JPH0527764U - Electrode for wet electrophotographic developing device - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an electrode suitable for a wet electrophotographic developing device, which has no movable part and prevents image deterioration due to toner adhesion to the developing electrode. A porous metal body and a supporting member, which are provided so as to face an electrophotographic photosensitive material on which an electrostatic latent image is formed and which is conveyed on a back guide, face a photosensitive layer of the electrophotographic photosensitive material. In addition to being configured, the distal end portion of the porous metal body is closed by the protruding portion of the support member.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention develops an electrophotographic photosensitive material on which an electrostatic latent image is formed with a developing solution (toner solution), and prevents the image deterioration due to the adhesion of toner to a developing electrode. Optimal electrode for.

[0002]

[Prior Art]

 FIG. 9 shows the structure of a conventional general wet electrophotographic developing device, in which a back guide 100 made of an insulating material is provided at a predetermined angle, and a predetermined development is performed so as to face the back guide 100. The developing electrode 101 is provided with a gap. The developing electrode 101 is biased to 150 [V] to 200 [V] by the bias power source 102, and the electrophotographic photosensitive material 120 on which the electrostatic latent image is formed in the exposed portion (not shown) is together with the developing solution 110. An image is formed by being conveyed in the developing gap on the back guide 100. The electrophotographic photosensitive material 120 is composed of a support layer 121 made of a conductive material such as aluminum and a photosensitive layer 122 made of OPC (Organic Photoconductor) in a plate shape. It is grounded and developed.

In the reversal development method, toner adheres to a non-charged portion (image portion) of the photosensitive layer 122, and the photosensitive layer 122 in a portion (non-image portion) charged with a positive charge is chemically etched to form an image. It is formed. In reversal development, in order to prevent fog, the developing bias voltage value must be set lower than the surface potential of the non-image area of the photosensitive material. Therefore, the development bias voltage is selected between the surface potential of the non-image area and the surface potential of the image area (actually, a small potential is left instead of zero, which is called the residual potential), and the development bias voltage and the non-image area are selected. Or, there is usually a sufficient potential difference between both potentials in the image area. Therefore, when the non-image portion of the photosensitive material 120 is positioned below the developing electrode 101 for a long time in the developing portion, the surface potential of the photosensitive layer 122 becomes higher than the bias voltage, so that the opposite surface of the developing electrode 101 on the developing electrode 101. As shown in FIG. 10, the toner 111 adheres and accumulates. After the plate passes through the developing electrode 101, the adhered toner 111 gradually disappears due to the electrical repulsion of the developing electrode 101 and the toner 111 and the liquid flow of the developing solution 110. When 120 is conveyed to the developing unit, the bias voltage apparently becomes higher than the bias voltage of the bias power source 102 due to the charge of the toner 111, and the image is crushed.

[0006] Such a phenomenon appears remarkably in the case of developing a long plate such as a newspaper vertical two-page plate (about 1100 mm), which is a serious problem. Furthermore, the time required for toner disappearance becomes smaller as the plate-making repeating cycle (multi-plate) is speeded up, so it is important to keep the bias voltage stable.

In order to prevent such an inconvenience, it is necessary to prevent (reduce) the adhesion of the toner to the developing electrode or to quickly remove the adhered toner. For this purpose, conventionally, a winding type developing device as shown in FIG. 11 (Japanese Patent Laid-Open No. 60-57875) or a movable type developing device as shown in FIG. 12 (Japanese Patent Laid-Open No. 61-20967). ) Is used. That is, in the take-up type developing device of FIG. 11, the electrophotographic photosensitive material 201 is conveyed along the back surface guide 200, and at the same time, the belt 205 is developed from the roller 205 to the take-up roller 206 via the rollers 202 and 203. The electrode 204 is adapted to be wound up. Since the winding of the strip-shaped developing electrode 204 is performed in synchronization with the conveyance of the electrophotographic photosensitive material 201, the development is always performed by the new strip-shaped developing electrode 204. Further, in the movable developing device of FIG. 12, the electrode member 212 is in the form of an endless belt and is wound around the driving roller 210 and the free roller 211, and is moved in synchronization with the conveyance of the electrophotographic photosensitive material 201. It is like this. Further, the toner adhering to the surface of the electrode member 212 in the developing gap is scraped off by the doctor blade 213 provided so as to be in contact with the electrode member 212 of the driving roller 210, and the cleaned electrode member 212 is always cleaned. It will be developed.

