JPH0850394A - Charged member, charging device, image forming device and process cartridge - Google Patents

Abstract

PURPOSE:To improve uniformity and long-term stability of charge on the surface of a body to be charged by incorporating magnetic conductive particles into a brush part. CONSTITUTION:The charged brush 20 has a brush part 23 made of semiconductive fibers in which magnetic conductive particles (magnetic carrier) 24 are incorporated. A photosensitive drum 1 is charged by applying voltage on the brush part and rubbing the drum with the brush. The magnetic conductive particles 24 used have <=30mum particle size and 10<4> to 10<8>OMEGA resistance. As the magnetic conductive particles, such particles prepared by kneading a resin with a magnetic powder such as magnetite, ferrite and cobalt to be formed into particles, or further mixing conductive carbon, etc., to the particles to control the resistance are used, or particles of sintered magnetite or ferrite, or particles prepared by reducing these particles to control the resistance are used. Further, magnetic particles prepared by plating the above mentioned particles to obtain proper resistance are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member, a charging device,
The present invention relates to an image forming apparatus and a process cartridge.

More specifically, a. At least the conductive fine particles are dispersed in the outermost layer, the brush portion (brush bristles, brush fiber portion, pile portion) is brought into contact with the charged body to apply a voltage to charge and charge the charged body. A brush-type contact charging member, b. A contact type charging device using this brush type charging member, c. An image forming apparatus using this charging device as a charging means for the image carrier, d. The present invention relates to a process cartridge which includes at least an image carrier and at least a charging member of the charging device for charging the image carrier and which is attached to and detached from an image forming apparatus main body.

[0003]

2. Description of the Related Art Conventionally, for example, in an image forming apparatus (copying machine, printer, etc.) such as an electrophotographic apparatus, an electrostatic recording apparatus, etc., an image bearing member such as a photosensitive member, a dielectric member, etc. A non-contact type corona charger has been widely used as a means / apparatus for performing a charging process (including a charge removing process).

In recent years, instead of this, a contact type charging device (contact charging device) has been put into practical use. This is to charge the surface of the charged object by bringing a charging member (conductive member) such as a roll type or a blade type into contact with the charged object and applying a voltage.
Features such as low power consumption (low voltage).

In particular, a roller charging method using a conductive roller (charging roller) as the contact charging member is preferably used from the viewpoint of charging stability. In roller charging, a conductive elastic roller as a charging member is pressed against and contacted with a body to be charged, and a voltage is applied to the body to charge the body to be charged.

In this contact charging device, charging is mainly performed by discharging from the contact charging member to the member to be charged, and therefore charging is started by applying a voltage equal to or higher than a certain threshold (threshold) voltage. It As an example, in an electrophotographic apparatus, when a charging roller is pressed against an OPC photosensitive member having a thickness of 25 μm, which is a member to be charged, and a voltage is applied to perform a charging process, the charging roller is About 640
When a voltage of V or more is applied, the surface potential of the photoconductor starts to rise, and thereafter, the surface potential of the photoconductor linearly increases with a slope of 1 with respect to the applied voltage. Hereinafter, this threshold voltage is defined as the charging start voltage Vth.

That is, in order to obtain a desired photoreceptor surface potential Vd required for electrophotography, Vd is applied to the charging roller.
A DC voltage higher than the required Vd of + Vth is required. The method of charging by applying only the DC voltage to the contact charging member in this way is hereinafter referred to as "DC charging method".

However, in the DC charging method, the resistance value of the contact charging member fluctuates due to environmental fluctuations, etc. Further, when the photoconductor as the member to be charged is scraped and the film thickness changes, Vth fluctuates. It was difficult to set the body potential to a desired value.

Therefore, in order to further homogenize the charging, as disclosed in Japanese Patent Laid-Open No. 63-149669, the DC voltage corresponding to the desired photoreceptor surface potential Vd is set to 2V.
An “AC charging method” is used in which an oscillating voltage in which an AC component having a peak-to-peak voltage of × Vth or more is superimposed is applied to the contact charging member. This is for the purpose of leveling out the potential due to the AC component, and the potential of the charged body converges on the photoreceptor surface potential Vd which is the center of the peak of the AC voltage, and is affected by disturbances such as the environment. There is no such thing.

However, even in the contact charging device of the DC charging type or the AC charging type as described above, the essential charging mechanism uses the phenomenon of discharging from the charging member to the member to be charged. As described above, the voltage required for charging needs to have a value equal to or higher than the desired surface potential Vd of the body to be charged, and a slight amount of ozone is generated. Further, when the AC charging method is used for uniform charging, a further amount of ozone is generated, vibration noise (referred to as AC charging sound) between the charging member and the body to be charged due to the electric field of the AC voltage is generated, Deterioration of the surface of the photosensitive member as a member to be charged due to discharge has become remarkable, which has become a new problem.

For this reason, there has been a demand for charging by directly injecting charges into a member to be charged such as a photoconductor. Conventionally, there is also a method in which a high voltage is applied to a contact conductive member such as a charging roller or a charging brush to inject charge into a trap level or the like on the surface of the photoconductor to perform contact injection charging, but the injection efficiency is poor. The current situation is that it has not been put to practical use.

Further, Japanese Patent Laid-Open No. 6-3921 discloses a charging system (charge injection charging system) by directly injecting charges into a body to be charged. In this charging method, a contact conductive member (contact charging member, injection charging member) such as a charging roller, a charging brush, or a charging magnetic brush is brought into contact with a photosensitive member as a member to be charged having a charge injection layer on its surface to apply a voltage. Is applied to inject charges into the conductive particles (float electrodes) of the charge injection layer on the photoconductor to perform contact injection charging.
Specifically, the charge injection layer is made of an acrylic resin on the surface of which S is made conductive by antimony doping which is a conductive filler.
It is possible to coat and use a dispersion of nO ₂ particles.

In this charge injection charging method, since the discharge phenomenon is not used, the voltage required for charging is a DC voltage of only the desired photoreceptor surface potential Vd, and ozone is not generated. Further, since no AC charging voltage is applied, no AC charging sound is generated, and the charging method is lower in ozone (ozone less) and lower in electric power than the roller charging method.

