JP2500903B2 - Electrophotographic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus applicable to printers, facsimiles and the like.

[0002]

2. Description of the Related Art Conventional electrophotographic developing methods include a cascade developing method, a touchdown developing method, a jumping developing method and the like. Among them, a cascade developing method shown in US Pat. No. 3,105,770 is known as a developing method in which a developer is directly sprinkled with a developer. The cascade developing method is the first developing method used in an electrophotographic copying machine.

Further, an AC bias is applied to the developing roller 1
U.S. Pat. No. 38 as a method for flying and developing a component toner
There is 66574. In this invention, it is explained that the AC bias applied to the developing roller is used for the purpose of activating the movement of the toner, and that the toner reaches the image portion and flies back on the way in the non-image portion.

Further, as a modification of the technique of applying the AC bias, there is a jumping developing method disclosed in Japanese Patent Publication No. 63-42256. This jumping developing method is a developing method in which toner is carried on a toner carrier and conveyed to a developing unit, where the toner is attached to the image part of the photoconductor by an AC bias. This Japanese special public Sho 63-42
The technical idea of the 256 publication is that the toner reciprocates in the image portion and the non-image portion in the above-mentioned US Pat.
866574.

[0005]

As is well known in the art, the cascade development method is not good at reproducing solid images. Further, there is a problem that the device becomes large and complicated. Further, US Pat.
The 6574 developing device has a drawback that the device is required to have high accuracy and is complicated and high in cost. In the jumping development method, since a photoreceptor is developed by a toner carrier carrying a toner layer, it is essential to form an extremely uniform thin layer on the toner carrier in order to obtain high image quality. Further, in this method, a so-called sleeve ghost phenomenon often occurs in which a history of the previous image remains in the thin toner layer on the toner carrier and an afterimage appears in the image. Further, there is a drawback that the device is complicated and the cost is high.

In view of the above problems, an object of the present invention is to provide an electrophotographic apparatus having a simple structure and high image quality. Further, the present invention provides an excellent electrophotographic apparatus which can cope with a high speed process. Further, the present invention provides an electrophotographic apparatus that smoothes the flow of the developer in the developer reservoir and prevents the developer from being crushed by its own weight to cause clogging between the photoconductor and the electrode roller. To do.

[0007]

In order to solve the above problems, the present invention is directed to an electrostatic latent image holder that contains a fixed magnet and moves, and an electrostatic latent image is formed on the electrostatic latent image holder. Forming means, a developer reservoir for supplying a magnetic developer to the image portion and non-image portion of the electrostatic latent image holding member on which the electrostatic latent image is formed by the fixed magnet, and the electrostatic latent image holding member. The electrode roller that is installed with a predetermined gap from the surface of the electrostatic latent image carrier and that moves in the direction opposite to the moving direction of the electrostatic latent image carrier, and the magnetic developer in the non-image area on the electrostatic latent image carrier Means for applying a direct current voltage superposed on the alternating current voltage to the electrode roller, a removing member for scraping off the magnetic developer adhering to the electrode roller, and the electrostatic latent image provided inside the developer reservoir. A developer flow control member installed between a carrier and the electrode roller. Preparative an electrophotographic apparatus according to claim.

[0008]

The present invention uses an electrostatic latent image holder containing a fixed magnet that does not rotate. A developer is sprinkled and magnetically adhered to the electrostatic latent image holder on which an electrostatic latent image is formed. In this configuration, the toner is carried and conveyed to an electrode roller, an AC bias is applied to the electrode roller, and the non-image portion toner of the electrostatic latent image holder is removed by electrostatic force and magnetic force. That is, the present invention adds two improvements to the cascade development method, in which a fixed magnet that does not rotate is installed inside the electrostatic latent image holding member and an AC voltage is applied to the electrodes,
It is smaller and has higher performance. In the present invention, development is almost completed when toner is first sprinkled on the electrostatic latent image holding member. The electrode roller part circulates the toner in the developer reservoir and at the same time collects the toner in the non-image part of the electrostatic latent image.

