JPH077223B2 - Discharge device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge device in which the amount of ozone generated is further reduced.

(Prior Art) Conventionally, many corona chargers have been used in electrophotographic copying machines and printers. For example, in the charging step, an image forming member such as a photosensitive drum is charged to a uniform potential by using a corona charger. Also in the transfer process, the corona charger for static elimination is used to transfer the toner image formed on the photosensitive drum to the recording paper side using the corona charger and to separate the recording paper from the photosensitive drum. Has been.

The corona charger used in these charging process and transfer process applies a high voltage of, for example, about 6 KV to the corona wire mounted in the shield case, and ionizes the space around the corona wire by this high voltage, The surface of an object to be charged such as a photosensitive drum is uniformly charged by the discharge charge generated by the ionizing action. However, since this corona charger uses a relatively thick corona wire with a wire diameter of about 60 μm and requires a large distance between the corona wire and the shield case, a high corona voltage such as 6 KV can be applied. This has to be applied, resulting in the disadvantage that an extremely large amount of ozone gas is generated. Since this ozone gas is harmful to the human body, there is an urgent need to develop a charging device that produces a small amount of ozone.

A brush charging method has been proposed as a charging device capable of charging with a small amount of ozone generation. With this brush charging method, the wire diameter is
Using a brush roller in which a large number of conductive fibers of about 10 μm are planted, the tip of the conductive fiber is brought into sliding contact with the surface of the photoconductor, and the corona discharge generated at the tip of the conductive fiber is used for the photoconductor. The surface is charged. In this brush charging method, the diameter of the conductive fiber that generates corona discharge is 10 μm.
Since the diameter and the diameter can be made small, the discharge starting voltage becomes low, and therefore the advantage that the ozone generation amount can be further reduced is achieved.

(Problems to be Solved by the Invention) In the brush charging device described above, charging is performed while the conductive fibers having a small diameter are brought into sliding contact with the surface of the photoconductor, so that mechanical stress is exerted strongly on the brush, and the brush is used for a long period of time. If it is used for a long time, the conductive fibers may fall over or fall out, and a uniform contact state may not be obtained. As a result, the surface of the photosensitive drum cannot be uniformly charged over the entire surface, and there is a problem in durability in practical use. Further, in order to be charged to a uniform surface potential, it is necessary to strictly regulate the contact state between the tip of the brush and the surface of the photoconductor, that is, the distance between the tip of the fiber and the surface of the photosensitive drum. For example, when the contact amount is too large, the tip of the conductive fiber is largely bent, and the tip of the fiber is separated from the surface of the photosensitive drum by a large distance, and the charging potential is lowered. On the other hand, if the contact amount is too small, uniform corona discharge does not occur and the charging potential becomes uneven. Therefore, there has been a problem that the setting work of the brush roller on the surface of the photosensitive member is troublesome. further,
If it is used for a long period of time, the residual toner that has not been removed in the transfer process adheres to the brush surface. Discharge did not occur locally, and there was the inconvenience that uniform charging was not possible.

Therefore, the object of the present invention is to eliminate the above-mentioned drawbacks, to charge the photoconductor to a desired surface potential with an extremely small amount of ozone generation, and to set the surface of the object to be charged to a predetermined level by a simple setting operation with excellent durability. The present invention provides a discharge device that can be uniformly charged to a potential.

(Means for Solving Problems) A discharge device according to the present invention includes an electrode member, a discharge body having a porous insulating coating formed on at least a part of an outer peripheral surface of the electrode member, and the discharge body. A supporting member for supporting the electrode member in an insulating state, and a power supply device for applying a discharge voltage to the electrode member, and a charged object is discharged from the surface of the electrode member through the holes of the porous insulating film to discharge the charged object. It is characterized by being charged to a predetermined potential.

(Operation) In the charging method using air discharge, the most effective method is to lower the discharge start voltage in order to reduce the amount of ozone generated. It is known that in a corona ion generator using a non-uniform electric field method using a linear discharge body, the critical voltage Vo at which corona discharge starts is expressed by the following empirical formula.

Where m = 1 t = temperature (° C) r = radius of discharge fine wire (cm) R = radius of cylindrical shield case (cm) (1) is an empirical formula for a linear body with a circular cross section. It is considered that the same can be applied to the case of a projection having a large curvature.

As a result of various analyzes of the formula (1), the present inventor has found that it is effective to satisfy any one of the following requirements in order to further lower the discharge starting voltage.

