JP2006201488A - Charging apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging apparatus having high durability, with no occurrence of rust or the like, scarcely impaired for the controllability of the charged potential even when contaminants such as toner are deposited more or less, stably controlling the charged potential on a photoreceptor in an appropriate range for a long time and being inexpensive as well. <P>SOLUTION: The charging apparatus 24 includes a needle electrode 50, a holding member 51, two cleaner members 52a and 52b, a support member 53, a moving member 54, a shield case 55, and a plate grid 56. In the charging apparatus 24, a nickel plating layer containing polytetrafluoroethylene particles is formed on the surface of the needle electrode 50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile, a photoconductor having a photosensitive layer containing a photoconductive material formed on the surface is used as an image carrier, and a charge is applied to the surface of the photoconductor. After being charged uniformly, an electrostatic latent image corresponding to image information is formed by various image forming processes, and this electrostatic latent image can be developed with a developer supplied from a developing means and containing toner. An image is formed on the recording paper by transferring the visible image onto a recording material such as paper, and then applying heat and pressure by a developing roller to fix the image on the recording material.

  In such an image forming apparatus, a charging device is used to charge the surface of the photoreceptor. The charging device is provided with an electrode for performing corona discharge on the photoconductor and, if necessary, between the surface of the photoconductor and the amount of charge applied to the surface of the photoconductor by the electrode, and thus the photoconductor. It is configured to include a grid that is an electrode for controlling the charging potential of the surface, and a support member that supports the electrode and the grid. Since the grid can control the charging potential on the surface of the photoconductor almost accurately, a charging device provided with a grid is now becoming mainstream. As the grid, a wire grid made of stainless steel, tungsten, or the like, a perforated plate grid in which a large number of through holes are formed in a metal plate (grid base material) made of stainless steel, or the like is used.

  As the electrode for the charging device, a wire electrode, a metal plate electrode having a plurality of needle-like portions (hereinafter referred to as “needle-like electrodes”), or the like is used. Among these, a needle-like electrode having advantages such as few component parts, long life, little ozone generation, and few failures because disconnection does not occur is preferably used. The acicular electrode is produced by etching a metal plate mainly made of an iron-based metal material such as stainless steel to form a plurality of acicular portions. The needle-shaped electrode produced by etching is also called an etching electrode. The etching cross section of this needle-like electrode lacks smoothness, and there are a plurality of edges for discharging at the tip of the needle-like part, and the shape of the edge existing at the tip of the plurality of needle-like parts Are uneven, the discharge of each needle-like part becomes non-uniform. As a result, the charged potential on the surface of the photoreceptor cannot be sufficiently controlled, and the charged potential on the surface of the photoreceptor becomes nonuniform.

  In addition, iron-based metal materials such as stainless steel, which are the materials for needle electrodes, have high durability, but are easily oxidized by moisture in a high humidity environment, ozone generated by corona discharge during charging operation, and the like. Has drawbacks. And when using an acicular electrode for a long time, use in a high-humidity environment, contact with ozone, etc. cannot be avoided. For this reason, in a needle electrode made of a metal material such as stainless steel, corrosion occurs due to moisture in the air, ozone, and the like, and the durability of the needle electrode decreases. At the same time, the ability to control the high voltage applied to the needle-like electrode due to corona discharge from the needle-like portion is reduced, the charge potential on the surface of the photoreceptor becomes uneven, and the desired charge potential is always stably maintained. There is a problem to be solved that cannot be applied to the surface.

  The wire electrode also has the same problem to be solved as the needle electrode in which rust and corrosion are generated by ozone generated by corona discharge, and the charged potential on the surface of the photosensitive member becomes non-uniform.

  In view of the above-described problems in the charging device, for example, a charging device including a wire electrode stretched in a shield case whose one surface is open, and a plate-like grid disposed between the wire electrode and the photosensitive member In the charging device, the plate-like grid is formed by forming a nickel plating layer having a thickness of about 1 μm on the surface of a stainless steel porous plate and further forming a gold plating layer having a thickness of about 0.3 μm thereon. It has been proposed (see, for example, Patent Document 1). The plate-like grid of Patent Document 1 forms a gold plating layer through a nickel plating layer, so that the gold plating layer is difficult to peel off, and the corrosion resistance and controllability of the charged potential on the surface of the photoreceptor are relatively good. . However, since it is essential to manufacture the plate grid through two plating steps, nickel plating and gold plating, there is a disadvantage that the manufacturing process becomes complicated and costs increase. In addition, in order for the plate-like grid to sufficiently exhibit the preferable characteristics as described above, the thickness of the gold plating layer needs to be 0.3 μm or more. In addition, since the plate-like grid is a relatively large member having substantially the same dimensions as the photosensitive member, the amount of gold used inevitably increases in combination with the fact that the plating layer must be thickened. However, such heavy use of gold raises the price of the charging device and thus the image forming apparatus more than necessary, and impairs versatility due to the relatively low price, which is one of the advantages of the image forming apparatus. Is. Therefore, a charging device having needle-like electrodes and plate-like grids that are excellent in durability and controllability of the charging potential on the surface of the photoreceptor without using expensive materials such as gold is desired.

  Similarly to Patent Document 1, a charging device including a wire electrode and a plate-like grid in which a gold plating layer is directly formed on the surface of a stainless steel metal plate by an electrolytic plating method using a pulse current has been proposed ( For example, see Patent Document 2). In this plate-like grid, the gold plating layer is not easily peeled off, and like the plate-like grid of Patent Document 1, the corrosion resistance is high and the charge potential controllability on the surface of the photoreceptor is also good. However, this plate-like grid also has the same defects as the charging device of Patent Document 1 because the thickness of the gold plating layer needs to be 0.3 μm or more.

  On the other hand, it has also been proposed to cover the electrode with gold (see, for example, Patent Document 3). The charging device of Patent Document 3 includes a needle electrode having a coating layer made of gold, platinum, copper, nickel, or chromium formed on the surface thereof by plating. In Patent Document 3, although methods such as etching and precision press are used for forming the needle-like electrode, as described above, the cross-section of the needle-like electrode obtained by these methods lacks smoothness and has fine irregularities. Arise. For this reason, even if plating is performed, fine unevenness in the cross section remains as it is, and the balance of corona discharge is disturbed, causing the charged potential on the surface of the photoreceptor to be non-uniform. Also, contaminants such as toner are likely to adhere to the fine irregularities. That is, the needle-shaped electrode of Patent Document 3 has a drawback that contaminants such as toner adhere due to long-term use, and this causes the charged potential on the surface of the photoreceptor to become more uneven.

Japanese Patent Laid-Open No. 11-40316 JP 2001-166669 A JP 2004-4334 A

  It is an object of the present invention to have high durability, and even if a contaminant such as toner adheres to some extent, the controllability of the charging potential is hardly impaired, and the charging potential of the photoconductor is appropriately adjusted over a long period of time. An object of the present invention is to provide a charging device that can be stably controlled within a range, can easily remove adhering contaminants, and is inexpensive, and an image forming apparatus that includes the charging device and can record high-quality images over a long period of time.