FIG. 6 shows an example of a charge injection charging type charging device using a magnetic brush type charging member. (A) is a cross-sectional model view, (b) is a vertical cross-sectional model view of one end side of the charging member.

Reference numeral 100 denotes a member to be charged, which is, for example, a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a drum) as an image bearing member of an electrophotographic apparatus. This drum 100
It is composed of a conductive drum substrate 100a and a photoconductor layer 100b formed on the outer peripheral surface thereof. The photoconductor layer 100b has a charge injection layer on the surface thereof, and has a predetermined peripheral speed (process speed) in the clockwise direction indicated by the arrow. Is driven to rotate.

Reference numeral 200 denotes a magnetic brush type contact charging member 20.
1 is a charging device. The charging member 201 includes a magnet roller 202 as a magnetic force generating member, a non-magnetic electrode sleeve 203 as a power feeding portion for a magnetic brush, which is fitted to the outside of the magnet roller 202 concentrically and rotatably on the roller, and the electrode sleeve 203. Inner magnet roller 2 on the outer peripheral surface
The magnetic brush 204 is composed of magnetic particles (hereinafter, referred to as carriers) that are attracted by the magnetic force of 02 to be retained.

The charging member 201 is arranged substantially in parallel with the drum 100 as a member to be charged, and the magnetic brush 204 is brought into contact with the surface of the drum 100 so that the shaft 2 of the magnet roller 202 is provided.
02a is supported by a bearing (not shown). The magnet roller 202 is non-rotatably fixed and held, and the non-magnetic electrode sleeve 203 is rotationally driven in the clockwise direction indicated by the arrow at a predetermined peripheral speed by a driving unit (not shown). That is, the magnetic brush 204 rotates with the rotation of the electrode sleeve 203 while keeping contact with the surface of the drum 100. N is a magnetic brush 2
04 is a contact nip portion between the drum 100 and the drum 100 (hereinafter, referred to as a charging nip portion). S1 is a power supply for applying a charging bias to the electrode sleeve 203 as a power feeding portion to the magnetic brush 204.

Thus, the drum 100 and the electrode sleeve 2
03 is rotationally driven, and the electrode sleeve 2 is connected from the power source S1.
03, a charge bias of a predetermined polarity and potential is applied to the conductive particles of the charge injection layer on the surface of the photoconductor layer 100b of the drum 100 by the magnetic brush 204, and the photoconductor of the drum 100 is charged. The surface of the layer 100b is charged with a predetermined polarity and potential by a charge injection charging method.

[0019]

However, in the case of the above magnetic brush charging using the magnetic brush type charging member 201 as the contact charging member, the carrier at the longitudinal end of the magnetic brush 204 and the magnetic brush 204 are to be charged. In the charging nip portion N which is the abutting portion of the drum 100 as a body, it is pushed in the direction of arrow A to the longitudinal outside region D ((b) of FIG. 6) which is a non-charging region. In this region D, since the magnetic brush is not in constant contact with the drum, the drum surface is not uniformly charged, and the surface potential of the drum is considerably lower than the charging potential. However, the magnetic brush 2
Since a voltage corresponding to the charging potential (eg, -700 V) is applied to 04, a potential difference is generated between the magnetic brush 204 and the surface of the drum 100, and the carrier of the magnetic brush 204 is supplied from the electrode sleeve 203, which is a power feeding unit. Due to the force in the direction of arrow B generated by the injection of electric charges, the carrier of the magnetic brush 204 moves from the charging member 201 side to the drum 10 as the charged body.
It moves to the 0 side.

That is, the magnet roller 202 is arranged in the electrode sleeve 203, and the magnetic binding force of the magnet roller 202 forms and holds the magnetic brush of the carrier which is magnetic particles.
Since the magnetic restraining force is weakened at the end of the magnet roller 202, the carrier pushed in the electrode sleeve 203 and the charging nip portion N of the drum 100 in the longitudinal direction of the electrode sleeve is not fully held and is carried onto the drum 100. (Disengagement / lost of magnetic brush carrier). There has been a problem that the carrier escaped from the magnetic restraining force interrupts the exposure at the exposure portion located downstream of the charging portion or mixes in the developing device to hinder the development and cause an image defect.

In addition, in such magnetic brush charging, if the magnetic brush carrier adheres to the member to be charged,
The magnetic brush carrier of the charging member is gradually reduced, so that charging defects and the like gradually occur. Therefore, an image forming apparatus or a process cartridge using magnetic brush charging has a problem that it cannot be used for a long period of time because an image defect occurs due to the charging failure.

Further, in the above-mentioned contact charging device of the DC charging method or the AC charging method, a brush charging method using a charging brush in addition to the charging roller has been studied as a contact charging member, and when a fixed brush is used. Since it is mechanically simple and is more advantageous in cost than the roller charging method using a conductive roller, it is being put to practical use. In this case, for the purpose of improving the uniform contact property of the brush portion (brush bristle portion, brush fiber portion, pile portion e) of the charging brush to the body to be charged,
There have been proposed means such as increasing the density of implanting piles as brush fibers constituting the brush portion and devising the shape of the fibers.

However, in the low-voltage charge injection charging system, it is particularly important to ensure the uniform contact of the charging brush with the member to be charged. Even if given, the increase in the density of planting the brush fibers is naturally limited by the yarn diameter of the base fabric into which the brush fibers are planted, so that there is a limit in ensuring uniform contact.

The magnetic brush is more advantageous for obtaining the above-mentioned uniform contact property, but as described above, the fine magnetic brush carrier which has escaped the magnetic restraining force may cause an image defect or reduce the carrier. Therefore, there is a problem that the charging performance is deteriorated.

The present invention relates to a brush-type contact charging member in charge injection charging, a charging device using the charging member, and an image forming apparatus or process cartridge using the charging member or the charging device. As well as ensuring uniform contact with the body or image carrier as well as with a magnetic brush, it eliminates the problem of magnetic brush carrier detachment / flow-away, which is a problem with magnetic brushes, and ensures uniform charging and long-term stability of the charging target surface. It is an object of the present invention to make it possible to stably output a high-quality image for a long period of time by the uniformity of charging and long-term stability of the image forming apparatus and the process cartridge.

