JP2672196B2 - Wet electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet electrophotographic apparatus for developing an electrostatic latent image by supplying liquid toner to the photosensitive surface of a photosensitive material which has been subjected to imagewise exposure to form an electrostatic latent image.

[0002]

2. Description of the Related Art Conventionally, a photosensitive material on which an electrostatic latent image is formed by being imagewise exposed after being charged, for example, an ELP master (a photoconductive layer composed of ZnO and a binder is provided on a waterproof and conductive-treated support. Wet electrophotographic apparatus that supplies liquid toner (developing solution formed of toner particles, charge control agent, dispersion medium, etc.) to a photoconductor laminated on a substrate to develop the electrostatic latent image formed on the master. Is proposed.

This wet electrophotographic apparatus has two adjacent electrophotographic apparatuses.
An electrode consisting of a sheet of metal plate (the metal plate facing the photosensitive surface of the photosensitive material is called the "developing electrode", the metal plate facing the back surface side of the photosensitive material is called the "back electrode") is provided between these electrodes. A bias voltage is applied or the electrodes are short-circuited, and liquid toner is flown between the electrodes while passing through the master for development.

When the liquid toner is supplied to the master passing between the electrodes, the toner particles contained in the liquid toner adhere to the latent image charge forming the electrostatic latent image on the master, that is, are electro-deposited and electrostatically charged. The latent image is visualized.

[0005]

However, in the above-mentioned conventional wet electrophotographic apparatus, in response to the latent image charge on the master being neutralized by the toner particles in the developing solution, the back electrode is provided with a photoreceptor. A charge having a polarity opposite to that of the charge charged on the back surface opposite to the photosensitive surface, that is, a charge having a polarity opposite to that of the toner particles is induced, and the toner particles adhere to the back electrode. Therefore, there is a problem that the back electrode becomes dirty.

Further, the amount of toner particles attached to the back electrode increases as the number of developing treatments increases, and a non-conductive film is formed on the back electrode. Since this non-conductive film inhibits the transfer of electric charges, as the development progresses, the electric charge of the toner particles on the film creates a so-called charged state, which causes the toner particles to adhere to the photosensitive surface. However, there is a problem in that the plate surface density decreases.

Further, if this coating film is thickly deposited, there is a problem that it peels off in a solid state and adheres to a portion of the master where the latent image is not formed to cause toner stain on the master.

Therefore, as schematically shown in FIG.
It has been proposed to support the back surface of the master support with a plurality of protrusions formed by roughening the back electrode (see Japanese Patent Laid-Open No. 61-11766). FIG.
As shown in FIG. 2, there has been proposed a device in which a conductive net is applied as a back electrode (see Japanese Utility Model Publication No. 56-14525). According to these conventional techniques, since the back electrode is in contact with the support of the master, the charge on the support is neutralized by the charge charged on the support, and the toner particles are electrodeposited on the back electrode. The amount can be reduced.

However, since the part of the back electrode which is not in contact with the support is close to the support, there is a gap between the part of the back electrode which is not in contact with the support and the part of the support which faces this part. The electric field strength in the (gap part) becomes stronger,
Toner particles (which are positively charged) are likely to be electrodeposited on the back electrode. In addition, since the area of the back electrode or the support body in the gap portion is large, the electrostatic attraction force that acts becomes strong, and the master is attracted to easily cause defective passage.

Further, in the case of the roughened back electrode, since the electrode is flat, the developer between the back electrode and the master is difficult to be removed and remains as a liquid film. It becomes difficult to obtain a reliable electrical contact between the support and the support, which facilitates electrodeposition.

Further, when this conductive net is used,
Since it is difficult to maintain a flat state, uneven contact is likely to occur and image quality stability is poor. If a support plate is provided to maintain the flat state, the liquid film remains as in the above case, and the same problem occurs.

Japanese Unexamined Patent Publication (Kokai) No. 58-4156 discloses that the developing electrode, which is arranged to face the photosensitive layer, is made of a foam metal material. This technique aims to supply more developer between the photosensitive layer and the developing electrode by utilizing the high porosity of the metal foam material. Further, the liquid is sent from the developing electrode side so that the developing electrode and the photoconductor do not come into contact with each other. However, since the back electrode is the same as the conventional one, there is a problem that toner particles adhere to the back electrode.

