JP2916787B2 - Developing device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a developing device using a one-component magnetic toner, and more specifically, to transport a one-component magnetic toner by a developing roller having an elastic layer and a magnetic field generating layer. And a developing device for developing.

[Prior Art] As disclosed in USP-4121931, a conventional developing device uses a developing roller having a magnet roller inside a non-magnetic cylindrical sleeve to place a magnetic brush of one-component magnetic toner on the sleeve. It is formed, and transports and develops a one-component magnetic toner, which is known as a one-component magnetic brush developing method.

Further, as a developing method for improving the above-described one-component magnetic brush developing method, a FEED developing method in which a floating electrode is provided on a developing roller to improve the image quality of a line image and a solid image as disclosed in US Pat. A developing device has been proposed in which toner thinned on the surface of a magnet roller is transported and developed on a belt-like latent image carrier as disclosed in -4851874.

[Problems to be Solved by the Invention] However, in the one-component magnetic brush developing method and the FEED developing method among the above-described conventional techniques, the developing roller is constituted by a developing sleeve and a magnet roller, and the structure is complicated, large, and cost-effective. And there are many factors deteriorating the image quality, such as density unevenness due to the magnetic field fluctuation of the magnet roller and trailing of the edge of the image. Also, in the developing method in which the toner thinned on the surface of the magnet roller is transported and developed, the image quality is similarly degraded due to the fluctuation of the magnetic field of the magnet roller, and the apparatus is large due to the use of the belt-like latent image carrier. Had the problem of becoming

Therefore, the present invention solves such a problem,
An object of the present invention is to provide a developing device suitable for developing a one-component magnetic toner. Still another object is to provide a small-sized and low-cost developing device having a simple structure. Still another object is to provide a developing device with high resolution and high image quality.

[Means for Solving the Problems] In a developing device of the present invention, a one-component magnetic toner is transported by a developing roller and the one-component magnetic toner is developed on a latent image carrier. And a magnetic field generating layer having flexibility on the elastic layer, wherein the magnetic field generating layer is magnetized in a lattice shape in which N poles and S poles appear alternately, and the magnetization reversal pitch is 100 μm or less. Features.

[Operation] According to the above configuration of the present invention, the structure of the developing roller is simply simplified by conveying the toner near the surface of the thin magnetic field generating layer and forming the developing roller with a single rotating body. Instead, a compact, lightweight and low-cost developing roller can be obtained. Further, the thin magnetic field generating layer is magnetized at a fine pitch to form a uniform and thin toner layer (or a fine pitch magnetic brush thin layer) on the developing roller. High-resolution development can be performed by reducing density unevenness and the like due to fluctuations in the toner layer thickness.

Further, according to the above configuration of the present invention, regardless of contact development or non-contact development, a uniform and thin toner layer is formed on the developing roller, and the thickness of the toner layer on the developing roller is changed. Density fluctuation can be reduced.

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

Furthermore, by providing an insulating layer on the developing roller,
The frictional charging between the developing roller and the toner can be stably performed, and the time variation of the developing density can be reduced.

 Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus using a developing device of the present invention, in which a latent image carrier 1 includes a conductive support 2.
Is coated with a photosensitive layer 3 having organic or inorganic photoconductivity, and the photosensitive layer 3 is charged using a charger 4 such as a corona charger or a charging roller.
Light emitted from a light source 5 such as an LED is selectively irradiated on the photosensitive layer 3 through an imaging optical system 6 in accordance with an image to obtain a potential contrast to form an electrostatic latent image. On the other hand, the developing device 7 transports and develops the magnetic toner 8, and the developing roller 9 that transports the toner 8 has an elastic layer around the shaft 10.
11 and the magnetic field generating layer 12 are arranged concentrically, and the magnetic toner 8 is directly held on the developing roller 9 by the leakage magnetic flux on the outer periphery of the magnetic field generating layer 12, and is made of non-magnetic or magnetic metal or resin. The developing roller 9 is rotated in a state where the developing roller 9 is regulated to an appropriate amount by the plate-like blade 13 configured, and the thin layer toner 8 is conveyed. When the toner 8 is transported to the developing 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 developing bias applying means 14, and the electric field is charged according to the developing electric field. The toner 8 adheres to the latent image carrier 1 and the electrostatic latent image is visualized. Further, a toner image is transferred onto the 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. Using an image forming apparatus as shown in FIG. 1, 600 [DPI] line images, character images and solid images were continuously formed over 10,000 sheets, and the 600 [DPI] line images were not thickened. It is formed stably and has no tailing or background fogging at the edges of the image.It can stably form high-density solid images with an OD value of 1.4 or more. There was no ground fog on the carrier, and the amount of waste toner was significantly reduced.