The present invention has a plurality of sharp protrusions, an electrode for applying a voltage to the surface of the photoconductor to charge the surface, and a charge potential on the surface of the photoconductor provided between the electrode and the photoconductor In a charging device including a plate-like grid that
The charging device is characterized in that a nickel plating layer containing polytetrafluoroethylene is formed on at least one surface of an electrode.

  The charging device of the present invention is characterized in that the nickel plating layer containing polytetrafluoroethylene is formed by an electroless plating method.

  Further, the charging device of the present invention is characterized in that the nickel plating layer containing polytetrafluoroethylene has a thickness of 0.3 μm or more.

  Furthermore, the charging device of the present invention is characterized in that a nickel plating layer is further formed between the electrode and a nickel plating layer containing polytetrafluoroethylene.

  Furthermore, the charging device of the present invention is characterized in that the nickel plating layer containing polytetrafluoroethylene contains phosphorus as a plating component together with nickel.

The present invention also provides a photosensitive member on which an electrostatic charge image is formed, a charging device for charging the surface of the photosensitive member, and an electrostatic charge by irradiating the charged photosensitive member surface with signal light based on image information. An exposure unit that forms an image; a developing unit that develops an electrostatic image formed on the surface of the photoreceptor to form a toner image; a transfer unit that transfers the toner image to a recording material; An image forming apparatus including a fixing unit that fixes a toner image.
An image forming apparatus, wherein the charging device is any one of the above-described charging devices.

  According to the present invention, a plate-like electrode (hereinafter referred to as a “needle-like electrode”) having a plurality of sharp projections and applying a voltage to the surface of the photoreceptor, polytetrafluoroethylene is applied to the surface. A nickel electrode layer containing a nickel electrode layer (hereinafter referred to as a “nickel PTFE composite plating layer” unless otherwise specified) and a surface of the photoconductor surface provided between the needle electrode and the photoconductor. There is provided a charging device including a plate-like grid for controlling an electric potential. The acicular electrode has a plurality of sharp protrusions and the surface thereof is coated with a nickel PTFE composite plating layer, so that it has excellent corona discharge performance on the surface of the photoreceptor, and charging of the surface of the photoreceptor. The electric potential can be uniformly controlled within an appropriate range. The acicular electrode has high durability and can stably exhibit the above-described charge potential controllability over a long period of time. Further, the needle-like electrode is coated with a nickel PTFE composite plating layer on its surface, so that contaminants such as toner adhering to the surface can be easily removed by a general cleaning means. Therefore, an image forming apparatus including a charging device having the needle-like electrode can record a high quality image over a long period of time. Furthermore, since the needle electrode is not a gold plating layer as in the prior art but a nickel plating layer containing polytetrafluoroethylene formed on the surface of the base material, it is less expensive than the conventional needle electrode. It has the advantage of being.

  According to the present invention, the nickel PTFE composite plating layer of the needle electrode is formed by an electroless plating method, so that the structure is denser than that of the nickel PTFE composite plating layer obtained by a normal electrolytic plating method using a direct current. The nickel PTFE composite plating layer that is hard, has few pinholes, is uniform even if the layer thickness is thin, and has high adhesion to the needle-like electrode, and smoothes the rough surface. The charge potential controllability and durability of the electrode plate are further improved. Further, contaminants such as toner are difficult to adhere.

  According to the present invention, by setting the thickness of the nickel PTFE composite plating layer on the needle electrode plate to 0.3 μm or more, the charge potential controllability and durability of the needle electrode plate are reliably exhibited.

  According to the present invention, in a needle-like electrode, a nickel plating layer is formed between the needle-like electrode base material and the nickel PTFE composite plating layer, whereby the nickel PTFE composite plating layer is peeled from the needle-like electrode base material. Is further prevented, and the durability as a needle-like electrode is further improved. Therefore, it is possible to obtain a charging device capable of stably controlling the charging potential on the surface of the photoreceptor for a longer period.

  According to the present invention, in the needle-shaped electrode, the nickel PTFE composite plating layer contains phosphorus as a plating component together with nickel, whereby the adhesion of the plating layer to the needle-shaped electrode substrate is improved, and the needle-shaped electrode plate As a result, the durability is further improved.

  According to the present invention, a nickel PTFE composite plating layer is formed on the surface of an image forming apparatus including a photosensitive member, a charging device, an exposure device, a developing device, a transfer device, and a fixing device as a charging device. By using the charging device of the present invention having an acicular electrode formed as described above, the charged potential on the surface of the photoconductor when forming an electrostatic latent image can be stably maintained within an appropriate range. Since an image quality image can be recorded and no gold plating layer is provided unlike the prior art, an inexpensive image forming apparatus can be obtained.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus 1 according to a first embodiment of the present invention. FIG. 2 is a perspective view schematically showing a configuration of a charging device 24 according to another embodiment of the present invention.

  The image forming apparatus 1 is a multifunction machine having both a copying function, a printer function, and a facsimile function. That is, the image forming apparatus 1 has three types of printing modes, ie, a copier mode (copying mode), a printer mode, and a FAX mode, and an operation input from an operation unit (not shown) or an external host device such as a personal computer. In response to the reception of the print job, a print mode is selected by a control unit (not shown).

  The image forming apparatus 1 stores a recording medium and feeds the recording medium to an image forming unit 3 described later, an image forming unit 3 that forms an image on the recording medium, and a paper discharge unit 4. A document reading unit 5 that reads an image and / or characters described on a copy document, converts the information into an electrical signal, and transmits the electrical signal to the image forming unit 3.

  The paper supply unit 2 conveys the recording media stored in the paper supply trays 10, 11, 12, and 13 and the paper supply trays 10 to 13 to the image forming unit 3. First and second transport paths 14 and 15, a frame 16 that accommodates and protects the paper feed trays 10 to 13 and the first and second transport paths 14 and 15, and a manual feed portion that is provided above the frame 16 17.

  The paper feed trays 10 to 13 can accommodate recording media of different sizes and / or types for each tray, for example. Here, the size means, for example, a size such as A3, A4, B4, and B5 defined in JIS P 0138 or JIS P 0202. Moreover, it is not limited to these sizes, An irregular-shaped recording medium can also be accommodated. On the other hand, the type means recording paper such as plain paper, color copy paper, OHP film, and the like. Of course, the paper feed trays 10 to 13 can accommodate the same size and the same type of recording medium.

  The paper feed trays 10 and 11 are arranged in parallel with each other, the paper feed tray 12 is arranged below them, and the paper feed tray 13 is arranged below them. For example, the supply of the recording medium to the paper feed trays 10 to 13 is performed by pulling out the paper feed trays 10 to 13 to the front side (operation side) of the image forming apparatus 1.