The technical idea of the present invention will be described with reference to FIG. Reference numeral 1 is an electrostatic latent image holder on which an electrostatic latent image is formed, 2 is toner, 3 is a developing electrode, 4 is a magnet, and 5 is a power source. In the conventional method, as shown in (b), toner is attached to the image portion of the electrostatic latent image holding member to obtain the toner image of (c). On the other hand, in the present invention, as shown in (d), the magnetic developer is once attached to the entire surface of the electrostatic latent image holder by magnetic force, and then (e).
As shown in (1), the toner is taken from the non-image portion by the magnetic force and the electrostatic force. That is, the conventional example is a “developing method for adhering toner to the image portion”, and the present invention can be said to be a “developing method for stripping off toner in unnecessary non-image portion”.

Due to such a difference in technical idea, the electrode roller of the present invention and a conventional method, for example, Japanese Patent Publication No. 63-42256.
The difference from the developing roller of the publication is as follows. (1) It is the electrostatic latent image carrier that carries and carries the developer from the developer reservoir to the developing section. (2) In the conventional developing roller, the surface carrying the toner layer is always opposed to the electrostatic latent image holding member. On the other hand, in the electrode roller of the present invention, the bare surface always faces the electrostatic latent image holding member. (3) In the conventional example, the developing roller and the electrostatic latent image carrier move in the same speed and in the same direction. However, in the present invention, the electrode roller rotates in the opposite direction.

That is, in the present invention, the electrostatic latent image carrier carries the developer from the developer reservoir to the developing section, and the toner collected by the bare electrode roller is immediately removed from the developing section by the reverse rotation. Is.

Due to such a difference in structure, the following difference in action and effect occurs. If the electrostatic latent image holding member and the roller move at the same speed and in the same direction as in Japanese Patent Publication No. 63-42256, the toner returned from the image portion of the electrostatic latent image holding member to the roller due to the reciprocating motion is again. You can return to the image section with. However, when the roller rotates in the reverse direction as in the present invention, once the toner moves to the roller side, the surface of the electrostatic latent image holding member facing next is different from the original electrostatic latent image holding member surface, and therefore the toner is the same again. You cannot go back to the place. That is, assuming that reciprocating motion occurs in the image portion in the reverse rotation as in the present invention, a visible image with toner cannot be obtained in principle. Therefore, the effect of the AC voltage applied to the electrode roller in the present invention is as follows.
"Reciprocating motion of toner" disclosed in Japanese Patent Laid-Open No. 3-42256
Instead, it is assumed to be close to the “activation of toner movement” shown in US Pat. No. 3,866,574. Here, in the present invention, since the toner is collected on the bare surface of the electrode roller, there is a new effect that the sleeve ghost phenomenon caused by the uneven thickness of the toner layer, which has been a problem in the past, does not occur. Further, since the transport movement of the developer can be used also as the rotation movement of the electrostatic latent image holding member, the construction of the developing device can be simplified and the entire apparatus can be downsized.

Further, in the present invention, the developer supplying section can magnetically attract the developer by the internal magnet of the electrostatic latent image holding member to supply a large amount to the electrostatic latent image holding member. That is, since the developing width is large, it is possible to provide an excellent developing device having a simple structure of the entire device and capable of supporting high-speed processes.

As the charging device used in the present invention, a commonly used corona charger and further a scorotron charger having a grid electrode are used. Further, any type of charging device such as a roller charging device made of an elastic rubber material or a conductive fur brush charging device can be used as long as it is a charging device normally used in an electrophotographic apparatus.

