JPS6190173A - Developing device for one-component toner - Google Patents

Abstract

PURPOSE:To form an electric field which is approximately uniform in the thickness direction of a toner layer, by setting an angle formed between surfaces facing the toner layer to be electrified of two electrodes, which triboelectrify a toner, to the angle<180 deg.. CONSTITUTION:The first electrode 5 is formed to a wedge shape to make the angle, which is formed between the surface facing the developing roll 2 of the electrode 5 and that of the second electrode 6, smaller than 180 deg.. Consequently, the distance between surfaces 5b and 6b facing the toner layer of electrodes 5 and 6 is shortened to increase the density of lines of the electric force in the formed peripheral electric field, and lines of the electric force are projected in the direction of a developing roll. Thus, lines of the electric force having high density are formed up to the surface of the developing roll 2 to form the electric field which is approximately uniform in the thickness direction of the toner layer, and the toner is prevented from being deficiently triboelectrified or being not electrified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a developing device for one-component toner, and particularly to a developing device for one-component toner configured to uniformly charge toner.

(Prior Art) Electrostatic latent image developing methods using one-component toner include one-powder cloud method, contact development method, jumping development method, magneto-dry method, and toner elongation development. In all of these developing methods, the toner to be charged is supplied from a toner hopper directly to a developing roller and is uniformly charged on the developing roller, or the toner is supplied onto a toner supply member consisting of a roller, etc. The electrostatic latent image formed on the photosensitive drum is developed by supplying the charged toner to a predetermined amount of charge on the supply member to a developing roller. In the developing method using this -component developer, uniformly charging the toner to a predetermined amount of charge is an extremely important issue in image formation. - As a method for charging component toner, for example, Japanese Patent Laid-Open No. 119142/1983 discloses a method of charging using frictional charging generated between a toner supply member and toner particles present on the surface thereof. ing. JP-A-54-74755 discloses a method of charging toner on a toner supply member by applying a corona charge to the toner using a corona charger. Furthermore, Japanese Patent Application Laid-open No. 55-48767 discloses that a plurality of electrodes are arranged facing each other with an insulator interposed therebetween, and are spaced a certain distance apart from each other, facing a toner supply member, and there is a gap between these electrodes. A method of charging toner passing through a gap between an electrode and a toner supply member by injecting charge into the toner passing through a gap between an electrode and a toner supply member using an electric field formed around the electrodes by applying a potential difference is disclosed. Furthermore, JP-A-54-42
Publication No. 141 discloses a method in which a rubber blade is disposed opposite to a toner supply member, and the toner is charged using frictional charging between the toner particles and the blade while being conveyed on the toner supply member. There is. However, these methods have various drawbacks. For example, in a method of charging toner particles using frictional charging, it is difficult to uniformly charge the toner to a predetermined amount of charge, and there is a drawback that uncharged toner or undercharged toner is generated. In addition, in the method of charging using a corona charger, the amount of charge on the toner can be easily controlled, but since it uses a corona charger and a high-pressure top source, it not only increases the size of the device but also increases the cost of the device. be. On the other hand, there is a method in which an electrode is provided facing the toner supply member, a potential difference is applied between the electrodes, and a peripheral electric field formed between the electrodes is used to inject charge into the toner moving on the toner supply member to charge the toner. has the advantage that toner can be easily charged with a simple configuration. However, in the method described in JP-A-55-46768, the surfaces of the electrodes that form the electric field that charges the toner, facing the toner layer to be charged, are parallel to each other, so that the toner is not charged. The lines of electric force that make up the electric field become dense near the surface of the toner layer, and sparse lines of electric force are formed deep within the toner layer.As a result, the toner located deep in the toner layer Being charged<<,
It has the disadvantage that it cannot be charged uniformly. As a result, uncharged toner or undercharged toner is generated, which poses a major problem in image formation. Particularly when toner with a small particle size is used, if insufficiently charged toner is generated, the repulsive force acting between the toner particles is small, causing toner agglomeration.

(Objective of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks, to charge the toner layer to be charged on the toner supply member or the developing roller uniformly in the thickness direction of the toner layer, and to prevent undercharged toner and the like. An object of the present invention is to provide a developing device for one-component toner that can prevent the generation of uncharged toner.

(Summary of the Invention) A developing device for one-component toner according to the present invention includes two rollers that are held facing each other via an insulator and extend in the extending direction of a developing roller.
It has two electrodes and a DC power source that provides a potential difference between these electrodes, and the toner to be charged is charged by passing through the peripheral electric field region formed between these electrodes, and the charged toner is charged. In a single-component toner developing device for developing an electrostatic latent image, at least a portion of the surfaces of the two electrodes facing the toner layer to be charged may form an angle other than 180°. This is a characteristic feature.

