JP2002244401A - Electrifier and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems such as the occurrence of uneven electrification due to uneven coating of liquid film in applying liquid in order to electrify in a contact or close contact state, the occurrence of the deterioration of exposure sharpness and the intrusion of the coating liquid into a developing device, in an electrifier loaded onto an image forming device. SOLUTION: The electrifier 2 for electrifying the surface of a photoreceptor 1 to be charged by an electrifying member 22 with a voltage applied by bringing the photoreceptor 1 into close contact with the electrifying member 22, is provided with a liquid applying device 6 for supplying the liquid 64 between the photoreceptor 1 and the electrifying member 22, and the surface of the photoreceptor is electrified while holding the liquid 64 between the photoreceptor 1 and the electrifying member 22 at an electrifying process, and also, the electrifier is provided with a liquid removing device 8 for removing the liquid on the surface of the photoreceptor after the electrifying process, but, before an exposure process, then, the occurrence of uneven electrification is prevented, the sharpness of a latent image formed at the exposure process is maintained, and the liquid is prevented from intruding into the constitutional member for developing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging a member to be charged, and more particularly, to a charging device for charging a surface of a member to be charged by bringing a charging member to which a voltage is applied close to the member to be charged. The present invention relates to a charging device of the system. The present invention also relates to an image forming apparatus such as a copying machine, a printer, a plotter, and a facsimile, which uses the charging device as a charging unit for an image carrier as a member to be charged.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic system or an electrostatic recording system, an image carrier (a member to be charged) such as a photoconductor for electrophotography and a dielectric for electrostatic recording has a required polarity and potential. As a charging device for uniformly charging, a corona charger using corona discharge is often used. The corona charger is a non-contact type charging device, and includes, for example, a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode. The surface of the image carrier is charged in a predetermined manner by exposing the surface of the image carrier to a discharge current generated by applying a high voltage to the discharge electrode and the shield electrode.

However, recently, since there are advantages such as low ozone and low power as compared with a corona charger, as described above, a charging member to which a voltage has been applied to a member to be charged is brought into contact or non-contact to bring the member into contact. 2. Description of the Related Art Proximity-type charging devices for charging a charged body have been put to practical use. The proximity charging device contacts a member to be charged such as an image carrier with a conductive charging member such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type. Alternatively, a predetermined charging bias is applied to a contact charger (hereinafter, referred to as a contact charging member) to charge the surface of the member to be charged to a predetermined polarity and potential.

In this contact charging system, the charging mechanism (charging mechanism, charging principle) includes two types of charging mechanisms, a remote charging system and a direct injection charging system, each of which depends on which one is dominant. The characteristic of appears. The remote charging system is a system in which the surface of a member to be charged is charged with a discharge product due to a discharge phenomenon such as corona discharge, which is remote charging generated in a gap between the contact charging member and the member to be charged. Corona charging has a certain discharge threshold for the contact charging member and the charged object,
It is necessary to apply a voltage higher than the charging potential to the charging member. Further, although the amount of generation is significantly smaller than that of a general corona charger, it is difficult to avoid adverse effects due to active ions such as ozone since generation of discharge products is unavoidable in principle. For example, a roller charging system using a conductive roller (charging roller) as a contact charging member is preferably and widely used in terms of charging stability, but a corona charging system is dominant in the charging mechanism of the roller charging. .

[0005] The charging roller is made of a conductive or medium-resistance rubber material or a foamed material. In some cases, these are further laminated to obtain desired characteristics. The charging roller has elasticity in order to obtain a constant contact state with the member to be charged, but has a large frictional resistance, and in many cases, is driven by the member to be charged or driven with a slight speed difference.
Therefore, since a reduction in absolute charging ability, a lack of contact, unevenness on the roller, and uneven charging due to an adhered substance on the charged body are inevitable, the charging mechanism in the conventional roller charging is mainly a corona charging system. is there.

Therefore, in order to further uniform the charging, as disclosed in, for example, JP-A-63-149669, a DC voltage corresponding to a desired potential Vd of the member to be charged is reduced by 2 ×. An “AC charging method” is used in which a voltage obtained by superimposing an AC component having a peak-to-peak voltage of Vth or more is applied to the contact charging member. This is for the purpose of a smoothing effect of a potential caused by an alternating current, which is an oscillating potential.
It converges to d and is not affected by disturbances such as the environment.

However, even in such a contact charging device, the essential charging mechanism uses the phenomenon of discharging from the contact charging member to the member to be charged, and is required for charging as described above. The voltage applied to the contact charging member needs to be higher than the surface potential of the member to be charged, and a small amount of ozone is generated. Further, when AC charging is performed for uniform charging, further generation of ozone, generation of vibration noise (AC charging noise) between the contact charging member and the photoconductor due to the electric field of the AC voltage, and charging due to discharge. Deterioration of the body surface and the like became remarkable, and this was a new problem. To prevent the deterioration of the surface of the member to be charged when AC is applied, Japanese Patent Application Laid-Open No.
As disclosed in JP-A-15234, a liquid coating process is provided on the upstream side where discharge from a contact charging member to a member to be charged is performed, and the liquid coating has a thickness of 1 μm or less. This solves the problem of uneven charging due to uneven contact with the body surface.

[0008]

However, it is difficult to improve the problem of uneven charging while applying a liquid to the surface of the member to be charged with a thickness of 1 μm or less to reduce the thickness. It has been found by the inventors' earnest research. As a method for thinning a liquid having a thickness of 1 μm or less, a method in which the gap between the member to be charged and the coating member is directly reduced to 1 μm or less is directly conceivable. It was also found that it was difficult in practice because it required precision control technology and mechanical assembly technology. Furthermore, since the state of contact between the member to be charged and the charging member is not always the same, some non-contact portions also appear during the charging process, and charging stability is greatly lost. It was found that uneven charging became severe. In addition, when the liquid film becomes 1 μm or more, if the exposure is performed as it is, the sharpness of the latent image on the member to be charged is lost, and a problem such as deterioration of image quality occurs. When the liquid film is 1 μm or more,
In the development process of visualizing the visualized particles,
In addition to the inherent electrostatic movement of the toner as the visualized particles to the member to be charged, the toner also adheres to portions other than the image due to the adhesive force on the liquid surface. In addition, there was a problem that the liquid was mixed into the developing device.