The present invention uses an electrostatic latent image holder containing a magnet. This magnet does not rotate but only the electrostatic latent image carrier rotates. At this time, if the magnet and the electrostatic latent image holder are supported coaxially, there is an advantage that the mechanism for driving the electrostatic latent image holder can be simplified and the magnetic pole position can be easily adjusted.
The maximum magnetic flux density of the magnet inside the electrostatic latent image carrier used in the present invention needs to be 300 gauss or more on the surface of the electrostatic latent image carrier, and is preferably 500 to 1200 gauss. 30
When it is 0 Gauss or less, the effect of the magnetic force is weakened, the uniformity of the image is lost, and the toner is easily clogged with the electrode roller. Further, in order to improve the transportability of the developer and the motility of the toner during development, the magnetic pole position of the magnet inside the electrostatic latent image holding member is set to the electrostatic latent image holding member and the electrode roller. It is preferable to set it at the closest position or at a position upstream thereof. This angle θ is preferably in the range of 0 ° to 30 °. The range of the magnetic pole angle is based on the assumption that the diameter of the photoconductor drum is 30 mm, and it is natural that this value becomes small when the diameter of the photoconductor is large.

As the electrostatic latent image carrier used in the present invention, zinc oxide, selenium, cadmium sulfide, amorphous silicon, or an organic photoconductor using phthalocyanine or an azo pigment can be used. Needless to say, ordinary electrostatic recording paper or the like may be used. The surface of the electrostatic latent image carrier may be roughened by sandblasting or the like in order to accelerate the formation of the developer layer.

In the present invention, a developer reservoir having an opening on the surface of the electrostatic latent image carrier is used. The developer is configured to come into direct contact with the electrostatic latent image holding member from the developer reservoir, and the developer is magnetically attracted to the electrostatic latent image holding member regardless of whether or not it is charged. The width of the opening of the developer reservoir facing the electrostatic latent image holder in the moving direction of the electrostatic latent image holder is required to be 5 mm or more, and preferably 10 to 15 mm. When this width is 5 mm or less, the image density becomes extremely low.

The magnetic developer used in the present invention is preferably an insulating one-component toner. If a one-component toner is used, the device configuration can be simplified. The one-component toner used in the present invention is obtained by dispersing powder of magnetite or ferrite together with a charge control agent in a binder resin such as styrene resin or acrylic resin, pulverizing and classifying. This toner may be a powder obtained by spray drying or a powder chemically obtained by a pearl polymerization method or the like. The average particle diameter of the toner used is preferably 15 μm or less, but if it is 12 μm or less, a sharper image can be obtained.

In the present invention, a two-component developer comprising toner and magnetic carrier can be used. The toner used in the present invention is obtained by dispersing a color pigment such as carbon black or phthalocyanine in a binder resin such as an acrylic resin or a polyester resin, pulverizing and classifying. The toner may be a powder obtained by spray drying, or a powder chemically obtained by a pearl polymerization method, an emulsion polymerization method, or the like. Further, the toner particles may be directly mixed with a carrier, or silica particles or fluororesin fine powder may be adhered to the surface of the toner. The average particle diameter of the toner used is preferably 15 μm or less, but 12 μm
A sharper image can be obtained by the following.

The carrier used in the present invention is a magnetic substance such as iron powder or ferrite powder, or a powder whose surface is coated with a resin, or a fine powder such as ferrite powder or magnetite in a proportion of about 30-80%. A magnetic powder that is dispersed and mixed in a resin, an epoxy resin, a styrene-acrylic resin, and pulverized and classified is used. The average particle size of the carrier is 30
The thickness is preferably 0 μm or less, but particularly 150 μm or less, the toner can be uniformly charged.

The distance between the electrode roller and the electrostatic latent image carrier is
100 μm to 700 μm when a one-component toner is used
Degree: 400 μm to 2 m when using a two-component developer
It is installed about m away.

The material of the electrode roller may be conductive.
When the fluidity of the developer is poor, if the electrode roller is made of a magnetic material, the magnetic lines of force from the magnet inside the electrostatic latent image carrier reach the electrode roller, and as a result, the developer transportability is improved. Examples of such a material include soft iron, magnetic stainless steel, nickel and the like. The surface of the electrode roller may be a polished one, or may be one in which the surface is made uneven by sandblasting or the like or a groove is carved.

