JP2001013793A - Wet developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent blotting caused by the adhesion of excess dispersion medium to paper in a wet developing device. SOLUTION: In this wet developing device, developer 3 obtained by dispersing toner 3b in the dispersion medium 3a is supplied to a latent image carrier so as to visualize an electrostatic latent image formed on the latent image carrier. The device is provided with a developing roller 2 arranged by leaving a specified gap between the latent image carrier and the roller 2 at a developing part, rotating in a periphery direction while holding the developer 3 in a thin film state. and supplying the developer 3 to the latent image carrier at the developing part, a developer supply member supplying the developer 3 to the peripheral surface of the roller 2, a film thickness regulating roller 6 arranged by leaving the specified gap between the roller 2 and the roller 6, removing one part of the dispersion medium 3a from the roller 2 and regulating the film thickness of the developer 3 supplied to the roller 2 to be equal to or under a distance between the roller 2 and the latent image carrier, and a power source 1 applying voltage to the rollers 2 and 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet developing apparatus which is employed in an image forming apparatus such as an electrophotographic apparatus and which visualizes an electrostatic latent image formed on a latent image carrier with a liquid developer. .

[0002]

2. Description of the Related Art In various image forming apparatuses such as an electrophotographic apparatus, an electrostatic latent image is formed on the surface of a latent image carrier such as a photoconductive photosensitive member based on image information. There is provided a developing device that develops and visualizes the image.

As a developing device for an electrostatic latent image formed on such a latent image carrier, a developing solution (liquid phase developer) in which toner is dispersed in a dispersion medium is held on an outer peripheral surface of a developing roller. There is known a wet developing device that supplies the latent image to the surface of a latent image carrier and visualizes the electrostatic latent image with the attached toner.

[0004] As one of the wet developing apparatuses,
As described in JP-A-55-143565, the distance between the outer peripheral surface of the developing roller and the surface of the latent image carrier in the developing section, that is, the developing solution held on the outer peripheral surface of the developing roller is shorter than the developing gap. There is a non-contact liquid development technique for performing development by reducing the film thickness of a liquid crystal.

In such a non-contact liquid developing technique, since the thickness of the developing solution held by the developing roller is smaller than the developing gap, the distance between the developing solution and the surface of the latent image carrier in the developing section is reduced. A gap is formed between them. Then, when the electric charge constituting the electrostatic latent image formed on the latent image carrier reaches the developing section, the electric field of the electric charge causes the developing solution to protrude toward the electric charge and adhere to the latent image carrier. Then, the electrostatic latent image is developed.

[0006]

In the conventional non-contact liquid developing technique described above, in order to improve the elongation of the developing solution to the latent image carrier, the ratio of the dispersion medium is increased to reduce the concentration of the developing solution. If the thickness is reduced, an extra dispersion medium adheres to the latent image carrier, and when a toner image is transferred to a recording medium such as paper, so-called “bleeding” appears, and a sharp visible image cannot be obtained.

The mechanism of occurrence of bleeding when using a liquid developer in which a toner is dispersed in a dispersion medium in such a conventional non-contact liquid developing technique will be described with reference to FIG.

FIG. 7 is an explanatory view showing a liquid phase developer in a developing section formed by a latent image carrier and a developing roller in a conventional wet developing apparatus.

As shown in the figure, an electrostatic latent image portion 1a made of negative charges is formed on the latent image carrier 1. Then, in the developing section, when the liquid developer 3 in which the toner 3b is dispersed in the dispersion medium 3a held on the outer peripheral surface of the developing roller 2 and the peripheral surface of the latent image carrier 1 approach each other, FIG. As shown in a), the liquid phase developer 3 projects and adheres so as to extend toward the negative charge of the electrostatic latent image portion 1a, thereby visualizing the electrostatic latent image portion 1a.

Here, when the outer peripheral surface of the developing roller 2 is separated from the peripheral surface of the latent image carrier 1, as shown in FIG. 7B, the liquid developer 3 attached to the electrostatic latent image portion 1a is removed. Separated from the developing roller 2. The toner 3b in the attached liquid phase developer 3 is held on the electrostatic latent image portion 1a by the electrostatic force, but the dispersion medium 3a immediately moves to the electrostatic latent image portion as shown in FIG. It flows out of 1a and appears as bleeding when transferred onto a recording medium such as paper.

As described above, in the wet developing device, there is a problem that the sharpness and the image quality of the image transferred to the recording medium are deteriorated by the extra dispersion medium.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a wet developing apparatus capable of preventing the occurrence of bleeding due to an extra dispersion medium adhering to a recording medium.

