubber layer. A member was created. The same measurement as in Example 1 was performed except that the charging roller was mixed as follows.
-Elastic layer-
Epichlorohydrin rubber 100 parts by weight Ether ester plasticizer 15 parts by weight Carbon black 10 parts by weight Quaternary ammonium salt 1 part by weight Calcium carbonate 30 parts by weight Zinc oxide 5 parts by weight Fatty acid 2 parts by weight Di-2-benzothiazolyl disulfide 1 Parts by weight tetramethylthiuram monosulfide 0.5 parts by weight sulfur 1 part by weight -surface layer-
Fluoro rubber 100 parts by weight Fluorinated carbon 20 parts by weight Amine-based curing agent 2.5 parts by weight

<Surface roughness measurement>
Rz of the charging roller was 2.5 μm.
<Measurement of dynamic resistance>
The charging roller had a dynamic resistance R of 9.72 × 10 ⁵ (Ω).
<Measurement of water contact angle of charging member>
The water contact angle of the charging roller was 127 °.
<Dynamic friction coefficient measurement>
The charging roller had a dynamic friction coefficient of 1.0.

(Comparative Example 1)
An EPDM layer made semi-conductive by dispersing carbon on a conductive support of Φ9 is formed, and a nylon 12 tube made semi-conductive by dispersing carbon is placed on the EPDM layer, thereby creating a charging member of Φ14 did. The same measurement as in Example 1 was performed except that the charging roller was mixed as follows.
-Elastic layer-
EPDM 100 parts by weight Carbon black 25 parts by weight Molecular end modified wax 5 parts by weight Dicumyl peroxide 25 parts by weight Ethylene glycol dimethacrylate 2 parts by weight -Surface layer-
Nylon 12 100 parts by weight Carbon black 20 parts by weight

<Surface roughness measurement>
Rz of the charging roller was 0.5 μm.
<Measurement of dynamic resistance>
The charging roller had a dynamic resistance R of 1.97 × 10 ⁶ (Ω).
<Measurement of water contact angle of charging member>
The water contact angle of the charging roller was 88 °.
<Dynamic friction coefficient measurement>
The charging roller had a dynamic friction coefficient of 0.21.

(Comparative Example 2)
Forming a semi-conductive silicon rubber layer by dispersing carbon on a Φ9 conductive support, and covering it with a semi-conductive vinylidene fluoride tube, Φ14 charging member It was created. The same measurement as in Example 1 was performed except that the charging roller was mixed as follows.
-Elastic layer-
Silicon rubber 100 parts by weight Carbon black 7 parts by weight Vulcanizing agent 2 parts by weight -Surface layer-
Vinylidene fluoride resin 100 parts by weight Polyurethane resin 5 parts by weight Carbon black 10 parts by weight

<Surface roughness measurement>
Rz of the charging roller was 4.5 μm.
<Measurement of dynamic resistance>
The charging roller had a dynamic resistance R of 5.71 × 10 ⁵ (Ω).
<Measurement of water contact angle of charging member>
The water contact angle of the charging roller was 109 °.
<Dynamic friction coefficient measurement>
The charging roller had a dynamic friction coefficient of 0.8.

(Comparative Example 3)
An ionic conductive epichlorohydrin rubber layer was formed on a Φ9 conductive support, and an ionic conductive epichlorohydrin rubber layer containing fluorine was formed thereon to form a Φ14 charging member. The same measurement as in Example 1 was performed except that the charging roller was mixed as follows.
-Elastic layer-
Epichlorohydrin rubber 100 parts by weight Quaternary ammonium salt 2 parts by weight Calcium carbonate 30 parts by weight Zinc oxide 5 parts by weight Fatty acid 5 parts by weight Ether ester plasticizer 15 parts by weight Sulfur 1 part by weight Di-2-benzothiazolyl disulfide 1 part by weight Tetramethylthiuram monosulfide 0.5 parts by weight -surface layer-
Epichlorohydrin rubber solution 100 parts by weight Solvent-soluble fluororesin solution 40 parts by weight

<Surface roughness measurement>
Rz of the charging roller was 11.5 μm.
<Measurement of dynamic resistance>
The charging roller had a dynamic resistance R of 3.76 × 10 ⁶ (Ω).
<Measurement of water contact angle of charging member>
The water contact angle of the charging roller was 100 °.
<Dynamic friction coefficient measurement>
The charging roller had a dynamic friction coefficient of 0.33.

