JPH04142576A - Developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a developing device using magnetic toner, and more particularly to a developing device that conveys and develops the magnetic toner by a developing roller having an elastic layer and a magnetic field generating layer. [Prior Art] As disclosed in USP-4121931, a conventional developing device uses a developing roller having a magnetic roller inside a non-magnetic cylindrical sleeve to form a magnetic brush of magnetic toner on the sleeve. , which transports and develops magnetic toner, and is known as a component magnetic brush development method. In addition, as a development method that improves the above-mentioned one-component magnetic brush development method, there is a FEED development method that improves the image quality of line images and solid images by providing a floating electrode on the developing roller as disclosed in USP-4564285, and a FEED development method that improves the image quality of line images and solid images.
A developing device has been proposed, as disclosed in Japanese Patent No. 4,851,874, which conveys a thin layer of toner on the surface of a magnetic roller and develops it on a belt-shaped latent image carrier. [Problems to be Solved by the Invention] However, in the one-component magnetic brush development method and the FEED development method among the above-mentioned conventional technologies, the developing roller is composed of a developing sleeve and a magnetic roller, and the structure is complicated, large, and costly. The problem is that there are many causes of image quality deterioration, such as density unevenness and trailing at the edges of the image due to fluctuations in the magnetic field of the magnet roller. In addition, even in the developing method, in which toner is transported and developed in a thin layer on the surface of a magnetic roller, image quality deterioration occurs similarly due to fluctuations in the magnetic field of the magnetic roller, and the device is large due to the use of a belt-shaped latent image carrier. It had the problem of becoming 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 magnetic toner. Yet another purpose is
The purpose is to provide a small, low-cost developing device with a simple structure. 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 in which a developing roller conveys magnetic toner and develops the magnetic toner onto a latent image carrier, in which the developing roller has an elastic layer, a magnetic field generating layer, and a non-magnetic layer. It is characterized by having at least a magnetic layer. Further, the developing device of the present invention is characterized in that the developing roller is brought into pressure contact with the latent image carrier. Further, the developing device of the present invention is characterized in that the gap between the developing roller and the latent image carrier is larger than the layer thickness of the magnetic toner on the developing roller. Furthermore, the developing device of the present invention is characterized in that the developing roller has a conductive layer. Furthermore, the developing device of the present invention is characterized in that the developing roller has an insulating 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 as a single rotating body. However, it is possible to obtain a small, lightweight, and low-cost developing roller. In addition, by appropriately arranging the magnetic field generating layer and the non-magnetic layer, when the magnetic field generating layer is magnetized, the magnetizing magnetic flux concentrates on the magnetic field generating layer, making magnetization easy. Since the leakage magnetic flux can be concentrated on the toner layer, the magnetic force can be effectively used for conveying or restraining the toner. 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. It is possible to reduce density unevenness caused by variations in toner layer thickness and perform high-resolution development. Further, according to the above configuration of the present invention, regardless of whether contact development or non-contact development is performed, a uniform and thin toner layer is formed on the developing roller, and the variation in the toner layer thickness on the developing roller is prevented. Temperature fluctuations can be reduced. Furthermore, by providing a conductive layer on the developing roller, a high-resolution image can be obtained due to the developing electrode effect. Furthermore, by providing an insulating layer on the developing roller, it is possible to stably perform frictional charging between the developing roller and the toner, thereby reducing temporal fluctuations in the developed density. Hereinafter, the present invention will be explained in detail with reference to Examples. [Example 1] FIG. 1 is a cross-sectional schematic view of an image forming apparatus using the developing device of the present invention. The latent image carrier 1 has a photosensitive layer 3 coated with an organic or inorganic photoconductive material on a conductive support 2, and the photosensitive layer 3 is coated with a corona charger or a charging roller. After charging using a charger 4 such as a laser or LED, light emitted from a light source 5 such as a laser or LED is selectively irradiated onto the photosensitive layer 3 according to the image through an imaging optical system 6 to obtain a potential contrast. Forms an electrostatic latent image. On the other hand, the developing device 7
1 conveys and develops magnetic toner 8, and the developing roller 9 that conveys the toner 8 has a non-magnetic elastic layer 1 and a magnetic field generating layer 12 arranged concentrically around the outer periphery of a shaft 0. 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 12,
A thin layer of toner 8 is conveyed by rotating a developing roller 9 while controlling the amount appropriately with a plate-shaped blade 13 made of non-magnetic or magnetic metal or resin. When the toner 8 is conveyed to the development gap where the latent image carrier 1 and the developing roller 9 are close to each other, a developing electric field is formed by the potential contrast of the latent image carrier 1 and the development bias applying means 14.
