JPH0365554B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a wet type developing device that develops an electrostatic latent image using a liquid developer. In conventional wet developing devices, in order to visualize the photoconductor on which the electrostatic latent image has been formed, a developing solution is applied between two electrically conductive sheets (hereinafter referred to as electrodes) that are electrically at the same potential or a bias potential. Various methods have been proposed in which the photoreceptor is supplied and simultaneously passed through a photoreceptor for development. FIG. 1 is a conceptual diagram of a developing mechanism of a wet type developing device. According to this, the electric field strength Eu between the surfaces of the main electrode 1 and the photoreceptor 2 is expressed as Eu=Vo/εu(dq/εp+dl/εl)+du. Here, Vo is the surface potential, dp is the thickness of the photoreceptor 2, εp is the relative permittivity of the photoreceptor, εu is the relative permittivity between the photoreceptor 2 and the main electrode 1, and εl is the difference between the photoreceptor 2 and the auxiliary electrode 3. The relative permittivity, du is the photoreceptor 2 and main electrode 1
and dl is the distance between the photoreceptor 2 and the auxiliary electrode 3. Figure 2 shows the relationship between each variable and the electric field strength Eu.
As a representative value of each variable, surface potential Vo=
600volt, photoconductor thickness dp = 0.001cm, photoconductor dielectric constant εp = 2, dielectric constant εu between photoconductor 2 and main electrode 1
=8 is adopted. According to this, when the space between the photoreceptor 2 and the auxiliary electrode 3 is filled with the developer, that is, εl=8, the electric field strength Eu is larger than when it is filled with air (εl=1). Therefore, in order to cause more toner particles T in the developer to adhere (to ensure sufficient development), it is necessary to sufficiently fill the space between the photoreceptor 2 and the auxiliary electrode 3 with the developer. However, when the space between the photoreceptor 2 and the auxiliary electrode 3 is filled with developer, an electric field strength El is generated, and the charged toner particles T also adhere to the surface of the auxiliary electrode 3. When the toner particles T touch the auxiliary electrode 3, there is a problem in that the adhered toner particles T cause stains. To solve these problems, Japanese Patent Application Laid-Open No. 49-62148 proposes a method in which a developer is forcibly sprayed above and below the photoreceptor 2, and the flow force pushes the photoreceptor 2 away from the main electrode 1 and the auxiliary electrode 3. This improves the permeability and prevents toner particles from adhering to the back surface of the photoreceptor. FIG. 3 is a conceptual diagram of the system, in which 4 and 5 are developer supply devices, 6 and 7 are photoreceptor feed rollers, 8 and 9 are squeeze rollers, and the developer supply devices 4 and 5 are connected to a pump (not shown). ) is used to send a developer and develop the photoreceptor 2. Hereinafter, this method will be referred to as the double jet method. On the other hand, FIG. 4 shows a developing device in which the developer is supplied from the developer supplying device 4 only from above the photoreceptor 2.
A thread-like guide 10 made of nylon or the like is provided on the surface of the auxiliary electrode 3 on the photoreceptor 2 side to reduce the contact area with the photoreceptor 2, to improve the passage of the photoreceptor 2 and to guide the photoreceptor 2 to the back side. This prevents the adhesion of toner particles. The following method is called the single jet method. The double-jet method produces excellent developed images, but it requires two developer supply devices, making the mechanism complicated, and the need to balance the amount of developer supply, resulting in troublesome maintenance. . On the other hand, the single-jet method has a simple mechanism and is easy to maintain, and the cost of the device is also low; however, it has the disadvantage that the uniformity of a large area (hereinafter referred to as fill-in) is poor. Fill-in means whether or not toner particles uniformly adhere to a latent image when the image area is completely black, for example, in a 10 cm x 10 cm area. In the double jet method, the toner particles adhere uniformly and sufficiently, but in the single jet method, the toner particles adhere to the center of the image somewhat less and unevenly. As can be seen from the principle described above, the double jet method does not allow air to enter the back surface of the photoreceptor and a sufficiently strong electric field strength is obtained between the photoreceptor and the main electrode, but the single jet method uses a thread-like guide. It is thought that air enters the created space, which causes the electric field strength to be weak and the amount of toner particles to adhere to be non-uniform. As a result of intensive research aimed at realizing a single-jet type developing device with good fill-in, the present inventor has found that one or more auxiliary electrodes are provided on the surface of the photoreceptor side of the auxiliary electrode at right angles to or at an angle close to the direction of passage of the photoreceptor. To produce a developing device, the developing device is characterized by having individual gutter-like recesses or weir-like protrusions, and an insulating thread-like guide provided above the guide at an angle parallel to or close to the direction in which the photoreceptor passes. I've reached it. The present invention will be explained in detail below based on the drawings. FIG. 5 is a sectional view of the wet developing device of the present invention, and FIG.