  The materials and characteristics measurement results of the charging members used in Examples 1 and 2 and Comparative Examples 1 to 3 are summarized in a table. Table 1 shows the material of each charging part of Examples 1 and 2 and Comparative Examples 1 to 3. Table 2 shows the characteristic measurement results of the charging members of Examples 1 and 2 and Comparative Examples 1 to 3.

Example 3
<Production of photoconductor>
The photoreceptor is produced by sequentially forming an undercoat layer, a charge generation layer, and a charge transport layer on an aluminum cylindrical conductive support adjusted to a diameter of 30 mm, a total length of 362 mm, and a surface roughness Rmax of 1.0 μm. To do.

  7 parts by weight of titanium oxide (manufactured by Ishihara Sangyo Co., Ltd .: TT055A), 13 parts by weight of copolymer nylon (manufactured by Toray Industries, Inc .: CM8000), 159 parts by weight of methyl alcohol, and 106 parts by weight of 1,3-dioxolane In addition to the mixed solvent, an undercoat layer coating solution was prepared by dispersing for 8 hours using a paint shaker. The coating liquid for the undercoat layer was filled in a coating tank, and the conductive support was dipped in the coating tank and pulled up, followed by natural drying to form an undercoat layer having a thickness of 1 μm.

  In the X-ray diffraction spectrum, 1 part by weight of crystalline oxotitanyl phthalocyanine showing a diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° and a butyral resin (manufactured by Denki Kagaku Kogyo Co., Ltd .: # 6000-C) 1 part by weight was mixed with 98 parts by weight of methyl ethyl ketone and dispersed with a paint shaker to prepare a charge generation layer coating solution. The charge generation layer coating solution was filtered through various filters to control the maximum particle size in the photoreceptor. Thereafter, the charge generation layer having a thickness of 0.4 μm was formed by coating on the undercoat layer and natural drying.

Subsequently, 100 parts by weight of a butadiene compound (manufactured by Takasago Chemical Co., Ltd .: T405), 150 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd .: Z300), and 2,6-bis-tert-butyl as an additive. -4-methylphenol (Sumitomo Chemical Co., Ltd .: Sumilizer BHT) 5 parts by weight was mixed to prepare a charge transport layer coating solution having a solid content of 21% by weight using tetrahydrofuran as a solvent. The charge transport layer coating solution was applied onto the charge generation layer and dried at 110 ° C. for 1 hour to form a charge transport layer having a thickness of 21 μm.
The filter for filtering the coating solution was changed, and the six photosensitive members prepared by controlling the particle size contained in the photosensitive member with various filters were observed with an optical microscope, and the maximum particle size contained was measured. It was. Moreover, as shown in Table 3, it was set as Examples 3-6 and Comparative Examples 4 and 5 according to the magnitude | size of the largest particle diameter to contain. That is, in Example 3, the maximum particle diameter contained in the photosensitive layer was 0.8 μm, whereas in Examples 4, 5, and 6, the maximum particle diameter contained in the photosensitive layer was 2.0 μm, 15 0.0 μm and 45.0 μm. In Comparative Examples 4 and 5, the maximum particle size contained in the photosensitive layer is 55.0 μm and 97.0 μm, respectively. Table 3 shows the results of confirmation of photoconductor leakage and image quality evaluation using these photoconductors.

<Photoconductor leak, image quality check>
As the image forming apparatus 100 using the photosensitive member 101 and the charging roller 102 shown in FIG. 4, the charging roller of Example 1 and the photosensitive members of Examples 3 to 6 and Comparative Examples 4 and 5 manufactured as described above are formed as an image. Using a device (manufactured by Sharp Corporation: AR-C260), a photoreceptor leak confirmation test was performed. The test was performed under the basic conditions of AR-C260 except for the following process conditions such as bias. The pressing force of the charging roller 302 to the photosensitive member 301 was set to a linear pressure of 10.3 gf / cm, and the charging roller 302 was rotated around the photosensitive member 301. A DC voltage of -1220V was applied to the shaft portion of the charging roller 302 from the outside using a high voltage power source with a rise time of 0.1 msec, and the surface potential of the photoreceptor 301 was set to -620V.

Table 3 shows the evaluation results of the photoreceptor leak and image quality after 30000 copies of A3 size originals in such an image forming apparatus. When the maximum diameter of the particles contained in the photoreceptor is 0.8 to 45.0 μm, no leakage of the photoreceptor or image defects due to the particles could be visually confirmed even after copying 30000 sheets of A3 size. On the other hand, when the maximum diameter of the particles contained in the photoreceptor is 55.0 μm or more, a leak occurred before 30000 copies. In the case of 97.0 μm particles, visual image defects were confirmed.
From the confirmation results in the above-described examples, the maximum particle size of the particles contained in the photosensitive layer is in the range of more than 1 micrometer and 45 micrometers or less, which is too large in the prior art and may cause the photoreceptor leakage. Layer leakage can be avoided and good image quality can be obtained. In consideration of a sufficient margin, the range is more preferably greater than 1 micrometer and not greater than 15 micrometers.

