JPS58149076A - Dry type developing device - Google Patents

Abstract

PURPOSE:To obtain a visible image which have less uneven density, high sharpness and resolution and less photographic fog, by providing a means for generating an electric field which generates electric field between a regulating member for layer thickness and a carrying body for a toner by applying the voltage of the polarity reversed from the charging polarity of the toner on the member for regulating the layer thickness. CONSTITUTION:The toner on a sleeve 5 which passed through a clearance (d) and receive substantially no effect of a electric field form a thin layer 3a smaller than the spacing (d) between a regulating member and a sleeve, and since the thickness of the layer 3a is decreased by the effect of the electric field generated in the clearance (d), the thickness thereof is made uniform overall as compared to the case in which conventional regulating members which regulate the layer thickness by the mechanical scraping force alone are used. Since a regulating member 6 for layer thickness is applied with an insulation treatment, the member 6 applied with the voltage prevents the impression of the electric charge of the polarity reverse from the polarity of the charge to be applied on the toners into the toners. It is possible to regulate the thickness of the toner layer 3a on the sleeve 5 by regulating the voltage of an electric power source 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing device that is used to visualize a km image formed on a latent image carrier.

Dry developing devices of the above type used in electronic copying machines, electrostatic recording devices, magnetic printers, and other various recording devices are well known in the art. This type of developing device that uses a one-component developer that does not contain a carrier, unlike a developing device that uses a two-component developer that contains a carrier and a toner, is particularly susceptible to deterioration of the carrier and the mixing ratio of the carrier and toner. Since there is no need to take this into consideration, the advantage is that the configuration of the device can be simplified. In this case, one component. As a toner for a system developer, for example, ]OI, which has a relatively high specific volume resistivity.
As is well known, when using toner with a resistance of 0Ω or more, especially 10l1 to 10l3Ω or more, it is necessary to forcibly charge the toner to a predetermined polarity before using it for development. In order to obtain a visible image, it is necessary to make the toner a thin layer and to charge the toner layer as uniformly as possible throughout its thickness.

A conventionally known structure is to regulate the layer thickness of toner on a toner carrier to reduce the thickness of the toner layer by using a layer thickness regulating member. For example, a configuration is known in which a blade-shaped layer thickness regulating member is placed opposite to the toner carrier, and this scrapes off a portion of the toner conveyed on the toner carrier to regulate the toner layer thickness. However, depending on this configuration, there is a limit to how thin the toner layer can be, and it is difficult to achieve uniform charging of the toner. There is also a known configuration in which a blade-shaped layer thickness regulating member is made of a magnetic material, and this regulating member is disposed inside the toner carrier, and the apexes are opposed to the magnetic poles of the magnet to regulate the toner layer thickness. However, according to this, there is no force unless the magnets are fixedly arranged, and for this reason, this configuration cannot be applied to a developing device that generates a rotating magnetic field to convey toner. The thickness regulating member is inevitably subject to failures in which the layer thickness regulating effect is insufficient or the range of its application is significantly limited.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry developing device that can eliminate or alleviate the above-mentioned conventional drawbacks.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention applied to a developing device for an electronic copying machine will be described in detail with reference to the drawings.

FIG. 1 shows a σ, π latent image carrier constructed as a drum-shaped photoreceptor 1, and a dry type developing device 2 for visualizing an electrostatic latent image formed on the surface of the photoreceptor 1. It goes without saying that a pellet-like or sheet-like photoreceptor may be used instead of the drum-like photoreceptor.

The developing device 2 includes a tank 4 for storing magnetic toner 3, a toner support member configured as a sleeve 5, a female layer thickness regulating member 6 for regulating the layer thickness of the toner, and a layer provided inside the sleeve 5. It has a magnet 7 having a plurality of magnetic poles. The specific volume resistivity of the toner 30 is 1010 Ω. The photoreceptor 1 and the sleeve 5 extend parallel to each other in a direction perpendicular to the plane of the drawing, and the magnetic poles N and S of the magnet 7 have opposite polarities alternately along the circumferential direction of the sleeve 5. The layer thickness regulating member 6 is formed into a blade shape and is fixed to the wall surface of the tank 4, and its tip 6a extends in the longitudinal direction of the sleeve 5 with a substantially constant gap d from the sleeve 5. . Although the magnet 7 is rotated clockwise and the sleeve 5 is rotated counterclockwise, it is possible to configure only one of the magnet 7 and the sleeve 5 to rotate. As is well known. As is also known, the sleeve 5 consists entirely or mostly of non-magnetic material.