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 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. 1st
Using an image forming apparatus as shown in the figure, 600 [
When line images, character images, and solid images of [DPI] were continuously formed on 10,000 sheets, the result was 600 [DPI].
DPI] line image is stably formed without line thickening, there is no tailing or blurring at the edge of the image, and the OD value is 1.
．． A solid image with a high density of 4 or higher can be stably formed, and there is no ground force blur on the recording paper as well as on the latent image carrier, and the amount of waste toner can be significantly reduced. Ta. FIG. 2 is a cross-sectional schematic diagram of an image forming apparatus using a developing device according to another embodiment of the present invention, in which members having substantially the same functions, functions, and names as those in FIG. 1 are given the same numbers and explained. omitted. The developing device 21 conveys and develops the magnetic toner 8, and the developing roller 9 that conveys the toner 8 holds the magnetic toner 8 directly on the developing roller 9 by leakage magnetic flux around the outer periphery of the magnetic field generating layer 11. The toner 8 is then thinned to an appropriate amount using a thin plate spring-like elastic blade 22 made of non-magnetic or magnetic metal or resin, and the developing roller 9 is rotated to form a thin layer of toner 8.
It is used to transport. 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. Charged according to the developing electric field

[7] The toner 8 adheres to the latent image carrier 1, and the electrostatic latent image is visualized. When we continuously formed 10,000 sheets of 600 [DPI] line images, character images, and solid images using the image forming apparatus shown in Figure 2, the 600 [DPI] line images did not become thick. It is stably formed and has the highest resolution of the line-bearing image, and there is no tailing or blurring at the edge of the image, and it is possible to stably form a high-density solid image with an OD value of 1.4 or more. Not only was there no ground force blur on the latent image carrier, but there was also no ground force blur on the latent image carrier, making it possible to significantly reduce the amount of waste toner. FIG. 3 t is a cross-sectional schematic view of an image forming apparatus using a developing device according to still another embodiment of the present invention, in which members having substantially the same functions and names as those in FIG. 1 are given the same numbers. The explanation will be omitted. The developing device 31 conveys and develops the magnetic toner 8, and the developing roller 9 conveys the toner 8.
A blade 3 made of non-magnetic or magnetic metal or resin suspended by a spring or the like holds the magnetic toner 8 directly on the developing roller 9 by leakage magnetic flux on the outer periphery of the magnetic field generation layer 12.
The toner 2 is brought into pressure contact with a developing roller 9 to form a thin layer to an appropriate thickness, and the developing roller 9 is rotated to convey the thin layer of toner 8. The developing roller 9 is disposed on the latent image carrier 1 with a predetermined gap (a gap having a length larger than the layer thickness of the toner 8 on the developing roller 9). When the toner 8 is conveyed to the development gap portion where the two are close to each other, the toner 8 charged according to the potential contrast of the latent image carrier 1 and the developing electric field by the developing bias applying means 14 is transferred to the latent image carrier 1 and becomes static. The latent image is visualized. Using an image forming apparatus as shown in FIG.
