JPH03259280A - Developing device - Google Patents

Abstract

PURPOSE:To maintain a stable carrying state and a developing state by making the surface roughness of a developing roller having a cylindrical thin film member smaller than the minimum magnetizing and inverting interval of a magnetic field generation layer and smaller than the volume average grain size of one component magnetic toner. CONSTITUTION:The magnetic field generation layer 22 is disposed on a thin film member 12 being the cylindrical thin film member and an electrically conductive layer 23 is disposed on the layer 22. Then, the layer 22 is magnetized in a horizontal direction so as to reduce a magnetizing and inverting pitch. Due to that, a fine toner chain by the toner 24 is formed on the conductive layer 23 and a thin and stable toner layer can be obtained. Besides, the surface roughness of the conductive layer 23 being the contact surface of the developing roller and the toner 24 is made sufficiently smaller than the minimum magnetizing and inverting interval and set to be equal to or under the volume average grain size of the toner 24 at the same time. As the result, the contact area of the toner 24 and the conductive layer 23 is sufficiently secured and the triboelectric charge performance of the toner 24 is improved and stably maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a developing device that uses a one-component magnetic toner, and more specifically, a developing device that conveys the one-component magnetic toner by a developing roller having a cylindrical thin film member. The present invention relates to a developing device that performs development.

[Prior Art] As disclosed in Japanese Patent Application Laid-Open No. 64-65579, a conventional developing device elastically attaches an excess portion of a cylindrical thin film member sleeve having an excess circumferential length to a drive roller onto a photoreceptor. By bringing them into close contact, it was possible to transport and develop non-magnetic toner.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the force that holds the toner on the developing roller is based on electrostatic mirror image force and adhesive force, so it is difficult to make the amount of toner conveyed uniform. Ta. Furthermore, when toner is developed on a latent image bearing member such as a photoreceptor, uncharged toner or toner with a non-regular polarity is developed in the non-image area, and there is significant ground blur (toner is not formed in the non-image area) on the latent image bearing member. Since only toner of the correct polarity is transferred to the recording paper, an image without blurring can be obtained on the recording paper, but the toner that is not transferred and is wasted unnecessarily. In many cases, this is not only uneconomical, but also requires a large amount of space for the waste toner container, making the image forming apparatus larger.

The present invention is intended to solve these problems.The purpose of the present invention is to stably form a thin layer of toner on a magnetic developing roller so that the amount of toner conveyed is stable and there is little density unevenness. The company provides a developing device. Still another object is to provide a developing device that causes less contamination due to toner scattering and can reduce unnecessary waste toner. Still another object is to provide a developing device that has a simple structure and is applicable to small, low-cost image forming apparatuses.

Still another object is to provide a developing device with high resolution and high image quality.

[Means for Solving the Problems] A developing device of the present invention is a developing device that conveys a one-component magnetic toner by a developing roller and develops the one-component magnetic toner onto a latent image carrier, in which the developing roller is a cylindrical thin film. the member and a drive roller that contacts at least a portion of the inner circumferential side of the cylindrical thin film member, the thin film member has at least a magnetic field generating layer, and the surface roughness of the developing roller is such that the surface roughness of the developing roller is equal to or smaller than the minimum magnetization of the magnetic field generating layer. It is characterized by being smaller than the reversal interval and smaller than the volume average particle diameter of the one-component magnetic toner.

[Function] According to the above structure of the present invention, the structure of the developing roller is simplified by conveying the toner near the surface of the thin magnetic field generating layer and configuring the developing roller with a single rotating body. By making the surface roughness of the developing roller smaller than the minimum magnetization reversal interval, the magnetic binding force acting on the toner on the developing roller is made uniform, resulting in a stable and thin developing roller. It is possible to obtain a stable development prevention force during stratification and development, and reduce ground force blur, and by making the surface roughness of the developing roller smaller than the volume average particle diameter of the toner, it is possible to reduce the retention of toner on the developing roller. This prevents toner from being charged and transported stably. Therefore,
The thin magnetic field generating layer is magnetized at a minute pitch to form a uniform, thin toner layer (or a thin layer of magnetic brush at a minute pitch) on the developing roller, thereby controlling magnetic field fluctuations and toner layer thickness. It is possible to perform high-resolution development by reducing density unevenness and background blur caused by fluctuations.

Hereinafter, the present invention will be explained in detail with reference to Examples.

