JP2002304044A - Electrifier and image forming apparatus mounted with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a stable discharge state for a long time by surely and efficiently cleaning a saw tooth electrode with a small-sized and simple constitution. SOLUTION: In an electrifier 1 of a corona discharge system which electrifies a photoreceptor drum by a saw tooth electrode 2 having a lot of discharge electrodes 2a like saw teeth arranged in the lengthwise direction of the photoreceptor drum, without contacting, a cleaner 3 which brings a cleaning member 5 into sliding contact with the saw tooth electrode 2 to clean the saw tooth electrode 2. The cleaning member 5 is impregnated with liquid which reduces friction between the cleaning member 5 and the saw tooth electrode 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge in which a plurality of sawtooth-shaped discharge electrodes are charged in a non-contact manner by a sawtooth electrode arranged along the longitudinal direction of the image carrier. TECHNICAL FIELD The present invention relates to a charging device of a system and an image forming apparatus equipped with the charging device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a facsimile, a laser printer, or the like using an electrophotographic system, a means such as a discharge wire (corona charger) is used as a means for uniformly charging the surface of a photoconductor as an image carrier. ) Using a corona charging method. The discharge wire used in the charging device using the corona charging method repeatedly discharges by applying a voltage to a thin wire, and when the discharge is performed for a long time, the surface of the discharge wire gradually becomes dirty. Go. Therefore, if the discharge wire is kept in that state and the discharge is continued, the corona discharge state on the surface of the photoreceptor fluctuates, so that a good and stable discharge state cannot be maintained. Will begin to fall. Therefore, in an image forming apparatus using such a corona charging type charging device, the discharge wire is cleaned when the stain on the discharge wire has advanced to some extent. As a cleaning method, for example, a cleaning member formed in a plate shape with a sponge is pressed against a discharge wire at the time of cleaning and is moved along the longitudinal direction of the discharge wire to directly clean the discharge wire.

[0003] In a corona charging type charging device using such a discharge wire, the components constituting the charging device are eroded or unpleasant odor is caused by the influence of ozone generated at the time of discharge. May be. In particular, copiers and laser printers are usually used in offices in many cases, so that the odor associated with the generation of ozone may become a complaint. In addition, if such a large amount of ozone enters the body, the effect on the mind and body can be considered. Therefore, it is desirable to reduce the amount of such ozone generated. By the way, the corona discharge type charging device is roughly classified into a wire discharge type and a pin discharge type, and it is said that the amount of generated ozone is smaller in the pin discharge type.
Therefore, in recent years, this pin discharge type charging device has been used in electrophotographic copying machines, laser printers and the like.

As a charging device of the pin discharge type, for example, there is a device using an electrode plate in which a plurality of sawtooth-shaped electrodes are formed on one thin plate-like member (for example, Japanese Patent Application Laid-Open No. 63-15 / 1988).
272 and JP-A-5-45999).
Cleaning is necessary also in such a sawtooth electrode, and a charging device having this sawtooth electrode has excellent discharge performance,
There was a drawback that cleaning was difficult due to its shape. Also, the durability was sometimes shorter than that of the wire discharge method. Therefore, for example, in Japanese Patent Application Laid-Open No. 9-21940, in order to improve the cleaning performance of the serrated charging electrode, a cleaning made of roll-shaped silicone rubber or foamed styrene is provided near the electrode to be discharged. By pressing the member, moving it along the longitudinal direction of the saw-tooth discharge electrode, and rotating it, the tip of the saw-tooth discharge electrode is cleaned to remove foreign matter adhering thereto.

[0005]

However, in the case of such a cleaning device in which the cleaning member is rotated to clean the saw-toothed electrode, the cleaning performance of the electrode is high, but the cleaning part of the electrode is high. Since it is limited to only the front end, there is a problem in that it is not possible to clean even a portion slightly away from the front end. Further, as described above, in the configuration in which the tip of the sawtooth-shaped discharge electrode is cleaned by rotating the cleaning member, a mechanism for rotating the cleaning member is required, so that the mechanism is complicated and the components are accordingly complicated. Since the number of points increases, there is a disadvantage that it is difficult to reduce the size of the entire apparatus. Further, when the cleaning member and the saw-toothed electrode are in direct contact, a large frictional force is generated between them, and the frictional force may cause the cleaning member to not rotate or move smoothly. there were. The present invention has been made in view of the above problems, and has a sawtooth electrode having a plurality of sawtooth-shaped electrodes. It is an object of the present invention to maintain a stable discharge state for a long time by performing cleaning with high cleaning efficiency.

[0006]

According to the present invention, in order to achieve the above object, a plurality of sawtooth-shaped discharge electrodes are formed by sawtooth electrodes arranged along the longitudinal direction of the image carrier. In a corona discharge type charging device for charging a carrier in a non-contact manner, a cleaning device for cleaning a sawtooth electrode by sliding a cleaning member on the sawtooth electrode is provided, and the cleaning member and the sawtooth are provided on the cleaning member. It is impregnated with a liquid that reduces friction with the electrode. The liquid impregnated in the cleaning member is preferably a non-volatile liquid having a viscosity of 30 to 100 cSt. Then, the liquid may be a liquid mainly composed of silicone oil. Further, the cleaning member is formed of a member having a large number of bubbles inside,
The liquid is preferably retained by the bubbles. The cleaning member is preferably formed to have an electric resistivity of 10 ⁵ Ω · m or more.

Further, it is effective that the range of sliding contact of the cleaning member with the sawtooth electrode is longer than the length of the sawtooth in the protruding direction of the sawtooth of the plurality of discharge electrodes formed in a sawtooth shape. is there. Further, the cleaning range of the cleaning member along the longitudinal direction of the image carrier may be longer than the length of the effective image forming area of the image carrier. The cleaning member may be movable along the longitudinal direction of the image carrier to a standby position outside the effective image forming area of the image carrier. Further, the present invention also provides an image forming apparatus equipped with any one of the charging devices described above. In the image forming apparatus, it is effective to use an amorphous silicon photoconductor as the image carrier.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the configuration of a charging device according to the present invention, FIG. 2 is an enlarged view showing a part of a saw-tooth electrode provided on the charging device, and FIG. FIG. 4 is a configuration diagram showing the vicinity of an image forming unit of an image forming apparatus provided with the charging device. In the charging device 1 shown in FIG. 3, a plurality of discharge electrodes 2a formed in a sawtooth shape are formed by sawtooth electrodes 2 arranged along the longitudinal direction (left and right directions in the figure) of a photosensitive drum as an image carrier. This is a corona discharge type charging device for charging the photoconductor drum in a non-contact manner, and includes a cleaning device 3 for cleaning the sawtooth electrode 2 by sliding a cleaning member 5 on the sawtooth electrode 2. The cleaning member 5 has a liquid 9 for reducing friction between the cleaning member 5 and the sawtooth electrode 2.
(See FIG. 1).