[0013]

In order to solve this problem, a wet developing apparatus of the present invention supplies a liquid developer in which a toner is dispersed in a dispersion medium to a latent image carrier, and supplies the latent image carrier with the liquid developer. A wet developing device for visualizing an electrostatic latent image formed on a body, which is arranged at a developing section with a predetermined developing gap from a latent image carrier, and which holds a liquid developer in a thin film form and surrounds it. A developing member that rotates in the developing direction and supplies a liquid developer to the latent image carrier in the developing section, a developer supply member that supplies the liquid developer to the peripheral surface of the developing member, and a predetermined gap with the developing member. A film thickness regulating means which is arranged at a distance and removes a part of the dispersion medium from the developing member to make the film thickness of the liquid phase developer supplied to the developing member equal to or less than the distance between the developing member and the latent image carrier, And a power supply for applying a voltage to the developing member and the film thickness regulating means.

This prevents the extra dispersion medium from adhering to the latent image carrier, thereby preventing the occurrence of bleeding of the image transferred to the recording medium.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a liquid developer in which a toner is dispersed in a dispersion medium is supplied to a latent image carrier, and the liquid developer is formed on the latent image carrier. A wet developing device for visualizing an electrostatic latent image, which is disposed at a predetermined developing gap from a latent image carrier in a developing section, holds a liquid phase developer in a thin film shape, rotates in a circumferential direction, and develops. A developing member for supplying the liquid developer to the latent image carrier, a developer supplying member for supplying the liquid developer to the peripheral surface of the developing member, and a developing member arranged with a predetermined gap therebetween. Film thickness regulating means for removing the dispersion medium of the portion from the developing member so that the film thickness of the liquid phase developer supplied to the developing member is equal to or smaller than the distance between the developing member and the latent image carrier; And a power supply for applying a voltage to the means. It has the effect that the Do dispersion medium makes it possible to prevent the occurrence of bleeding due to the attachment.

According to a second aspect of the present invention, in the first aspect of the present invention, the toner is disposed between the film thickness regulating means and the developing section with a predetermined gap from the developing member, and the toner is subjected to liquid phase development. A concentration control electrode for controlling the surface concentration of the liquid phase developer on the peripheral surface of the developing member whose film thickness is regulated by the film thickness regulation means by attracting to the surface of the developer, a power supply for applying a voltage to the concentration control electrode, and a power supply And a concentration control electrode for controlling an applied voltage to the developing device, and a voltage application means for applying a voltage to the concentration control electrode to increase the viscosity of the liquid developer applied to the developing member without increasing the viscosity. This has the effect that the toner concentration on the film surface can be controlled.

According to a third aspect of the present invention, in the first or second aspect, the latent image carrier is disposed at a predetermined gap from the latent image carrier and supplied to the latent image carrier in the developing section. A wet developing device having a squeezing unit for removing a part of the dispersion medium from the liquid phase developer and a power supply for applying a voltage to the squeezing unit. The excess dispersion medium attached to the latent image carrier is transferred onto the recording medium. This has the effect of preventing bleeding.

According to a fourth aspect of the present invention, in the first aspect of the present invention, there is provided a voltage control means for controlling a voltage applied to the thickness control means. And has the effect that the amount and concentration of the liquid developer supplied to the latent image carrier can be controlled.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is an explanatory view showing a wet developing apparatus according to Embodiment 1 of the present invention together with a latent image carrier, and FIG. 2 shows the operation of a liquid film regulating roller in the wet developing apparatus of FIG. FIG. 3 is an explanatory view showing the operation of a density control electrode in the wet developing apparatus of FIG. 1. FIG. 4 is a state in which a liquid phase developer adheres to a latent image carrier from a developing roller in the wet developing apparatus of FIG. FIG. 5 is an explanatory diagram showing the operation of the squeeze roller in the wet developing device of FIG.

The wet developing apparatus according to the present embodiment supplies a developer (liquid developer) 3 held in a thin film state to the latent image carrier 1, and forms an electrostatic image formed on the latent image carrier 1. This is to visualize the latent image. In the wet developing device, the latent image carrier 1 is supplied to the latent image carrier 1 at a point where the developer 3 is supplied to the latent image carrier 1 by, for example, 400 μm or less, preferably 100 μm.
The developing roller (developing member) 2 is disposed close to the developing roller with a developing gap of at most m, more preferably at most 30 μm. However, the interval of the developing gap may be other than the above-mentioned numerical value. Further, the developing member 2 may be a belt instead of the roller as in the present embodiment.