[Example] FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus using a developing device of the present invention, in which a latent image carrier 1 is coated with an organic or inorganic photoconductive material on a conductive support 2. After the photosensitive layer 3 is charged using a charger 4 such as a corona charger or a charging roller, a laser or L
Light emitted from a light source 5 such as an ED is selectively irradiated onto the photosensitive layer 3 according to an image through an imaging optical system 6 to obtain a potential contrast and form an electrostatic latent image. On the other hand, the developing device 7 conveys and develops the magnetic toner 8, and the developing roller 9 that conveys the toner 8 is rotatably driven and has a friction part etc. on the outer periphery of the driving roller 10 and the outer periphery of the driving roller 10. It is composed of a cylindrical thin film member 11 that is externally packaged with a surplus remaining, and a magnetic field generating layer 12 is placed on the cylindrical thin film member 11.
The magnetic toner 8 is held directly on the developing roller 9 by leakage magnetic flux around the outer periphery of the magnetic field generating layer 11, and an appropriate amount is held by a thin plate spring-like elastic blade 13 made of non-magnetic or magnetic metal or resin. The developing roller 9 is rotated to convey the thin layer of toner 8. The developing roller 9 is pressed against the latent image carrier 1 with a predetermined pressure, and when the toner 8 on the developing roller 9 is conveyed to the pressure contact portion, the potential contrast of the latent image carrier 1 and the developing bias applying means 14 are applied. Toner 8 charged according to the developing electric field adheres to the latent image carrier 1, and the electrostatic latent image is visualized. Further, a toner image is transferred onto the recording paper 16 using a transfer device 15 such as a corona transfer device or a transfer roller, and the toner is fixed on the recording paper using heat or pressure to obtain a desired image on the recording paper. It is. Note that the pressure with which the developing roller 9 is pressed against the latent image carrier is approximately 0.5 [kgf] to maintain a stable developing state, and the blade 13 is not limited to an elastic blade. A known toner transport amount regulating member such as a rigid blade can be used. When line images, character images, and solid images of 600 [DPI] were continuously formed on 10,000 sheets using an image forming apparatus as shown in Fig. 1, the line images of JOO [DPI] did not become thick. It is stably formed, the resolution of the line pair image is sufficiently large, there is no tailing or blurring at the edge of the image, and a high density solid image with an OD value of 184 or more can be stably formed, and it can be printed on recording paper. Not only was there no ground force blur, but there was also no ground force blur on the latent image carrier, making it possible to significantly reduce the amount of waste toner.

In FIG. 1, the drive roller 10 has a resin or metal shaft with natural rubber, silicone rubber, urethane rubber, etc.
Butadiene rubber, chloroprene rubber, neoprene rubber,
A friction part is provided using NBR or the like, and the thin film member 1
1 is pressed against the drive roller IO to transmit rotational driving force.

Further, the thin film member 11 can be made of a metal thin film such as phosphor bronze, stainless steel, or nickel, or a resin thin film material such as nylon, polyimide, or polyethylene terephthalate.
The thickness of the thin film member 11 varies depending on the material, but in order to obtain sufficient pressure contact with the latent image carrier, it is 10 to 500 [μm].
Furthermore, the magnetic field generation layer 12 can be made of a known magnetic recording material or magnet material, and more specifically, Fe, Ni, Co,
Magnetic materials containing at least one element among Mn, such as y-Fe, 03, Ba-Fe, Ni-
Co, Co-Cr, Mn-Al, etc. can be used, and the film thickness is 100 [μm] or less, preferably around 10 [μm], and the minimum magnetization reversal pitch is 100 [μm] or less (both horizontal and perpendicular magnetization). This makes it possible to uniformly thin the toner and at the same time suppress variations in the amount of toner conveyed on the developing roller due to magnetic brush formation to a minute pitch, thereby reducing density unevenness. Further, as the toner used in the present invention, all toners known as one-component magnetic toners can be used, and the composition of the developer may be either resin-based toner or wax-based toner, as is known in the art.
It is made by adding magnetic powder, colorants, external additives, and other additives to resin, and is created by pulverization or polymerization methods.

In addition, in FIG. 1, the present invention is not limited only to the configuration in the figure, and although the arrows indicate the rotation direction of each member, the present invention is not limited to the present invention.Furthermore, the developing method is also It can be used regardless of whether it is regular development or reversal development.