[0026]

The present invention is a charging member, a charging device, an image forming apparatus, and a process cartridge, which are characterized by the following configurations.

(1) A brush-type contact charging member for charging a charged body by bringing a brush portion into contact with the charged body in which conductive fine particles are dispersed in at least the outermost layer to apply a voltage. A charging member characterized in that magnetically conductive particles are included in the brush portion.

(2) The charging member according to (1), characterized in that both ends of the brush portion are provided with portions not containing magnetic conductive particles.

(3) The charging member according to (1), which is a rotatable roller body having a brush portion on the outer periphery.

(4) A charging device for charging an object to be charged by applying a voltage to the object to be charged, in which conductive fine particles are dispersed in at least the outermost layer, to charge the object. Is a brush-type contact charging member for bringing a brush portion into contact with a body to be charged to apply a voltage to charge the body, and the brush portion contains magnetic conductive particles therein.

(5) The charging device according to (4), wherein the charging member is a rotatable roller body having a brush portion on the outer periphery.

(6) The charging device according to (4) or (5), wherein the member to be charged is an image carrier of the image forming apparatus.

(7) The charging device according to (6), wherein the image bearing member is a photosensitive member in which a photosensitive layer and a surface protective layer are laminated in this order on a conductive substrate.

(8) The charging device according to (6), wherein the image carrier is a photoconductor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive substrate.

(9) An image forming apparatus for performing image recording by applying an image forming process including a step of charging the surface of the image carrier with a charging device, wherein the charging device has at least the outermost surface. A charging device for charging an image bearing member by bringing a charging member applied with a voltage into contact with an image bearing member in which conductive fine particles are dispersed in the layer, wherein the charging member contacts the brush portion to the image bearing member. An image forming apparatus, comprising a brush-type contact charging member that is brought into contact with the surface of the image carrier to charge the image carrier, wherein the brush portion contains magnetic conductive particles.

(10) The charging member is a rotatable roller body having a brush portion on the outer periphery (9)
The image forming apparatus according to item 1.

(11) The image forming apparatus according to (9) or (10), wherein the image bearing member is a photosensitive member in which a photosensitive layer and a surface protective layer are laminated in this order on a conductive substrate. .

(12) The image forming apparatus according to (9) or (10), characterized in that the image bearing member is a photosensitive member in which a charge generating layer and a charge transporting layer are laminated in this order on a conductive substrate. apparatus.

(13) A process cartridge which includes at least an image carrier and at least a charging member of a charging device for charging the image carrier and which is attached to and detached from the main body of the image forming apparatus. The device is a charging device for charging an image carrier by bringing a charging member applied with a voltage into contact with an image carrier in which conductive particles are dispersed in at least the outermost layer, and the charging member is a brush. A process cartridge characterized in that it is a brush-type contact charging member for charging the image carrier by applying a voltage to the image carrier by bringing the part into contact with the image carrier, wherein the brush part contains magnetic conductive particles.

(14) The charging member is a rotatable roller body having a brush portion on the outer periphery (1)
The process cartridge according to 3).

(15) The process cartridge according to (13) or (14), wherein the image bearing member is a photosensitive member in which a photosensitive layer and a surface protective layer are laminated in this order on a conductive substrate.

(16) The process cartridge as described in (13) or (14), wherein the image carrier is a photoconductor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive substrate. .

[0043]

In other words, the brush-type contact charging member (charging brush) in which the magnetic conductive particles are included in the brush portion (brush portion in which conductive fibers are used as brush bristles) is a conventional charging brush in which magnetic conductive particles are not included. Compared with the conventional charging brush, the density of the brush portion, that is, the electrode density, is higher than that of the conventional charging brush. Therefore, the uniform contact property with respect to the charged member or the image bearing member can be significantly improved. And has sufficient charging stability. Since the charging uniformity is improved, the charging failure due to fog or the like can be improved.

Since the magnetic conductive particles contained in the brush portion are easily bound by the pile of conductive fibers that are the brush bristles of the brush portion, the magnetic brush carrier as in the case of the magnetic brush alone is used. As it can be prevented from coming off and being washed away, durability stability is improved. Further, the amount of magnetic carrier used can be made smaller than that of a single magnetic brush.

Therefore, regarding the brush-type contact charging member in charge injection charging, the charging device using the charging member, the charging member or the image forming apparatus or the process cartridge using the charging device, the member to be charged or the charging member of the charging member is used. As well as ensuring uniform contact with the image carrier as well as the magnetic brush, it eliminates the problem of magnetic brush carrier detachment and drainage, which is a problem with magnetic brushes, and improves the uniformity of charging and the long-term stability of the surface of the charged object. In the image forming apparatus and the process cartridge, it is possible to stably output a high-quality image for a long period of time due to the uniform charging and long-term stability of the charging.

[0046]

【Example】

<Embodiment 1> (FIGS. 1 to 4) (1) Example of image forming apparatus (FIG. 1) FIG. 1 is a schematic configuration diagram of an example of the image forming apparatus. The image forming apparatus of this example is a laser beam printer using an electrophotographic process.

Reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member in which conductive fine particles are dispersed in at least the outermost layer, and the clockwise direction indicated by an arrow. Is rotated at a predetermined process speed (peripheral speed). The layer structure of the photosensitive drum 1 will be described in detail later in item (2).

Reference numeral 2 is a contact charging device using a brush-type contact charging member (hereinafter referred to as a charging brush) 20. The charging brush 20 and the charging device 2 will be described in detail later in (3). The photosensitive drum 1 is uniformly primary-charged by the charging device 2 to a predetermined polarity and potential during the rotation process.