(A) To further increase the curvature of the discharge body.

(B) To further reduce the distance from the discharge body to the counter electrode.

FIG. 1 is a schematic diagram for explaining the principle of the present invention.
A conductive rubber layer 3 impregnated with, for example, carbon particles 2 is formed on the outer peripheral surface of the metal base electrode member 1.
It is considered that when a large amount of carbon particles 2 are impregnated in the rubber material, the carbon particles form a chain and form a large number of conductive paths 4. One end of the conductive path 4 of the chain-like carbon particles comes into contact with the surface of the base electrode member 1, and the other end is exposed on the surface of the conductive rubber layer 3. Therefore, on the surface of the rubber layer 3, minute protrusions composed of the carbon particles 2 are formed. Since it is considered that the particle size of the carbon particles 2 is about 1 μm or less, 1 μm is present on the surface of the conductive rubber layer 3.
A large number of minute protrusions having the following diameters will be formed. On this conductive rubber layer 3, a porous insulating coating 5 having a thickness of 100 μm, for example, is formed to form a discharge body 6. This discharge body 6
Are brought into contact with the surface of the object 7 to be charged. In the present example, the object to be charged 7 is a photoreceptor having a photosensitive layer formed on an Al base drum 8, and the base drum 8 is grounded. When a discharge voltage is applied to the base electrode 1 from the DC high-voltage power supply 9 with the insulating coating 5 of the discharge body in contact with the surface of the photosensitive layer, exposed carbon particles located in the holes of the insulating coating 5 are removed. Air discharge occurs in the air layer near the carbon particles, which constitutes the discharge tip of the discharge electrode, and the generated discharge charge is discharged toward the photoconductor 7. In this case, the distance from the carbon particles exposed on the surface that becomes the discharge electrode to the surface of the photosensitive layer is accurately defined by the film thickness of the insulating coating, so the distance from the discharge electrode to the surface of the charged object is extremely small. Can be As a result, the curvature of the tip of the discharge body for generating the discharge can be made extremely large and the distance to the counter electrode can be made extremely short, so that the discharge starting voltage can be further lowered. Further, since the distance between the discharge electrode and the surface of the object to be charged is extremely small, the surface of the object to be charged can be charged to a potential almost equal to the voltage applied to the discharge electrode. Further, the distance between the discharge electrode and the object to be charged is always accurately regulated to a constant value by the thickness of the insulating coating, so that the work of setting the discharge body is further facilitated.

Furthermore, if the discharge body is connected to a high-voltage AC power supply, positive and negative discharge charges are alternately emitted, and therefore, it can be used also as a static eliminator.

(Embodiment) FIG. 2 is a diagram showing the construction of an example of an electrophotographic printer device having a discharge device according to the present invention. The photosensitive drum 10 to be charged is rotated in the direction of arrow a. The photosensitive drum 10 has a structure in which a selenium layer or an organic photosensitive material layer is coated on the outer peripheral surface of an aluminum cylindrical base member, and the base member is grounded. The photosensitive drum 10 is completely discharged by the eraser lamp 11 and then discharged by the discharge device 12 of the present invention.
Is charged to a uniform surface potential, for example 600V. The discharge device 12 has a charging roller 13 in which a porous insulating coating is formed on the outer peripheral surface of a conductive roller member, and this charging roller is connected to a DC high voltage power supply 15 via a switch 14.
Then, the charging roller 13 is driven to rotate while being lightly pressed against the surface of the photosensitive member 10. When the charging roller 13 comes into contact with the photosensitive drum 10, air discharge is generated through the holes of the insulating film of the charging roller, and the photosensitive drum is charged to a uniform surface potential. After charging, it is exposed by an exposure device 16 such as an LED array to form an electrostatic latent image. This electrostatic latent image is developed by the developing device.
Develop with 17 to form a toner image. This toner image is transferred by the transfer device 18 onto the recording paper 20 that is synchronously conveyed from the paper feed cassette 19. Recording paper with toner image transferred
20 is conveyed to the heat roll fixing device 22 via the conveying device 21, and the toner image on the recording paper 20 is fixed on the recording paper by this heat roller fixing device. After that, the discharge roller 23
Then, the sheet is discharged to the sheet discharge tray 24. On the other hand, the photosensitive drum that has undergone the transfer process is cleaned by the cleaning device 25 to remove residual toner, and then erased by the eraser lamp 11 to start the next copying cycle. Although the toner particles that have not been transferred are removed by the cleaning device, they may not be completely removed, and some residual toner may remain.
When the resident toner comes into contact with the charging roller 13, it moves to the charging roller side, and when image formation is performed many times, there is a possibility that toner particles may adhere to the surface of the charging roller.
In order to eliminate such inconvenience, a scraper 26 such as an elastic blade is brought into contact with the surface of the charging roller to scrape off the toner adhering to the surface of the charging roller by the scraper, so that the surface of the charging roller is always kept clean. be able to. That is, since the insulating coating formed on the surface of the charging roller has high mechanical strength,
Even if 12 is brought into contact, the adhered toner particles can be removed without causing any inconvenience. In this case, it is desirable to use, as the insulating coating material, an insulating material having a small friction coefficient such as fluororesin. Further, the insulating film also has a function of protecting the electrode member. still,
Of course, the scraper 26 is not necessary when there is almost no residual toner or when the toner does not move to the charging roller side.