When line images, character images, and solid images of 0 [DPI] were continuously formed on 10,000 sheets, 30
A line image of 0 [DPI] is stably formed without line thickening, and there is no tailing or blurring at the edge of the image, and the O
A high-temperature solid image with a D value of 1.4 or more can be stably formed, and there is no ground force blur on the recording paper as well as on the latent image carrier, greatly reducing the amount of waste toner. We were able to. 1 to 3, the non-magnetic elastic layer 11 includes natural rubber, silicone rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, isoprene rubber, N
Using BR etc., the form of the elastic layer is rubber, foam,
It is used in the form of a sponge, etc., and the layer thickness of the non-magnetic elastic layer 11 varies depending on the developing method and the method of regulating the amount of toner conveyance, but it is preferably 500 μm or more in order to obtain sufficient elastic displacement. For the magnetic field generation layer 12, known magnetic recording materials and magnet materials can be used, and more specifically, Fe, Ni, Co, and Mn. Magnetic materials containing at least one element among Cr, such as 7-Fe2O3, Ba-Fe, Ni-Co,
Go-Cr, Mn--A1, etc. can be used, and the film thickness is 10
The toner is thinned to 0 [μm] or less, preferably around 10 [μm], and the minimum magnetization reversal pitch is 10o [μm] or less to make the toner a uniformly thin layer. At the same time, the amount of toner conveyed on the developing roller is varied by magnetic brush formation. It is possible to reduce temperature unevenness by suppressing the pitch to a minute pitch. Moreover, the magnetic field generation layer 1
Since the lower layer of 2 is the non-magnetic elastic layer 11, the magnetic flux can be concentrated in the magnetic field generating layer 12 when the magnetic field generating layer 12 is magnetized, so that magnetization is easy. Further, as the toner used in the present invention, all toners known as magnetic toners can be used, including resin-based toners and wax-based toners. As is well known, the composition of the developer is a mixture of resin, magnetic powder, colorant, external additives, and other additives, and is produced by a pulverization method, a polymerization method, or the like. In addition, in FIGS. 1 to 3, the present invention is not limited only to the configurations shown in the figures, and although the arrows indicate the rotation direction of each member, they are not intended to limit the present invention.
Furthermore, the developing method can be used regardless of whether it is regular development or reversal development. FIG. 4 to FIG. 9 are diagrams showing the layer structure of the developing roller in the embodiment of the present invention. FIG. 4 is a diagram showing the layer structure of a developing roller in an embodiment of the present invention, in which a non-magnetic elastic layer 42 mainly composed of a non-magnetic elastic resin is formed on a base 41 such as a shaft. A magnetic field generating layer 43 is formed on the elastic layer 42 to serve as a developing roller. By forming the magnetic field generation layer 43 so that the layer thickness d is 100 [μm] or less, preferably 10 [μm], and magnetizing it in the horizontal direction so that the magnetization reversal pitch p becomes 100 [μm] or less, A minute toner chain is formed by the toner 44 on the magnetic field generating layer 43, resulting in a thin and stable toner layer. When the nonmagnetic elastic layer 42 is made of a magnetic material, the magnetic flux generated in the magnetic field generation layer 43 is transferred to the nonmagnetic elastic layer 4.
However, in the present invention, the nonmagnetic elastic layer 42
Since it is non-magnetic, most of the magnetic flux penetrates the toner layer, allowing effective use of magnetic force. Furthermore, by dispersing a non-magnetic conductive material such as carbon black in an elastic resin to form the non-magnetic elastic layer 42, a developing bias voltage can be applied to the non-magnetic elastic layer 42 to improve the developing electrode effect. High resolution images can be obtained. Note that the arrow in the figure indicates the direction of magnetization. FIG. 5 is a diagram showing the layer structure of a developing roller in another embodiment of the present invention, in which an elastic layer 52 made of foamable resin is formed on a base 51 such as a shaft, and a non-magnetic layer is formed on the elastic layer 52. A conductive layer 53 is formed, and a magnetic field generating layer 54 is formed on the nonmagnetic conductive layer 53 to form a developing roller. When the nonmagnetic conductive layer 53 is thin, it is desirable that the elastic layer 52 is also nonmagnetic in order to concentrate the magnetic flux on the toner layer.
The magnetic field generation layer 54 is formed so that the layer thickness d is 100 [μm] or less, preferably 10 [μm], and is horizontally magnetized so that the magnetization reversal pitch is 100 [μm] or less. A minute toner chain is formed by the toner 55 on the generation layer 54, resulting in a thin and stable toner layer. Therefore, the developing bias voltage is applied to the nonmagnetic conductive layer 5.
