JP2001166572A - Non-magnetic one-component developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device and an image forming device capable of always obtaining stable image density by efficiently supplying toner without giving stress to the toner in the case of supplying the toner to a developing roller. SOLUTION: This non-magnetic one-component developing device is equipped with a brush type toner supply roller 14 and the 2nd developing roller 12. In the developing device an electrostatic latent image on a photoreceptor 1 separated from the roller 12 is developed with the toner carried on the roller 12 by fine closed electric field by applying DC developing bias, and the roller 12 is provided separately from the roller 14, and the bias obtained by superimposing a DC component on an AC component is applied between the rollers 12 and 14. Then, the image forming device is equipped with the developing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developing apparatus and an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, to a developing apparatus in which a plurality of developing apparatuses overlap and develop on a photosensitive member. At least one of them is a non-magnetic one-component developing device and relates to an image forming apparatus provided with such a non-magnetic one-component developing device.

[0002]

2. Description of the Related Art A developer used in an image forming apparatus for developing a visible image by developing an electrostatic latent image formed on a photoreceptor includes a two-component developer composed of a toner and a carrier and a toner alone. And a one-component developer. Of these, a developing method using a two-component developer can provide a relatively stable and good recorded image, but easily causes deterioration of the carrier and a change in the mixing ratio between the toner and the carrier, and also increases the size of the apparatus. There was a disadvantage. Therefore, a developing method using a one-component developer is used in view of miniaturization, cost reduction, and reliability of the apparatus. In addition, when comparing a magnetic one-component developer and a non-magnetic one-component developer, the developing method using a magnetic one-component developer generally includes a magnetic material that is a black magnetite powder in a toner that is a developer,
It is difficult to obtain a clear color developer for colors other than black. Therefore, in order to form a multicolor image, a non-magnetic one-component toner which is a non-magnetic one-component developer is used. In addition, since the effect on the life of the photoconductor and the developing roller is taken into account and superimposition development is possible, the photoconductor on which the latent image is formed and the developer layer of the developing roller are in a non-contact state, and a DC bias is applied. A non-contact developing method is used in which a developing is performed by applying a voltage and causing toner to fly. In such a method, the development is performed without the developer layer coming into contact with the photoconductor, so that the photoconductor and the developing roller are hardly damaged by the influence of friction and the like caused by the filled and compressed developer, and This is advantageous for arranging a plurality of developing devices in the peripheral portion, performing a plurality of developments on the electrostatic latent image, and forming a multicolor image by superimposing the toner image on the photosensitive member.

For this purpose, in an image forming apparatus for exposing an image portion to form an electrostatic latent image on a photoreceptor and visualizing the latent image with toner, a developing roller for forming a minute closed electric field on the surface is used. An image forming apparatus has been proposed in which a toner supply roller is brought into contact with a toner to charge and supply the toner (for example, Japanese Patent Application Laid-Open No. 5-35071). Further, there has been proposed a developing device that forms a cloud flow of toner by contacting a developer flow path control unit and supplies the toner to a developing roller in a non-contact manner by a DC bias (for example, Japanese Patent Application Laid-Open No. 10-207226). etc).

[0004]

However, the above-mentioned image forming apparatus has the following problems. For example, in Japanese Patent Application Laid-Open No. Hei 5-35071, the developing roller and the toner supply roller are in contact with each other, so that excessive stress is applied to the toner, and the fluidity deteriorates over time. When the development is performed in a non-contact manner, there is a problem that the image density is significantly reduced. Further, in the developing device disclosed in Japanese Patent Application Laid-Open No. H10-207226 and the like, since an AC developing bias is used, when superimposing on the photoconductor, the toner image on the photoconductor tends to be disturbed. There is a problem that it is difficult to properly perform both stripping and supply. Further, since the toner supply brush and the developer flow path control unit are in contact with each other, there is a problem that stress is applied to the toner.