  The first transport path 14 is provided so as to extend along the frame 16 of the paper feed unit unit 2 in a substantially vertical direction that is perpendicular to the installation surface 100 of the image forming apparatus 1. , 13 is fed to the image forming unit 3. Further, the second transport path 15 is provided so as to extend in a substantially horizontal direction parallel to the installation surface 100 of the image forming apparatus 1 along the frame of the paper feed unit unit 2. The stored recording medium is fed to the image forming unit 3.

  As described above, the paper feed trays 10 to 13 and the first and second transport paths 14 and 15 are efficiently arranged in the frame 16 of the paper feed unit unit 2, thereby realizing space saving.

  The manual feed portion 17 is provided above the frame 16, and includes a manual feed tray 18, paper feed rollers 19 a and 19 b for taking a recording medium supplied to the manual feed tray 18 into the image forming apparatus 1, and a second conveyance path. 15 and a manual feed path 20 for feeding a recording medium taken into the image forming apparatus 1 by the paper feed rollers 19a and 19b to the image forming unit 3.

  The manual feed tray 18 is fixed to the upper side of the frame 16 inside the image forming apparatus 1, and a part thereof is provided so as to protrude outward from the side surface 1 a of the image forming apparatus 1. The manual feed tray 18 is provided so as to be housed inside the image forming apparatus 1. A recording medium is supplied from the manual feed tray 18 into the image forming apparatus 1.

  The paper feed rollers 19a and 19b are provided so as to be in pressure contact with each other and to be rotatable around an axis by driving means (not shown). The recording medium supplied from the manual feed tray 18 to the pressure contact portions of the paper feed rollers 19a and 19b is sent to the manual feed path 20 by the rotational drive of the paper feed rollers 19a and 19b.

  The manual feed path 20 is provided so as to penetrate the frame 16 and connect to the second transport path 15. The recording medium sent to the manual feed path 20 by the paper feed rollers 19 a and 19 b passes through the second transport path 15 and is fed to the image forming unit 3.

  According to the manual feed section 17, the recording medium supplied from the manual feed tray 18 is sent to the manual feed path 20 by the paper feed rollers 19 a and 19 b and further sent to the image forming section 3 via the second transport path 15. It is done.

  In the paper feed unit 2, when an image is formed on a recording medium, a tray for storing a recording medium of a predetermined size and type is selected from the paper feeding trays 10 to 13, and the tray is selected from the tray. The recording media are separated one by one, and the separated recording media are fed to the image forming unit 3 via either the first conveyance path 14 or the second conveyance path 15 and image formation is performed. Alternatively, the recording medium supplied from the manual feed unit 17 is similarly fed to the image forming unit 3 and image formation is performed.

  The image forming unit 3 transfers the toner image formed corresponding to the image data to the recording medium, and fixes the toner image transferred onto the recording medium in the electrophotographic process unit 21 to the recording medium. And the fixing unit 22 to be configured.

  The electrophotographic process unit 21 includes a photosensitive drum 23, a charging device 24, an optical scanning unit 25, a developing unit 26, a developer storage unit 27, a transfer unit 28, and a cleaning unit 29. The

  The photosensitive drum 23 is supported by a driving means (not shown) so as to be rotatable around an axis, and is not shown in the figure, a cylindrical, columnar or thin film sheet, preferably cylindrical conductive substrate, and the surface of the conductive substrate. And a photosensitive layer formed thereon.

  As the conductive material for the conductive substrate, those commonly used in this field can be used. For example, aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold Metals such as platinum, two or more kinds of these alloys, synthetic resin films, metal films, and paper-like substrates such as aluminum, aluminum alloys, tin oxide, gold, indium oxide, etc. Examples thereof include a conductive film formed by forming a conductive layer, a resin composition containing conductive particles and / or a conductive polymer. In addition, as a film-form base | substrate used for an electroconductive film, a synthetic resin film is preferable and a polyester film is especially preferable. Moreover, as a formation method of the electroconductive layer in an electroconductive film, vapor deposition, application | coating, etc. are preferable.

  The photosensitive layer is formed, for example, by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. In that case, it is preferable to provide an undercoat layer between the conductive substrate and the charge generation layer or the charge transport layer. By providing an undercoat layer, the scratches and irregularities present on the surface of the conductive substrate are coated to smooth the surface of the photosensitive layer, to prevent deterioration of the chargeability of the photosensitive layer during repeated use. Alternatively, the advantage of improving the charging characteristics of the photosensitive layer in a low humidity environment can be obtained.

  The charge generation layer is mainly composed of a charge generation material that generates a charge when irradiated with light, and contains a known binder resin, plasticizer, sensitizer and the like as necessary. As the charge generation material, those commonly used in this field can be used, for example, perylene pigments such as perylene imide and perylene acid anhydride, polycyclic quinone pigments such as quinacridone and anthraquinone, metal and metal-free phthalocyanines, and halogenated compounds. Phthalocyanine pigments such as metal-free phthalocyanine, squalium dye, azulenium dye, thiapyrylium dye, carbazole skeleton, styryl stilbene skeleton, triphenylamine skeleton, dibenzothiophene skeleton, oxadiazole skeleton, fluorenone skeleton, bis stilbene skeleton, distyryl oxa And azo pigments having a diazole skeleton or a distyrylcarbazole skeleton. Among these, metal-free phthalocyanine pigments, oxotitanyl phthalocyanine pigments, bisazo pigments containing a fluorene ring and / or a fluorenone ring, bisazo pigments composed of aromatic amines, trisazo pigments, etc. have high charge generation ability and high sensitivity. Suitable for obtaining a photosensitive layer. One type of charge generating material can be used alone, or two or more types can be used in combination. The content of the charge generation material is not particularly limited, but is preferably 5 to 500 parts by weight, more preferably 10 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer.

  As the binder resin for the charge generation layer, those commonly used in this field can be used. For example, melamine resin, epoxy resin, silicone resin, polyurethane, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, polycarbonate, phenoxy Examples thereof include resins, polyvinyl butyral, polyarylate, polyamide, and polyester. Binder resin can be used individually by 1 type, or can use 2 or more types together as needed.

  The charge generation layer comprises a charge generation material, a binder resin, and, if necessary, an appropriate amount of a plasticizer, a sensitizer, etc., dissolved or dispersed in an appropriate organic solvent capable of dissolving or dispersing these components. It can be formed by preparing a generation layer coating solution, applying the charge generation layer coating solution to the surface of the conductive substrate, and drying. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 0.05 to 5 μm, more preferably 0.1 to 2.5 μm.

  The charge transport layer laminated on the charge generation layer has as essential components a charge transport material having the ability to accept and transport the charge generated from the charge generation material and a binder resin for the charge transport layer. Known antioxidants, plasticizers, sensitizers, lubricants and the like. As the charge transport material, those commonly used in this field can be used, for example, poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensation product and derivatives thereof, Polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, pyrazoline Derivatives, phenylhydrazones, hydrazone derivatives, triphenylamine compounds, tetraphenyldiamine compounds, triphenylmethane compounds, stilbene compounds, 3-methyl-2-benzothiazoline -Donating substances such as azine compounds, fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, tetracyano Examples include electron-accepting substances such as ethylene, tetracyanoquinodimethane, promanyl, chloranil, and benzoquinone. The charge transport materials can be used alone or in combination of two or more. The content of the charge transport material is not particularly limited, but is preferably 10 to 300 parts by weight, more preferably 30 to 150 parts by weight with respect to 100 parts by weight of the binder resin in the charge transport material.