When the copying operation starts, the photoreceptor 1 is rotated in the desired direction (clockwise in this example), and an electrostatic latent image is formed on the surface of the photoreceptor by a latent image forming means (not shown). is formed. As the photoreceptor 10 rotates, this latent image moves to an area adjacent to the sleeve 5 and the photoreceptor 1, that is, to a developing area.

When the sleeve 5 rotates counterclockwise and the magnet 7 rotates clockwise, the toner 3 in the tank 4 is supported on the circumferential surface of the sleeve 5 and receives a counterclockwise conveying force. It is sent out of the tank from the outlet 4a of No. 4. The layer thickness of the toner thus sent out is regulated by the layer thickness regulating member 6, as will be described in detail later, and reaches the development area described above.

In this case, the toner conveyed on the sleeve 5 has a polarity of W (in this example, the electric charge forming the latent image on the photoreceptor 1) due to friction with the circumferential surface of the sleeve 5 before reaching the development area. (reverse polarity). When reaching this second development area, the toner electrostatically adheres to the electrostatic latent image, and the latent image becomes a visible image. The toner that did not adhere to the photoreceptor is returned to the tank 4 again.

As mentioned above, the toner used for development is charged to a predetermined polarity by friction with the sleeve 5, but in order to improve the quality of the visible image, the toner should be uniformly charged throughout its thickness. need to be charged.

In order to obtain such uniform charging, the thickness of the toner on the sleeve 5 should be made as thin as possible, or the thickness 1) should be made uniform throughout to create a thick toner layer portion and a thin toner layer portion. It is desirable to prevent this. For this purpose, as described above, the toner is thinned by the layer thickness regulating member 6, and the details of this action will be explained below.

The layer thickness regulating member 6 is made of a conductive material. As shown in FIG. An electric field is generated in the gap d between the two. The portion of the layer thickness regulating member 6 that comes into contact with the toner is insulated, for example, by coating with an insulating resin and making holes, or by pasting an insulating member.

On the other hand, the toner existing in the gap d between the regulating member and the sleeve is charged by contact with the circumferential surface of the sleeve 5 to an extent that the toner is not uniformly charged as a whole, but is already charged to a certain degree. The charged toner tends to adhere to the circumferential surface of the sleeve 5 not only by the magnetic force of the magnet 7 but also by the attractive force with the mirror image charge generated on the sleeve 5. However, as described above, an electric field is generated in the gap d, and in the vicinity of the regulating portion f6, the electric field concentrates on the regulating member 6, and the toner is charged and passes through the regulating member 6.
It also receives electrical attraction from. That is, among the toner existing in the gap d, the toner located near the regulating member 6 tends to adhere to the regulating member 6, and the toner located near the sleeve 5 tends to adhere to the surface of the sleeve 5. The toner existing in the gap d is partially washed away, and only the toner attached to the sleeve 5 passes through the gap d. For this reason, the gap d
The toner on the sleeve 5 that passes through and is not substantially affected by the electric field forms a thin layer 3a that is smaller than the gap d between the regulating member and the sleeve. Moreover, this toner layer 3a is formed in the gap d and is thinned by the action of the π electric field, so compared to the π field OK using a conventional regulating member that regulates the layer thickness with a mechanical scraping blade. Then, the insulation treatment is applied to the layer thickness regulating member 6, which is uniform throughout, as described above. Therefore, the voltage is applied with a charge of opposite polarity to the charge that should be applied to the toner. '1
The member 6 prevents the toner from being injected. Further, by adjusting the voltage of the power source 8, the amount of toner adhering to the regulating member 6, in other words, the thickness of the toner layer 3a on the sleeve 5 can be adjusted. The reason why the toner is thin and dry is that by rubbing the toner with the sleeve 5, the toner can be charged uniformly over its entire thickness, and the thickness is uniform throughout. It is possible to obtain a clear, high-resolution, and visible image with less cuff IJ.