Example 7
The effect of the surface roughness Rmax of the conductive support on the photoreceptor leakage and image quality was examined.
A photoconductor having the same production method as in Example 3 was used, except that a cylindrical conductive support made of aluminum was adjusted to a diameter of 30 mm, a total length of 323 mm, and a surface roughness of Rmax 0.2 to 3.0 μm. This time, the maximum particle size contained in the photoreceptor was 20 to 40 μm. Thereafter, the charge generation layer having a thickness of 0.4 μm was formed by coating on the undercoat layer and natural drying.

  As the image forming apparatus 10 using the photosensitive member 1 and the charging roller 2 shown in FIG. 1, the charging roller of Example 1 and the photosensitive members of Examples 3 to 6 and Comparative Examples 4 and 5 manufactured as described above were used. A photoreceptor leak confirmation test was performed using an image forming apparatus (manufactured by Sharp Corporation: DM2515). The test was performed under the basic conditions of AR-C260 except for the following process conditions such as bias. The pressing force of the charging roller 2 to the photoreceptor 1 was set to a linear pressure of 10.3 gf / cm, and the charging roller 2 was rotated around the photoreceptor 1. A DC voltage of −1180 V was applied to the shaft portion of the charging roller 2 from the outside using a high voltage power source with a rise time of 0.1 msec, and the surface potential of the photoreceptor 1 was set to −600 V.

  Table 4 shows the evaluation results of the photoreceptor leak and image quality after copying 30000 A3-size originals in such an image forming apparatus.

When the surface roughness Rmax of the conductive support of the photosensitive member was 0.5 to 2.0 μm, no leak occurred and no image defect was observed. On the other hand, when Rmax was 0.2 μm, a striped pattern was observed. In addition, when Rmax was 3.0 μm, a leak occurred before copying 30000 sheets.
From the confirmation results in the above examples, it is preferable that the surface roughness of the conductive support that can avoid photoconductor leakage and is not affected by interference fringes is in the range of 0.5 to 2.0 micrometers. Considering a sufficient margin, a more preferable range for avoiding the photoreceptor leakage is a range of 0.5 to 1.0 micrometers. On the other hand, considering the influence of interference fringes, the most preferable value is 1.0 micrometers.

Example 8
The effect of photoreceptor leakage on the charge transport layer thickness of the photoreceptor was examined.
The charging member used in Example 1 was used, and five types of photoreceptors were prepared by changing the film thickness of the charge transport layer by the same manufacturing method as in Example 3. This time, the maximum particle size contained in the photoreceptor was 20 to 40 μm.

The image forming apparatus used was a modified machine manufactured by Sharp Corporation: AR-C260. The pressing force of the charging roller 302 to the photosensitive member 301 was set to a linear pressure of 10.3 gf / cm, and the charging roller 302 was rotated around the photosensitive member 301. A DC voltage of -1220V was applied to the shaft portion of the charging roller 302 from the outside using a high voltage power source with a rise time of 1.1 msec, and the surface potential of the photoreceptor 301 was set to -620V.
The test was performed under the basic conditions of AR-C260 except for the process conditions such as the bias described above.

  In the above image forming apparatus, a photoreceptor leak confirmation test was performed after 30000 copies of A3 size originals were copied. The results are shown in Table 5.

No photoconductor leakage occurred when the charge transport layer thickness was 21 to 38 μm. However, when a photosensitive drum having a film thickness of 15 μm was used, a leak occurred when the film thickness decreased to 12 μm.
From the confirmation results in the above examples, the thickness of the charge transport layer that can avoid the photoreceptor leakage and obtain good image quality is 15 to 38 micrometers. Considering a sufficient margin from the viewpoint of avoiding photoconductor leakage, a more preferable range is 15 to 21 micrometers. Further, considering the image quality, the most preferable value is 15 micrometers.

Example 9
The influence on the image quality with respect to the surface roughness Rz of the charging member was examined.
The charging member was produced by the same manufacturing method as in Example 1, and Rz was adjusted by adjusting the particle size and the like of the conductive filler added to the surface layer.
The photoreceptor used in Example 5 was used.