The material of the non-magnetic conductive layer 53, which can improve the developing electrode effect and obtain a high-resolution image by applying a voltage of In addition to materials containing metal, a nonmagnetic conductive material such as carbon black can be used, and the nonmagnetic conductive layer 53 can be formed by means such as adhesion, coating, plating, or the like. Note that the arrow in the figure indicates the direction of magnetization. FIG. 6 is a diagram showing the layer structure of a developing roller in still another embodiment of the present invention, in which a non-magnetic elastic M62 made of a non-magnetic sponge or the like is formed on a base 61 such as a shaft, and a non-magnetic elastic layer A magnetic field generating layer 63 is formed on the magnetic field generating layer 62, and a non-magnetic conductive layer 64 is formed on the magnetic field generating layer 63 to form a developing roller. Since the non-magnetic conductive layer 64 is non-magnetic, the magnetic circuit will not be short-terminated within the non-magnetic conductive layer 64. By magnetizing the magnetic field generation layer 63 with a fine magnetization reversal pitch in the horizontal direction, A minute toner chain is formed by the toner 65, and a thin and stable toner layer is obtained. Therefore, by applying a developing bias voltage to the non-magnetic conductive layer 1i64, it is possible to improve the developing electrode effect and obtain a high-resolution image. Then, the nonmagnetic conductive layer 64 functions as a protective film for the magnetic field generation layer 63, and the life of the developing roller can be extended. Note that the arrow in the figure indicates the direction of magnetization. FIG. 7 is a diagram showing the layer structure of a developing roller in still another embodiment of the present invention, in which a non-magnetic elastic layer 72 mainly composed of a non-magnetic elastic resin is formed on a base 71 such as a shaft. , a magnetic field generating layer 73 is formed on a non-magnetic elastic layer 72, and a non-magnetic insulating layer 74 is formed on the magnetic field generating layer 73 to form a developing roller. As in the previous embodiment, a minute toner chain is formed by the toner 75 on the magnetic field generating layer 73, resulting in a thin and stable toner layer. By providing the non-magnetic insulating layer 74 in the contact area with the toner 75, it is possible not only to control the charging polarity and the amount of charge of the toner 75, but also to use a resin with excellent wear resistance such as fluorocarbon resin as the non-magnetic insulating layer. By using it in 74, it can also be used as a protective layer for the magnetic field generation layer 73. Note that the arrow in the figure indicates the direction of magnetization. FIG. 8 is a diagram showing the layer structure of a developing roller in still another embodiment of the present invention, in which a base 8 such as a shaft, a non-magnetic elastic layer 82 mainly composed of a non-magnetic elastic resin is formed on the base 8]. forming a magnetic field generating layer 83 on the nonmagnetic elastic layer 82;
A non-magnetic conductive layer 84 is formed on the magnetic field generating layer 83 7, and a non-magnetic insulating layer 85 is formed on the non-magnetic conductive layer 84 to form a developing roller. As in the previous embodiment, a minute toner chain is formed by the toner 86 on the magnetic field generating layer 83, resulting in a thin and stable toner layer. Therefore, it is possible to obtain a high-resolution image by applying a developing bias voltage to the non-magnetic conductive layer 84 to counteract the developing electrode effect, and to provide the non-magnetic insulating layer 85 in the contact area with the toner 86. This not only makes it possible to control the charging polarity and the amount of charge of the toner 86, but also makes it possible to control the non-magnetic conductive layer 84 by using a resin with excellent abrasion resistance such as fluorocarbon resin for the non-magnetic insulating layer 85.
functions as a protective layer to maintain stable development electrode effects. Note that the arrows in the figure indicate the direction of magnetization. FIG. 9 is a diagram showing the layer structure of a developing roller in still another embodiment of the present invention, in which an elastic layer 92 mainly composed of elastic resin is formed on a base 91 such as a shaft, and the elastic layer 92 is
A nonmagnetic conductive layer 93 is formed thereon, a magnetic field generating layer 94 is formed on the nonmagnetic conductive layer 93, and a nonmagnetic insulating layer 95 is formed on the magnetic field generating layer 94 to form a developing roller. When the non-magnetic conductive layer 93 is thin, it is desirable that the elastic layer 92 is also non-magnetic in order to concentrate the magnetic flux on the toner.Similar to the previous embodiment, the toner 96 is placed on the magnetic field generation layer 04.