Although the basic configuration example and its operation of the present invention have been described above, the present invention can be configured by variously modifying the above configuration, or can be applied to various other types of developing devices.

For example, in the specific example shown, the magnet 7 is rotated to generate a rotating magnetic field, but as already briefly explained, a developing device in which the magnet 7 is stopped and a rotating magnetic field is not generated can also be applied. Applicable. Hey, if you generate a rotating magnetic field, you can increase the amount of charge on the toner and reduce visible image fog and background stains, so in that sense, it is desirable to generate a rotating magnetic field. In this case, the conventional configuration in which the layer thickness regulating member is made of a magnetic material and the regulating member is opposed to a fixed magnetic pole to regulate the toner layer thickness is not suitable for a developing device that generates a rotating magnetic field. It should be noted that this is not applicable. Note that the layer thickness regulating member 6 according to the present invention may be made of a magnetic material or a non-magnetic material. Furthermore, it is of course possible to use an electromagnet instead of using a permanent magnet as shown in the figure as a means for generating the @ field.Furthermore, the present invention provides development using a high-resistance non-magnetic toner instead of a high-resistance magnetic toner. Applicable to equipment as well.
In this case, there is no need to provide a magnetic field generating means as is known in the art.

In the embodiment shown, the holes are configured to charge the toner by friction with the sleeve, as is known per se.
For example, the invention can also be applied to a configuration in which an electric charge is applied to the toner by a corona discharger or a triboelectric charging member that comes into contact with the toner. In addition, there are developing devices in which the toner carrier is formed by a belt rather than a sleeve, a magnetic printer that forms a latent image magnetically, a direct copy recording device that uses the latent image carrier as the final copy, or a developing device in an electrostatic recording device. The present invention can be advantageously applied to the device Kt.

The present applicant has recently proposed a particularly advantageous configuration of a toner carrier, and the present invention can be applied without any problem to a developing device having such a toner carrier. (Japanese Patent Application No. 55-185726) has not yet been published, so in consideration of this point, this carrier will be explained in some detail below.

As shown in FIG. 2, the toner carrier formed, for example, as a belt or sleeve 5 includes a conductive support 9, a dielectric layer provided on the surface of the conductive support 9, a dielectric layer 0 provided on the surface of the conductive support 9, and a large number of microscopic holes supported by the conductive support 9. This is composed of electrodes 11 and these microelectrodes】1
The electrodes are insulated from the conductive support 9, and the microelectrodes are also substantially insulated from each other. This sleeve 5
For example, when used in a developing device for an electronic copying machine, it is possible to visualize a line image (linear latent image) of an electrostatic latent image with a particularly high density, thereby making it possible to visualize a relatively low-density image in the document to be copied. l
A high-density visible image can be obtained from the fB-line image. And in order to obtain this effect, sleeve 5
It is necessary to make the gap between the photoreceptor and the photoreceptor extremely narrow 1 and to increase the amount of charge on the toner, but by using the layer thickness regulating member 6 (FIG. 1) according to the present invention, these requirements can be satisfied almost at the same time. Therefore, the present invention can be advantageously applied to a developing device having this sleeve (it goes without saying that the toner carrier shown in FIG. 2 can also be used for recording devices other than electronic copying machines). ).

As described above, according to the invention, the intended purpose can be achieved with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an example of a developing device according to the invention, and FIG. 2 is a schematic enlarged sectional view of a sleeve having microelectrodes. 2...Developing device 3...Toner 6...Layer thickness regulating member

Claims (1)

[Scope of Claims] (J) A toner carrier carrying toner and a layer thickness regulating member regulating the layer thickness of the toner on the carrier, the toner being charged to a predetermined polarity; In a dry developing device that visualizes a latent image using charged toner, a voltage having a polarity opposite to the charged polarity of the toner is applied to the layer thickness regulating member to generate an electric field between the layer thickness regulating member and the toner carrier. The developing device is characterized in that it is provided with an electric field generating means for generating an electric field. (2) The developing device according to claim 1, wherein at least a portion of the layer thickness regulating member that contacts the toner is subjected to insulation treatment.