JPH06161270A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To provide an electrophotographic method by which a structure is made simple and the soiling of toner in a device is prevented. CONSTITUTION:A photosensitive drum 38 which incorporates a fixed magnet is used. After an electrostatic latent image is formed, it is brought into contact with magnetic developer 44 in a developer container 43, and the developer 44 is attracted to the surface of the photosensitive body 38 by a magnetic force. Further, when an electrode roller 45 to which an AC voltage is applied is passed, the toner remains only in the image part and is developed and visualized. A voltage for developing the toner is applied when the electrified area of the electrostatic latent image carrier passes opposite the electrode roller 45. Thus, the formation of a solid image, which is caused immediately after the start of printing in reversal development, can be prevented.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A developing device to which the present invention is applied includes an electrostatic latent image holding member that moves by containing a fixed magnet, a developer reservoir, and an electrode roller installed with a gap between the electrostatic latent image holding member and the electrostatic latent image holding member. And a developing device. In this developing device, after the electrostatic latent image holding member is charged and exposed to form an electrostatic latent image, a magnetic developer is magnetically applied to the surface of the electrostatic latent image holding member located in the developer reservoir. The developer is attracted to adhere the developer, the developer is opposed to the electrode roller, an AC voltage is applied to the electrode roller, and the electrostatic latent image is reversely developed.

[0003]

Immediately after the operation of the developing device is started, the surface of the electrostatic latent image holding member in the developer reservoir is in a state of being in contact with the developer without being charged. When a developing bias voltage is applied to the electrode roller in this state, a large amount of toner adheres to the surface of the electrostatic latent image holding member, which not only wastes toner but also causes serious contamination in the apparatus.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an electrophotographic method capable of preventing solid toner adhesion immediately after the start of printing operation with a simple structure.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an electrostatic latent image holding member, a developer reservoir, and a gap between the electrostatic latent image holding member and a moving member that includes a fixed magnet. The electrostatic latent image holding member used in an electrophotographic apparatus having an electrode roller installed via the electrostatic latent image holding member is charged and exposed to form an electrostatic latent image, and then the electrostatic latent image is placed in the developer reservoir. A magnetic developer is magnetically attracted to the surface of the image carrier to adhere the developer, the developer is opposed to the electrode roller, and an electric field is formed between the electrode roller and the electrostatic latent image carrier. And a reversal development type electrophotographic method for developing an electrostatic latent image, characterized in that a voltage for developing the toner is applied when the electrostatic latent image carrier charging area passes through the electrode roller facing position. This is an electrophotographic method.

[0006]

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 points to the cascade development method, in which a non-rotating magnet is fixedly installed inside the electrostatic latent image holding member and an AC voltage is applied to the electrodes, thereby further reducing the size and improving the performance. . In the present invention, the development is almost completed when the toner is first sprinkled on the electrostatic latent image carrier. 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.

A developing device using the present invention will be described in detail with reference to FIG. FIG. 1 is an enlarged view of the developing unit shown in FIG. 2 described later. In FIG. 1, reference numeral 1 is an electrostatic latent image holder having an electrostatic latent image formed on its surface, 2 is a magnetic developer in a developer reservoir, and 3 is a non-rotating fixed member contained in the electrostatic latent image holder 1. Magnets, 4
Is a brush of the magnetic developer 2 formed by the magnet 3, and 5 is an electrode roller. The electrostatic latent image holder 1 on which the electrostatic latent image is formed conveys the developer 2 in the direction of the arrow A by magnetically attracting the magnetic developer 2 by the magnet 3, and at the same time, the developer ears 4 To form. The ears 4 of the developer not only form a stable developer layer between the electrostatic latent image holder 1 and the electrode roller 5, but also develop from the gap between the electrostatic latent image holder 1 and the electrode roller 5. It also prevents the agent from spilling down. The developer 2 electrostatically attracted to the electrode roller 5 is conveyed in the direction of arrow B by the rotational force of the electrode roller 5. As described above, according to the structure of the present invention, each constituent element can also serve several roles which have been conventionally divided, so that the structure of the developing machine can be simplified.

