JPH0219447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to development apparatus. More specifically, the present invention relates to a developing device that forms a uniform thin layer of a one-component developer on a developer holding means and develops the layer by facing a latent image holding member.

Various methods are known or proposed for developing devices that use a one-component developer.

Among these, the jumping development method is known as unique. In this method, a one-component developer is uniformly applied as a thin layer onto a developer holding means, and then the electrostatic latent image surface is opposed to the surface of the thin developer layer with a small gap being maintained. This is a method of developing by causing the developer to fly from the developer holding means to the electrostatic latent image surface using the electrostatic attraction. (Tokuko Showa 41-9475
(Refer to US Pat. No. 2,839,400) According to this method, not only is the developer not attracted to the non-image area where there is no latent image potential, but also the developer does not come into contact with the non-image area, resulting in a good image with no fog. Development is performed. Furthermore, since no carrier particles are used, good effects such as no fluctuation in the developer mixing ratio and no deterioration of the carrier particles can be obtained.

In addition, the applicant has also disclosed Japanese Patent Application No. 52-109240 and Japanese Patent Application No. 109240 as a development method different from this jumping development method.
He proposed a completely new developing method as described in No. 53-92108.

In the former development method, a one-component magnetic developer, a developer holding means (non-magnetic), and a magnetic field generating means are arranged in this order, and a uniform thin layer of developer is formed on the developer holding means by the magnetic force of the magnetic field generating means. The thin developer layer surface layer faces the electrostatic latent image forming surface with a small gap therebetween. Then, development is performed by stretching the developer facing the image area due to the electrostatic attraction. Also in this case, since development is carried out in a state where the developer does not come into contact with the non-image area, a developed image completely free of fog can be obtained.

In the latter development method, a one-component magnetic developer, a developer holding means (non-magnetic), and a magnetic field generating means are arranged in this order, and a uniform thin layer of developer is formed on the developer holding means by the magnetic force of the magnetic field generating means. A thin developer layer is formed, and the surface layer of the developer thin layer faces the electrostatic latent image formation surface with a small gap therebetween so as not to contact the surface layer. Developing is carried out by applying an alternating current bias voltage as a developing bias voltage to this and further changing the gap between the electrostatic latent image surface and the developer holding means over time. According to this development method, at the initial stage of development, the developer reaches the non-image areas of the electrostatic latent image, thereby developing the halftone area, and over time, the developer reaches only the image area. As a result, compared to the former developing method, it is possible to achieve the effect of developing with good halftone reproducibility and without fogging.

In this way, the development method in which a thin layer of one-component developer is arranged opposite to the latent image surface has extremely superior effects in terms of development performance, image reproducibility, developer life, etc. compared to conventional methods. It will be done. However, these developing methods also have the following problems when put into practical use.

(1) The development history remains in the developer layer on the developer holding means due to the development action, and a ghost image is developed during the next development.

In the above development method, the developer layer formed on the developer holding means is an extremely thin layer. Therefore, once this developer layer is subjected to development, there is a large difference in the thickness of the developer layer between the portion corresponding to the image area and the portion corresponding to the non-image area. This history of the thickness of the developer layer remains unchanged even if a new developer is supplied after development, and it has a great effect on the next development, and is called a ghost.The negative pattern of the previously developed image remains in the next development. There were some drawbacks that occurred. This may be because the developer removed from the surface of the developer holding means cannot be sufficiently supplied in the subsequent developer replenishment process, or there may be a slight gap between the developer remaining on the surface of the developer holding means and the newly supplied developer. This is thought to be due to differences in characteristics (especially tribo).

(2) During long-term development, a thin layer of developer is formed on the surface of the developer holding means, resulting in a decrease in development performance.

During development, the developer is constantly repeatedly brought into contact with and separated from the surface of the developer holding means, and as a result, the surface of the developer holding means is likely to be stained with developer and a film layer of developer may be formed. This film layer may be a low molecular weight resin component contained in the developer, a control agent for providing triboelectricity, or a layer of very small fine powder that does not contribute to development. In any case, if these components cover the surface of the developer holding means, especially in the case of a developing method that utilizes the electrostatic charge of the developer, the amount of charge on the developer will be insufficient, resulting in a decrease in development density and poor image reproducibility. This may cause problems such as:

(3) During long-term development, the developer may aggregate, or the adhesion between the developer and the surface of the developer holding means may increase, making it difficult to form a layer with a uniform thickness, resulting in uneven development. arise.

