JP2517206B2 - 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 Conventionally, a two-component developing method using a magnetic developer has been widely used in an electrophotographic method. Various methods have been proposed to date as the developing method, but the magnetic brush developing method developed in 1953 has the advantage that the apparatus can be made more compact and the fine line reproducibility is improved compared to the conventional cascade developing method. Because it ’s relatively good,
It has become the mainstream of the electrophotographic development method for copying documents.

An example of the conventional two-component developing method described above will be described below with reference to the drawings. FIG. 1 shows an electrophotographic apparatus using a conventional two-component developing method. In FIG. 1, reference numeral 1 is a two-component developer in which toner and carrier are mixed. A developing roller 2 includes a magnet roller 3 inside. 4 is an electrophotographic photoreceptor, 5 is a corona charger that charges the electrophotographic photoreceptor, 6 is exposure light that exposes a signal, 7 is a corona charger that transfers a toner image onto paper,
A cleaning device 8 cleans the toner remaining on the photoconductor. The operation of the electrophotographic apparatus configured as described above will be described below. First, the photoconductor 4
Is charged by the charger 5. After exposure with the signal light 6, an electrostatic latent image is formed and developed by the two-component magnetic brush developer 1 carried on the developing roller 2. The toner image thus obtained on the photoconductor 4 is transferred onto the paper by using the transfer charger 7. The toner remaining on the photoconductor is cleaned by the cleaning device 8
And use again for the next imaging step.

Other conventional electrophotographic developing methods include a cascade developing method, a touchdown developing method and a jumping developing method.

Among them, the cascade developing method disclosed in US Pat. No. 3,105,770 is known as a developing method in which a developer is directly sprinkled on the photoreceptor. The cascade developing method is the first developing method used in an electrophotographic copying machine.

A touch-down developing method disclosed in US Pat. No. 3,866,574 is known as a method for flying and developing one-component toner. An AC bias is applied to the developing roller. In the present invention, it is described that the AC bias applied to the developing roller activates the movement of the toner, and the toner reaches the flying portion in the image portion and returns to the developing roller midway 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. 58-32375. This jumping developing method is a developing method in which a toner layer is carried on a toner carrier and is carried to a developing unit, and an AC bias is applied to the toner carrier to adhere the toner to the image area of the photoconductor. This Japanese Patent Publication No. 58-32375 differs from the above-mentioned U.S. Pat. No. 3,866,574 in technical idea in that the toner reciprocally moves electrostatically in the image portion and the non-image portion.

A technique similar to the Japanese Patent Publication No. 58-32375 is disclosed in Japanese Examined Patent Publication No. 30136. this is,
The charged toner is once electrostatically attached to the entire surface of the photoconductor from the toner carrier, and then an AC voltage is applied to a separately provided non-contact electrode roller to collect unnecessary toner.
This patent differs from the above-mentioned Japanese Patent Publication No. 58-32375 in that there is a step of electrostatically transferring the initially charged toner from the toner carrier to the photoreceptor.

[0009]

However, the magnetic brush developing method has a problem in that the structure of the developing device is large and the apparatus becomes large and complicated. In addition, there is a problem that the image quality is poor because the contact time between the photosensitive member and the developer is short.

Furthermore, the cascade development method is not good at reproducing solid images. Further, there is a problem in that the structure is large and the device becomes large and complicated.

Further, the developing device disclosed in US Pat. No. 3,866,574 has the drawback that the device is required to have high accuracy and is complicated and costly.

Further, since the jumping developing method has a structure in which only the image portion of the photoconductor is developed by the toner carrier carrying the toner layer, the history of the previous image remains in the toner layer on the toner carrier and the developed image is obtained. The so-called sleeve ghost phenomenon, in which afterimages appear on the screen, was a drawback. In addition, the device is complicated and the cost is high.

In the last Japanese Patent Publication No. 3-30136, a sleeve ghost does not appear because an electrode roller is separately provided, but it has a drawback that the device is complicated and the cost is high because there are two rollers.

An object of the present invention is to obtain an electrophotographic apparatus having a simple structure and high image quality.