  The image forming apparatus used was a modified machine manufactured by Sharp Corporation: AR-C260. The pressing force of the charging roller 102 to the photosensitive member 101 was set to a linear pressure of 10.3 gf / cm, and the charging roller 102 was rotated around the photosensitive member 101. A DC voltage of -1220V was applied to the shaft portion of the charging roller 102 from the outside using a high voltage power source with a rise time of 30 msec, and the surface potential of the photosensitive member 101 was set to -620V.

  In such an image forming apparatus, a photoreceptor leak confirmation test was performed after 30000 copies of A3 size originals were copied. The results are shown in Table 6.

When the surface roughness Rz was 0.5 to 14.5 μm, there was no defective charging and a good image was obtained. When the surface roughness Rz is 17.3 μm or more, defective charging partially appears in the image, which is a problem.
From the confirmation results in the above examples, the range of the surface roughness Rz in which good image quality is obtained by uniform charging is 0.5 to 14.5 micrometers. Considering a sufficient margin, a more preferable range is 0.5 to 11.0 micrometers.

Example 10
The effect of photoconductor leakage on the rise time of the power supply was examined.
The charging member used was that described in Examples 1-2 and Comparative Examples 1-3, and the photoreceptor used in Example 5 was used.

  As the image forming apparatus 100 using the photosensitive member 101 and the charging roller 102 shown in FIG. 4, the charging roller of Example 1 and the photosensitive members of Examples 3 to 6 and Comparative Examples 4 and 5 manufactured as described above were used. A photoreceptor leak confirmation test was performed using an image forming apparatus (manufactured by Sharp Corporation: AR-C260). The test was performed under the basic conditions of AR-C260 except for the following process conditions such as bias. The pressing force of the charging roller 102 to the photosensitive member 101 was set to a linear pressure of 10.3 gf / cm, and the charging roller 102 was rotated around the photosensitive member 101. A DC voltage of -1220V was applied to the shaft portion of the charging roller 102, and the surface potential of the photoreceptor 101 was set to -620V. At this time, six types of high-voltage power supplies having a rise time of 0.002 msec to 90 msec were used.

  In such an image forming apparatus, the leakage of the photosensitive member after 30000 copies of A3 size originals was evaluated. The results are shown in Table 7.

* Photoconductor leak did not occur, but there was an image defect that appeared to be the transfer of roller material in the photoconductor cycle.
From the confirmation results in the above examples, the preferable range of the rise time that can avoid the photoreceptor leak is 0.02 to 90 milliseconds. In view of a sufficient margin, a more preferable range is 0.02 to 50 milliseconds.

Example 11
We examined photoconductor leakage in a cleanerless system.
The charging member used in Example 1 and Comparative Example 2 was used, and the photoreceptor used in Example 5 was used.

The image forming apparatus used was a modified machine manufactured by Sharp Corporation: AR-C260. Using a high voltage power supply with a rise time of 30 msec from the outside to the shaft portion of the charging roller 102, a DC voltage of -1220V is applied, the surface potential of the photosensitive member 101 is set to -620V, and the toner is used to disturb the toner instead of the cleaning blade. A characteristic brush was installed, and a bias of DC bias: +500 V, amplitude: 1 kV, frequency: 250 Hz was applied to the disturbance brush. The test was performed under the basic conditions of AR-C260 except for the process conditions such as the bias described above.
In such an image forming apparatus, a photoreceptor leak confirmation test was performed after 30000 copies of A3 size originals were copied. The results are shown in Table 8.

  In a system using a hybrid roller as a charging member, no photoconductor leakage occurred, and a good image was obtained over a long period of time. A photoconductor leak occurred in the electronically conductive roller.

It is explanatory drawing which shows the one aspect | mode of implementation of the contact charging device of this invention. FIG. 2 is a cross-sectional view showing a layer configuration of the photoreceptor 1 shown in FIG. 1. It is sectional drawing which shows the structure of the charger 20 shown in FIG. It is explanatory drawing which shows the structure of the image forming apparatus of a color printing system provided with the contact charging device of this invention. It is an explanatory view showing an image forming apparatus of a color printing method adopting a charging and cleaning method and a developing and cleaning method. FIG. 6 is an explanatory diagram illustrating a configuration of a photosensitive member and each device disposed in the periphery thereof to form an image of each color in FIG. 5. It is explanatory drawing which shows an example of the structure which applied the above-mentioned charging and cleaning system and developing and cleaning system to a monochrome machine. It is explanatory drawing for demonstrating a mode when the dynamic resistance of a charging roller is measured.