When such a developing device is used for reversal development, the surface of the electrostatic latent image carrier in the developer reservoir comes into contact with the developer without being charged immediately after the operation of the developing device is started. If a bias voltage is applied to the electrode roller in this state, a large amount of toner adheres to the surface of the electrostatic latent image holding member, resulting in waste of toner. Therefore, such a toner adhesion can be prevented by starting the application of the bias voltage applied to the electrode roller at least after the charged portion of the electrostatic latent image carrier starts passing in front of the electrode roller. it can.

The present invention uses an electrostatic latent image holder which contains 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. Thirty
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.

As the electrostatic latent image carrier used in the present invention, zinc oxide, selenium, cadmium sulfide, amorphous silicon, an organic photoconductor using phthalocyanine or an azo pigment, and the like 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 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 powder whose surface is coated with a resin, or fine powder such as ferrite powder or magnetite in a proportion of about 30 to 80%, a styrene resin or an epoxy resin. A magnetic powder obtained by dispersing and mixing with resin, styrene-acrylic resin, etc. and pulverizing and classifying is used. The average particle size of the carrier is preferably 300 μm or less, but particularly 150 μm or less allows the toner to 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 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. 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. An alternating 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 AC voltage is
Approximately 50H, depending on the image forming process speed
in the range z to 5000 Hz, preferably 300
To 3000 Hz is good. The value of AC voltage is ze
The value of the roto peak is preferably about 0.5 to 3 times the charging potential of the electrostatic latent image holding member, and further 0.5.
Therefore, a double value 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.

At the time of reversal development, when an AC voltage is applied to the electrode roller at the same time when the electrostatic latent image holding member starts to rotate, the surface of the electrostatic latent image holding member located inside the developer reservoir is not charged. A large amount of toner adheres as a solid image. Therefore, it is necessary to apply the voltage to the electrode roller when the area where the surface of the electrostatic latent image holding member is charged by the charger passes in front of the electrode roller.
As an improved method of this, the voltage applied to the electrode roller is set to an AC voltage in which a DC voltage is superposed, and the toner is not transferred when passing through an uncharged area (surface potential is almost 0 V) on the surface of the electrostatic latent image holding member. An AC voltage may be applied by superimposing a DC voltage that does not remain on the electrostatic latent image carrier, and an AC voltage may be applied by superimposing a DC voltage such that the toner is developed when passing through the charging area. Needless to say, the same effect can be obtained by applying a DC voltage having the same polarity as the toner to the electrostatic latent image holding member instead of applying the voltage to the electrode roller. At this time, it is sufficient to apply only the AC voltage to the electrode roller.

The developer attached to the electrode roller is scraped off by a scraper provided in the developer reservoir and returned to the developer reservoir again. This scraper is preferably electrically insulated so as not to affect the electrode roller. Therefore, for example, plastic such as polyester film is preferable for this scraper.
This scraper can be made of stainless steel or phosphor bronze plate, but at this time, in order to prevent it from electrically affecting the electrode roller, insulate it so that it does not come into electrical contact with anything other than the electrode roller. There is a need to.

[0019]

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

Specific Example 1 In FIG. 2, 1 is an organic photosensitive drum in which phthalocyanine is dispersed in a polyester binder resin, 2 is a magnetic two-component developer consisting of toner and carrier, and 3 is coaxial with the photosensitive body 1. A fixed, non-rotating magnet, 5 is photoconductor 1 and 5
A magnetic stainless steel electrode roller set with a gap of 00 μm, 6 is a corona charger for negatively charging the photoconductor, 7 is a grid electrode for controlling the charging potential of the photoconductor, 8 is signal light, and 9 is a developer. Reservoir 10 is an AC high-voltage power supply that applies a voltage to the electrode roller, 11 is a scraper made of polyester film that scrapes off the developer on the electrode roller, and 12 is a transfer corona charger that transfers the toner image on the photoconductor onto paper. is there. Magnetic flux density on the surface of photoconductor 1 is 800G
s. The photoconductor 1 has a diameter of 30 mm and a peripheral speed of 60 mm.
It was rotated at / s. Toner is styrene acrylic resin 93
% Of carbon black and 2% of oxycarboxylic acid metal complex, and 0.5% of colloidal silica was externally added (all in% by weight). As the carrier, ferrite powder having a particle size of 100 μm, the surface of which was coated with silicone resin, was used. The magnetic pole of the magnet 3 was set at an angle of 30 ° upstream from the closest position of the electrode roller 5.