(Example) FIG. 1 is a sectional view showing the structure of an example of a developing device for one-component toner according to the present invention, and FIG. 2 is a sectional view showing the detailed structure of the toner supply section of the developing device shown in FIG. be. Hopper 1
The uncharged toner contained therein is supplied onto the developing roller 2 from the lower end of the hopper 1. A toner supply port 8 extending in the longitudinal direction of the developing roller 2 is provided at the lower end of the hopper 1, and a toner charging device is provided on one housing wall constituting the toner supply port 8. 4 is attached at a predetermined distance from the developing roller 2. This toner charging device 4 has first and second electrodes 5 and 6 extending in the longitudinal direction of the developing roller 2 and having a thickness of 1.
is held through an insulating plate 7 made of Tear-On (trade name), polyethylene, polypropylene, etc. and about 100 μm thick, and a bias source 8 is connected between the first and second electrodes 5 and 6. , the first @ electrode 5 is positively biased and the second electrode 6 is grounded. The developing roller 2 is made of aluminum,
An insulating layer 1o made of silicone rubber, neoprene rubber, nitrile rubber, etc. is provided on the outer peripheral surface of a conductive sleeve 9 made of stainless steel, brass, etc., and a bias source 11 giving negative polarity is connected to the conductive sleeve 9. When the developing roller 2 is rotated in the direction of the arrow a, the toner contained in the hopper 1 moves in the direction of the arrow A and reaches the toner supply port a.
The toner is gradually supplied onto the developing roller 2. As the developing roller 2 rotates in the direction of the arrow a, the toner in the hopper 1 moves through the toner supply port 8 in the direction b due to the conveying force of the developing roller 2, and is transferred between the first and second electrodes 5 and 6 and the developing roller. 2
It passes through the gap created by the Since a bias source 8 is connected between the first electrode 5 and the second electrode 6 so that the first electrode 5 becomes the positive electrode, there is a peripheral electric field between the first electrode 5 and the second electrode 6. is formed, and each toner particle is positively charged as the toner passes through this electric field region. The positively charged toner is held on the insulating layer 10 of the developing roller 2 by electrostatic force with the electric field created by the negative bias connected to the sleeve 9, and is held on the insulating layer 10 of the developing roller 2 by the edge portion 5a of the first electrode 5. A toner layer of a predetermined thickness is formed on the insulating layer 10 of the developing roller 2. Then, as the developing roller 2 rotates in the direction of arrow a, the electrostatic latent image is carried out to the developing area facing the photosensitive drum 12 on which the electrostatic latent image is formed, and the negative electrostatic charge formed on the photosensitive drum 12 is transferred. The latent image will be developed. Note that the bias source connected to the conductive sleeve 9 of the developing roller 2 also acts as a developing bias. In the developing device having such a configuration, the toner band 'wLflt is determined by the electric field strength of the electric field region formed between the first electrode 5 and the second electrode 6. That is, the amount of charge of toner that passes through a strong electric field strength region increases, and the amount of charge of toner that passes through a region of weak electric field strength decreases. and,? ! The strength of the electric field formed between the electrodes is determined by the density of the lines of electric force between the electrodes, so if the lines of electric force formed between the first electrode 5 and the second electrode 6 are concentrated near the surface of the toner layer, the developing roller 2 The toner near the surface of the insulating layer 1o is no longer charged. Therefore, in order to uniformly charge the uncharged toner in the hopper 1, the lines of electric force created by the first TIL pole 5 and the second TIL pole 6 are connected to the developing roller 2.
It must be formed so as to protrude in the direction of the toner layer and must be formed uniformly in the thickness direction of the toner layer on the developing roller 2. The shape of the electric lines of force in the electric field region formed between the first electrode 5 and the second i-pole 6 is determined by the shapes of the first and second electrodes.

FIG. 3A is a diagram showing the conventional electrode shape and the form of the lines of electric force formed therein, and FIG. 3BNE is a diagram showing the form of the electrode shape and the lines of electric force formed according to the present invention. In conventional electrodes, the surfaces of the first and second electrodes 5 and 6 that face the developing roller are aligned on the same straight line, so that electric current is concentrated between the edge portions 5a and 6a that are close to each other. As the distance from one electrode increases, the sparseness rapidly increases.

