JPH03259287A - Developing device - Google Patents

Abstract

PURPOSE:To stabilize the carrying quantity of toner and to reduce the irregularity of density or ground fogging by using a developing roller having an elastic layer and a magnetic field generation layer and specifying a developing bias. CONSTITUTION:The developing roller 2 carrying the magnetic toner 1 is obtained by respectively providing the elastic layer 4 and the magnetic field generation layer 5 on the outside circumference of a base body 3 in a concentric circular state. Then, the magnetic toner 1 is directly held by the leakage magnetic flux of the outside circumference of the magnetic field generation layer 5. Besides, the toner 1 of a thin layer is carried by rotating the developing roller 2 in a state that it is regulated to proper quantity by a plate-like blade 6 constituted of a non-magnetic or magnetic metal or resin. Then, when the potential of an image part on a latent image carrier 9 is set to V1, the potential of a non-image part is set to V2 and the developing bias impressed between the carrier 9 and the roller 2 is set to Vb, an inequality I is satisfied by them. Thus, the carrying quantity of the toner is stabilized and the irregularity of the density is reduced. Besides, the ground fogging is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device that uses a one-component magnetic toner.

[Prior Art] As shown in Japanese Unexamined Patent Publication No. 63-31776, a conventional developing device uses a developing roller, which is a non-magnetic rotating cylinder with an elastic conductive layer and which houses a fixed or rotatable magnet inside, to produce a single component. The magnetic toner was conveyed and developed by pressing a developing roller against the latent image carrier.

In addition, other conventional developing devices that have been proposed include UPS-
4564285 and Japanese Patent Application Laid-Open No. 59-119371, an insulating layer is formed on a conductive substrate, a plurality of microelectrodes are dotted on the surface of the insulating layer, and either the insulating layer or the microelectrodes is A one-component magnetic toner is conveyed by a magnetic developing roller, and development is performed by bringing the developing roller into contact with or close to a latent image carrier.

[Problems to be Solved by the Invention] However, in the former example of the prior art described above, the developing roller is constituted by a developing sleeve and a magnetic roller, resulting in a complicated structure, large size, and high cost. Furthermore, although the toner holding power is ensured and there is little ground force blur, this precept is difficult to form a thin and uniform toner layer due to the low limit of miniaturization of the magnetic pole pitch, and the concentration due to fluctuations in the magnetic field of the magnet roller. The problem is that there are many causes of image quality deterioration such as unevenness and trailing at the edges of line images.

In addition, with the latter conventional technology, it is difficult to form an insulating layer whose surface is dotted with micromagnets, resulting in high costs.
Furthermore, there is a problem in that density unevenness occurs due to non-uniform magnetic force applied to the toner layer.

Furthermore, since sufficient toner retention force S is not obtained, uncharged toner or toner charged to the opposite polarity to the normal one is developed in the non-image area of the latent image carrier (static blur), and images such as electrophotography are formed. Even if the toner is not transferred to the recording paper in the device, a lot of toner is unnecessarily discarded, which is not only uneconomical but also requires an excessive amount of space in the waste toner container, making the image forming device larger. . In addition, even if the toner is charged to the correct polarity, when the toner comes into contact with the latent image carrier in the development area, the toner with a large charge I per unit volume will adhere to the non-image area due to image force etc., resulting in recording failure. This has the problem of causing soil burrs that remain on the paper.

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 in which toner transport I is stable, density unevenness is small, and ground force blur does not occur. Still another object is to provide a developing device that can reduce unnecessary waste toner. Still another object is to provide a developing device that has a simple structure and is applicable to small, low-cost image forming apparatuses. Still another object is to provide a developing device with high resolution and high image quality.

