JPH0336571A - developing device - Google Patents

Abstract

PURPOSE:To stably form a high-quality image for a long time by allowing a magnetic roller to contain a rare earth magnet and providing a covering layer on the surface of the magnetic roller. CONSTITUTION:In a developing device 7, developer 8 being the composite element of developer is electrostatically charged and conveyed by the cylindrical magnetic roller 9 which rotates in a direction shown by B in a figure. In such case, the magnetic roller 9 contains the rare earth magnet 14 and the covering layer 16 is provided on the surface of the roller 9. Then, at least the developer conveying surface of the roller 9 is covered lest the magnet 14 should be exposed. Therefore, oxide corrosion caused by the effect of oxygen or water content, etc., in the air is prevented from occurring on the surface of the roller 9. Thus, the high-quality image is stably formed for a long time.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a magnetic brush developing device.

[Prior Art] A conventional developing device, known as a magnetic brush developing device, has a plurality of magnetic poles attached to a rotatable non-magnetic and conductive cylindrical developer conveying member, also called a developing sleeve. It has a magnetized cylindrical magnetic roller, holds the developer on the developer transport member by a magnetic field generated by the magnetic roller, and develops by rotating at least one of the magnetic roller and the developer transport member. It was used to transport the developer on the agent transport member. As is well known, examples of the developer include a one-component developer made up of only a developer and a two-component developer made up of a developer and a carrier.

In such a developing device, polishing of the outer diameter of the magnetic roller, processing of the outer diameter of the developer conveying member, and accurate placement of the magnetic roller with a small gap between it and the conveying member are required. In addition, there are many components of the developing device, such as magnetic rollers, developer conveying members, and parts to support each, and it is necessary to make the developing device smaller and lighter. was not possible.

Furthermore, if the number of magnetized poles of the magnetic roller is increased in order to reduce uneven development density due to the magnetic pole pitch of the magnetic roller that occurs in the image when the magnetic roller is rotated, sufficient leakage magnetic flux will be generated on the developer transport member. Therefore, it was not possible to secure a sufficient amount of developer to be transported.

[Problems to be Solved by the Invention] Therefore, the present applicant has devised a developing device that directly conveys developer on the surface of a magnetic roller, as a developing device that solves these problems. As the magnet material of the magnetic roller, known magnet materials such as ferrite, alnico, manganese aluminum, and rare earth magnets can be used, but in particular, 14 types of atomic numbers ranging from 58 to 71 (element symbols Ce to Lu) can be used. rare earth elements, among them Nd, Pr and S
At least one of the rare earth elements represented by m, Fe,
At least one of the 3d transition metals represented by Ni and CO
However, when a magnetic roller containing a rare earth magnet containing Fe is used, the surface of the magnetic roller may be affected by oxygen or moisture in the air. Oxidative corrosion (
This has the problem that high-quality images cannot be stably formed over a long period of time due to the occurrence of so-called rust.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a developing device that can stably form high-quality images over a long period of time.

[Means for Solving the Problems] A developing device of the present invention includes a cylindrical magnetic roller magnetized with a plurality of magnetic poles, and a magnetic field generated by the magnetic roller causes the developer to be transferred to the magnetic roller. In a developing device that transports the developer by rotating the magnetic roller, the magnetic roller includes a rare earth magnet, and a coating layer is provided on the surface of the magnetic roller. The magnet is coated so that the magnet is not exposed on the developer transport surface of the magnet.

[Function] According to the above configuration of the present invention, by providing a coating layer on the surface of the magnetic roller, even when a magnetic roller containing a rare earth magnet is used, the above-mentioned Since oxidative corrosion does not occur on the surface of the magnetic roller, high-quality images can be stably formed over a long period of time.

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

[Embodiment] FIG. 1 shows a cross-sectional schematic view of an image forming apparatus including a developing device in an embodiment of the present invention.