The present invention has been made in view of the above circumstances, and in a charging device provided in an image forming apparatus, when a liquid is applied when performing proximity charging including contact.
An object of the present invention is to solve the problems of uneven charging due to uneven coating of a liquid film, deterioration of sharpness of exposure, and mixing of a coating liquid into a developing device. Still another object of the present invention is to provide an image forming apparatus using a proximity charging device, which is excellent in chargeability, has high environmental stability, and can stably output a high-quality image.

[0010]

According to the first aspect of the present invention, there is provided a charging device used in an image forming apparatus for forming an image through respective steps of charging, exposing, developing, and transferring. A charging device for bringing the member to be charged close to the member to be charged and charging the surface of the member to be charged by a charging member to which a voltage is applied, comprising a means for supplying a liquid between the member to be charged and the charging member. In the charging step, the surface of the member to be charged is charged in a state where the liquid is sandwiched between the member to be charged and the charging member, and the liquid is removed after the charging step and before the exposing step. It is characterized by having a device.

According to a second aspect of the present invention, in the charging device according to the first aspect, the liquid interposed between the member to be charged and the charging member is a liquid containing silicon oil as a main component. . According to a third aspect of the present invention, in the charging device according to the first or second aspect, the liquid interposed between the charged member and the charging member is 50 c.
It is a liquid having a viscosity of St or more.

According to a fourth aspect of the present invention, in the charging device according to any one of the first, second, and third aspects, the liquid removing device may have a resistance of 10 ⁷ Ω · cm or more at a portion in contact with the member to be charged. It is characterized by. According to a fifth aspect of the present invention, in the charging device according to the first, second, third, or fourth aspect, the contact member of the liquid removing device that contacts the member to be charged has a blade shape. Features.

In the invention according to claim 6, according to claims 1, 2, 2
6. The charging device according to 3, 4, or 5, wherein the charging member has a roller shape. According to a seventh aspect of the present invention, in the charging device according to the first, second, third, fourth, or fifth aspect, the charging member has a blade shape. Further, in the invention according to claim 8, in the charging device according to claim 6, the closest distance between the charging member and the member to be charged is 10
It is characterized by being arranged within 0 μm. According to a ninth aspect of the present invention, in the charging device of the sixth aspect, the charging member includes a cleaning mechanism.

According to the tenth aspect of the present invention, after the image bearing member to be charged is charged by charging means, the image bearing member is exposed to light to form a latent image, and the latent image is developed by developing means. After developing and visualizing, in an image forming apparatus that forms an image by transferring the visible image on the image carrier to a transfer material by a transfer unit,
As a charging means for charging an image carrier which is a member to be charged, the charging device according to any one of claims 1 to 9 is used. According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, the image carrier is an amorphous silicon (a-Si) photoconductor.

According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth or eleventh aspect, the developer used in the developing means has a weight average diameter of 4 to 15 μm. According to a thirteenth aspect of the present invention, in the image forming apparatus according to the tenth aspect, when the latent image on the image carrier is developed, an alternating electric field is applied.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure, operation and operation of the present invention will be described below in detail with reference to the illustrated embodiments.

Embodiment 1 FIG. 1 is a schematic structural view of an image forming apparatus showing an embodiment of the present invention. The image forming apparatus shown in FIG. 1 is a laser printer using a transfer type electrophotographic process and using a charging unit of a proximity charging type. After an image carrier 1 as a member to be charged is charged by a charging unit 2, The image carrier 1 is exposed to laser light L1 from an optical writing device (not shown) to form a latent image, and the latent image is developed with a developer 31 of a developing unit 3 to become a visible image. The visible image on the body is transferred to a transfer material P such as recording paper as a recording medium by a transfer means 4 to form an image, and the image transferred to the transfer material P is fixed by a fixing means 5 and output. I do. Further, the surface of the image carrier after the image transfer is cleaned by the cleaning unit 7.

In the image forming apparatus shown in FIG. 1, a charging means 2 brings an image carrier 1 as a member to be charged into close proximity with a charging member 22, and charges the surface of the image carrier 1 by a charging member 22 to which a voltage is applied. A charging device for supplying a liquid 64 between the image carrier 1 and the charging member 22 (specifically, applying a liquid to the surface of the image carrier) upstream of a charging step (charging process). A liquid coating device) 6 for charging the surface of the image carrier with a liquid sandwiched between the image carrier 1 and the charging member 22 during the charging process, and before the exposure process (exposure process) after the charging process. A liquid removing device 8 for removing the liquid 64 on the surface of the image carrier is provided. The printer according to the present embodiment performs a reversal development type development process. As the image carrier 1, amorphous silicon (a-S) is formed on the surface of a conductive drum.
An amorphous silicon photoconductor in which i) is laminated is used. Hereinafter, the printer having the configuration shown in FIG. 1 will be described more specifically.

<< Outline of the Overall Configuration and Operation of the Printer of the Present Embodiment >> [Image Carrier] In FIG. 1, the image carrier 1 to be charged is a rotating drum type electrophotographic photosensitive member. The photoconductor 1 of the embodiment is an amorphous silicon (a-Si) photoconductor having a diameter of 100 mm and charged to a positive polarity, and is rotationally driven with a peripheral speed of 300 mm / sec in a clockwise direction indicated by an arrow in the drawing. Is done.