FIG. 3 is a schematic sectional view showing a detailed structure of the roller charging device. The charging roller 13 has a metal roller shaft 30,
A conductive elastic rubber layer 3 having a thickness of 5 mm is formed on the outer circumference of the roller shaft 30.
1 is formed, and a porous insulating coating 32 having a thickness of several 10 μm is formed on the conductive rubber layer. For the conductive rubber layer 31, an elastic rubber material such as natural rubber, silicon rubber, NBR rubber, chloroprene rubber, or polyurethane rubber mixed with conductive fine powder such as carbon, copper, aluminum, or tungsten is used. be able to. It is desirable that these conductive fine powders are fine powder materials having a particle size of several μm or less,
In particular, it is desirable to use a fine powder material having a diameter smaller than that of the pores formed in the insulating coating. By mixing the conductive fine powder material into the rubber material, the conductive fine powder material will be exposed on the surface and fine protrusions will be formed on the roller surface without any special fine processing or polishing. You can That is, it is sufficient that the conductive fine powder material is exposed on the surface. Alternatively, a conductive rubber having a small diameter may be impregnated in a rubber material to form the conductive rubber. If the conductive fibers are impregnated, the conductive fibers themselves form a conductive path and the tips of the conductive fibers are exposed on the surface of the rubber material layer, so a discharge electrode with a small diameter is formed without any special treatment. can do. Various methods can be used as a method for forming the conductive rubber layer 31 on the metal type roller shaft 30. For example, a conductive rubber layer is formed by interposing an adhesive layer between the roller shaft and the conductive rubber layer. The layer can also be adhesively fixed to the outer circumference of the roller shaft.

The porous insulating coating 32 is made of polyester, polyvinyl chloride,
It can be made of an electrically insulating material such as polyethylene, polypropylene, nylon, epoxy resin, or fluorine resin. In order to form fine pores of several μm or less in this insulating film, for example, an insulating resin is dissolved in various solvents, the conductive rubber layer is coated with this, and then the solvent is volatilized. be able to. The diameter of this fine hole is 10 μm
Hereafter, it is preferably several μm or less. The shaft portions 30a and 30b at both ends of the charging roller 13 having such a structure are rotatably supported by electrically insulating bearings 33a and 33b.
33a and 33b are supported by support plates 34a and 34b. Then, the bearing 32a is connected to the high-voltage power supply 15 via the brush connecting member 35. When the charging roller 13 is pressed against the photosensitive drum 10,
The conductive rubber layer 31 elastically deforms, and the porous insulating coating 32 on the outer periphery comes into contact with the photosensitive layer of the photosensitive drum 1 in a close contact state. On the other hand, since an air layer is formed in the area of the pores formed in the insulating coating 32, when a discharge voltage is applied to the conductive rubber layer 31 via the metal roller shaft 30, the insulating coating 32 will be removed. Air discharge occurs in the surface portion of the conductive rubber layer corresponding to the pores. At this time, since an electric field is formed between the conductive rubber layer and the base of the photosensitive drum, this electric field causes corona ions to be emitted toward the surface of the photosensitive drum through the pores, and the photosensitive layer is charged to a desired surface potential. Will be done. In this case, since the air discharge continues until the surface potential of the photosensitive layer approaches the discharge voltage, the surface of the photoconductor is charged to a potential almost equal to the discharge voltage. in this case,
Since the discharge current is almost equal to the discharge charge flow radiated toward the photoconductor, the discharge charge flow can be effectively used and the power consumption of the charging device can be further reduced. The charged area formed on the surface of the photosensitive layer by the discharge charge is an insulating film.
It is regulated by the diameter and the number of holes formed in 22. For example, when holes having a diameter of several μm are formed with an area ratio of about 30%, the average particle diameter of the toner particles should be 10 μm or more. If this is taken into consideration, no inconvenience will occur in the resolution of the reproduced image. In particular, when a toner image is fixed using a heat roll fixing device or a pressure fixing device, the toner adhering to the recording paper spreads during the fixing process, so that there is no inconvenience such as white spots on the image. In particular, in the printer device, since the line image is reproduced in a dot shape, the resolving power of the reproduced image is substantially governed by the resolving power of the exposure device, so that no inconvenience occurs on the image. Further, since the insulating film 32 is interposed between the charging roller 13 which is a discharge body and the photosensitive drum 10, and the insulating body is constantly maintained in the insulating state between the discharge body 13 and the photosensitive drum 10, the surface of the photosensitive drum is pinned. Even if scratches such as holes are generated, it is possible to effectively prevent the occurrence of breakdown. Moreover, even if the uncleaned toner adheres to the surface of the charging roller, if the pore size of the pores formed in the insulating film is set to be much smaller than the particle size of the toner particles, the scraper is brought into contact. The toner adhering to the outer circumference of the charging roller can be removed without clogging.