Further, the back electrode needs to be regularly cleaned and needs to be removed when an abnormality such as defective passage of the photosensitive material occurs. In such a case, in the conventional electrophotographic apparatus, it is necessary to disassemble the entire developing section. There is a problem and maintainability is not good. Further, when the photosensitive material is guided to the developing portion, the back surface of the photosensitive material is soiled by the toner or the like attached to the guide surface.

The present invention has been made to solve the above problems, and can make the toner concentration on the photosensitive surface of the photosensitive material uniform, and further reduce the amount of toner particles attached to the back electrode. It is an object of the present invention to provide a wet electrophotographic apparatus capable of smoothly moving a photosensitive material.

In addition to the above objects, it is another object of the present invention to provide a wet electrophotographic apparatus which can facilitate the attachment / detachment of the back electrode and improve the maintainability.

Further, in addition to the above objects, it is an object of the present invention to obtain a wet electrophotographic apparatus which can surely prevent the back surface of the photosensitive material from being soiled.

[0017]

In order to achieve the above object, the invention according to claim 1 is a developing electrode which is opposed to the first surface of the photosensitive material on which the electrostatic latent image is formed in a non-contact state. A second surface of the conductive material, which is arranged opposite to the developing electrode and is in contact with the second surface of the photosensitive material opposite to the first surface, and which is made of a conductive material having a three-dimensional mesh structure. It is configured to include a back electrode in which a surface formed by connecting portions in contact with the surface is a flat surface.

According to a second aspect of the invention, a plate-shaped developing electrode facing the photosensitive surface of the photosensitive material on which an electrostatic latent image is formed by imagewise exposure, and a conductive material having a three-dimensional network structure are used. A plate-shaped back electrode facing the surface opposite to the photosensitive surface,
Conveying means for conveying the photosensitive material between the developing electrode and the back electrode, toner supplying means for supplying liquid toner between the developing electrode and the photosensitive material to visualize an electrostatic latent image, and the rear electrode. A supporting frame body, a guide plate provided at an end portion of the frame body on the insertion side of the photosensitive material for guiding the photosensitive material between a developing electrode and a back electrode, and a detaching / attaching for detaching the back electrode from the frame body. And means. This guide board is
It is effective to integrate it with the back electrode.

[0019]

The photosensitive material on which the electrostatic latent image of the present invention is formed is supplied between the developing electrode and the back electrode in a state of being in contact with the back electrode while being supplied with liquid toner to be developed. As a result, the latent image charge on the photosensitive surface of the photosensitive material is neutralized by the toner particles in the liquid toner, so that the back surface (second surface) opposite to the photosensitive surface (first surface) of the photosensitive material. ), The charge of the opposite polarity to the latent image charge, which escapes to the back electrode,
These are neutralized with the charges flowing from the developing electrode to the back electrode.

By the way, when the photosensitive material passes between the developing electrode and the back electrode, in order to improve the flow of charges,
The second surface of the photosensitive material needs to be slid in contact with the back electrode. In the present invention, the back electrode is made of a conductive material having a three-dimensional network structure. Further, the back electrode is formed such that the surface formed by connecting the portions of the conductive material that are in contact with the second surface of the photosensitive material is a flat surface. Since the back electrode of the present invention has a three-dimensional mesh structure, the contact portion with the second surface of the photosensitive material is the tip of a wire as shown in FIG. 10, and the contact portion has a small area. Further, the distance between the non-contact portion and the second surface of the photosensitive material is sufficiently long as compared with the case of a conductive net or a roughened electrode, and the electric field strength of the non-contact portion is sufficiently small. Therefore, the area where the toner is electrodeposited by the electric field is small, and the electrostatic attraction force is also small. Therefore, it is possible to reduce the amount of toner electrodeposited and prevent defective conveyance of the photosensitive material. Further, since the back electrode of the present invention has a three-dimensional mesh structure, the liquid toner that has flown around to the second surface side of the photosensitive material flows inside the back electrode and the liquid film does not remain. Therefore, reliable electrical contact is possible. Further, since it is three-dimensional, it can have sufficient rigidity to maintain the flatness, and uniform contact is possible. Further, since the surface of the back electrode is almost the same as the flat surface, it does not give a resistance force when the photosensitive material slides, and maintains the gap between the photosensitive surface and the developing electrode at a predetermined size. Thus, the photosensitive material can be supported, and the developing accuracy can be improved.