The electrode roller may be a non-magnetic roller having a non-rotating magnet fixed inside. For example, there is a configuration in which a magnet is inserted into a cylinder made of non-magnetic stainless steel or aluminum.
The magnetic pole of the magnet inside the electrode roller is preferably opposite in polarity to the magnetic pole of the magnet inside the electrostatic latent image holding member.

An AC voltage is applied to this electrode roller. Of course, a pulse waveform or a triangular wave may be used as long as an alternating electric field is effectively applied to the electrostatic latent image holder.
The frequency of this alternating voltage varies depending on the image forming process speed, and is in the range of approximately 50 Hz to 5000 Hz, preferably in the range of 300 to 3000 Hz. The value of the AC voltage is the value of zero to peak, which is about 0.5 to 3 of the charging potential of the electrostatic latent image holding member.
A double value is preferable, and a value of 0.5 to 2 is preferable. In the case of reversal development, if the value of the DC voltage superimposed on the AC voltage is set equal to or lower than the charging potential of the electrostatic latent image carrier by several tens of percent, a good negative-positive reversal image can be obtained. . On the other hand, in the case of normal development, a good positive image can be obtained by setting the value to be equal to or higher than the background potential of the electrostatic latent image carrier by several tens of percent.

When the rotating direction of the electrode roller is opposite to the moving direction of the electrostatic latent image holding member at the developing position,
High image quality can be obtained, and the device configuration can be simplified.

In order to effectively remove the fog on the electrostatic latent image carrier, it is preferable to increase the moving speed of the electrode roller. On the other hand, the slower the moving speed of the electrode roller, the more carefully the toner on the electrostatic latent image carrier can be removed. The speed of the electrode roller is preferably in the range of 0.3 to 2.0 times the moving speed of the electrostatic latent image carrier.

The developer adhering to the electrode roller is scraped off by a removing member provided in the developer reservoir and returned to the developer reservoir again. The removing member is preferably electrically insulated so as not to affect the electrode roller. Therefore, for example, a plastic such as a polyester film is preferable for the removing member. The removing member may be made of stainless steel, phosphor bronze plate, or the like, but at this time, in order not to electrically affect the electrode roller, make sure that it does not come into electrical contact with anything other than the electrode roller. Needs to be insulated. Further, it goes without saying that a member for removing the developer such as a roller to which a voltage is applied or a magnet from the electrode roller is effective as the removing member.

The developer flow control member is provided inside the developer reservoir and is provided between the electrostatic latent image carrier and the electrode roller. By providing at this position, the developer in the developer reservoir has an effect as a damper for preventing clogging of the developer in the nip portion between the electrostatic latent image holding member and the electrode roller due to gravity or impact. Further, it has an effect as a developer guide for smoothing the circulation of the developer in the developer reservoir as shown by the arrow in FIG. 5 and improving the image quality.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic apparatus of the present invention will be described below with reference to the drawings.

Concrete Example 1 FIG. 2 shows an example of the electrophotographic apparatus of the present invention. In FIG. 2, 6 is an organic photoconductor drum in which phthalocyanine is dispersed in a polyester binder resin, 7 is a magnet which is fixed coaxially with the photoconductor 6 and has 7 magnetic poles which do not rotate, and 8 is a negative charge on the photoconductor. Corona charger, 9 is a grid electrode for controlling the charging potential of the photoconductor, 1
0 is a signal light, 11 is a developer reservoir, 12 is an average particle size of about 10
A negatively chargeable magnetic one-component toner of μm, and 13 is a toner guide. The magnet 7 has magnetic poles of three poles attracting each other at a portion facing the developer reservoir 11, and magnetic poles of four poles mutually repelling at a repulsive magnetic field portion 14 on the opposite side with respect to the axis. . Reference numeral 15 is an electrode roller made of stainless steel having magnetism, 16 is an AC high voltage power source for applying a voltage to the electrode roller, 17 is a scraper made of a polyester film for scraping off toner on the electrode roller, and 18 is a paper image of a toner image on the photoconductor. It is a transfer corona charger that transfers to.
Reference numeral 19 is a recovery unit for recovering the toner splashed by the repulsive magnetic field unit 14. The magnetic flux density on the surface of the photoconductor 6 is 800
It is Gs. The photoconductor 6 has a diameter of 30 mm and a peripheral speed of 30 m.
It was rotated at m / s.