4A and 4B are diagrams showing the configuration of a modified example of the roller charging device. As shown in FIG. 4A, two charging rollers 40 and 41 having substantially the same charging width are arranged in pressure contact with the photoconductor 10. According to this structure, a portion of the surface of the photosensitive drum that is not directly charged due to the direct contact with the insulating film of the first charging roller 40 is charged by the second charging roller 41. The entire surface of the drum can be charged more densely.

Further, as shown in FIG. 4B, the charging width can be freely set according to the image width to be reproduced by combining charging rollers having different charging widths. For example, A-4 size (21
The first charging roller 42 having a charging width of 0 mm) and the second charging roller 43 having two charging rollers 43a and 43b having a charging width of 44 mm are used to charge the A-size and the A-3 size (297 mm ) Is charged. That is, the image reproduction width is A
In the case of -4 size, only the first charging roller 42 is turned on.
On the other hand, when performing A-3 size charging, both the first and second charging rollers 42 and 43 are turned on. According to this structure, since only the desired reproduction image width can be charged, the side lace is not necessary, which is particularly useful for a variable magnification type copying apparatus.

FIG. 5 is a diagram showing the configuration of another modification of the discharge device according to the present invention. In this example, the photosensitive belt is charged to a predetermined potential by using a charging belt. As the charging belt 50, a conductive elastic belt member having a porous insulating coating formed on the outer periphery thereof is used. The charging belt 50 is stretched over the two supporting rollers 51 and 52 so as to come into contact with the photosensitive drum 10 so as to run freely. The support rollers 51 and 52 are rotatably supported in an electrically insulated state by insulating bearings, while the support roller 52 and
Is connected to the high voltage power supply 15 via a brush connecting member. With this configuration, the charging belt 50 that functions as a discharge body
Since the contact length between the surface of the photosensitive drum and the surface of the photosensitive drum can be set long, the advantage that the charging time can be further extended is achieved. In this case, it is not necessary to match the traveling speed of the charging belt 50 to the peripheral speed of the photosensitive drum 10, and the traveling speed of the charging belt 50 may be set to be higher or lower than the peripheral speed of the photosensitive drum. it can. If the running speed of the charging belt is changed and set, the probability of facing the pores of the insulating film of the charging belt 50 of the photosensitive drum increases, and the uncharged surface area of the photosensitive layer surface can be reduced. Therefore, the surface of the photosensitive drum may be charged while the charging belt 50 is stopped. In this connection, as shown in FIG.
The discharge body 53 may be arranged in fixed contact with the electrode 10.
The discharge body 53 has a strip-shaped metallic discharge electrode member 54 extending over the image recording width, a conductive elastic rubber layer 55 is formed on the electrode member 54, and a porous insulating material is formed on the rubber layer. Film 56
Are formed. Then, the discharge body 53 is supported by the insulating support member 57 so as to be in pressure contact with the photosensitive drum 10. If a plate-shaped discharge body extending over the image recording width is used, the discharge body can be attached only by placing the discharge body in pressure contact with the photosensitive drum 10, and the mounting work is simplified and the structure is also improved. More simplified.