Accordingly, the present invention has been made in view of the above-mentioned problems, and it is possible to always supply a stable image density by efficiently supplying the toner to the developing roller without applying stress to the toner. An object of the present invention is to provide a developing device and an image forming apparatus that can be obtained. Still another object of the present invention is to provide a developing device and an image forming apparatus that prevent a blur of an image and a decrease in image density by providing a member that promotes charging of toner. It is another object of the present invention to provide a developing device and an image forming apparatus that prevent transfer of a defectively charged toner on a toner supply member to a developing roller, thereby preventing image blur and reduction in image density.

[0006]

According to a first aspect of the present invention, there is provided a brush-type toner supply roller and a developing roller, which are carried on the developing roller by a minute closed electric field. A non-magnetic one-component developing device that applies a DC developing bias to develop an electrostatic latent image on a photoconductor separated from a developing roller with toner that is separated from the developing roller; a developing roller and a toner supply roller are provided separately; This is a non-magnetic one-component developing device that applies a bias for superimposing a DC component on an AC component between a developing roller and a toner supply roller. According to a second aspect of the present invention, in the non-magnetic one-component developing device, a charging member having the same polarity as the toner is provided in contact with the toner supply roller with respect to a brush of the toner supply roller. A non-magnetic one-component developing device according to claim 1. The invention according to claim 3 is the non-magnetic one-component developing device according to claim 1 or 2, wherein the charging member is applied with a bias for superimposing a DC component on an AC component having the same phase as the toner supply roller. Device.

According to a fourth aspect of the present invention, there is provided an image forming apparatus including a plurality of developing devices, wherein the developing devices for the second and subsequent colors for performing superimposed development on a photoreceptor include a brush-like toner supply roller and a developing roller. A non-magnetic one-component developing device that develops an electrostatic latent image on a photoreceptor separated from the developing roller by applying a DC developing bias to the toner carried on the developing roller by a minute closed electric field; In the apparatus, a non-magnetic one-component developing device is an image forming device in which a developing roller and a toner supply roller are provided apart from each other, and a bias for superimposing a DC component on an AC component is applied between the developing roller and the toner supply roller. According to a fifth aspect of the present invention, in the non-magnetic one-component developing device, a charging member having the same polarity as the toner is provided in contact with the toner supply roller with respect to a brush of the toner supply roller. An image forming apparatus according to claim 4. The invention according to claim 6 is the image forming apparatus according to claim 4 or 5, wherein the charging member is applied with a bias for superimposing a DC component on an AC component having the same phase as that of the toner supply roller. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a schematic sectional view showing a developing device according to an embodiment of the present invention. FIG.
FIG. 2 is a schematic diagram illustrating a configuration of an image forming apparatus including the developing device according to claim 1. This image forming apparatus forms a two-color digital image by reversal development, and uniformly prepares the surface of the photoconductor 1 around the photoconductor 1 on which an electrostatic latent image is formed, in preparation for the first development. First charging device 2, which is charged to
A first exposure device 3 that exposes a document to form an electrostatic latent image for developing a first toner on the photoconductor 1, and develops the electrostatic latent image with a first toner to form a toner image 1 developing device 4, second charging device 5, second exposure device 6, second developing device 7, and second developing device 7 for forming a toner image with the second toner in the same manner as in the first development. A paper feed unit 8 for supplying recording paper for transferring a toner image, a transfer device 9 for applying a charge having the opposite polarity to the toner charge from the back side of the recording paper and transferring the toner image on the photoconductor to the recording paper, A cleaning device 10 for removing the toner remaining on the photoconductor 1 after the transfer and an erasing light source 11 as a static eliminator for removing charges on the surface of the photoconductor 1 in preparation for the next image formation are sequentially arranged. The photoreceptor 1 has a conductive layer on a peripheral surface of a drum-shaped substrate,
The charge generation layer and the charge transport layer are sequentially laminated, rotatably supported, and driven by a driving unit (not shown) so as to rotate in a fixed direction at a linear velocity of, for example, 200 mm / sec. The first developing device 4 and the second developing device 7 are:
A developing opening is provided at a position facing the photoreceptor 1, and a first developing roller or a second developing roller 12
, And is supported such that the peripheral surface of each developing roller faces the peripheral surface of the photoconductor 1. The first developing device 4 uses a two-component developer composed of a magnetic carrier and a toner.
The magnetic brush-shaped developer formed on the first developing roller is in contact with the photoconductor 1, and the second developing device 7 is a non-magnetic one-component developer using a color pigment. The toner layer formed on the second developing roller is
Is supported so as to maintain a predetermined distance from the peripheral surface of the.