The thickness sufficient for the liquid toner to flow inside the back electrode is 1/3 of the distance between the developing electrode and the back electrode.
It is preferable that the average diameter of the conductive material is 1/3 or less of the average mesh pitch.

Further, in the present invention, a frame for supporting the back electrode and a mounting means for removably mounting the back electrode on the frame may be provided. In this way, when maintenance such as cleaning is required, only the back electrode can be easily removed, and maintenance workability is improved. Furthermore, since the back electrode is attached to the frame, the back electrode does not become larger than necessary,
It leads to cost reduction.

Guide means for guiding the conveyed photosensitive material between the developing electrode and the back electrode can be provided on the photosensitive material input side of the frame. If this guiding means is made of a conductive material having a three-dimensional mesh structure and is integrated with the back electrode, all the portions of the developing portion that come into contact with the photosensitive material will be a conductive material having a three-dimensional mesh structure, and the photosensitive material It is possible to reliably prevent dirt on the back surface of the.

[0024]

FIG. 3 shows an embodiment of a wet electrophotographic apparatus 10 to which the present invention is applied. FIG. 1 is a side view showing an outline of a developing unit of the wet electrophotographic apparatus 10.

As shown in FIG. 3, the wet electrophotographic apparatus 10 has a rectangular cross section, and the outer circumference is covered by the cover 1.
Covered with 1. The wet electrophotographic apparatus 10 has legs 13 attached to the four corners of the bottom, and is installed on the floor by the legs 13. Casters 15 are attached near the legs 13 and are used when the wet electrophotographic apparatus 10 is moved.

As shown in FIG. 3, a long photosensitive member (hereinafter referred to as "master"), which is a photosensitive material wound in a roll shape, is formed on an upper portion of the inside of the wet electrophotographic apparatus 10 covered with the cover 11. A paper feeding unit 14 is provided in which the paper feeding device 12 is loaded.

The master 12 used in this embodiment is shown in FIG.
As shown in FIG. 3, the conductive waterproof layer 3 is formed on the support 34 made of paper.
6, the intermediate layer 38, and the photosensitive layer (ZnO) 40 are sequentially stacked. A conductive waterproof layer 42 is also attached to the back surface side of the support 34. The thickness of the support 34 is about 175 μ
m, and the thickness of the photosensitive layer 40 is about 10 μm. Further, the conductive waterproof layer having a surface resistance value of 10 ⁸ to 10 ¹¹ Ω is used. In FIG. 3, two roll-shaped masters 12A, 1
2B is shown and they differ in size (width dimension).

A charging section 16 for charging the surface of the master 12 pulled out from the sheet feeding section 14 is arranged on the side of the sheet feeding section 14. Further, an exposure unit 18 is arranged on the side and the lower part of the charging unit 16. Further, the charging unit 16 and the paper feeding unit 1
4 and 4 and Katsu 3
0 is provided, and the master 12 pulled out to a predetermined length from the paper feeding unit 14 is cut to have a predetermined length.

An exposure table 46 is erected on the exposure unit 18. A plurality of suction holes are formed on the surface of the exposure table 46, and a negative pressure is supplied from a negative pressure supply means (not shown). The surface of the exposure unit 46 is charged by the charging unit 16 and the master 12 cut into a predetermined length is conveyed and adsorbed. Further, the exposure unit 46 is provided with an exposure lamp 48 that irradiates a document placed on the document table 26 with light, and a mirror 50 that reflects the light emitted from the exposure lamp 48 onto the document to the exposure table 46. A lens 52 is arranged between the document table 26 and the mirror 50.