[Charging Means] The charging means 2 is a proximity roller charger using a roller-shaped charging member 22 disposed close to the photosensitive member 1, and the charging member 22 is a medium-resistance charging member serving as a proximity charging member. Roller. Charging roller 22 of this example
Is provided with a rubber layer having a hardness of 50 degrees according to JIS-A on the core metal 21, and the resistance between the shaft and the roller surface is 10 ⁷ Ω.
A cm roller was used. The surface of the roller is coated with fluorine so that the surface is not affected by silicone oil as a coating solvent.

[Charging Application Conditions] In FIG. 1, V1 is a charging bias power supply for the proximity roller charger 2, and in this embodiment, the power supply V1 is applied to the core 21 of the proximity charging roller 22, and the photosensitive drum 1 is rotated. Outer surface is almost + 700V
A charging bias is applied so as to be uniformly charged.
Note that the bias applied to the charging roller 22 to uniformly charge the surface of the photoconductor to +700 V is actually +
1.5 kV was required.

[Exposure / Latent Image Formation] An unillustrated optical writing device (laser beam scanner) including a laser diode, a polygon mirror, and the like is output to the charged surface of the photosensitive member 1 charged by the charging process. The scanning exposure is performed by the laser beam L1 to be performed. The laser beam L1 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 outer periphery of the photoconductor 1 which is rotated by scanning exposure with the laser beam L1. An electrostatic latent image corresponding to the target image information is formed on the surface.

[Developing Means] The developing means 3 is a reversal developing device, and a developing sleeve 32 of a developing roller 33
Is carried and conveyed, and the electrostatic latent image on the photoconductor 1 is reversely developed. That is, the electrostatic latent image formed on the outer peripheral surface of the rotating photoconductor 1 is reversely developed by the developer 31 carried and conveyed by the developing sleeve 32, and a developer image (toner image)
As a visible image.

[Developer] Here, the developer 31 used in the developing device 3 of the image forming apparatus according to the present embodiment will be described.

(One-component developer) The weight average diameter is measured according to the following procedure. First, the aqueous electrolytic solution 100-1
In 50 ml, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersant. Here, the electrolytic aqueous solution is prepared by preparing an approximately 1% NaCl aqueous solution using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of the measurement sample is further added. The electrolytic aqueous solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the volume and the number of the toner particles or the toner are measured by the measuring device using a 100 μm aperture as an aperture. Calculate volume distribution and number distribution. From the obtained distributions, the weight average particle diameter of the toner (D4), can be determined and the number average particle diameter.

As channels, 2.00 to 2.52
less than 2.5 μm; less than 2.52 to 3.17 μm;
4. less than 4.00 μm; 4.00 to less than 5.04 μm;
04 to less than 6.35 μm; 6.35 to less than 8.00 μm; 8.00 to less than 10.08 μm; 10.08 to 1
2.70 μm or less; 12.70 to less than 16.00 μm;
16.00 to less than 20.20 μm; 20.20 to 25.
Less than 40 μm; 25.40 to less than 32.00 μm; 3
Thirteen channels of 2.00 to less than 40.30 μm are used, and particles having a particle size of 2.00 μm or more to less than 40.30 μm are targeted.

"Materials Constituting Developer" The description is such that one component or two components can be used. Description will be made in the order of toner → carrier. Hereinafter, materials such as a binder resin and a colorant that constitute the toner will be described. The percentage of the total toner is 75% to 93% for the binder resin, 3% to 10% for the colorant, and 3% for the release agent.
% To 8%, and other components are 1% to 7%.

Examples of the binder resin to be used include, for example, homopolymers of styrene and its substituted substances such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyl Toluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, Styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone and the like can be mentioned.

As the colorant, conventionally known inorganic or organic dyes / pigments can be used. For example, carbon black, aniline black, acetylene black,
Naphthol Yellow, Hansa Yellow, Lodamun Lake, Alizarin Lake, Bengala, Phthalocyanine Blue, Indazulene Blue.

Further, if necessary, a magnetic material can be used as a coloring agent. Examples of the magnetic material include iron oxides such as magnetite, γ-iron oxide, ferrite iron, and excess ferrite; magnetic metals such as iron, cobalt, and nickel; iron oxides or magnetic metals, and cobalt, tin, titanium,
Examples thereof include a composite metal oxide alloy or a mixture with a metal such as copper, lead, zinc, magnesium, manganese, aluminum, and silicon. These magnetic particles have an average particle size of 0.0
It is preferably within a range of 5 to 1.0 μm, more preferably within a range of 0.1 to 0.6 μm, and still more preferably within a range of 0.1 to 0.4 μm.

These magnetic particles are made of B by a nitrogen adsorption method.
The ET specific surface area is preferably in the range of 1 to 20 m ² / g, particularly in the range of 2.5 to 12 m ² / g, and more preferably the Mohs hardness is in the range of 5 to 7. The shapes of the magnetic particles include octahedron, hexahedron, sphere,
There are needles and scales, but octahedrons, hexahedrons, and spheres with little anisotropy are preferred. When used as a magnetic toner, the magnetic toner particles containing a magnetic material are
10 to 150 parts by mass, preferably 20 to 100 parts by mass
It is preferable to contain up to 120 parts by mass of a magnetic material.

In the toner used in the image forming apparatus of the present invention, a small amount of an additive can be used within a range that does not substantially adversely affect the toner. Examples of the additive include lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder, and polyvinylidene fluoride powder; cerium oxide powder,
Abrasives such as silicon carbide powder and strontium titanate powder; fluidity-imparting agents such as titanium oxide powder and aluminum oxide powder or anti-caking agents; 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 releasing agent may be added to improve the fixing property and the like. Examples of the release agent include paraffin wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives, polyolefin wax and its derivatives, and carnauba wax and its derivatives. 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 waxes, and petrolactam can also be used.

Next, the charge control agent will be described. 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, aromatic hydroxycarboxylic acid-based metal complexes, aromatic dicarboxylic acid-based metals Complexes. 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 controlling agent for controlling the toner to have a positive charge include denaturation products of nigrosine and fatty acid metal salts; tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate. Quaternary ammonium salts,
And onium salts such as phosphonium salts, which are analogs thereof, and their lake pigments, triphenylmethane dyes, and these lake pigments (as the lake-forming agent, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid) Lauric acid, gallic acid, ferricyanide, ferrocyanide).