For this reason, the density of the lines of electric force becomes extremely small near the surface of the developing roller 2, which is far away from the electrodes. On the other hand, in the electrode according to the present invention shown in FIG. 8B, the island No. 1 iJ pole 5 has a wedge-shaped shape, and the surface of the first electrode facing the developing roller 2 and the surface of the second electrode facing the developing roller 2 are arranged. Since the angle with the surface is smaller than 180', the SX electrode and 6
As the distance between the surfaces 5b and 6b facing the toner layer becomes smaller, the density of the lines of electric force in the peripheral electric field increases, and the lines of electric force protrude toward the developing roller 1 on the surface of the developing roller 2. High density electric lines of force can be formed up to nearby areas. In this case, the wedge-shaped wedge angle θ halo 0°
A range of 8o0 to 8o0 is preferable.

When θ is 6.0° or more, the developing roller protrudes in two directions.
This is because the amount of the electric field is too small, and if θ is less than 300, the lines of electric force will be too concentrated at the tip of the first electrode. In Fig. 3G, the insulator layer 7 is wedge-shaped, the first and second poles 5 and 6 have rectangular cross sections, and the angle between the first electrode and the second pole is smaller than 180'. An example of this configuration is shown below.

With this configuration, the lines of electric force can be further concentrated between the surfaces 5b and 6b, and the lines of electric force can be formed so as to project in the direction of the developing roller 2. The eighth design is such that the surfaces 5b and 6b of the first and 21i1i poles 5 and 6, which face the developing roller 2, are formed into arc shapes so that the first electrode 5 and the second electrode
@The angle formed by the surface facing the developing roller of pole 6 is 180'
Here is an example of a smaller size. FIG. 3E shows an example in which the first electrode has an inverted wedge shape and the angle between the surfaces of the first electrode 5 and the second electrode 6 facing the developing roller 2 is set to be larger than 180°. With this configuration, the electric lines of force are concentrated only near the electrodes and are extremely sparse in the direction of the developing roller 2. Therefore, in this example, when it is desired to charge only the toner particles existing near the surface of the toner layer, for example, it is effective for toner having a large particle size.

As shown in FIG. 8B, the first electrode 5 is wedge-shaped, the first and second electrodes 5 and 6 have the same thickness, and the insulator plate 7
with a thickness of 100 μm, and
When forming a toner layer of μm, the toner is 5μc/
9 was able to be uniformly charged. In this case, the thickness of the toner layer to be charged is set to about 1 of the thickness of the first and second electrodes 5 and 6.
When set to 0%, good charging was possible. Therefore, by appropriately setting the thickness of the electrodes 5 and 6, the thickness of the toner layer, and the toner transport speed, the present invention can be applied to almost all types of one-component toner.

The thickness of the insulator plate 7 is appropriately set in consideration of the magnitude of the bias #8, the dielectric strength voltage of the insulator plate, the conductivity of the toner, etc.

It should be noted that the present invention is not limited to the embodiments described above, and numerous changes and modifications are possible. For example, in the above-described embodiments, the case where a non-magnetic component toner is used has been described, but the present invention can also be applied to a magnetic component toner. In this case, a developing roller including a magnetic roller and a conductive sleeve rotatably disposed around the outer periphery of the developing roller may be used.

Furthermore, even if two electrodes each face the toner m on a plurality of surfaces, the angle formed by at least some of the surfaces is 1.
Any angle other than 80° is sufficient.

(Effects of the Invention) As explained above, according to the present invention, since the angle between the two electrodes for charging toner is set to be smaller than the angle of 2180° formed by the surfaces facing the toner layer to be charged, there is a gap between the electrodes. The lines of electric force that are formed can be formed so as to extend in the direction of the toner layer, and a nearly uniform electric field can be formed in the thickness direction of the toner layer. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagrammatic sectional view showing the configuration of an example of a one-component toner developing device according to the present invention, FIG. 2 is a diagrammatic sectional view showing the detailed configuration of a toner charging section, and FIG. 8A is a conventional Diagrammatic cross-sectional view showing the electrode shape and form of electric lines of force, Figure 3 B-E
1 is a diagrammatic cross-sectional view showing the shape of an electrode and the form of lines of electric force according to the present invention. l...Hopper 2...Developing roller 8,
... Toner supply port 4 ... Toner charging device 5 ...
・First electrode 6...Second electrode? ... Insulator plate 8, 11 ... Bias source 9 ... Sleeve 10 ... Insulator layer Patent applicant Olympus Optical Industry Co., Ltd. Figure 3A Figure 3CD

Claims (1)

[Claims] 1. It has two electrodes that are held facing each other with an insulator in between and extends in the extending direction of the developing roller, and a DC power supply that provides a potential difference between these electrodes, and the toner to be charged is charged between these electrodes. In a one-component toner developing device in which toner is charged by passing through a peripheral electric field region formed between electrodes and an electrostatic latent image is developed with the charged toner, the toner is opposed to the toner layer to be charged of the two electrodes. A developing device for one-component toner, characterized in that the angle formed by at least a portion of the surface is an angle other than 180°.