, a fine toner chain is formed and a thin and stable toner layer is obtained. Therefore, by applying a developing bias voltage to the non-magnetic conductive layer 93, it is possible to improve the developing electrode effect and obtain a high-resolution image.
By providing the non-magnetic insulating layer 95 in the contact area with the non-magnetic insulating layer 95, it is possible to control the charge polarity and the amount of charge of the toner 96, as well as use a resin with excellent wear resistance such as fluorocarbon resin for the non-magnetic insulating layer 95. A stable toner layer can be maintained as a protective layer of 94. Note that the arrow in the figure indicates the direction of magnetization. In addition to the above examples of layer configurations, stacked layer configurations are possible, such as a configuration in which the functions of multiple layers are combined into a single layer, and a layer configuration in which an intermediate layer is provided between each layer to facilitate interlayer bonding. It is also possible to provide a structure in which the developing electrode effect is improved by arranging it in a predetermined layer. Further, in the present invention, the magnetic field generation layer is formed with a magnetization reversal pitch p
By magnetizing the toner so that it is sufficiently small (for example, 100 [μm] or less), a stable thin toner layer is formed on the developing roller, and it does not particularly depend on the magnetization state. In order to perform magnetism, the layer thickness d of the magnetic field generation layer is preferably 100 [μm] or less, preferably around 10 [μm]. Further, the magnetization may be carried out directly on the developing roller, or a magnetic field generating layer on the film may be previously magnetized and then properly placed 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 structure is simple, magnetization is easy, and the magnetic force is It is possible to provide a small, low-cost developing device with high utilization efficiency, and it has the effect of stably forming high-resolution, high-quality images. In addition, we can provide a developing device that can handle any of contact development, pressure development, and non-contact development.In particular, when pressure development is used, it is possible to maximize the development electrode effect and form the highest resolution image. can. 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 the magnetic toner developing method.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus using a developing device of the present invention, FIG. 2 is a cross-sectional schematic diagram of an image forming device using a developing device according to another embodiment of the present invention, and FIG. A schematic cross-sectional view of an image forming apparatus using a developing device according to another embodiment of the invention, FIG. 4 is a diagram showing the layer structure of a developing roller in an embodiment of the invention, and FIG. 5 is a diagram showing another embodiment of the invention. FIG. 6 is a diagram showing the layer structure of the developing roller in still another embodiment of the present invention,
FIG. 7 is a diagram showing the layer structure of the developing roller in still another embodiment of the present invention, FIG. 8 is a diagram showing the layer structure of the developing roller in still another embodiment of the present invention, and FIG. 9 is a diagram showing the layer structure of the developing roller in still another embodiment of the present invention. FIG. 7 is a diagram showing a layer structure of a developing roller in still another embodiment. 1...Latent image carrier 7...Developing device Toner developing roller Non-magnetic elastic layer Magnetic field generating layer and above

Claims (5)

[Claims] (1) A developing device that conveys magnetic toner by a developing roller and develops the magnetic toner on a latent image carrier, wherein the developing roller has at least an elastic layer, a magnetic field generating layer, and a nonmagnetic layer. Device. (2) The developing device according to claim 1, wherein the developing roller is brought into pressure contact with the latent image carrier. (3) The developing device according to claim 1, wherein the gap between the developing roller and the latent image carrier is larger than the layer thickness of the magnetic toner on the developing roller. (4) The developing device according to claim 1, wherein the developing roller has a conductive layer. (5) The developing device according to claim 1, 2, 3, or 4, wherein the developing roller has an insulating layer.