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, in which members having substantially the same functions and the same names as those in FIG. I do. The developing device 21 transports and develops the magnetic toner 8, and the developing roller 9 that transports the toner 8 directly holds the magnetic toner 8 on the developing roller 9 by the leakage magnetic flux on the outer periphery of the magnetic field generation layer 11. Then, the layer is appropriately thinned by a thin leaf spring-like elastic blade 22 made of non-magnetic or magnetic metal or resin, and the developing roller 9 is rotated to convey the thin layer toner 8. The developing roller 9 is pressed against the latent image carrier 1 at a predetermined pressure, and when the toner 8 on the developing roller 9 is conveyed to the pressing portion, the potential contrast of the latent image carrier 1 and the developing bias applying means 14 are used. The toner 8 charged in accordance with the developing electric field adheres to the latent image carrier 1, and the electrostatic latent image is visualized. When an image forming apparatus as shown in FIG. 2 was used to continuously form a line image of 600 [DPI], a character image and a solid image over 10,000 sheets, the line image of 600 [DPI] was not thickened. It is possible to stably form a high-density solid image with an OD value of 1.4 or more with no line tailing or ground fogging at the edge of the image. As a matter of course, there was no ground fog, and there was no ground fog on the latent image carrier, so that the amount of waste toner could be greatly reduced.

FIG. 3 is a schematic cross-sectional view of an image forming apparatus using a developing device in still another embodiment of the present invention. Members having substantially the same functions and the same names as those in FIG. Omitted. The developing device 31 transports and develops the magnetic toner 8, and the developing roller 9 that transports the toner 8 includes:
The magnetic toner 8 is directly held on the developing roller 9 by the leakage magnetic flux on the outer periphery of the magnetic field generating layer 11, and a blade 32 made of non-magnetic or magnetic metal or resin suspended by a spring or the like is pressed against the developing roller 9. The developing roller 9 is rotated to transport the toner 8 in a thin layer. The developing roller 9 is provided on the latent image carrier 1 via 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 developing gap portion where the developing roller 9 and the developing roller 9 come close to each other, the toner 8 charged according to the developing electric field by the potential contrast of the latent image carrier 1 and the developing bias applying means 14 is used. And the electrostatic latent image is visualized. Using an image forming apparatus as shown in FIG. 3, 600 [DPI] line images, character images and solid images were continuously formed over 10,000 sheets.
I] The line image of [I] is formed stably without thickening, and there is no tailing or fogging at the image edge, and a high-density solid image with an OD value of 1.4 or more can be formed stably. There was no background fog on the paper, and also there was no background fog on the latent image carrier, and the amount of waste toner could be greatly reduced.

1 to 3, the elastic layer 11 is made of natural rubber, silicone rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, or the like. The elastic layer may be made of rubber, foam, sponge, or the like. The thickness of the elastic layer 11 varies depending on the developing method and the method of regulating the amount of toner transported.
[Μm] or more is desirable. The magnetic field generating layer 12
Known magnetic recording materials and magnet materials can be used, more specifically, Fe, Ni, Co, Mn, a magnetic material containing at least one element of, for example, γ
_{-Fe 2 O 3, Ba-Fe} , Ni-Co, Co-Cr, Mn-Al and the like can be used, the film thickness is thinned in the longitudinal 100 [[mu] m] or less preferably 10 [[mu] m], the minimum magnetization inversion pitch Is set to 100 [μm] or less, and at the same time, the toner is uniformly thinned, and at the same time, the variation of the toner conveyance amount on the developing roller due to the formation of the magnetic brush is suppressed to a minute pitch, so that the density unevenness can be reduced. Further, as the toner used in the present invention, all toners known as one-component magnetic toner can be used, and any of resin-based toner and wax-based toner may be used. As is known, the composition of the developer is obtained by adding a magnetic powder, a colorant, an external additive, and other additives to a resin, and is prepared by a pulverization method, a polymerization method, or the like.