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 0.1 to 20 parts by mass, more preferably 0.2 to 10 parts by mass, based on 100 parts by mass of the binder resin. It is good to contain by mass.

The toner produced according to the present invention may contain, if necessary, a generally used toner additive such as a fluidizing agent such as colloidal silica, titanium oxide,
Metal oxides such as aluminum oxide, abrasives such as silicon carbide, and lubricants such as fatty acid metal salts may be contained.
The inorganic fine powder is preferably used in an amount of 0.1 to 2% by weight based on the toner. If it is less than 0.1% by weight, the effect of improving toner aggregation is poor. If it exceeds 2% by weight,
There is a tendency that problems such as toner scattering between the fine lines, contamination inside the machine, scratches and abrasion of the photoreceptor, and the like occur.

As a method of mixing the additives into the toner,
A conventionally known method may be used, and mixing can be performed by a device such as a Henschel mixer or a speed kneader. As a method for producing a toner kneading and cooling after the toner powder may be a conventionally known method, for example, by kneading and cooling, which was ground with a jet mill, obtained by classifying.

The toner for developing an electrostatic image produced by the present invention 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 used is such that the toner particles adhere to the carrier surface of the carrier particles and have a surface area of 30 to 90%.
%, It is preferable to mix both particles. In the present invention, the core particles of the carrier constituting the developer may be conventionally known ones, for example, ferromagnetic metals such as iron, cobalt and nickel; alloys and compounds such as magnetite, hematite and ferrite; A composite of fine particles and a resin is exemplified.

The carrier used in the present invention is preferably coated on its surface with a resin for the purpose of increasing the durability. Examples of the resin forming the coating layer include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene;
Polyvinyl and polyvinylidene-based resins such as polystyrene, acrylic (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polybiriketone; vinyl chloride-vinyl acetate copolymer A silicone resin comprising an organosiloxane bond or a modified product thereof (for example, a modified product of an alkyd resin, a polyester resin, an epoxy resin, a polyurethane, etc.); polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene Polyamide; Polyester; Polyurethane; Polycarbonate; Amino resin such as urea-formaldehyde resin; Epoxy resin It is. Among them, preferred are silicone resins or modified products thereof and fluororesins in terms of preventing toner spent, and particularly preferred are silicone resins or modified products thereof. 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. Further, the thickness of the coating layer is preferably 0.1 to 20 μm.

(Two-Component Developer) Next, a two-component developer will be described as an example of the developer. Hereinafter, a production example as a two-component developer will be described.

Manufacturing Example 100 parts by weight of a polyester resin (weight average particle diameter 300 μm, softening temperature 80.2 ° C.)
A mixture having a composition of 10 parts by weight of carbon black, 5 parts by weight of polypropylene (weight average particle size: 180 μm), and 2 parts by weight of a quaternary ammonium salt was melt-kneaded, then pulverized and classified. Further, based on 100 parts by weight of the base colored particles,
0.3 parts by weight of hydrophobic silica was mixed, and the average particle size was 9.0 μm.
m was obtained. 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. Then, this slurry was spray-granulated with a spray drier to obtain spherical particles. The particles were calcined in a nitrogen atmosphere at a temperature of 1000 ° C. for 3 hours and then cooled to obtain core particles.

Next, 100 parts by weight of the silicone resin solution,
A mixture having a composition of 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 to prepare a coating layer forming liquid. This coating solution was coated on the surface of 1,000 parts by weight of the core particles using a fluidized bed type coating apparatus to obtain a silicone resin-coated carrier. 2.5 parts by weight of the toner was mixed with 97.5 parts by weight of the magnetic carrier to prepare a two-component developer.

[Method of Applying Bias] Next, a method of applying a developing bias will be described. In the developing device 3 in the image forming apparatus of the present embodiment shown in FIG. 1, during development, a vibration bias voltage in which an AC voltage is superimposed on a DC voltage is applied to the developing roller 33 as a developing bias by a power source V2. 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 section b. In this alternating electric field, the toner and the carrier of the developer 31 vibrate violently, and the toner shakes off the electrostatic restraining force on the developing sleeve 32 and the carrier, flies to the rotating photosensitive drum 1, and the photosensitive drum 1 The toner adheres to the latent image.

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. However, a value closer to the background portion potential than the image portion potential is more likely to cover the background portion potential region. 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, so that the movement of the toner is further activated, and the potential of the toner on the latent image surface is 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.

[Transfer Means] In FIG.
The transfer roller is a medium-resistance transfer roller serving as a contact transfer unit. The transfer roller is pressed against the rotating photoconductor 1 at a predetermined pressure to form a transfer nip portion c. A transfer material P as a recording medium is supplied to the transfer nip c from a paper supply unit (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 4 from a transfer bias power supply V3. so,
The developer image on the rotating photoconductor 1 is sequentially transferred onto the surface of the transfer material P fed to the transfer nip c. The transfer roller 4 used in the present embodiment has a roller resistance of 5 × 10 ⁸ Ω in which a medium resistance foam layer 42 is formed on a core metal 41, and a DC voltage of −2.0 kV is applied to the core metal 41. And transfer was performed. The transfer material P introduced into the transfer nip portion c is nipped and conveyed by the transfer nip portion c, and a developer image formed and carried on the surface of the photoconductor 1 is sequentially charged on the front surface side of the transfer material P by an electrostatic charge. It is transferred by force and pressing force.

[Fixing Means] In FIG.
This is a fixing device such as a heat fixing system including a heating roller and a pressure roller. The transfer material P fed to the transfer nip c of the transfer roller 4 and receiving the transfer of the developer image on the photoconductor 1 side is
After being separated from the surface of the photoreceptor 1 and introduced into the fixing device 5, the developer image is fixed at the nip portion between the heating roller and the pressure roller, and is discharged out of the device as an image formed product (print, copy). .