As shown in FIG. 2, the second developing device 7 has a second developing roller 12 at an opening provided at a position facing the photoconductor 1, and the second developing roller 12 It is supported so as to rotate in the same direction as the body 1. The second developing roller 12 has a surface on which a dielectric portion and a conductor portion grounded via a DC developing power supply 18b are regularly distributed in a small area. As a result, a minute electric field is formed on the surface of the developing roller, and the amount of toner adhering to the developing roller can be increased. Photoconductor 1 and second developing roller 12
In order to keep these surfaces in a non-contact state between them, a spacer roller 13 is arranged. Photoconductor 1
A thinning blade 16 for evenly equalizing the layer thickness of the toner layer on the second developing roller 12 is provided on the peripheral surface of the developing roller 12 on the upstream side of the facing portion between the developing roller 12 and the second developing roller 12. It is provided in contact with the pressing force.

A toner supply roller 14 and an agitator 15 are provided behind the second developing roller 12 in the second developing device 7, and are supported so as to rotate in directions indicated by arrows. The toner replenished from a toner replenishing unit (not shown) is conveyed while being stirred by the agitator 15, adheres to the brush-like toner supply roller 14 by the agitator 15, and then is transferred from the toner supply roller 14 to the second
It adheres to the developing roller 12, is subsequently thinned by the thinning blade 16, and is applied to the electrostatic latent image of the photoconductor 1 by the DC developing power supply 18 b, the gap being maintained by the second developing roller 12 and the spacer roller 13. It is developed and visualized. The toner has a negative polarity. The toner has a weight average particle diameter in the range of 5 to 15 μm. 5μ
If it is less than m, the adhesion to the developing roller is strong and the developability deteriorates, and even if the image is developed, the weight is small and the image density is low, so that it is difficult to obtain a high-quality image.
If the thickness is 15 μm or more, the image is easily developed on the contrary, and is easily developed on the non-image portion of the image, and the image is easily stained.
Further, the toner is manufactured by melting and mixing a colorant with a thermoplastic resin and pulverizing the mixture. As the thermoplastic resin, a polyester resin, a styrene-acryl resin, or the like is used. As the colorant, any one of carbon black for the black toner, quinacridone-based pigment, azo-based pigment and perylene-based pigment for the red toner can be used. A toner that reproduces yellow, cyan, and magenta using other colorants may be used.

Here, the toner supply roller 14 has a core bar made of non-magnetic stainless steel, copper, aluminum, or the like, and brushed with a fiber coated with a metal fiber surface of non-magnetic stainless steel, copper, aluminum, or the like. The toner coated on the surface is frictionally charged with the toner to adsorb the toner. Here, the resin to be coated is preferably a silicone resin or a fluorine resin. In particular, a fluororesin is preferable, and a fluororesin such as vinylidene fluoride-ethylene tetrafluoride copolymer, polytetrafluoroethylene, and a copolymer resin of such a fluororesin and another resin are preferable. This resin can be appropriately selected depending on the configuration of the toner. These resins can make the charging polarity of the toner negative. The toner supply roller 14 is 0.1 to 1.0 with respect to the second developing roller 12.
It is provided with a gap of mm. Second developing roller 1
This is because, if it is in contact with 2, the toner may be stressed and may adhere to the surface of the second developing roller 12. The toner supply roller 14 has a supply bias power supply 18.
Voltages obtained by superimposing an AC component and a DC component are applied by a and 18b. Here, the AC component is 500 to 5
kHz, amplitude 100-800V, DC component -8
Use 50 to -1200V. As a result, the toner on the fiber surface of the toner supply roller 14 is
The toner is caused to fly and transfer from the toner supply roller 14 to the second developing roller 12 by the electric field between the developing roller 4 and the second developing roller 12. The flying and transfer prevent the toner from being stressed.

