JPH0256586A - Liquid developing device - Google Patents

Abstract

PURPOSE:To enable uniform solid black development by composing the liquid developing device of a mechanism which gives real charges to liquid toner on the surface of a carrier for conveying the liquid toner to a development area and a developing electrode composed of a low-dielectric-constant member and a high-dielectric-constant member or metallic member. CONSTITUTION:A repulsive force operates on the liquid toner 7 in the opposite direction from its conveying direction owing to an increase in energy at the time of the conveyance of the liquid toner 7 to the development area. In this case, if there is a difference in the electrostatic capacity of the development area, the liquid crystal toner 7 having real charges concentrates on a stable part where electrostatic energy is small and electrostatic capacity is small. Therefore, the developing electrode 13 in the development area consists of the low-dielectric-constant member 15 and high-dielectric-constant member 14a or metallic member 14b to convey the liquid toner 7 which concentrates on the high-dielectric-constant member 14a or metallic member 14b to the development area. Consequently, the uniform solid black development is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic image developing device used in copying machines, printers, etc., and particularly to a developing device using a liquid developer.

[Conventional technology]

Conventionally, in recording processes such as electrophotography, electrostatic recording, and ionography used in copying machines and printers, basically the electrostatic latent image formed on a latent image carrier is visualized with a colored material. Records have been obtained through this process. Various methods have been proposed to create an electrostatic latent image, including exposing a negatively charged photoconductive material to light, and forming a latent image on a dielectric material using a multi-needle electrode or an ion emission gate. . In addition, there are various types, such as those in which the latent image carrier is used as the final recording medium, and those in which a visualized button is transferred from the latent image carrier to the recording medium. A so-called development process for visualization is common to these recording methods.

Development methods are broadly divided into dry development methods that use powder toner as a colored material and wet development methods that use liquid toner. Among the dry development methods, a magnetic brush development method in which toner is transported to a development area by magnetic force is currently widely used. However, since powdered toner is used as the coloring material, there is a problem in that toner powder smoke is likely to be generated and stain the inside and outside of the device. Another drawback is that a fixing process that applies heat or pressure is essential in order to fix the powder toner image to the recording medium.

On the other hand, in the wet development method, the latent image medium is immersed in a liquid developer in which colored particles are dispersed in a highly resistive organic liquid, and the latent image is developed by electrophoresis of the colored particles. However, there are problems such as colored particles adhering to background areas that are not originally desired to be developed, resulting in background smudges, and the need to dry the organic liquid in the dispersion medium, which increases the concentration of organic liquid vapor around the device. Ta.

As a liquid development method that solves these problems, U.S. Pat. Proposed. FIG. 4 shows an example of the configuration of a recording process using this method, and FIGS. 5(a) to 5(c) show the developing process. In this method, when a thin layer of liquid toner approaches a latent image carrier, toner protrusions grow from the thin toner layer toward the latent image carrier due to an electrostatic field.
Toner contacts and adheres only to the latent image area. Therefore, development is carried out without background smearing and without adhesion of excess dispersion medium.

[Problem to be solved by the invention]

However, with the vapor method, the electric field strength must be very high to extract the protrusions that grow from the toner film. According to experimental results, projections of liquid toner could be drawn out when the distance between the surface of the developing electrode and the image carrier was 0.3 or less and the potential difference between the developing electrode and the image carrier was 3 KV or more. However, the electric field strength at this time is 10K
It is V/mm or more, which is very large. This electric field strength is
This is the electric field strength that can cause gas dielectric breakdown and spark discharge in the atmosphere. Spark discharge causes various problems such as malfunction of electronic equipment, destruction of photoreceptor films, and generation of ozone.

In addition, the protrusions that grow from the liquid toner thin film are generated in the electric field concentration area between the electrostatic image on the carrier and the protrusions caused by minute fluctuations on the free surface of the liquid toner thin layer. In solid black areas, there was a problem in that the protrusions were unevenly generated, making it impossible to achieve uniform solid black development and causing omissions (Figure 5 (a), (b), (c)) left)
. In addition, when protrusions begin to form, the electric field becomes more concentrated in that area, so for electrostatic latent images that are close together, multiple protrusions are generated individually for each latent image. Instead of being formed, only the one protrusion that happened to be initially formed grows and reaches the latent image. For this reason, there was a problem in that fine latent images could not be reproduced and were destroyed (Fig. 5 (a), (b), (c) right side).

[Means to solve the problem]

The present invention provides an electrode facing an image carrier in a development region composed of a high dielectric constant member or a metal member and a low dielectric constant member having a certain thickness and partially existing on the surface of the member; It is characterized by having a carrier that transports liquid toner to a developing area while in contact with the carrier, and a mechanism that applies a true charge to the liquid toner that uniformly wets the surface of the toner transport carrier.

[Effect]

According to the present invention, by charging the liquid on the surface of the carrier that conveys the liquid toner, the toner can be concentrated in a plurality of areas on the development electrode in the development area. When a charger applies a charge of Ql per unit area to the liquid toner, the potential v1 of the toner becomes on the order of Ql/c+ due to the capacitance C1 of the toner transport carrier.

Since the liquid toner is transported from this state to the development area while holding the charge Q1, if the electrostatic capacitance C2 in the development area is 02<C+, the potential v2 of the toner becomes Q, /C2, and v2> The relationship vl holds true. From the standpoint of electrostatic energy, this means an increase of , which is thought to be due to the mechanical energy during transport of the liquid toner.

In other words, due to the increase in energy when the liquid toner is transported to the development area, a repulsive force acts on the toner in the opposite direction to the transport direction. In this case, if there is a size difference in the capacitance of the development area, the liquid toner having a true charge will concentrate in the small capacitance area where the electrostatic energy is small and stable. Therefore, by making the development electrode in the development area an electrode composed of a low dielectric constant member and a high dielectric constant member or a metal member, liquid toner is concentrated on the upper part of the high dielectric constant member or metal member and is transported to the development area. It becomes possible to do so.