As a result, the image of the document placed on the document table 26 is irradiated with light from the exposure lamp, and the reflected light is irradiated to the master 12 on the exposure table 46 via the lens 52 and the mirror 50. , The master 12 is imagewise exposed.

A developing section 20 is arranged below the exposing section 18. In the developing section 20, a developing box 54 is arranged as shown in FIGS. The developing box 54 is formed in a box shape whose upper side and one side are opened. A conveying roller 60 is arranged on the inlet side of the master 12 between the opposing side walls 56 and 58 of the developing box 54, and both ends of the rotary shaft are rotatably supported by the side walls 56 and 58, respectively. Side wall 56 of rotating shaft
A gear 62 and a sprocket wheel 64 are fixed to the side.

Further, the end of the rotary shaft supported by the side wall 56 penetrates the side wall 56 and projects, and a sprocket wheel 66 is fixed to the tip. A chain 68 is wound between the sprocket wheel 66 and a sprocket wheel fixed to a drive shaft of a motor (not shown), and the rotational driving force of the motor (not shown) is transmitted to the chain 68.
The transport roller 60 rotates.

A skewered roller 70 is provided above the transport roller 60.
Are arranged in contact with each other. Both ends of the rotary shaft of the skewered roller 70 are supported by the side walls 56 and 58 via bearings (not shown). A gear 74 is fixed to the side wall 56 side of the rotary shaft of the skewer roller 70, and the gear 74 meshes with the gear 62 to which the conveying roller 60 is fixed. As a result, the rotational driving force transmitted to the transport roller 60 is transmitted to the skew roller 70.

On the opposite side of the conveying roller 60, that is, on the exit side of the master 12, a conveying roller pair 76 is provided on the side walls 56, 5.
It has been passed over between eight. The carrying roller pair 76 is arranged at a position lower than the carrying roller 60 and the skew roller 70. A sprocket wheel 78 is fixed to the end of the lower roller of the conveying roller pair 76 on the side wall 56 side.
A chain 80 is wound between the sprocket wheel 78 and the sprocket wheel 64. As a result, the rotational driving force transmitted to the transport roller 60 is transmitted to the transport roller pair 76. The master 12 transported from the exposure unit 18 is inserted between the transport roller 60 and the skew roller 70, and is delivered obliquely downward toward the transport roller pair 76.

A developing electrode 82 and a back electrode 84 are provided between the conveying roller 60, the skew roller 70 and the conveying roller pair 76.
Is arranged. The developing electrode 82 and the back electrode 84 are inclined so that the end portions on the conveying roller pair 76 side are located downward. Further, a gap 86 is formed between the developing electrode 82 and the back electrode 84, and the master 12 sent out between the transport roller 60 and the skew roller 70 passes diagonally downward through the gap 86, It is inserted between the pair of transport rollers 76.

The developing electrode 82 is formed of a metal plate and is located above the transport path of the master 12 in correspondence with the photosensitive surface side of the master 12. Also, the back electrode 84
Is located in the lower part of the transport path of the master 12 corresponding to the conductive waterproof layer 42 side of the master 12.

The back electrode 84 is a developing box 5 which is a frame.
It is housed in a rectangular hole 90A formed in the central portion of the back plate 90 housed in 4. Male screws 110, which form a part of the attaching / detaching means, project downward from the apparatus at the four corners of the peripheral edge of the rectangular hole 90A. The back electrode 84 is attached to the support plate 112. The support plate 112 has circular holes 114 at its four corners at positions corresponding to the male screws 110. Where male screw 1
The support plate 112 is fixed to the back plate 90 when 10 penetrates the circular hole 114 and is screwed together with the male screw 110 with the nut 116 which constitutes the attaching / detaching means.

The back plate 90 is slightly bent in the direction in which the carry-in side of the master 12 is separated from the developing electrode 82, and the master 12 is bent to the developing electrode 82 and the back electrode 84 at this bent portion.
A guide plate 118 to be received between and is attached.
The guide plate 118 and the back electrode 84 are flush with each other.