[0015]

In order to solve the above problems, the present invention includes an electrostatic latent image holding member that contains a fixed magnet and holds and moves an electrostatic latent image, and at least toner. A developer reservoir that holds a magnetic developer inside and magnetically attaches the magnetic developer to the surface of the electrostatic latent image holding member located inside the developer reservoir by the magnetic force of the fixed magnet; A developer amount regulating plate for uniformly regulating the layer thickness of the magnetic developer attached to the surface of the electrostatic latent image carrier, and the electrostatic latent image carrier carrying the magnetic developer layer on the surface,
Further, an electrode roller which encloses and rotates a fixed magnet and collects the magnetic developer, and an alternating voltage for removing the toner in the non-image area and leaving the toner in the image area on the electrostatic latent image carrier are applied to the electrode roller. The electrophotographic apparatus has a high-voltage power supply to be applied and a scraper for scraping the magnetic developer collected on the electrode roller.

[0016]

According to the present invention, a photosensitive member having a fixed magnet inside is used, and a developer is sprinkled and magnetically adhered to an electrostatic latent image holding member on which an electrostatic latent image is formed. After the thickness is made uniform, it is carried and conveyed to the electrode roller part which has a magnet inside, AC bias is applied to the electrode roller, and unnecessary developer in the non-image part of the photoconductor is removed by the combined force of electrostatic force and magnetic force. Is. That is, the present invention, in the conventional electrophotographic developing method, a magnet for adsorbing the developer is installed inside the photoreceptor,
The size and performance of the photoconductor are improved by adding an AC voltage to the electrode roller provided outside the photoconductor. As a result, the developing device can be simplified, and the developing area of the developer that comes into contact with the photoconductor can be widened, and high image quality can be obtained. In the present invention, when the developer is first sprinkled on the photoconductor, the development is almost completed, and the electrode roller part circulates the developer in the developer reservoir and at the same time, the non-image part of the photoconductor electrostatic latent image. The developer of is collected.

The difference in structure between the electrode roller of the present invention and the developing roller used in the conventional developing method will be described. (1) In the present invention, it is the photoreceptor containing a magnet that carries and carries the developer from the developer reservoir to the developing section, and the concept of the conventional electrostatic latent image carrier and the developer carrier is the same. It is an embodiment. Since the configuration is based on this technical idea, the image forming method has a difference that it is a method of peeling off the unnecessary developer in the non-image area, rather than attaching and developing the developer to the image area. (2) The electrode roller of the present invention has a structure in which the bare surface always faces the photoconductor, and the developer collected by the electrode roller is immediately removed from the developing section by the rotation of the roller. In the conventional method of developing the image portion with the thin developer layer formed on the developing roller, the uniformity of the thin developer layer on the developing roller appears in the image as it is, which is high in forming the developer layer. Precision is required. However, as in the present invention, when a developer layer having an excessive thickness is first formed on the photoconductor and then the developer is collected by a bare electrode roller, most of the non-uniform portion of the developer layer is formed. Moves to the side of the electrode roller, and becomes flat on the photoconductor so that a uniform image can be left.

According to the present invention, since the magnet is provided in the inner space of the photosensitive member and the conveying movement of the developer can be used also as the moving force of the photosensitive member, the construction of the developing device can be simplified, and further, the electrode roller Since the developer is collected on the bare surface, sleeve ghost does not occur.

[0019]

EXAMPLE A toner for a so-called two-component developer can be used in the present invention. This is one in which a coloring pigment such as carbon black or phthalocyanine is dispersed in a binder resin such as styrene resin or acrylic resin, pulverized and classified. The toner may be a powder obtained by spray drying or a powder chemically obtained by a pearl polymerization method or the like. In this case, if silica fine particles are adhered to the surface of the toner, the fluidity of the toner is improved, and as a result, the fog is effectively eliminated. The toner particles may be mixed as they are with the carrier, or depending on the use conditions, fine particles of fluororesin, fine plastic powder, zinc stearate or the like may be adhered to the surface of the toner. The average particle diameter of the toner used is preferably 15 μm or less, but when it is 12 μm or less, a sharper image can be obtained.

The carrier used in the two-component developer of the present invention is a magnetic substance such as iron powder or ferrite powder, or those whose surface is coated with a resin, and fine powder such as ferrite powder or magnetite in an amount of about 30 to 80%. A magnetic powder or the like, which is pulverized and classified by being dispersed and mixed in a styrene resin, an epoxy resin, a styrene acrylic resin or the like, is used. The average particle size of the carrier is preferably 300 μm or less, but particularly 150
If it is less than μm, the toner can be uniformly charged.