Also in the case of this example, an appropriate nip width can be formed by utilizing the elastic deformation of the conductive elastic rubber layer 55, and as a result, an appropriate charging time can be obtained.

FIG. 6 is a diagram showing the structure of a transfer device using the discharge device according to the present invention. A charging roller 60 is arranged in contact with the photosensitive drum 10 so as to be freely rotatable. The charging roller 60 has a metal roller shaft, a conductive elastic rubber layer is formed on the outer periphery thereof, and a porous insulating film is formed on the outer periphery of the rubber layer. This charging roller 60 is an insulating bearing (not shown)
Rotatably supported by. The recording paper 20 is synchronously conveyed according to the image forming operation, and enters between the photosensitive drum 10 and the charging roller 60. In synchronization with this approach of the recording paper 20,
A high-voltage power supply 61 applies a positive discharge voltage to the charging roller 60. In this case, since the Al base of the photosensitive drum 10 acts as a counter electrode, a strong electric field is generated between the charging roller and the Al base of the photosensitive drum, and positive discharge charges are discharged from the charging roller toward the recording paper 20. . As a result, a positive charge is accumulated on the back side of the recording paper 20 (the side not facing the photosensitive drum 10), and this positive charge forms a strong transfer electric field between the recording paper and the Al base of the photosensitive drum. The toner particles on the photosensitive drum are transferred to the recording paper side by the transfer electric field. In this case, a power source 61 for applying a discharge voltage to the charging roller 60
If the voltage is set to about 2500V, sufficiently good transfer efficiency can be obtained. Further, in this example, the charging roller 60
The charge eliminating roller 62 is arranged in the subsequent stage. This charge eliminating roller 62 is also configured in the same manner as the charging roller 61, and an AC discharge voltage is applied from an AC high voltage power source 63. A high-voltage AC neutralizing roller 62
Application to the photosensitive drum 10 from the charge eliminating roller 62.
Positive and negative corona charges are alternately discharged toward the side, and the charges accumulated on the back side of the recording paper 20 are removed by the corona charges, and the recording paper 20 can be separated from the photosensitive drum 10 well. In this case, an AC high voltage power supply in which an AC voltage is superimposed on a DC voltage can also be used as the AC high voltage power supply. Incidentally, also in this example, a scraper may be brought into contact with the charging roller 60 and the discharging roller 63 to remove the toner particles attached to the surfaces of the charging roller and the discharging roller.

FIG. 7 is a diagram showing an application example as a charge eliminating roller.
Since the discharge device according to the present invention is a charging system using air discharge, if a high voltage AC power supply is used as a discharge voltage source, positive charges and negative charges are alternately discharged. Therefore, when the surface of the insulator is charged with positive or negative charges, this charged charge can be effectively eliminated. Therefore, by connecting the discharge body according to the present invention to a high-voltage AC power source and bringing the porous insulating coating into contact with the surface of the insulator to be discharged, a charge eliminating device is constructed. In this example, the case where the surface of the heel roller of the heat roll fixing device 22 shown in FIG. 2 is neutralized will be described as an example. The heat roll fixing device 70 is
For example, it has a heat roller 71 in which a fluorine resin layer is coated on the outer peripheral surface of a hollow core made of Al and a backup roller 72 in which a silicon rubber layer is coated, and these heat roller and backup roller are pressure-bonded to each other. Composed. A heater 73 such as a halogen lamp is arranged in the internal space of the heat roller 71 to heat the heat roller 71 to a predetermined temperature. Recording paper 20 on which an unfixed toner image is formed
While passing between the heat roller 71 and the backup roller 72, the toner image on the recording paper is fused and fixed on the recording paper 20. In this heat roll fixing device, since fluorine resin and silicon rubber coated on the outer peripheral surface of the heat roller are insulating materials, frictional electrification occurs due to rotational driving of the heat roller, and the heat roller surface has a high surface potential of 1000 V or more. May be charged. When this charged electric charge has a polarity opposite to that of the toner, the toner on the recording paper is transferred to the heat roll side due to the electrostatic force due to the charged electric charge, which causes an undesirable offset phenomenon. Therefore, in this example, the static eliminator according to the present invention is used in order to neutralize the charged charges of the heat roller 71. This static eliminator has the same structure as that described with reference to FIG. 6, and uses a static eliminator roller 74 having a porous insulating film formed on the outer peripheral surface of the conductive elastic roller member as a discharge body. The static eliminating roller 74 is pressed against the heat roller 71 and rotatably arranged. Then, an AC high-voltage power supply is provided via a metal roller member and a brush connecting member.
Connect to 75. In the contact area where the static elimination roller 74 and the heat roller 71 face each other, the Al cored bar of the heat roller serves as a counter electrode, and the distance between the discharge electrode and the counter electrode of the static elimination roller 74 becomes an extremely small distance. Corona discharge occurs, and positive and negative discharge charges that are alternately generated are discharged toward the heat roller 71. As a result, the charge generated on the heat roller surface by frictional charging disappears,
The surface of the heat roller is always maintained at the surface potential of 0V. In this case, the plate-shaped discharge body shown in FIG. 5b may be used instead of the charge eliminating roller.
In addition, this static eliminator can remove static electricity not only on the surface of the heat roller but also on the surfaces of various insulating members, and can of course be used for static erasing the surface of the photosensitive drum and the surface of the transfer belt used in the transfer device.

