JPH0213792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method and apparatus, and more particularly to a developing method and apparatus that enable development without rubbing the surface of a latent image carrier using a two-component developer.

Conventionally, various two-component developers have been widely used to develop latent images formed on image carriers such as electrophotographic photoreceptors. In particular, a two-component developer containing a non-magnetic toner and a magnetic carrier enables compact and effective development using a magnetic brush development method or the like. For magnetic development, one-component developers using magnetic toner are also used, but one-component developers contain black magnetic material, making it difficult to obtain the desired color developer, so they are not suitable for color image formation. In this case, the method using the two-component developer described above is superior.

For example, a two-color color developing method and apparatus are disclosed in Japanese Patent Application Laid-Open No. 83069/1983 as a method for easily obtaining color images. FIG. 1 shows the main parts of a two-color color device. After a first exposure 2 is applied to the photosensitive drum 1, a first development 3 is performed, followed by a second exposure 4, and a two-color developed image is formed on the photosensitive drum through a second development 5. Subsequently, the image is transferred onto a transfer material 7 by a transfer roller 6. Conventional 2
In the color development method and apparatus, since both the first and second development are two-component magnetic brush development, in the second development step, the image (for example, black) that has already been formed by the first development is There was a problem that the first latent image was disturbed by the magnetic brush in the second developing section, and the first latent image was further developed by the second developing process, resulting in color mixing (for example, red was placed on top of the black developed image). .

On the other hand, as an alternative to the magnetic brush developing device, there is a jumping developing device using a one-component developer as disclosed in Japanese Patent Laid-Open No. 54-43037. In the case of jumping development, since the latent image surface and the toner layer face each other with a distance between them, the problem of disturbance of the first developed image in the second developing section, which occurs in a magnetic brush developing device, does not occur. That is, the first developed image is not scraped off by the carrier in the second developing section. Also the first
If the polarities of the latent image and the second latent image are reversed and the polarities of the first developer (for example, black) and the second developer (for example, red) are mutually different, color mixing will not occur, so the ideal two
Color development is possible. However, a one-component developer for jumping development has magnetite and resin as its main components, and the color of the magnetite material is black or brown, so even if you make a red developer by coloring it with resin, The above-mentioned disadvantage of magnetic developers is that when they are heated and fixed onto a transfer material, the resin melts and the magnetite is exposed on the surface, resulting in extremely poor color reproducibility in the resulting copies.

The present invention has been made in view of the above-mentioned points, and relates to a developing method and apparatus that enable good image formation without disturbing latent images or developed images on an image carrier.

The present invention includes a developer storage container containing non-magnetic toner and a magnetic carrier, a non-magnetic cylinder that rotates with a part facing the container and a part facing the latent image carrier, and a developer storage container containing non-magnetic toner and a magnetic carrier. A fixed magnet having a plurality of magnetic poles arranged only in a portion where the non-magnetic cylinder faces the container, and among the plurality of magnetic poles, a magnetic pole on the most downstream side with respect to the rotation direction of the non-magnetic cylinder. a magnetic member disposed to face the non-magnetic cylinder so as to form a magnetic field between the magnetic members, and a magnetic member that is arranged to face the non-magnetic cylinder so as to form a magnetic field between the magnetic members, and a magnetic carrier that is magnetized with a magnetic pole that is upstream in the rotation direction of the non-magnetic cylinder from the most downstream magnetic pole. The magnetic carrier and non-magnetic toner are transported by the rotation of the non-magnetic cylinder by being attracted to the non-magnetic cylinder, and the magnetic carrier is restrained by the magnetic field at the position of the magnetic member to allow the non-magnetic toner to pass through. This is a developing device characterized by developing a latent image.

Hereinafter, details of the present invention will be explained using specific examples with reference to the drawings.

FIG. 2 shows an embodiment of the invention. 1 is a photosensitive drum as a latent image carrier; 8 is a non-magnetic cylindrical developing sleeve that holds a developer; 9 is a magnetic member such as a magnetic blade; 10 is a magnetic carrier 11 and a non-magnetic toner 1
2 is a two-component developer, 13 is a magnet in the sleeve, and 12 is a non-magnetic toner. 14 is a developer storage container (hereinafter referred to as a developing container); 15 is a bias power source for applying a bias voltage to the developing sleeve 8; the developing container 14 is provided with a stirring blade 17 that rotates around a shaft 16; In the developer container, the carrier 11 and the non-magnetic toner 12 are weakly coupled by electrostatic force, and the magnet 13
-3, 13-2 is adsorbed. This adsorbed two-component developer 10 is conveyed to the magnetic blade 9 by rotation of the sleeve. During this conveyance process, the two-component developer 10 consisting of the non-magnetic toner 12 and the carrier 11 is attracted to the surface of the sleeve 8 by magnetic force and rubs against it, so the non-magnetic toner 12 is also electrostatically charged on the surface of the developing sleeve 8. It is absorbed by force. In the magnetic blade 9, carrier particles are retained and scraped off from the surface of the sleeve 8 due to the magnetic field between the magnet (also referred to as a developer cut magnetic pole) 13-1 and the magnetic blade 9. On the other hand sleeve 8
The non-magnetic toner 12 adhering to the surface of the blade 9 passes through this blade 9 without being affected by this magnetic field.
A thin layer of nonmagnetic toner 12 is formed on the surface of the sleeve 8 and is supplied to a developing section where the photosensitive drum 1 and the developing sleeve 8 are close to each other. In order to prevent the particles of the carrier 11 from leaking out from the blade 9, the developer cut magnetic pole 13-1 is tilted toward the developer container 14 by 5 to 15 degrees (θ in the figure). By limiting all the magnetic poles within the developer container 14 in this way, the magnetic blade 9
Since leakage of magnetic flux from the carrier 1 to the developer side is prevented and the magnetic flux is limited only to the inside of the developer container 14,
1 is almost never taken out from the blade 9 section. Figure 3 shows the state of the magnetic field at this time. The distance d between the photosensitive drum 1 and the developing sleeve 8 is sufficiently wide so that the thin toner layer 12 does not come into contact with the surface of the photosensitive drum 1 in the absence of an external electric field. During development, by setting the developing sleeve roller to a predetermined potential using the bias power supply 15, desired image quality can be obtained.