[Photoconductor Cleaning Means] In FIG. 1, the cleaning means 7 is a cleaning device for cleaning the surface of the photoconductor 1. After the transfer of the developer image to the transfer material P, the contaminants such as transfer residual toner remaining on the photoreceptor surface are removed from the cleaning member 7 of the cleaning device 7.
1 (in this example, a cleaning blade made of urethane rubber which is in contact with the surface of the photoconductor 1), is scraped off and cleaned, and is repeatedly provided for image formation. The transfer residual toner and the like scraped off from the surface of the photoconductor 1 by the cleaning blade 71 are collected in the cleaner container 72 of the cleaning device 7.

[Liquid Coating Apparatus] In FIG. 1, a liquid coating apparatus 6 for coating a liquid 64 on the surface of the photoreceptor 1 has a
An application roller comprising a sponge roller for applying a thin layer of silicone oil, which is an insulating liquid, to the surface of the photoreceptor 1;
The photoconductor 1 is disposed in contact with the photoconductor 1 at a position between the charging roller 22 as a proximity charging member and the photoconductor cleaning device 7. The application roller 6 is composed of a cored bar 61 and a sponge roller unit 62 provided concentrically outside the cored bar 61. The sponge roller unit 62 contains silicon oil as the liquid 64, and rotates following the photosensitive member 1. Then, silicone oil is applied to the outer peripheral surface of the rotating photoconductor 1.
The application roller 6 is not limited to the driven type, and may be configured to rotate by a drive different from that of the photoconductor 1.

In this embodiment, the surface of the photoreceptor 1 has a viscosity of 100 by the sponge roller 62 of the coating roller 6.
A non-volatile silicon oil 64 of cSt is applied. The silicone oil to be applied is not particularly limited as long as it has a viscosity that does not exhibit volatility. If a general silicone oil has a viscosity of 50 cSt or more, it does not show volatility, so that a problem that the silicon oil remains in the apparatus does not occur. Therefore, the viscosity is desirably 50 cSt or more. The thickness of the layer of silicon oil applied to the outer peripheral surface of the rotating photoconductor 1 is adjusted so that the coating roller 6 has a film thickness of about the closest gap distance between the charging roller 22 and the photoconductor 1.
Is set to the contact pressure of the photosensitive member 1. Further, a dropping device 65 is disposed near the upper portion of the application roller 6 so as to appropriately replenish the silicone oil, and the silicone oil 64 in the dropping device 65 is dropped onto the sponge roller portion 62 of the application roller 6 through a vinyl tube 63. It is supposed to.

As described above, since the insulating liquid 64 made of silicone oil is applied to the photoreceptor 1 by the application roller 6, the silicon oil which is the liquid to be applied to the surface of the used photoreceptor 1 penetrates. It is preferable to have a hard surface layer because a high quality image can be obtained for a long period of time. Here, when the photoreceptor 1 is an a-Si photoreceptor, it is the most suitable photoreceptor in this system because it has high corrosion resistance to silicon oil. Also, an organic compound-based photoconductor, so-called OPC
However, there is no problem if there is an organic substance in the surface layer that is not affected by the surface layer by silicon oil. Alternatively, a photoreceptor having a surface layer of a resin that is not affected by silicone oil can be used on the surface layer of the photoreceptor.

[Function and Effect of Liquid Application] The photosensitive member 1 is brought into close proximity with the charging roller 22 by the charging roller 2 which is a proximity charging member, and the surface of the photosensitive member is close to the charging roller 22 in the charging nip portion a which is the closest part of the photosensitive member 1. The roller is charged by discharging, but if the surface of the roller is uneven with respect to the surface of the photoreceptor, the discharging is not performed uniformly. Even if the distance approaching the photoconductor surface is not uniform,
Silicon oil 64, which is an insulating liquid, is applied to the surface of the photoreceptor 1 by the application roller 6 to form a thin layer of the silicon oil 64. As the proximity charging roller 22 serving as a charging member approaches the photoconductor 1, electric charges are diffused in a silicon oil layer on the surface of the photoconductor 1 and electric charges are also discharged to a region on the photoconductor 1 where discharge was insufficient. Wraparound and sufficient charging is performed, so that uneven charging does not occur.

The silicone oil 64 applied to the surface of the photoreceptor 1 is generally an insulator. However, in a thin layer having a thickness of 100 μm or less, a discharge occurs between the photoreceptor 1 and the charging roller 22 to cause a charging process. Is performed. However, in the case of a liquid film having a thickness of 100 μm or more, even if the potential applied to the charging roller 22 is increased, the uneven charging is not eliminated. As a result, the transfer material P becomes uneven in toner concentration, and the phenomenon of uneven charging appears. . Therefore,
At the time of image formation by the printer, the silicone oil application roller 6, which is an application device, is kept separated from the photoreceptor 1 to apply the silicone oil to the photoreceptor 1 only. Is applied to apply silicone oil to the photoconductor 1 by contacting the photoconductor 1 with the photoconductor 1. However, even in this case, there is an effect of eliminating uneven charging.

In the configuration shown in FIG. 1, the proximity charging roller 2 is provided with a sponge-like cleaning member 23 for removing excess silicon oil. The sponge-like cleaning member 23 contacts the sponge on the proximity charging roller 22 and incorporates oil after the discharge to remove excess oil to prepare for the next charging process. Even when a commonly used blade is used as this cleaning member, there is an effect of liquid removal, and the effect is more efficient than a sponge. However, since the charging roller 22 passes through the liquid of the silicon oil 64 with respect to the photoreceptor 1, there is a possibility that the charging roller 22 rotates by entrainment. . In an apparatus configuration in which the proximity charging roller 22 can be driven separately from the photoconductor 1, a blade can be used as a cleaning member on the charging roller.
Blade cleaning is more desirable because it is more effective in removing the liquid.