The above-mentioned concentration of liquid toner acts as an insulating membrane in the development area and is effective in preventing spark discharge between the image carrier and the development electrode. Furthermore, in the development area, the carrier of the electrostatic latent image and the liquid toner come close to each other, and the electrolytic strength between them increases, so that protrusions are formed from the surface of the liquid toner and are drawn to the latent image area. In the present invention, when forming the protrusions, concentration of the liquid toner formed on the toner transport carrier causes
It is likely to be formed in the portion of the high dielectric constant member or metal member. For this reason, the formation of protrusions is not determined by chance positions due to minute fluctuations on the free surface of the thin liquid toner layer, but by the arrangement of the high dielectric constant member or metal member previously formed on the developing electrode. Even in such a solid black area, uniform solid black development is performed without uneven formation of protrusions. Furthermore, even for electrostatic latent images in close proximity,
A plurality of protrusions can be easily formed individually for each latent image portion, and even fine latent images can be faithfully reproduced without being crushed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention, which is used in an electrophotographic process using liquid development basically similar to that shown in FIG. 4 as a conventional example. The difference from the developing device 4 used in the conventional example is the developing electrode 13 and the toner transport carrier 17. As shown in FIG. 1, the developing electrode 13 in this embodiment includes a low dielectric constant member 15 and a high dielectric constant member or metal member 14a.
It has a laminated structure with a certain degree of thickness. Such a developing electrode can be obtained by laminating each plate and polishing a cut block.

In the charging region, the surface of the toner transport carrier 17 is uniformly wetted with the liquid toner 7, and a high dielectric constant member or a metal member 14b is installed on the back side of the transport carrier. A thin film of the liquid toner 7 given a true charge by the charger 2 is formed on the surface of the toner transport carrier 17 that has passed through such a charging area.

When the liquid toner 7 moves to the development area together with the toner transport carrier 17 in this state, since the development electrode has a laminated structure, the liquid toner 7 moves onto the high dielectric constant member or the metal member 14a on the transport carrier according to the principle described above. Concentrate on that part.

Figure 3 shows the developing area in the direction along the central axis of the photoreceptor 1. In both figures (a) to (c), the left side is a solid black area with uniform potential distribution, and the right side of the figure is a separated black area. This corresponds to an area where the electrostatic latent images are located close to each other. FIG. 3(a) shows a state where the liquid toner 7 is concentrated on the high dielectric constant member or the metal member 14a and swells on the toner transport carrier 17 as described above, and the electrostatic potential on the photoreceptor 1 is The image shows the state immediately before the liquid toner 7 is sucked.

The electric field in the developing section concentrates on the convex portion of the liquid toner 7 near the electrostatic latent image, but in this embodiment, since the convex portion of the liquid toner 7 is formed in advance, the electric field is concentrated on the convex portion of the liquid toner 7 as shown in FIG. 3(b). In the solid black portion, suction occurs from the swell of all the liquid toner 7 facing the electrostatic latent image 16a. Furthermore, in the areas where the electrostatic latent images are close, all the bulges of liquid toner 7 facing the electrostatic latent images 16b and 16c are attracted for each latent image portion, and the liquid toner 7 is removed as shown in FIG. Achieves a solid black image with no blemishes and fine development without any blemishes.

The developing electrode 13 in this embodiment had a laminated structure of a low dielectric constant member 15 and a high dielectric constant member or metal member 14a, but this was designed to reduce the gap between the high dielectric constant members or metal members. It goes without saying that the same development as described above can be performed with an electrode filled with a dielectric constant material, or an electrode where the high dielectric constant material or metal members 14a and 14b are integrated and the gap is filled with a low dielectric constant material. do not have.

〔Effect of the invention〕

As explained above, the present invention includes a mechanism that applies a true charge to the toner on the surface of the carrier that conveys the liquid toner to the development area, and a low dielectric constant member, a high dielectric constant member, or a metal member. By configuring the developing device with the developing electrode, spark discharge between the image carrier and the developing electrode, which causes various types of problems, can be prevented, and even black solid areas with no missing prints can be reproduced. This has the effect that the electrostatic latent image can be faithfully reproduced without being destroyed.

FIGS. 5(a) to 5(c) are diagrams showing the conventional developing process.

In the figure, ■ is a photoreceptor, 2 is a charger, 3 is an exposure device, 4 is a developer, 6 is a doctor blade, 7 is a liquid toner, 8 is a transfer roll, 9 is a cleaner, IO is an eraser, and 11 is a recording paper. . Further, 13 is a developing electrode, 14a and 1
4b is a high dielectric member or a metal member, 15 is a low dielectric constant member, and 16a.

16b and 16c are electrostatic latent images, 17 is a toner conveyance carrier, and 18 is a drive roller.

Agent Patent Attorney Susumu Uchihara

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a developing device according to an embodiment of the present invention, and FIG.
The figure shows the configuration of an electrophotographic recording apparatus according to an embodiment of the present invention, FIGS. 3(a) to 3(c) show the development process in this embodiment, and FIG. A diagram showing an example of the configuration of a toner developing device, 72 譜#+r-

Claims (1)

[Claims] an electrode facing the image carrier in a development area composed of a high dielectric constant member or a metal member and a low dielectric constant member having a certain thickness and partially existing on the surface of the member;
A liquid developing device comprising: a carrier that conveys liquid toner to a developing area while in contact with the electrode; and a mechanism that applies a true charge to the liquid toner that uniformly wets the surface of the toner conveying carrier.