JPH04333877A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device by which toner is uniformly electrostatically charged and clear development is accomplished in a non-contact developing system using non-magnetic toner. CONSTITUTION:In the developing device 10, the non-magnetic toner 12 and carrier beads 18 are mixed and stirred by a stirring blade 20. Thereafter, the toner 12 is carried to a metallic mesh 28 by a sponge roller 22. The metallic mesh 28 is provided to be opposed to a photosensitive body 26, and an electrostatic latent image is developed to be a visible image with the toner 12 there.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in electrophotographic devices and the like, which develops an electrostatic latent image on a photoreceptor into a visible image.

0002

[Prior Art] Conventionally, as a developing device for developing an electrostatic latent image on an image carrier into a visible image, a developing device using a developing method called two-component magnetic brush developing method has been considered and has not been put into practical use. ing.

[0003] In this method, large magnetic particles called carriers and toner are mixed and stirred and charged by friction, and then the toner and carrier, which adhere to each other by electrostatic force, are non-magnetic and have a cylindrical shape. A magnetic brush is formed on the developing sleeve by the magnetic force of the magnet provided inside the sleeve.
This magnetic brush is conveyed to the developing area by the rotation of the sleeve, where it rubs against the electrostatic latent image on the photoreceptor, causing toner to adhere to the latent image and developing it into a visible image. According to this method, the toner is charged uniformly and the carrier functions as a developing electrode, so that beautiful images with excellent reproducibility of fine lines can be obtained.

However, the above development method has the following drawbacks. That is, in order to uniformly triboelectrically charge the toner, a stirring means is required to mix and stir the toner with the carrier. Regarding the mixing ratio of toner and carrier, if there is too much toner, the toner will not be charged sufficiently, resulting in uncharged toner, which will tend to adhere to the non-image area of the photoreceptor and cause the image to be imaged. It contaminates the On the other hand, if the amount of toner is too small, not only the image density decreases but also carrier adhesion occurs in which the carrier shakes off the magnetic binding force and adheres to the photoreceptor. Therefore, the mixing ratio of toner and carrier must be strictly controlled, which requires means for detecting the mixing ratio and means for replenishing toner. For these reasons, the two-component magnetic brush developing type developing device inevitably becomes larger and more complicated.

[0005] In order to solve the above-mentioned drawbacks, a developing device using a one-component magnetic toner developing method without using a carrier was devised. This is a method in which an elastic blade presses the magnetic toner on the developing sleeve to charge the toner and regulate the layer thickness, thereby reversing and developing the electrostatic latent image on the photoreceptor into a visible image.

However, in this method, in order to sufficiently charge the toner with the elastic blade, the toner layer on the developing sleeve must be made very thin, and therefore, the toner layer at the pressure contact portion between the elastic blade and the developing sleeve is As a result, toner sticks due to stress, resulting in toner clogging between the blade and sleeve. This appears as white streaks on the sleeve and detracts from the beauty of the image. Furthermore, if the pressing force of the blade is weakened in order to prevent this toner from sticking, the toner layer on the sleeve will become thicker and sufficient charging will not be achieved. As a result, toner adheres to non-image areas on the photoreceptor, staining the image.

[0007] Recently, a developing device has been devised that uses a developer containing magnetic toner and a small amount of magnetic carrier, and carries out development by conveying the developer using a relatively rotating sleeve and a magnetic roll. has been made into With this developing method, a developing device with relatively excellent fine line reproducibility and solid black density can be manufactured with such a simple configuration.

[0008] Such a developing method using magnetic toner has the advantages of a simple structure and easy handling of the toner, but since the toner contains magnetic powder, the images obtained are only black and white. , it is unsuitable as a developing device for obtaining color images. Therefore, in the one-component development method, a development method using non-magnetic toner has been considered and put into practical use in order to cope with colorization.

The developing device shown in FIG. 4 is an example of this,
This is an example of an impression development method. The configuration and operation will be described below.

The developing device 70 includes a toner container 72, a toner 74 in the toner container, a discharge roller 76 for discharging the toner 74 from the toner container, a developing roller 78 made of a conductive material, and a developing roller. A power supply 79 provided at 78 and an elastic blade 8 pressed against the developing roller 78
0 and a charging roller 8 provided in contact with the developing roller 78
2. Further, the developing roller 78 has elasticity and is pressed against the photoreceptor 84 carrying the electrostatic latent image.

The toner in the toner container is removed by a discharge roller 76.
The image is conveyed onto the developing roller 78 and the charging roller 82 by the rotation of the image forming apparatus. This toner is frictionally charged between the developing roller 78 and the charging roller 82. The charged toner adheres to the developing roller 78 by van der Waals force and mirror image force, and is carried to the vicinity of the photoreceptor 84 by the rotation of the developing roller. An elastic blade 80 is pressed against the upstream side near the photoreceptor 84, and the layer thickness of the toner on the developing roller is regulated by the elastic blade 80, and the toner is further triboelectrically charged to be uniformly charged. The thus charged toner adheres to the photoreceptor 84 by the electric field generated by the electrostatic latent image on the photoreceptor, and the electrostatic latent image is developed into a visible image.