As shown in FIG. 5 and FIG. 10 which is an enlarged view of FIG. 5, the back electrode 84 is formed of a foam metal plate which is a conductive material having a three-dimensional mesh structure. As shown in FIGS. 5 and 10, the foam metal plate (back electrode 84) is
It has a three-dimensional network structure, with many holes penetrating the front and back surfaces, and the front and back surfaces have an uneven shape when viewed microscopically, but since the hole diameter is extremely small (high density), it is macroscopic. As you see, the front and back surfaces are flat. That is, the surface formed by connecting the contact portion with the back surface of the master 12 made of a conductive material is flat. This macroscopic planar shape means that the resistance when the master 12 slides on the back electrode 84 is equal to or less than the resistance when sliding on a normal plane. In order to set such a sliding resistance within a predetermined range, the number of cells of the foam metal plate may be in the range of 5 to 100 cells / inch, preferably 20 to 50 cells / inch.
In other words, as shown in FIG. 10, the average value of the diameter d of the conductive material may be 1/3 or less of the average value of the mesh pitch P. Further, the average value of the distance t between the contact portion of the conductive material with the back surface of the master 12 and the non-contact portion is such that the toner particles are not electrodeposited by the electric field generated between the back surface and the non-contact portion of the master. Good to do.

Celmet (trade name "Sumitomo Electric Industries, Ltd.") is commercially available as this foam metal plate (rear electrode 84). There are several types of celmet depending on the number of cells and the specific surface area, but in the present embodiment, the number of cells is 26 to 35 cells / inch, and the specific surface area is 2,500 m ^2.
"Part number # 4" of / m ³ is applied.

As shown in FIG. 1, the side of the guide plate 118 in the foam metal (back electrode 84) is the guide plate 11.
The thickness is gradually reduced toward the end on the 8th side. Therefore, the master 12 guided by the guide plate 118 does not have a problem of being caught on the edge of the metal foam plate (back electrode 84), and the master 12 can be smoothly transported. The metal foam plate has a sufficient thickness to allow the liquid toner to flow therein. This thickness is preferably 1/3 or more of the distance between the developing electrode and the back electrode.

As shown in FIG. 1, the foam metal plate (back electrode 84) is short-circuited with the developing electrode 82. As a result, the master 12 thus charged is charged with the developing electrode 82 and the back electrode 84.
When passing through a gap 86 between the developing electrode 8 and the developing electrode 8 due to electrostatic induction.
An electric field is generated between the second electrode and the back electrode 84, and charges of opposite polarities are induced in the respective electrodes.

As shown in FIG. 2, a liquid toner supply box 92 is disposed on the guide plate 118 between the developing electrode 82 and the skew roller 70. The liquid toner supply box 92 is connected to a liquid toner tank 93 (see FIG. 1) by a pipe line 91, and a supply pump 95 is arranged in the middle of the pipe line 91. By the operation of the supply pump 95, the liquid toner is supplied to the liquid toner supply box 92.

The liquid toner supply box 92 is provided with a liquid toner discharge port which opens along the width direction of the master 12 between the developing electrode 82 and the back electrode 84. From this liquid toner ejection port, liquid toner is ejected between the developing electrode 82 and the photosensitive surface of the master 12, and is supplied to the surface of the master 12 which is conveyed obliquely.

As shown in FIG. 3, a fixing unit 22 is arranged beside the developing unit 20. In this fixing unit 22, a pair of conveying rollers 94 is arranged on the developing unit 20 side. The master 12 delivered from the developing unit 20 is inserted between the pair of transport rollers 94.

Further, in the fixing unit 22, a conveying roller pair 96 is arranged at a position higher than the conveying roller pair 94 on the exit side of the master 12. Further, a guide 98 is arranged between the conveying roller pair 96 and the conveying roller pair 94, and is inclined obliquely upward so that the end portion on the conveying roller pair 96 side is higher than the end portion on the conveying roller pair 94 side. Further, two lamps 100 are arranged above the guide 98.