A laser printer, which is an image forming apparatus provided with four charging devices 1 in an image forming section as shown in FIG.
Four photoreceptor drums 10Y and 10 each serving as an image carrier and having amorphous silicon laminated on the surface layer.
This is an electrophotographic printer capable of forming a color image by reversal development using M, 10C, and 10B. The photoconductor drums 10Y, 10M, 10C, and 10B are arranged in the printer body in parallel in the horizontal direction, and the above-described cleaning device 3 is provided around each of the photoconductor drums 10Y, 10M, 10C, and 10B. Developing units 6Y, 6M, 6C, 6B for developing latent images with toners of respective colors of yellow, magenta, cyan, and black;
A cleaning unit 7 and a static elimination lamp 8 are provided, respectively. Below the photosensitive drums 10Y to 10B, an intermediate transfer belt 25 as an intermediate transfer body is disposed in contact with the photosensitive drums 10Y to 10B, respectively. The intermediate transfer belt 25 has three support rollers. 2
6a, 26b, and 26c are installed so as to be rotatable in the direction of arrow B.

The intermediate transfer belt 25 is, for example, a belt mainly made of polyimide and has a resistance of 10 ² Ω.
・ It is a low resistance belt of cm. Photoconductor drums 10Y-1
The primary transfer rollers 27a, 27b, 27c, and 27d are in contact with 0B via the intermediate transfer belt 25 from below. The primary transfer member is not limited to the roller described above, but may be a non-contact charger. The primary transfer roller 27a of the intermediate transfer belt 25,
27b, 27c, 27d and photosensitive drums 10Y to 10B
The toner images formed on the surfaces of the photosensitive drums 10Y to 10B are sequentially transferred by electrostatic force and pressing force to the portions sandwiched between the photosensitive drums 10Y and 10B. Note that a belt cleaning unit 28 is provided on the intermediate transfer belt 25 at the position of the support roller 26c.

The support roller 26b also has a function as an opposing roller of the secondary transfer means.
A secondary transfer device 29 composed of a belt is provided opposite to the intermediate transfer belt 25 via an intermediate transfer belt 25. In this embodiment, the belt-shaped secondary transfer device 29 is used. However, the secondary transfer unit may be a roller or a charger. Although not shown in the drawing, the secondary transfer device 29 is provided with a cleaning unit for cleaning dirt on the belt. This secondary transfer device 2
Reference numeral 9 also functions to transport the sheet on which the image has been transferred to the entrance of the fixing device 30. The fixing device 30 is a heat fixing type fixing unit, and includes an endless fixing belt 31 stretched between two rollers, and a pressing roller 32 pressed against the fixing belt 31. ing. This fixing device 3
Numeral 0 is disposed below the support roller 26c of the intermediate transfer belt 25 so as to enter the opposite roller side of the secondary transfer.
Below the fixing device 30 and the secondary transfer device 29, a double-sided reversing unit (not shown) is arranged for double-sided transfer in the horizontal direction. The double-sided reversing unit includes a reversing roller, a sending roller, a plurality of pairs of conveying rollers, and the like.

The color image forming process of this laser printer includes four photosensitive drums 10Y, 10M, 10C,
10B, a latent image corresponding to each color of yellow, magenta, cyan, and black is sequentially formed, and the latent images are sequentially developed with toner of each color by developing units 6Y, 6M, 6C, and 6B. The images are transferred onto the intermediate transfer belt 25 so as to be sequentially superimposed to form a four-color superimposed toner image. The toner image is fed at a predetermined timing from a paper feeding unit (not shown), and the timing is adjusted by the registration roller 20, and is transferred by the secondary transfer device 29 to the fed paper. Then, the toner remaining on the intermediate transfer belt 25 after the transfer of the toner image is removed and collected by the belt cleaning unit 28. The paper on which the toner image of the four colors is transferred is subjected to fixing processing of the toner image by the fixing device 30, and is discharged onto a discharge tray by a discharge device (not shown).

Next, each part of the laser printer will be described in detail. The photoreceptor drum 10Y is a rotating drum type electrophotographic photoreceptor to be charged, and has, for example, positive amorphous silicon (hereinafter a-type) having a diameter of 60 mm.
4) in the direction indicated by the arrow A in FIG.
It is driven to rotate at a peripheral speed of 00 mm / sec. This a-
The Si photoreceptor heats a conductive support to 50 ° C. to 400 ° C., and forms a vacuum deposition method, a sputtering method, an ion plating method, a thermal CVD method, a photo CVD method, a plasma CVD method, etc. on the support. A photoconductive layer made of a-Si is formed by a film method. Among them, a plasma CVD method, that is, a method in which a raw material gas is decomposed by direct current, high frequency, or microwave glow discharge to form an a-Si deposited film on a support is used as a preferable method. The layer configuration of the a-Si photoreceptor includes, for example, those shown in the schematic configuration diagrams of FIGS. 5A to 5D. A photoconductor 500A shown in FIG. 5A has a photoconductive layer 502 made of a-Si: H, X and having photoconductivity provided on a support 501. The photoconductor 500B shown in FIG. 5B is provided with a photoconductive layer 502 made of a-Si: H, X and having photoconductivity and an amorphous silicon-based surface layer 503 on a support 501. It is a thing. The photoconductor 500C shown in FIG. 5C has a photoconductive layer 502 made of a-Si: H, X and having photoconductivity, and an amorphous silicon-based surface layer 503 on a support 501.
And an amorphous silicon-based charge injection blocking layer 504. Photoconductor 500 shown in FIG.
D is provided with a charge generation layer 505 made of a-Si: H, X and a photoconductive layer made of a charge transport layer 506 on a support 501. Then, an amorphous silicon-based surface layer 503 is provided thereon.

The support 501 of the photosensitive member may be either conductive or electrically insulating. As the conductive support, Al, Cr, Mo, Au, In, Nb, Te, V,
Metals such as Ti, Pt, Pd, and Fe, and alloys thereof;
For example, stainless steel is used. Further, a film or sheet of a synthetic resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polystyrene, polyamide, etc., at least the surface of the electrically insulating support such as glass, ceramic or the like on the side on which the photosensitive layer is formed, A support subjected to a conductive treatment can also be used. The shape of the support 501 can be a cylindrical or plate-like endless belt having a smooth surface or an uneven surface, and its thickness is appropriately determined so as to form a desired photoreceptor for an image forming apparatus. However, when flexibility as a photoreceptor for an image forming apparatus is required, it can be made as thin as possible within a range where the function as a support can be sufficiently exhibited. The support 501 is usually 10 μm or more in terms of production, handling, mechanical strength and the like.

