JPH03259290A - Developing device - Google Patents

Abstract

PURPOSE:To simplify and miniaturize the structure of a developing roller and to make it inexpensive by using the developing roller having an elastic layer and a magnetic field generation layer and executing developing in a developing area while an alternate electric field is actuated. CONSTITUTION:The developing roller 2 carrying magnetic toner 1 is obtained by disposing the elastic layer 4, which is obtained by dispersing carbon black into a foamed polyurethane rubber, and the magnetic field generation layer 5, which is coated with a magnetic coating material obtained by dispersing gamma-Fe2O3 into binder solution and formed, on the outside circumference of a base body 3 in a concentric circular state. Then, the magnetic toner 1 is directly held by the leakage magnetic flux of the outside circumference of the magnetic field generation layer 5. Besides, the toner 1 of a thin layer is carried by rotat ing the developing roller 2 in a state that the toner 1 is regulated to proper quantity by a plate-like blade 6 constituted of a non-magnetic or magnetic metal or resin. Thus, the structure of the developing roller 2 is simplified and miniaturized. Besides, it is made light in weight and inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device that uses a one-component magnetic toner.

[Prior Art] As shown in Japanese Unexamined Patent Publication No. 63-31776, a conventional developing device uses a developing roller, which is a non-magnetic rotating cylinder with an elastic conductive layer and which houses a fixed or rotatable magnet inside, to produce a single component. The magnetic toner was conveyed and developed by pressing a developing roller against the latent image carrier.

In addition, other conventional developing devices that have been proposed include UPS-
4564285 and Japanese Patent Application Laid-Open No. 59-119371, an insulating layer is formed on a conductive substrate, a plurality of microelectrodes are dotted on the surface of the insulating layer, and either the insulating layer or the microelectrodes is A one-component magnetic toner is conveyed by a magnetic developing roller, and development is performed by bringing the developing roller into contact with or close to a latent image carrier.

[Problems to be Solved by the Invention] However, in the former example of the prior art described above, the developing roller is constituted by a developing sleeve and a magnetic roller, resulting in a complicated structure, large size, and high cost. Furthermore, because this configuration has a low limit for miniaturization of the magnetic pole pitch, it is difficult to form a thin and uniform toner layer, resulting in image quality deterioration such as uneven density and trailing at the edges of line images due to fluctuations in the magnetic field of the magnetic roller. The problem was that there were many factors.

In addition, with the latter conventional technology, it is difficult to form an insulating layer whose surface is dotted with micromagnets, resulting in high costs.
Furthermore, there is a problem in that the magnetic force applied to the toner layer becomes non-uniform, resulting in uneven density. Furthermore, since the toner comes into contact with the latent image carrier, there is a problem in that the toner adheres to the non-image area by mirror image force (ground force blur).

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and an object of the present invention is to provide a developing device suitable for developing one-component magnetic toner. Still another object is to provide a developing device that is simple in structure, small in size, and low in cost. Still another object is to provide a developing device with high resolution and high image quality.

[Means for Solving the Problems] The developing device of the present invention has a developing roller that conveys a one-component magnetic toner and a latent image carrier that are opposed to each other in a developing area with a gap equal to or less than the thickness of the developer layer. , a developing device that develops a one-component magnetic toner while forming an alternating electric field in a developing area, characterized in that the developing roller has at least an elastic layer and a magnetic field generating layer.

Further, the developing device of the present invention has a developing device that presses a developing roller that conveys a one-component magnetic toner against a latent image carrier in a developing region, and develops the one-component magnetic toner while forming an alternating electric field in the developing region. , the developing roller has at least an elastic layer and a magnetic field generating layer.

Further, the developing device of the present invention is characterized in that the developing roller has an insulating layer.

Further, the developing device of the present invention is characterized in that the developing roller has a conductive layer.