A latent image carrier 1, which is a photoconductive photosensitive member, is formed in a drum shape, rotates clockwise in the illustrated case, and is electrostatically charged by a charging unit (not shown) and an exposure unit. Is formed. The developer 3 is attached to the electrostatic latent image,
A visible image corresponding to the electrostatic latent image is formed. Then, the developed visible image is transferred onto a recording medium by a transfer unit (not shown).

Here, the latent image carrier 1 may be a photoconductive photoreceptor or a member having a thin dielectric layer formed on a conductive substrate (electrostatic by position-selective charging using a multi-needle electrode or the like). Which can form a latent image). Also,
The developer 3 is for electrophotography in which a toner 3b is dispersed in a dispersion medium (Isoper: trade name) 3a which is a dielectric liquid. In the present embodiment, a developer charged to a positive charge is used. . Therefore, the visible image formed on the latent image carrier 1 is a toner image. Further, as the exposure means, a document image exposure method of irradiating a document light image, a light beam writing method, or the like is adopted.

In order to supply the developer 3 to the outer peripheral surface of the developing roller 2, a developer supplying roller (developer supplying means) 4 is provided rotatably in contact with the developing roller 2. A part of the developer supply roller 4 is immersed in the developer 3 stored in the developer container 5, and the developer 3 is attached to the outer peripheral surface of the developer supply roller 4, and the developer supply roller 4 is rotated counterclockwise, for example. Supply to 2.

In order to regulate the film thickness of the developing solution 3 supplied to the developing roller 2, a film thickness regulating roller (film thickness regulating means) 6
Is provided. As shown in FIG. 2, the film thickness regulating roller 6 is disposed close to the developing roller 2 so as not to contact the developer 3 held on the outer peripheral surface of the developing roller 2. A power supply 7 and a film thickness regulating roller applied voltage control device (film thickness regulating means applied voltage control means) 8 are connected between them.

As described above, the developer 3 is obtained by dispersing the positively charged toner 3b in the dispersion medium 3a which is a dielectric liquid. When a strong electric field acts while the liquid surface of the developing solution 3 is exposed to air, the toner 3b in the developing solution 3 follows the direction of the electric field, that is, the positively charged toner 3b moves toward a lower potential. It has been confirmed by experiments that the dispersion medium 3a raises the liquid surface in accordance with the strength of the electric field, regardless of the direction of the electric field, while moving in the liquid.

Applying this fact, when a voltage is applied between the developing roller 2 and the film thickness regulating roller 6 by the power source 7 and the film thickness regulating roller applying voltage controller 8, the developing roller 2 and the film thickness regulating roller 6 An electric field is formed between the developing roller 2 and the developing solution 3 on the outer peripheral surface of the developing roller 2 as the developing roller 2 and the film thickness regulating roller 6 rotate, as shown in FIG. Adhere to. Since the potential of the film thickness regulating roller 6 is higher than the potential of the developing roller 2, the positively charged toner 3 b migrates in the liquid and is attracted to the developing roller 2 side.

When the developing roller 2 and the film thickness regulating roller 6 further rotate, the developer 3 adhering to the film thickness regulating roller 6 is removed.
Are separated, and a part of the dispersion medium 3a is wiped off by the film thickness regulating roller 6 as shown in FIG.

The film thickness regulating roller 6 to which the dispersion medium 3a has adhered is wiped by the cleaning blade 9 on the dispersion medium 3a.

As described above, the amount of the dispersion medium 3a that is wiped off by the film thickness regulating roller 6 changes depending on the voltage between the developing roller 2 and the film thickness regulating roller 6, so that the film thickness regulating roller applied voltage control device 8 By controlling the applied voltage, the amount (film thickness) and concentration of the developer 3 held by the developing roller 2 can be controlled.

Here, it is desirable that the dispersion medium 3a, which is a dielectric liquid, has a high dielectric constant. Preferably it is two or more.
It is also desirable that the electric resistance is sufficiently high. 1 × 10 ¹⁰ Ω
cm or more, preferably 1 × 10 ¹³ Ωcm or more.

The developer 3 whose film thickness and density are regulated by the film thickness regulating roller 6 is in a state where the toner 3b is attracted to the developing roller 2 side. A concentration control electrode 11 is provided for drawing.