[0006]

[Problems to be solved by the device]

 The conventional winding-type and moving-type developing devices described above are both focused on removing the adhered toner, and the developing electrodes are movable, so the mechanism is complicated and maintenance is easy. There is a drawback that performance is reduced. Further, since it is movable, it is very difficult to maintain the flatness of the developing electrode, and it is difficult to realize a narrow developing gap.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to effectively prevent image deterioration by reducing toner adhesion to a developing electrode without having a movable part. It is an object of the present invention to provide an optimum electrode for a wet electrophotographic developing device.

[0008]

[Means for Solving the Problems]

 The present invention relates to an electrode for a wet electrophotographic developing device, and the above-mentioned object of the present invention is to provide an electrostatic latent image-carrying electrophotographic photosensitive material, which is conveyed on a back guide, to face the electrophotographic photosensitive material. It is composed of a porous metal body facing the photosensitive layer of the photographic light-sensitive material and a support member, and the tip of the porous metal body is closed by a projecting member from the support member. Is achieved by

[0009]

[Action]

 In the electrode of the present invention, the surface of the developing electrode is roughened to increase the surface area, and the distance between the toner adhering to the electrode and the electrode during development is reduced to prevent an unnecessary increase in the bias voltage. We try to eliminate inconveniences such as crushing. Since the projection is provided at the tip of the electrode, development can be carried out with a small liquid feeding amount.

As a means for roughening the surface of the developing electrode, irregularities such as grooves and holes may be provided on the electrode surface, and it is particularly preferable to use a porous metal body such as Celmet (trade name). As a material of the porous metal body, a conductor such as Al, Cu, Ni, Ag or the like is preferable, and a metal having a higher conductivity has a better effect. FIG. 5 shows the difference in surface roughness of the developing electrode and the state of toner adhesion. FIG. 5A shows the surface of the developing electrode 1 having a flat surface roughness (hereinafter referred to as “specific surface area”) 1. It is shown that Toner 2 adheres in a consistent manner. The distance between the toner and the electrode is the largest compared to the roughened electrode, and the electrode surface area that attracts the toner charge is the smallest. Therefore, the bias voltage rises apparently. This is the relationship between the conventional general developing electrode and toner adhesion. FIG. 5 (B) shows that the toner 2 adheres to the surface of the developing electrode 3 having a grooved specific surface area of about 70 to 100. Is deteriorated, the distance between the toner 2 and the developing electrode 3 is reduced, and the electrode surface area is increased, so that a synergistic effect can be obtained. Further, FIG. 5C shows the case where the porous metal body 4 having a specific surface area of about 2500 to 3000 is used as the developing electrode, and the consistency of the adhesion of the toner 2 is completely lost, and the distance between the toner 2 and the developing electrode 4 is limited. The increase in the bias voltage can be suppressed to an extremely small level in accordance with the size of the surface area. By improving the conditions for such toner adhesion, the development bias does not rise abnormally due to toner adhesion.

[0011]

【Example】

 FIG. 1 shows an embodiment of the present invention in which an electrophotographic photosensitive material 20 on which an electrostatic latent image is formed is conveyed at a predetermined speed on a back guide 10 which is inclined at a predetermined angle (for example, 7 °). The support layer of the electrophotographic photosensitive material 20 is grounded via the ground terminals 21 and 22. The back guide 10 has minute protrusions for the purpose of reducing the contact resistance with the back surface of the photosensitive material for improving the transportability and for suppressing the volume of the developing chamber so as not to unnecessarily increase the liquid transfer amount. It is composed of a glass plate. A developing electrode 30 of the present invention having the structure shown in FIG. 2 is arranged above the rear guide 10 with a predetermined developing gap, and a pair of aperture rollers 11 are provided at the outlet of the rear guide 10. And 12 are provided. The developed electrophotographic photosensitive material 20 is squeezed between the squeezing rollers 11 and 12, and then conveyed to a fixing unit (not shown) in the next stage. Further, a cleaning pad 13 for cleaning is attached to the squeezing roller 11 so that the squeezing rollers 11 and 12 are automatically cleaned.