Next, the image formation of the image forming apparatus according to the fourth aspect will be described. When an image is formed by the image forming apparatus having the above configuration, the electrostatic latent image formed on the photoconductor 1 moves to a position facing the first developing device 4 by the rotation of the photoconductor 1. A DC bias is applied to the first developing roller at the time of image formation, and contact development with a black developer is performed while moving at substantially the same speed as the photosensitive member 1 in the circumferential direction. After the development by the first developing device 4, the photosensitive member 1 is rotated, and is sequentially transported to a position facing the second charging device 5 and the second exposing device 6. After the image is formed, it moves to a portion facing the second developing device 7. In the second developing device 7, the toner (red) is stirred by the agitator 15, moves to the toner supply roller 14 side while being charged, and electrically adheres to the surface of the toner supply roller, and
By the rotation of No. 4, the toner is conveyed to the second developing roller 12 side. At this time, the electric charge on the second developing roller 12 is also fixed by frictional charging with the toner supply roller 14. On the other hand, the toner attached to the toner supply roller 14 is
2 is rubbed between the toner supply roller 14 and the photosensitive member 1
And adheres to the peripheral surface of the second developing roller 12. The toner adhering to the second developing roller 12 is conveyed with the rotation of the second developing roller 12, and is regulated to a constant layer thickness when passing through a position where the thinning blade 16 is brought into contact. A thin layer of toner is formed on the developing roller 12. The toner layer formed in this manner is conveyed to the developing area facing the surface of the photoconductor 1 on which the electrostatic latent image is formed, with the rotation of the second developing roller 12. When a thin layer of red toner is conveyed to the developing area and approaches the surface of the photoconductor 1 on which the electrostatic latent image is formed, the red toner is transferred to the second developing roller 1.
2 fly by the bias voltage applied to
Attaches to surface. At this time, the bias voltage applied to the second developing roller 12 is a DC bias, so that the second development can be performed without disturbing the toner image formed by the first development. Are superimposed to form a two-color toner image. And
The toner image thus formed is transferred to a transfer paper (not shown) by the transfer device 9 and then fixed by a fixing device (not shown) to form a two-color image.

(Second Embodiment) FIG. 3 is a schematic sectional view showing a developing device according to an embodiment of the present invention. Here, a charging member 17 for charging the fibers of the brush-like toner supply roller 14 is provided in the second developing device 7. The charging member 17 is in contact with the toner supply roller 14 and charges the brush-like fibers of the toner supply roller 14 to attract the toner. Further, the charging member 17 is provided so as to be in contact with the brush fiber of the toner supply roller 14 so that the toner supply roller 1 can be more reliably provided.
4 can be charged. Therefore, the brush-like fibers of the toner supply roller 14 are charged to the opposite polarity to the toner, so that the charged toner can be surely adsorbed on the fiber surface. This charging member 17
The surface of a conductive metal plate made of non-magnetic stainless steel, copper, aluminum or the like is coated with a resin. As the resin to be coated, a styrene-acrylic resin, a polyester resin, or the like is preferable. As a result, the fibers of the toner supply roller 14 can be charged to a polarity opposite to that of the toner, and the toner can be adsorbed.

According to a fifth aspect of the present invention, there is provided an image forming apparatus including the developing device according to the second aspect. By providing such a second developing device 7, since a toner of the opposite polarity is not generated, it is possible to obtain a high-quality image with no stain on the non-image portion.

(Third Embodiment) FIG. 3 is a schematic sectional view showing a developing device according to a third embodiment of the present invention. The DC component is superimposed on the charging member 17 in the same phase as the AC component applied to the toner supply roller 14 and on the toner supply roller 14 on the same polarity side as the toner. Here, it is necessary to apply a bias slightly larger than the DC component applied to the toner supply roller 14 to the charging member 17.
1500 V is used. Thereby, the oppositely charged toner is removed from the toner supply roller 14, and the transfer of the oppositely charged toner to the second developing roller 12 can be prevented.