The magnetic one-component toner used was composed of 70% polyester resin, 25% ferrite, 3% carbon black, and 2% oxycarboxylic acid metal complex, and 0.4% colloidal silica was added externally. (All were weight%).

The operation of the electrophotographic apparatus configured as described above will be described below with reference to FIG. Photoconductor 6
Was charged to -500V by a corona charger 8 (applied voltage-4kV, grid 9 voltage-500V). The photoconductor 6 was irradiated with a laser beam 10 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V. On the surface of the photoconductor 6, a magnetic one-component toner 12 is stored in a developer reservoir 11
It is attached by magnetic force inside. At this time, the toner was charged to approximately −3 μC / g. Next, the photoconductor 6 having the toner layer attached thereto was passed in front of the electrode roller 15. The electrode roller 15 was installed at a distance of 300 μm from the photoconductor 9. A high voltage power supply 16 is applied to the electrode roller 15 so that the electrode roller 15 shown in FIG.
400 of the waveform shown in FIG.
An AC voltage (frequency 300 Hz) of V0-p (peak-to-peak 800V) was applied. The toner layer on the photoconductor 6 moves between the photoconductor 6 and the electrode roller 15, and the toner in the non-image area gradually moves to the side of the photoconductor 6
A negative-positive inverted toner image remained only on the image portion on the upper portion. The toner adhering to the electrode roller 15 rotating in the direction of the arrow was scraped off by the scraper 17 and returned to the developer reservoir 11 to be used for the next image formation. The toner image thus obtained on the photoconductor 6 is transferred onto a sheet of paper (not shown) by the transfer charger 18, and then a fixing device (not shown).
It was fixed by heat. On the other hand, the toner remaining on the photoconductor 6 after the transfer is transferred to the photoconductor 6 by the repulsive magnetic field portion 14 as the photoconductor 6 moves.
It is splashed from the surface and collected in the collection unit 19. In some cases, the toner repelled in the repulsive magnetic field portion is partially returned to the surface of the photoconductor, but at this time, the portion passing through the repulsive magnetic field portion adheres to the surface of the photoconductor in a dispersed state. Subsequent charging exposure has virtually no effect.

The photoconductor 6 is charged again by the corona charger 8.
Used in the next imaging step. As a result, a sharp image with no toner scattering was obtained.

In the embodiment, the repulsive magnetic field portion is provided with a collecting portion for collecting the splashed toner. However, since the toner repelled once and adhering to the surface of the photoreceptor again is well dispersed, the amount of the toner may be small. If it does not affect the next process. Therefore, if the magnetic field configuration is such that the dispersed toner adheres to the surface of the photoconductor again, the recovery unit 19 may be omitted.

Concrete Example 2 The constitution of FIG. 4 is different from the constitution of FIG. 2 in that the magnetic developer is a two-component developer in which toner and carrier are mixed. Further, the electrode roller 20 is provided with a fixed magnet 21. Other configurations are the same as those in FIG. The toner used consisted of 93% of styrene acrylic resin, 5% of carbon black and 2% of metal complex of oxycarboxylic acid, and 0.1% of colloidal silica was added externally (all are% by weight).
A two-component developer 22 prepared by mixing a ferrite powder carrier having a particle size of 100 μm and a toner, the surface of which was coated with a silicone resin, was placed in the developer reservoir, and magnetically attached to the surface of the photoconductor 6. When the photoconductor 6 on which the electrostatic latent image was formed was passed through the developer 22, the two-component developer 22 was adsorbed on the surface of the photoconductor. Further, when passing through the electrode roller 20, only the toner in the image portion passed through the electrode roller 20, and a toner image was obtained on the photoconductor 6. The obtained toner image was transferred onto paper (not shown) by the transfer charger 18, and then heat-fixed by a fixing device (not shown). On the other hand, after the transfer, the photoconductor 6 was charged again by the corona charger 8 and used in the next image forming step. As a result, a sharp image with no toner scattering was obtained.

