JPH03259289A - Developing device - Google Patents

Abstract

PURPOSE:To stably form an image of high resolution and high quality by disposing a magnetic field generation layer to the cylindrical thin film member of a developing device which makes carried toner contact with a latent image carrier, gives an alternate electric field and executs developing. CONSTITUTION:A developing roller 2 carrying the magnetic toner 1 is constituted of a driving roller 3 which is driven to be rotated and provided with a frictional part or the like on the outside circumference, and the cylindrical thin film member 4 which is externally provided to the outside circumference of the roller 3 by leaving excess length. Then, the member 4 has constitution that the magnetic field generation layer 6 is disposed on a base body 5 which has elasticity and electrical conductivity. Besides, the toner 1 is held by the leakage magnetic flux of the outside circumference of the magnetic field generation layer 6. Then, the toner 1 of a thin film is carried by rotating the roller 2 in a state that the toner is regulated to proper quantity by a plate-like blade 7 constituted of a non-magnetic or magnetic metal or resin. Thus, the irregularity of the density caused by the change of the layer thickness of the toner is reduced and ground fogging is reduced by adding the alternate electric field to a developing area while holding the toner to the roller 2 by magnetic force. As the result, the developing of the high resolution and the high printing quality is realized.

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 disclosed in Japanese Unexamined Patent Publication No. 64-65579, a conventional developing device elastically brings the excess portion of a cylindrical thin film member having an excess circumferential length with respect to a drive roller into close contact with a photoreceptor. Let me,
It was used to transport and develop non-magnetic toner.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the force for holding the toner on the developing roller is very weak due to electrostatic mirror image force and adhesive force, and it is difficult to make the toner conveying tray uniform. is difficult,
The problem is that there are many causes of image quality deterioration such as temperature unevenness and trailing at the edges of line images. Furthermore, when toner is developed on a latent image bearing member such as a photoreceptor, uncharged toner or toner with a non-regular polarity is developed in the non-image area, and there is significant ground blur (toner is not formed in the non-image area) on the latent image bearing member. In image forming devices such as copying machines, only toner of the correct polarity is transferred to the recording paper, but many toners are not transferred and are discarded unnecessarily.
Not only is this uneconomical, but the waste toner container occupies an excessive amount of space, making the image forming apparatus larger. Furthermore, 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 amount of charge per unit volume will adhere to the non-image area due to image force, etc. This was the cause of soil buri remaining in the soil.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and an object thereof is to provide a developing device in which the amount of toner conveyed 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 conveys a one-component magnetic toner to a developing area by a developing roller, and applies an alternating electric field to the developing area while transferring the one-component magnetic toner to a latent image carrier. A developing device that performs development, wherein the developing roller has at least a cylindrical thin film member and a drive roller that contacts at least a portion of the inner circumferential side of the cylindrical thin film member, and the thin film member has at least a magnetic field generating layer. shall be.

Further, the developing device of the present invention is characterized in that the thin film member is brought into pressure contact with the latent image carrier.

Further, the developing device of the present invention is characterized in that the thin film member has a conductive layer.

Further, the developing device of the present invention is characterized in that the thin film member has an insulating layer.

[Function] According to the above structure of the present invention, it is possible to convey the toner near the surface of the thin magnetic field generation layer, and not only simplify the structure of the developing roller but also obtain a small, lightweight, and low-cost developing roller. can. In addition, by magnetizing the thin magnetic field generating layer at a minute pitch, a uniform and thin toner layer (or a thin magnetic brush layer at a minute pitch) can be formed on the developing roller.
Reduces density unevenness due to variations in toner layer thickness, and applies alternating electric fields to the developing area while holding the toner on the developing roller by magnetic force, reducing ground force blurring and developing with high resolution and high print quality. 6 Furthermore, by reducing soil burr and reducing unnecessary waste toner,
The image forming apparatus can be made smaller and lower in cost and requires less maintenance, and it is also possible to reduce toner consumption and running costs.