As a result, the master 12 sent out from the pair of conveying rollers 94, guided by the guide 98 and conveyed obliquely upward is fixed by heating by the lamp 100.

A stacking unit 24 is arranged outside the device on the side of the pair of transport rollers 96. The master 12 sent from the pair of transport rollers 96 is stacked in the stacking unit 24.

Next, the operation of this embodiment will be described.

The master 12 loaded in the paper feeding unit 14 is drawn out to the charging unit 16 and is sent to the exposure table 46 of the exposure unit 18 while the surface is uniformly charged. When the master 12 has a predetermined length, that is, a length that allows the master 12 to fit on the exposure table 46, it is cut by the cutter 30 to have a predetermined length.

The master 12 cut to a predetermined length and sent to the exposure table 46 is attracted to the exposure table 46. From this state, the image of an original document (not shown) placed on the original table 26 is irradiated with the light of the exposure lamp 48, and the reflected light is reflected by the lens 5.
2. Irradiation onto the master 12 through the lens 50.
As a result, the master 12 on the exposure table 46 is image-exposed and an electrostatic latent image is formed on the surface.

The master 12 on which the electrostatic latent image is formed is inserted between the conveying roller 60 and the skew roller 70 of the developing section 20, and is inserted into the gap 86 between the developing electrode 82 and the back electrode 84. When the master 12 is inserted between the developing electrode 82 and the back electrode 84, liquid toner is supplied from the liquid toner supply box 82 to the surface of the master 12.

On the back side of the master 12 inserted between the developing electrode 82 and the back electrode 84, a metal foam plate (back electrode 84) is slidably contacted and slid downwardly between the pair of transport rollers 76. Be transported.

The master 12 is the developing electrode 82 and the back electrode 8
4 and the developing electrode 82 by electrostatic induction.
Then, an electric field is generated between the front surface of the master 12, the back surface of the master 12, and the back electrode 84. In this electric field, the positively charged toner particles in the liquid toner adhere to the electrostatic latent image formed by the negative charges formed on the surface of the master 12, and the electrostatic latent image is developed by the toner particles.

At this time, although a negative charge remains on the surface of the back electrode 84, the entire foam metal (back electrode 84) is a conductor, and the tip of the foam metal and the back surface side of the master 12 are in contact with each other. So this negative charge is master 1
Neutralize with the positive charge on the back side of 2 (FIG. 10). Further, since the toner particles are guided to the concave portions, that is, the holes of the metal foam plate, and no liquid film is formed on the surface of the back electrode 84, the amount of the toner particles attached to the back electrode 84 is reduced. Therefore, the electrical connection between the back electrode 84 and the master 12 is always maintained, the amount of toner adhered to the photosensitive surface of the master 12 can be made uniform, and the density of the master 12 can be made substantially uniform. . Further, since the distance t between the contact portion and the non-contact portion of the foam metal master with the back surface is long, the electric field strength is small and the toner is not electrodeposited. In order to clarify this effect, as shown in FIG. 6, when the development is performed using a conventional grooved back electrode (see arrow A in FIG. 6), the metal foam plate (celmet, Comparison was made with the case of using the product number # 4) as the back electrode 84 (see arrow B in FIG. 6). In the experiment, the toner was made to adhere to the entire solid surface, that is, the entire photosensitive surface.

According to the results of this experiment, both the reflection densities at the tip of the master 12 are around 1.3,
In the conventional type, the reflection density gradually decreases as it reaches the rear end of 2, and at the point 30 cm from the front end, the reflection density decreases by about 0.3. On the other hand, in the present embodiment, the decrease in concentration is 0.
It can be seen that it is suppressed to around 1.

From the number of plate-making / reflective density characteristics shown in FIG. 7 and the number of plate-requiring required amount of electric charges per unit area shown in FIG. It can be seen that the amount holds a substantially constant value.

The master 12 developed by the developing section 20 is sent to the fixing section 22 and is heated and fixed on the toner that adheres to the surface of the master 12 and forms an image. The master 12 after being fixed by the fixing unit 22 is accumulated in the accumulating unit 24.