In this embodiment, the non-magnetic toner is charged by friction with the carrier and sleeve surfaces. Preferably, the surface of the carrier is coated with an oxide film or an insulating treatment such as a resin that is at approximately the same electrostatic level as the toner, so as to reduce the triboelectricity imparted from the carrier to the toner, and to receive the triboelectricity necessary for development from the sleeve surface. By doing so, deterioration of the carrier can be prevented and toner can be easily applied to the sleeve surface. Since the carrier is not directly involved in development and only plays the role of transporting and stirring the non-magnetic toner to the sleeve surface, it is only necessary to replenish the non-magnetic toner. The magnet 13 fixed within the sleeve is arranged so that a magnetic field exists only on the developer container 14 side, and the magnetic flux on the sleeve surface is required to be 400 to 600 G. The surface roughness of the sleeve 8 is controlled to R _z = approximately 1 to 5 μm by sandblasting or the like in order to promote the conveyance of the two-component developer 10 and to increase the opportunity for the non-magnetic toner 12 to come into contact with the surface. do.

Experiments were conducted using the configurations of the first developing device and the second developing device as described below, and the effects of the present invention were revealed as follows.

Developing sleeve 8: Outer diameter 32φ, made of non-magnetic stainless steel, surface sandblasted R _z = 3 μm Rotation: Same peripheral speed as the drum (300 mm/s) Magnet 13: 400 Gauss on the surface of the developing sleeve Developing sleeve 8 and magnetic blade 9 Between a=
0.5mm developer cut magnetic pole 13-1 and cut blade 9
Inclination angle θ=10° Between developing sleeve 8 and photosensitive drum 1〓d=
0.3mm The first developer is a two-component developer with a black toner and the second developer is a magenta toner (each is a well-known non-magnetic resin toner) The carrier is the same kind of magnetic material The first latent image is positive, the second latent image is The material was selected to have a negative polarity, whereas the black toner has a charge similar to that of the magenta toner. The bias power supply 15 supplies the developing sleeve 8 with a frequency of 600Hz, a peak-to-peak value of 1.5KV, and a center value with the same polarity as the latent image.
An AC bias voltage of 150V was applied.

As a result of image formation under the above conditions, the final image obtained on the copy after the first development and second development was overheated after transfer was good with no disturbances caused by the second development and almost no color mixture. The image quality was good.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram explaining the conventional developing method, Fig. 2 is an explanatory diagram of an embodiment of the developing device of the present invention, and Fig. 3 shows the magnetic flux generated by the fixed magnet provided in the developing sleeve. This is a conceptual diagram. 8...Developing sleeve, 9...Magnetic blade, 1
1...Carrier, 12...Nonmagnetic toner, 13...
...Magnet, 15...Bias power supply, a...Between〓, d...Between〓, θ...Tilt angle.

Claims (1)

[Scope of Claims] 1. A developer storage container containing non-magnetic toner and a magnetic carrier, a non-magnetic cylinder that rotates with a part facing the container and a part facing the latent image carrier, and this non-magnetic cylinder. A magnet fixed in a magnetic cylinder, which has a plurality of magnetic poles arranged only in a portion where the non-magnetic cylinder faces the container; a magnetic member disposed to face the non-magnetic cylinder so as to form a magnetic field with the downstream magnetic pole, the magnetic member being magnetic at the magnetic pole upstream in the direction of rotation of the non-magnetic cylinder from the most downstream magnetic pole; The carrier is attracted to the non-magnetic cylinder, the rotation of the non-magnetic cylinder transports the magnetic carrier and the non-magnetic toner, and the magnetic carrier is restrained by the magnetic field at the position of the magnetic member to allow the non-magnetic toner to pass through. A developing device characterized by developing a latent image in layers. 2. The magnetic member is further positioned than the most downstream magnetic pole.
The developing device according to claim 1, wherein the developing device is located at a downstream position with respect to the rotational direction of the non-magnetic cylinder. 3. The developing device according to claim 1 or 2, further comprising a bias power source that forms an alternating bias electric field between the latent image carrier and the non-magnetic cylinder.