As shown in FIGS. 1 and 3, the density control electrode 11 is disposed close to the developing roller 2 so as not to contact the developing solution 3 held on the outer peripheral surface of the developing roller 2. A power supply 17 and a concentration control electrode applied voltage control device (concentration control electrode applied voltage control means) 18 are connected between the concentration control electrodes 11.

As shown in FIG. 3, the voltage applied to the film thickness regulating roller 6 by the power supply 17 and the density control electrode applied voltage controller 18 is such that the developer 3 does not adhere to the density control electrode 11. When a reverse voltage is applied, a reverse electric field is formed between the developing roller 2 and the density control electrode 11, and the toner 3 b attracted to the developing roller 2 by the film thickness regulating roller 6 is attracted to the surface of the developer 3. Come.

As described above, by controlling the voltage applied to the concentration control electrode 11 by the concentration control electrode application voltage controller 18, the developer 3 can be developed without increasing the viscosity of the developer 3.
The density of the toner 3b on the surface can be adjusted.

The developing solution 3 whose film thickness and concentration are regulated by the film thickness regulating roller 6 and whose concentration on the liquid surface is adjusted by the concentration controlling electrode 11 is regulated so that the film thickness is regulated to be equal to or less than the gap of the developing gap. To reach the developing section.

The developing roller 2 is formed of a conductive member, and a power supply 27 is provided for applying a DC voltage to the developing roller 2. When a voltage is applied from the power supply 27 to the developing roller 2, an electric field is formed between the developing roller 2 and the latent image carrier 1.

When an electric field acts on the developing solution 3 in the form of a thin film held on the outer peripheral surface of the developing roller 2, projections of the developing solution 3 are generated in the developing section as shown in FIG. In this state, when the electrostatic latent image portion 1a made of a negative charge arrives at the developing portion, the protrusion of the developing solution 3 extends in accordance with the distribution of the negative charge, and the developing solution is placed on the electrostatic latent image portion 1a of the latent image carrier 1. 3 adheres.

Here, as described above, the concentration control electrode 11
As a result, the toner 3b in the developing solution 3 is gathered near the surface of the developing solution, so that the toner 3b on the developing roller 2 side is diluted and the viscosity of the developing solution 3 is low, so that the toner 3b tends to expand, and the toner 3b gathers at the tip of the projection. The efficiency of attaching the toner 3b to the electrostatic latent image portion 1a is improved.

The developing solution 3 attached to the electrostatic latent image portion 1a includes
An extra dispersion medium 3a is still included. Therefore, if the extra dispersion medium 3a adheres at the time of transfer to the recording medium, the image quality is reduced. Therefore, in order to remove such a dispersion medium 3a, a squeeze roller (squeeze means) 31 is used.
Is provided.

As shown in FIG. 5, the squeeze roller 31 is disposed close to the latent image carrier 1 so as not to come into contact with the developer 3 attached to the electrostatic latent image portion 1a. A power supply 37 is provided for applying a voltage. When a voltage sufficiently higher than that of the electrostatic latent image portion 1a is applied from the power source 37 to the squeeze roller 31, the electric field formed between the squeeze roller 31 and the electrostatic latent image portion 1a acts on the developer 3. As a result, the liquid surface rises and eventually adheres to the squeeze roller 31. Since the potential of the squeeze roller 31 is higher than the potential of the electrostatic latent image portion 1a, the positively charged toner 3b is attracted to the electrostatic latent image portion 1a and stays there, and only the excess dispersion medium 3a is removed. Adheres to

Further, the latent image carrier 1 and the squeeze roller 31
Is rotated, the developer 3 adhering to the squeeze roller 31 is separated, and as shown in FIG.
Is wiped off by the squeeze roller 31.

The squeeze roller 31 to which the dispersion medium 3a adheres is cleaned by the cleaning blade 32.
a is wiped off.

As described above, according to the present embodiment, since the film thickness of the developer 3 supplied to the developing roller 2 is regulated by the film thickness regulating roller 6 and the excess dispersion medium 3a is removed, the latent An extra dispersion medium 3 a of the developer 3 is added to the image carrier 1.
Is prevented from adhering. Thereby, the occurrence of bleeding due to the extra dispersion medium 3a adhering to the recording medium is prevented, and the image quality can be improved.

(Embodiment 2) FIG. 6 is an explanatory view showing a wet developing apparatus according to Embodiment 2 of the present invention together with a latent image carrier. The same components as those described in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the present embodiment, a squeeze electrode 41 is provided instead of the squeeze roller 31 in the wet developing apparatus described in the first embodiment.