  As the binder resin for the charge transport layer, those commonly used in this field and capable of uniformly dispersing the charge transport material can be used. For example, polycarbonate, polyarylate, polyvinyl butyral, polyamide, polyester, polyketone, epoxy resin, Examples thereof include polyurethane, polyvinyl ketone, polystyrene, polyacrylamide, phenol resin, phenoxy resin, polysulfone resin, and copolymer resins thereof. Among these, in consideration of film formability, wear resistance of the resulting charge transport layer, electrical characteristics, etc., polycarbonate containing bisphenol Z as a monomer component (hereinafter referred to as “bisphenol Z type polycarbonate”), bisphenol Z type polycarbonate And a mixture of polycarbonate with other polycarbonates are preferred. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The charge transport layer preferably contains an antioxidant together with the charge transport material and the binder resin for the charge transport layer. As the antioxidant, those commonly used in this field can be used, and examples thereof include vitamin E, hydroquinone, hindered amine, hindered phenol, paraphenylenediamine, arylalkane and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds. It is done. One antioxidant can be used alone, or two or more antioxidants can be used in combination. The content of the antioxidant is not particularly limited, but is 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the total amount of components constituting the charge transport layer.

  The charge transport layer comprises a charge transport material, a binder resin, and, if necessary, an appropriate amount of an antioxidant, a plasticizer, a sensitizer, etc. dissolved in an appropriate organic solvent capable of dissolving or dispersing these components. It can be formed by dispersing to prepare a charge transport layer coating solution, applying the charge transport layer coating solution to the surface of the charge generation layer, and drying. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably 10 to 50 μm, more preferably 15 to 40 μm.

  Note that a photosensitive layer in which a charge generation material and a charge transport material are present can be formed in one layer. In that case, the type, content, binder resin, and other additives of the charge generation material and the charge transport material may be the same as in the case of separately forming the charge generation layer and the charge transport layer.

  In the present embodiment, as described above, the photosensitive member formed with the organic photosensitive layer using the charge generation material and the charge transport material is used, but instead, an inorganic photosensitive layer using silicon or the like is formed. A photoreceptor can also be used.

  FIG. 2 is a perspective view schematically showing the configuration of the charging device 24. FIG. 3 is a front view of the charging device 24 shown in FIG. The charging device 24 is provided so as to be relatively movable with respect to the plate-like needle electrode 50 having a plurality of sharp projections 58, a holding member 51 that holds the needle electrode 50, and the needle electrode 50. Two cleaning members 52a and 52b that clean the surface of the needle-like electrode 50 by rubbing the needle-like electrode 50 during movement, a support member 53 that supports the cleaning members 52a and 52b, the cleaning members 52a and 52b, and A moving member 54 for moving the supporting member 53, a needle-like electrode 50, a holding member 51, a shielding case 55 for housing the cleaning members 52a and 52b and the supporting member 53, and a plate for adjusting the charging potential on the surface of the photosensitive drum 23 And a grid 56. The charging device 24 is disposed in the electrophotographic process unit 21 along the longitudinal direction of the photosensitive drum 23 while facing the photosensitive drum 23.

  The needle-like electrode 50 is a thin plate-like member made of, for example, stainless steel, and has a flat plate portion 57 that extends long in one direction and a sharpened shape that is formed so as to protrude in the short direction from one end surface of the flat plate portion 57 in the short direction. A nickel PTFE composite plating layer is formed on the surface of the needle-like electrode substrate constituted by the protrusions 58. Exemplifying the dimensions of the needle-like electrode 50, the length L1 in the short direction of the flat plate portion 57 is preferably about 10 mm, the length L2 in the protruding direction of the projection 58 is preferably about 2 mm, and the tip of the projection 58 Is preferably about 40 μm, and the pitch TP on which the protrusions 58 are formed is preferably about 2 mm.

  The needle electrode 50 can be manufactured according to a known method. As an example, a manufacturing method including a chemical polishing step, a water washing step, an acid dipping step, a water washing step, a pure water dipping step, a nickel plating step, a nickel PTFE composite plating step, a water washing treatment and a drying treatment can be mentioned. Among these steps, the nickel plating step is not an essential step and is performed as necessary.

  In the chemical polishing step, masking and etching are performed so that a plurality of sharp protrusions are formed on the sheet metal. Masking can be performed according to a known method. Etching can also be performed according to a known method, for example, a method of spraying an etching solution such as a ferric chloride aqueous solution onto a sheet metal. Here, the metal used as the material of the sheet metal can be used without particular limitation as long as corona discharge is possible by application of voltage, and sharp projections can be formed and can be plated. Examples include stainless steel, aluminum, nickel, copper, and iron. Among these, stainless steel is preferable. Specific examples of the stainless steel include SUS304, SUS309, SUS316, and the like. Among these, SUS304 is preferable. The thickness of the sheet metal is not particularly limited, but is preferably 0.05 to 1 mm, more preferably 0.05 to 0.3 mm.

  Sheet metal on which a plurality of sharp protrusions are formed in the chemical polishing process is subjected to water washing, acid washing or pure water washing in the water washing process, the acid dipping process, the water washing process and the pure water dipping process, and foreign matter is removed from the surface. It is removed and a needle-like electrode substrate is obtained.

  Although nickel plating can be performed by a generally practiced method, it is preferable to perform electroplating in consideration of forming a nickel PTFE composite plating layer later. The thickness of the nickel plating layer is not particularly limited, but is preferably 0.03 to 3 μm, more preferably 0.5 to 1.5 μm, and particularly preferably about 1 μm.

  The nickel PTFE composite plating step can be performed, for example, according to an electroless nickel plating method such as a catalytic nickel plating method (Kanizen method). Here, as the plating bath, for example, a plating bath in which polytetrafluoroethylene is further added to an aqueous solution containing hypophosphorous acid or a salt thereof and a nickel salt is used. The pH of the plating bath is usually adjusted to a range of 5 to 5.5. The polytetrafluoroethylene used here is particulate polytetrafluoroethylene, and the particle diameter is not particularly limited as long as it is smaller than the thickness of the plating layer to be formed, but is preferably 1 μm or less, more preferably Is 100-500 nm. Although the amount of polytetrafluoroethylene added to the plating bath is not particularly limited, it is preferably 0.01 to 10% by weight, more preferably 0.1 to 1.0% by weight based on the total weight of the plating bath. Specific examples of the plating solution include, for example, the product name “Kaniflon S” manufactured by Nippon Kanisen Co., Ltd., the product name “Nimflon” manufactured by Uemura Kogyo Co., Ltd., and the product name “Topni” manufactured by Okuno Pharmaceutical Co., Ltd. "Cogit" series. A nickel PTFE composite plating layer is formed on the surface of the substrate by immersing the needle electrode substrate in a plating bath having the composition and pH as described above at a bath temperature of 90 ° C. or more and performing electroless plating. . The content of PTFE in the nickel PTFE composite plating layer to be formed is preferably 3 to 30% by volume, more preferably 20 to 30% by volume. The layer thickness of the nickel PTFE composite plating layer to be formed is not particularly limited, but is preferably 0.3 μm or more, more preferably 0.3 to 20 μm, and particularly preferably 1 to 5 μm. If the thickness is less than 0.3 μm, pinholes are likely to be generated and become non-uniform, and the stainless steel of the needle electrode substrate is corroded through the pinholes, so that the charged potential obtained on the photoreceptor is partially It tends to be unstable. On the other hand, if it greatly exceeds 20 μm, the plating film may be peeled off due to stress. In addition, since the thickness of the nickel PTFE composite plating layer is almost proportional to the length of the plating time, the immersion time of the needle electrode substrate in the plating bath is appropriately changed in order to obtain a plating layer having a desired thickness. Just do it.