8A and 8B show an example in which the discharge device according to the present invention is applied to a developing device. In this example, an example in which an insulating toner is charged by the charging device according to the present invention to form a one-component non-magnetic developing device will be described. A developing device housing 80 is arranged so as to face the photosensitive drum 10. Insulating toner 81 is stored in the developing device housing 80, and this toner is supplied to the developing roller 83 by rotating the toner carrying bar 82.
A hollow sleeve roller made of Al is used as the developing roller 83, and the outer peripheral surface of the sleeve roller is sandblasted. A plate-shaped discharge body 84 shown in FIG. 5B is placed in contact with the developing roller 83, and the discharge body 84 is discharged by a high-voltage power supply.
Connect to 85. As described above, in the discharge body 84, the conductive elastic rubber layer is formed on the metal electrode member, the insulating coating is formed on the conductive elastic rubber layer, and the insulating coating is formed on the developing roller 83. Place it so that it is lightly pressed against. The toner supplied to the developing roller 83 is transported to a position facing the discharge body 84 as the developing roller rotates while being accommodated in the minute recesses on the outer peripheral surface of the developing roller. Then, a toner layer having a uniform thickness is formed by passing between the developing roller 83 and the discharge body 84. At this time, the toner layer is interposed between the discharge body 84 and the developing roller 83, and the toner layer is charged by the discharge charge discharged from the discharge body 84. Due to the electrostatic charge of the toner, electrostatic charges of opposite polarity are electrostatically induced in the developing roller 83, and the toner particles are held on the developing roller by the attraction force acting between the induced charges and the toner charges. Then, the charged toner is transferred to a position facing the photosensitive drum 10 while being held by the developing roller 83, and the electrostatic latent image on the photosensitive drum 10 is visualized. In the embodiment shown in FIG. 8b, a roller-shaped discharge body 90 is used instead of the plate-shaped discharge body. This discharge body 90 is connected to the developing roller 83
And is rotated opposite to the developing roller. The toner supplied to the developing roller 83 is charged by the electric charge discharged from the discharge body at a position facing the roller discharge body 90,
Photosensitive drum 10 held on the developing roller by induced charge
The electrostatic latent image above is visualized. As described above, the charging device according to the present invention can also be used for charging the toner, and by utilizing the charging device according to the present invention, a non-magnetic one-component developing device can be configured.

The present invention is not limited to the above-described embodiments, and various changes and modifications can be made. For example, in the above-described embodiment, the example in which the discharge body is brought into contact with the surface of the object to be charged for charging has been described. It is also possible to use it by interposing an air layer of, for example, about 100 μm with the surface of the object.

Further, in the above-mentioned embodiment, the conductive elastic rubber layer is formed on the base electrode member, and the porous insulating coating is formed on the conductive rubber layer.However, the minute protrusions are formed on the outer peripheral surface. It is also possible to form a porous insulating film directly on the formed metallic electrode member to form a discharge body. Such a discharge body is particularly effective when the object to be charged has flexibility or deformability.

(Effects of the Invention) The effects of the present invention described above are summarized as follows.