With such a squeeze electrode 41,
After the development, the excess dispersion medium 3a is removed from the developing solution 3 attached to the electrostatic latent image portion 1a by an electric field formed between the electrostatic latent image portion 1a and the squeeze electrode 41. The image quality is prevented from deteriorating due to the extra dispersion medium 3a adhering during transfer.

[0048]

As described above, according to the present invention, since the film thickness of the liquid developer supplied to the developing member is regulated by the film thickness regulating means and the excess dispersion medium is removed, the latent image is removed. The extra dispersion medium of the liquid phase developer is prevented from adhering to the carrier. As a result, the occurrence of bleeding due to the extra dispersion medium adhering to the recording medium is prevented, and an effective effect of improving the image quality can be obtained.

Since the toner concentration on the liquid film surface can be controlled without increasing the viscosity of the liquid phase developer applied to the developing member by the density control electrode, it is possible to increase the developing density without slowing down the printing speed. An effective effect that it becomes possible is obtained.

Since the excess dispersion medium attached to the latent image carrier can be removed by the squeezing means, the excess dispersion medium is prevented from being transferred onto the recording medium and bleeding, and the image quality can be improved. An effective effect that it becomes possible to achieve this is obtained.

The amount of the dispersion medium to be wiped from the developing member can be adjusted by controlling the voltage applied to the film thickness regulating means. Thus, an effective effect that the print density can be arbitrarily controlled can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a wet developing device according to a first embodiment of the present invention together with a latent image carrier;

FIG. 2 is an explanatory diagram showing an operation of a liquid film regulating roller in the wet developing device of FIG. 1;

FIG. 3 is an explanatory diagram showing an operation of a concentration control electrode in the wet developing device of FIG.

FIG. 4 is an explanatory view showing a state in which a liquid phase developer has adhered to a latent image carrier from a developing roller in the wet developing device of FIG. 1;

FIG. 5 is an explanatory diagram showing an operation of a squeeze roller in the wet developing device of FIG. 1;

FIG. 6 is an explanatory diagram showing a wet developing device according to a second embodiment of the present invention together with a latent image carrier.

FIG. 7 is an explanatory view showing a liquid phase developer in a developing section formed by a latent image carrier and a developing roller in a conventional wet developing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Latent image carrier 2 Developing roller (developing member) 3 Developing liquid (liquid phase developer) 3a Dispersion medium 3b Toner 4 Developer supplying roller (developing liquid supplying means) 6 Film thickness regulating roller (film thickness regulating means) 7 Power supply 8 Thickness regulation roller applied voltage control device (thickness regulation means applied voltage control means) 11 Concentration control electrode 17 Power supply 18 Concentration control electrode applied voltage control device (Density control electrode applied voltage control means) 27 Power supply 31 Squeeze roller (Squeeze means) 37 power supply 41 squeeze electrode (squeeze means)

Claims (4)

[Claims] 1. A wet developing apparatus for supplying a liquid developer in which a toner is dispersed in a dispersion medium to a latent image carrier to visualize an electrostatic latent image formed on the latent image carrier. A liquid developer is disposed in the developing section at a predetermined developing gap from the latent image carrier, and is rotated in the circumferential direction while holding the liquid developer in a thin film form; A developing member for supplying an image carrier, a developer supplying member for supplying a liquid developer to a peripheral surface of the developing member, a developing member disposed at a predetermined gap from the developing member, and a part of the dispersion medium. A film thickness regulating means for removing a film thickness of the liquid phase developer supplied from the developing member to the developing member so as to be equal to or less than an interval between the developing member and the latent image carrier; and the developing member and the film. A power source for applying a voltage to the thickness regulating means. Developing device. 2. A method according to claim 1, further comprising the step of: disposing a predetermined gap from said developing member between said film thickness regulating means and said developing section, attracting said toner to a surface of said liquid phase developer, and forming said film by said film thickness regulating means. A concentration control electrode for controlling the surface concentration of the liquid phase developer on the peripheral surface of the developing member whose thickness is regulated; a power supply for applying a voltage to the concentration control electrode; and a concentration control for controlling the applied voltage to the power supply. 2. An electrode application voltage control means.
The wet developing device according to claim 1. 3. A squeezing means which is arranged at a predetermined gap from said latent image carrier and removes a part of a dispersion medium from a liquid phase developer supplied to said latent image carrier in said developing section; 3. The wet developing apparatus according to claim 1, further comprising a power supply for applying a voltage to the squeezing means. 4. The wet developing apparatus according to claim 1, further comprising a voltage control means for controlling a voltage applied to said film thickness control means.