[Means for Solving the Problems] The developing device of the present invention has a developing roller that conveys a one-component magnetic toner and a latent image carrier that are opposed to each other in a developing area with a gap equal to or less than the thickness of the developer layer. , a developing device for developing a one-component magnetic toner, wherein the developing roller has at least an elastic layer and a magnetic field generating layer, and the potential of the image area on the latent image carrier is V1, the potential of the non-image area is V2, and the potential of the non-image area is V2; It is characterized in that the formula (*) is satisfied when the developing bias applied between the latent image carrier and the developing roller is Vb.

Further, in the developing device of the present invention, a developing roller that conveys a one-component magnetic toner is brought into pressure contact with a latent image carrier in a developing area to develop the one-component magnetic toner. and satisfies formula (*).

Further, in the developing device of the present invention, the developing roller has a conductive layer, the conductive layer has at least a developing bias, and the developing roller has a formula (
*) is characterized by satisfying the following.

[Function] According to the above configuration of the present invention, by configuring the developing roller with a single rotating body, it is possible not only to simplify the structure of the developing roller but also to obtain a small, lightweight, and low-cost developing roller. . In addition, by magnetizing the thin magnetic field generation layer at a minute pitch, a uniform and thin toner layer (
Alternatively, it is possible to form a magnetic brush thin layer with a minute pitch, reduce density unevenness caused by fluctuations in the magnetic field and fluctuations in the toner layer thickness, and perform high-resolution development.

Further, according to the above configuration of the present invention, by holding the toner with the uniform and sufficiently strong magnetic force of the magnetic field generation layer, the ground force blur that tends to occur when the toner comes into contact with the latent image carrier is eliminated. It is possible to widen the range of development bias to be prevented and efficiently reduce ground force blur. Furthermore, by reducing soil blurring and reducing unnecessary waste toner, image forming apparatuses using the developing device of the present invention can be made smaller, lower cost, and require less maintenance. Costs can also be reduced.

Further, according to the above configuration of the present invention, even when the thin film member is pressed against the latent image carrier for development, development can be performed with high resolution and high printing quality without any ground force blur.

Furthermore, by providing a conductive layer on the developing roller,
By arranging the developing electrode very close to the latent image carrier, it is possible to perform high-temperature development with a low developing bias, and to obtain a high-resolution image due to the developing electrode effect.

Hereinafter, the details of the present invention will be shown by examples.

[Example] FIG. 1 is a cross-sectional schematic diagram of an example of the developing device of the present invention. The developing roller 2 that conveys the magnetic toner 1 is made of elastic rubber [4 and
The magnetic field generating layers 5 each having a thickness of about 10 [μm] are arranged in concentric circles, and are formed by applying a magnetic paint containing a magnetic material dispersed in a binder solution. The toner 1 of NM is directly held therein, and the developing roller 2 is rotated to transport the toner 1 of NM while controlling the appropriate amount with a plate-shaped blade 6 made of non-magnetic or magnetic metal or resin. The toner 1 is transported to a development area where a latent image carrier 9 having an electrostatic image holding layer 8 formed on a support electrode 7 and a developing roller 2 are arranged with a gap narrower than the layer thickness of the toner 1, and the toner is The layer contacts the latent image carrier 9. Further, the toner 1 is formed by the potential contrast of the latent image carrier 9 and the bias applied between the supporting electrode 7 of the latent image carrier 9 and the elastic layer 4 of the developing roller 2 by the developing bias applying means 10. Depending on the developing electric field, the electrostatic latent image adheres to the latent image carrier 9 and becomes visible.

Using a developing device as shown in FIG. When 10,000 sheets of line latent images, character latent images, and solid latent images of 600 [DPI] were continuously developed at a developing bias of Vb = -400 [V], the line images of 600 [DPI] became thicker. It was possible to stably form a high-temperature solid image with an OD value of 1.4 or more without any tailing or blurring at the edges of the image.

FIG. 2 is a cross-sectional schematic diagram of another embodiment of the developing device of the present invention. Components with substantially the same names as those in FIG. 1 are given the same numbers and their explanations will be omitted.