The operation of the electrophotographic apparatus configured as described above will be described below with reference to FIG. Photoconductor 1
Was charged to -500V by a corona charger 6 (applied voltage-4kV, voltage of grid 7-500V). The photoconductor 1 was irradiated with laser light 8 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V. The magnetic developer 2 was attached to the surface of the photoconductor 1 in the developer reservoir 9 by magnetic force. Next, the photoconductor 1 was passed in front of the electrode roller 5. When passing through the uncharged area of the photoconductor 1, an AC high voltage power source 10 applied an AC voltage (frequency: 500 Hz) of 500 V 0-p (peak-to-peak 1 kV) without superimposing a DC voltage to the electrode roller 5. After that, -5
When the photoconductor 1 charged with 00V and having the electrostatic latent image written thereon is passed, the AC high voltage power source 10 causes the electrode roller 5 to
AC voltage of 500V0-p (peak-to-peak 1kV) superimposed with DC voltage of 350V (frequency 500H
z) was applied. Then, the developer moved between the photoconductor 1 and the electrode roller 5, and a negative-positive inverted toner image remained only on the image portion on the photoconductor 1. The developer adhered to the electrode roller 5 rotating in the direction of the arrow was scraped off by the scraper 11 and returned to the developer reservoir 9 to be used for the next image formation. The toner image thus obtained on the photoconductor 1 was transferred onto a sheet of paper (not shown) by the transfer charger 12, and then thermally fixed by a fixing device (not shown). As a result, a sharp image was obtained without any brush marks of the developer or toner scattering. Immediately after the start of printing, a solid black print portion did not occur on the photoconductor, and toner contamination inside the apparatus did not occur.

Concrete Example 2 Next, the apparatus shown in FIG. 2 was also used. This time, the insulating magnetic one-component toner was used as the toner. The composition of the magnetic one-component toner was 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 was externally added and used. %). If one-component toner is used, the spikes of the developer attached to the magnet become smaller, so the gap between the photoconductor 1 and the electrode roller 5 is set to 300 μm, and the magnetic pole of the magnet 3 is located upstream of the closest position of the electrode roller. The angle was set at 20 °. Corona charger 6 for photoconductor 1
(Applied voltage-4kV, voltage of grid 7-500V)
Then, it was charged to -500V. The photoconductor 1 was irradiated with laser light 8 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V. Toner 2 was magnetically adhered to the surface of the photoreceptor 1 in the developer reservoir 9. Next, the photoconductor 1 was passed in front of the electrode roller 5. When the photoconductor 1 passes through the uncharged area, the AC high voltage power source 10 applies a DC voltage of 500 V 0-p (peak-to-peak 1 kV) to the electrode roller 5 (frequency 50 kHz).
0 Hz) was applied. After that, when the photoconductor 1 charged with −500V and having an electrostatic latent image written thereon is passed, 500V0-p (peak-to-peak) in which a DC voltage of −350V is superposed on the electrode roller 5 by the AC high-voltage power source 10. 1
An alternating voltage (frequency: 500 Hz) of kV) was applied. Then, the toner moves between the photoconductor 1 and the electrode roller 5,
On the photoconductor 1, a negative-positive inverted toner image remained only in the image portion. The toner adhering to the electrode roller 5 rotating in the direction of the arrow was scraped off by the scraper 11 and returned to the developer reservoir 9 to be used for the next image formation. The toner image thus obtained on the photoconductor 1 was transferred onto a sheet of paper (not shown) by the transfer charger 12, and then thermally fixed by a fixing device (not shown). As a result, a sharp image was obtained without any brush marks of the developer or toner scattering. Immediately after the start of printing, a solid black print portion did not occur on the photoconductor, and toner contamination inside the apparatus did not occur.