In FIGS. 1 to 3, the present invention is not limited only by the configurations shown in the drawings. Arrows indicate the rotation directions of the respective members, but do not limit the present invention.
Further, the developing method can be used regardless of whether it is regular development or reversal development.

FIGS. 4 to 9 show the layer structure of the developing roller in the embodiment of the present invention.

FIG. 4 (a) is a diagram showing a layer structure of a developing roller in an embodiment of the present invention. An elastic layer 42 mainly composed of an elastic resin is formed on a base 41 such as a shaft. A magnetic field generating layer 43 is formed on the substrate to form a developing roller. By magnetizing the magnetic field generating layer 43 in the horizontal direction so that the magnetization reversal pitch P becomes 100 [μm] or less, a fine toner chain of the toner 44 is formed on the magnetic field generating layer 43, and a thin and stable toner is formed. A layer is obtained. Also, by dispersing a conductive material such as carbon black in the elastic resin to form the elastic layer 42, a developing bias voltage is applied to the elastic layer 42 to improve a developing electrode effect, thereby achieving high resolution images. Obtainable. Furthermore, as shown in FIG. 4 (b), by magnetizing the magnetic field generating layer 45 in the vertical direction, the magnetization reversal pitch can be increased to the particle diameter of the toner (about 10 [μm]). It is also possible to uniformly form a thin layer of the toner 46, and since a strong magnetic field is obtained on the surface of the magnetic field generating layer, the content of the magnetic powder in the toner 46 is reduced to facilitate the production of the toner and the fixing property. Improvements are possible. 4th
In the example shown in FIG. 2B, a larger magnetic field can be obtained on the surface of the magnetic field generating layer 45 by providing a magnetic circuit of a soft magnetic material on the back surface of the magnetic field generating layer 45. The arrow in the figure indicates the direction of magnetization.

FIG. 5 is a view showing a layer structure of a developing roller according to another embodiment of the present invention. An elastic layer 52 made of a foamable resin is formed on a base 51 such as a shaft, and a conductive layer is formed on the elastic layer 52.
53 is formed, and a magnetic field generating layer 54 is formed on the conductive layer 53 to form a developing roller. By magnetizing the magnetic field generation layer 54 in the horizontal direction so that the magnetization reversal pitch is 100 [μm] or less, a fine toner chain of toner 55 is formed on the magnetic field generation layer 54, and a thin and stable toner layer is formed. Is obtained. Therefore, a high-resolution image can be obtained by applying a developing bias voltage to the conductive layer 53 to improve the developing electrode effect. As a material of the conductive layer 53, a conductive material such as carbon black can be used in addition to a material containing a conductive metal such as Al and Ni, and the conductive layer 53 is formed by means such as adhesion, coating, plating, or the like. can do. The arrows in the figure indicate the direction of magnetization, and the magnetic field generating layer 54 may be a perpendicular magnetization film.

FIG. 6 is a view showing a layer structure of a developing roller according to still another embodiment of the present invention, in which an elastic layer 62 such as a sponge is formed on a base 61 such as a shaft, and a magnetic field generating layer is formed on the elastic layer 62. 63 is formed, and a conductive layer 64 is formed on the magnetic field generating layer 63 to form a developing roller. By magnetizing the magnetic field generation layer 63 in the horizontal direction with a fine magnetization reversal pitch, a fine toner chain of the toner 65 is formed on the magnetic field generation layer 63, and a thin and stable toner layer can be obtained. Therefore,
A developing bias voltage is applied to the conductive layer 64 to improve the developing electrode effect and obtain a high-resolution image.
When the conductive layer 64 is formed of a metal thin film containing, for example, Cr or Cr, the conductive layer 64 functions as a protective film for the magnetic field generating layer 63 and the life of the developing roller can be extended. The arrow in the figure indicates the direction of magnetization,
The magnetic field generation layer 63 may be a perpendicular magnetization film.

FIG. 7 is a view showing a layer structure of a developing roller according to still another embodiment of the present invention, in which an elastic layer 72 mainly composed of an elastic resin is formed on a base 71 such as a shaft, and A magnetic field generating layer 73 is formed thereon, and an insulating layer 74 is formed on the magnetic field generating layer 73 to form a developing roller. As in the above-described embodiment, a fine toner chain of the toner 75 is formed on the magnetic field generating layer 73, and a thin and stable toner layer can be obtained. By providing the insulating layer 74 at the contact portion with the toner 75, it is possible to not only control the charge polarity and the charge amount of the toner 75, but also to use a resin having excellent wear resistance such as a fluorine resin for the insulating layer 74. Thereby, it can be used as a protective layer for the magnetic field generating layer 73. The arrows in the figure indicate the direction of magnetization, and the magnetic field generation layer 73 may be a perpendicular magnetization film.

