JPS62279374A - Electrophotographic developing device - Google Patents

Abstract

PURPOSE:To prevent a streaky flaw from being formed in a toner layer on the 1st roll by bringing a magnetic thin plate provided rotatably into contact with the 2nd roll at any time by a magnet in the 2nd roll to constant contacting pressure, and forming a toner layer which has uniform thickness in the axial direction of the 2nd roll. CONSTITUTION:The magnet 7 provided in the 2nd roll 5 opposite the magnetic thin plate 8 attracts the magnetic thin plate 8, which contacts the surface of the 2nd roll 5. When the 2nd roll 5 rotates as shown by an arrow, toner 4 sticks on the surface of the 2nd roll 5 while charged electrostatically by friction and passes through the contacting part between the magnetic thin plate 8 and the 2nd roll 5 form the toner layer having constant thickness on the 2nd roll 5, and the toner layer is transferred onto the 1st roll 6 at the position opposite the 1st roll 6. Thus, an electrostatic latent image is developed by the toner layer formed on the 1st roll 6.

Description

Detailed Description of the Invention V. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic developing device, and more specifically, a first roll for completely developing an electrostatic latent image, and a first roll for developing an electrostatic latent image. The present invention relates to an improvement of a developing device comprising a second roll that supplies developer to the roll.

[Conventional technology]

When fully developing and visualizing an electrostatic latent image in electrophotographic technology, is there a developing device that develops the electrostatic latent image with one developing roll and multiple rolls? In the latter type of developing device, two or more rolls are placed side by side in a non-contact state, and a single layer of toner is formed on the roll closest to the toner hopper. One layer of toner is sequentially transferred onto adjacent rolls by electrostatic force, and finally the electrostatic latent image is developed in a non-contact state by the one layer of toner transferred and formed on the roll disposed closest to the electrostatic latent image. ing. In such a developing device, in order to obtain good copies, it is necessary to always form a good toner layer of a constant thickness on the roll directly involved in the development. 1
As a known technique using multiple developing rolls, Japanese Patent Application Laid-Open No. 47
-13088, Japanese Patent Publication No. 51-36070, and the like. These publications describe a method in which a toner thickness regulating member such as a rubber blade or a metal blade is brought into contact with the developing roll or by maintaining a minute gap with the developing roll to form a thin toner layer on the roll. With this method, it is difficult to obtain a uniform pressure distribution over the entire axial length of the roll, which tends to cause unevenness in the thickness of the toner layer, and it is difficult to precisely maintain minute gaps, so that the toner does not reach the roll during long-term use. It has the disadvantage of causing sticking. In addition, streaks are more likely to occur in the toner due to blocking of the toner itself or the intrusion of foreign matter, which is particularly detrimental to the development of solid areas. Developing devices using a plurality of rolls are described in Japanese Patent Laid-Open Nos. 53-53632, 185052-1982, and 2853-1988. Although this type of developing device can relatively effectively prevent streaks and unevenness in the single layer of toner to be formed on the roll, it is not possible to obtain a uniform pressure distribution over the entire roll axis direction, so It is difficult to form a uniform thin layer of toner on the roll. In addition, since the amount of toner transferred to the last roll for development 2 is small, if a large number of solid images are continuously developed, the toner layer on the developing roll will rapidly become thinner, resulting in an 8 degree drop in the resulting image.

Furthermore, when a metal blade, rubber blade, or the like is used as a layer thickness regulating member for one layer of toner, a toner cloud is likely to occur.

[Problem that the invention seeks to solve]

The present invention carries and conveys toner on a developer conveying member,
It is an object of the present invention to provide an electrophotographic developing device that eliminates the above-mentioned drawbacks of conventional developing devices for developing electrostatic latent images.

Furthermore, the present invention provides a developing device comprising a first roll for developing an electrostatic latent image and a second roll for supplying developer to the first roll, in which the thickness of a single layer of toner to be formed on the second roll is adjusted. ? What are the drawbacks of the conventional methods as mentioned above, such as being able to always be constant? It is an attempt to provide an electrophotographic device that eliminates the above problems.

〔problem? Means/effect for solving the problem] The above intermediary point is the second point in an electrophotographic developing device consisting of a first roll that develops an electrostatic latent image and a second roll that supplies developer to the first roll. A magnetic thin plate provided on the outside of the roll and a second
A magnet is provided at a position facing the magnetic thin plate inside the roll, and one end of the magnetic thin plate is provided. The middle part of the magnetic thin plate is rotatably supported and arranged so as to be able to contact the second roll, and the developer is passed through the contact area between the magnetic thin plate and the second roll to keep the developer constant on the second roll. This problem is solved by an electrophotographic developing device which forms a thick developer layer and transfers the developer layer on the second roll onto the first roll to develop an electrostatic latent image.

The present invention will be explained in more detail below with reference to the drawings.

In FIG. 1, (1) is a photoreceptor consisting of a photosensitive layer (2) and a substrate (3), and an electrostatic latent image (not shown) formed on the photosensitive layer by electrophotography is the first Roll (6)
It is developed by a thin layer of toner that has been formed on top. (
8) is a magnetic thin plate, which is rotatably supported (9) on a hopper (10) containing toner (4). A magnet (7) is located at a position facing the magnetic thin plate inside the second roll (5) for completely transferring the toner to the first roll (6).
is provided, so that the magnetic thin plate is attracted by the magnet and is in contact with the surface of the second roll. Therefore, for example, when the first roll (5) made of an aluminum hollow sleeve rotates in the direction of the arrow K, the toner adheres to the surface of the first roll while being triboelectrically charged, and is transferred to the magnetic thin plate (8) and the second roll (5). ) contact area? The toner is passed through to form a single layer of a constant thickness on the second roll, and the first toner is
One layer of tona on the roll? Transfer. The toner layer thus formed on the second roll develops the electrostatic latent image as described above.

