JPH04142579A - Developing device - Google Patents

Abstract

PURPOSE:To enable high-resolution press-contacting development using magnetic toner by incorporating specific resin in the binder of the magnetic field producing layer of a toner carrier which carries the magnetic toner, setting its film thickness and minimum magnetism inversion pitch below specific values, and forming a protection layer on its surface. CONSTITUTION:A developing roller 9 holds and carries the magnetic toner 8 which leaking magnetic flux at the outer periphery of the protection layer 14. When the toner 8 is carried to a development gap part, the toner 8 sticks on a latent image carrier 1 according to a developing electric field, produced by a developing bias applying means 16 according to the potential contrast of the latent image carrier 1, to visualize an electrostatic latent image. Vinyl copolymer resin and resin such as polyamide are blended and used as the binder of the magnetic field producing layer. Further, the magnetic field producing layer is reduced in thickness to <=100mum and its minimum inversion pitch is set to <=100mum. The protection layer is formed thinly of SiO2, Al2O3, carbon, etc., to about <=10mum thickness to prevent the surface of the magnetic field producing layer, etc., from wearing.

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 and develops magnetic toner.

[Prior Art] 1. A developing device using conventional magnetic toner is disclosed in Japanese Patent Application Laid-open No. 1983-
43530, a magnetic field generating means is formed by molding a kneaded material in which a permanent magnet material is dispersed in a medium such as a resin into a mold shape or coating it on a substrate, and the magnetic field generating means is arranged at minute intervals. Magnetization reduces toner conveyance unevenness in one-component magnetic brush development.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, since the development is performed in close proximity, the distance M (gap) between the latent image carrier and the development electrode is large, making it difficult to form a high-resolution image. Met.

Therefore, in order to solve such problems, the present applicant proposed a magnetic pressure-contact developing device in Japanese Patent Application No. 2-58321, etc., but the present invention proposes a magnetic field generating layer of a toner carrier that can be used in such a developing device. The purpose is to provide a developing device suitable for developing magnetic toner with high resolution. Still another object is to provide a developing device capable of pressure-contact development of magnetic toner.

[Means for Solving the Problems] A developing device of the present invention is a developing device that conveys magnetic toner by a toner carrier and develops the magnetic toner on a latent image carrier, wherein the toner carrier is exposed to at least a magnetic field. It has a generating layer, and the binder of the magnetic field generating layer contains at least one of vinyl resin, polyamide, nitrocellulose, and cellulose acetobutyrate.

Further, the developing device of the present invention is characterized in that it has a protective layer on the surface of the magnetic field generation layer.

Further, in the developing device of the present invention, the thickness of the magnetic field generation layer is 100 mm.
[μm] or less.

Furthermore, 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, since the magnetic field generating layer has excellent flexibility, development can be performed with the toner carrier in pressure contact with the latent image carrier, and the developing electrode is attached to the latent image carrier. It is possible to form a high-resolution image by bringing them into close proximity. Further, according to the above structure of the present invention, the dispersibility of the magnetic powder etc. is improved by containing at least one of vinyl resin, nitrocellulose resin, or cellulose acetobutyrate resin in the binder of the magnetic field generating layer. This improves the magnetic properties, makes the magnetic properties uniform, makes toner transport uniform and stable, and further improves the development properties, making it possible to form high-quality images.

Further, according to the above configuration of the present invention, the protective layer can prevent wear of the magnetic layer and improve the durability and reliability of the developing device.

Further, according to the above configuration of the present invention, the magnetic field generation layer is made up of 10
By reducing the thickness to 0 [μm] or less, sufficient flexibility can be imparted to the magnetic field generation layer.

Further, according to the above configuration of the present invention, the minimum magnetization reversal pitch of the magnetic field generation layer is set to 100 [μm] or less, so that a uniform and thin toner layer (or a fine-pitch magnetic brush thin layer) is formed on the toner carrier. layer), it is possible to reduce density unevenness due to fluctuations in the magnetic field and fluctuations in the toner layer thickness, and it is possible to perform high-resolution development.