[0012] Such a one-component non-magnetic toner developing method is as follows:
In the following points, this method is advantageous compared to a two-component development method that similarly uses non-magnetic toner. That is, since no carrier is used, there is no need to strictly adjust the mixing ratio of toner and carrier as in the two-component development method, and therefore no toner concentration detection means is required. Further, since a magnet, which is required in the two-component developing method, is not required as a means for carrying the toner on the surface and transporting it to the vicinity of the photoreceptor, the weight of the developing device itself is reduced.

[0013]

However, the conventional developing device having the above structure has the following problems.

[0014] In the one-component development system, since triboelectric charging properties are disadvantageous, the toner layer on the developing roller is extremely thin, and at most is several times the toner particle diameter (approximately 10 microns). Therefore, in order to increase the image density, development is performed by bringing a developing roller into contact with the photoreceptor, but as a result, the surface of the photoreceptor becomes easily damaged, shortening its life. Furthermore, since it is difficult to perform triboelectric charging uniformly, the image quality is clearly inferior to that of the two-component method.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing device that uses a non-contact developing method using non-magnetic toner and can uniformly triboelectrically charge the toner and perform beautiful development.

[0016]

[Means for Solving the Problems] In order to solve the above problems, the developing device of the present invention converts the electrostatic latent image on the image carrier into
In a developing device that develops into a visible image, non-magnetic toner and
A stirring means for stirring and mixing the magnetic or non-magnetic fine particles, the non-magnetic toner and the fine particles, a conveying means for conveying the non-magnetic toner, and a stirring means provided at a position opposite to the image carrier and in contact with the conveying means. It also includes a conductive member having a large number of small holes.

[0017]

[Operation] The developing device of the present invention having the above-mentioned structure uses the stirring means to stir and mix the non-magnetic toner and the magnetic or non-magnetic fine particles. Thereafter, the non-magnetic toner is transported to a conductive member having a large number of small holes by the transport means. The conductive member faces the image carrier, where the non-magnetic toner develops the electrostatic latent image into a visible image.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the developing device of the present invention.

The developing device 10 includes a non-magnetic toner 12, a toner container 14 containing the non-magnetic toner 12, and a discharge roller 16 provided at the opening of the toner container 14 and feeding the non-magnetic toner 12 into the developing device. , non-magnetic carrier beads 18 housed in the developing device 10 , stirring blades 20 as stirring means for stirring and mixing the non-magnetic toner 12 and the carrier beads 18 , and supporting and conveying the non-magnetic toner 12 . A sponge roller 22 as a conveying means, a regulating blade 24 for regulating the amount of non-magnetic toner 12 adhering to the sponge roller 22, and a regulating blade 24 that faces the photoreceptor 26 carrying an electrostatic latent image and contacts the sponge roller 22 described above. A metal mesh 28 serving as a conductive member is provided.

The non-magnetic toner 12 is made by using, for example, a polyester resin as a binder polymer, and in the case of a black toner, colored fine powder such as carbon black and a charge control agent such as a metal complex of a monoazo dye are kneaded. It is then ground to an average particle size of about 10 microns. As the charge control agent, an electron-accepting substance such as an azo metal-containing dye, chlorinated paraffin, or chlorinated polyester is used for the negatively charged toner used in this example. Also,
The non-magnetic carrier beads 18 are approximately spherical beads made of glass or the like with an average particle size of about 50 to 100 microns, and are coated with a resin (for example, styrene-acrylic resin) that is relatively distant from the toner in terms of charging, as necessary. Get it by coating.

The metal mesh 28 is equipped with a power source 30 and is applied with a developing bias. This developing bias waveform may be a DC voltage or a DC voltage superimposed with an AC voltage. Further, the mesh roughness of the metal mesh 28 is desirably larger than the above-mentioned toner particle size and smaller than the carrier bead particle size. That is, it is preferably 20 to 50 microns.

Next, the operation of this developing device will be explained. The non-magnetic toner 12 in the toner container 14 is thrown into the developing device 10 by the rotation of the discharge roller 16. Therefore, the non-magnetic toner 12 is stirred and mixed together with the carrier beads 18 by the stirring blade 20, and the carrier beads 18 are stirred and mixed.
It receives frictional electrification due to this, and in this case it becomes negatively charged. The non-magnetic toner 12 thus negatively charged is transferred to the sponge roller 2.
2 by mechanical and electrostatic forces. The sponge roller 22 conveys the attached non-magnetic toner 12 by rotating, and after the amount of toner is regulated by a regulating blade 24, the non-magnetic toner is conveyed to a metal mesh 28 facing the photoreceptor 26. .

The sponge roller 22 is provided in contact with the metal mesh 28 with appropriate pressure. Therefore, the non-magnetic toner 12 conveyed by the sponge roller 22 is exposed on the surface facing the photoreceptor 26 on the outside of the metal mesh 28 . The non-magnetic toner 12 thus attached to the outside of the metal mesh 28 is blown away by the electrostatic latent image carried on the photoreceptor 26 and the electric field caused by the developing bias applied to the metal mesh 28, making the electrostatic latent image visible. Develop into an image.