The developing roller 2 is pressed against the latent image carrier 9 at a predetermined pressure, and an appropriate amount of thinned toner 1 is pressed against the developing roller 2 by an elastic blade 26 in the form of a thin plate spring made of non-magnetic or magnetic metal or resin. When the electrostatic latent image is conveyed to the latent image carrier 9, it adheres to the latent image carrier 9 depending on the potential contrast of the latent image carrier 9 and the developing electric field formed by the developing bias applying means 10, and the electrostatic latent image is visualized.

Using a developing device as shown in FIG. Develop the image with full bias Vb = -250 [V] - (-1600 []) PI] line latent image, character latent image and solid latent image at 100
After continuously developing 00 sheets, the result was 600 [DP process]
Line images are stably formed without line thickening,
It is possible to stably form a high-density solid image with an OD value of 1.4 or higher without causing any trailing or blurring at the edges of the image, and without excessive toner development at the edges of the image. did it.

In the embodiments of FIGS. 1 and 2, the elastic layer 4 can be composed of materials such as natural rubber, silicone rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, and the like.

The elastic layer 4 can be made of rubber, foam, sponge, etc., and preferably has a thickness of 500 μm or more. It is formed by dispersing known magnetic powder as a material in a binder solution together with additives and applying a magnetic paint. Furthermore, the toner used in the present invention includes:
All toners known as one-component magnetic toners can be used, including resin-based toners and wax-based toners. It is made by adding agents and other additives, such as by pulverization or polymerization methods.

In addition, in FIGS. 1 and 2, the present invention is not limited only to the configurations shown in the figures. Further, although the arrows indicate the rotation direction of each member, this does not limit the present invention.Furthermore, the latent image carrier 9 can also be in the form of a belt, and the developing method can be divided into normal development and reversal development. can be used without asking.

FIG. 3 is a diagram showing the layer structure of a developing roller in an example of the present invention. An elastic M32 mainly composed of elastic resin is formed on a base 31 such as a shaft, a conductive layer 33 is formed on the elastic layer 32, a magnetic field generation layer 34 is formed on the conductive layer 33, and the magnetic field generation layer 34 is formed on the conductive layer 33. An insulating layer 35 is formed thereon to form a developing roller. By magnetizing the magnetic field generation layer 34 in the horizontal direction so that the magnetization reversal pitch is 100 [μm] or less, a minute toner chain of magnetic toner L is formed on the magnetic field generation layer 34, which is a thin and stable layer. A toner layer is obtained. In addition, by magnetizing the magnetic field generation layer 34 in the perpendicular direction (not shown), the magnetization reversal pitch can be made denser to the particle size of the toner (approximately 10 [μm1]), and the magnetization can be uniformly formed in one or two layers. It is also possible to form a thin layer of toner, and since a strong magnetic field can be obtained on the surface of the magnetic field generation layer, it is possible to reduce the magnetic powder content of magnetic toner 1, making it easier to manufacture the toner and improving fixing properties. Note that the arrow in the figure indicates the direction of magnetization.

Further, as the material of the conductive layer 33, A1. In addition to a material containing a conductive metal such as Ni, a conductive material such as carbon black can be used, and it can be formed by means such as adhesion, coating, plating, etc.

Further, only when the magnetic field generating layer 34 is vertically magnetized, a large magnetic field can be obtained on the surface of the insulating layer 35 by providing a magnetic circuit of the magnetic field generating layer 34 with a configuration in which the conductive layer 33 includes a soft magnetic material. be able to. Furthermore, by providing the insulating layer 35 at the contact portion with the toner 1, it is possible not only to control the charging polarity and the amount of charge of the toner 1, but also to apply a resin with excellent wear resistance such as fluorocarbon resin to the insulating layer 35. It can also be used as a protective layer for the magnetic field generation layer 34.