The a-Si photoreceptor has a structure shown in FIG.
The conductive support 501 and the photoconductive layer 502 as shown in FIG.
It is more effective to provide a charge injection blocking layer 504 having a function of blocking charge injection from the support 501 side. That is, the charge injection blocking layer 504 has a function of preventing charges from being injected from the support body 501 side to the photoconductive layer 502 side when the photosensitive layer is subjected to a charging treatment of a fixed polarity on its free surface. However, such a function is not exhibited when receiving a charging treatment of the opposite polarity, that is, it has a so-called polarity dependency. In order to provide such a function, the charge injection blocking layer 504 contains a relatively large number of atoms for controlling conductivity as compared with the photoconductive layer. The charge injection blocking layer 5
The layer thickness of the layer 04 is preferably 0.1 to 5 μm, more preferably 0.3 to 4 μm, and most preferably 0.5 to 3 μm from the viewpoint of obtaining desired electrophotographic characteristics and economic effects.
It is desirable that The photoconductive layer 502 is formed on the undercoat layer as needed, and the layer thickness of the photoconductive layer 502 is appropriately determined as desired from the viewpoint of obtaining desired electrophotographic characteristics and economic effects, Preferably 1-100μ
m, more preferably 20-50 μm, optimally 23-4
It is desirable that the thickness be 5 μm.

The charge transport layer 506 shown in FIG.
Is a layer mainly having a function of transporting electric charges when the photoconductive layer is functionally separated. This charge transport layer 506 is
It is composed of a-Si (H, F, O) containing at least silicon atoms, carbon atoms, and fluorine atoms, and if necessary, hydrogen atoms and oxygen atoms, and has desired photoconductive properties, particularly charge retention. It has characteristics, charge generation characteristics and charge transport characteristics. In the image forming apparatus according to this embodiment,
It is particularly preferred that it be made of a-Si containing an oxygen atom. The thickness of the charge transport layer 506 is appropriately determined from the viewpoint of obtaining desired electrophotographic properties and economic effects, and is preferably 5 to 50 μm, more preferably 10 to 40 μm, and most preferably Is desirably 20 to 30 μm. The charge generation layer 505 is a layer mainly having a function of generating charges when the photoconductive layer is separated in function. The charge generation layer 505 contains at least silicon atoms as constituent elements, and contains substantially no carbon atoms.
If necessary, it is made of a-Si: H containing a hydrogen atom, and has desired photoconductive properties, particularly, charge generation properties and charge transport properties.

The thickness of the charge generation layer 505 is appropriately determined from the viewpoint of obtaining desired electrophotographic characteristics and economic effects, and is preferably 0.5 to 15 μm.
m, more preferably 1 to 10 μm, optimally 1 to 5 μm
It is desirable that The a-Si photoreceptor described above is further provided on a photoconductive layer composed of a charge generation layer 505 and a charge transport layer 506 on a support 501, if necessary, as shown in FIG. It is preferable to form the surface layer 503. This surface layer 503 has a free surface, and mainly has moisture resistance,
Continuous repeated use characteristics, electrical pressure resistance, use environment characteristics,
It is provided to achieve durability. The thickness of the surface layer 503 is usually 0.01 to 3 μm, preferably 0.05 to 2 μm, and most preferably 0.1 to 1 μm. If the layer thickness is less than 0.01 μm, the surface layer is lost due to abrasion or the like during use of the photoreceptor, and if it exceeds 3 μm, degradation of electrophotographic properties such as an increase in residual potential is observed. . Note that the photoconductor drums 10M, 10C, and 10B shown in FIG. 4 have the same configuration as the photoconductor drum 10Y described above, and a description thereof will be omitted.

Next, the exposure system will be described. Scanning exposure by a laser beam (which may be either LD or LED) corresponding to each image of yellow, magenta, cyan, and black is applied to the photosensitive drums 10Y, 10M, 10C, and 10B shown in FIG. Output from a laser beam scanner (not shown) including a polygon mirror, etc.
Thereby, the photosensitive drums 10Y, 10M, 10C, 1
Each of the charged surfaces 0B is exposed to form an electrostatic latent image thereon. The laser beam output from the laser beam scanner is intensity-modulated in accordance with a time-series electric digital pixel signal of target image information, and the respective photosensitive drums 10Y, 10Y are scanned and exposed by the laser beam.
An electrostatic latent image corresponding to the target image information is formed on the outer peripheral surfaces of 0M, 10C, and 10B. In the digital writing method as in this embodiment, the writing amount of dots is counted when each photosensitive drum is exposed, and the writing density of the output image, in other words, the distribution of the image density is calculated. The information is sent to an operation sequence device (not shown).

Next, the developing unit will be described. The developing units 6Y, 6M, 6C and 6B are reversal developing devices having the same configuration except that only the color of the toner used is different. For example, the developing unit 6Y for yellow includes a developing roller 11 and a doctor blade as shown in FIG. It comprises 12, two first screws 13, a second screw 14, a toner density sensor 15 and an outer case 16. The developing roller 11
6, the first screw 13 and the second screw 14 are positioned obliquely downward from the developing roller 11 as shown in FIG. 6, and the first screw 13 and the second screw The two screws 14 are arranged in parallel in the horizontal direction. The outer case 16 is the first
It has a partition plate 16a that divides each room in which the screw 13 and the second screw 14 are stored, and the partition plate 16a is cut out so that the developer can circulate between the first screw 13 and the second screw 14. Has been.
In the outer case 16, an opening 16b is formed in a portion facing the photosensitive drum 10Y, and a part of the developing roller 11 is exposed from the opening 16b.

As described above, the outer case 16 includes the developing roller 1
The developing roller 11, the first screw 13, the second screw 14, and the doctor blade 12 are surrounded with a slightly larger space above the first screw 13 beside the first screw 13. The developing roller 11 has a magnet (not shown) serving as a magnetic field generating means fixed inside a rotatable non-magnetic developing sleeve. The developer is conveyed while being stirred, and is constantly circulating in two chambers having the first screw 13 and the second screw 14. Then, the developer circulated while being stirred and conveyed is supplied to the developing roller 11 by the first screw 13, is pumped up by the magnetic force of the magnet in the developing roller 11, and is held in a magnetic brush shape on the surface. The developer held by the magnetic brush is cut into appropriate amounts by the doctor blade 12 and sent to the developing section facing the photosensitive drum 10Y. The developer remaining after being cut off by the doctor blade 12 is
By gravity, the surface of the developing roller 11 falls off the outside of the magnetic brush shape, returns to the room where the first screw 13 is located, and is again supplied to the developing roller 11 while being stirred and conveyed again.

On the other hand, the developer, which is held in the form of a magnetic brush on the surface of the developing roller 11 and is sent to the developing unit, is visualized by attaching toner to the electrostatic latent image on the photosensitive drum 10Y. The developer not used for the visualization is the outer case 16
The portion where the magnetic force of the magnet in the developing roller 11 does not work is separated from the developing roller 11 and returned to the room where the first screw 13 is located and collected. As described above, the developer in the outer case 16 is supplied to the developing roller 11 while being stirred and conveyed by the first screw 13 and the second screw 14 and circulated.
Collected in 6. The developing unit 6Y detects the toner density in the outer case 16 by the toner density sensor 15 because the toner density gradually decreases when an image is repeatedly output, and the outer case 16 (Not shown).