[0024] In the developing device having such a configuration, mixing and stirring with carrier beads is used as a method of charging the toner. Therefore, compared to the frictional charging method using a pressure welding blade as shown in the conventional example,
The contact area of the charging member that rubs the toner with the toner is large, which is advantageous in uniformly triboelectrically charging the toner.

FIG. 2 shows a second embodiment of the invention. The developing device 30 includes a toner container 32 and a sponge roller 34.
, a regulation blade 36 provided so as to be in contact with the sponge roller 34 , and a sponge roller 3 facing the photoreceptor 38 .
4, and a metal mesh 40 provided so as to be in contact with the metal mesh 40. The metal mesh 40 is equipped with a power source 41 for applying a developing bias voltage. The toner container 32 contains non-magnetic toner 42 and non-magnetic carrier beads 4 therein.
4 are included together. Further, the toner container 32 is equipped with an agitator 48 that stirs and mixes the non-magnetic toner 42 and the carrier beads 44 and conveys the non-magnetic toner 42 to the opening 46. The opening 46 is equipped with a mesh screen 50. There is.

The coarseness of the mesh screen 50 provided in the toner container 32 is selected to be larger than the particle size of the non-magnetic toner 42 and smaller than the particle size of the carrier beads 44.

The operation of the developing device 30 will be explained below. In the toner container 32, the non-magnetic toner 42 and carrier beads 44 are stirred and mixed by rotation of an agitator 48, and the non-magnetic toner 42 is triboelectrically charged. This triboelectrically charged non-magnetic toner 42 is carried near the mesh screen 50 by the agitator 48, but as described above, the coarseness of the mesh screen 50 is such that the non-magnetic toner 42
Since the mesh screen 50 is large enough to allow the carrier beads 44 to pass through, only the non-magnetic toner 42 is sent to the developing device 30 through the mesh screen 50. The non-magnetic toner 42 thus sent adheres to the sponge roller 34 by electrostatic force and mechanical adhesion force, and after the amount of adhered toner is regulated by the regulating blade 36, it is conveyed onto the metal mesh 40, where it is exposed to light. The electrostatic latent image on body 38 is developed into a visible image.

FIG. 3 shows a third embodiment of the present invention. The developing device 52 includes a toner container 54 and a sponge roller 56.
, a regulating blade 57 for regulating the amount of toner on the sponge roller, and a metal mesh 58. The metal mesh 58 is equipped with a power source 59 for applying a developing bias voltage. The toner container 54 is provided with a pair of mesh screens 60 at its opening, and non-magnetic toner 62 is contained within the toner container, and between the pair of mesh screens 60,
Non-magnetic carrier beads 64 are housed. Also,
The mesh screen pair 60 can be vibrated by a piezoelectric element (not shown).

The coarseness of the mesh screen pair 60 is:
The size is such that the non-magnetic toner 62 passes through, but the carrier beads 64 do not pass through.

The non-magnetic toner 62 in the toner container 54 is
The carrier beads 64 pass through a pair of mesh screens 60 containing carrier beads 64 and fall onto the sponge roller 56 . When the non-magnetic toner 62 passes through the mesh screen pair 60, the non-magnetic toner 62 and carrier beads 64 are mixed and agitated by vibrating the mesh screen pair 60 with a piezoelectric element, and are subjected to frictional electrification. In this way, only the triboelectrically charged nonmagnetic toner adheres to the sponge roller 56, and this toner develops the electrostatic latent image on the photoreceptor 66 into a visible image.

Other changes may be made to the present invention without departing from the spirit thereof. For example, in the developing device shown in the above example, metal mesh is used in all parts facing the photoreceptor carrying the electrostatic latent image.
In addition to metal mesh, conductive resin or the like may be used as long as the member is conductive and has many small holes.

[0032]

[Effects of the Invention] As is clear from the above explanation, the developing device of the present invention uses a non-contact developing method using non-magnetic toner, and can uniformly triboelectrically charge the toner and perform beautiful development. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a developing device of the present invention.

FIG. 2 is a diagram showing a second embodiment of the developing device of the present invention.

FIG. 3 is a diagram showing a third embodiment of the developing device of the present invention.

FIG. 4 is a diagram showing an example of a conventional developing device.

[Explanation of symbols]

10 Developing device 12 Non-magnetic toner 18 Carrier beads 20 Stirring blade 28 Metal mesh

Claims (1)

[Claims] Claim 1: In a developing device that develops an electrostatic latent image on an image carrier into a visible image, a non-magnetic toner, magnetic or non-magnetic fine particles, and the non-magnetic toner and the fine particles are stirred and mixed. The present invention is characterized by comprising: a stirring means, a conveyance means for conveying the non-magnetic toner, and a conductive member having a large number of small holes provided at a position facing the image carrier and in contact with the conveyance means. Developing device.