An image forming apparatus according to a sixth aspect is an image forming apparatus including the developing device according to the third aspect. The provision of the second developing device 7 completely removes the toner of the opposite polarity and prevents the toner from being supplied to the developing roller, so that the non-image portion has no stain and is high in quality faithful to the latent image. Image quality can be obtained.

[0017]

As described above, in the developing device according to the first aspect, without giving stress to the toner,
The toner can be supplied to the developing roller, and a stable image density can be obtained for a long time. In the developing device according to the second aspect, in addition to the first aspect, a charging member that comes into contact with the brush-like toner supply roller is provided to promote charging of the toner, so that image blurring and reduction in image density are reduced. Images can be obtained. In the developing device according to the third aspect, it is possible to prevent the poorly charged toner such as reverse charging on the toner supply member from transferring to the developing roller, and to more reliably prevent the image from being blurred and the image density from being lowered. can do.

Further, in the image forming apparatus according to the present invention, a stable image can be obtained for a long period of time because there is no stress on the toner. In the image forming apparatus according to the fifth aspect, since a toner of the opposite polarity is not generated, it is possible to obtain a high-quality image with no stain on the non-image portion. In the image forming apparatus according to the sixth aspect, since the toner of the opposite polarity is completely removed and the toner is not supplied to the developing roller, a high-quality image with no stain on the non-image portion and faithful to the latent image is provided. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention, including the developing device according to the first embodiment;

FIG. 3 is a schematic sectional view showing a developing device according to an embodiment of the invention described in claim 2;

FIG. 4 is a schematic sectional view showing a developing device according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 first charging device 3 first exposure device 4 first developing device 5 second charging device 6 second exposure device 7 second developing device 8 paper feeding unit 9 transfer device 10 cleaning device 11 erasing light source 12 second development Roller 13 Spacer roller 14 Toner supply roller 15 Agitator 16 Thinning blade 17 Brush charging member 18a AC power supply 18b AC power supply

Claims (6)

[Claims] 1. A direct current developing bias for an electrostatic latent image on a photoreceptor, which is provided with a brush-like toner supply roller and a developing roller, and which is carried on the developing roller by a minute closed electric field, is separated from the developing roller. A non-magnetic one-component developing device, wherein a developing roller and a toner supply roller are provided apart from each other, and a bias for superimposing a DC component on an AC component is applied between the developing roller and the toner supply roller. Non-magnetic one-component developing device. 2. The non-magnetic one-component developing device according to claim 1, wherein a charging member having the same polarity as that of the toner is provided in contact with the toner supply roller with respect to a brush of the toner supply roller. The non-magnetic one-component developing device according to claim 1. 3. The non-magnetic single component according to claim 1, wherein the charging member is applied with a bias for superimposing a DC component on an AC component having the same phase as that of the toner supply roller. Developing device. 4. An image forming apparatus comprising a plurality of developing devices, wherein a developing device for a second color and thereafter for performing superposition development on a photoreceptor includes a brush-like toner supply roller and a developing roller, and is provided with a minute closed electric field. An image forming apparatus, which is a non-magnetic one-component developing device that develops an electrostatic latent image on a photoconductor separated from the developing roller by applying a DC developing bias with toner carried on the developing roller, An image forming apparatus, wherein a developing device is provided with a developing roller and a toner supply roller separated from each other, and applies a bias between the development roller and the toner supply roller to superimpose a DC component on an AC component. 5. The non-magnetic one-component developing device according to claim 1, wherein a charging member having the same polarity as the toner is provided in contact with the toner supply roller with respect to a brush of the toner supply roller. The image forming apparatus according to claim 4. 6. The image forming apparatus according to claim 4, wherein a bias for superimposing a DC component on an AC component having the same phase as that of the toner supply roller is applied to the charging member.