Next, the developer will be described in detail. [One-component developer] The weight average diameter is measured by the following procedure. First, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution. Here, the electrolytic solution is prepared by preparing an approximately 1% NaCl aqueous solution using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter Inc.) is used. Here, two more measurement samples were taken.
Add ~ 20 mg. The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and a measuring apparatus using a 100 μm aperture as an aperture.
The volume distribution and the number distribution are calculated by measuring the volume and the number of the toner particles or the toner. From the obtained distribution, the weight average particle diameter (D4) and the number average particle diameter of the toner are determined. 1. 2.00 to less than 2.52 μm as a channel;
52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to 6.35.
6.35 to less than 8.00 μm; 8.00 to 1
Less than 0.08 μm; 10.08 to less than 12.70 μm;
12.70 to less than 16.00 μm;
Less than 20 μm; 20.20 to less than 25.40 μm; 2
5.40 to less than 32.00 μm; 32.00 to 40.3
Using 13 channels of less than 0 μm, particle size of 2.00 μm
m to less than 40.30 μm.

"Materials Constituting Developer" The description is such that one component or two components can be used. The ratio of the materials constituting the toner is as follows: the binder resin is 75% to 93%, and the colorant is 3% to 1%.
0%, release agent 3% ~ 8%, other components 1% ~ 7%
It is. Examples of the binder resin used include, for example, a homopolymer of styrene such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene and a substituted product thereof; a styrene-p-chlorostyrene copolymer and a styrene-vinyltoluene copolymer. Coalesce, styrene-vinylnaphthalene copolymer,
Styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl Examples include ether copolymers and styrene-vinyl methyl ketone. As the coloring agent, conventionally known inorganic or organic dyes / pigments can be used, and examples thereof include carbon black, aniline black, acetylene black, naphthol yellow, hansa yellow, rhodun lake, alizarin lake,
Bengala, phthalocyanine blue, and induslen blue. Note that a magnetic material can be used as a coloring agent if necessary. As the magnetic material,
Iron oxide such as magnetite, γ-iron oxide, ferrite iron, excess ferrite; magnetic metal such as iron, cobalt, nickel; iron oxide or magnetic metal, and cobalt, tin, titanium, copper, lead, zinc, magnesium, manganese , Aluminum, a composite metal oxide alloy with a metal such as silicon, or a mixture thereof.

These magnetic particles preferably have an average particle size in the range of 0.05 to 1.0 μm, more preferably in the range of 0.1 to 0.6 μm, and still more preferably 0.1 to 0.6 μm. It is preferable that the thickness be within a range of 0.4 μm.
These magnetic particles preferably have a BET specific surface area measured by a nitrogen adsorption method in the range of 1 to 20 m ² / g, particularly 2.5 to 2.5 m ² / g.
It is preferably in the range of 12 to 12 m ² / g, and more preferably the Mohs hardness is in the range of 5 to 7. Examples of the shape of the magnetic particles include an octahedron, a hexahedron, a sphere, a needle, and a scale, and an octahedron, a hexahedron, and a sphere having little anisotropy are preferable. When used as a magnetic toner, the magnetic toner particles containing the magnetic material may contain the magnetic material in an amount of 10 to 150 parts by mass, preferably 20 to 120 parts by mass, per 100 parts by mass of the binder resin.

In this toner, a small amount of an additive can be used within a range that does not substantially adversely affect the toner. Examples of the additives include lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder, and polyvinylidene fluoride powder; abrasives such as cerium oxide powder, silicon carbide powder, and strontium titanate powder;
Fluidity-imparting agents or anti-caking agents such as aluminum oxide powder; conductivity-imparting agents such as carbon black powder, zinc oxide powder and tin oxide powder; and organic or inorganic fine particles of opposite polarity. Further, a release agent may be added in order to improve the fixability and the like. As the release agent, paraffin wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives,
Examples include polyolefin wax and its derivatives, carnauba wax and its derivatives. The derivatives include oxides, block copolymers with vinyl monomers, and graft-modified vinyl monomers. In addition, alcohols, fatty acids, acid amides, esters, ketones, hydrogenated castor oil and derivatives thereof, vegetable waxes, animal waxes,
Mineral wax and petrolactam can also be used.

As the charge control agent for controlling the toner to be negatively charged, for example, organometallic complexes and chelate compounds are effective, and monoazo metal complexes, acetylacetone metal complexes,
An aromatic hydroxycarboxylic acid-based metal complex and an aromatic dicarboxylic acid-based metal complex are exemplified. Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, their anhydrides, their esters, and phenol derivatives such as bisphenol. Examples of the charge control agent for controlling the toner to have a positive charge include a modified product of nigrosine and a fatty acid metal salt; tributylbenzylammonium-1-hydroxy-4-naphthosulfonate;
Quaternary ammonium salts such as tetrabutylammonium tetrafluoroborate, and onium salts such as phosphonium salts, which are analogs thereof, and lake pigments thereof;
Triphenylmethane dyes and their lake pigments (as the lacking agent, phosphotungstic acid, phosphomolybdic acid,
Phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide)
There is. The number average particle diameter of the particulate charge control agent is preferably 4 μm or less, more preferably 3 μm or less. When these charge control agents are internally added to the toner particles, the toner particles are preferably from 0.1 to 20 parts by mass, more preferably from 100 parts by mass of the binder resin.
The content is preferably 0.2 to 10 parts by mass.

The toner may be, if necessary, an additive for toner generally used widely, for example, a fluidizing agent such as colloidal silica, a metal oxide such as titanium oxide or aluminum oxide, or an abrasive such as silicon carbide. And a lubricant such as a fatty acid metal salt. The inorganic fine powder is preferably used in an amount of 0.1 to 2% by weight based on the toner. If the amount is less than 0.1% by weight, the effect of improving toner aggregation is poor. If the amount is more than 2% by weight, problems such as toner scattering between fine lines, contamination inside the machine, scratches and abrasion of the photoreceptor tend to occur. is there. As a method for mixing the additives with the toner, a conventionally known method may be used, and the additives can be mixed with a device such as a Henschel mixer or a speed kneader. The method for producing the toner powder after kneading and cooling the toner may be a conventionally known method, for example, after kneading and cooling,
This is pulverized with a jet mill and classified.

The toner for developing an electrostatic charge image thus produced can be used as a dry one-component developer and a dry two-component developer. When used as a two-component developer, the mixing ratio of the toner and the carrier is generally about 0.5 to 6.0 parts by weight of the toner per 100 parts by weight of the carrier.
When used as a dry two-component developer, the amount of the carrier and the toner of the present invention is such that the toner particles adhere to the carrier surface of the carrier particles and have a surface area of 30 to 40%.
It is preferable to mix both particles so as to account for 90%.
As the core particles of the carrier constituting the developer, conventionally known particles may be used, for example, ferromagnetic metals such as iron, cobalt, and nickel; alloys and compounds such as magnetite, hematite, and ferrite; And the like.