Here, the back electrode 84 needs to be cleaned or replaced at predetermined intervals. In such a case, by removing the nut 116 from the male screw 110, the back electrode 84 together with the support plate 112 can be easily removed from the back plate 90, thus improving maintainability. After cleaning the back electrode 84, the male screw 11 is again used.
It suffices to insert 0 into the circular hole 114 and screw it with the nut 116 so that it can be easily attached and detached, and the processing at the time of abnormality such as when the master 12 is jammed can be performed quickly.

In this embodiment, the back electrode 84 is applied only to the portion facing the developing electrode 82. However, as shown in FIG. 9, the guide plate 118 and the back electrode 84 are integrally formed of a foam metal plate. In this case, all the surfaces that come into contact with the master 12 are foamed metal plates, and the dirt on the back surface of the master 12 can be reduced. In this case, the back plate 90 can be replaced with the support plate 112.

[0061]

As described above, the wet electrophotographic apparatus according to the present invention can make the concentration of toner on the photosensitive surface of the photosensitive material uniform, and reduce the amount of toner particles attached to the back electrode. In addition, the excellent effect that the movement of the photosensitive material can be made smooth is obtained.

In addition to the above effects, the back electrode can be easily attached and detached, and the maintainability can be improved. Further, in addition to the above effects, it is possible to reliably prevent the back surface of the photosensitive material from being soiled.

[Brief description of the drawings]

FIG. 1 is a side view showing a developing unit of a wet electrophotographic apparatus according to the present invention.

FIG. 2 is an exploded perspective view of a developing unit.

FIG. 3 is a schematic view showing the overall structure of a wet electrophotographic apparatus to which the present invention is applied.

FIG. 4 is a cross-sectional view showing a master.

FIG. 5 is a cross-sectional view showing a metal foam plate.

FIG. 6 is a characteristic diagram comparing the state of change in reflection density according to the processing of one master with the conventional example and the present example.

FIG. 7 is a characteristic diagram of the number of processed masters versus reflection density.

FIG. 8 is a charge amount characteristic diagram that contributes to the development per unit area of the number of processed masters.

FIG. 9 is a perspective view of the vicinity of the back plate when the back electrode and the guide plate are integrally formed of a metal foam plate.

10 is a schematic view showing a part of the metal foam plate shown in FIG. 5 in an enlarged manner.

FIG. 11 is a partially enlarged schematic view of a conventional roughened electrode.

FIG. 12 is a partially enlarged schematic view of a conventional planar mesh electrode.

[Explanation of symbols]

 10 Wet Electrophotographic Device 12 Photoreceptor (Master) 20 Developing Section 32 Liquid Toner 82 Developing Electrode 84 Back Electrode (Foam Metal Plate) 110 Male Screw 112 Support Plate 116 Nut 118 Guide Plate

Claims (3)

(57) [Claims] 1. A developing electrode facing the first surface of the photosensitive material on which an electrostatic latent image is formed, in a non-contact state, and a side opposite to the first surface of the photosensitive material, the developing electrode being opposed to the developing electrode. Back electrode that is in contact with the second surface of the conductive material and is made of a conductive material having a three-dimensional mesh structure, and the surface formed by connecting the portions of the conductive material in contact with the second surface is a flat surface And a wet electrophotographic apparatus including: 2. A plate-shaped developing electrode facing a photosensitive surface of a photosensitive material on which an electrostatic latent image is formed by image exposure, and a conductive material having a three-dimensional mesh structure, which is opposite to the photosensitive surface. Plate-shaped back electrode facing the side surface, a conveying means for conveying the photosensitive material between the developing electrode and the rear electrode, and liquid toner is supplied between the developing electrode and the photosensitive material to generate an electrostatic latent image. Toner supplying means for making an image visible, a frame body for supporting the back electrode, and a guide provided at an end portion of the frame body on the insertion side of the photosensitive material to guide the photosensitive material between the developing electrode and the back electrode. A wet electrophotographic apparatus comprising a plate and a detaching means for detaching the back electrode from the frame. 3. The wet electrophotographic apparatus according to claim 2, wherein the guide plate is integrated with the back electrode.