The charged surface of the rotary photosensitive drum 1 is intensity-modulated corresponding to the time-series electric digital pixel signal of the target image information output from a laser beam scanner (not shown) including a laser diode, a polygon mirror, and the like. Scanning exposure 3 (image exposure) is performed by the laser beam and the exposed portion is destaticized to form an electrostatic latent image corresponding to the target image information on the peripheral surface of the rotating photosensitive drum 1.

The electrostatic latent image is reversely developed as a toner image by the toner adhering to the exposed portion by the jumping development type reversal developing device 4 using magnetic one-component insulating toner (negative toner). 4a is a developing sleeve, and S2 is a developing bias applying power source.

On the other hand, a transfer material 9 as a recording material is supplied from a paper feeding unit (not shown), and the rotary photosensitive drum 1 and a contact transfer means which is brought into contact with the rotary photosensitive drum 1 with a predetermined pressing force have a medium resistance. It is introduced into the pressure contact nip portion (transfer portion) T with the transfer roll 5 at a predetermined timing. A transfer bias voltage of 3 KV is applied to the transfer roll 5 from the transfer bias applying power source S3 in this example. The transfer material 9 introduced into the transfer portion T is nipped and conveyed by the transfer portion T, and the toner images formed and carried on the surface of the rotary photosensitive drum 1 are sequentially transferred to the surface side by electrostatic force and pressing force. Will be done.

The transfer material 9 on which the toner image has been transferred is separated from the surface of the photosensitive drum 1 and is fixed by a fixing device 7 such as a heat fixing system.
Then, the toner image is fixed and is discharged to the outside of the apparatus as an image formed product (print / copy).

Further, the surface of the photosensitive drum 1 after the transfer of the toner image to the transfer material 9 is cleaned by the cleaning device 6 to remove adhered contaminants such as residual toner, and repeatedly used for image formation. 6a is a urethane rubber counter blade as a cleaning member.

In the printer of this embodiment, a process in which four process devices, that is, the photosensitive drum 1, the charging brush 20, the developing device 4, and the cleaning device 6 are contained in the cartridge 8 and which can be attached / detached and exchanged collectively with respect to the printer main body. It is a cartridge type device. Reference numeral 10 denotes an attachment / detachment guide / support member for the cartridge 8. However, the image forming apparatus is not limited to the process cartridge detachable type.

(2) Photosensitive Drum 1 In the present embodiment, the photosensitive drum 1 as the member to be charged is charged by directly and uniformly injecting charges into the surface thereof from the charging brush 20 (charge injection charging).

Therefore, from the viewpoint of charge injection efficiency and uniformity, at least a surface layer of which conductive particles are dispersedly contained is used. An image resulting from a phenomenon in which conductive particles are not dispersed in the surface layer has a low charge injection efficiency in charge injection charging and is insufficiently charged or the charge injection is uneven. Defects are likely to occur.

The constitution of the photoreceptor is not particularly limited except for the above-mentioned dispersion of the conductive fine particles in the surface layer, and
Any conventional photosensitive member can be used. For example, as the constitution of the photoreceptor, there are one in which a photosensitive layer made of an optical semiconductor is provided on a conductive substrate, and one in which a surface protective layer is further provided on the photosensitive layer. It can be used if conductive particles are dispersed therein.

Further, the photoconductor will be described in detail.

A) First, a photosensitive member in which a photosensitive layer and a surface protective layer are laminated in this order on a conductive substrate will be described.

The surface protective layer in the photoreceptor having this constitution is composed of a film in which conductive fine particles are dispersed and contained in a binder resin. Examples of the binder resin include polyester resin, polycarbonate resin, polystyrene resin, fluorine resin, cellulose, Usual commercially available resins such as vinyl chloride resin, polyurethane resin, acrylic resin, epoxy resin, silicone resin, alkyd resin and vinyl chloride-vinyl acetate copolymer resin can be mentioned.

As the conductive fine particles, Cu, Al,
A metal such as Ni, zinc oxide, tin oxide, antimony oxide, titanium oxide, or a metal oxide such as a solid solution or a fusion body of these substances, or a conductive polymer such as polyacetylene, polythiophene, or polypyrrole can be used. From the viewpoint of translucency, it is preferable to use a conductive material having high transparency. The particle size of the conductive fine particles is preferably 0.3 μm or less from the viewpoint of transparency, and optimally 0.1 μm.
m or less.

The electric resistance of this protective layer is 10 ⁹ to 10 ¹⁴ Ω.
Set so that the range is cm. The content of the conductive fine particles in this protective layer depends on the particle size, but
A range of -100 wt% is suitable.

In this protective layer, in order to improve the dispersibility of the conductive fine particles and the adhesiveness or smoothness,
Various additives can be added. Particularly for improving dispersibility, it is very effective to add a coupling agent or to perform surface treatment of the conductive fine particles with the coupling agent.

Similarly, from the viewpoint of improving dispersibility and durability of the protective layer, the use of a curable resin as the binder resin further improves the characteristics. When a curable resin is used for the surface protective layer, a coating solution in which conductive fine particles are dispersed in a solution of a curable resin monomer or oligomer is applied onto the photosensitive layer, and after the film is formed, the coating is applied by heat or light irradiation. The coating film is cured to form a surface protective layer.

Examples of such a curable resin include acrylic resin, epoxy resin, phenol resin and melamine resin, but the curable resin is not limited to this, and energy such as light or heat is applied after coating and film formation. Any resin can be used as long as it causes a chemical reaction to be cured.

This protective layer can be obtained by applying a solution in which a binder resin, conductive fine particles and necessary additives are appropriately dissolved and dispersed onto the photosensitive layer and drying. The thickness of the protective layer depends on the electric resistance of the film, but is preferably 0.1 to 10 μm, and most preferably 0.5 to 5 μm.

As the photosensitive layer, a conventionally known photosensitive layer can be used, for example, Se, As ₂ Se ₃ , a-Si, CdS,
Inorganic optical semiconductors such as ZnO ₂ or P
Those using an organic material such as VK-TNF, a phthalocyanine pigment, and an azo pigment can be used.