It is preferable that the surface of such a carrier is coated with a resin for the purpose of increasing the durability. As a resin forming the coating layer, for example, polyethylene,
Polyolefin resins such as polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polystyrene, acrylic (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polybiriketone, etc. Polyvinyl chloride and vinyl acetate copolymers; vinyl chloride-vinyl acetate copolymers; silicone resins composed of organosiloxane bonds or modified products thereof (for example, modified products by alkyd resins, polyester resins, epoxy resins, polyurethanes, etc.); Fluororesins such as ethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyamides; polyesters; Urethane; polycarbonate;
Amino resins such as urea-formaldehyde resins; epoxy resins and the like. Of these, silicone resins or modified products thereof, and fluorine resins, particularly silicone resins or modified products thereof, are preferred in terms of preventing toner spent. As a method of forming the coating layer, a coating layer forming liquid may be applied to the surface of the carrier core particles by a method such as a spraying method and an immersion method, as in the related art. The thickness of the coating layer is preferably 0.1 to 20 μm.

[Two-Component Developer] Next, the two-component developer will be described in detail. Production Example 1 100 parts by weight of a polyester resin (weight average particle size 300 μm, softening temperature 80.2 ° C.), carbon black 10
Parts by weight and polypropylene (weight average particle size 180 μm)
5 parts by weight and 2 parts by weight of a quaternary ammonium salt are melt-kneaded, then pulverized and classified. Further, the base colored particles 10
0.3 parts by weight of hydrophobic silica is mixed with 0 parts by weight to obtain a toner having an average particle size of 9.0 μm. Further, 2 parts by weight of polyvinyl alcohol and 60 parts by weight of water were placed in a ball mill and mixed for 12 hours with respect to 100 parts by weight of magnetite prepared by a wet method to prepare a magnetite slurry. This slurry was spray-granulated with a spray drier to obtain spherical particles. The particles are placed in a nitrogen atmosphere for 100
After baking at a temperature of 0 ° C. for 3 hours, the mixture was cooled to obtain core particles 1.

A mixture of 100 parts by weight of the silicone resin solution, 100 parts by weight of toluene, 15 parts by weight of γ-aminopropyltrimethoxysilane, and 20 parts by weight of carbon black was dispersed with a homomixer for 20 minutes.
Was adjusted. This coating layer forming liquid was coated on a surface of 1,000 parts by weight of core particles 1 using a fluidized bed type coating apparatus to obtain a silicone resin-coated carrier.
97.5 parts by weight of the magnetic carrier and toner 2.
The mixture was mixed at a ratio of 5 parts by weight to prepare a two-component developer.

Next, the application of the developing bias will be described. In the developing unit 6Y shown in FIG. 6, an oscillating bias voltage obtained by superimposing an AC voltage on a DC voltage is applied as a developing bias from a power source (not shown) to the developing roller 11 during development. The non-image portion potential and the image portion potential are located between the maximum value and the minimum value of the vibration bias potential. As a result, an alternating electric field whose direction changes alternately is formed in the developing unit 17. The toner and carrier of the developer violently vibrate in the alternating electric field, and the toner shakes off the electrostatic restraining force on the developing roller 11 and the carrier, and the photosensitive drum 10
The toner flies to Y, and toner adheres to the latent image on the photosensitive drum 10Y. The difference (peak-to-peak voltage) between the maximum value and the minimum value of the vibration bias voltage is preferably 0.5 to 5 KV, and the frequency is preferably 1 to 10 KHz. As the waveform of the oscillation bias voltage, a rectangular wave, a sine wave, a triangular wave, or the like can be used. As described above, the DC voltage component of the vibration bias is a value between the background portion potential and the image portion potential. It is preferable from the viewpoint of preventing toner from adhering.

When the waveform of the oscillation bias voltage is a rectangular wave,
It is desirable that the duty ratio be 50% or less. Here, the duty ratio is a ratio of a time during which the toner goes to the photoconductor in one cycle of the vibration bias. By doing so, the difference between the peak value of the toner going to the photoreceptor and the time average value of the bias can be increased. It adheres faithfully to the distribution and can improve roughness and resolution. Also, since the difference between the peak value of the carrier having the opposite polarity to the toner and the time average value of the bias toward the photoreceptor can be reduced, the motion of the carrier is calmed down, and the background of the latent image is reduced. The probability that the carrier adheres to the portion can be greatly reduced.

Next, the cleaning of the photosensitive drum 10Y will be described. The surface of the photosensitive drum 10Y is cleaned by the cleaning unit 7. The cleaning unit 7 functions to remove the toner remaining on the photosensitive drum 10Y after the primary transfer.
In the example shown in FIG. 3, a cleaning blade 18 made of, for example, polyurethane rubber, a fur brush 19, and an electric field roller 21 disposed in contact with the fur brush 19 are provided.
And a scraper 22 of the electric field roller 21 and a collecting screw 23. In addition, fur brush 1
Reference numeral 9 denotes a conductive brush, and the electric field roller 21 is a metal roller. In the cleaning operation by the cleaning unit 7, the toner remaining on the photosensitive drum 10Y is first scraped off by the fur brush 19 rotating in the direction opposite to the rotation direction of the photosensitive drum 10Y. Electric field roller 2 rotating in a direction opposite to the rotation direction of fur brush 19
1 and the electric field roller 21 is cleaned by a scraper 22. At this time, a bias (not shown) is applied to the electric field roller 21, and the residual toner moves from the photosensitive drum 10 </ b> Y to the fur brush 19, from the fur brush 19 to the electric field roller 21 by electrostatic force, and finally to the scraper 22. Is scraped off and recovered screw 2
3, the toner is collected in a waste toner bottle (not shown) or returned to the developing unit 6Y for reuse.

Next, the charging device 1 will be described in detail. The charging device 1 shown in FIG. 3 performs constant current control with a power supply (not shown) to control the current flowing through the sawtooth electrode 2 to be constant. This is a so-called scorotron charging device that applies a voltage to the grid 36 so as to keep the potential of the photosensitive drum constant. The charging device 1 includes a resin back plate 39 between end blocks 37 and 38 provided at both ends of a charging casing 35.
Is fixed, and the sawtooth electrode 2 is held by the back plate 39 as shown in FIG. As shown in FIG. 3, a terminal 41 for applying a high voltage to the sawtooth electrode 2 is provided at one end of the back plate 39, and the terminal 41 can be pulled out to the left in FIG. I have. As described above, in the corona charging type charging device 1 having the sawtooth electrode 2, the charging device is provided between the sawtooth electrode 2 and the photosensitive drum in order to keep the surface of the photosensitive drum to be charged at a stable potential. 1 is provided with a metal grid 36 at a position closest to the photosensitive drum so as to maintain a desired potential.