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

[Example 1] FIG. 1 is a cross-sectional schematic diagram 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, a laser or LED
The light emitted from the light source 5 is passed through the imaging optical system 6 to the photosensitive layer 3.
A latent electrostatic image is formed by selectively irradiating light according to the image to obtain potential contrast. On the other hand, the developing device 7 conveys and develops the magnetic toner 8, and the developing roller 9 conveying the toner 8 has an elastic layer 1 formed on the outer periphery of the shaft 10.
1, a conductive layer 12, a magnetic field generating layer 13, and a protective layer 14 are arranged concentrically, and the magnetic toner 8 is held on the developing roller 9 by the leakage magnetic flux around the outer periphery of the protective layer 14. The toner 8 is conveyed in a thin layer by rotating the developing roller 9 in a state where the toner 8 is thinned to an appropriate amount by an elastic blade 15 in the shape of a thin plate spring made of metal or resin. When the toner 8 is conveyed to the development gap portion where the latent image carrier 1 and the developing roller 9 are close to each other, the latent image carrier 1
A developing electric field is formed by the potential contrast and developing bias applying means 16, and the toner 8 charged according to the developing electric field adheres to the latent image carrier 1, and the electrostatic latent image is visualized.

Furthermore, the toner image is transferred onto the recording paper 18 using a transfer device 17 such as a corona transfer device or a transfer roller, and the toner is fixed on the recording paper using heat or pressure to form the desired image on the recording paper. It's something you get. When we continuously formed 10,000 sheets of 600 [DPI] line images, character images, and solid images using the image forming apparatus shown in Fig. 1, we found that the 600 [DPI] line images did not become thicker. It was possible to stably form a high-temperature solid image with an OD value of 1.4 or more without any trailing or blurring at the edges of the image. Further, there was almost no wear of the protective layer before and after continuous image formation. Furthermore, when the cross section of the magnetic field generating layer of this example was observed by TEM, it was confirmed that there was no agglomeration of the magnetic powder and high dispersibility was observed.

In FIG. 1, the elastic layer 11 includes natural rubber, silicone rubber, isoprene rubber, urethane rubber, butadiene rubber,
Chloroprene rubber, neoprene rubber, NER, etc. can be used in the form of rubber, foam, sponge, etc.

Alternatively, any resin that can be formed into elastic foams, including elastomers, can be used, e.g.
It is possible to use styrene resin, vinyl chloride resin, polyurethane resin, polyethylene resin, methacrylic resin, etc. Further, the magnetic field generating layer 13 was formed by applying a magnetic paint having the following composition.

Vinyl chloride 40% solution 30wt% vinyl acetate 40% solution 30wt% polyurethane
40% solution 180wt% polyisocyanate
1wt% carbon black
2wt% silane coupling agent Iwt
%yFe203 100wt%
Toluene:THF:MEK 1:1:1 856wt% 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, and has approximately the same function and function as FIG. 1. Named members are given the same numbers and explanations are omitted. Developing device 2
1 conveys and develops the magnetic toner 8, and the developing roller 22 that conveys the toner 8 has a driving roller 23 that is rotationally driven and has a friction portion on the outer periphery, and an extra length is left on the outer periphery of the driving roller 23. A magnetic field generating layer 25 and a protective layer 26 are disposed in this order on the cylindrical thin film member 24, and magnetic flux is generated by leakage magnetic flux around the outer periphery of the protective layer 26. The toner 8 is held on the developing roller 22 and transported. The developing roller 22 is pressed against the latent image carrier 1 at a predetermined pressure, and when the toner 8 on the developing roller 22 is conveyed to the pressing portion, development is performed in the same manner as in the first embodiment. Using an image forming apparatus such as that shown in FIG.
When continuously formed over several sheets, a line image of 600 [DPI] was stably formed without line thickening, the resolution of the line pair image was the highest, there was no trailing or blurring at the edge of the image, and the OD value was 1. It was possible to stably form a solid image at a high temperature of .4 or higher. Further, there was almost no wear of the protective layer before and after continuous image formation.

Furthermore, when the cross section of the magnetic field generating layer of this example was observed by TEM, it was confirmed that there was no agglomeration of the magnetic powder and high dispersibility was observed.

In FIG. 2, the thin film member 24 is made of Ni, Co, Cu, Z
It is possible to use metals such as n, A1, or alloys containing them formed into a thin cylindrical shape. Alternatively, it is also possible to use a film-like resin or one whose surface is made conductive.

Further, the magnetic field generating layer 25 was formed by applying a magnetic paint having the following composition.