  Since the nickel PTFE composite plating layer formed by electroless plating is uniformly applied to the surface of the needle-shaped electrode substrate, the plating bath solution can be used even when the thickness of the plating layer is as thin as about 0.3 μm. It has preferable characteristics that it is uniform without thickness variation and has very few pinholes. Furthermore, the plating structure is dense and has high adhesion to the surface of the needle-shaped electrode substrate, so that peeling does not occur even when used for a long period of time.

  The nickel PTFE composite plating step can be performed by electroplating. As the plating bath, the same one as the electroless plating bath can be used. The electroplating conditions are the same as general nickel electroplating. In nickel PTFE composite plating by electroplating, there is a tendency peculiar to electroplating, that is, there is a tendency that the edge portion can easily be plated. Therefore, it is necessary to increase the layer thickness in order to make the layer thickness uniform, Needs to have a layer thickness of 3 μm or more.

  Note that, when forming the nickel PTFE composite plating layer, whether to select electroless plating or electroplating may be determined according to the characteristics and cost of each plating method.

  The holding member 51 that holds the needle-like electrode 50 is a member that extends long in one direction like the needle-like electrode 50 and has an inverted T-shaped cross section perpendicular to the longitudinal direction, and is made of, for example, resin. The needle electrode 50 is screwed by a screw member 59 to one side surface of the protruding portion of the holding member 51 in the vicinity of both ends in the longitudinal direction. A voltage of about 5 kV is applied to the needle-like electrode 50 for corona discharge during operation to charge the photosensitive member 23 described above.

  The cleaning members 52a and 52b have a plate shape, more specifically, a planar projection shape having a T shape, and are made of an elastic body of a metal material or a polymer material having a thickness t of 20 to 40 μm. If the thickness t is less than 20 μm, it easily deforms when it comes into contact with the needle-like electrode 50, but the pressing force against the needle-like electrode 50, which is a reaction force accompanying the deformation, becomes weak, so The substance cannot be removed sufficiently. If the thickness t exceeds 40 μm, the contaminants adhering to the needle electrode 50 can be sufficiently removed, but the rigidity becomes so high that the pressing force against the needle electrode 50 becomes too strong. There is a risk of the 58 tip being deformed and damaged. As a result, when the thickness t is out of the range of 20 to 40 μm, there is a possibility that image unevenness or the like due to charging failure occurs. As a metal material constituting the cleaning members 52a and 52b, phosphor bronze, ordinary steel, stainless steel, or the like can be used. Among these, considering that the cleaning members 52a and 52b are used in an ozone atmosphere generated by corona discharge, stainless steel is preferable from the viewpoint of durability life based on oxidation resistance. Examples of stainless steel include SUS304, which is an austenitic stainless steel defined in Japanese Industrial Standards (JIS) G4305, and SUS430, which is a ferritic stainless steel, but are not limited thereto. Stainless steel may be used.

  The hardness of the cleaning members 52a and 52b is desirably 115 or more on the Rockwell hardness M scale defined in the American Society for Testing and Materials (ASTM) standard D785. If the Rockwell hardness is less than 115, the hardness is too soft, so that when cleaning the contact with the needle electrode 50, the cleaning members 52a and 52b are deformed more than necessary, and the cleaning effect cannot be obtained. Even if the hardness of the cleaning members 52a and 52b is high, there is no particular problem in terms of function, so there is no need to set an upper limit. However, since the upper limit value of the Rockwell hardness M scale is 130, if an upper limit is set. That is 130.

  The width dimension w of the T-shaped vertical bar portion that is the portion of the cleaning members 52a and 52b that is in contact with the needle-like electrode 50, that is, in the direction perpendicular to the moving direction of the cleaning members 52a and 52b and in the direction in which the protrusion 58 extends On the other hand, the dimension w of the cleaning members 52a and 52b in the vertical direction is preferably 3.5 mm or more. When the width dimension w is less than 3.5 mm, the value per unit area of the force generated when the needle-like electrode 50 is pressed and deformed increases, so that fatigue failure due to repeated deformation is likely to occur, and the durability life is reduced. . By setting the width dimension w to 3.5 mm or more, the value per unit area of the force described above can be reduced and the durability life against repeated deformation can be increased. However, if the width is excessively wide, the rigidity becomes too strong, Since the size is increased, the upper limit is preferably set to about 10 mm.

  The cleaning members 52a and 52b and the needle-like electrode 50 are arranged so that the biting amount d of the protrusion 58 of the needle-like electrode 50 with respect to the cleaning members 52a and 52b is 0.2 to 0.8 mm. Is preferred. Here, the biting amount d is a state in which the cleaning members 52a and 52b and the protrusion 58 are projected on a virtual plane perpendicular to the direction in which the cleaning members 52a and 52b move relative to the needle electrode 50. The cleaning members 52a and 52b and the protruding portion 58 mean a length that overlaps in the extending direction of the protruding portion 58. When the biting amount d is less than 0.2 mm, the pressing force against the needle electrode 50 which is a reaction force accompanying the deformation of the cleaning members 52a and 52b becomes weak, so that the contaminants adhering to the needle electrode 50 cannot be removed sufficiently. If the amount of bite d exceeds 0.8 mm, the contaminants adhering to the needle electrode 50 can be sufficiently removed, but the reaction force (the pressing force against the needle electrode 50) accompanying the deformation of the cleaning members 52a and 52b becomes strong. Therefore, the tip of the protrusion 58 of the needle electrode 50 may be deformed and damaged. As a result, if the biting amount d is out of the range of 0.2 to 0.8 mm, there is a possibility that image unevenness or the like due to defective charging occurs.