The charging device 1 is provided with the cleaning device 3 for cleaning the saw-tooth electrode 2 by bringing the cleaning member 5 into sliding contact with the saw-tooth electrode 2 as described above. The cleaning device 3
It is roughly composed of three parts, and comprises a shaft 43 for supporting the entire cleaning device, a cleaning member 5 for cleaning the sawtooth electrode 2, and a grid cleaning member 44 for cleaning the grid 36. The shaft 43 is movably fitted in a direction indicated by an arrow C in a resin-made support end block 45 integrally formed at a lower portion of the end block 38. The grid cleaning members 44 are fixed respectively. Therefore, if the shaft 43 is moved right and left in FIG. 3, both the saw-tooth electrode 2a of the saw-tooth electrode 2 and the inner surface of the grid 36 can be cleaned. The cleaning member 5 and the grid cleaning member 44 are, for example, made of the same material and mainly made of foamed polyurethane having air bubbles therein, and have an insulating volume resistivity of 10 ⁵ Ω · m, preferably 10 ¹⁰ Ω · m. It is formed with a sponge exhibiting properties.

The cleaning member 5 is impregnated with a non-volatile silicone oil having a viscosity of 30 to 100 cSt, preferably 50 cSt, as a liquid 9 for reducing the friction between the cleaning member 5 and the sawtooth electrode 2. I have. Therefore,
When the cleaning member 5 is moved along the longitudinal direction of the sawtooth electrode 2, the liquid 9 containing silicon oil as a main component contained in the cleaning member 5 is applied to the surface of the sawtooth electrode 2 in a thin film form. become. The sawtooth electrode 2 has a base portion 2b for supporting and fixing the entire electrode, and a large number of sawtooth-shaped discharge electrodes 2a for performing discharge, as shown in a partially enlarged view in FIG. The cleaning member 5 includes
Cut 5 for sandwiching the sawtooth electrode 2 as shown in FIG.
a is formed. The cutout 5a sandwiches the electrode 2a on the tip side of the sawtooth electrode 2 from both sides. The grid cleaning member 44 fixed to the lower side of the shaft 43 is formed of a sponge of the same material as the cleaning member 5, but is not impregnated with silicon oil.

When the charging device 1 is discharging with the sawtooth electrode 2, the cleaning device 3 is on standby at a standby position outside the effective image area shown in FIG. In this state, since the cleaning member 5 that is in contact with the sawtooth electrode 2 has insulating properties, there is no influence on the discharging operation necessary for performing the image forming operation. Further, since the liquid 9 made of silicon oil impregnated in the cleaning member 5 also has an insulating property, it does not affect the discharge. In the charging device 1, the surface potential of the photosensitive drum is charged to +500 V, so that the grid 36 has +550 V and the sawtooth electrode 2
A voltage of 5.5 kV is applied by constant current control (+0.6 mA). Even when a high voltage is applied to the sawtooth electrode 2 to cause discharge, the cleaning member 5 is made of an insulating foamed polyurethane, so that there is no abnormal leakage of current. Therefore, the photosensitive drum can be favorably charged. When the cleaning member 5 has a low volume electrical resistance, the voltage applied to the sawtooth electrode 2 is applied to the cleaning member 5, so that the discharge state is not stable. As a result, the charging operation to the photosensitive drum is not performed normally.

As described above, in the charging device 1, a voltage of 5.5 kV is applied to the sawtooth electrode 2.
Even in a general image forming apparatus, the application of a voltage to the sawtooth electrode is often +4 k to +9 kV (the reverse polarity, also -4 k to -9 kV) in order to avoid abnormal discharge. Within the range, if the volume resistivity of the cleaning member 5 is set to have an insulating property of 10 ⁵ Ω · m or more, the occurrence of the abnormal discharge described above can be prevented. By the way, in corona wire charging using a fine wire, it is known that a silicon oxide compound accumulates on the wire as the discharge time increases, and that abnormal discharge is likely to occur. I have.
As in the charging device 1 according to this embodiment, the sawtooth electrode 2
The same is true for a charging device using a saw-tooth electrode 2.
If the sawtooth electrode 2 is not cleaned, the discharge will not be stable and the durability will be reduced.

Accordingly, in the charging device 1, the cleaning device 3 is provided as described above, and the shaft 43 is connected to the shaft C in FIG.
The electrode 2a on the tip side of the sawtooth electrode 2 can be cleaned only by moving the cleaning member 5 in the same direction. When the cleaning member 5 is moved in a state in which the cleaning member 5 is in contact with the saw-tooth electrode 2, the intended cleaning is not performed due to the effect of the frictional force generated by the rubbing between the cleaning member 5 and the saw-tooth electrode 2. Is also conceivable. However, in the charging device according to the present embodiment, as described above, the cleaning member 5 is impregnated with the viscous liquid 9 made of silicone oil, which also has a function as a lubricant.
When the cleaning member 5 is slid along the sawtooth electrode 2, the liquid 9 contained in the cleaning member 5 is thinly applied to the surface of the sawtooth electrode 2 to coat the surface of the sawtooth electrode 2. Therefore, it is possible to prevent foreign substances causing abnormal discharge from adhering to the electrode 2a and to protect the electrode 2a.

Therefore, even with a mechanical cleaning device that slides the cleaning member 5 along the sawtooth electrode 2 like the cleaning device 3, a stable cleaning effect is obtained and the mechanical durability is improved. Can also be planned. Further, since the viscous liquid (silicone oil) 9 impregnated in the cleaning member 5 has an insulating property as described above, it hardly affects the discharge. Further, since the liquid 9 is hardly volatile, it does not evaporate from the cleaning member 5 made of foamed polyurethane, so that it is not necessary to replenish the liquid every time cleaning is performed, which is convenient. In the case of an image forming apparatus that is frequently used and has a large number of output sheets, the frequency of cleaning the sawtooth electrode 2 by the cleaning member 5 increases. In such a case, the liquid (silicon oil) 9 is supplied. It is preferable to provide a device for performing the above. Further, the cleaning device 3 according to the above-described embodiment includes:
By manually moving the shaft 43, the cleaning member 5 is brought into sliding contact with the sawtooth electrode 2 to perform the cleaning operation.
A mechanism for automatically moving the shaft 43 in the pull-out direction may be provided.