[Liquid Removal Apparatus] The liquid removal apparatus 8 for removing the liquid (silicone oil) 64 on the photoreceptor surface after the charging process and before the exposure process is located downstream of the proximity charging roller 22 as shown in FIG. Thus, it was arranged on the upstream side of the exposure position of the laser beam L1. As the liquid removing device 81, a blade (hereinafter, referred to as a liquid removing blade) is the simplest and cost effective as the liquid removing member 81 that actually contacts the photoconductor 1 and removes the silicon oil 64 applied by the applying roller 6. It is the best from the viewpoint of.

In general cleaning of the photosensitive member, there is a cleaning method in which a fur brush is rotated to make contact with the photosensitive member 1. However, since silicon oil 64, which is a viscous liquid, is applied to the photosensitive member 1, The function does not work effectively with the removal of the liquid by the fur brush. Further, with a fur brush, abrasion marks appear on the liquid surface, which is not preferable because it causes image unevenness in the next exposure and development steps. In addition, in photoconductor cleaning, there is a method of cleaning by bringing a roller into contact with the surface of the photoconductor, but in this case, the photoconductor and the roller-shaped liquid removing member come into contact with each other and the liquid removing roller rotates. Also, a phenomenon such as slippage of silicon oil occurs, which is not preferable. Also, in this case, the roller-shaped liquid removing member needs to be pressed against the photoreceptor with a constant pressure, so that the roller supporting device becomes large, and the number of components increases as the liquid removing device. It is not desirable. Therefore, as the liquid removing member 81, a liquid removing blade is most optimal.

When a blade is used as the liquid removing member,
The contact direction of the liquid removing blade 81 is a counter direction with respect to the rotation direction of the photoconductor 1 rotating in the direction of the arrow in the figure as shown in FIG. This is because, as described above, the silicon oil layer on the photoreceptor 1 after the charging process is likely to cause the liquid to pass through in the trailing direction. Therefore, as shown in FIG.
It is desirable that the contact direction of the liquid removing blade 81 is a counter direction with respect to the rotation direction of the photoconductor 1. In addition, the liquid removing blade 81 must have a high resistance at least at a portion that comes into contact with the photoconductor 1. This is because, if the conductivity of the contact portion is high, the charged potential on the photoconductor may travel through an energizable region in the liquid removing blade 81, and the potential may decrease. Therefore, the liquid removing device 8
It is desirable that the liquid removing blade 81 has a high resistance of 10 ⁷ Ω · cm or more at a portion in contact with the photoreceptor 1.
0 using a urethane rubber blade indicating a high resistance ^{12 Ω} · cm.

Below the liquid removing blade 81 is disposed a container 82 for collecting excess silicon oil. The liquid removing blade 81 needs to be longer than the effective image area, and a seal (not shown in FIG. 1) is attached to the blade end to prevent silicon oil from leaking from the blade end. In the image forming apparatus shown in FIG. 1, when the image forming process is performed, a liquid pool is formed by the liquid removing blade 81 and the seal, but the silicon oil is stored in the container 82 by utilizing the liquid flowing down on the blade due to gravity. . Also, due to mechanical restrictions, the container 82
If it is not possible to place the lower part of the liquid removing blade 81, a tube or the like may be used to flow into the container. However, in this case, it may be difficult to flow due to the viscosity of the silicon oil, so it is desirable to forcibly suck up the silicon oil using a pump.

An image forming process was performed by operating the above-described liquid removing device, and an image was output. As a result, an image having a sharp boundary between an image portion and a non-image portion could be obtained. In addition, a high-resolution dot image such as a halftone image was obtained.

[Comparison with the case where no silicone oil is applied] In the case of the printer of the first embodiment except that the silicone oil application device 6 is omitted, when an image is output, the proximity charging roller 22 and the photosensitive member 1 are output. A streak-like image was generated due to the proximity state to the image. Further, image unevenness, which is considered to be due to the state (grinding line) of the surface of the charging roller, also occurred. As a result, even when the charging roller 22 not interposed with the liquid and the photoreceptor 1 are in contact with each other (the air layer is in the vicinity of the charging nip), the image unevenness is reduced to a lesser degree.

On the other hand, the silicone oil coating device 6
When a thin layer of silicone oil 64 is applied and formed on the surface of the rotating photoconductor 1 and the distance between the proximity charging roller 22 and the photoconductor 1 is set to 30 μm (the liquid film is 30 μm), the first embodiment is performed. With this printer, it was possible to output a good image without black streaks caused by uneven contact. Further, in this state, the silicon oil liquid film immediately after being applied by the silicon oil application roller 6 was 70 μm, but the liquid 64 was regulated between the proximity charging roller 22 and the photoconductor 1 as shown in FIG. It was found that the charging was performed in the state where the charging was performed. However, even in such a state, no unevenness appears on the image.

[Effects of the liquid removing device] Next, when the liquid removing device 8 is not operated and the image when the liquid removing device 8 is operated is compared, when the liquid removing device 8 is not operated, It was found that the sharpness of the boundary between the non-image portion and the image portion was reduced. In addition, toner is scattered near the boundary,
It was found that the potential was very unstable. In addition, some dots were not output for the dot image, and the resolution was reduced. The reason for the decrease in the stability of the potential is that the laser light L1
It is presumed that the exposure performed in step (1) was diffused and did not reach the potential that should have dropped. In particular, it is considered that the potential of the dot image changes due to the highlight, and the fluctuation of the potential becomes slow because the exposure amount is transmitted to some extent. Therefore, in the case of a configuration in which silicon oil is applied to the surface of the photoconductor before the charging process, it is necessary to operate the liquid removing device 8 for removing the silicon oil on the surface of the photoconductor after the charging process and before the exposure process. When the device 8 was operated, the above problem was solved.

