JPH0483280A - Developing device - Google Patents

Abstract

PURPOSE:To give single-component toner a mean electrostatic charging quantity which is required for development by providing a layer forming member which forms a thin layer of a single-component developer and a corona charger which gives electrostatic charges to the single-component developer in the thin layer. CONSTITUTION:A developing sleeve roll 1 and an elastic blade 4 are arranged abutting on each other and the toner 7 is supplemented to between them and applied to the developing sleeve roll 1. The corona discharger 3 has a control grid 2, which charges the thin layer of toner uniformly. An agitating blade 6 operates to gather the toner 7 in the direction of a conveyance roller 8. A roller which is made of aluminum and processed to about 3Z - 10Z surface roughness is used as this developing sleeve roll 1. Consequently, even the single- component toner can be charged electrostatically only by a quantity required for development and in a development area, toner which is not charged and charged to the opposite polarity can be eliminated, so the image density is stable, an image density irregularity is small, and a less-fogging image can be obtained for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device used in electrophotographic copying machines, laser printers, and the like.

[Conventional technology]

Conventionally, in developing devices that have the function of charging one-component toner and transporting it to the developing area, the toner is charged using a brush, or the toner is pressed against the developing sleeve by a toner regulating member when forming a thin film. There were methods that used friction with toner to charge the toner. Regardless of the method, when using frictional charging, the probability of contact between toner and foreign substances (brushes, sleeves, regulating members, etc.) is increased, and the material is carefully examined to promote charging. There is. Furthermore, several methods have been proposed for attempting to charge toner using methods other than frictional charging. Among them, a method of charging toner with a corona charger has also been proposed.

[Problem to be solved by the invention]

According to the conventional method, the method of triboelectrically charging toner by bringing it into contact with the toner has generally been a two-component method in which a powder called a carrier for accelerating charging is placed in a developing device and triboelectrically charged. However, since it is necessary to accurately control the mixing ratio of the L1 carrier and toner, and the stirring mechanism, toner replenishment mechanism, etc. are complicated, the developing device becomes large, which is disadvantageous in terms of cost. Further, when the carrier is used for a long period of time, a toner component called spent toner adheres to the surface of the carrier, resulting in a decrease in charging ability. Since this carrier basically remains in the developing device without being consumed, the carrier must be replaced periodically. A one-component development method has been proposed to solve these problems. This is a method in which the developing mechanism does not contain a carrier, but only contains toner, and is provided with some kind of charging means. As a toner charging means in a one-component system, a method that utilizes frictional charging with a substance constituting a developer container is generally used. These methods increase the probability of contact between toner and foreign substances to promote charging. The basic problem with one-component systems is that frictional charging is insufficient compared to two-component systems, and contact between toners can result in toner being charged to the opposite polarity to the polarity that is originally desired. That was the problem. In other words, in one-component systems, the average charge amount of the toner is generally insufficient and the charge amount spectrum is wide, resulting in the generation of toner that does not contribute to development. This generation of toner that does not contribute to development poses the problem that the toner is not used effectively, but at the same time, it also causes the even bigger problem of a general decrease in image density and the occurrence of local image density unevenness. Random. In a one-component system, there is no carrier, so there is no need to replace it. However, the actual life of the developing device is determined by the accumulation of toner that does not contribute to development. This is particularly true in the case of non-disposable developing devices, in which the accumulation of defective toner is a serious problem. For this reason, even disposable type developing devices cannot be loaded with a large amount of toner to avoid this problem.

In addition, a method has been proposed in which a corona charger is used to promote and uniformly charge the toner. However, although this method can charge the toner to a single polarity, the absolute value required for development is 5 to 30 μC/g.
It was difficult to obtain an average charge amount of . In addition, toner is a powder, and most of it is an insulating material, so unless there is a mechanism that uniformly applies corona to each toner particle, charged toner and uncharged toner will be generated. There is a drawback.

[Means to solve the problem]

The present invention includes a layer forming member that forms a thin layer of a one-component developer, and a corona charger that applies an electric charge to the thin layer of the one-component developer.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. 1st
In the figure, the developing sleeve roll 1 and the elastic blade 4 are placed in contact with each other, and during this time, toner 7 is supplied and a thin layer of toner is applied to the developing sleeve roll 1. The corona charger 3 has a control grip 2 to uniformly charge the thinned toner. A stirring blade 6 provided in the developer container 5 serves to stir the toner 7 toward the conveyance roll 8 . This developing sleeve roll 1 has a surface roughness of 3
An aluminum roller that has undergone a treatment of about Z~107 is used. The material of the developing sleeve roller 1 must be at least electrically conductive. It is desirable that the thinned toner layer be formed into a single layer so that two or more layers of toner do not overlap, and by forming the toner layer into a single layer, charges can be uniformly injected into each toner particle. If the toner is not formed into a single layer, the lower the layer, the more difficult it is for corona to reach the toner, making it difficult to charge it uniformly. Further, as the corona charger 3, a scorotron charger having a control grid 2 is preferable in order to keep the surface potential of the developing sleeve roll 1 constant, which is generated when the thinned toner is charged. The average particle size of toner is 5μ
A material having a diameter of about m to 20 μm can be used. When a charge of several tens of μC/g in absolute value of the average charge amount is applied to the toner layer made thin (single layer) with such a configuration, the surface potential on the developing sleeve roll 1 becomes several hundred volts. With a potential of this level, sufficiently stable charging is possible with a scorotron charger. However, if the toner layer is not thin (for example, if toner particles are piled up in 10 or more layers), the surface potential of the developing sleeve roll 1 will be several thousand volts, which is an area that is impossible with a corona charger. Therefore, for this reason as well, it is necessary to make the toner layer thinner.

〔Effect of the invention〕

By employing the above configuration, even one-component toner can be given the amount of charge necessary for development, and uncharged toner or toner charged to the opposite polarity can be eliminated in the development area. As a result, the image density is stable, there is little unevenness in image density, and images with little fog can be obtained for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. 1...Developing sleeve roll, 2...Control grid,
3... Corona charger, 4... Elastic blade, 5...
・Developer container, 6... Stirring blade, 7... Toner 8
...Conveyance roll.

Claims (1)

[Claims] A developing device comprising: a layer forming member for forming a thin layer of a one-component developer; and a corona charger for applying an electric charge to the thin layer of the one-component developer.