JP2517204B2 - 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 provides an electrostatic latent image holding member containing a fixed magnet, and a magnetic developer containing at least a toner, the electrostatic latent image holding member. A developer reservoir for magnetically attracting and adhering to the surface of the body by the magnetic force of the fixed magnet, a developer amount regulating plate for forming a developer layer on the electrostatic latent image carrier, and a thickness of the developer layer. And an electrode roller to which an AC voltage is applied, which is installed with a narrower gap and collects toner in the non-image portion of the electrostatic latent image holding member and leaves a toner image.

[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, and then carried and conveyed to an electrode roller portion.
An AC bias is applied to the electrode roller, and the unnecessary developer in the non-image portion of the photoconductor is removed by electrostatic force. That is, the present invention is a conventional electrophotographic development method, in which a magnet for adsorbing a developer is installed inside the photoconductor, and a voltage is applied to an electrode provided outside the photoconductor to further reduce the size.
It is a high-performance product. 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.

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.

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.

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 and the photosensitive member are 100 μm to 4 m.
It will be installed at a distance of m. In order to obtain a higher solid image density, the distance between the photoconductor and the electrode roller is 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 developer electrode roller may be any material as long as it is electrically 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, it is effective to put a magnet inside the electrode roller. An alternating voltage is applied to this electrode roller. The frequency of this AC voltage is
Depending on the process speed of image formation, it is approximately 5
A range of 0 Hz to 5000 Hz, preferably a range of 300 to 3000 Hz is good. The AC voltage value is a zero-to-peak value, which is approximately 0.5 of the charging potential of the photoconductor.
Values of 3 to 3 are preferable, and values of 0.5 to 1.5 are more preferable. 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, a developer having a reverse polarity may be used to apply a voltage substantially equal to the exposure potential of the photoconductor. 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 moving direction of the electrode roller is preferably the same as the outer peripheral moving direction of the photoconductor, and when the moving speeds are substantially the same, the edge effect peculiar to electrophotography does not appear and uniform solid development is 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, for example, plastic such as polyester film is preferable for this scraper. This scraper may be made of stainless steel or phosphor bronze plate, but at that time, it is not electrically contacted with anything other than the developer electrode roller so as not to electrically affect the electrode roller. So it needs to be insulated.

(Specific Example 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 polyester binder resin,
Reference numeral 10 is a non-rotating magnet composed of four magnetic poles fixed coaxially with the photoconductor 9, 11 is a corona charger for negatively charging the photoconductor, 12 is a grid electrode for controlling the charging potential of the photoconductor, and 13 is a signal. Light, 14 is a developer reservoir, 15 is a negative charging magnetic one-component toner having an average particle size of about 10 μm, 1
6 is a non-magnetic stainless steel developer amount control plate, 17 is an aluminum electrode roller, 18 is an AC high-voltage power supply for applying a voltage to the electrode roller, and 19 is polyester that scrapes off toner on the electrode roller 17. A film scraper 20 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 9 is 1000 Gs. The diameter of the photoconductor 9 is 30 mm,
It was rotated at a peripheral speed of 30 mm / s. The composition of the magnetic one-component toner used is 61% polyester resin and 37 magnetite.
%, And 2% of oxycarboxylic acid metal complex, and 1.0% of colloidal silica was externally added and used (all are% by weight).

The photosensitive member 9 is connected to the 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. At this time, the exposure potential of the photoconductor 9 is −
It was 100V. Magnetic one-component toner 15 is attached to the surface of the photoconductor 9 in the developer reservoir 14 by magnetic force,
Further, by applying a voltage of -500 V, the surface of the photosensitive member 9 and
After passing through the developer amount regulating plate 16 installed with a distance of 0 μm, a toner layer having a thickness of about 200 μm was formed on the photoconductor 9. At this time, the toner was charged to approximately −5 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 electrode roller 17 and the photoconductor 9 was set to 150 μm. The electrode roller 17 is supplied with a high-voltage power supply 18 and a DC voltage of -400 V is superimposed on it to 450 V 0-p (peak-to-peak 9
An AC voltage (frequency: 600 Hz) of 00 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 only the image area on the photoconductor 9 has a negative-positive inverted toner image. The remaining. The toner adhering to the electrode roller 17 was scraped off by the scraper 19 and returned to the developer reservoir 14 to be used for the next image formation. The toner image thus obtained on the photoconductor 9 was transferred onto a sheet of paper (not shown) by the transfer charger 20, and then thermally 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 dark image having a reflection density of 1.7 in the solid image portion was obtained.