Further, an intermediate layer may be provided between the surface protective layer and the photosensitive layer. Such an intermediate layer is intended to enhance the adhesion between the protective layer and the photosensitive layer, or to function as a charge barrier layer. As the intermediate layer, a commercially available resin material such as an epoxy resin, a polyester resin, a polyamide resin, a polystyrene resin, an acrylic resin or a silicone resin can be used.

As the electroconductive substrate for the photoconductor, a metal such as aluminum, nickel, stainless steel, or steel, plastic or glass having an electroconductive film, electroconductive paper, or the like can be used.

B) Next, a photosensitive member having a photosensitive layer provided on a conductive substrate will be described.

As described above, the photosensitive member needs to have conductive fine particles dispersed on the surface thereof. Therefore Cd
In the photosensitive layer in which the inorganic photo-semiconductor particles such as S and ZnO ₂ are dispersed in the binder resin, the conductive fine particles are dispersed in this film, and even in the case of the photo-sensitized layer using the organic photo-semiconductor material, the surface layer is electrically conductive. Particles are dispersed and contained.

In the case of a photosensitive layer using an organic photo-semiconductor material, the constitution is roughly classified into two types, a single layer type composed of a single layer in which an organic pigment is dispersed in a binder resin, a charge generation layer and a charge transport layer. There is a function-separated type in which layers are stacked in this order or in the reverse order. In the former case, conductive particles may be dispersed in a layer in which an organic pigment is dispersed in a binder resin, and in the latter case, conductive fine particles may be dispersed in the surface layer.

However, in view of characteristics such as durability and image stability, a photoconductor in which a charge generation layer and a charge transport layer are laminated in this order and conductive fine particles are dispersed in the charge transport layer is more preferable.

C) The photosensitive drum 1 specifically used in this embodiment is as follows. FIG. 2 shows the layer structure model diagram.

The photosensitive drum 1 of this embodiment is a function separation type O
The charge injection layer is provided on the PC photosensitive member.

That is, the conductive layer 1 as an undercoat layer is formed on the φ30 aluminum cylinder 11 (drum substrate, conductive substrate).
2 (UC layer) is formed with a film thickness of about 20 μm.

Next, in order to prevent dark decay due to injection of holes from the drum substrate 11, the injection prevention layer 13 (CP layer).
To provide. An electrically medium resistance material is used for the CP layer 13, and an insulating amylan resin is mixed with methoxymethylated nylon showing a certain degree of ionic conductivity and applied to a thickness of about 1 μm.

Next, the charge generation layer 14 (CG layer) is formed. The CG layer 14 is formed by coating a layer in which a polyvinyl butyral resin as a binder and a disazo pigment as a charge generating material are dispersed at a ratio of 1: 2 to a thickness of about 1 μm.

Next, the charge transport layer 15 (CT
Layers). The CT layer 15 plays a role of transporting only positive charges of the charge pairs generated in the CG layer 14 to the surface of the photoconductor. Specifically, a polycarbonate resin in which hydrazone is dispersed at a weight ratio of 1: 1 has a film thickness of 20.
What was coated by μm was used.

At present, the OP of an ideal N-type semiconductor is used.
Although a C photoconductor has not been found, it is theoretically possible to replace the P-type semiconductor having the above-mentioned configuration with an N-type semiconductor and perform positive charging.

Further, a charge injection layer 16 is further provided on the CT layer 15, and this injection layer 16 enables direct injection charging from the contact charging member 20. Here injection layer 16, 70 wt of SnO ₂ as conductive filler 17 in the phosphazene resins. % ((Weight of conductive filler / total weight of conductive filler and binder) × 100
(Value defined by [%]) dispersed to form a film thickness of 10 μm.

Regarding the amount of SnO ₂ dispersed, if the amount of dispersed is too large, the surface resistance value of the charge injection layer 16 may become too low, and a lateral flow of latent image charges may occur after image exposure. Yes, this phenomenon becomes remarkable especially in a high temperature and high humidity environment.

On the contrary, if the dispersion amount is too small, the charge injection layer 1
6 SnO ₂ as the conductive filler 17 does not fully appear on the surface, and the charge is not sufficiently injected, resulting in partial charge failure. Specifically, a solid white image in the reversal development system causes black spots on the sandy surface and fogging on the entire surface, resulting in a defective image.

In order to prevent these problems, as shown in Table 1, the amount of SnO ₂ dispersed is ₂ to 100 wt. It must be in the range of%. In the table, L / L environment, H
/ H environment is low temperature and low humidity environment (15 ° C × 10% R
H), high temperature and high humidity environment (32.5 ° C. × 85% RH).

[0085]

[Table 1] However, when the low-resistance charge injection layer 16 is simply formed on the surface of the photosensitive layer, the charge laterally flows through the surface and the electrostatic latent image cannot be held. Therefore, the surface resistance is high, and the anisotropic conductive property is such that the resistance value is small in the inner direction of the photosensitive drum. As an example of the configuration, it is possible to obtain the above-mentioned anisotropic conductivity by using an insulating binder in which an appropriate amount of conductive particles 17 such as SnO ₂ having a light transmitting property are dispersed.

It is possible to use other metal oxides, conductive carbon, etc. as the conductive filler 17,
Since it is a condition that light reaches the CG layer 14 during image exposure, SnO ₂ particles having good light transmittance are preferable. S
70wt the nO _2. % In the dispersed state, the charge injection layer 1
Since 6 alone showed a transmittance of 95% with respect to light of 730 nm, it is possible to form a latent image by image exposure at a level where there is no practical problem.

The same effect can be observed by dispersing TiO ₂ particles as another conductive filler, but when TiO ₂ which is a white particle is dispersed in the charge injection layer 16, the light transmittance is reduced. When the light transmittance of the charge injection layer 16 is less than 50%,
A sufficient image cannot be obtained because a sufficient bright portion potential cannot be obtained. In order to prevent this, if the exposure intensity is increased, the light scattering phenomenon due to the conductive particles of the charge injection layer 16 becomes remarkable, which causes bleeding and blurring of the latent image, which is not preferable.