Concrete Example 3 In FIG. 5, 23 is an organic photosensitive drum in which phthalocyanine is dispersed in a polyester binder resin, 24 is a non-rotating magnet fixed coaxially with the photosensitive body 23, and 25 is a minus surface of the photosensitive body. Is a corona charger, which is charged to the surface, 26 is a grid electrode that controls the charging potential of the photoconductor, 27 is signal light, and 2
Reference numeral 8 is a developer reservoir, 29 is a magnetic one-component developer, 30 is a non-magnetic electrode roller set with a gap from the photoconductor 23, 31 is a non-rotating fixed magnet installed inside the electrode roller 30, 32 Is a high voltage AC power source for applying a voltage to the electrode roller 30, 33 is a scraper made of polyester film for scraping off the developer on the electrode roller, and 34 is a transfer corona charger for transferring the toner image on the photoconductor onto paper.
35 makes the flow of the developer in the developer reservoir smooth,
Further, it is a damper for preventing the developer from being crushed by its own weight and causing clogging between the photoconductor and the electrode roller. The magnetic flux density on the surface of the photoconductor 23 is 600 Gs. The magnetic flux density on the surface of the electrode roller 30 is 800 Gs. The magnetic force inside the electrode roller is stronger than the magnetic force inside the photoconductor to improve the transportability. The magnet 24 shown in the figure
The magnetic pole angle θ was set to 15 °. The diameter of the photoconductor 23 is 3
It was used by rotating it in the direction of the arrow in the figure at 0 mm and a peripheral speed of 60 mm / s. The diameter of the electrode roller 30 is 16 mm, and the peripheral speed is 4
The photosensitive member was rotated at 0 mm / s in the direction opposite to the advancing direction of the photoconductor (the direction of the arrow in the figure). Photoconductor 23 and electrode roller 30
The gap between and was set to 300 μm.

As the magnetic one-component developer, fine particle insulating magnetic one-component toner having a particle size of 5 μm was used. The composition of the magnetic one-component toner is 70% polyester resin, 25% ferrite,
Carbon black 3%, Oxycarboxylic acid metal complex 2%
Further, 1% of colloidal silica was externally added and used (all are% by weight).

The photosensitive member 23 is charged with a corona charger 25 (applied voltage −4.5 kV, grid voltage −500 V).
It was charged to 500V. Laser light 27 is applied to the photoconductor 23.
Was irradiated to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -90V. The toner 29 was magnetically attached to the surface of the photoconductor 23 in the developer reservoir 28. Next, the photoconductor 23 was passed in front of the electrode roller 30. When passing through the uncharged area of the photoconductor 23, a DC voltage of 0V was superposed on the electrode roller 30 by the AC high voltage power supply 75.
An AC voltage (frequency 1 kHz) of 0V0-p (peak-to-peak 1.5 kV) was applied. Then -50
When passing through the photoconductor 23 charged to 0V and having an electrostatic latent image written therein, an AC high voltage power source 32 is applied to the electrode roller 30
AC voltage of 750V0-p (peak-to-peak 1.5kV) superposed with DC voltage of -350V (frequency 1
kHz) was applied. Then, the toner attached to the charged portion of the photoconductor 23 is collected by the electrode roller 30, and
A negative-positive inverted toner image remained only on the image portion on the upper portion. The toner attached to the electrode roller 30 rotating in the direction of the arrow was scraped off by the scraper 33, returned to the developer reservoir 28, and used for the next image formation. The state of toner circulation in the developer reservoir 28 is indicated by a dashed arrow. The toner image thus obtained on the photoconductor 23 is printed on paper (not shown).
After transfer by the transfer charger 20, heat fixing was performed by a fixing device (not shown). As a result, the horizontal lines are not disturbed and the toner is not scattered, and the solid is uniform and the density is 1.5.
An extremely high-resolution and high-quality image in which lines / mm lines were reproduced was obtained.