(Specific Example 2) In FIG. 3, reference numeral 21 denotes an organic photosensitive drum having an azo pigment dispersed in a binder resin.
Reference numeral 22 is a non-rotating magnet composed of four magnetic poles fixed coaxially with the photoconductor 21, 23 is a corona charger for negatively charging the photoconductor, 24 is a grid electrode for controlling the charging potential of the photoconductor, and 25 is a signal. Light, 26 is a developer reservoir, 27 is an iron powder carrier 28 having a particle size of 100 μm, the surface of which is coated with a silicone resin, and a toner 29 colored with carbon black.
Is a two-component developer, 30 is a developer amount control plate made of stainless steel, which is installed with a distance of 1 mm from the photoconductor 21, 31
Is an aluminum electrode roller installed at a distance of 1 mm from the photoconductor 21, 32 is a non-rotating magnet composed of three poles fixed coaxially with the electrode roller 31, and 33 is a voltage applied to the electrode roller. AC high-voltage power supply, 34 is a scraper made of polyester film that scrapes off the developer on the electrode roller, 35 is a drain that discharges the used developer, and 36 is a transfer corona charger that transfers the toner image on the photoconductor onto paper. Is. Surface of photoconductor 21 and electrode roller 31
The magnetic flux density on the surface is 800 Gs. The diameter of the photoconductor 21 was 30 mm, and the photoconductor 21 was rotated at a peripheral speed of 30 mm / s.

The photosensitive member 21 is -50 at a corona charger 23 (applied voltage -4 kV, grid 24 voltage -500 V).
It was charged to 0V. The photoconductor 21 was irradiated with a laser beam 25 to form an electrostatic latent image. In the developer reservoir 26, a two-component magnetic developer 27 having a toner concentration of 10% is magnetically attached onto the surface of the photoconductor 21 and passes through the developer amount regulating plate 30. A developer layer of about 1.2 mm was formed. Next, the photoconductor 21 to which the developer layer is attached
Was passed in front of the electrode roller 31. A high-voltage power supply 33 applied to the electrode roller 31 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 21 moves between the photoconductor 21 and the electrode roller 31, a negative-positive inverted toner image remains only on the image portion on the photoconductor 21, and other developers are placed on the electrode roller 31 side. I moved. The developer adhering to the electrode roller 31 was adhered to the electrode roller 31 by the internal magnet 32 and conveyed, scraped off by the scraper 34 and discharged to the drain 35. The toner image thus obtained on the photoconductor 21 was transferred onto a sheet of paper (not shown) by the transfer charger 36 and then thermally fixed by a fixing device (not shown). As a result, a sharp image with no toner scattering was obtained.

[0032]

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. After the adhesion, the developer layer thickness regulating plate regulates the developer layer, and the magnetic roller in the non-image area is removed by the electrode roller arranged with a narrower gap than the developer layer. A simple and high quality electrophotographic device can be obtained.

[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 16 Developer Layer Control Plate 17 Electrode Roller 18 AC High Voltage Power Supply 19 Scraper

Claims (1)

(57) [Claims] 1. An electrostatic latent image holder containing a fixed magnet,
A developer reservoir that magnetically attracts and attaches a magnetic developer containing at least toner to the surface of the electrostatic latent image holding member by the magnetic force of the fixed magnet, and a developer layer on the electrostatic latent image holding member. a developer amount regulating plate forming the disposed with a narrow gap than the thickness of the developer layer, straight as to leave a toner image by collecting the toner of the non-image portion of the electrostatic latent image holding member
An electrophotographic apparatus, comprising: the electrode roller to which an alternating voltage with a flowing voltage is applied.