(3) Charging Device 2 (FIG. 3) a) Charging Device Structure The charging brush 20 used in the present invention has a brush portion 23 made of semiconductive fiber, and is preferably a rotatable roll. A magnetic brush (roller brush) containing magnetic conductive particles (magnetic carriers) 24 is used, and a voltage is applied to the brush, and the photosensitive drum 1 is rubbed and charged.

The resistance value of the semiconductive fiber of the brush portion 23 is 1
A material having a volume resistivity of about 0 ³ to 10 ⁷ Ω · cm is used. Specifically, SA-7 (acrylic type, manufactured by Toray),
Examples include fibers in which conductive carbon black is dispersed, such as Bertron (nylon-based, Kanebo), REC (rayon-based, Unitika), Roval (polypropylene-based, Mitsubishi Rayon), Cracabo (PET-based, Kuraray). I can. These fibers having a thickness of about 1 to 10 denier are easy to use in terms of chargeability and pile density.

The magnetic conductive particles 24 have a particle size of 30 μm.
Hereinafter, those having a resistance value of 10 ⁴ to 10 ⁸ Ω are preferably used. The magnetic conductive particles include: -a resin and a magnetic powder of magnetite, ferrite, cobalt or the like kneaded and molded into particles, or a mixture of conductive carbon or the like for resistance adjustment; -sintered magnetite , Ferrite, or those having a resistance value adjusted by reducing these, or those having a suitable resistance value obtained by plating these magnetic particles can be used.

The charging brush 20 shown in FIG. 3 has magnetic conductive particles 24.
Is a roll brush in which the brush part 23 is included. After the pile of the semi-conductive fiber is wound around the non-magnetic electrode sleeve 22 having the magnet roll 21 as a magnetism generating member inside to form the brush portion 23, the surface is finished and the dimensional accuracy is obtained. , A certain amount of magnetic conductive particles 2
4 is placed on the pile surface and included between the fibers.

The distance between the bristles of the brush portion 23 of the charging brush 20 and the photosensitive drum 1 which faces the brush is such that the pushing amount of the pile surface is preferably 1/2 or less of the pile length t, more preferably 1/3 or less. Set. If the pushing amount is more than that, the torque pressure becomes too high, and the possibility of rubbing scratches on the surface of the photosensitive drum increases, which is not preferable.

In this embodiment, the brush portion 23 is a conductive rayon fiber REC-B (thickness 6 denier / filament, density 100,000 filament / inc) manufactured by Unitika Ltd.
At h ² , the resistance value of the brush is 3 × 10 ⁵ Ω (converted from the current value that flows when a voltage of 100 V is applied to an aluminum drum having a diameter of 30 mm with a nip width of 3 mm)) Pile-shaped tape with a diameter of 1
A roll brush having an outer diameter of 17 mm was spirally wound around a 2 mm electrode sleeve 22.

Further, in this embodiment, the magnetic conductive particles 24 contained in the brush portion 23 are the following resin carriers, and in this embodiment, 8 g of the resin carrier is contained in the brush portion 23. That is, the used resin carrier 24 is obtained by mixing 100 parts by weight of magnetite in polystyrene resin, kneading and crushing, and has a particle diameter of 30 μm and a resistance value of 1 × 10 ⁶ Ω. This resistance value is almost the intrinsic resistance value of magnetite itself, and when the resistance value is further increased, the mixing amount of magnetite is reduced. Further, when it is desired to lower the value, a desired resistance value can be obtained by externally adding carbon black to the particle surface.

Magnetic conductive particles 2 contained in the brush portion 23
4 is restrained by the magnetic force of the magnet roll 21 and also by the bristles of the brush portion 23.

The charging brush (roll brush) 20 as the contact charging member is arranged substantially parallel to the photosensitive drum 1, and the brush portion 23 containing the magnetic conductive particles 24 is brought into contact with the surface of the photosensitive drum 1 to make a magnet roll. The shaft 21 is supported by a bearing (not shown). The magnet roll 21 is non-rotatably fixed and held, and the non-magnetic electrode sleeve 2
2 is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed by a driving unit (not shown). That is, the brush portion 23 rotates with the rotation of the electrode sleeve 22 while keeping contact with the surface of the photosensitive drum 1. N is a contact nip portion between the brush portion 23 and the photosensitive drum 1 (hereinafter referred to as a charging nip portion). S1 is a power supply for applying a charging bias to the electrode sleeve 22 as a power feeding portion to the brush portion 23.

In this example, the electrode sleeve 22, that is, the brush portion 2
3 is rotated at a speed 1 times the peripheral speed of the photosensitive drum 1 so as to move in the opposite direction to the rotating direction of the photosensitive drum 1 in the charging nip portion N, and the surface of the photosensitive drum 1 and the magnetic conductive material The brush portion 23 including the particles 24 is uniformly contacted. Since the fine magnetic conductive particles 24 are in contact with the photoconductor, charging can be performed even if the peripheral speed is less than 1 time and about 0.1 times.

Thus, the photosensitive drum 1 and the electrode sleeve 2
2 is driven to rotate, and the electrode sleeve 22 is connected to the power source S1.
By applying a charging bias of a predetermined polarity and potential to the conductive fine particles 17 of the charge injection layer 16 on the surface of the photosensitive drum 1, charges are injected by the brush portion 23, and the surface of the photosensitive drum 1 is predetermined. Charged by injection charging method to polarity / potential.

B) Principle of Charging (FIG. 4) The principle of actual charge injection will be described with reference to FIG.

In the present embodiment, the charge injection layer 16 is provided on the surface of the photosensitive drum 1 as the member to be charged, so that the SnO ₂ particles 17 as the conductive fine particles, which are exposed on the surface, form the electrode of the capacitor (see FIG. 4 (b)).

That is, if the conductive fine particles 17 have an appropriate amount of dispersion as described above, there are countless minute capacitors sandwiching the CT layer 15 as a dielectric on the surface of the photoconductor as shown in FIG. 4B. Can be considered to be located in. By bringing a conductive contact charging member 20 into contact with the electrode 17 and applying a voltage, it is possible to inject charges into the electrode 17 as in a normal capacitor.