As described with reference to FIG. 2, the sawtooth electrode 2 comprises a base 2b and a number of sawtooth-shaped electrodes 2a, and a portion necessary for charging the photosensitive drum is a tip-side electrode. This is only the portion 2a. In order to perform a good discharge, it is necessary to clean all of the electrodes 2a serving as the discharge portions. Therefore, the sliding range Wa of the cleaning member 5 of the cleaning device 3 with respect to the sawtooth electrode 2 is the length of the sawtooth in the protruding direction of the sawtooth of the plurality of discharge electrodes 2a formed in a sawtooth shape (direction of arrow E). The range is set to be longer than Lb. That is, the cleaning member 5 of the cleaning device 3
The depth La (corresponding to Wa) of the cut 5a, which is the cleaning range of the cleaning member 5, is set to the electrode (discharge portion) of the sawtooth electrode 2.
The length of the saw tooth 2a is longer than the length Lb. In this way, when only the tip of the electrode 2a is cleaned, abnormal discharge that occurs when foreign matter adheres to other portions may not be prevented, but the depth of the cut 5a of the cleaning member 5 may be reduced. By setting La to be longer than the length Lb of the electrode 2a of the sawtooth electrode 2, all the portions of the electrode 2a can be more reliably cleaned. As described above, even if the saw-tooth electrode 2 does not clean the base portion 2b, the base portion 2b has a flat plate shape and is located far from the photosensitive drum, so that a high voltage is applied thereto. The probability of occurrence of abnormal discharge is extremely low, and the probability of occurrence of abnormal discharge due to the adhesion of discharge products is high.
Part. Therefore, as described above, the cleaning member 5
By making the depth La of the notch 5a longer than the length Lb of the electrode 2a of the sawtooth electrode 2, the discharge product (foreign matter) adhered to the electrode 2a by the cleaning operation by the cleaning device 3
Is more likely to move or be removed from the electrode 2a, so that abnormal discharge is less likely to occur.

In the charging device 1 based on the scorotron charging system shown in FIG. 3, in order to make the surface potential of the photosensitive drum uniform, the magnitude of the voltage applied to the sawtooth electrode 2 and the grid 36 has the following relationship. I am trying to become. Vd: target photoreceptor surface potential Vg: grid potential Vc: voltage applied to the sawtooth electrode (monitoring the voltage output during constant current control) Vd <Vg <Vc (relation in absolute value) Specifically, Vd = −500 V, Vg = −55
0 V and Vc = -5.5 kV (Vd ≒ Vg may be satisfied). The discharge generally follows Paschen's law, but if the discharge body and the discharge body (charged body) are on the order of millimeters, no discharge occurs unless an absolute value of 4 kV or more is applied.

In this embodiment, the distance between the grid 36 and the photosensitive drum is 1.5 mm, and no discharge occurs at a grid potential of -550 V. Under such a state, the grid cleaning member 44 does not need silicon oil used for cleaning the sawtooth electrode 2. Rather, if the silicone oil is applied to the inner surface of the grid 36 by the grid cleaning member 44, the gaps arranged at regular intervals will be closed by the silicone oil, so that the charging of the photosensitive drum is normal. Will not be performed. Therefore, it is not preferable to impregnate the grid cleaning member 44 with silicon oil, like the cleaning member 5 used for cleaning the sawtooth electrode 2. Therefore, in the charging device 1, as shown in FIG. 1, the cleaning member 5 and the grid cleaning member 44 are vertically divided into two by the shaft 43, and the cleaning member 5 used for cleaning the sawtooth electrode 2 is made of silicon oil. A normal discharge is caused by impregnating with a liquid 9 made of and preventing the grid cleaning member 44 for cleaning the grid 36 from containing the liquid. The liquid 9 to be impregnated in the cleaning member 5 is made to have a viscosity, and is made to be non-volatile so as to be leaked to the outside by infiltrating into the sponge-like cleaning member 5. This prevents the liquid 9 from seeping out to the position of the grid cleaning member 44 on the grid 36 side (the outflow of the liquid 9 is prevented by the shaft 43). Also, as described above, the shaft 43
By fixing the cleaning member 5 and the grid cleaning member 44 on both sides of the surface, the sawtooth electrode 2 is cleaned by the cleaning member 5 and the grid 36 is cleaned by the grid cleaning member 44 by a single cleaning operation of moving the shaft 43. be able to. Therefore, the size of the cleaning device 3 can be reduced.

FIG. 7 is a schematic diagram showing an embodiment of a cleaning device provided with a brush type grid cleaning member, and portions corresponding to FIG. 3 are denoted by the same reference numerals. The cleaning device according to this embodiment is different from the cleaning device 3 illustrated in FIG. 3 only in that a brush type grid cleaning member 54 is provided instead of the sponge type grid cleaning member 44. The brush portion of the grid cleaning member 54 was a flocking type having a volume electric resistance of 10 ⁹ Ω · m, and was a flat material having a material of SA7 and a flocking density of 100,000 / inch ² . When the cleaning performance of the grid 36 was actually confirmed by this cleaning device, the same effect as in the case of the grid cleaning member 44 using the sponge was obtained. Therefore, for reference, when the same thing as the grid cleaning member 54 was replaced with the cleaning member 5 for the sawtooth electrode 2 and the cleaning property was confirmed, the same effect as in the case of the cleaning member 5 was not obtained. The reason is that, in the case of a brush, there is no closed air bubble inside, so that the liquid (silicone oil) 9 cannot be held in the cleaning member, so that the effect of applying the liquid 9 to the sawtooth electrode 2 is obtained. It is determined that this was not possible. From the above results, when the liquid 9 necessary for improving the cleaning performance of the sawtooth electrode 2 is required, a cleaning member made of a material having air bubbles therein is necessary, and the liquid 9 is not interposed. However, if a sufficient cleaning effect is obtained, that is, not only a sponge but also a brush-type grid cleaning member 54 for cleaning the grid 36, the same effect can be obtained.

The photosensitive drum used in this embodiment uses an a-Si (amorphous silicon) photosensitive member described with reference to FIGS. 5A to 5D. This a-Si has a higher surface hardness than OPC, and is a semiconductor laser (7) generally used in an image forming apparatus.
(70 to 800 nm). In addition, since deterioration due to repeated use is hardly recognized, the durability is excellent, and as a result, the durability of the image forming apparatus can be improved. In the case of such an a-Si photoreceptor, it is often performed by positive charging. When the discharge (image forming operation) is repeatedly performed in the positive charging corona charging, for example, a silicon compound, which is a discharge product, accumulates in a needle shape on the surface of the sawtooth electrode 2 described with reference to FIG. It is easy to cause abnormal discharge. Therefore, the surface of the sawtooth electrode 2 (particularly, the tip electrode 2a which greatly contributes to discharge)
Need to be cleaned.