  The support member 53 is a member having an inverted L shape that supports the cleaning members 52a and 52b, and arm portions of the cleaning members 52a and 52b having a T shape are attached to the beam-like portions. The two cleaning members 52a and 52b are provided to have a predetermined interval L3 with respect to the direction of movement relative to the needle electrode 50. The interval L3 is selected so that when one of the cleaning members 52a deforms by contacting the needle electrode 50, the other cleaning member 52b does not hit the deformed cleaning member 52a, and is attached to the support member 53 to be mounted. It can be adjusted by the thickness of the beam. Since the deformation state varies depending on the material constituting the cleaning members 52a and 52b, it is desirable to determine the distance L3 by testing the deformation state of the material in advance. For example, when the cleaning members 52a and 52b are made of stainless steel having a thickness t of 30 μm, the distance L3 is preferably 2 mm. By providing the interval L3 between the two cleaning members 52a and 52b, while the one cleaning member 52a scrapes the needle-like electrode 50, the other cleaning member 52b does not hinder the deformation of the cleaning member 52a. Since the pressure can be maintained, the tip of the needle electrode 50 can be sufficiently cleaned without being deformed and damaged.

  The shield case 55 is made of, for example, stainless steel, and is a container-like member having a rectangular parallelepiped outer shape and having an internal space, and having an opening on one surface facing the above-described photoreceptor 23. The shield case 55 extends long in the same direction as the needle-like electrode 50 and has a substantially U-shaped cross section in a direction orthogonal to the longitudinal direction. The holding member 51 is attached to the bottom surface 63 of the shield case 55. Further, the end portion of the columnar portion of the support member 53 is slidably inserted into the groove portion 62 formed by the inner surface 61 of the shield case 55 and the holding member 51.

  A through hole 60 is formed in the columnar portion of the support member 53 in parallel with the extending direction of the needle electrode 50, and a moving member 54 is provided through the through hole 60. Since the moving member 54 is fixed to the support member 53 at a portion inserted through the through hole 60, the support member 53 is pulled into the groove 62 by pulling the moving member 54 in the extending direction of the needle electrode 50. The needle electrode 50 can slide in the direction in which the needle electrode 50 extends by being guided by the groove 62. That is, the cleaning members 52 a and 52 b supported by the support member 53 can be abutted against the needle-like electrode 50 and rubbed.

  The moving member 54 is a thread-like or wire-like member, extends outward from the shield case 55 through a hole or gap formed in the shield case 55, and is a pulley 64a provided on the outer surface of the shield case 55 or on the body of the copying machine 2. , 64b, and its end is suspended. Note that the ends of the pulleys 64a and 64b and the moving member 54 are omitted in FIG. The end of the moving member 54 is preferably extended to the outside of the image forming apparatus 1. Accordingly, the needle electrode 50 can be cleaned without removing the charging device 24 from the image forming apparatus 1 or without opening the image forming apparatus 1.

  When the cleaning member 52a, 52b is brought into contact with the needle electrode 50 by the pulling of the moving member 54 for cleaning, the pressing force of the cleaning member 52a, 52b against the needle electrode 50 is adjusted to be 10 to 30 gf. Is preferred. If the pressing force is less than 10 gf, there is a possibility that contaminants such as toner and paper powder adhering to the needle electrode 50 may not be sufficiently removed. If the pressing force exceeds 30 gf, the tip of the protrusion 58 of the needle electrode 50 is deformed and damaged. There is a fear.

  The pressing force of the cleaning members 52a and 52b against the needle electrode 50 can be adjusted as follows, for example. With the weight suspended from one end of the moving member 54, the magnitude of the force applied to the cleaning member 52a or 52b is measured. The measurement is performed, for example, by connecting a spring balance to the cleaning member 52a or 52b. Then, by selecting a weight with which the force applied to the cleaning member 52a or 52b is 10 to 30 gf and cleaning the needle electrode 50, the weight selected in advance is suspended from the end of the moving member 54. It can be cleaned with a predetermined pressing force. Further, an electric motor whose rotational torque is adjusted may be connected to the end of the moving member 54 so that a predetermined pressing force can be applied.

  The plate-like grid 56 is provided between the needle-like electrode 50 and the photosensitive drum 23, and a voltage is applied to the plate-like grid 56 to adjust the variation in the charged state on the surface of the photosensitive drum 23 and to set the charging potential. Make uniform. The plate-like grid 56 is configured to include a metal material like the needle-like electrode 50. The plate-like grid 56 can be produced in the same manner as the needle-like electrode 50 except that masking and etching are performed so as to be formed in a porous shape in the chemical polishing step. Furthermore, the plate-like grid 56 can be subjected to nickel plating, nickel PTFE composite plating, or the like similar to the needle-like electrode 50.

  According to the charging device 24, corona discharge occurs when a voltage is applied to the needle-like electrode 50, the surface of the photosensitive member unevenness 23 is charged, and a predetermined grid voltage is applied to the plate-like grid 56. Thus, the charged state of the surface of the photosensitive drum 23 is made uniform, so that the surface of the photosensitive drum 23 can be charged to a predetermined potential and polarity. Further, by pulling the moving member 54, the cleaning members 52a and 52b that come into contact with the support member 53 and thus the needle electrode 50 are moved, and contaminants such as toner adhering to the needle electrode 50 are efficiently and reliably removed. The

  Here, referring back to FIG. 1, the optical scanning unit 25 is composed of a semiconductor laser or the like, and a laser light source 25 a that emits laser light that is modulated according to image document information input from the document reading unit 5 or an external device; A polygon mirror 25b that deflects laser light emitted from the laser light source 25a in the main scanning direction, and a lens that converges the laser light deflected in the main scanning direction by the polygon mirror 25b so as to form an image on the surface of the photosensitive drum 23. 25c and mirrors 25d and 25e that reflect the laser beam converged by the lens 25c. Laser light emitted from the laser light source 25a is deflected by the polygon mirror 25b, converged by the lens 25c, reflected by the mirrors 25d and 25e, and irradiated onto the surface of the photosensitive drum 23 charged to a predetermined potential and polarity. Then, an electrostatic latent image corresponding to the image document information is formed.

  The developing unit 26 is provided so as to face and press-contact the photosensitive drum 23, and supplies a developing roller 26a for supplying a developer containing toner to the electrostatic latent image formed on the surface of the photosensitive drum 23, and the developing roller 26a. A supply roller 26b for supplying a developer containing toner to the developing roller 26a, a casing for rotatably supporting the developing roller 26a and the supply roller 26b, and accommodating the developer in the internal space thereof 26c. The developer accommodated in the casing 26c adheres to the surface of the developing roller 26a by the rotation of the supply roller 26b, and is further supplied from the surface of the developing roller 26a to the electrostatic latent image on the surface of the photosensitive drum 23. The latent image is developed to obtain a toner image.

  The developer storage unit 27 is a developer storage container provided adjacent to the development unit 26, and supplies an appropriate amount of developer to the development unit 26 according to the remaining amount of developer in the development unit 26.