Further, according to the above configuration of the present invention, the thin film member 711
Even when the development is carried out in pressure contact with the image carrier, it is possible to perform development with high resolution and high printing quality without any background blur.

Furthermore, by providing an independent conductive layer on the thin film member, the developing electrode effect can be enhanced and a high-resolution image can be obtained.

Further, by providing an insulating layer on the thin film member, the frictional charging between the thin film member and the toner can be stably performed, and temporal fluctuations in the degree of development immersion can be reduced.

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.
It is a diagram. The developing roller 2 that conveys the magnetic toner 1 is driven by a driving roller 3 that is rotationally driven and has a friction portion on the outer periphery.
and a cylindrical thin film member 4 that is wrapped around the drive roller 3 with a surplus left on its outer periphery. A cylindrical thin film member 4 has a magnetic field generating layer 6 on a base 5 having elasticity and conductivity.
The magnetic toner 1 is held by leakage magnetic flux around the outer periphery of the magnetic field generating layer 6, and is regulated to an appropriate plate by a plate-shaped blade 7 made of non-magnetic or magnetic metal or resin. In this state, rotate the developing roller 2 to apply a thin layer of toner 1.
It is used to transport. The toner 1 transported to the development area where the latent image carrier 8 composed of the supporting electrode 9 and the electrostatic image holding layer 10 and the developing roller 2 are close to each other is controlled by the potential contrast of the latent image carrier 8 and the DC development bias. The electrostatic latent image adheres to the latent image carrier 8 according to the developing electric field formed by the applying means 11 and the AC bias applying means 12, and the electrostatic latent image is visualized.

Using a developing device as shown in FIG.
PI] line image, character image, and solid image 1
When continuously formed over 0,000 sheets, 600 [D
PI] line image is stably formed without line thickening, there is no trailing or blurring at the edge of the image, and the OD value is 1.
It is possible to stably form a solid image at a high temperature of 4 or higher, and there is no ground force blur in the image transferred onto the recording paper, and there is also no ground force blur on the latent image carrier, significantly reducing the amount of waste toner. We were able to.

FIG. 2 is a cross-sectional schematic view of another embodiment of the developing device of the present invention, and members having substantially the same functions, names, and names as those in FIG.

The developing roller 2 that conveys the toner 1 generates a magnetic field.
The magnetic toner 1 is held directly on the developing roller 2 by leakage magnetic flux on the outer periphery of the magnetic toner 16, and is thinned to an appropriate thickness by a thin plate spring-like elastic blade 27 made of non-magnetic or magnetic metal or resin, and then developed. Rotate roller 2 to apply a thin layer of toner 1.
It is used to transport.

The developing roller 2 is pressed against the latent image carrier 8 at a predetermined pressure, and when the toner 1 on the developing roller 2 is conveyed to the pressure contact portion, the potential contrast of the latent image carrier 8 and the DC developing bias applying means 11 are The electrostatic latent image is adhered to the latent image carrier 8 in accordance with the developing electric field formed by the AC developing bias applying means 12, and the electrostatic latent image is visualized.

Using a developing device as shown in FIG.
When line images, character images, and solid images of [DPI] were continuously formed on 10,000 sheets, the result was 600 [DPI].
DPI] line images are stably formed without line thickening, the line pair image has the highest resolution, there is no tailing or blurring at the image edges, and it is a high-temperature solid image with an OD value of 1.4 or higher. was able to be stably formed, and there was no background blur in the image transferred onto the recording paper, and there was also no background blur on the latent image carrier, making it possible to significantly reduce the amount of waste toner.

In Figures 1 and 2, the drive roller 3 has a friction part made of natural rubber, silicone rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, etc. on the outer periphery of a resin or metal shaft. The thin film member 4 is pressed against the drive roller 3 to transmit rotational driving force.