Concrete Example 3 In FIG. 3, 13 is an organic photosensitive drum in which phthalocyanine is dispersed in a polyester binder resin, 14 is a magnet fixed coaxially with the photosensitive body 13, and 15 is a negatively charged photosensitive body. Corona charger, 16 is a grid electrode for controlling the charging potential of the photoconductor, 17 is signal light, 18 is a developer reservoir, 19 is a magnetic one-component developer, and 20 is a non-contact set with a gap with the photoconductor 13. A magnetic electrode roller, 21 is a fixed magnet installed inside the electrode roller 20, which does not rotate,
22 is an AC high-voltage power supply for applying a voltage to the electrode roller 40,
Reference numeral 23 is a scraper made of a polyester film that scrapes off the toner on the electrode roller, and reference numeral 24 is a transfer corona charger that transfers the toner image on the photoconductor onto paper. The magnetic flux density on the surface of the photoconductor 13 is 600 Gs. The magnetic flux density on the surface of the electrode roller 20 is 800 Gs. The photoconductor 13 has a diameter of 30 mm and is rotated at a peripheral speed of 60 mm / s.

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). When such a fine particle single-component toner is used, the ears of the developer adhering to the magnet are small and the transportability is extremely deteriorated. Therefore, the gap between the photoconductor 13 and the electrode roller 20 is set to 200 μm, and the photoconductor is also set. The magnetic force inside the electrode roller was made stronger than the magnetic force inside to improve the transportability.

The photosensitive member 13 is -50 at a corona charger 15 (applied voltage -4 kV, grid 16 voltage -500 V).
It was charged to 0V. The photoconductor 13 was irradiated with laser light 17 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V. The toner 19 was magnetically attached to the surface of the photoconductor 13 in the developer reservoir 18. Next, the photoconductor 13 was passed in front of the electrode roller 20. When passing through the uncharged region of the photoconductor 13, an AC high voltage power supply 22 applies a DC voltage of +100 V to a 500 V 0-p (peak to peak 1 kV) AC voltage (frequency 500 Hz) to the electrode roller 20. . After that, -5
When passing the photoconductor 13 charged to 00V and having an electrostatic latent image written therein, 500V 0-p in which a DC voltage of -350V is superimposed on the electrode roller 20 by an AC high voltage power source 22.
An AC voltage (frequency 500 Hz) of (peak-to-peak 1 kV) was applied. Then, the toner moved between the photoconductor 13 and the electrode roller 20, and a negative-positive inverted toner image remained only on the image portion on the photoconductor 13. The toner attached to the electrode roller 20 rotating in the direction of the arrow was scraped off by the scraper 23, returned to the developer reservoir 18 and used for the next image formation.

The toner image thus obtained on the photosensitive member 13 was transferred onto a sheet of paper (not shown) by the transfer charger 24, and then thermally fixed by a fixing device (not shown). As a result, there are no brush eyes of the developer and toner scattering.
An extremely high-resolution image in which an image line of book / mm was reproduced was obtained. Immediately after the start of printing, a solid black print portion did not occur on the photoconductor, and toner contamination inside the apparatus did not occur.