The developing electrode 30 has two separated electrode supporting plates 31 and 32, and the electrode supporting plates 31 and 32 are connected by connecting plates 33 and 34 at their ends. Further, Celmet (trade name: manufactured by Sumitomo Electric Works, Ltd.) layers 35 and 36 as porous metal bodies are provided on the lower surfaces of the electrode support plates 31 and 32. The celmet layers 35 and 36 are electrically connected via a lead wire 37, and a bias voltage is applied to the celmet layers 35 and 36 by a bias power source 38.

On the other hand, a developing solution supply unit 40 is installed on the support plate 31 from which the developing electrode 30 is separated, and the developing solution supplied from the supply pipes 41 and 42 and stored therein is of a porous or slit type. The developing solution 44 is supplied to the developing gap from a cylindrical ejection portion 43 having an ejection port. The developing solution is pumped up from a developing solution tank (not shown) and stored in the developing solution supply section 40 through the supply pipes 41 and 42, and is supplied to the developing gap from the discharge section 43 of the developing solution supply section 40, thereby developing electrode. The developer overflowing from 30 is collected by the bath and returned to the developer tank. Such circulation of the developing solution is performed continuously or intermittently during the development and before and after the development. Further, the downward inclination of the back guide 10 and the developing electrode 30 is such that the developing solution 44 is not supplied to the upstream side along the electrophotographic photosensitive material 20 so that the developing solution is supplied in a small amount and the developing gap is filled with the developing solution 44. Is set, and the inclination (7 ° in this example) is set so that air bubbles do not mix, and excess developer overflows outside the development gap to promote toner evaporation and toner performance change does not occur. To be done.

FIG. 3 shows a cross-sectional structure of the developing section, in which the front end of the celmet layer 36 is closed by a projection 32 A projecting downward at the front end of the support plate 32. Since the celmet layer 36 is a porous body, it absorbs the developer 44 to the full extent, and without the protrusion 32A, the developer is filled several times to fill the gap with the developer as compared with the case where the protrusion 32A is present. The required amount of liquid is required. If the tip portion of the celmet layer 36 has the protrusion 32A, the developer absorbed by the celmet layer 36 does not flow in the inclined direction and is blocked, so that the gap can be filled with a small amount of liquid. it can. That is, if the protrusion 32A is provided as shown in FIG. 3, the gap length L1 can be filled with a small amount of liquid to be fed, but if the protrusion 32A is not provided as shown in FIG. L2) also flows out and fills the inside thereof, so that several times as much liquid transfer amount as the gap length L3 (= L1 + L2) is required. When the amount of liquid to be delivered increases, it is necessary to improve the capacity of the liquid delivery pump, and there is a drawback that the liquid delivery device becomes large in size in response to a large circulation amount.

The number of cells of Celmet is preferably as large as possible within the range in which air replaces the toner. In this embodiment, product number # 4 (26 to 35 cells / inch) is used. When the thickness of the celmet layer 36 is small, the effect is reduced and the strength is weak. Further, if the thickness of the celmet layer 36 is too large, air will not be formed and a good image will not be formed. Therefore, the thickness is preferably in the range of 1 to 5 mm, and good conditions may be selected according to the toner prescription. In this embodiment, the thickness is L2 = 2 mm.

