JPH04181970A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a developing device capable of press-contact development without damaging a latent image carrier at a low cost by disposing a magnetic field generating layer obtained by dispersing magnetic powder in binder on an elastic layer. CONSTITUTION:A developing roller 9 carrying toner 8 is constituted by forming the elastic layer 11 on the outer periphery of a shaft 10 and further concentrically disposing a magnetic field generating layer 12 having electric conductivity, which is obtained by dispersing the magnetic powder, on the outer periphery of the layer 11. The layer 12 is a sleeve obtained by dispersing the magnetic powder 21 in the binder, and rubber material such as natural rubber, silicone rubber, and isoprene rubber or elastomer such as polyurethane or polyester, etc., can be used as the binder 22, and the magnetic powder known as a magnetic recording material and a magnet material is used as the magnetic powder 21. Thus, the electric conductivity and the magnetic characteristic of the layer 12 are appropriately set for development, and the development is performed without damaging the latent image carrier even when a toner carrier press- contacts with the latent image carrier whose rigidity is high so as to perform the development.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device that develops magnetic toner, and more particularly to a developing device that is characterized by a toner carrier that conveys the magnetic toner.

[Prior Art] A conventional developing device using magnetic toner is disclosed in Japanese Patent Application Laid-Open No. 1986-
42738, the toner carrier is formed of a conductive rubber magnet to ensure a sufficient amount of toner conveyance for development and to reduce the contact pressure between the toner carrier and the latent image carrier. The development was carried out under pressure.

In addition, as a method for performing pressure development by relaxing the contact pressure between the toner and the latent image carrier, as disclosed in Japanese Patent Laid-Open No. 63-226676, a cylindrical thin film having an excess circumference with respect to the drive roller is used. A toner carrier is configured by the member sleeve,
Some have made it possible to convey and develop non-magnetic toner by elastically bringing the surplus portion into close contact with the latent image carrier.

[Problems to be Solved by the Invention] However, in the prior art described above, carbon or the like is mixed into the rubber in order to impart conductivity to the rubber magnet.
If you want to obtain a conductivity below [Ωan], the rubber hardness should be 4
It is difficult to reduce the angle to less than 5 degrees, and if a hard rubber magnet is pressed against the latent image carrier, the toner will solidify at the pressure contact area between the toner carrier and the latent image carrier, and not only will a good image not be obtained, but the latent image carrier will not be able to obtain a good image. There is a problem in that the image carrier is worn out.

In addition, in the above-mentioned conventional technology, the thin film member and the drive roller are not fixed, so it is necessary to handle the thin film member as a single unit during assembly. When assembled, the thin film member is deformed, resulting in a decrease in cylindricity, which causes uneven toner conveyance.

Therefore, the present invention aims to solve these problems.
The purpose is to provide a developing device that can perform pressure development without damaging the latent image carrier at a low cost.

Still another object is to provide a developing device whose toner carrier is easy to handle during assembly and which is easy to assemble.

Still another object is to provide a developing device suitable for performing high-resolution development using magnetic toner.

[Means for Solving the Problems] The developing device of the present invention is a developing device that conveys magnetic toner by a toner carrier and develops the magnetic toner on the latent image carrier, wherein the toner carrier is elastic or flexible. The magnetic field generating layer is characterized in that the magnetic field generating layer is made of a sleeve in which magnetic powder is dispersed in rubber or elastomer.

Further, the developing device of the present invention is characterized in that the minimum magnetization reversal pitch of the magnetic field generation layer is 100 [μm] or less.

[Function] According to the above structure of the present invention, by disposing the magnetic field generating layer on the elastic layer, the conductivity and magnetic properties of the magnetic field generating layer can be set suitably for development, and a latent image with high rigidity can be formed. Even when the toner carrier is pressed against the carrier, development can be performed without damaging the latent image carrier.