At this time, if cleaning unevenness occurs, the sawtooth electrode 2
The abnormal discharge may cause abnormal discharge due to the deterioration of the surface state of the photoconductor, and the abnormal discharge may cause the photosensitive member to be easily broken. Therefore, special attention must be paid to the abnormal discharge. In particular, it is disadvantageous to increase the film thickness of the a-Si photosensitive member in the manufacturing process, and it is difficult to increase the potential by charging using the sawtooth electrode, and the discharge voltage is often increased, so that abnormal discharge easily occurs. So be careful. However, even if such an a-Si photoreceptor is used, in the charging device 1 according to the present embodiment, the cleaning member 5 for cleaning the sawtooth electrode 2 is impregnated with the liquid 9 made of silicon oil having a lubricating function to clean By applying the liquid 9 to the entire electrode 2a of the sawtooth electrode 2 during the cleaning operation by the device 3, the mechanical operation at the time of cleaning is stabilized. As a result, the durability of the charging device 1 is improved, and the cleaning performance of the cleaning device 3 is improved, so that abnormal discharge is less likely to occur. Therefore, the original high durability of the a-Si photoconductor can be obtained. The durability as a whole can be improved.
Further, since the cleaning device 3 does not rotate the cleaning member, the configuration can be simplified and the number of parts can be reduced by that much, so that the cost can be reduced. The cleaning range of the cleaning member 5 along the longitudinal direction of the photosensitive drum described with reference to FIG. 3 is longer than the length of the effective image forming area of the photosensitive drum. This makes it possible to reliably clean all portions of the sawtooth electrode corresponding to the effective image forming area.

[0048]

As described above, according to the present invention, the following effects can be obtained. According to the charging device of the first aspect, if the cleaning member of the cleaning device is moved to be in sliding contact with the sawtooth electrode, the liquid impregnated in the cleaning member is applied to the sawtooth electrode, so that the sawtooth electrode is formed. The frictional force between the electrode and the cleaning member is reduced, and the cleaning efficiency is increased. Therefore, the discharging operation can be performed in a stable state for a long time. In addition, since the cleaning device has a simple configuration that only moves the cleaning member, the size can be reduced. According to the charging device of the second aspect, since the liquid impregnated in the cleaning device is a non-volatile liquid having a viscosity of 30 to 100 cSt, the device is filled with the vaporized liquid component during the cleaning operation and the image forming operation. Never do. Further, since the liquid impregnated in the cleaning device does not evaporate, a high cleaning efficiency that is stable over a long period of time can be obtained. According to the charging device of the third aspect, since the liquid is a liquid containing silicon oil as a main component, it is possible to reduce deposition of a silicon oxide compound on an electrode during discharge in the atmosphere and maintain a stable discharge state. it can.

According to the charging device of the fourth aspect, the viscous liquid can be easily held in the bubbles of the cleaning member, and the action of the bubbles causes damage when the cleaning member slides on the sawtooth electrode. Therefore, the durability of the saw-tooth electrode itself can be improved. According to the charging device of the fifth aspect, since the cleaning member has an electric resistivity of 10 ⁵ Ω · m or more, there is no abnormal leakage of current during the discharging operation, so that good charging performance can be obtained. According to the charging device of the sixth aspect, the range of sliding contact of the cleaning member with the sawtooth electrode is a range longer than the length of the sawtooth in the protruding direction of the sawtooth of the plurality of discharge electrodes formed in a sawtooth shape. Therefore, it is possible to reliably clean all of the sawtooth-shaped discharge electrodes that greatly contribute to the discharge of the sawtooth electrode, and it is possible to prevent the occurrence of abnormal discharge caused by attached foreign matter.

According to the charging device of the present invention, since the cleaning range of the cleaning member is longer than the length of the effective image forming area of the image carrier, uneven cleaning of the saw-tooth electrode corresponding to the effective image forming area is achieved. All can be reliably cleaned so as not to occur. According to the charging device of the eighth aspect, when the cleaning operation is not performed, the cleaning member can be made to wait outside the effective image forming area, so that the cleaning member is formed in the effective image forming area when the sawtooth electrode is discharged. It is possible not to affect the latent image. According to the image forming apparatus of the ninth aspect, an image forming apparatus having excellent durability can be provided. Further, since the charging device can be made smaller than the corona wire type charging device, the entire image forming apparatus can be downsized. According to the image forming apparatus of the present invention, the photosensitive member has a high surface hardness, exhibits high sensitivity to long wavelength light such as a semiconductor laser, and hardly deteriorates due to repeated use. The overall durability can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a charging device according to the present invention.

FIG. 2 is an enlarged view showing a part of a sawtooth electrode provided in the charging device.

FIG. 3 is a configuration diagram of the charging device as viewed from the front.

FIG. 4 is a configuration diagram illustrating the vicinity of an image forming unit of an image forming apparatus including the charging device.

FIG. 5 is a schematic diagram schematically illustrating a layer configuration of an a-Si photoconductor.

FIG. 6 is a configuration diagram illustrating an image forming unit that forms a yellow image.

FIG. 7 is a schematic view showing an embodiment of a cleaning device provided with a brush type grid cleaning member.

[Explanation of symbols]

1: charging device 2: saw-tooth electrode 2a: electrode 3: cleaning device 9: cleaning member 9: liquid 10Y, 10M, 10C, 10B: photosensitive drum (image carrier)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H200 FA07 FA08 GA18 GA45 GA47 GB25 HA12 HA28 HB06 HB14 HB30 HB45 JC12 JC15 LB05 LB08 LB13 LB17 LB20 LB35 LB36 LB38 MA04 MA08 MA20 MB04

Claims (10)

[Claims] 1. A corona discharge type charging device in which a plurality of sawtooth-shaped discharge electrodes are charged in a non-contact manner by means of sawtooth electrodes arranged along the longitudinal direction of the image carrier. A cleaning device that cleans the saw-tooth electrode by bringing a cleaning member into sliding contact with the saw-tooth electrode, wherein the cleaning member is impregnated with a liquid that reduces friction between the cleaning member and the saw-tooth electrode. Charging device. 2. The liquid impregnated in the cleaning member is 30 to
2. The charging device according to claim 1, wherein the charging device is a non-volatile liquid having a viscosity of 100 cSt. 3. The charging device according to claim 2, wherein the liquid is a liquid containing silicon oil as a main component. 4. The charging device according to claim 1, wherein the cleaning member comprises a member having a large number of air bubbles therein, and holds the liquid by the air bubbles. . 5. The cleaning member has an electric resistivity of 10 ⁵ Ω ·
The charging device according to any one of claims 1 to 4, wherein the charging device is formed to have a length of m or more. 6. A range in which the cleaning member slides on the sawtooth electrode is longer than a length of the sawtooth in a protruding direction of the sawtooth of each of the plurality of discharge electrodes formed in a sawtooth shape. The charging device according to claim 1, wherein: 7. The image forming apparatus according to claim 1, wherein a cleaning range of the cleaning member along a longitudinal direction of the image carrier is longer than a length of an effective image forming area of the image carrier. The charging device according to claim 1. 8. The image forming apparatus according to claim 1, wherein the cleaning member is movable along a longitudinal direction of the image carrier to a standby position outside an effective image forming area of the image carrier.
The charging device according to claim 1. 9. An image forming apparatus equipped with the charging device according to claim 1. 10. The image forming apparatus according to claim 9, wherein the image carrier is an amorphous silicon-based photoconductor.