Concrete Example 4 In FIG. 6, 36 is an organic photosensitive drum in which phthalocyanine is dispersed in a polyester binder resin, 37 is a fixed magnet which is fixed coaxially with the photosensitive member 36 and which does not rotate. Maximum magnetic flux density on the surface is 800 Gs
Is. 38 is a corona charger for negatively charging the photoconductor, 39 is a grid electrode for controlling the charging potential of the photoconductor,
40 is a signal light, 41 is a developer reservoir, and 42 is an average particle size of about 1
Negatively chargeable magnetic one-component toner of 0 μm, and 43 is a toner guide. 44 is a fixed magnet 4 that does not rotate inside
5, an aluminum electrode roller having 5; an AC high voltage power supply for applying a voltage to the electrode roller; 47, a scraper made of polyester film for scraping off the toner on the electrode roller; 48, a toner image on the photoconductor is transferred to paper. It is a transfer corona charger. The magnet 37 has a magnetic pole formed at a portion facing the developer reservoir 41. Further developer reservoir 4
The width A of the opening 49 facing the photoconductor 36 of No. 1 is about 15
It is set to mm. The width A referred to here is the photosensitive member 36.
And the distance from the closest portion of the electrode roller 44 to the developer reservoir end 50 along the surface of the photoconductor 36. The diameter of the photoconductor 36 is 30 mm, and the peripheral speed is 120 mm /
It was rotated by s. Electrode roller 44 has a peripheral speed of 100 mm / s
Then, it was rotated in the direction of the arrow. Reference numeral 51 is a cleaner for cleaning the toner remaining on the photoconductor after transfer.

The composition of the magnetic one-component toner used is composed of 70% of polyester resin, 25% of ferrite, 3% of carbon black and 2% of metal complex of oxycarboxylic acid, and 0.4% of colloidal silica is externally added. (All were weight%).

The operation of the electrophotographic apparatus configured as described above will be described below with reference to FIG. Photoconductor 3
6 to a corona charger 38 (applied voltage-4 kV, grid 3
It was charged to -500V at a voltage of 9-500V). The photoconductor 36 was irradiated with laser light 40 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V.
Magnetic one-component toner 42 is attached to the surface of the photoconductor 36 in the developer reservoir 41 by magnetic force. At this time, the toner was charged to approximately −3 μC / g. Next, the photoconductor 36 having the toner layer attached thereto was passed in front of the electrode roller 44. This electrode roller 44 is 300 μm thick with the photoconductor 36.
It was installed with the distance between. The electrode roller 44 has a high voltage power source 4
6, 400 V0-p (peak-to-peak 80) of the waveform shown in FIG.
An alternating voltage of 0 V (frequency 300 Hz) was applied. The toner layer on the photoconductor 36 moves between the photoconductor 36 and the electrode roller 44, and the toner in the non-image area gradually moves to the electrode roller 4.
After moving to the No. 4 side, the negative-positive inverted toner image remained on the image portion on the photoconductor 36. The toner adhering to the electrode roller 44 rotating in the direction of the arrow was scraped off by the scraper 47, returned to the developer reservoir 41 and used for the next image formation. After the toner image thus obtained on the photoconductor 36 is transferred onto a paper (not shown) by the transfer charger 48,
Heat fixing was performed by a fixing device (not shown). The surface of the photoconductor after the transfer is cleaned by the cleaner 51, and the corona charger 3 is again used.
It was charged at 8 and used in the next image forming step. As a result, a sharp image with no toner scattering was obtained.