In addition, by constructing the magnetic field generating layer with a sleeve in which magnetic powder is dispersed in rubber or elastomer, damage to the magnetic field generating layer during assembly can be reduced, and it can be bonded using the elasticity of rubber and M vibration force. Since the magnetic field generating layer can be applied to the elastic layer without a layer, the number of assembly steps can be reduced.

Furthermore, since pressure-contact development can be performed, there is no need to manage the development gap between the toner carrier and the latent image carrier, and high-speed printing is possible because the contact width (width of the lubricant) is expanded.

Furthermore, by providing the magnetic field generation layer on the surface of the toner carrier, leakage magnetic flux from the magnetic material can be effectively used for toner retention, and sufficient toner retention force and conveyance amount can be obtained by making the magnetic field generation layer thinner. Can be layered.

Furthermore, the minimum magnetization reversal pitch of the magnetic field generation layer was set to 100 [μ
m] or less, it is possible to form a uniform and thin toner layer (or a thin magnetic brush layer with a minute pitch) on the toner carrier, and it is possible to form a uniform and thin toner layer (or a thin magnetic brush layer with a fine pitch) on the toner carrier, and it is possible to prevent uneven soaking due to fluctuations in the magnetic field and fluctuations in the toner layer thickness. can be reduced.

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 an organic or inorganic photoconductive photosensitive layer 3 coated on a conductive support 2, and the photosensitive layer 3 is charged with a corona charger, a charging roller, etc. After charging using device 4, use a laser or LE
Light emitted from a light source 5 such as D 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 W7 conveys and develops the magnetic toner 8, and the developing roller 9 that conveys the toner 8 has an elastic layer 1 on the outer periphery of the shaft 10.
1, and conductive magnetic field generating layers 12 with magnetic powder dispersed around the outer periphery thereof are arranged concentrically, and the magnetic toner 8 is transferred onto the developing roller 9 by leakage magnetic flux from the outer periphery of the magnetic field generating layers 12. 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 in an appropriately thin layer state.

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 part, it is formed by the potential contrast of the latent image carrier 1 and the developing bias applying means 14. The electrostatic latent image is adhered to the latent image carrier 1 according to the developing electric field applied thereto, and the electrostatic latent image is visualized. moreover,
A toner image is transferred onto a 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. .

FIG. 2 is a more detailed sectional view of the developing roller 9 in an embodiment of the present invention, in which the magnetic field generating layer 12 disposed on the elastic layer 11 has magnetic powder 21 dispersed in a binder 22. It is a sleeve, and its layer thickness is preferably 1 mm or less, preferably 0 mm, since the hardness of the magnetic field generation layer increases when magnetic powder is dispersed to impart magnetic properties or conductivity.
5 [mm] or less, and the binder 22 is made of rubber materials such as natural rubber, silicone rubber, isoprene rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, polyurethane-based, polyester-based, polyamide-based, olefin-based, etc. Styrene-based, nitrile-based, vinyl chloride-based elastomers can be used, and magnetic powder 21
As a magnetic recording material or a magnet material, a known magnetic powder can be used, and more specifically, Fe, Ni,
Magnetic materials containing at least one element among Co, Mn, and Cr, such as 7-Fe2O3, Ba-
Fe, Ni-Co, Co-Cr, Mn-Al, etc. can be used, and the elastic layer 11 can be made of natural rubber, silicone rubber, isoprene rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, etc. rubber,
Elastic deformation of all resins and elastomers that can be used in the form of foams, sponges, etc., and can also be formed into elastic foams such as styrene resin, vinyl chloride resin, polyurethane resin, polyethylene resin, methacrylic resin, etc. Resins can be used that have a large amount and have a short recovery time to their original state.

Using an image forming apparatus as shown in FIG.
When line images, character images, and solid images of [DPI] were continuously formed on 10,000 sheets, the line images of 600 [DPI] became thick due to the development electrode effect because the developing roller and the latent image carrier were in close proximity. The image is formed stably without any tailing at the edge of the image.
In addition, since a sufficient amount of toner for development was conveyed by the magnetic field generation layer, it was possible to stably form a high-temperature solid image with no ground force blur and an OD value of 1.4 or more.