FIG. 8 is a view showing a layer structure of a developing roller according to still another embodiment of the present invention, in which an elastic layer 82 containing an elastic resin as a main component is formed on a base 81 such as a shaft. A magnetic field generating layer 83, a conductive layer 84 is formed on the magnetic field generating layer 83, and an insulating layer 85 is formed on the conductive layer 84 to form a developing roller. As in the previous embodiment, the magnetic field generating layer
A minute toner chain of toner 86 is formed on 83, and a thin and stable toner layer is obtained. Therefore, a developing bias voltage is applied to the conductive layer 84 to improve the developing electrode effect, and a high-resolution image can be obtained. By providing the insulating layer 85 at the contact portion with the toner 86, the charging of the toner 86 is performed. Not only the control of the polarity and the control of the charge amount can be performed, but also a stable developing electrode effect can be maintained as a protective layer of the conductive layer 84 by using a resin having excellent abrasion resistance such as a fluorine resin for the insulating layer 85. The arrows in the figure indicate the direction of magnetization, and the magnetic field generating layer 83 may be a perpendicular magnetization film.

FIG. 9 is a view showing a layer structure of a developing roller according to still another embodiment of the present invention, in which an elastic layer 92 mainly composed of an elastic resin is formed on a base 91 such as a shaft. A conductive layer 93 is formed on the conductive layer 93, a magnetic field generating layer 94 is formed on the conductive layer 93, and an insulating layer 95 is formed on the magnetic field generating layer 94 to form a developing roller. As in the previous embodiment, the magnetic field generating layer
A fine toner chain of toner 96 is formed on 94, and a thin and stable toner layer is obtained. Therefore, a developing bias voltage is applied to the conductive layer 94 to improve the developing electrode effect, and a high-resolution image can be obtained. By providing the insulating layer 95 at the contact portion with the toner 96, the charging of the toner 96 can be performed. In addition to controlling the electrode properties and controlling the amount of charge, it is possible to maintain a stable toner layer as a protective layer of the magnetic field generating layer 94 by using a resin having excellent abrasion resistance such as a fluorine resin for the insulating layer 95. . The arrow in the figure indicates the direction of magnetization, and the magnetic field generating layer 94 may be a perpendicular magnetization film.

In addition to the above layer configuration examples, various layer configurations such as a configuration in which the functions of a plurality of layers are integrated into one layer and a layer configuration in which an intermediate layer is provided between layers to facilitate bonding between layers are possible. It is also possible to adopt a configuration in which the developing electrode effect is improved by disposing the developing layer in a predetermined layer.

FIG. 10 to FIG. 12 are schematic views showing the magnetized state of the magnetic field generating layer of the developing roller in the embodiment of the present invention.

FIG. 10 is a schematic view of the magnetized state of the magnetic field generating layer in the embodiment of the present invention. The magnetic field generating layer 101 is magnetized in a lattice shape such that N poles and S poles appear alternately. When magnetized in the horizontal direction so that the minimum magnetization reversal pitch is 50 to 100 [μm], a magnetic flux density of 500 [Gauss] or more is obtained on the magnetic field generating layer 101, and the toner can be stably held.
Further, when magnetized in the vertical direction, it is possible to obtain magnetization at a narrower pitch and higher magnetic flux density. Note that the magnetized state is not limited to the lattice shape, and a thin toner layer can be stably formed even when the lattice is inclined or a part of the lattice is magnetized.

FIG. 11 is a schematic view of the magnetized state of the magnetic field generating layer in the embodiment of the present invention. The magnetic field generating layer 111 is arranged such that N poles and S poles alternately appear in the circumferential direction or axial direction of the developing roller. It is magnetized. Minimum magnetization reversal pitch is 50-100
When magnetized in the horizontal direction so as to be [μm], a magnetic flux density of 500 [Gauss] or more is obtained on the magnetic field generating layer 111, and the toner can be stably held. With such a magnetized state, the number of magnetized poles is relatively small, and magnetizing is easy. Further, when magnetized in the vertical direction, it is possible to obtain magnetization at a narrower pitch and higher magnetic flux density.

