JPS59142575A - Developing device - Google Patents

Abstract

PURPOSE:To cast a non-magnetic toner to a uniform thickness on a developing roller, and also to form a color picture by impressing an electric field between a magnetic roller and a surface insulating developing roller, and also destaticizing the developing roller. CONSTITUTION:A magnetic toner is a powder of 7-15mu having 10 parts carbon and 90 parts polystyrene and a carrier uses iron powder. The voltage of the same polarity as that of an electrostatic image is applied to a developing roller 11 by a power source 13. As for a magnetic roller 8, the desirable voltage of the same polarity as that of the toner is applied by a power source 16, moving the toner more onto a roller surface 14. The surface of the roller 11 is of an insulating property, and destaticized by a destaticizing means 15. The means 15 consists of a conductive fiber such as a carbon fiber, etc. The interval between the roller 11 and a photosensitive body 1 is set to 300mum, and an alternating electric field of 16KHz and 2KVpp deviating center value to DC+200V is impressed to obtain a good picture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device, and more particularly to a developing device for developing an electrostatic image formed on an image carrier such as a photoreceptor in an image forming apparatus such as an electrophotographic device. .

Hitherto, the jumping development method has been known as a unique method. In this method, the developer is applied as a thin layer onto the developer holding means, and then the thin developer layer is kept at a small distance from the surface layer. The configuration is such that the electro-electro-image planes face each other. U.S. Pat. No. 2,839, which is a method of developing by causing the developer to fly from the developer holding means to the electrostatic latent image surface using the electrostatic attraction.
(See specification No. 400 and specification No. 3,232,190)
. According to this method, developer is attracted to non-image areas where there is no latent image potential.・However, during development, the phenomenon of toner flight caused by the electric field of an electrostatic image is used, so the visible image obtained generally lacks sharpness and is unclear at the edges of the image area. When developing a line image, the original image is developed with a thin appearance, and due to the l16i filtration with a steep γ (gradient of the characteristic curve of the 1tII image density with respect to the comma-electrostatic image potential), only one image can be obtained. The result is no.

The applicant previously proposed a new developing method described in Japanese Patent Application Laid-open No. 55-18656-9. In this development method, the -component developer is uniformly opposed to the developer holding means, and an AC bias voltage of 1-1 J is applied as a development bias voltage between the developer thin layer and the electrostatic latent image forming surface. However, in the past, development was performed by changing the distance between the electrostatic latent image surface and the developer holding means over time. At the beginning of development using this development method, developer is applied to the non-image area of the static latent image for 11 minutes.
By reaching 1, the halftone area is developed,
Development is performed so that it reaches only the image area over time. As a result, a sharp image with no capri and extremely good development with halftone bleed was achieved. However, with these development methods, it is difficult to uniformly form a thin layer of developer on the developer holding means. It was important. In the case of a -component magnetic developer, in the case of a development method using a one-component non-magnetic developer, which is relatively easy to control and easy to put into practical use by using magnetic force means, a one-component non-magnetic developer is usually placed on a developer holding means such as a developing roller. A magnetic developer is supplied, charged by a frictional charging member, and then opposed to the electrostatic latent image surface. However, if the toner supplied to the developing roller is not constant, or the frictional charging member is abraded due to friction with the developing roller, the toner will fuse and aggregate on the surface of the frictional charging member and the developing roller, and the toner will not be applied to the developing roller. Nonuniformity occurs, and the charge amount of the toner also varies. This causes unevenness to appear in the copied image during development.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a developing device that enables good development using a -component nonmagnetic developer.

The apparatus according to the present invention is capable of receiving the attracted toner by contacting the magnetic brush between the magnetic roller and the magnetic roller, which forms a magnetic brush with a magnetic carrier that charges and attracts non-magnetic toner particles; In a developing device having a developing roller that guides the toner to a position facing each other with a predetermined gap and is used for development, the surface of the developing roller is electrically insulated, and non-magnetic toner is placed on the developing roller between the L1 magnetic brush roller and the developing roller. Developing is performed by applying an electric field in the direction of movement 1 and by providing a means for eliminating static electricity from the surface of the developing roller, and setting the distance between the S image holder and the developing roller to be larger than the thickness of the toner on the developing roller. .