  The transfer unit 28 includes a driving roller 28a provided so as to be rotatable around an axis by driving means (not shown), driven rollers 28b and 28c, and an endless belt 28d stretched around the driving roller 28a and the driven rollers 28b and 28c. Consists of including. The driving roller 28a is provided not only so as to be rotationally driven, but also so as to face the photosensitive drum 23 via the endless belt 28d and to press the photosensitive drum 23, the endless belt 28d, and the driving roller 28a in this order. It is done. According to the transfer unit 28, the recording medium is supplied from the paper feeding unit 2 through the third conveyance path 32 and supplied between the photosensitive drum 23 and the endless belt 28 d, and the recording medium is exposed to light by pressing by the driving roller 28 a. The surface of the body drum 23 is brought into pressure contact, and the toner image on the surface is transferred to a recording medium. After the toner image is transferred in this way, the recording medium is fed to the fixing unit 22.

  After the transfer unit 28 transfers the toner image to the recording medium, the cleaning unit 29 removes the toner remaining on the surface of the photosensitive drum 23 and cleans the surface of the photosensitive drum 23. For example, a cleaning blade is used for the cleaning unit 29. In the image forming apparatus of the present invention, an organic photosensitive drum is mainly used as the photosensitive drum 23, and the surface of the organic photosensitive member is mainly composed of a resin component. Surface degradation is likely to proceed due to the chemical action of the ozone generated. However, the deteriorated surface portion is worn by receiving a rubbing action by the cleaning unit 29 and is gradually but surely removed. Therefore, the problem of surface deterioration due to ozone or the like is practically solved, and the charging potential by the charging operation can be stably maintained over a long period of time.

  According to the electrophotographic process unit 21, as the photosensitive drum 23 is driven to rotate, an electrostatic latent image is formed by charging and exposure, a toner image is formed by developing the electrostatic latent image, and the toner image is transferred to a recording medium. , And a series of operations of cleaning the surface of the photosensitive drum 23, the toner image is transferred to the recording medium, and the recording medium is fed to the fixing unit 22.

  The fixing unit 22 is provided so as to be rotatable around an axis, and has a fixing roller 30 having a heating unit (not shown) therein, and a pressure roller provided in pressure contact with the surface of the fixing roller 30 so as to be rotatable around the axis. 31 and a temperature sensor 32 provided so as to face the surface of the fixing roller 30 and detecting the surface temperature of the fixing roller 30. For example, a heater or the like can be used as a heating unit (not shown) provided inside the fixing roller 30. Further, the amount of electric power supplied to the heater is controlled by a control unit (not shown) so that the surface temperature of the fixing roller 30 is maintained at a predetermined temperature according to the detection result by the temperature sensor 32. According to the fixing unit 22, the recording medium onto which the toner image is transferred, obtained in the electrophotographic process unit 21, is supplied to the pressure contact portion between the fixing roller 30 and the pressure roller 31, and the fixing roller 30 and the pressure roller 31. The toner image is fixed to the recording medium by being pressurized and heated when passing through the pressure contact portion in accordance with the rotational driving of the toner, and an image-recorded recording medium is obtained.

  According to the image forming unit 3, the toner image corresponding to the image original information is transferred to the recording medium fed from the paper feeding unit unit 2, and is further heated and pressed to fix the toner image to the recording medium. Thus, a recording medium on which a high-quality image is formed can be obtained for a long time and continuously.

  The paper discharge unit 4 changes the transport direction of the image-recorded recording medium, and a fourth transport path 34 for supplying the image-recorded recording medium obtained in the fixing unit 22 of the image forming unit 3 to reversing rollers 36a and 36b described later. The reversing rollers 36a and 36b, the fifth transport path 35 for transporting the image-recorded recording medium to a discharge tray or a sixth transport path 37 (not shown) provided outside the image forming apparatus 1, and the image-recorded recording medium. And a sixth transport path 37 transported to the third transport path 33 again. Here, the reversing rollers 36a and 36b are both provided so as to be capable of rotating in the forward and reverse directions around the axis and so as to be in pressure contact with each other. The image-recorded recording medium supplied to the pressure contact portions of the reverse rollers 36a and 36b via the fourth conveying path 34 is sandwiched between the reverse rollers 36a and 36b by the forward rotation of the reverse rollers 36a and 36b. Is done. Thereafter, the reverse rollers 36a and 36b are conveyed in the fifth conveyance path 35 by rotation in the reverse direction. When an image is recorded only on one side of the recording medium, the sheet is discharged outside the image forming apparatus 1 in the direction of the arrow 101 by the operation of a switching gate (not shown) via the fifth transport path 35. It is discharged to the tray. Further, when images are formed on both sides of the recording medium, the image is transferred from the fifth transfer path 35 to the sixth transfer path 37 by the operation of a switching gate (not shown), and is turned upside down and then passes through the third transfer path. Then, the toner image is conveyed to the image forming unit 3 where the toner image is transferred and fixed.

The document reading unit 5 includes a document supply unit 38 and an image reading unit 39.
The document supply unit 38 includes a document tray 40 on which documents are placed, a document restriction plate 41 that feeds documents, a curved conveyance path 42 that conveys the image surface of the document to be reversed, a material supply unit 38, and a later-described document supply unit 38. And a protective mat 43 provided on the contact surface with the original platen (platen glass) 44. The document tray 40 is placed so that the image surface of the document faces upward. The document regulating plate 41 feeds documents one by one to the curved conveyance path 42. The curved conveyance path 42 conveys the document to the position just above the document table 44 while being reversed so that the image surface of the document is directed downward. The document restricting plate 41 mainly protects the document table 44 formed of platen glass. According to the document supply unit 38, after inputting printing conditions such as the number of prints, the printing magnification, and the paper size with the condition input key on an operation panel (not shown) arranged on the front surface of the exterior of the image forming apparatus 1, the start key is pressed. When pressed, the copy operation is started, and the originals placed on the original tray 40 with the image surface facing upward are automatically conveyed one by one, and inversion processing is performed so that the image surface faces downward during the conveyance. Then, it is conveyed to just above the document table 45. While the document passes over the document table 45, the image document information of the document is read by an image reading unit 39 described later. The document passing over the document table 45 is then discharged by a discharge roller 49 to a discharge tray (not shown) provided outside the image forming apparatus 1.

  The image reading unit 39 places a document that cannot be automatically conveyed and is provided apart from the document table 44 for reading the image document information and the document table 44 in the sub-scanning direction. A document table 45 for passing a document that can be automatically conveyed and reading image document information when the document passes, and a light source provided to be movable in a direction parallel to the surfaces of the document tables 44 and 45 (sub-scanning direction) The unit 46 includes a mirror unit 47 that guides reflected light from the document to a later-described CCD reading unit 48, and a CCD reading unit 48 that converts reflected light from the document into an electrical signal.

  The light source unit 46 includes only a light source 46a, a concave reflector (not shown) for condensing the reading illumination light emitted from the light source 46a at a predetermined reading position on the document table 44 or the document table 45, and only reflected light from the document. Includes a slit (not shown) that selectively passes through and a mirror 46b that reflects the reflected light from the original by 90 °. The light source unit 46 emits reading illumination light to the document and supplies light reflected from the document to the mirror unit 47.