A latent image carrier 1 that rotates in the direction shown in the figure is composed of a conductive support 2 coated with a photoconductive photosensitive layer 3. After being charged to a potential of form an image.

The developing device 7 charges a developer 8, which is a component of the developer, and conveys the developer 8 with a cylindrical magnetic roller 9 rotating in the direction indicated by B in the figure. The surface of the magnetic roller 9 is coated with a coating layer 16 so that the magnet 14 is not exposed at least on the developer conveying surface of the magnetic roller 9. The developer 8 held on the magnetic roller 9 by magnetic force is regulated to an appropriate amount by the developer conveyance amount regulating member 10, and then conveyed to a development gap portion where the latent image carrier 1 and the magnetic roller 9 are close to each other. The developer 8 adheres to the electrostatic latent image on the latent image carrier 1 in accordance with the electric potential of the electrostatic latent image on the latent image carrier 1 and the bias voltage from the electric current Wll, which is a developing bias voltage applying means, and thereby the latent image is developed. The electrostatic latent image on the image carrier 1 is visualized.

The developer 8 (which has developed the electrostatic latent image on the latent image carrier 1) is transferred onto the recording paper 13 by the transfer device 12, and is further fixed on the recording paper 13 by means such as pressure or heating, thereby creating a desired image. images can be obtained.

As the coating layer 16 in the present invention, the magnetic roller 9
Any material can be used as long as it can cover the surface of the magnet 14 so that the magnet 14 is not exposed; for example, Al,
Non-ferrous metals such as Ni, Au, Pt, Fe1O4, SiO2
It is possible to use inorganic oxides such as, resins such as polycarbonate, polystyrene, etc. Further, the thickness of the coating layer 16 is desirably 1 μm or more from the viewpoint of preventing defects such as pinholes during formation of the coating layer and preventing deterioration of the coating layer during long-term use.

In this embodiment, as shown in FIG. 1, the rotation directions of the latent image carrier 1 and the magnetic roller 9 are indicated by A in the figure.
and B, but this does not limit the present invention. In the present invention, any developer known as a one-component magnetic brush developer or a two-component magnetic brush developer can be used. .

Example 1 In this example, a neodymium-iron sintered magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with an epoxy resin as the coating layer 16.

Images equivalent to 50,000 sheets of A4 size plain paper were continuously formed in an environment of a temperature of 30° C. and a relative humidity of 60% using an image forming apparatus with a developing device configured as described above.
No deterioration of the obtained image was observed, and a high quality image with high resolution was obtained, similar to the first printed sheet. Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 1 An image forming apparatus similar to that of Example 1 was produced using an image forming apparatus having a developing device having the same configuration as that of Example 1 except that the surface of the magnetic roller 9 was not coated with epoxy resin and the magnet 14 was exposed. When images equivalent to 500 sheets of A4 size plain paper were continuously formed in an environment, the resulting images showed deterioration such as blurred brush marks and ground covering, and the surface of the magnetic roller 9 showed some deterioration. Oxidation corrosion was observed.

Example 2 In this example, a neodymium-iron sintered magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with Ni (Ni plating) as the coating layer 16.

Using an image forming apparatus with the developing device configured as described above, 50,000 pieces of A4 size plain paper were processed under the same environment as in Example 1.
Images corresponding to the number of sheets were successively formed, but no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained as with the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 2 Magnet 1 without coating the surface of magnetic roller 9 with Ni
Images equivalent to 50,000 sheets of A4 size plain paper were continuously formed under the same environment as in Example 1 using an image forming apparatus with a developing device having the same configuration as in Example 2 except that 4 was exposed. However, deterioration such as blurred brush marks and ground covering was observed in the obtained image, and oxidative corrosion was observed on the surface of the magnetic roller 9.

Example 3 In this example, a neodymium-iron sintered magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with SiO2 as the coating layer 16.