[Embodiment 2] Next, as another embodiment of the present invention, a configuration in which a charging member of a charging device is shaped like a blade will be described. FIG. 2 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention. In the configuration of FIG.
As compared with the image forming apparatus of the first embodiment, only the charging member of the charging device 2 is changed from a proximity charging roller to a blade (hereinafter, charging blade 24), and other configurations and operations are the same as those in FIG. It is. Therefore, the description of the configuration and operation other than the charging member is omitted here.

The charging member of the charging device 2 is
Is different from the charging roller 22 of the first embodiment in that the charging blade 24 requires a certain length, and it is very difficult to set the closest distance to about 100 μm. . The reason is that the blade is an elastic body, so-called "sagging" occurs due to gravity, and a certain distance in a minute range cannot be maintained. Therefore, the blade-shaped charging member is less expensive than the roller, but is disadvantageous in maintaining the distance from the photoconductor. However, when the charging blade 24 was used, it was found that charging unevenness did not occur by bringing the tip of the blade into contact with the rotating photoreceptor 1 and applying silicon oil 64 as a liquid during that time. In this case, silicone oil 6
4 is applied, as described above, the silicone oil always intervenes between the photoreceptor 1 and the charging blade 24 due to the liquid permeability, and is similar to the charging roller described above. Discharge occurs. Therefore, even when the charging blade 24 is used, the same operation and effect as those of the charging roller can be obtained.
The output image was not uneven. It is considered that the reason for this is that the contact property between the photoconductor 1 and the charging blade 24 is increased with the silicon oil 64 interposed therebetween, and as a result, discharge uniformity was obtained.

There are two directions of contact of the charging blade 24, that is, a counter and a trailing direction. Generally, in the cleaning of the photosensitive member, a problem occurs in the trailing direction in order to prevent the toner from passing through. However, the present invention includes the liquid removing device 8 before the exposure process even in the trailing direction. Therefore, even if the silicon oil 64 slips through, there is no problem since the silicon oil is removed by the liquid removing device 8. In the blade-shaped charging member 24, the photosensitive member 1
Since the position of the contact portion does not fluctuate greatly, there is no problem even if the cleaning function provided by the roller charging system is not provided.

In this embodiment, as the charging blade 24,
Although a urethane rubber blade having a resistance of 10 ⁷ Ω · cm was used, the result was the same as that of the proximity charging roller described above. This urethane rubber blade has conductive carbon dispersed in the urethane rubber.

As described above, in the image forming apparatus of the present invention, the surface of the photoreceptor to be charged is coated with silicon oil, which is an insulating liquid, in a thin layer having a thickness of 100 μm or less. The charge applied to the member to be charged by the proximity charging member can prevent uneven charging due to unevenness in the proximity state of the proximity charging member to the photoreceptor surface, and after charging while applying the liquid, silicon oil which is an insulating liquid The liquid removal device removes the liquid on the photoreceptor without lowering the potential, so that in the subsequent exposure process, the sharpness of potential fluctuation due to diffusion in the writing exposure coating liquid is reduced. Therefore, a high-quality image in which the boundary between the image portion and the non-image portion is sharp was able to be output.

In the past, the image deletion was prevented by forming a liquid film having a very high accuracy of 1 μm or less, but in the present invention, a liquid film of 100 μm or less is formed. Even if the accuracy was mechanically reduced to suppress the accuracy or the accuracy was reduced due to environmental fluctuation, a good image could be output by the arrangement of the liquid removing device. Further, even when the fine uniformity of the liquid film is deteriorated, the effect does not affect processes such as exposure and development, and a high quality image with high environmental stability can be stably output.

[0070]

As described above, according to the first aspect of the present invention, there is provided a charging device used in an image forming apparatus for forming an image through respective steps of charging, exposure, development, and transfer,
A charging device for bringing a member to be charged and a charging member close to each other and charging a surface of the member to be charged by a charging member to which a voltage is applied, comprising: a unit for supplying a liquid between the member to be charged and the charging member; At the time of the process, a liquid removing device for charging the surface of the charged object with the liquid sandwiched between the charged object and the charging member, and for removing the liquid on the surface of the charged object after the charging step and before the exposure step. Since the liquid is interposed between the member to be charged and the charging member during the charging step, it is possible to prevent the occurrence of uneven charging,
After the charging step, the liquid is removed before the exposure step, so that the sharpness of the latent image formed at the time of exposure can be maintained, and furthermore, the liquid can be prevented from being mixed into the components that perform the development step, and as a result, It is possible to improve not only the image quality but also the durability.

According to a second aspect of the present invention, in the charging device according to the first aspect, the liquid interposed between the charged member and the charging member is a liquid containing silicon oil as a main component. In addition to the effects of the first aspect, the discharge phenomenon in the charging process can be stably performed. According to a third aspect of the present invention, in the charging device according to the first or second aspect, the liquid interposed between the charged member and the charging member is a liquid having a viscosity of 50 cSt or more. Therefore, in addition to the effects of claim 1 or 2, for example, the liquid interposed between the member to be charged and the charging member is made of silicone oil as a main component, has a viscosity of 50 cSt or more, and has non-volatility. The liquid component can be prevented from leaking to the device, and as a result, a stable image forming process can be performed.

According to a fourth aspect of the present invention, in the charging device according to any one of the first to third aspects, the liquid removing device has a resistance of 10 ⁷ Ω · cm or more at a portion in contact with the member to be charged. Therefore, in addition to the effects of claims 1, 2 and 3, the exposure process can be performed without affecting the surface potential of the member to be charged, and as a result, the image quality can be improved. it can. Claim 5
According to the invention according to the first aspect, in the charging device according to any one of the first to third aspects, the contact member of the liquid removing device that contacts the member to be charged has a blade shape. In addition to the effects of the first, second, third or fourth aspect, it is possible to remove the liquid remaining on the member to be charged most simply and reliably.