It is good if the developer coated on the developer holding means contributes to development within a short time and leaves the surface of the developer holding means, but if the developer does not contribute to development due to reasons such as low density of the original, the developer holding means If the developer is left on the surface for a long time, the cohesive force between the developers increases and the adhesion between the developer and the surface of the developer holding means increases, forming a partially thick coating layer and causing uneven development in the developed image.

In order to eliminate these drawbacks, the structure is such that an endless developer holding means is arranged with a small gap from the latent image holder, and the developer is supplied to this developer holding means, and the supplied developer is In a developing method in which the layer thickness of the developer is regulated and development is carried out by placing the regulated developer layer facing the latent image holding member, the amount of water on the developer holding means is We proposed a method to remove the developer and re-deposit it.

However, although this method solves the above problems, the developer that has gone through the development process once is repeatedly used for development, and when the developer lacks triboelectric charge, development is performed using the old developer that has gone through the development process repeatedly. This caused problems such as unevenness in the developed image due to deterioration of the developer.

The present invention solves all of the above-mentioned problems, and aims to provide a new developing device with good image reproducibility, high fidelity, and long developer life.

That is, the present invention provides a monocomponent developer thin layer that is thinner than the gap between the latent image holder and the developer holding means in an endless developer holding means arranged with a minute gap with respect to the latent image holder. A developing device that forms and develops a latent image includes a developer supply means for storing a monocomponent developer and supplying a new monocomponent developer to form a developer layer, and the developer holding means after development. The one-component developer is removed from the developer, the removed one-component developer and the one-component developer supplied from the developer supply means are stirred and mixed, and the one-component developer thus stirred and mixed is held as a developer. Since the developing device is characterized in that it is equipped with a means for imparting to the means, all of the above-mentioned problems have been solved.

Hereinafter, specific embodiments of the present invention will be described in detail using FIGS. 1 and 2.

FIG. 1 shows an embodiment of the invention. In the figure, reference numeral 1 denotes an electrostatic latent image holder such as a photoreceptor or an insulator on which an electrostatic latent image is formed, which moves in the direction of arrow a. Reference numeral 2 indicates a non-magnetic developing sleeve (eg, made of stainless steel, steel, plastic, rubber, etc.) which is disposed with a minute gap between the electrostatic latent image carrier and rotates in the direction of arrow b. This minute gap is set to be larger than the thickness of the thin developer layer formed on the developing sleeve. As shown in the figure, a magnetized magnetic roll 3 is fixedly provided inside the developing sleeve. A layer of developer T is formed on the surface of the developing sleeve by the magnetic force of the magnetic roll. The thickness of the developer layer is regulated by a doctor plate 4 (eg, made of iron) placed close to the surface of the developing sleeve. The gap between the tip of the doctor blade and the developing sleeve is set to, for example, 200 μm.

In order to more accurately and reliably regulate the thickness of the developer layer, a magnetic pole is arranged inside the developing sleeve facing the tip of the blade. The developer layer, whose thickness has been regulated, then reaches a development position facing the electrostatic latent image holder and is developed by any of the development methods described above. After the development is completed, the developer layer is thinner in the image area corresponding to the electrostatic latent image, maintains its original thickness in the non-image area, and is thicker in the electrostatic latent image area in the halftone area. The thickness changes depending on the image potential.

Here, if new developer is supplied as in the past, it is not possible to form a uniform developer layer thickness even after regulating the developer layer thickness with a doctor blade due to the influence of the previous development history. Even if it is obtained, faithful development will not be performed in the next development, and the previously developed image will appear as a ghost. This is due to a difference in the thickness of the developed layer before applying new developer, or a difference in characteristics between the developer in the developer layer that has been used for development and the newly supplied developer (tribo state, etc.)
It is thought that this is influenced by.

The present invention has been improved to eliminate this drawback, and the embodiment shown in FIG. 1 is as follows. As mentioned above, the layer thickness on the surface of the developing sleeve after development has changed, and the characteristics of the developer have also changed. Therefore, after the development is completed, a developer removing plate 5 is installed at a position before the developer is supplied by the hopper 5 to remove the developer on the developing sleeve, and its mounting angle is set as shown in the figure to scoop up the developer. A good angle is in the counter direction with respect to the moving direction of the developer layer. This removal plate is preferably made of phosphor bronze with a thickness of about 130 μm, for example.