Using an image forming apparatus with the developing device configured as described above, 50,000 pieces of A4 size plain paper were processed under the same environment as in Example 1.
Images corresponding to the number of sheets were successively formed, but no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained as with the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 3 An image forming apparatus with a developing device having the same configuration as in Example 3 was used, except that the surface of the magnetic roller 9 was not coated with 5iOz and the magnet 14 was exposed, and the environment was the same as in Example 1. When images equivalent to 50,000 sheets of A4 size plain paper were continuously formed below, deterioration such as misalignment of brush marks and ground covering was observed in the resulting images, and there was also some deterioration on the surface of the magnetic roller 9. Oxidation corrosion was observed.

Example 4 In this example, a neodymium-iron sintered magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with TiO2 as the coating layer 16.

Using an image forming apparatus with the developing device configured as described above, 50,000 pieces of A4 size plain paper were processed under the same environment as in Example 1.
Images corresponding to the number of sheets were successively formed, but no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained as with the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 4 An image forming apparatus with a developing device having the same configuration as in Example 3 was used, except that the surface of the magnetic roller 9 was not coated with TiO2 and the magnet 14 was exposed, and the environment was the same as in Example 1. When images equivalent to 50,000 sheets of A4 size plain paper were continuously formed below, deterioration such as blurred brush marks and ground covering was observed in the resulting images, and the surface of the magnetic roller 9 was Oxidative corrosion was observed.

Example 5 In this example, a praseodymium-iron cast magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with SiC as the coating layer 16.

Using an image forming apparatus with the developing device configured as described above, 50,000 pieces of A4 size plain paper were processed under the same environment as in Example 1.
Images corresponding to the number of sheets were successively formed, but no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained as with the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 5 An image forming apparatus having a developing device having the same configuration as in Example 4 was used, except that the surface of the magnetic roller 9 was not coated with SiC and the magnet 14 was exposed, and the same environment as in Example 1 was used. When images equivalent to 500 sheets of A4 size plain paper were continuously formed below, deterioration such as blurring of brush marks and ground covering was observed in the obtained images, and the surface of the magnetic roller 9 was Oxidative corrosion was observed.

Example 6 In this example, a praseodymium-iron cast magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with Al2O3 as the coating layer 16.

Using an image forming apparatus with the developing device configured as described above, 50,000 pieces of A4 size plain paper were processed under the same environment as in Example 1.
Images corresponding to the number of sheets were successively formed, but no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained as with the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 6 An image forming apparatus with a developing device having the same configuration as in Example 5 was used, except that the surface of the magnetic roller 9 was not coated with Al2O3 and the magnet 14 was exposed, and the same environment as in Example 1 was used. When images equivalent to 50,000 sheets of A4 size plain paper were continuously formed below, deterioration such as blurred brush marks and ground covering was observed in the resulting images, and the surface of the magnetic roller 9 was Oxidative corrosion was observed.

Example 7 In this example, a praseodymium-iron cast magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with ZnO as the coating layer 16.

Using an image forming apparatus with the developing device configured as described above, 50,000 pieces of A4 size plain paper were processed under the same environment as in Example 1.
Images corresponding to the number of sheets were successively formed, but no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained as with the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 7 An image forming apparatus with a developing device having the same configuration as in Example 5 was used, except that the surface of the magnetic roller 9 was not coated with ZnO and the magnet 14 was exposed, and the same environment as in Example 1 was used. Below, images equivalent to 500 sheets of A4 size plain paper (10 sheets) were continuously formed, and the resulting images showed deterioration such as blurring of brush strokes and ground covering, and the surface of the magnetic roller 9 Oxidative corrosion was observed.

Example 8 In this example, an extruded praseodymium-iron magnet was used as the magnetic roller 9, and the surface of the magnetic roller 9 was coated with A1 as the coating layer 16.