Further, the base body 5 of the thin film member 4 may be made of phosphor bronze, stainless steel,
A metal thin film such as nickel or a resin thin film material such as nylon, polyimide, or polyethylene terephthalate in which a conductive material such as carbon black is dispersed can be used, and the thickness of the thin film member 4 varies depending on the material, but it is suitable for carrying a latent image. In order to obtain sufficient pressure contact with the body, the pressure must be 10 to 500 μm.
It is preferable that the magnetic field generation layer 6 is approximately
Known magnetic recording materials and magnet materials can be used; more specifically, Fe, Ni, Co,
Magnetic materials containing at least one element among Mn, such as y-Fe203, Ba-Fe, Ni-C
o, Co-Cr, Mn-Al, etc. can be used, and the film thickness is 1
00 [μm] or less, preferably around 10 [μm] 1, and the minimum magnetization reversal pitch is 100 [μm] or less to uniformly thin the toner, and at the same time, change the amount of toner conveyance on the developing roller by forming a magnetic brush. It is possible to reduce density unevenness by suppressing the pitch to a minute pitch. Further, as the toner used in the present invention, all toners known as one-component magnetic toners can be used, and the composition of the developer may be either resin-based toner or wax-based toner, as is known in the art. It is made by adding magnetic powder, colorants, external additives, and other additives to resin, and is created by pulverization or polymerization methods.

In addition, in FIGS. 1 and 2, the present invention is not limited to the configurations shown in the figures, and although the arrows indicate the rotation directions of the respective members, the present invention is not limited to the configurations shown in the figures. The latent image carrier 9 can also be in the form of a belt,
The developing method can be used regardless of whether it is regular development or reversal development.

FIG. 3 is a diagram showing the layer structure of a thin film member in an embodiment of the present invention, in which a conductive layer 32 is formed on an elastic base 31, a magnetic field generation H33 is formed on the conductive layer 32, and a magnetic field H33 is formed on the conductive layer 32. An insulating layer M34 is formed on the generation layer 33 to form a thin film member. The magnetic field generation layer 33 has a magnetization reversal pitch of 1
By horizontally magnetizing the magnetic toner 1 to a value of 00 [μm] or less, a minute toner chain of the magnetic toner 1 is formed on the magnetic field generating layer 33, and a thin and stable toner layer is obtained. In addition, by magnetizing the magnetic field generation layer 33 in the perpendicular direction (not shown), the magnetization reversal pitch can be made denser to about the toner particle size (about 10 [μm1]), and 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. It is. Note that the arrows in the figure indicate the direction of magnetization, and as the material of the conductive layer 32, in addition to materials containing conductive metals such as A1 and Ni, conductive materials such as carbon black can be used. , it can be formed by means such as adhesion, coating, plating, etc. Further, only when the magnetic field generating layer 33 is vertically magnetized, a large magnetic field can be obtained on the surface of the insulating layer 34 by making the conductive layer 32 include a soft magnetic material and providing a magnetic circuit for the magnetic field generating layer 33. be able to. In addition, the insulating layer 34
By providing the contact area 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 generate a magnetic field by using a resin with excellent wear resistance such as fluorocarbon resin for the insulating layer 34. It can also serve as a protective layer for layer 33.

Although examples of the layer structure have been described above, the developing roller in the developing device of the present invention is as follows: 1. It consists of at least a thin layer member 4 that has elasticity and conductivity and includes a magnetic field generating layer 33 as a component, and a drive roller 3 that drives the thin layer member 4, and an insulating layer 34 that improves the charging property of the toner. A separate conductive layer 32 can be added as a component. In addition, a protective layer can be provided to improve durability, an intermediate layer can be provided to improve moldability, and
A configuration in which functions of multiple layers are combined into a single layer is also possible.

Furthermore, the magnetic field generation layer 33 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 example in which the developing device of the present invention was used and the developing bias conditions were changed.

The horizontal axis represents the contrast potential V, which is the difference between the potential of the image area and the potential of the developing roller due to the DC developing bias, and the vertical axis represents the developed toner ID of the image formed on the latent image carrier, and the curve in the figure is the V-D characteristic. FIG. 4 uses the difference VpP between the peak and bottom of the alternating current component of the developing bias as a parameter, and shows that the slope of the V-D characteristic tends to become steeper when 1 Vppl is increased. Therefore, it is recommended that the developing device be suitable for copying machines etc. that require high gradation.
1≧300 It is desirable that ≦1Vppl≦600 [V].

FIG. 5 is a diagram showing the amount of developed toner in an example in which the developing device of the present invention was used and other developing bias conditions were changed. The horizontal axis is the contrast potential V, which is the difference between the potential of the image area and the potential of the developing roller due to the DC developing bias, and the vertical axis is the developing toner jID of the image formed on the latent image carrier.
The curve in the figure is the V-D characteristic. FIG. 5 uses the frequency f of the AC component of the developing bias as a parameter, and shows that the slope of the V-D characteristic tends to become steeper as f becomes larger. Therefore, for a developing device suitable for copying machines and the like that require gradation, it is desirable that f≦1200 [H2], and the temperature of each pixel is binary, and the temperature of each binary value is stable. A developing device suitable for a laser beam printer etc. where a wide area is desirable has f≧600.
[H2] is desirable.

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 toner conveyed by the developing roller consisting of a cylindrical thin layer member and a driving roller is brought into contact with a latent image carrier and developed by applying an alternating electric field. By arranging a magnetic field generation layer on a cylindrical thin film member in the device, it is possible to provide a developing device with a simple structure, small size and low cost, which can stably form high resolution and high quality images. It has this effect. Further, it has the effect that ground force blur, which occurs noticeably when toner comes into contact with the latent image carrier, can be prevented by the magnetic binding force generated by alternating electric fields and minute pitch magnetic fields. Furthermore, by stably supplying the N-layer toner to the development area with a --like magnetic binding force, it is possible to provide a developing device that is compatible with both contact development and pressure development, and in particular, it is possible to provide a development device that is compatible with both contact development and pressure development. It is possible to maximize the development electrode effect and form the highest resolution image. Furthermore, since contact development is performed by supplying toner in a thin layer to the development area, the effect of alternating electrolysis can be obtained even if the voltage of the AC component of the development bias is lower than in conventional technology, making it possible to reduce the size and cost of the power supply. It has the effect of being. moreover,
By providing a conductive layer or an insulating layer, it is possible to improve the developing electrode effect and durability.

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 schematic view of an embodiment of the developing device of the present invention, and is a 21st! 1 is a schematic cross-sectional view of another embodiment of the developing device of the present invention, FIG. 3 is a diagram showing the layer structure of the thin film member in the embodiment of the present invention, and FIG. 4 is a diagram of the developing device of the present invention. FIG. 5 is a diagram showing the amount of developed toner in an example in which the developing device of the present invention was used and the conditions of the developing bias were changed. FIG. FIG. 3 is a diagram showing the amount of toner. 1: Toner 2: Developing roller 3: Drive roller 4: Thin film member 6: Magnetic field generating layer 8: ? W image carrier 10: DC development bias application means 11: AC development bias application means 33: Conductive layer 35: Insulating layer or above

Claims (4)

[Claims] (1) In a developing device that conveys a one-component magnetic toner to a developing area by a developing roller and develops the one-component magnetic toner onto a latent image carrier while applying an alternating electric field to the first developing area, the developing roller is arranged in a cylinder. 1. A developing device comprising a thin film member having a shape of cylindrical shape and a drive roller that contacts at least a portion of an inner circumferential side of the cylindrical thin film member, the thin film member having at least a magnetic field generating layer. (2) The developing device according to claim 1, wherein the thin film member is pressed against the latent image carrier. (3) The developing device according to claim 1 or 2, wherein the thin film member has a conductive layer. (4) The developing device according to claim 1, 2 or 3, wherein the thin film member has an insulating layer.