According to the sixth aspect of the present invention,
The charging device according to 3, 4 or 5, wherein the charging member has a roller shape.
In addition to the effects of the first, second, third, fourth or fifth aspect, the operation of the member to be charged and the operation of the charging roller as the charging member can be made to follow, and a stable discharge state can be formed. In the invention according to claim 7, in the charging device according to claim 1, 2, 3, 4, or 5, the charging member has a blade shape. , 3, 4 or 5, the charging process by discharge can be performed at the lowest cost. Further, in the invention according to claim 8, in the charging device according to claim 6, the closest distance between the charging member and the member to be charged is 10
Since they are arranged within 0 μm, in addition to the effect of the sixth aspect, in the charging process, the applied bias can be extracted most effectively, and uneven charging due to insufficient potential can be reduced. Furthermore, in the invention according to claim 9, in the charging device according to claim 6,
Since the charging member is provided with a cleaning mechanism, in addition to the effects of claim 6, the surface of the roller is stabilized by the fact that the liquid applied to the charging member does not permanently remain on the roller surface. As a result, a stable charging process can be performed.

According to the tenth aspect of the present invention, after the image bearing member to be charged is charged by the charging means, the image bearing member is exposed to light to form a latent image, and the latent image is developed by the developing means. After developing and visualizing, in an image forming apparatus that forms an image by transferring the visible image on the image carrier to a transfer material by a transfer unit,
Since the charging device according to any one of claims 1 to 9 is used as a charging unit for charging an image carrier that is a member to be charged, the charging device according to any one of claims 1 to 9 is used. The same effect is obtained, excellent in chargeability and high environmental stability,
It is possible to provide an image forming apparatus using a proximity charging device capable of stably outputting a high-quality image. In the invention according to claim 11, the image forming apparatus according to claim 10 is characterized in that the image carrier is an amorphous silicon (a-Si) photosensitive member. In addition, it is possible to reduce the damage due to the contact of the developer carrying member constituting the developing means and the deterioration due to oil absorption and expansion due to oil, and it is possible to extend the life of the electrostatic latent image carrying member. .

According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth or eleventh aspect, the developer used in the developing means has a weight average diameter of 4 to 15 μm. In addition to the effect of item 10 or 11, the resolution of the obtained image can be improved. In the invention according to claim 13, claim 10, 1
13. The image forming apparatus according to claim 1, wherein when developing the latent image on the image carrier, an alternating electric field is applied. When a latent image on the image carrier is developed, a vibration bias voltage in which an AC voltage is superimposed on a DC voltage is applied, so that a high-definition image without roughness can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus showing one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus showing another embodiment of the present invention.

FIG. 3 is a view schematically showing a state in which a film thickness of a liquid supplied between a member to be charged and a proximity charging roller is regulated by a charging roller in the image forming apparatus shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor (image carrier (charged member)) 2 charger (charging unit) 3 developing device (developing unit) 4 transfer roller (transfer unit) 5 fixing device (fixing unit) 6 liquid coating device 7 photoconductor cleaning device (Cleaning unit) 8 Liquid removing device 21 Core bar 22 Charging roller (Charging member) 23 Cleaning member 24 Charging blade (Charging member) 31 Developer 32 Developing sleeve 33 Developing roller 41 Core bar 42 Foam layer 61 Core bar 62 Sponge roller unit 63 Tube 64 Liquid (silicone oil) 65 Dropping device 71 Photoconductor cleaning member 72 Cleaner container 81 Liquid removal blade (liquid removal member) 82 Container L1 Laser beam V1 Charging bias power supply V2 Developing bias power supply V3 Transfer bias power supply

Claims (13)

[Claims] 1. A charging device used in an image forming apparatus for forming an image through respective steps of charging, exposing, developing, and transferring, wherein a charged member and a charging member are brought close to each other, and a voltage is applied to the charging member. A charging device for charging the surface of the member to be charged by means of: comprising means for supplying a liquid between the member to be charged and the charging member, and interposing the liquid between the member to be charged and the charging member during the charging step. A charging device, comprising: a liquid removing device that charges a surface of a member to be charged in a state and removes a liquid on the surface of the member to be charged after the charging step and before an exposure step. 2. The charging device according to claim 1, wherein the liquid sandwiched between the member to be charged and the charging member is:
A charging device comprising a liquid containing silicon oil as a main component. 3. The charging device according to claim 1, wherein the liquid sandwiched between the member to be charged and the charging member is:
A charging device comprising a liquid having a viscosity of 50 cSt or more. 4. The charging device according to claim 1, wherein the liquid removing device has a resistance of at least 10 ⁷ Ω · cm at a portion contacting the object to be charged. . 5. The charging device according to claim 1, wherein the contact member of the liquid removing device that contacts the member to be charged includes:
A charging device having a blade shape. 6. The charging device according to claim 1, wherein said charging member has a roller shape. 7. The charging device according to claim 1, wherein the charging member has a blade shape. 8. The charging device according to claim 6, wherein the closest distance between the charging member and the member to be charged is 100 μm.
m. A charging device, wherein the charging device is arranged within m. 9. The charging device according to claim 6, wherein the charging member includes a cleaning mechanism. 10. An image bearing member, which is a member to be charged, is charged by charging means, and then the image bearing member is exposed to light to form a latent image, and the latent image is developed by developing means to form a visible image. An image forming apparatus for forming an image by transferring a visible image on an image carrier to a transfer material by a transfer unit after forming the image carrier, wherein the charging unit for charging the image carrier, which is the member to be charged, is provided. An image forming apparatus using the charging device according to any one of the above items 9 to 9. 11. An image forming apparatus according to claim 10, wherein said image bearing member is an amorphous silicon (a-Si) photosensitive member. 12. The image forming apparatus according to claim 10, wherein the developer used for said developing means has a weight average diameter of 4 to 4.
An image forming apparatus having a thickness of 15 μm. 13. The image forming apparatus according to claim 10, wherein an alternating electric field is applied when developing the latent image on the image carrier.