FIG. 2 is a cross-sectional schematic view of a cylindrical thin film member in an embodiment of the present invention, in which a magnetic field generation layer 22 is provided on the thin film member 21, and a conductive layer 23 is provided on the magnetic field generation layer 22. By magnetizing the magnetic field generation layer 22 in the horizontal direction so that the magnetization reversal pitch is 100 [μm] or less, a minute toner chain is formed by the toner 24 on the conductive layer 23, resulting in a thin and stable toner layer. is obtained. The surface roughness of the conductive layer 23, which is the contact surface with the toner 24 of the developing roller, is made sufficiently smaller than the minimum magnetization reversal interval (approximately 80 μm in the figure) so that the thin layer of the toner 24 has a surface roughness that is equal to the surface roughness of the developing roller. The toner 24 is made of conductive M2S so that the surface roughness is less than or equal to the volume average particle diameter of the toner 24 (about 10 [μm1 in the figure), preferably about 1/2 of the volume average particle diameter, and the toner 24 does not become non-uniform.
It prevents the toner from sticking to the top and is conductive to the toner 24 [23
This is to ensure a sufficient contact area with the toner 24, thereby improving the triboelectric charging properties of the toner 24 and stably holding it. Further, by applying a developing bias voltage to the conductive layer 23, it is possible to improve the developing electrode effect and obtain a high-resolution image. Furthermore, conductive JI2
If the conductive layer 3 is formed of a metal thin film containing Ni, Or, etc., the conductive layer 23 functions as a protective film for the magnetic field generating layer 22, and the life of the developing roller can be extended. Note that the arrows in the figure indicate the direction of magnetization, and the magnetic field generation layer 22 may be a perpendicularly magnetized film.

The present invention has been explained above using Examples, but regarding the layer structure of the thin film member of the developing roller, in addition to the magnetic field generation layer, a conductive layer or an insulating layer may be appropriately disposed to improve the developing electrode effect. The chargeability of the toner can be improved, and in addition, a protective layer can be provided to improve durability, and an intermediate layer can be provided to improve moldability. Furthermore, the magnetic field generation layer of the developing roller can be used in various magnetized states such as line magnetization, lattice magnetization, and spiral magnetization. A stable thin toner layer can be formed on the developing roller by magnetizing the toner so that the reversal interval is sufficiently small (for example, 100 [μm] or less). Further, the magnetization may be carried out directly on the developing roller, or a film-like magnetic field generating layer may be previously magnetized and appropriately disposed on the developing roller by means such as adhesion.

Although the embodiments have been described above, the present invention can be applied not only to the above embodiments but also to a wide range of developing devices such as electrophotography.
It is especially effective when applied to printers, copiers, facsimiles, and displays.

[Effects of the Invention] As described above, according to the present invention, the developing roller has at least a cylindrical thin film member, the thin film member has at least a magnetic field generating layer, and the surface roughness of the developing roller is determined by the magnetic field generating layer. By making the magnetization reversal interval smaller than the minimum magnetization reversal interval and smaller than the volume average particle diameter of the monocomponent magnetic toner, a stable thin layer of the monocomponent magnetic toner can be formed on the developing roller.
The present invention has the advantage that it is possible to stably form high-resolution and high-quality images by maintaining stable conveyance and development conditions, and to provide a compact, low-cost developing device with a simple structure. In addition, by making the toner a thin layer and performing contact development, it is possible to maximize the development electrode effect and form high-resolution images, and the amount of waste toner is reduced by the magnetic binding force of minute pitches. Contamination caused by toner scattering is also reduced, making it possible to reduce running costs in image formation and maintenance of the image forming apparatus.

Therefore, the developing device of the present invention is suitable for one-component magnetic development method.
This has the excellent effect of providing a developing device that can produce high-resolution images with few image defects such as ground blur and trailing.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional overview of an image forming apparatus using a developing device of the invention, and FIG. 2 is a cross-sectional overview of a thin film member in an embodiment of the invention. Process 0 1 2 Latent image carrier developing device Toner developing roller Drive roller Thin film member Magnetic field generating layer and above

Claims (1)

[Claims] (1) One-component magnetic toner is conveyed by a developing roller,
In the developing device for developing the one-component magnetic toner onto a latent image carrier, the developing roller includes at least a cylindrical thin film member and a drive roller that contacts at least a portion of an inner circumferential side surface of the cylindrical thin film member. , the thin film member has at least a magnetic field generating layer, and the surface roughness of the developing roller is smaller than the minimum magnetization reversal interval of the magnetic field generating layer and smaller than the volume average particle diameter of the monocomponent magnetic toner. Characteristic developing device.