In the developing device of the present invention, charge is imparted to the toner on the second roll by frictional charging with a non-magnetic sleeve forming the roll, charging by a corona charger, charge injection by electrostatic charge, etc. This can also be done.

In the former case, a material that is different from the toner material in terms of electrical charge is used for the sleeve, but in the latter case, a resistive layer is provided on the sleeve surface. The sleeve surface may be smooth, but
The toner transportability of the surface can be improved by sandblasting or the like. The thickness of the toner layer formed on the second roll is determined by the magnetic force of the magnet provided in the second roll.
It can be controlled by the material (magnetic permeability, etc.), shape (thickness, etc.) of the magnetic thin plate, and the rotational speed of the second roll, and the thickness of the single layer of toner formed on the first roll can be controlled by controlling the thickness of the toner layer formed on the first roll.
Besides the electrical transition conditions between the roll and the second roll, it can also be controlled by the speed difference between the two rolls. Generally, the relationship VPA≦vt<v is satisfied between the rotational speed of the photosensitive drum (V pA'), the rotational speed of the first roll (vl), and the rotational speed of the second roll (vz). Preferably, the rotation speed is selected. The transfer of one layer of toner from the second roll to the first roll takes place electrically by applying a bias voltage vz * vt 5t to both rolls. Approximately 3 x 10'V/c when applying a DC electric field
m is preferable, and when applying an alternating electric field, the frequency (f
) 400Hz ~2kHz2, potential difference (V,, -p)
500-1500V is preferred. Generally, the transfer efficiency is better when using an alternating electric field. Transfer of toner from the first roll to the surface of the photoreceptor is performed by direct current or alternating current flying. Further, in order to keep the charging history and toner charge amount constant, it is preferable to provide a scraper on each roll.

[Implementation F! II] In the apparatus shown in Fig. 1, the surface oxidized diameter 37
(7) A block magnet with a magnetic force of 800G in the second roll made of a φ aluminum hollow sleeve)
f was installed. As a magnetic thin plate, it was rotatably attached to a permalloy tape (manufactured by Hitachi Metals, Ltd., 88-aooo4)t-) with a thickness of 100 μm. The first roll has a diameter of 376
5US-504 non-magnetic hollow sleeve with nφ. Gap between the first roll and the second roll g! are Q, 3Ws, and the gap g between the photoreceptor with the selenium photosensitive layer and the first roll is
! was also 0.3 gm. Furthermore, the moving speeds of the photoreceptor, first roll, and second roll were all set to 127/sec. The electrostatic latent image potential on the photoreceptor is +800V, and the bias voltage of the first roll v1 and the bias voltage of the second roll V! The electrostatic latent images were developed in the following manner.

DC electric field: Vl = -400V, V2 = +20
0 V cross R1i field: Vl (f=4oaHz, vp-
p = 1aoov) = Ov Vl (f = 400Hz, vp-p = 500V) =
-1-2aav Toner used: particle size 13p, density a, qyl tan 3 Under the above conditions, a uniform toner thin layer was obtained on the first roll, and a dense copy image with excellent graininess was obtained even in the solid image area. It was done. The toner conveyance amount of the second roll is 1.1, the first roll is dusted at 131η/α2, and the developed weight of the solid part is α2.
It was 2m9/σ2. In addition, thin streaks l-j found in a single layer of toner on the second roll disappear when the toner is transferred to the first roll, and a uniform layer of toner without streaks is formed on the first roll. It was observed that

〔Effect of the invention〕

According to the electrophotographic developing device of the present invention, since the rotatably provided magnetic B-mome is always brought into contact with the second roll with a constant contact pressure by the magnet in the second roll, A single layer of toner having a uniform thickness in the axial direction can be formed. In addition, since the first roll and the second roll are separated, the toner does not stick to both rolls, and the thickness of the toner layer on the first roll is made smaller than the thickness of the toner layer on the second roll. The generation of streaks in the single layer of toner on the first roll is prevented. Since the toner is quickly transferred from the second roll to the first roll, there is no reduction in image density even when all solid images are continuously copied. Furthermore, since the toner charge distribution can be made uniform, copies with good image quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an electrophotographic developing apparatus of the present invention. Symbols in the figure: 1... Photoreceptor, 2... Photosensitive layer, 3...
Substrate, 4...To? -+, 5... 2nd roll, 6.
...First roll, 7... Magnet, 8... Magnetic thin plate, 9
...-Axis support, 10... Toner hopper.

Claims (1)

[Claims] In an electrophotographic developing device consisting of a first roll that develops an electrostatic latent image and a second roll that supplies developer to the first roll, a magnetic thin plate provided on the outside of the second roll and an inside of the second roll are used. a magnet provided at a position facing the magnetic thin plate, one end of the magnetic thin plate is rotatably supported, and an intermediate portion of the magnetic thin plate is disposed so as to be able to contact a second roll; By passing the developer through the contact area with the second roll, a developer layer of a constant thickness is formed on the second roll, and the developer layer on the second roll is transferred onto the first roll to form an electrostatic latent. An electrophotographic developing device characterized in that it develops an image.