In addition, magnetic powder and conductive particles are dispersed in the magnetic field generating layer to provide sufficient toner holding power and conductivity for development, so even though the hardness of the magnetic field generating layer has increased, the magnetic field generating layer is retained. The elastic layer can effectively disperse and relieve the contact pressure between the magnetic field generating layer and the latent image carrier, and the nip width can be made wider, making it possible to perform high-speed printing.

Furthermore, the minimum magnetization reversal pitch of the magnetic field generation layer was set to 100 [μ
m] or less, the leakage magnetic flux that attracts the magnetic toner is limited to about several tens [μm] from the surface of the magnetic field generation layer, and at the same time, the toner is made into a uniformly thin layer, and at the same time, the amount of toner conveyed on the developing roller by forming a magnetic brush is reduced. It was possible to suppress the fluctuation to a minute pitch and eliminate density unevenness.

FIG. 3 is an explanatory diagram of a method of manufacturing the developing roller 9 in an embodiment of the present invention, and members having the same functions and names as those in FIG. 1 are given the same numbers and explanations are omitted. . In FIG. 3, the magnetic field generating layer 12 is made of isoprene rubber with an internal diameter of 18 [mm] and a thickness of 0.5 [mm] and has a conductivity of 105 [Ωan], and the elastic layer 11 is formed on the outer periphery of the shaft 10. Compression molded silicone rubber with a rubber hardness of 20 degrees to an outer diameter of 19 mm.
], the magnetic field generation layer 12 is attracted and expanded in the radial direction, and the elastic layer 11 is inserted with the inner diameter being equal to or larger than the outer diameter of the elastic layer, and then the attraction force is removed to generate a magnetic field. Since the tensile force in the circumferential direction of the layer generates a contractile force in the radial direction, it is possible to fix the magnetic field generation layer to the elastic layer using only frictional force without using adhesives, without causing slippage between the two. I was able to perform pressure development.

4-a and 4-b are explanatory diagrams of a method of manufacturing the developing roller 9 in another embodiment of the present invention, and the members having the same functions and names as those in FIG. The same numbers will be given and the explanation will be omitted. In Figure 4-a, the magnetic field generation layer 12 is lO
Inner diameter 18 [mm] with conductivity of 5 [Ωan], thickness 0
．． It is a thermoplastic elastomer with a thickness of 2 [mm], and the elastic layer 1
1 is a polyurethane foam formed around the outer periphery of a shaft 10 with an outer diameter of 19 [mm], and a sleeve 31
is a cylinder made of Ni and has an outer diameter of 17 [mm] and a thickness of 200 [μm], and the elastic layer 11 formed on the shaft is first inserted into the sleeve 31, and then the sleeve 31 is fitted. The sleeve 31 is inserted into the magnetic field generating layer 12 in the compressed state, and finally, as shown in FIG. Because of this, it is possible to fix the magnetic field generating layer to the elastic layer using only frictional force without using adhesives, etc., and pressure development can be performed without slippage between the two, as well as improving the manufacturing process of the toner carrier. There were no defective products caused by handling of the magnetic field generating layer.

In addition to the developing roller manufacturing method described above, there are various methods such as inserting the shaft into the sleeve-shaped magnetic field generating layer in advance, and melting and filling an elastic material such as silicone rubber between the magnetic field generating layer and the shaft. Any method is possible, and it may be manufactured by any method.

Furthermore, the method for disposing the magnetic field generation layer on the elastic layer is not limited to relying only on the restoring force and frictional force of the elastic body, but may also be performed by reinforcing the binding force using an adhesive or the like.