[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. However, it is possible to obtain a small, lightweight, and low-cost developing roller. In addition, by magnetizing the thin magnetic field generation layer at a minute pitch, it is possible to form a uniform and thin toner layer (or a thin layer of magnetic brush at a minute pitch) on the developing roller, which prevents fluctuations in the magnetic field. Reduces density unevenness caused by variations in toner layer thickness,
High-resolution development can be performed. Further, according to the above configuration of the present invention, by applying an alternating electric field to the developing area and at the same time applying a uniform magnetic restraining force of the magnetic field generating layer, the effect of scraping the toner back from the latent image carrier to the developing roller ( scavenging effect), thereby reducing ground blurring that occurs significantly when toner comes into contact with a latent image carrier, and further enables high-resolution development.

Furthermore, by providing a conductive layer on the developing roller, a high-resolution image can be obtained due to the developing electrode effect.

Further, by providing an insulating layer on the developing roller, it is possible to stably perform frictional charging between the developing roller and the toner and reduce temporal fluctuations in the developer density.

Further, by optimizing the peak potential and frequency of the developing bias, it is possible to provide a developing device capable of forming an image with gradation or a binary image with contrast.

Hereinafter, the details of the present invention will be shown by examples.

[Example] FIG. 1 is a cross-sectional schematic diagram of an example of the developing device of the present invention. The developing roller 2 that conveys the magnetic toner 1 has an elastic layer 4 made of foamed urethane rubber dispersed in carbon black and a γ-Fe2O3 on the outer periphery of the base 3.
Magnetic field generating layers 5 each having a thickness of about 10 μm and formed by applying a magnetic paint containing dispersed particles in a binder solution are arranged concentrically, and magnetic toner 1 A thin layer of toner 1 is conveyed by rotating the developing roller 2 while directly holding the toner 1 and regulating the appropriate amount with a plate-shaped blade 6 made of non-magnetic or magnetic metal or resin. The toner 1 is transferred to a latent image carrier 9 having an electrostatic image holding layer 8 formed on a supporting electrode 7 and a developing roller 2.
The toner layer is conveyed to a development area arranged with a gap narrower than the layer thickness of the toner 1, and the toner layer comes into contact with the latent image carrier 9. Further, the toner 1 is applied depending on the potential contrast of the latent image carrier 9 and the developing electric field formed between the latent image carrier 9 and the developing roller 2 by the DC developing bias applying means 1o and the AC developing bias applying means 11. The latent image carrier 9
The electrostatic latent image is visualized.

Using a developing device as shown in FIG.
When line latent images, character latent images, and solid latent images of PI] were continuously developed over 10,000 sheets, 600
[DPI] line images are stably formed without line thickening, there is no tailing or blurring at the edges of the image, and high-density solid images with an OD value of 1.4 or higher can be stably formed. did it.

FIG. 2 is a cross-sectional schematic diagram of another embodiment of the developing device of the present invention. Components having substantially the same functions, names, and names as those in FIG.

The developing roller 2 is pressed against the latent image carrier 9 at a predetermined pressure, and the toner 1 on the developing roller 2 is thinned by an elastic blade 26 in the shape of a thin plate spring made of non-magnetic or magnetic metal or resin. When layered and roughly conveyed to the pressure contact section, the potential contrast of the latent image carrier 9, the DC development bias application means 10 and the AC development bias application means 1
Toner 1 charged according to the developing electric field formed by 1
is attached to the latent image carrier 9, and the electrostatic latent image is visualized.

Using a developing device as shown in FIG.
When line latent images, character latent images, and solid latent images of PI] were continuously developed over 10,000 sheets, 600
The [DPI] line image is stably formed without line thickening, there is no trailing or blurring at the edge of the image, and there is no excessive toner development at the edge of the surface image, and the OD
It was possible to stably form a solid image with a high density of 1.4 or higher.

In the embodiments of FIGS. 1 and 2, the elastic layer 4 can be composed of materials such as natural rubber, silicone rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, and the like.