The following will explain based on examples.

@1 In the figure, 1 is an electrostatic image carrier including an optical semiconductor layer,
2 is an #electronic image forming device including a charging device and an image exposure device; 3
Reference numeral 4 indicates a developing device according to the present invention, 4 a developing image transfer material, 5 a transfer device, and 6 a cleaning device for an electrostatic image holder.

FIG. 2 is a configuration diagram of the developing device 3 according to the present invention, in which 7 is a one-component non-magnetic toner, 8 is a magnetic roller, 9 is a non-magnetic sleeve, 10 is a magnet, and 11 is a developing roller 112 is a magnetic brush. be.

The non-magnetic toner used was a powder of 7 to 15 microns mainly consisting of 10 parts of carbon and 90 parts of polystyrene, and the magnetic carrier used was iron powder. The toner is charged to a predetermined polarity depending on the polarity of the electrostatic image. In the figure, in contrast to the positive electrostatic image, the toner is negatively charged due to friction with the carrier. As the developing roller 11, a metal roller with a relatively thin insulating layer 14 provided thereon is used. Then, in order to prevent the electrostatic image from being coupled to the developing roller and form an image with gradation, an alternating voltage biased in the same polarity as the electrostatic image is applied to the power source 13.

On the other hand, even if the magnetic roller 8 is grounded, a voltage is applied in a direction that facilitates the movement of the toner from the magnetic roller 8 to the surface of the developing roller 14, which is fine, but it is more desirable that a voltage with the same polarity as that of the toner be applied to the power supply 16. By doing so, more toner is transferred to the developer roller surface 14. In Fig. 2, a direct current voltage is applied between the magnetic roller and the ground by the power supply 16, but as shown in Fig. 3, a voltage is immediately applied by the power supply 16 between the developing roller 11 and the magnetic roller 8. Also good.

The layer thickness can be further adjusted.

The relationship between image density and toner thickness is usually 4 to 15μ.
This applies to the front and rear toner particles, and when the toner layer is around 30μ, the developed image density is easily affected by fluctuations in the toner layer thickness, whereas when it is 30μ or more, the density is saturated. There is a tendency.

Therefore, if the image density is less than 30μ, the image density is unstable and it is essential to control the toner layer to maintain its uniform distribution, but if it is more than 30μ', it is appropriate and a good density can be obtained easily.

On the other hand, when the toner layer is 100 μm or more, it has reached a substantially saturated state, so there is no problem with the density.

Therefore, in order to adjust the gap with respect to the electrostatic image carrier d', the toner layer thickness within this range can be arbitrarily used. However, an increase in the thickness of one layer of toner on the other hand leads to an increase in toner replenishment and non-uniformity of toner charge in one layer of toner, which tends to cause ground force blur, so it is preferable to develop with a sheet of 100 μm or more.

In the example of FIG. 2, such a toner layer thickness is
This could be achieved by applying a voltage of 0 to -50 V as the voltage of 6, and -200 to -1000 V in the example shown in FIG.

In addition, when adopting the aperture method in which the voltage of the alternating voltage applying means 13 of the developing row 2- is adjusted in order to adjust the density of the developed image, the power supply 1 to the magnetic roller 10 in the example of FIG.
It is desirable to adjust the applied voltage from 6 by adjusting the bias of the alternating voltage applying means 13 to match the DC component.

On the other hand, in the example shown in FIG. 3, such adjustment is not necessary because the electric field between the developing roller and the magnet roller is constant.