  The mirror unit 47 includes a pair of mirrors 47a and 47b arranged so that the reflecting surfaces are orthogonal to each other. The reflected light from the original supplied from the light source unit 46 is guided to the CCD reading unit 48 by changing its optical path by 180 ° by the mirrors 47 a and 47 b.

  The CCD reading unit 48 includes an imaging lens 48a that forms an image of the reflected light from the mirror unit 47, and a CCD image sensor 48b that outputs an electrical signal corresponding to the light imaged by the imaging lens 48a. The reflected light incident on the imaging lens 48a from the mirror unit 47 is imaged, and the image is converted into an electrical signal by the CCD image sensor 48b. The image original information as an electrical signal is optically scanned via a control unit (not shown). The image is input to the unit 25 and image formation corresponding to the input is executed.

  According to the image reading unit 39, image document information of the document placed on the document tables 44 and 45 is taken in as reflected light from the document by light irradiation from the light source unit 46, and this reflected light is further reflected in the mirror unit 47. Then, it is led to the CCD reading unit 48 and converted into image original information of an electric signal. This information is subjected to image processing under preset conditions, transmitted to the optical scanning unit 25 of the image forming unit 3, and image formation is performed.

The present invention will be specifically described with reference to examples.
(Example 1)
Masking treatment and etching treatment were performed on a sheet metal (size 20 mm × 310 mm × thickness 0.1 mm) made of stainless steel (SUS304) to produce a needle-shaped electrode substrate. Etching was performed by spraying a 30 wt% aqueous ferric chloride solution at a liquid temperature of 90 ° C. for 2 hours onto a stainless steel sheet metal. After the etching, the needle electrode base material was taken out from the etching solution, washed with water and washed with pure, to produce a needle electrode base material.

  A Ni plating layer having a thickness of 0.5 μm was formed by electroplating on the surface of the needle-like electrode substrate obtained above. Next, the needle-like electrode base material on which this Ni plating layer was formed was immersed in a nickel PTFE composite plating bath (trade name: Nimflon, manufactured by Uemura Kogyo Co., Ltd., liquid temperature 90 ° C.) for 25 minutes, and the thickness was increased on the surface. A needle electrode having a 3 μm nickel PTFE composite plating layer formed thereon was produced. After the completion of plating, the needle electrode was taken out of the plating bath, washed with water and washed with pure, and dried.

  This acicular electrode was replaced with the acicular electrode of the charging device in a commercially available image forming apparatus (trade name: AR625, manufactured by Sharp Corporation) to produce the charging device and the image forming apparatus of the present invention. The following tests were carried out using this needle electrode, charging device and image forming apparatus.

[Discharge test]
As a severe test, an aging test without passing paper was performed under low humidity conditions (10% or less). Since AR625 is a 70-sheet machine, 71 hours corresponds to the number of copies (300K life). In this test, the charged potential on the surface of the photoreceptor was initially set to -630V.

[Detection of nitrogen oxides and rust]
Detection of rust and nitrogen oxides was performed by observing the needle electrode after discharge with a microscope.
As a result, precipitation of rust or the like was observed on the needle-like electrode as it was made of stainless steel, whereas precipitation of rust or the like was not observed on the needle-like electrode plated with the present plan.

  In addition, even after printing 300,000 sheets in an actual copying test, when the needle-like electrode made of stainless steel is not cleaned, white stripes and black stripes are seen in the halftone image. The needle-like electrode had a uniform halftone image quality and no unevenness.

  In addition, due to the smoothness of the surface, which is a feature of nickel PTFE composite plating, there are fewer deposits such as dust in the air compared to stainless steel needle electrodes, and it can be easily removed during cleaning. There was found. On the other hand, since the stain cannot be sufficiently removed by cleaning only with the Ni plating layer, the image quality of the halftone does not recover uniformly after cleaning.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to a first embodiment of the present invention. It is a perspective view which shows schematically the structure of the charging device which is other embodiment of this invention. FIG. 3 is a front view of the charging device shown in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1a Side surface of image forming apparatus 2 Paper feed unit part 3 Image forming part 4 Paper discharge part 5 Document reading part 10, 11, 12, 13 Paper feed tray 14 1st conveyance path 15 2nd conveyance path 16 Frame 17 Manual feed section 18 Manual feed tray 19a, 19b Paper feed rollers 19a, 19b
DESCRIPTION OF SYMBOLS 20 Manual feed path 21 Electrophotographic process part 22 Fixing part 23 Photoconductor drum 24 Charging device 25 Optical scanning unit 25a Laser light source 25b Polygon mirror 25c Lens 25d, 25e Mirror 26 Developing unit 26a Developing roller 26b Supply roller 26c Casing 27 Developer Storage unit 28 Transfer unit 28a Drive roller 28b, 28c Driven roller 28d Endless belt 29 Cleaning unit 30 Fixing roller 31 Pressure roller 32 Temperature sensor 33 Third transport path 34 Fourth transport path 35 Fifth transport path 36a, 36b Reverse roller 37 Sixth transport path 38 Document supply section 39 Image reading section 40 Document tray 41 Document restriction plate 42 Curved transport path 43 Protective mats 44, 45 Document table 46 Light source unit 46a Light source 46b Mirror 47 Unit 47a, 47b mirror 48 CCD reading unit 48a imaging lens 48b CCD image sensor 49 discharge roller 50 needle electrode 51 holding member 52a, 52b cleaning member 53 support member 54 moving member 55 shield case 56 plate grid 57 flat plate portion 58 Sharp protrusion 59 Screw member 60 Through hole 61 Inner side surface of shield case 62 Groove portion 63 Bottom surface of shield case 64a, 64b Pulley 100 Installation surface of image forming apparatus 101 Arrow

Claims (6)

An electrode that has a plurality of sharp protrusions and applies a voltage to the surface of the photoconductor to charge the surface, and a plate-like grid that is provided between the electrode and the photoconductor to control the charging potential of the photoconductor surface In a charging device including
A charging device comprising a nickel plating layer containing polytetrafluoroethylene formed on at least one surface of an electrode.   The charging device according to claim 1, wherein the nickel plating layer containing polytetrafluoroethylene is formed by an electroless plating method.   3. The charging device according to claim 1, wherein the nickel plating layer containing polytetrafluoroethylene has a thickness of 0.3 [mu] m or more.   The charging device according to claim 1, wherein a nickel plating layer is further formed between the electrode and the nickel plating layer containing polytetrafluoroethylene.   The charging device according to claim 1, wherein the nickel plating layer containing polytetrafluoroethylene contains phosphorus as a plating component together with nickel. A photosensitive member on which an electrostatic charge image is formed, a charging device for charging the surface of the photosensitive member, and an exposure for forming an electrostatic charge image by irradiating the charged photosensitive member surface with signal light based on image information Means, developing means for developing an electrostatic image formed on the surface of the photosensitive member to form a toner image, transfer means for transferring the toner image to a recording material, and fixing the toner image transferred to the recording material In an image forming apparatus including a fixing unit,
An image forming apparatus, wherein the charging device is any one of the charging devices according to claim 1.

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