Explanation of symbols

1, 101, 101a, 101b, 101c, 101d Photoconductor 1a Conductive support 1b Undercoat layer 1c Charge generation layer 1d Charge transport layer 1e Photosensitive receiving layer 2, 102a, 102b, 102c, 102d, 202 Charge roller 2a Conductivity Support 2b Elastic layer 2c Resistive layer 4, 241 Developing roller 20, 20a, 120, 120a, 120b, 120c, 120d, 220, 220a, 220b, 220c, 220d Charger 21, 221 Cleaning member, recovery member 30, 130, 130a, 130b, 130c, 130d Exposure unit 40, 140, 140a, 140b, 140c, 140d, 240, 240a, 240b, 240c, 240d Development unit 50 Transfer unit 60, 160 Fixing unit 70, 170, 170a, 170b, 170c, 170d chestnut Ninging part 80 Charger power supply 81, 281 Conductive brush, toner disturbing member 82, 282 Disturbing voltage power supply 100, 200 Image forming apparatus 105, 105a, 105b, 105c, 105d Transfer roller 150 Transfer conveying belt part 151 Transfer belt driving roller 152 , 154 Transfer belt driven roller 153 Transfer belt tension roller 155 Transfer belt 157 Transfer belt cleaning unit 157a Cleaning blade 160 Fixing unit 161 Heat roller 162 Pressure roller 180 Paper feed tray 181 Pickup roller 182 Registration roller 184 Transport direction switching guide 185 Transport roller 186 Side cover 190, 191 Discharge tray 242 Toner supply roller 280, 280a, 280b, 280c, 280d Foreign matter disturbance device 300 Dynamic resistance of charging roller Constant 301 power 302 charging member 303 photoconductor 304 ammeter

Claims (14)

A photoreceptor formed by forming a photosensitive layer on the surface of the conductive support or on the undercoat layer formed on the surface of the conductive support;
A charging roller having a conductive elastic layer disposed between the shaft and the surface, the surface being arranged to rotate while contacting the photosensitive layer;
A charging power source for applying a DC charging voltage between the conductive support of the photosensitive member and the shaft portion of the charging roller;
Since the conductive elastic layer has conductivity by dispersing the electronic conductive material and the ion conductive material in the elastic material, a current flowing between the charging roller and the photosensitive layer is locally generated by the charging voltage. A contact charging device for an electrophotographic process, having a conductivity that does not cause dielectric breakdown of the photosensitive layer when concentrated on the photosensitive layer.   The contact charging device according to claim 1, wherein the electronic conductive material contained in the conductive elastic layer of the charging roller is made of carbon black, graphite, or a conductive metal oxide.   The contact charging device according to claim 1, wherein the ion conductive material contained in the conductive elastic layer of the charging roller is made of an alkali metal salt or a quaternary ammonium salt.   2. The contact charging device according to claim 1, wherein the photosensitive layer is a layer containing particles having a maximum diameter of more than 1 micrometer and not more than 45 micrometers.   The contact charging device according to claim 1, wherein the conductive support has a surface roughness of 0.5 to 2.0 μm on a surface on which the photosensitive layer is formed.   2. The contact charging device according to claim 1, wherein the photosensitive layer comprises a charge generation layer formed on a conductive support and a charge transport layer having a thickness of 15 to 38 micrometers formed on the charge generation layer.   The contact charging device according to claim 1, wherein the conductive support is formed by applying a thermoplastic resin to an aluminum surface.   The contact charging device according to claim 1, wherein the charging roller has a surface roughness of 0.5 to 14.5 micrometers on a surface in contact with the photosensitive layer.   2. The contact charging device according to claim 1, wherein the charging power source has a rise time of 0.02 to 90 milliseconds from the start of applying the charging voltage until the charging roller shaft voltage reaches the target voltage.   An electrophotographic image forming apparatus comprising the contact charging device according to claim 1. A plurality of photoreceptors for forming images of different colors in order to form a color image;
The image forming apparatus according to claim 10, further comprising the contact charging device disposed corresponding to each photoconductor for charging the photoconductor. A developing unit having a function of cleaning the photosensitive member by adsorbing charged particles on the surface of the photosensitive member to the developing unit;
An electrophotographic image forming apparatus comprising the contact charging device according to claim 1.   The image forming apparatus according to claim 12, further comprising a charging roller cleaning unit that cleans a surface of the charging roller, so that the contact charging device has a photosensitive member cleaning function. A toner disturbing member for disturbing toner remaining on the surface of the photoreceptor after the transfer is disposed in front of the contact charging device;
14. The image forming apparatus according to claim 12, wherein the residual toner is configured to pass through the contact charging device after being disturbed by the toner disturbing member.

Images