Concrete Example 5 The structure shown in FIG. 7 is an example in which the electrophotographic apparatus of the present invention is applied to an analog copying machine. The structure shown in FIG. 6 is an optical system for exposing a photoconductor and a toner as the photoconductor. The point of having a reverse polarity charging property,
Also, the voltage applied to the electrode roller is different. Other configurations are the same as those in FIG. Similar elements are given the same numbers as in FIG. The toner 42 used is styrene-acrylic resin 68%, ferrite 25%, carbon black 5%,
A nigrosine dye of 2% was used, and colloidal silica was externally added by 1% (both by weight).

The charging of the photoconductor 36 is the same as in the case of FIG. Reference numeral 52 denotes a manuscript table which serves as a light source 53 for manuscripts placed thereon.
While illuminating with, constant speed mirror 54 and half speed mirrors 55, 5
When scanning is performed at 6, the reflected light of the document forms an image on the photoconductor 36 via the lens 57 and the mirror 58, and a latent image is formed as the photoconductor moves.

When the toner 42 is passed through the photoconductor 36 on which the electrostatic latent image is formed, the toner 42 is adsorbed on the surface of the photoconductor, and when it passes through the electrode roller 44, only the toner in the image portion passes through the electrode roller 44. Then, a positive regular toner image was obtained on the photoconductor 36. At this time, the voltage applied to the electrode roller is -150V as shown in FIG. 8 unlike the case of FIG.
400V0-p (peak to
It is an AC voltage (frequency 300 Hz) with a peak of 800 V.

The obtained toner image is transferred onto a sheet of paper (not shown) by a transfer charger 48, and then a fixing device (not shown).
It was fixed by heat. On the other hand, after transfer, the corona charger 3 again
The photosensitive member 36 was charged at 8 and used in the next image forming step. As a result, a sharp image with no toner scattering was obtained.

Although the above-mentioned embodiment uses the one-component magnetic toner, the present invention can be similarly applied to the two-component magnetic developer using the carrier.

[0047]

According to the present invention, an electrophotographic apparatus having a simple structure and high image quality can be obtained. Further, an excellent electrophotographic apparatus that can handle high-speed processes can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view explaining a difference in technical idea between a conventional method and the present invention.

FIG. 2 is a configuration diagram of an electrophotographic apparatus according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing a waveform of an AC voltage used in the first and fourth embodiments of the present invention.

FIG. 4 is a configuration diagram of an electrophotographic apparatus according to a second embodiment of the present invention.

FIG. 5 is a block diagram of an electrophotographic apparatus according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of an electrophotographic apparatus according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram of an electrophotographic apparatus according to a fifth embodiment of the present invention.

FIG. 8 is a schematic diagram showing a waveform of an AC voltage used in a fifth embodiment of the present invention.

[Explanation of symbols]

 23 Photoconductor 24 Magnet 25 Corona Charger 26 Grid Electrode 27 Laser Exposure 28 Developer Reservoir 29 Magnetic Developer 30 Electrode Roller 31 Magnet 32 AC High Voltage Power Supply 33 Scraper 35 Developer Flow Control Member

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G03G 15/06 101 G03G 15/06 101 15/09 101 15/09 101 21/00 350 21/00 350

Claims (1)

(57) [Claims] 1. An electrostatic latent image holder that includes a fixed magnet and moves, means for forming an electrostatic latent image on the electrostatic latent image holder, and the electrostatic latent image on which the electrostatic latent image is formed. A developer reservoir in which the magnetic one-component toner is attached to the entire surface of the image holding member by the fixed magnet and is supplied, and the surface of the electrostatic latent image holding member is provided with a predetermined gap. Move in the opposite direction of the electrostatic latent image carrier
The magnetic one-component toner in the non-image area on the electrostatic latent image carrier is
An electrode roller for removing, a means for applying a DC voltage superposed with an AC voltage to the electrode roller, a removing member for scraping off the magnetic one-component toner adhering to the electrode roller , and inside the developer reservoir, and The electrostatic latent image carrier and the above
Developer flow installed in the developer circulation part between the electrode roller
And a fixed member at a position substantially opposite to the electrode roller.
The closest position between the electrostatic image carrier and the electrode roller.
The electrophotographic device is characterized in that it is located on the upstream side .