Since the surface of the developing electrode 30 of the present invention is the porous body of the Celmet layers 35 and 36, the specific surface area of the rough surface is considerably higher than that of the flat electrode 1 as shown in FIG. The toner adheres in the state as shown in FIG. By the way, when a portion of the photosensitive material having a high surface potential (unexposed portion) is under the developing electrode, the toner adheres to the developing electrode due to the electric field of the difference between the developing bias voltage and the surface potential. This rise in the charge amount of the adhered toner appears as fluctuations in the development bias voltage, and development at a bias voltage value higher than in the normal state is performed behind the unexposed area, and halftone dot shadow areas, white characters, etc. are crushed. Reproducibility decreases. However, by using a porous metal body as the developing electrode as in the present invention, the specific surface area of the electrode can be increased, the distance between the toner adhering to the electrode and the electrode can be shortened, and an apparent bias voltage rise can be prevented. For this reason, the phenomenon that the developing bias voltage fluctuates depending on the image pattern is reduced, and in particular, a remarkable effect can be obtained in the processing of a long plate such as a newspaper vertical two-page plate and the speedup of the multi-plate cycle. .. FIG. 6 shows the relationship between the specific surface area (1, 70, 2500) of the developing electrode and the halftone dot area ratio (%) of the halftone dot reproduction area. The electrode having the specific surface area 2500 is Celmet part number # 4.

7 and 8 show another embodiment of the present invention, which shows a developing electrode 50 having an integrated structure. A developing solution supply section 51 is provided at the center of the electrode, and the developing solution is supplied to the developing gap from the ejection port 51A at the bottom. The upper surface side of the developing electrode 50 is composed of a supporting plate 52, and the lower surface side thereof is provided with a celmet layer 54, and the supporting plate 52 at the tip end thereof has a protruding portion 52A having a bent structure. It is formed so as to hold a predetermined developing gap length L4. Since the developing solution is supplied to the developing gap through the celmet layer 54, a bubble escape hole 55 is provided on the upstream side. With such a developing electrode 50, the electrophotographic photosensitive material 61 conveyed on the back guide 60 is developed.

Since the developing electrode 50 has an integrated structure, the maintainability is improved, and since the celmet layer 54 is not separated, it is easy to maintain the developing gap length at the predetermined length L4.

[0019]

[Effect of the device]

 According to the developing electrode of the present invention, the specific surface area due to the rough surface of the electrode is increased by using a porous metal body or the like to shorten the distance between the toner adhering to the electrode and the electrode, and the synergistic effect of expanding the electrode surface area. As a result, the apparent bias voltage rise due to the charge of the adhered toner can be reduced. Therefore, the phenomenon in which the development bias voltage fluctuates depending on the image pattern is reduced, and the problem such as image crushing can be eliminated. Further, since the protrusion is provided at the tip of the electrode to limit the outflow of the developing solution, it is possible to carry out the development with a small solution sending amount.

[Brief description of drawings]

FIG. 1 is a structural diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a perspective structure of a developing electrode of FIG.

FIG. 3 is a cross-sectional view showing a cross-sectional structure of the developing electrode of FIG.

FIG. 4 is a diagram for explaining the operation of the developing electrode.

FIG. 5 is a diagram showing the roughness of the developing electrode surface and the state of toner adhesion.

FIG. 6 is a diagram for explaining the effect of the present invention.

FIG. 7 is a cross-sectional view showing another embodiment of the present invention.

8 is a perspective view showing a perspective structure of the developing electrode of FIG. 7. FIG.

FIG. 9 is a diagram for explaining the structure of a general wet electrophotographic developing device.

FIG. 10 is a diagram for explaining the state of development in FIG.

FIG. 11 is a diagram showing an example of a conventional device.

FIG. 12 is a diagram showing another example of a conventional device.

[Explanation of symbols]

 1, 3 and 4 developing electrode 2 toner 10 back guide 11 and 12 aperture roller 20 electrophotographic photosensitive material 21 and 22 grounding terminal 30 developing electrode 31 and 32 supporting plate 35 and 36 celmet layer 40 developing solution supplying section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Akihiro Kanazawa 1005 Koen, Ayase City, Kanagawa Prefecture Fuji Micrographix Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A backside guide is provided so as to face an electrophotographic photosensitive material on which an electrostatic latent image is formed,
The structure is composed of a porous metal body facing the photosensitive layer of the electrophotographic photosensitive material and a supporting member, and the tip of the porous metal body is closed by a projecting member from the supporting member. An electrode for a wet electrophotographic developing device, which is characterized in that