JPH0453311B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a developing device for electrophotography or electrostatic recording, and more specifically to a developing device using a powder cloud developing method to improve image quality. be.

(Prior Art) Conventionally, there are the following developing apparatuses that use a powder cloud developing method or a similar developing method. First, JP-A-53-
The developing device described in Publication No. 110835 mixes and stirs magnetic particles with a size of 10 μ or more and toner particles finer in an alternating magnetic field, extracts a gas containing only toner particles from the stirred gas, and processes the extracted gas. Development is performed by supplying it to the latent image surface.

Next, the developing devices described in Japanese Patent Application Laid-open Nos. 55-41412, 41413, and 41414 carry out development by supplying a toner cloud flow to the latent image through a circulating transport path, collect residual toner through a filter, and air After separating the toner from the flow, the toner is returned to the circulation path.

(Problems to be solved by the invention) In such a developing device, as shown in FIGS.
As shown in the figure, there are problems such as toner particles adhering to non-image areas or image smearing. First, as shown in FIG. 2A, a latent image is formed on the electrostatic latent image bearing surface 1, where area a indicates the image area, and areas b and c each indicate the non-image area. shall be. When a toner cloud flow containing charged toner particles passes near the surface of the supporting surface 1 from the direction indicated by the arrow D in parallel with the supporting surface 1, the toner particles 2 are carried as shown in FIG. 2B. Adheres to surface 1. That is, charged toner particles are difficult to adhere to the inclined portions of the electric lines of force 3 (both ends of region b) and non-image portions a and c, and are concentrated at the center of image portion b. However, when the toner cloud flow is flowing at a constant speed, in image area b, the image omission is further emphasized on the upstream side of the toner cloud flow, and toner particles also adhere to the slope of the line of force 3 on the downstream side. ,
Alternatively, it may stick to the edge of the image area b.

Also, as shown in Figure 3A, arrow E (at 45° to the supporting surface) or arrow F (perpendicular to the supporting surface)
When the toner cloud flow is applied from the direction of , as shown in FIG. 3B, toner particles adhere to almost the entire area of image area b, but also adhere to non-image areas a and c, resulting in significant fogging. will occur.

Further, in the conventional developing device, density unevenness occurs when developing a solid black image, making it difficult to form a uniform image.

An object of the present invention is to provide a developing device that solves the problems of the prior art.

(Means for Solving the Problems) The present invention provides a developing device for developing an electrostatic latent image using toner particles contained in a mist state in an air flow, in which a portion near an electrostatic latent image bearing surface is provided. a first air flow forming means for forming a first air flow containing charged toner particles substantially parallel to the latent image bearing surface, and a second air flow containing no toner particles extending substantially perpendicular to the latent image bearing surface. and a second air flow forming means for forming an air flow.

(Operation) The operation of the present invention configured as described above will be explained with reference to FIG. 4. In the figure, in a state in which a toner cloud flow (first air flow) containing charged toner particles is passing near the surface of the carrier 1 from the direction indicated by arrow A in parallel to the carrier 1, When a second air stream containing no toner particles is applied in the direction of arrow B, turbulence is generated in the vicinity of the carrier surface 1. The first air flow as a whole advances in the direction of arrow A while maintaining this turbulent state. As a result, toner particles corresponding to the latent image are attached to the supporting surface 1, and toner particles do not attach to the non-image area.
The toner image does not flow (protrude from the edge of the image area) due to the flow of electric current.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic diagram of an embodiment of the present invention.
A photoreceptor 11 forms a surface for carrying an electrostatic latent image, and is composed of a conductive substrate 12 and a photoconductive layer 13.
14 is a developing device, which includes an inlet 15 for a toner cloud flow (first air flow) containing pre-charged toner particles, an inlet 16 for a second air flow not containing toner particles, and a developing device. An outlet 17 for an air stream containing toner particles to be discharged from inside 14 is formed in the housing 18 of the developer. Further, a filter member 19 having fine ventilation holes through which the second air flow not containing toner particles introduced from the inlet 16 is disposed inside the developing device 14 . Here, a broken line A drawn inside the developing device indicates the direction of the toner cloud flow introduced from the introduction port 15, and a dashed line B indicates the direction of the air flow not containing toner particles introduced from the introduction port 16. This shows that.

As shown in the figure, in this example, the air flow B acts in a direction substantially perpendicular to the toner cloud flow A, and the toner cloud flow A is directed toward the discharge port 17 as a whole near the surface of the photoreceptor 11. However, a turbulent flow containing toner particles is generated on the surface of the photoreceptor as shown by the broken line in the figure. A latent image on the photoreceptor 11 is developed by the toner particles contained in this turbulent flow.

Next, FIG. 5 shows another embodiment of the present invention. In this example, an electrode 5 is placed near the surface of the photoreceptor 11.
1, and this electrode is grounded or a bias voltage is applied to this electrode. The direction of the electric force lines due to the latent image charge is shown by the broken line. As the electrode, in addition to circular hole mesh electrodes, mesh electrodes with square or circular holes can be used, and wire electrodes (diameter 50~
200μ) can also be used. Further, the applied voltage may be either direct current or alternating current. The other configurations are the same as the example shown in FIG.

Also in this embodiment configured in this way, the first
Similar to the illustrated example, a suitable toner image is formed.

In the above embodiment, the flow speeds of the toner cloud flow A and the air flow B are determined by the charge amount of the toner particles,
It should be set appropriately based on the latent image potential, etc. Further, each flow can be generated using known means such as a blower, and by appropriately selecting these means and the diameter of the ventilation hole of the filter member 19, the speed of each flow in the developing device can be adjusted. and turbulence can be controlled.

In addition, in the embodiments described above, the filter member 19 having minute ventilation holes is, for example,
Polymer beads (diameter 60 to 200μφ) are compressed and formed into branch shapes to have a rhombohedral filling structure, and ventilation holes (5
~40μφ) can be used.

Furthermore, although the above-mentioned embodiments do not mention the method of charging toner particles, (1) triboelectric charging with the inner tube wall peculiar to aerosol development, (2) corona charging, and (3) two-component development. A known method such as electrode charging may be used to separate only the toner by stirring and mixing the toner as an agent and applying frictional electrification.

Furthermore, in the above-described embodiments, a plate-shaped photoreceptor is used as an example, but it goes without saying that it may be in the shape of a cylindrical drum or an endless belt, for example.

(Effects of the Invention) As described above, according to the present invention, an air flow that does not contain toner particles is applied to a toner cloud flow that flows in the vicinity of a latent image carrying surface in parallel to the carrying surface. Therefore, a turbulent flow containing toner particles is formed on the latent image bearing surface, and a suitable toner image corresponding to the latent image can be formed.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Figures A and B, Figures 3A and B, and Figures 4A and B are explanatory diagrams showing the operation of adhering toner particles to a latent image;
The figure is a configuration diagram showing another embodiment of the present invention. 11... Photoreceptor, 12... Conductive substrate, 13...
...Photoconductive layer, 14...Developer, 15...Inlet,
16...Inlet, 17...Outlet.

Claims (1)

[Claims] 1. In an apparatus for developing electrostatic latent images using toner particles contained in a mist in an air stream,
a first air flow forming means for forming a first air flow containing charged toner particles in a vicinity of the electrostatic latent image bearing surface and substantially parallel to the electrostatic latent image bearing surface; and substantially perpendicular to the latent image bearing surface. and second air flow forming means for forming a second air flow containing no toner particles.