As described above, since a high voltage is applied between the developing roller and the magnet roller, the surface of the developing roller 11 needs to be insulating. This surface insulation is sufficiently thick so that no discharge occurs between the carrier particles restrained by the developing roller and the magnetic roller, and only requires an electric field between the photoreceptor 1 and the developing roller 11 by the alternating electric field applying means 13 during development. It must also be thin enough to be applied.

Therefore, it is desirable that the surface insulating layer thickness 14 is about 2 to 200 μm. The surface insulating layer 14 is dipping.

It can be coated, heat-shrinkable tube, etc.

Further, when the surface insulating layer 14 is charged due to friction with carrier particles, it becomes difficult for toner particles to transfer from the magnetic roller to the surface of the developing roller, and coating becomes more likely to become uneven. Therefore, a highly stable coating can be obtained by eliminating static electricity from this surface insulating layer.

Figures 2 and 3. In the figure, reference numeral 15 indicates a static eliminating means for the developing roller, and as an example of this static eliminating means, conductive fibers such as carbon fibers, conductive treated chemical fibers, or plated chemical fibers can be used. By grounding these, the surface of the developing roller can be neutralized.

Further, as another static eliminating means, a metal such as phosphor bronze or stainless steel may be used and brought into contact with the developing roller surface 14 as shown in FIG. 4, 17. In such a case, these static eliminating members 1
5 and 17 have the role of removing the fibers from the surface 14 of the developing roller and scraping off the toner on the developing roller. Scraping off the toner in this manner is always effective in making the thickness of the toner on the developing roller 2 uniform.

Further, as other static eliminating means, a corona charger or the like may be used to eliminate the surface of the developing roller. At this time, the corona charger is preferably a direct current or alternating current corona charger having a polarity opposite to that of the toner.

The static eliminating means 15 and 17 as described above were provided, and the distance between the developing roller and the photoreceptor was set to 300 μm.
, :2KVpp, and an alternating electric field whose center value was biased to DC +200V was applied, and a good image was obtained.

Note that in the case where the static eliminating means was not provided, a phenomenon occurred in which the image density decreased as the developing action was repeated. At this time, when the potential on the surface of the developing roller was measured, it was found that it was charged to the same polarity as the toner.

As explained above, the present invention transfers the toner particles on the magnetic roller with magnetic carriers adsorbed onto the developing roller and develops the thin layer of toner on the roller by insulating the surface of the developing roller and magnetically A good image can be obtained without applying an electric field L1 between the roller and the developing roller and removing the developing roller by the static eliminating means. Also, magnetic 11
It is now possible to use color toners that cannot be used with mitoners, and it has become possible to form color images.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the entire electrostatic recording process to which the developing device of the present invention is applied. FIG. 2 is a schematic diagram of the phenomenon apparatus of the present invention. FIGS. 3 and 4 are schematic diagrams of other developing devices of the present invention. 1-111 electrostatic image carrier, 2-+-electrostatic image forming device including charging device and image exposure device, 3-11 developing device related to Honkomei, 4-m-developed image transfer material, 5-111 Transfer, device, 6----Electrostatic image carrier cleaning device, 7--
---component non-magnetic toner, El---magnetic roller,
9-111 non-magnetic sleeve, l O-magnet 111---
- Developing roller, l 2 - - - Magnetic brush, 13 -
---One alternating voltage reduction source, 1 4---One-piece image roller surface insulator, 15.17--- Static elimination means, 16--- One power source. Applicant: Canon Co., Ltd. 81 Hard foil? figure

Claims (1)

[Claims] A magnetic roller that adsorbs a magnetic carrier to form a magnetic brush for charging the monocomponent thread non-magnetic toner, and a magnetic roller whose surface is electrically insulating. It has a developing roller that develops the latent image on the holding body, means for applying an electric field between both rollers in a direction in which the toner moves from the magnetic roller onto the developing roller, and means for neutralizing the surface of the developing roller. A developing device that develops a latent image by setting the distance between the holder and the developing roller to be larger than the thickness of the toner on the developing roller.