At this time, since the conductive fine particles 17 as electrodes are electrically independent from each other and form a kind of minute float electrode, the surface of the photoconductor is charged / charged to a uniform potential macroscopically. However, in reality, countless minute SnO ₂ particles 17 charged are covering the surface of the photoconductor. Therefore, even if image exposure with laser light is performed, each SnO ₂ particle 1
Since 7 is electrically independent, it is possible to hold an electrostatic latent image.

For reference, in the case of the conventional photosensitive drum having no charge injection layer, the electrode as in this embodiment does not exist on the surface of the photosensitive member, or only the trap level plays the role of the electrode. No injection is made.

(4) Image Output Example As described above, the brush-type contact charging member (charging brush) 20 in which the magnetic conductive particles (magnetic carrier) 24 are included in the brush portion 23 does not include the magnetic conductive particles 24. Since the density of the brush portion, that is, the electrode density is higher than that of the charging brush, it is possible to improve the uniform contact property with respect to the photosensitive drum 1 as the member to be charged much more than the conventional charging brush alone, and similar to the magnetic brush. Uniform contact can be secured,
It has sufficient charge stability. Since the charging uniformity is improved, the charging failure due to fog or the like can be improved.

Since the magnetic conductive particles 24 contained in the brush portion 23 are easily restrained by the pile of conductive fibers that are the brush bristles of the brush portion 23, the magnetic conductive particles 24 in the case of the magnetic brush alone are Since it is possible to prevent the magnetic brush carrier from coming off and flowing out, durability stability is improved. Further, the amount of magnetic carrier used can be made smaller than that of a single magnetic brush.

Therefore, regarding the brush-type contact charging member in charge injection charging, the charging device using the charging member, the charging member or the image forming apparatus or the process cartridge using the charging device, the member to be charged of the charging member is used. In addition to ensuring uniform contact with the image carrier as well as with a magnetic brush, it eliminates the problem of magnetic brush carrier detachment / flow-off, which is a problem with magnetic brushes, and ensures uniform charging and long-term stability of the charged surface. Improvements have been made possible, and in the image forming apparatus and the process cartridge, it is possible to stably output a high-quality image for a long period of time due to the uniformity of charging and long-term stability.

Specifically, in the printer shown in FIG. 1,
The magnetic conductive particles 2 of the charging device 2 (FIG. 3) of the above item (3).
A charging brush (roll brush) 20 containing 4 is brought into contact with the photosensitive drum 1 at a charging nip width of about 5 mm, and is rotated in the same direction as the rotating direction of the photosensitive drum 1 so that the peripheral speed difference becomes 1 time. Meanwhile, charging was performed at a process speed of 50 mm / sec.

As a result, the surface potential of the photosensitive drum was almost equal to the applied voltage, and the surface potential when a DC voltage of -500V was applied was -490V.

Also, with the above printer, 32.5 ° C ×
85% RH high temperature and high humidity environment (H / H environment), 23 ° C x
65% RH normal environment (N / N environment), 15 ° C x 10
Image output was performed under low temperature and low humidity environment (L / L environment) of% RH, but a good image without charging defects, image blurring, and flow can be obtained, and this method does not use discharge. Due to the charging method, generation of ozone and flow due to discharge on the surface of the photosensitive drum did not occur.

In order to obtain a similar image with a conventional photosensitive drum, it is necessary to apply a voltage obtained by superposing an AC voltage of 2000V (peak-to-peak voltage value) on a DC voltage of -500V to perform AC charging under this condition. Then the amount of ozone is 0.01ppm
It was observed that the surface of the photosensitive drum was roughened by the discharge, and the charging noise was generated by the oscillating electric field.

As a comparative example, when an image was formed using a conventional photosensitive drum under the bias conditions of this example, the surface potential of the photosensitive drum was almost 0 V and charging was not performed.

As described above, by adopting the configuration of this embodiment, it becomes possible to perform charging without discharge at a low DC voltage, and ozone generation, AC
It became possible to eliminate the charging noise.

Furthermore, the charging potential after 5k printing is -4.
The voltage was 75 V, the decrease in charging property during durability was small, and the image quality was good. Carrier amount after 5k printing is 7.8g
And there was almost no loss due to spillage. Also 5
After k-printing, the charging potential when using only the charging brush that does not include the magnetic conductive particles 24 is -380V,
When a solid white image was output, there was fog on the whole and the image quality was degraded.

Example 2 The same examination as in Example 1 was conducted except that the brush portion 23 of the charging brush 20 was changed to have a thickness of 10 denier / filament and a density of 70,000 filament / inch ² .

A DC voltage of -500 V is applied to the electrode sleeve 22.
The surface potential of the photosensitive drum was -480 V when applied to the sheet, and the charging potential after 5 k printing was -465 V, and the image quality was good.

<Embodiment 3> An examination was conducted in the same manner as in Embodiment 1 except that the charging brush 20 similar to that in Embodiment 1 was used and the process speed was set to 94 mm / sec.

The surface potential of the photosensitive drum when -700 V was applied was -680 V, the charging potentials of the photosensitive drum after 5 k and 10 k printing were -660 and 650 V, respectively, and the fog of a solid white image was 1% or less in the initial reflectance. Against 1.5
It was almost the same as%, and there was no effect on the image quality of characters etc.

The amount of magnetic conductive particles contained in the brush portion 23 was 7.2 g after 10 k printing, compared with 8 g initially used.
Met.

When the peripheral speed difference was 0.5 times and the same examination was conducted, the surface potential of the photosensitive drum when -700 V was applied was-.
675V, the photosensitive drum charging potentials after printing 5k and 10k were -650 and -640V, respectively, and no fog was observed in the solid white image.

<Embodiment 4> (FIG. 5) In this embodiment, the brush portion 23 provided in the conductive sleeve 22 of the charging brush 20 is provided in the area portion 20A corresponding to the maximum sheet passing width as shown in the schematic view of FIG. Thickness 6 denier / filament, density 100,000 filament / inch ² , outer diameter 17m
m, both outer area portions 20B and 20B have a thickness of 3 denier / filament and a density of 300,000 filament / inch.
^{2. The} examination was conducted in the same manner as in Example 3 except that the outer diameter was 19 mm and the same amount (8 g) of the magnetic conductive particles 24 as described above was included in the pile portion of the former region portion 20A.