Concrete Example 4 In FIG. 4, 25 is an organic photoconductor drum in which phthalocyanine is dispersed in a polyester binder resin, 26 is a non-rotating magnet fixed coaxially with the photoconductor 25, and 27 is a negative photoconductor. A corona charger for charging, 28 a grid electrode for controlling the charging potential of the photoconductor, 29 a signal light, 30
Is a developer reservoir, 31 is a magnetic two-component developer, 32 is a developer amount regulating plate for regulating the amount of the developer 31 attached to the photoconductor 25, and 33 is a nonmagnetic electrode set with a gap from the photoconductor 25. A roller, 34 is a fixed magnet installed inside the electrode roller 33 that does not rotate, 35 is an AC high-voltage power supply that applies a voltage to the electrode roller 33, 36 is a scraper made of polyester film that scrapes off the developer on the electrode roller, Three
Reference numeral 7 is a transfer corona charger that transfers the toner image on the photoconductor to paper. Magnetic flux density on the surface of photoconductor 25 is 800 Gs
The magnetic flux density on the surface of the electrode roller 33 is 800 Gs. The magnetic pole of the magnet 26 is set at an angle of 20 ° upstream of the closest position of the electrode roller, and the magnetic pole of the magnet 34 on the photoconductor side is set at an angle of 20 ° below the closest position of the photoconductor 25. Was set. The diameter of the photoconductor 25 is 30 mm
Then, it was used by rotating at a peripheral speed of 60 mm / s. A toner having 93% of styrene-acrylic resin, 5% of carbon black and 2% of metal complex of oxycarboxylic acid, and 0.4% of colloidal silica externally added and having an average particle diameter of 5 μm was used (all are% by weight). As the carrier, ferrite powder having a particle size of 100 μm, the surface of which was coated with silicone resin, was used.

The operation of the electrophotographic apparatus configured as described above will be described below with reference to FIG. Photoconductor 2
5 is a corona charger 27 (applied voltage-4 kV, grid 2
And the voltage of 8 was -500V). The photoconductor 25 was irradiated with a laser beam 29 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -100V.
A magnetic two-component developer 31 was magnetically attached to the surface of the photoconductor 25 in the developer reservoir 30. Next, this developer was regulated to a thickness of 1 mm by the developer amount regulating plate 32, and then passed in front of the electrode roller 33 installed at a distance of 1 mm from the photoconductor 25. At this time, when the photoconductor 25 passes through the uncharged area, a DC voltage of +100 V is superimposed on the electrode roller 33 by the AC high voltage power source 500.
An AC voltage (frequency 500 Hz) of V0-p (peak-to-peak 1 kV) was applied. After that, -500V
When the photoconductor 25 charged with the electrostatic latent image and charged with the electrostatic latent image passes through, the AC high-voltage power supply 35 causes the electrode roller 33 to
500V0-p (peak
Two-peak 1kV AC voltage (frequency 500H)
z) was applied. Then, the developer violently moves back and forth and left and right between the photoconductor 25 and the electrode roller 33, and finally, a negative-positive inverted toner image remains only on the image portion on the photoconductor 25. The developer adhered to the electrode roller 33 rotating in the direction of the arrow was scraped off by the scraper 36, returned to the developer reservoir 30 and used for the next image formation. The toner image thus obtained on the photoconductor 25 is printed on paper (not shown).
After being transferred by the transfer charger 37, it was heat-fixed by a fixing device (not shown). As a result, an extremely high-resolution image was obtained in which brush lines of the developer and scattering of toner did not occur and an image line of 32 lines / mm was reproduced. Immediately after the start of printing, a solid black print portion did not occur on the photoconductor, and toner contamination inside the apparatus did not occur.