Using an image forming apparatus with the developing device configured as described above, 5000 sheets of A4 size plain paper were processed under the same environment as Example gg1.
Although images equivalent to 0 sheets were continuously formed, no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained, similar to the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 8 Magnet 1 without coating the surface of magnetic roller 9 with Al
Images equivalent to 50,000 sheets of A4 size plain paper were continuously formed under the same environment as in Example 1 using an image forming apparatus with a developing device having the same configuration as in Example 5 except that 4 was exposed. However, deterioration such as blurred brush marks and ground covering was observed in the obtained image, and oxidative corrosion was observed on the surface of the magnetic roller 9.

Example 9 In this example, a samarium-cobalt extruded magnet is used as the magnetic roller 9, and a coating layer 16 is used.
As a result, the surface of the magnetic roller 9 was coated with Ni.

Using an image forming apparatus with the developing device configured as described above, 50,000 pieces of A4 size plain paper were processed under the same environment as in Example 1.
Although images corresponding to the number of sheets were continuously formed, no deterioration of the obtained images was observed, and a high quality image with high resolution was obtained as in the case of 1 print B.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer having a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 9 Magnet 1 without coating the surface of magnetic roller 9 with Ni
Using a lil image forming apparatus with a developing device having the same configuration as in Example 5 except that 4 was exposed, images equivalent to 50,000 sheets of A4 size normal Mf were continuously produced under the same environment as in Example 1. When the image was formed, deterioration such as brush marks, misalignment, and ground covering was observed in the resulting image, and
Oxidative corrosion was observed on the surface of the magnetic roller 9.

Example 10 In this example, a samarium-cobalt compression molded magnet is used as the magnetic roller 9, and a coating layer 16 is used.
As a result, the surface of the magnetic roller 9 was coated with TiO2.

Using an image forming apparatus with a developing device configured as described above, 50,000 sheets of A4 size plain paper were processed under the same environment as the actual ML.
Images corresponding to the number of sheets were successively formed, but no deterioration of the obtained images was observed, and high-quality images with high resolution were obtained as with the first printed sheet.

Further, no oxidative corrosion was observed on the surface of the magnetic roller 9, and a developer layer with a uniform thickness was stably formed on the magnetic roller 9.

Comparative Example 10 An image forming apparatus having a developing device having the same configuration as in Example 5 was used, except that the surface of the magnetic roller 9 was not coated with TlO2 and the magnet 14 was exposed, and the same environment as in Example 1 was used. When images equivalent to 50,000 sheets of A4 size plain paper were continuously formed below, deterioration such as blurred brush marks and ground covering was observed in the resulting images, and the surface of the magnetic roller 9 was Oxidative corrosion was observed.

Although the embodiments have been described above, the present invention is particularly effective when applied not only to the above embodiments but also to a wide range of image forming apparatuses such as electrophotographic recording apparatuses, such as page printers, facsimile machines, and copying machines.

[P! [Bright Effect] As described above, according to the present invention, a cylindrical magnetic roller magnetized with a plurality of magnetic poles is provided, and the developer is transferred onto the magnetic roller by the magnetic field generated by the magnetic roller. In a developing device that transports the developer by rotating the magnetic roller, when the magnetic roller contains a rare earth magnet, a coating layer is provided on the surface of the magnetic roller, and more particularly, when the magnetic roller contains a rare earth magnet, Fe Even when containing, a developer layer can be stably formed on the magnetic roller without causing oxidative corrosion on the surface of the magnetic roller, and a high-resolution and high-quality image can be stably formed. It has this effect.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus including a developing device according to an embodiment of the present invention. Latent image carrier Developer Magnetic roller Developer transport amount regulating member Power supply coating layer and above

Claims (1)

[Claims] It has a cylindrical magnetic roller magnetized with a plurality of magnetic poles, the developer is held on the magnetic roller by a magnetic field generated by the magnetic roller, and the developer is rotated to hold the developer on the magnetic roller. What is claimed is: 1. A developing device for transporting a magnetic roller, wherein the magnetic roller includes a rare earth magnet, and a coating layer is provided on the surface of the magnetic roller.