FIG. 12 is a schematic view of a magnetized state of a magnetic field generating layer according to still another embodiment of the present invention. In the magnetic field generating layer 121, N poles and S poles alternately spirally appear along a developing roller. It is magnetized. Minimum magnetization reversal pitch is 50-100 [μ
m], the magnetic field generating layer
A magnetic flux density of 500 [Gauss] or more is obtained on the substrate 121, and the toner can be stably held. With such a magnetized state, the number of magnetized poles is relatively small, and magnetizing is easy. Further, when magnetized in the vertical direction, it is possible to obtain magnetization at a narrower pitch and higher magnetic flux density.

In addition to the above-mentioned magnetized state, a method of magnetizing the magnetization in a state in which the magnetization reversal directions are nearly random, a method of magnetizing the magnetic pole in accordance with the shape of the magnetized yoke such as a circle, and the like are possible. In this case, a stable toner thin layer can be formed on the developing roller by magnetizing the magnetic field generating layer so that the minimum magnetization reversal pitch is sufficiently small (for example, 100 [μm] or less). do not do. Further, the magnetization may be performed directly on the developing roller, or a film obtained by magnetizing the film-shaped magnetic field generating layer in advance may be appropriately disposed on the developing roller by bonding or the like.

Although the embodiments have been described above, the present invention can be widely applied not only to the above-described embodiments but also to a developing device such as an electrophotograph, and is particularly effective when applied to a printer, a copying machine, a facsimile, and a display.

[Effects of the Invention] As described above, according to the present invention, by developing with a developing roller having at least an elastic layer and a magnetic field generating layer, it is possible to provide a small-sized and low-cost developing device having a simple structure, There is an effect that a high-resolution and high-quality image can be stably formed. Also, contact development, pressure development,
It is possible to provide a developing device that can cope with any of the non-contact development. In particular, when the pressure contact development is used, the development electrode effect can be maximized to form the highest resolution image. Further, by providing a conductive layer or an insulating layer, the development electrode effect and the durability can be improved.

Therefore, the developing device of the present invention has an excellent effect of providing a developing device capable of obtaining a high-resolution image with less image defects such as background fogging and tailing in a one-component magnetic developing method. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus using a developing device of the present invention, 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, and FIG. FIG. 4 is a schematic cross-sectional view of an image forming apparatus using a developing device according to still another embodiment of the present invention. FIG. 4 is a diagram illustrating a layer configuration of a developing roller according to an embodiment of the present invention. FIG. 6 is a diagram showing a layer configuration of a developing roller in an example, FIG. 6 is a diagram showing a layer configuration of a developing roller in still another embodiment of the present invention, and FIG. 7 is a layer of a developing roller in still another embodiment of the present invention. FIG. 8 is a view showing a structure, FIG. 8 is a view showing a layer structure of a developing roller in still another embodiment of the present invention, FIG. 9 is a view showing a layer structure of a developing roller in still another embodiment of the present invention, FIG. 10 is a schematic view of the magnetized state of the magnetic field generating layer in the example of the present invention. , FIG. 11 is a schematic view of the magnetic state of the magnetic field generating layer in another embodiment of the present invention, further schematic view of the magnetic state of the magnetic field generating layer in another embodiment of FIG. 12 the present invention. DESCRIPTION OF SYMBOLS 1 ... Latent image carrier 7 ... Developing device 8 ... Toner 9 ... Developing roller 11 ... Elastic layer 12 ... Magnetic field generating layer

Continuation of the front page (56) References JP-A-61-199610 (JP, A) JP-A-62-223771 (JP, A) JP-A-61-83565 (JP, A) JP-A-1-281476 (JP) JP-A-58-49969 (JP, A) JP-A-60-4967 (JP, A) JP-A-60-250376 (JP, A) JP-A-61-141468 (JP, A) 61-66371 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/08-15/095

Claims (1)

(57) [Claims] 1. A developing device for transporting a one-component magnetic toner by a developing roller and developing the one-component magnetic toner on a latent image carrier, wherein the developing roller has an elastic layer and flexibility on the elastic layer. A magnetic field generating layer, wherein the magnetic field generating layer is magnetized in a lattice shape in which N poles and S poles alternately appear, and has a magnetization reversal pitch of 100 μm or less.