The elastic layer 4 can be made of rubber, foam, sponge, etc., and preferably has a thickness of 500 μm or more. It is formed by dispersing known magnetic powder together with additives in a binder solution and applying a magnetic paint. Furthermore, 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. 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 FIGS. 1 and 2, the present invention is not limited to the configurations shown in the figures, and although the arrows indicate the rotation directions of the respective members, the present invention is not limited to the configurations shown in the figures. The latent image carrier 9 can also be in the form of a bell, and the developing method can be used regardless of whether it is regular development or reversal development.

FIG. 3 is a diagram showing the layer structure of a developing roller in an embodiment of the present invention, in which an elastic layer 32 mainly composed of an elastic resin is formed on a base 31 such as a shaft, and 3 layers are formed on an elastic layer 32.
A four-conductor layer 33 is formed, a magnetic field generating layer 34 is formed on the conductive layer 33, and an insulating layer is further formed on the magnetic field generating layer 34! Iti35 was formed to serve as a developing roller. Magnetic field generation 83
By magnetizing the toner 4 in the horizontal direction so that the magnetization reversal pitch is 100 [μm] or less, a minute toner chain of the magnetic toner 1 is formed on the insulating layer 35, resulting in a thin and stable toner layer. It will be done. In addition, by magnetizing the magnetic field generation layer 34 in the perpendicular direction (not shown), the magnetization reversal pitch can be made denser to about the toner particle size (approximately 10 [μm1]), and can be uniformly formed in one or two layers. It is also possible to form a thin layer of toner, and since a strong magnetic field can be obtained on the surface of the magnetic field generation layer, it is possible to reduce the magnetic powder content of toner 1, making it easier to manufacture the toner and improving fixing properties. . Note that the arrows in the figure indicate the direction of magnetization, and the direction of the conductive layer 3
As the material of 3, in addition to materials containing conductive metals such as A1 and Ni, conductive materials such as carbon black can be used, and it can be formed by means such as adhesion, coating, plating, etc. Further, only when the magnetic field generating layer 34 is vertically magnetized, a large magnetic field can be obtained on the surface of the insulating layer 35 by providing a magnetic circuit of the magnetic field generating layer 34 with a configuration in which the conductive layer 33 includes a soft magnetic material. be able to. Furthermore, by providing the insulating layer 35 at the contact portion with the toner 1, not only can the charging polarity and the amount of charge of the toner 1 be controlled, but also a resin having excellent abrasion resistance such as fluorocarbon resin can be used in the insulating layer 35. It can also be used as a protective layer for the magnetic field generation layer 34.

Although examples of the layer structure have been described above, the developing roller in the developing device of the present invention has at least an elastic layer and a magnetic field generating layer, and either the elastic layer or the magnetic field generating layer has conductivity or is an independent conductive layer. In addition, it is possible to add a base body that ensures the strength of the roller and an insulating layer that improves the charging property of the toner as other constituent elements. In addition, a protective layer can be provided to improve durability, an intermediate layer can be provided to improve moldability, and it is also possible to combine the functions of multiple layers into a single layer. It is. Furthermore, the magnetic field generation layer 34 can be used in various magnetized states such as line magnetization, grid magnetization, and spiral magnetization. Alternatively, a magnetic field generating layer in the form of a film that has been magnetized in advance may be appropriately disposed on the developing roller by means such as adhesion.

FIG. 4 is a diagram showing the amount of developed toner in an example in which the developing device of the present invention was used and the developing bias conditions were changed.

The horizontal axis represents the contrast potential V, which is the difference between the potential of the image area and the potential of the developing roller due to the DC developing bias, and the vertical axis represents the developed toner jID of the image formed on the latent image carrier, and the curve in the figure is the V-D characteristic. In FIG. 4, the difference between the peak and bottom of the alternating current component of the developing bias (VpI) is used as a parameter, and it shows that the slope of the V-D characteristic tends to become steeper when 1Vppl is increased. Therefore, as a developing device suitable for copying machines etc. that require good gradation, ! v
It is desirable that pp1≧300 [V], and
For a developing device such as a laser beam printer where the density of each pixel is binary and it is desirable that the stable range of each binary density is wide, it is desirable that 100≦1Vppl≦600 [V] be satisfied.