Although examples of the layer structure have been described above, the developing roller in the developing device of the present invention includes at least an elastic layer and a magnetic field generating layer as constituent elements, and either the elastic layer or the magnetic field generating layer has electrical conductivity. or have a separate conductive layer. In addition, there is a base that ensures the strength of the roller,
It is possible to add as a component an insulating layer that improves the charging properties of the toner. In addition, a protective layer can be provided to improve durability, an intermediate layer can be provided to improve moldability, and it is also possible to combine the functions of multiple layers into a single layer. It is. Furthermore, the magnetic field generation layer 34 can be used in various magnetized states such as line magnetization, grid magnetization, and spiral magnetization. Alternatively, a magnetic field generating layer in the form of a film that has been magnetized in advance may be appropriately disposed on the developing roller by means such as adhesion.

FIG. 4 is a diagram showing the amount of developed toner in an image area and a non-image area in an example in which the developing device of the present invention was used and the conditions of the developing bias were changed. The horizontal axis is Vb/(V1+V2)
l, and the vertical axis is the image area 4 formed on the latent image carrier.
The developed toner amount 41 of the 0 image area, which represents the developed toner amount of the 1 and non-image areas 42, rises from the level of the developing bias corresponding to the toner retention force and eventually becomes saturated.

The non-image area is 1.0>l Vb/(V1+V2
) In the range of l>0.5, the amount of developing toner is small and is an acceptable amount. Therefore, in the developing device of the present invention, if vb is set within the developing bias range of V1+V2≦IVbl≦IV2+ (ne), a good image without blurring can be obtained.

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, by developing using a developing roller having at least an elastic layer and a magnetic field generating layer and setting a developing bias that satisfies the formula (*), the structure can be improved. Although it is a simple, small and low-cost developing device, it has the advantage of being able to stably form images with a stable toner transport amount and less temperature unevenness and ground force blur. In particular, by forming a magnetic field with a minute pitch and holding the toner uniformly and with sufficient strength on the developing roller, the range of the developing bias that prevents blurring caused by the toner coming into contact with the latent image carrier is expanded, and the contact A developing device capable of handling both development and pressure development can be provided. Furthermore, by setting vb to satisfy formula (*) in a steady state, ■1 and V2
It is possible to provide a highly reliable developing device by reducing changes in developing characteristics caused by changes in . moreover,
Pressure development maximizes the development electrode effect,
It is possible to form the highest resolution image.

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 one-component magnetic development. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional overview of an embodiment of the developing device of the present invention, FIG. 2 is a cross-sectional overview of another example of the developing device of the present invention, and FIG. 3 is a cross-sectional overview of an embodiment of the developing device of the present invention. FIG. 4 is a diagram showing the layer structure of the developing roller in the example, and FIG. 4 is a diagram showing the optical flux of the image area and non-image area of the example, which was carried out using the developing device of the present invention and changing the conditions of the developing bias. It is. 1... Toner; 2... Developing roller 3...
・Substrate; 4...Elastic layer 5...Magnetic field generation layer
9...Latent image carrier 10...Development bias applying means 33...Conductive layer or more

Claims (3)

[Claims] (1) A developing device for developing the one-component magnetic toner, in which a developing roller that conveys the one-component magnetic toner and a latent image carrier are held facing each other in a developing area with a gap equal to or less than the thickness of the developer layer, and the one-component magnetic toner is developed. Development in which the developing roller has at least an elastic layer and a magnetic field generating layer, and a potential of an image area on the latent image carrier is V1, a potential of a non-image area is V2, and a potential is applied between the latent image carrier and the developing roller. A developing device that satisfies formula (*) when bias is Vb. (|V1+V2|/2)≦|Vb|≦|V2|(*) (2) A developing device that develops the one-component magnetic toner by pressing a developing roller that conveys the one-component magnetic toner against a latent image carrier in a developing area, wherein the developing roller conveys at least an elastic layer and a magnetic field generating layer. A developing device characterized in that it has the following characteristics and satisfies the formula (*). (3) The developing device according to claim 1 or 2, wherein the developing roller has a conductive layer and applies a developing bias to the conductive layer.