In this way, the developer on the developing sleeve is collected into the developing container 6. On the other hand, new developer is supplied into the developer container 6 from a hopper 7. The old developer removed by the developer removal plate 5 and the new developer supplied from the hopper 7 are stirred by a stirring brush 8. The old and new developers sufficiently stirred by the stirring brush are applied again onto the developing sleeve by the developer applying brush 9, and developed again with the developer layer thickness regulated by the doctor blade. be done.

In this way, the developer that has passed through the development position is removed from the surface of the development sleeve and stirred together with the developer newly supplied from the hopper, resulting in a developer with new vitality and a high concentration that always has a clear sharpness. A developed image can be obtained.

Next, FIG. 2 shows another embodiment in which the developing method of the present invention is implemented as an apparatus. Items with the same number symbols as in Figure 1 have the same functions. The specific structure for removing the developer on the developer sleeve in the embodiment shown in FIG. 2 is as follows. A developer removing brush 10 is provided to remove the developer that has passed through the first development position from the surface of the developing sleeve. This removal brush 10
It also serves to stir the developer newly supplied from the hopper 7, and the old and new developer are mixed well. The mixed and stirred developer is then passed through filter 1.
1, the developer is again applied onto the developing sleeve by the developer supply bushing, its thickness is regulated by a doctor blade, and it is used for development. The filter 11 functions to remove impurities such as agglomerated toner and paper dust, so that a pure developed image can always be obtained.

As a result of this structural action, the development history of the developer layer on the developer holding means is erased, so that no ghost occurs during the next development. Even if the developing action is performed for a long time, a thin layer of developer is not formed on the surface of the developer holding means, so that good developing performance can always be maintained. The developer layer subjected to the development action is removed once and stirred with new developer supplied from the hopper to form a new developer layer, so that no aggregation of the developer occurs. Furthermore, when selecting materials for the developer, it is only necessary to focus on the initial development performance and fixing performance, so that extremely remarkable effects such as a wider range of material selection can be obtained.
Another great effect of the present invention is that the developer on the surface of the developer applying means is always replaced with a well-mixed mixture of old and new developer. This means that no unevenness occurs in the developer layer on the surface of the agent applying means. When the developer that does not contribute to development remains stationary on the application means for a long time, the cohesive force between the developers or the adhesive force between the developer and the application means increases, and the thickness of the developer layer gradually decreases. This tendency has made it difficult to achieve stable image reproducibility. However, this problem could be solved by imparting movement to the developer on the application means as in the present invention.

Note that in the above explanation, the one-component development method refers to the conventional mixed system of carrier particles and toner particles, and the toner particles are mixed with a charge control agent, lubricant, abrasive, etc. This is within the scope of one-component development. Furthermore, although an electrostatic latent image has been described in the embodiment as a latent image holder, it is also applicable to a magnetic latent image. In this case, it is necessary that no magnetic field generating means that would disturb the magnetic latent image be disposed within the magnetic sleeve facing the magnetic latent image. In the example, the magnetic roll is fixed and the developing sleeve is moved, but this also applies to the magnetic roll moving,
It is also applicable to fixing the developing sleeve and various other relative movements. Further, although the non-magnetic developing sleeve has been described as the developer holding means, a belt-shaped one can also be used.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view illustrating the structure of one embodiment of the developing device of the present invention, and FIG. 2 is a cross-sectional view showing another embodiment of the present invention. In the figure, 1 is an electrostatic latent image holder, 2 is a developing sleeve, 3 is a magnetic roll, 4 is a doctor blade, 5 is a removal plate, 6 is a developer container, and 7
8 is a hopper, 8 is a stirring brush, and 9 is an application brush.

Claims (1)

[Scope of Claims] 1. A thin layer of one-component developer that is thinner than the gap between the latent image holder and the developer holding means in an endless developer holding means arranged with a minute gap with respect to the latent image holder. A developing device that forms a latent image and develops a latent image, the developer supply means containing a monocomponent developer and supplying new monocomponent developer to form a developer layer, and retaining the developer after development. The one-component developer is removed from the means, the removed one-component developer and the one-component developer supplied from the developer supply means are stirred and mixed, and the stirred and mixed one-component developer is used as a developer. A developing device comprising: means for applying to the holding means;