In addition, in FIGS. 1 to 4, the present invention is not limited only to the configurations shown in the figures. In particular, the structure of the magnetic field generation layer is not limited to those shown in the first surface to FIG.
It is also possible to disperse functional powder other than magnetic powder, such as conductive particles, and use it as a floating electrode to improve the development electrode effect. A structure that improves the developing electrode effect or abrasion resistance is also possible, and various layer structures are possible, such as a multilayer structure in which the magnetic field generating part and the conductive part are functionally separated.

Further, although the arrows indicate the rotation direction of each member, this does not limit the present invention.

Furthermore, the developing method can be used regardless of whether it is regular development or reversal development.

Further, as the toner used in the present invention, all toners known as magnetic toners can be used, and either resin-based toner or wax-based toner may be used. It is made by adding magnetic powder, coloring agents, external additives, and other additives to the powder, and is created by pulverization or polymerization methods.

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 above configuration of the present invention, the magnetic field generation layer is disposed on the elastic layer, so that the magnetic properties of the magnetic field generation layer and the g! Since it can be set suitably for conductive development and does not damage the latent image carrier even when pressure-contact development is performed, it is possible to obtain high-resolution and high-temperature layer images for a long period of time. This eliminates the need to manage the development gap between the image carrier and the latent image carrier, and has the effect that the development device can be provided at a low price.

In addition, by constructing the magnetic field generating layer with a sleeve in which magnetic powder is dispersed in rubber or elastomer, damage caused by handling of the magnetic field generating layer during assembly can be reduced, and the elasticity and frictional force of rubber can be used. Since the magnetic field generating layer can be attached to the elastic layer without an adhesive layer, the assembly is simple, the number of assembly steps can be reduced, and the developing device can be provided at a low price.

Furthermore, the minimum magnetization reversal pitch of the magnetic field generation layer was set to 100 [μ
m] or less, it is possible to form a uniform and thin toner layer (or a thin magnetic brush layer with a fine pitch) on the toner carrier, and it is possible to form a uniform and thin toner layer (or a thin magnetic brush layer with a fine pitch) on the toner carrier, and it is possible to prevent uneven distribution due to fluctuations in the magnetic field and fluctuations in the toner layer thickness. This has the effect that high-resolution development can be performed.

Therefore, the developing device of the present invention has the excellent effect of being able to provide a small and lightweight developing device at a low cost that can obtain high-resolution images with few image defects such as ground blur and trailing in magnetic development. It is.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional schematic view of an image forming apparatus using a developing device of the present invention, FIG. 2 is a cross-sectional view of a toner carrier in an embodiment of the present invention, and FIG. FIG. 4 is an explanatory diagram of a method for manufacturing a developing roller in an example;
Figures 4-a and 4-b are explanatory diagrams of a method for manufacturing a developing roller in another embodiment of the present invention. 1 ・・・・・・・・・・・・・・・Latent image carrier 7
・・・・・・・・・・・・・・・Developing device 8 ・
・・・・・・・・・・・・・・・ Toner 9 ・・・・・・
・・・・・・・・・・・・Developing roller 11...
・・・・・・・・・・・・ Elastic layer 12 ・・・・・・
...... Magnetic field generation layer 21 ...
・・・・・・・・・・・・Magnetic powder 22 ・・・・・・・・・
・・・・・・・・・ Binder 31 ・・・・・・・・・
・・・・・・・・・ Sleeve and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kisanbe Suzuki (@!1 person) Figure 4-a

Claims (2)

[Claims] (1) A developing device that conveys magnetic toner by a toner carrier and develops the magnetic toner onto a latent image carrier, the toner carrier having at least an elastic or flexible member and a magnetic field generating layer. A developing device characterized in that the magnetic field generating layer is made of a sleeve in which magnetic powder is dispersed in rubber or elastomer. (2) The minimum magnetization reversal pitch of the magnetic field generation layer is 100[
2. The developing device according to claim 1, wherein the developing device has a diameter of less than [μm].