(1) An electrode member having a porous insulating coating formed on the outer peripheral surface is used as a discharge body, and this discharge body is placed in contact with or close to the surface of the object to be charged, and the surface of the electrode member is insulated. Since the object to be charged is charged by the discharge charge emitted through the pores of the coating film, the distance from the discharge electrode to the surface of the object to be charged can be set to an extremely small distance,
As a result, the discharge starting voltage is further lowered, and the ozone generation amount can be further reduced. Furthermore, since the minute projections having a large curvature formed on the surface of the electrode member are used as the discharge electrodes, the discharge starting voltage can be further reduced.

(2) Since the distance from the discharge electrode to the surface of the object to be charged can be regulated by the film thickness of the insulating coating, the surface of the object to be charged can be charged to a potential almost equal to the discharge voltage.

(3) Since the distance between the discharge electrode and the object to be charged is regulated by the film thickness of the insulating coating, the work of setting the discharge body is further facilitated.

(4) If the discharge body is formed in the shape of a roller and the discharge body is driven to rotate, the surface of the discharge body can be cleaned simply by bringing the slapper into contact with the discharge body. There is no inconvenience.

(5) Since most of the discharge charge discharged from the discharge electrode is used only for charging the object to be charged, the discharge current becomes extremely small, and the power consumption of the charging device can be further reduced.

(6) Since the insulating coating formed on the outer peripheral surface of the electrode member functions as an insulating material layer interposed between the object to be charged and the discharge electrode, the risk of dielectric breakdown is avoided and, for example, photosensitive It is possible to prevent the base of the drum and the discharge electrode from being directly short-circuited, and to prevent the occurrence of breakdown even if there are pinholes or the like on the photosensitive drum.

(7) Since the roller charging device according to the present invention can be applied to a transfer device, it is possible to construct a transfer device with an extremely small amount of ozone generated.

(8) Since the charging device according to the present invention can be applied to charge the insulating toner, the non-magnetic one-component developing device can be constructed with a simple structure by using the charging device according to the present invention.

(9) If an AC high-voltage power supply is used as the high-voltage power supply, an AC static eliminator that produces an extremely small amount of ozone can be configured.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the principle of the charging device and the static eliminator according to the present invention, and FIG. 2 is a diagram showing the configuration of an example of a printer device including the charging device and the static eliminator according to the present invention. FIG. 4 is a diagrammatic sectional view showing the configuration of a roller charging device according to the present invention, FIGS. 4A and 4B are diagrams showing the configuration of a modified example of the roller charging device according to the present invention, and FIGS. FIG. 6 is a diagram showing a configuration of a modified example of the charging device according to the invention, FIG. 6 is a diagram showing a configuration when the charging device according to the invention is applied to a transfer device, and FIG. 8A and 8B are diagrams showing an example of a non-magnetic one-component developing device using the charging device according to the present invention. 1 ... Base electrode member, 2 ... Carbon particles 3 ... Conductive rubber layer, 4 ... Conductive path 5 ... Porous insulating coating, 6 ... Discharge body 7 ... Uncharged material, 9 ... DC High-voltage power supply 10 …… Photosensitive drum, 13 …… Charging roller 20 …… Recording paper, 64 …… AC high-voltage power supply.

Claims (7)

[Claims] 1. An electrode member, a discharge body having a porous insulating coating formed on at least a part of an outer peripheral surface of the electrode member, a support member for supporting the discharge body in an insulating state, and the electrode. A power supply device for applying a discharge voltage to the member, the discharge being discharged from the surface of the electrode member through the pores of the porous insulating film to charge the object to be charged to a predetermined potential. apparatus. 2. The discharge device according to claim 1, wherein minute protrusions having a diameter smaller than the hole diameter of the holes of the porous insulating film are formed on the outer periphery of the electrode member. 3. The electrode member is made of a metal material having fine protrusions formed on the outer periphery thereof, and a porous insulating film is formed on the outer periphery of the metal material. The discharge device described. 4. The electrode member includes an elastic material layer containing a conductive substance, and the porous insulating coating is formed on an outer peripheral surface of the conductive elastic material layer. 2. The discharge device according to 2. 5. The discharge device according to claim 1, wherein the discharge body is formed in a roller shape, and the discharge body is rotatably supported by the support member. 6. The discharge device according to claim 5, further comprising a scraper for removing foreign matter adhering to the surface of the insulating film. 7. The power supply device according to claim 1, wherein the power supply device is an AC power supply or a power supply device that generates a voltage in which an AC voltage is superimposed on a DC voltage. Discharge device.