An insulating one-component toner can be used as the magnetic developer of the present invention. 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. The toner may be a powder obtained by spray drying or a powder chemically obtained by a pearl polymerization method or the like. In this developing method, the toner is once attached to the entire surface of the photoconductor, and then the toner in the non-image area is removed by the electrode roller. However, in this method, if the toner has poor fluidity, the toner in the non-image area is removed. Adheres strongly to the photoconductor and cannot be removed, resulting in background fog and degrading the image. When silica fine particles are externally added to the surface of the toner, the fluidity of the toner is improved, the non-electrostatic adhesion force to the photoconductor is reduced, and the fog is eliminated. At this time, the silica particles contribute not only to improving the fluidity but also to charging the toner. In this developing method, in the case of a one-component toner, it is not necessary to particularly provide a charging member for charging the toner, and if silica particles are added to the toner, when the toner comes in contact with the charged photoreceptor, the charge is transferred from the photoreceptor side to the toner side. It was found that the toner was charged to the same polarity as the photoconductor. The silica fine particles are also called colloidal silica.

The photoreceptor used in the present invention includes zinc oxide,
An organic photoreceptor using selenium, cadmium sulfide, phthalocyanine or an azo pigment can be used. The present invention
An electrophotographic photosensitive drum containing a magnet is used. This magnet does not rotate but only the photoconductor rotates.

In the present invention, a developer reservoir having an opening on the surface of the photoreceptor is used. The developer is configured to directly contact the photoconductor from the developer reservoir.

When the photoconductor having such a structure passes through the inside of the developer reservoir, the developer adheres to the photoconductor due to the magnetic force and moves with the movement of the photoconductor. At this time, when the developer is a one-component toner, the developer remains attached to the photoconductor due to electrostatic attraction and so-called van der Waals force even if the developer leaves the magnetic field.

The amount of the developer attached to the surface of the photoconductor is
It is regulated by the developer amount regulating plate. For this developer amount regulating plate, an elastic body such as a rubber plate can be used. At this time, if a urethane or silicone rubber plate is softly brought into direct contact with the surface of the photoreceptor, a uniform thin layer of developer is formed on the surface of the photoreceptor. In addition, soft iron, nickel, magnetic stainless steel (SUS43
A magnetic substance such as 0) may be used. At this time, if the developer amount regulating plate is installed at a position facing the one magnetic pole contained in the photoconductor with a distance, the developer flowing out is partially obstructed by the magnetic force connecting the two magnetic poles. It becomes possible to form a different developer layer on the photoreceptor. Further, when the developer amount regulating plate is used as a conductor and a DC voltage is applied, the developer layer can be formed more easily. For example, when a DC voltage that is approximately the same as or higher than the surface potential of the photoconductor is applied, the developer is pushed from the developer amount regulating plate toward the photoconductor, and a uniform dense developer thin layer is formed. The distance between the developer amount regulating plate of the magnetic material and the surface of the photoconductor is preferably 100 μm to 4 mm. The thin developer layer thus formed has a thickness of 10
From 0 μm to about 4 mm, especially in the case of one-component toner, a sharp line image was obtained when the developer layer thickness was set to about 50 μm.

The electrode roller is a photoreceptor and 100 μm to 4 m.
It will be installed at a distance of m. If this distance is set wider than the thickness of the developer layer formed on the photoconductor, a sharp line image can be obtained. On the other hand, in order to obtain a higher solid image density, the distance between the photoconductor and the electrode roller may be set smaller than the thickness of the developer layer. That is, at this time, the tip of the developer layer on the photoconductor contacts the electrode roller. The material of the electrode roller may be any material as long as it is conductive, and examples thereof include stainless steel and aluminum. The surface of the developer electrode roller may be polished, or may be provided with irregularities by sandblasting or the like. Further, a conductive resin having graphite or the like dispersed in enamel may be coated on the conductive support. Such selection is determined in consideration of the fluidity of the developer used. In order to efficiently collect the developer on the photoconductor, a magnet is placed inside the electrode roller. This makes it possible to efficiently remove not only the electrostatic force but also the magnetic force to remove the developer on the photoconductor, which is efficient.