Nitrocellulose 40% solution 60wt% polyurethane 40% solution 180wt% polyisocyanate 1wt% carbon black
2wt% silane coupling agent
1wt%yFe203 100w
t%Toluene:THF:MEK 1:1:1 856wt% In Figures 1 and 2, the magnetic field generating layer contains vinyl such as vinyl acetate, vinyl alcohol, vinyl butyral, vinyl alcohol, vinyl ethyl ester, etc. Using at least one of copolymer resin, polyamide, nitrocellulose, or cellulose acetobutyrate, blended with other resins as necessary. For example, blending vinyl acetate, vinyl chloride, and polyurethane. Alternatively, by blending nitrocellulose and polyester, or blending cellulose acetobutyrate and vinyl formal, it is possible to design a binder that complements each other's properties and has both dispersibility and mechanical strength. Further, as the magnetic powder of the magnetic field generation layer, a magnetic powder known as a magnetic recording material or a magnet material can be used. magnetic material, e.g. y
-Fe203, Ba = FeS Ni-Co, Co-C
r, Mn-A1, etc. can be used. It is also possible to add additives such as a dispersant to the binder in which the magnetic powder is dispersed. Furthermore, the film thickness of the magnetic field generation layer is 100
[μm] or less, preferably around 10 [μm3,
For the same diameter, the bending stress, which is inversely proportional to the film thickness, is reduced to provide sufficient flexibility. In addition, by setting the minimum magnetization reversal pitch of the magnetic field generation layer to 100 [μm] or less, the leakage magnetic flux that attracts the magnetic toner is reduced approximately several tens [μm] from the surface of the magnetic field generation layer.
], the toner can be uniformly made into a thin layer, and at the same time, fluctuations in the amount of toner conveyed on the developing roller due to magnetic brush formation can be suppressed to a minute pitch, thereby reducing density unevenness.

In addition, the protective layer has a thickness of approximately 10 [μm] or less, and is made of SiO
2. A thin film of material such as Al2O3 or carbon is formed to prevent the surface of the magnetic field generation layer from wear and improve the durability of the developing device.

In addition, in FIG. 1 and FIG. 2, the present invention is not limited only to the configurations in the figures. In particular, the layer structures of the developing roller 9 and the thin film member 24 are not limited to those shown in FIGS. A stacked layer structure is possible, such as a layer structure in which an intermediate layer is provided, and a structure in which a floating electrode is provided in a predetermined layer to improve the developing electrode effect is also possible. 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. Furthermore, the toner used in the present invention includes:
All known toners can be used as magnetic toners, 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.

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 magnetic field generating layer has sufficient flexibility, making it possible to perform good press-contact development. Further, according to the present invention, by developing with a developing roller containing at least one of vinyl resin, polyamide, nitrocellulose, or cellulose acetobutyrate as a binder of the magnetic field generating layer,
It makes magnetic properties uniform, makes toner transport uniform and stable, and furthermore realizes high development characteristics, making it possible to stably supply high-quality images. Furthermore, it is possible to provide a small and low-cost developing device with a simple structure, which has the effect of stably forming high-resolution, high-quality images.

Further, according to the present invention, by providing a protective layer on the magnetic field generating layer, the magnetic field generating layer is protected from mechanical deterioration such as wear,
This has the effect of stabilizing the amount of toner conveyed over a long period of time and providing a highly reliable developing device.

Further, by setting the thickness of the magnetic field generating layer to 100 [μm] or less, sufficient flexibility can be imparted to the magnetic field generating layer, thereby making it possible to perform good pressure-contact development.

In addition, the minimum magnetization reversal pitch of the magnetic field generation layer was set to 100 [μm
] Form a thin toner layer by doing the following,
This has the effect of enabling good pressure development.

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 magnetic development.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus using a developing device of the present invention, and FIG. 2 is a schematic cross-sectional view of an image forming apparatus using a developing device according to another embodiment of the present invention. 7.21...Developing device 8...Toner 9.22...Developing roller 11...Elastic layer, magnetic field generating layer, protective layer and above

Claims (4)

[Claims] (1) A developing device that conveys magnetic toner by a toner carrier and develops the magnetic toner on a latent image carrier, wherein the toner carrier has at least a magnetic field generating layer, and a binder of the magnetic field generating layer A developing device comprising at least one of a vinyl resin, a nitrocellulose resin, or a cellulose acetobutyrate resin. (2) The developing device according to claim 1, further comprising a protective layer on the surface of the magnetic field generating layer. (3) The developing device according to claim 1 or 2, wherein the thickness of the magnetic field generation layer is 100 [μm] or less. (4) The minimum magnetization reversal pitch of the magnetic field generation layer is 100[
3. The developing device according to claim 1 or 2, wherein the developing device has a particle size of 1.0 μm or less.