The charging potentials of the photosensitive drums after printing 5k and 10k were -650 and -640V, respectively, and no fog was observed in the solid white image.

The amount of the magnetic conductive particles was 8 g in the initial use,
After 10 k printing, the weight is 7.5 g, and the pile structure (brush part structures 20A and 20B) provided with the magnetic particle-free parts 20B at the pile parts at both ends is taken as in the present embodiment.
Preferably, the portion 20B has a small fiber diameter and a flock density of 20.
The flow-out prevention effect was further enhanced by increasing the outer diameter of the portion A or making the outer diameter of the portion 20B larger than that of the portion 20A.

The brush-type contact charging member (charging brush) of the present invention, in which the magnetic conductive particles 24 are contained in the brush portion 23, is not limited to the roll brush 20 of the embodiment, but is a rotary endless type. It can also be configured as a belt type charging brush. Further, it may have a non-rotating rod shape, a square bar shape, a horizontally long plate shape, or the like. Alternatively, the non-magnetic electrode sleeve 22 may be eliminated, and the brush member 23 may be directly provided on the magnet member whose surface is made electrically conductive, and the magnetic conductive particles 24 may be included in the brush member. .

[0124]

As described above, according to the present invention, a brush-type contact charging member in charge injection charging, a charging device using the charging member, an image forming apparatus or a process cartridge using the charging member or the charging device. With respect to the charging member, the uniform contact property of the charging member with respect to the member to be charged or the image carrier is ensured in the same manner as the magnetic brush, and the problem due to detachment / flow-off of the magnetic brush carrier, which is a problem with the magnetic brush, is eliminated, and the surface of the member to be charged is The uniformity and long-term stability of charging can be improved, and the uniformity and long-term stability of charging in image forming apparatuses and process cartridges enables stable output of high-quality images over a long period of time. It has become possible.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

[Fig. 2] Model diagram of layer structure of photosensitive drum

FIG. 3 is a schematic configuration diagram of a charging device.

4A and 4B are explanatory views of the principle of charge injection charging.

FIG. 5 is a schematic diagram of the configuration of a charging brush (roll brush) of Example 4.

FIG. 6A is a cross-sectional model view of a conventional magnetic brush type charging device, and FIG. 6B is a vertical cross-sectional model diagram of one end of the magnetic brush type charging member.

[Explanation of symbols]

1 Photosensitive Drum as Charged Object 16 Charge Injection Layer 17 Conductive Fine Particles 2 Contact Charging Device 20 Charging Brush (Roll Brush) 21 Magnet Roll 22 Non-Magnetic Sleeve 23 Brush Part 24 Magnetic Conductive Particles Enclosed in Brush Part (Magnetic Carrier) ) S1 Charging bias application power supply

Claims (16)

[Claims] 1. A brush-type contact charging member for charging a charged body by applying a voltage to a charged body in which conductive fine particles are dispersed in at least an outermost surface layer to apply a voltage, A charging member characterized in that magnetically conductive particles are included in the brush portion. 2. The charging member according to claim 1, wherein both ends of the brush portion are provided with portions that do not contain magnetic conductive particles. 3. The charging member according to claim 1, wherein the charging member is a rotatable roller body having a brush portion on the outer periphery. 4. A charging device for charging an object to be charged by bringing a charging member, to which a voltage is applied, into contact with an object to be charged, in which conductive particles are dispersed in at least the outermost layer. A charging device which is a brush-type contact charging member for charging a charged body by bringing a brush portion into contact with the charged body and applying a voltage, wherein the brush portion contains magnetic conductive particles. 5. The charging device according to claim 4, wherein the charging member is a rotatable roller body having a brush portion on its outer periphery. 6. The charging device according to claim 4 or 5, wherein the member to be charged is an image carrier of an image forming apparatus. 7. The image carrier comprises a photosensitive layer, a photosensitive layer, and
The charging device according to claim 6, wherein the charging device is a photoconductor in which surface protection layers are laminated in this order. 8. The charging device according to claim 6, wherein the image carrier is a photoconductor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive substrate. 9. An image forming apparatus for performing image recording by applying an image forming process including a step of charging the surface of an image carrier with a charging device, wherein the charging device is at least an outermost layer. A charging device for charging an image bearing member by bringing a charging member to which a voltage has been applied into contact with the image bearing member in which conductive fine particles are dispersed. The charging member contacts the brush portion to the image bearing member. An image forming apparatus, which is a brush-type contact charging member that applies a voltage to charge an image bearing member, wherein magnetically conductive particles are included in the brush portion. 10. The image forming apparatus according to claim 9, wherein the charging member is a rotatable roller body having a brush portion on its outer periphery. 11. The image forming apparatus according to claim 9, wherein the image bearing member is a photosensitive member in which a photosensitive layer and a surface protective layer are laminated in this order on a conductive substrate. 12. The image forming apparatus according to claim 9, wherein the image carrier is a photoconductor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive substrate. 13. A process cartridge which includes at least an image carrier and at least a charging member of a charging device for charging the image carrier and which is attached to and detached from an image forming apparatus main body. Is a charging device for charging the image bearing member by bringing a charging member applied with a voltage into contact with an image bearing member in which conductive fine particles are dispersed in at least the outermost layer, and the charging member is a brush portion. Is a brush-type contact charging member for charging the image carrier by applying a voltage to the image carrier to apply a voltage, wherein the brush portion contains magnetic conductive particles. 14. The charging member is a rotatable roller body having a brush portion on the outer periphery thereof.
The process cartridge described in 1. 15. The process cartridge according to claim 13, wherein the image bearing member is a photosensitive member in which a photosensitive layer and a surface protective layer are laminated in this order on a conductive substrate. 16. The process cartridge according to claim 13 or 14, wherein the image carrier is a photoconductor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive substrate.