An alternating voltage is applied to this electrode roller. The frequency of this AC voltage is approximately 50 Hz to 5000 Hz, although it varies depending on the image forming process speed.
, Preferably from 300 to 3000 Hz. The value of the AC voltage is a zero-to-peak value, which is preferably about 0.5 to 3 times, and more preferably 0.5 to 1.5 times the charging potential of the photoconductor. If the value of the DC voltage superimposed on the AC voltage is set to be equal to or less than several tens of percent lower than the charging potential of the photoconductor, a good negative-positive reversal image can be obtained. Needless to say, in the case of regular development, it is sufficient to apply a voltage substantially equal to the exposure potential of the photoconductor using a toner of opposite polarity. When such a voltage is applied to the electrode roller, the developer attached to the surface of the photoconductor moves between the photoconductor and the electrode roller, and gradually the developer in the non-image area of the photoconductor moves to the electrode roller side. , The developer image remains only in the image area. The outer peripheral movement direction of this electrode roller is preferably the same as the outer peripheral movement direction of the photoconductor,
Moreover, when the moving speeds were made substantially the same, the edge effect peculiar to electrophotography did not appear, and uniform solid part development was obtained. However, conversely, when the edge is emphasized in order to improve the character reproduction, the reverse rotation may be performed.

The developer adhering to the electrode roller may be scraped off by a scraper provided in the developer reservoir, and the developer may be returned to the developer reservoir again or may be discharged to the outside of the developing device as it is. good. This scraper is preferably electrically insulated so as not to affect the electrode roller. Therefore, plastic such as polyester film is preferable for this scraper. This scraper can be made of stainless steel or phosphor bronze plate, but at that time, make sure that it does not come into electrical contact with anything other than the electrode roller so as not to electrically affect the electrode roller. Needs to be insulated.

(Specific Embodiment 1) An electrophotographic developing apparatus of the present invention will be described below with reference to the drawings.

In FIG. 2, 9 is an organic photosensitive drum in which phthalocyanine is dispersed in a binder resin, and 10 is a photosensitive member 9.
, A magnet composed of four magnetic poles fixed coaxially, 11 is a corona charger for negatively charging the photoconductor, 12 is a grid electrode for controlling the charging potential of the photoconductor, 13 is signal light, 1
4 is a developer reservoir, 15 is a negatively chargeable magnetic one-component toner having an average particle diameter of about 10 μm, 16 is a developer amount control plate made of stainless steel, 17 is an electrode roller made of aluminum, and 18 is fixed coaxially with the electrode roller 17. A non-rotating magnet composed of four magnetic poles, 19 is an AC high-voltage power source for applying an AC voltage to the electrode roller, 20 is a scraper made of polyester film for scraping off the developer on the electrode roller 17, and 21 is on the photoconductor. A transfer corona charger that transfers a toner image onto paper. The magnetic flux density on the surface of the photoconductor 9 and the surface of the electrode roller 17 is 800 Gs. The diameter of the photoconductor 9 is 30 mm
Then, it was rotated at a peripheral speed of 30 mm / s.

The photoconductor 9 is charged with a corona charger 11 (applied voltage-
4kV, voltage of grid 12 -500V), -500
It was charged to V. The photoconductor 9 was irradiated with laser light 13 to form an electrostatic latent image. In the developer reservoir 14, the magnetic one-component toner 15 is magnetically adhered onto the surface of the photoconductor 9 and further passed through the developer amount regulating plate 16 to which a voltage of −500 V is applied. Thickness about 150 μm
Toner layer was formed. At this time, the toner is
It was charged to 3 μC / g. Next, the photoconductor 9 having the toner layer attached thereto was passed in front of the electrode roller 17. At this time, the distance between the photoconductor 9 and the electrode roller 17 was set to 200 μm. The electrode roller 17 has a voltage of -450 due to the high voltage power supply 19.
An AC voltage (frequency: 1 kHz) of 700 V0-p superposed with a DC voltage of V was applied. The toner layer on the photoconductor 9 moves between the photoconductor 9 and the electrode roller 17, and the toner in the non-image area gradually moves to the electrode roller 17 side, and the toner image on the photoconductor 9 is negative-positive inverted only in the image area. Remained. The toner adhering to the electrode roller 17 was adhered to the electrode roller 17 by the internal magnet 18 and conveyed, scraped off by the scraper 20, returned to the developer reservoir 14 and used for the next image formation. The toner image thus obtained on the photoconductor 9 was transferred onto paper (not shown) by the transfer charger 21, and then heat-fixed by a fixing device (not shown). on the other hand,
After the transfer, the photoreceptor 9 was charged again by the corona charger 11 and used in the next image forming step. As a result, a sharp image with no toner scattering was obtained.