Specific Example 5 In FIG. 5, 38 is an organic photosensitive drum in which phthalocyanine is dispersed in a polyester binder resin, 39 is a fixed magnet which is coaxial with the photosensitive member 38 and does not rotate, and 40 is a negative member of the photosensitive member. , 41 is a grid electrode for controlling the charging potential of the photoconductor, 42 is signal light, 4
3 is a developer reservoir, 44 is a magnetic one-component developer, 45 is a non-magnetic electrode roller set by opening a gap with the photoconductor 38,
Reference numeral 46 is a fixed magnet installed inside the electrode roller 45, which does not rotate, 47 is an AC high-voltage power supply for applying a voltage to the electrode roller 45, 48 is a scraper made of polyester film for scraping the developer on the electrode roller, and 49 is It is a transfer corona charger that transfers the toner image on the photoconductor to paper. Fifty
Is a damper for smoothing the flow of the developer in the developer reservoir and 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 38 is 600 Gs.
The magnetic flux density on the surface of the electrode roller 45 is 800 Gs.
The magnetic force inside the electrode roller is stronger than the magnetic force inside the photoconductor to improve the transportability. The magnetic pole angle θ of the magnet 39 shown in the figure was set to 15 °. The diameter of the photoconductor 38 is 30 m
It was used by rotating in the direction of the arrow in the figure at m and a peripheral speed of 60 mm / s. The diameter of the electrode roller 45 is 16 mm and the peripheral speed is 40 m.
The photoconductor was rotated at a speed of m / s in the direction opposite to the traveling direction (the direction of the arrow in the figure). The gap between the photoconductor 38 and the electrode roller 45 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 photoconductor 38 is charged with a corona charger 40 (applied voltage −4.5 kV, grid 41 voltage −500 V).
It was charged to 500V. A laser beam 42 is applied to the photoconductor 38.
Was irradiated to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -90V. Toner 44 was magnetically attached to the surface of the photoconductor 38 in the developer reservoir 43. Next, the photoconductor 38 was passed in front of the electrode roller 45. When the photoconductor 38 passes through the uncharged area, a DC voltage of 0 V is superposed on the electrode roller 45 by an 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 38 charged to 0V and having the electrostatic latent image written therein, an AC high voltage power supply 47 is applied to the electrode roller 45,
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 38 is collected by the electrode roller 45,
A negative-positive inverted toner image remained only on the image portion on the upper portion. The toner attached to the electrode roller 45 rotating in the direction of the arrow was scraped off by the scraper 48, returned to the developer reservoir 43, and used for the next image formation. The state of toner circulation in the developer reservoir 43 is indicated by a dashed arrow. The toner image thus obtained on the photoconductor 38 is formed on paper (not shown).
After transfer by the transfer charger 49, 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. Immediately after the start of printing, a solid black print portion did not occur on the photoconductor, and toner contamination inside the apparatus did not occur.

[0032]

According to the present invention, it is possible to obtain an electrophotographic apparatus having a simple structure, a small size, a long life, and no toner contamination in the apparatus.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a developing device used in the present invention.

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

FIG. 3 is a configuration diagram of an electrophotographic apparatus according to a third embodiment of the present invention.

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

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

[Explanation of symbols]

 1, 13, 25, 38 Photoreceptor 3, 14, 21, 26, 34, 39, 46 Magnet 6, 15, 27, 40 Corona charger 9, 18, 30, 43 Developer reservoir 2, 19, 31, 44 Magnetic developer 5, 20, 33, 45 Electrode roller 10, 22, 35, 47 AC high voltage power supply 11, 23, 36, 48 Scraper

Claims (2)

[Claims] 1. An electrophotographic apparatus having an electrostatic latent image holding member which moves with a fixed magnet contained therein, a developer reservoir, and an electrode roller provided with a gap between the electrostatic latent image holding member, and After the electrostatic latent image holder is charged and exposed to form an electrostatic latent image, a magnetic developer is magnetically attracted to the surface of the electrostatic latent image holder located in the developer reservoir to magnetically attract the developer. And the developer is opposed to the electrode roller, and an electric field is formed between the electrode roller and the electrostatic latent image holder to develop the electrostatic latent image. hand,
An electrophotographic method, characterized in that the voltage for developing the toner is applied when the electrostatic latent image carrier is passing through the charging area of the electrode roller facing position. 2. An electric field formed between the electrode roller and the electrostatic latent image carrier is an alternating electric field in which a DC electric field is superposed, and the electrostatic latent image is generated when passing through an uncharged area of the electrostatic latent image carrier. An alternating electric field is formed by superimposing a DC electric field that does not develop the carrier, and when passing through the electrostatic latent image carrier charging area, an alternating electric field is formed by superimposing a DC electric field suitable for developing the electrostatic latent image. The electrophotographic method according to claim 1, wherein: