JPH03259288A - Developing device - Google Patents

Abstract

PURPOSE:To stabilize the carrying quantity of toner and to reduce the irregularity of density or specially, ground fogging by disposing a magnetic field generation layer to a cylindrical thin film member, securing toner holding force and specifying a developing bias at the same time. CONSTITUTION:A developing roller 2 carrying the 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. Besides, the member 4 has such constitution that the magnetic field generation layer 6 is disposed on a base body 5 which has elasticity and electrical conductivity. Then, when the potential of an image part on a latent image carrier 8 is set to V1, the potential of a non-image part is set to V2 and the developing bias impressed between the carrier 8 and the roller 2 is set to Vb, an inequality 1 is satisfied. 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 disclosed in Japanese Patent Application Laid-Open No. 64-65579, a conventional developing device elastically attaches an excess portion of a cylindrical thin film member sleeve having an excess circumferential length to a drive roller onto a photoreceptor. By bringing them into close contact, it was possible to transport and develop non-magnetic toner.

[Problem M to be solved by the invention] However, in the above-mentioned conventional technology, the force for holding the toner on the developing roller depends on electrostatic mirror image force and adhesive force, so it is difficult to make the amount of toner conveyed uniform. In addition, because the toner retention force is small, 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), resulting in image formation such as electrophotography. Even if the toner is not transferred to recording paper in the device, much toner is unnecessarily discarded, which is not only uneconomical, but also requires a sufficient space for 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 amount of charge per unit volume will adhere to the non-image area due to image force, etc. This had the problem of causing soil burrs that remained on the R paper.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a current fII device in which the amount of toner conveyed is stable, density unevenness is small, and soil blur does not occur. In particular, it is an object of the present invention to provide a developing device that provides a margin in the range of the developing bias Vb, which is limited as a measure against background blur, and that allows high image quality to be obtained even with a low developing bias. 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] A developing device of the present invention is a developing device in which a developing roller conveys a one-component magnetic toner to a developing area and develops the one-component magnetic toner onto a latent image carrier. the thin film member has at least a drive roller that contacts at least a portion of the inner circumferential side of the cylindrical thin film member, the thin film member has at least a magnetic field generating layer, and the image area on the latent image carrier is The potential is V1, the potential of the non-image area is V2, and the developing bias applied between the latent image carrier and the developing roller is V.
b, it is characterized by satisfying formula (*).

lV1+V2 ≦ l Vb l ≦ IV21 (ne)
Further, the developing device of the present invention is characterized in that the thin film member is pressed against the latent image carrier and satisfies formula (*).

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

[Function] According to the above configuration of the present invention, not only the structure of the developing roller can be simplified, but also a developing roller that is small, lightweight, and low cost can be obtained. In addition, by magnetizing the thin magnetic field generation layer at a minute pitch, it is possible to form a uniform and thin toner layer (or a thin layer of magnetic brush at a minute pitch) on the developing roller, which prevents fluctuations in the magnetic field. It is possible to reduce density unevenness caused by variations in toner layer thickness, and to perform development with high resolution and high print quality.

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 the developing bias that is limited in order to prevent blurring, and to 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, reducing toner consumption and reducing running time. 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 toner 1 is constituted by a driving roller 3 that is rotationally driven and has a friction portion on its outer periphery, and a cylindrical thin film member 4 that is sheathed with a surplus portion left on the outer periphery of the driving roller 3. The cylindrical thin film member 4 has a structure in which a magnetic field generating layer 6 is disposed on a base body 5 having elasticity and conductivity, and the magnetic toner 1 is retained by the leakage magnetic flux around the outer periphery of the magnetic field generating layer 6, and the non-magnetic toner is retained. Alternatively, a thin layer of toner 1 is conveyed by rotating the developing roller 2 while regulating the appropriate amount with a plate-shaped blade 7 made of magnetic metal or resin. Then, the supporting electrode 9 and the electrostatic image holding layer 1
The toner 1 conveyed to the development gap portion where the latent image carrier 8 and the developing roller 2 are close to each other is affected by the potential contrast of the latent image carrier 8 and the developing bias applying means 1.
1, the electrostatic latent image adheres to the latent image carrier 8 and is visualized.

Using a developing device as shown in FIG. When 600 [DPI] line images, character images, and solid images were continuously formed on 10,000 sheets at a developing bias Vb = -400 [V], the 600 [DPI] line images were stable without line thickening. It is possible to stably form a high-density solid image with an OD value of 1.4 or more without any trailing or background blurring at the edges of the image, and of course there is no background blurring on the recording paper. There was no soil burr on the body, and the amount of waste toner was significantly reduced.

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 transfers the magnetic toner 1 to the developing roller 2 due to leakage magnetic flux around the outer periphery of the magnetic field generating layer 6.
The toner 1 is held directly on top of the toner, is thinned to an appropriate amount by a thin plate spring-like elastic blade 27 made of non-magnetic or magnetic metal or resin, and is conveyed in a thin layer by rotating the developing roller 2. be.

The developing roller 2 is pressed against the latent image carrier 8 with 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 developing bias applying means 11 are applied. The toner 1 charged according to the developing electric field adheres to the latent image carrier 8, and the electrostatic latent image is visualized.

Using a developing device as shown in FIG. Image development bias V
b=-250 [V] When 600 [DPI] line images, character images, and solid images were continuously formed on 10,000 sheets, the 600 [DPI] line images were stably formed without line thickening. The resolution of the paired images is the highest, there is no trailing at the edges of the image, there is no ground blurring, it is possible to stably form a high density solid image with an OD value of 1.4 or more, and there is no ground blurring on the recording paper. Not only that, but there was no smudging on the latent image carrier, and the amount of waste toner could be significantly reduced.

In FIGS. 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 thin film member 4 can be made of a metal thin film such as phosphor bronze, stainless steel, or nickel, or a resin thin film material such as nylon, polyimide, or polyethylene terephthalate. In order to obtain sufficient pressure contact with the body, it is preferable to have a thickness of about 10 to 500 [μm].Furthermore, the magnetic field generation layer 6 can be made of a known magnetic recording material or magnet material, and even more For details, see Fe, Ni, Co, M
A magnetic material containing at least one element among n, such as 7 Fe2O3, Ba-Fe, N
i-Co, Co-Cr, Mn-Al, etc. can be used, and the film thickness is 100 [μm] or less, preferably around 10 [μm], and the minimum magnetization reversal pitch is 100 [μm] or less to make the toner uniform. At the same time, variations in the amount of toner conveyed on the developing roller due to the formation of the magnetic brush can be suppressed to a minute pitch, thereby reducing temperature unevenness. moreover,
The toner used in the present invention can be any toner known as a one-component magnetic toner, and may be either a resin-based toner or a wax-based toner. It is made by adding magnetic powder, coloring agents, external additives, and other additives, and is made 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 end holder 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 the thin film member 4 of the developing roller 2 in an embodiment of the present invention.
A conductive layer 32 is formed on the conductive layer 1, a magnetic field generation layer 33 is formed on the conductive layer 32, and an insulating yfI3 is further formed on the magnetic field generation layer 33.
4 to form a developing roller. By magnetizing the magnetic field generation layer 33 in the horizontal direction so that the magnetization reversal pitch is 100 [μm] or less, a minute toner chain of the magnetic toner 1 is formed on the magnetic field generation layer 33, which is a thin and stable layer. A toner layer is obtained. Furthermore, by magnetizing the magnetic field generation layer 33 in the perpendicular direction (not shown),
It is possible to increase the magnetization reversal pitch to the toner particle size (around 10 [μm1)], and evenly distribute the toner in one layer.
It is also possible to form a thin layer, 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 the magnetic toner 1, facilitating toner production and improving fixing properties. . 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 providing a magnetic circuit of the magnetic field generating layer 33 with a configuration in which the conductive layer 32 includes a soft magnetic material. be able to. Further, by providing the insulating layer 34 at the contact portion with the magnetic toner l, the charge polarity I! of the magnetic toner l can be changed. Not only can fm and the amount of charge be controlled, but also a protective layer for the magnetic field generation layer 33 can be used by using a resin with excellent wear resistance such as fluorocarbon resin for the insulating 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 the thin layer member 4 which has elasticity and conductivity and includes the magnetic field generating layer 33 as a component; It is possible to add an insulating layer 34 and an independent conductive layer 32 as constituent elements to improve the charging property of the toner. 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 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 tg axis is 1Vb/ (V1+V
2) I, and the vertical axis represents the amount of developing toner in the image area 41 and non-image area 42 formed on the latent image carrier.
The amount of developed toner 41 in the image area rises from the level of the developing bias corresponding to the toner retention force and eventually becomes saturated. The non-image area is 1>l Vb/ (V1+V2)l
>0.5, the amount of developed toner is small and is an acceptable amount.

Therefore, in the developing device of the present invention, if Vb is set within the range of the developing bias (lV1+V21≦1Vbl≦1V21 C lines), a good image without any 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, in a developing device that develops toner conveyed by a developing roller consisting of a cylindrical thin layer member and a drive roller, the cylindrical By arranging a magnetic field generation layer on a shaped thin film member to ensure toner retention and setting a developing bias that satisfies the formula (*), the amount of toner conveyed is stable, and temperature unevenness and especially soil blurring are prevented. It is possible to provide a developing device with a small number of developing devices, reduce unnecessary waste toner, and provide a developing device with low running costs. It is possible to provide a developing device with a simple structure, small size, and low cost. It has the effect of stably forming high-quality images.In addition, it is possible to provide a developing device that is compatible with both contact development and pressure development, and in particular, when pressure development is used, it is possible to maximize the development electrode effect. In addition, by setting Vb so as to satisfy the formula (*) in a steady state, it is possible to form an image with the highest resolution. It is possible to provide a highly reliable developing device by minimizing changes in developing characteristics.

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 schematic cross-sectional view of an embodiment of the developing device of the present invention, FIG. 2 is a schematic cross-sectional diagram of another embodiment of the developing device of the present invention, and FIG. 3 is a schematic cross-sectional diagram of another embodiment of the developing device of the present invention. FIG. 4 is a diagram showing the layer structure of the thin film member of the developing roller in FIG. FIG. 1 ・ 3 ・ 5 ・ 8 ・ 11 ・ 32 ・ Toner. Drive roller: Substrate, latent image carrier, developing bias application means, conductive layer, developing roller, thin layer member, magnetic field generating layer and above

Claims (3)

[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 on a latent image carrier, the developing roller includes a cylindrical thin film member and a cylindrical thin film member. the thin film member has at least a magnetic field generating layer, and the potential of the image area on the latent image carrier is V1, and the potential of the non-image area is V1. A developing device that satisfies formula (*), where V2 is V2, and Vb is a developing bias applied between the latent image carrier and the developing roller. (|V1+V2|/2)≦|Vb|≦|V2|(*) (2) A developing device, wherein the thin film member is in pressure contact with the latent image carrier and satisfies formula (*). (3) The developing device according to claim 1 or 2, wherein the thin film member has a conductive layer, and a developing bias is applied to the conductive layer.