(Specific Example 2) In FIG. 3, 22 is an organic photosensitive drum in which an azo pigment is dispersed in a binder resin.
Reference numeral 23 denotes a non-rotating magnet composed of four magnetic poles fixed coaxially with the photoconductor 22, 24 a corona charger for negatively charging the photoconductor, 25 a grid electrode for controlling the charging potential of the photoconductor, and 26 a signal. Light, 27 is a developer reservoir, 28 is an iron powder carrier 29 having a particle size of 100 μm whose surface is coated with a silicone resin, and a toner 30 colored with carbon black.
Is a two-component developer, 31 is a stainless steel developer amount regulating plate installed with a distance of 1 mm from the photoconductor 22, 32
Is an aluminum electrode roller installed at a distance of 1 mm from the photoconductor 22, 33 is a non-rotating magnet composed of three magnetic poles fixed coaxially with the electrode roller 32, and 34 is a voltage applied to the electrode roller. AC high-voltage power supply, 35 is a scraper made of polyester film for scraping off the developer on the electrode roller, 36 is a drain for discharging the used developer, 37 is a transfer corona charger for transferring the toner image on the photoconductor onto paper Is. Surface of photoconductor 22 and electrode roller 32
The magnetic flux density on the surface is 800 Gs. The photoconductor 22 has a diameter of 30 mm and is rotated at a peripheral speed of 30 mm / s.

The photosensitive member 22 is -50 at a corona charger 24 (applied voltage -4 kV, grid 25 voltage -500 V).
It was charged to 0V. The photoconductor 22 was irradiated with laser light 26 to form an electrostatic latent image. In the developer reservoir 27, when a two-component magnetic developer 28 having a toner concentration of 10% is magnetically attached to the surface of the photoconductor 22 and passed through the developer amount regulating plate 31, the thickness of the photoconductor 22 is increased. A developer layer of about 1.2 mm was formed. Next, the photoconductor 22 to which the developer layer is attached
Was passed in front of the electrode roller 32. To the electrode roller 32, a high voltage power source 34 applied an AC voltage of 700 V0-p (frequency 1 kHz) on which a DC voltage of -450 V was superimposed. The developer layer on the photoconductor 22 moves between the photoconductor 22 and the electrode roller 32, a negative-positive inverted toner image remains only on the image portion on the photoconductor 22, and other developers are placed on the electrode roller 32 side. I moved. The developer attached on the electrode roller 32 was attached to the electrode roller 32 by an internal magnet 33 and conveyed, scraped off by a scraper 35, and discharged to a drain 36. The toner image thus obtained on the photoconductor 22 was transferred onto a sheet of paper (not shown) by the transfer charger 37, and then thermally fixed by a fixing device (not shown). As a result, a sharp image with no toner scattering was obtained.

[0034]

As described above, according to the present invention, after the electrostatic latent image is formed on the electrostatic latent image holder containing the fixed magnet, the magnetic developer is magnetically applied on the surface of the electrostatic latent image holder. Since the magnetic developer in the non-image portion is adhered and then the magnetic developer in the non-image portion is removed by the electrode roller having the fixed magnet inside, it is possible to obtain an electrophotographic apparatus having a simple constitution and high image quality.

[Brief description of drawings]

FIG. 1 is a schematic view of a conventional electrophotographic developing device.

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

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

[Explanation of symbols]

 9 Photoconductor 10 Magnet 11 Corona Charger 12 Grid Electrode 13 Laser Exposure 14 Developer Reservoir 15 Magnetic Developer 17 Electrode Roller 18 Magnet 19 AC High Voltage Power Supply 20 Scraper

Claims (1)

(57) [Claims] 1. An electrostatic latent image holder that contains a fixed magnet and that holds and moves an electrostatic latent image, and a surface of the electrostatic latent image holder.
The magnetic developer containing at least a toner is held inside, and the magnetic developer is magnetically attracted to the surface of the electrostatic latent image holding member located inside the developer reservoir by the magnetic force of the fixed magnet. A developer reservoir to be attached, a developer amount regulating plate for uniformly regulating the layer thickness of the magnetic developer attached to the surface of the electrostatic latent image holding member, and the electrostatic carrying the magnetic developer layer on the surface. An electrode roller that faces the latent image carrier and rotates with a fixed magnet contained therein to collect the magnetic developer, and a toner in the non-image area on the electrostatic latent image carrier is removed to remove the toner in the image area. An electrophotographic apparatus, comprising: a high-voltage power source for applying an alternating voltage, which is a superposed direct current voltage to the electrode roller, to the electrode roller; and a scraper for scraping the magnetic developer collected on the electrode roller.