FIG. 5 is a diagram showing the amount of developed toner in an example in which the developing device of the present invention was used and other developing bias conditions were changed. The horizontal axis is the contrast potential ■, which is the difference between the potential of the image area and the potential of the developing roller due to the DC developing bias, and the vertical axis is the developing toner JID of the image formed on the latent image carrier.
The curve in the figure is the V-D characteristic. FIG. 5 uses the frequency f of the AC component of the developing bias as a parameter, and shows that the slope of the V-D characteristic tends to become steeper as f becomes larger. Therefore, it is desirable that f≦1200 [Hzl] for a developing device suitable for a copying machine or the like that requires good gradation. In addition, a developing device suitable for a laser beam printer, etc., in which the density of each pixel is binary, and it is desirable that the stable region of each binary density is wide, is suitable for f≧600.
[Preferably Hzl.

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, a developing roller having at least an elastic layer and a magnetic field generating layer is used, and development is performed while applying an alternating electric field in the developing area, thereby achieving a simple structure, small size, and low cost. It is possible to provide a low-cost developing device, and has the effect of stably forming high-resolution, high-quality images. Further, it has the effect that ground force blur, which occurs noticeably when toner comes into contact with the latent image carrier, can be prevented by the magnetic binding force generated by alternating electric fields and minute pitch magnetic fields.

Furthermore, by stably supplying a thin layer of toner to the development area using a magnetic binding force similar to -, it is possible to provide a developing device that is compatible with both contact development and pressure development, and in particular uses pressure development. It is possible to maximize the development electrode effect and form the highest resolution image. Furthermore, since contact development is performed by supplying toner in a thin layer to the development area, the effect of alternating electrolysis can be obtained even if the voltage of the AC component of the development bias is lower than in conventional technology, making it possible to reduce the size and cost of the power supply. It has the effect of being. Furthermore, by providing a conductive layer or an insulating layer, it is possible to improve the developing electrode effect and durability.

Therefore, the developing device of the present invention has an excellent effect in that it can provide a developing device that can obtain high-resolution images with few image defects such as ground blur and trailing in one-component magnetic development. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional overview of an embodiment of the developing device of the present invention, FIG. 2 is a cross-sectional overview of another example of the developing device of the present invention, and FIG. 3 is a cross-sectional overview of an embodiment of the developing device of the present invention. FIG. 4 is a diagram showing the layer structure of a developing roller in an example, FIG. 4 is a diagram showing the amount of developed toner in an example in which the developing device of the present invention was used and the conditions of the developing bias were changed, and FIG. FIG. 7 is a diagram showing the amount of developed toner in an example in which the developing device of the present invention was used and other developing bias conditions were changed. 1: Toner 2: Developing roller 4: Elastic layer 5: Magnetic field generating layer 9: Latent image carrier 10: DC developing bias applying means 11: AC developing bias applying means 33: Conductive layer 35: Insulating layer or above

Claims (4)

[Claims] (1) A developing roller that conveys one-component magnetic toner and a latent image carrier are held facing each other in a developing area with a gap equal to or less than the thickness of the developer layer, and while an alternating electric field is formed in the developing area, the one-component magnetic toner is A developing device for developing magnetic toner, wherein the developing roller has at least an elastic layer and a magnetic field generating layer. (2) A developing device which presses a developing roller that conveys the one-component magnetic toner against a latent image carrier in a developing region and develops the one-component magnetic toner while forming an alternating electric field in the developing region, the developing device comprising: A developing device characterized in that the roller has at least an elastic layer and a magnetic field generating layer. (3) The developing device according to claim 1 or 2, wherein the developing roller has an insulating layer. (4) The developing device according to claim 1, 2 or 3, wherein the developing roller has a conductive layer.