The figure shows a perspective view of the auxiliary electrode 3. Figures 5 and 6
The developing device of the present invention shown in the figure includes a photoreceptor 2, a pair of photoreceptor feed rollers 6 and 7 for feeding the photoreceptor 2 into the developing device, and an auxiliary electrode with an inclination for improving image quality and forming a liquid path. 4. Photoreceptor 2 of auxiliary electrode 4
A plurality of insulating thread-like guides 10 made of nylon or the like are provided on the surface side to facilitate the passage of the photoreceptor; a main electrode 1 facing the auxiliary electrode 3 for improving image quality and forming a liquid path; A tank 12 that stores a developer, a pump 13 that sends the developer in the tank 12 to the developer supply device 4, a liquid supply pipe 14 that sends the developer sent out by the pump 13, and a liquid supply pipe 14 that allows the developer from the liquid supply pipe 14 to be exposed to light. A developer supply device 4 that forcibly sprays onto the surface of the body 2 and supplies between the main electrode 1 and the auxiliary electrode 3 to form a liquid path; a pair of squeezing rollers 8 that serve both to feed the photoreceptor 2 and to squeeze the developer;
9. Consists of a weir-like convex portion 11 made of a good electrical conductor and provided between the thread-like guide 10 and the auxiliary electrode 3. Next, the operation and effect of the present invention will be explained. In FIGS. 5 and 6, the photoreceptor 2 having an electrostatic latent image is transmitted in the direction of arrow A by feed rollers 6 and 7, and is connected to a thread-like guide 10 and an auxiliary electrode 3 having a weir-like convex portion 11. The signal is transmitted between the main electrodes 1 provided opposite to the main electrodes 3 and 3. At this time tank 12
The developer inside is sent to the developer supply device 4 by a pump 13 via a pipe 14 (this process is not shown) and is forcibly injected between the auxiliary electrode 3 and the main electrode 1. Therefore, when the photosensitive paper 2 is sent between the auxiliary electrode 3 and the main electrode 1, the developer is forcibly sprayed onto the surface of the photoreceptor 2 having the electrostatic latent image, and at the same time, the developer is forcedly sprayed between the auxiliary electrode 3 and the main electrode 1. The electrostatic latent image is made into a visible image using a developer with a liquid path formed in the area. The developer that has passed through a liquid path formed between the auxiliary electrode 3 and the main electrode 1 returns to the tank 12 and is circulated. Further, the developed photoreceptor 2 is transferred to aperture rollers 8 and 9.
is sent out of the developing device. The photoreceptor 2 having an electrostatic latent image is forced onto a plurality of thread-like guides 10 made of nylon or the like provided on the auxiliary electrode 3 by a developer forcibly sprayed from a developer supply device 4 and assisted. Since the light passes between the electrode 3 and the main electrode 1, the main electrode 1, the photoreceptor 2, the photoreceptor 2, and the auxiliary electrode 3 are transmitted while always maintaining a constant gap. In the above embodiment, the auxiliary electrode 3 has four weir-like convex parts.
However, it is the same as the one in which relatively gutter-shaped recesses are provided at three locations on the auxiliary electrode 3. Since it has the above configuration, from the upper part of the photoreceptor 2,
Most of the developer forcibly injected from the developer supply device 4 flows over the photoconductor 2, but since the width of the developer discharge port 15 of the developer supply device 4 is made larger than the width of the photoconductor 2, The developer a flowing outside the width of the photoreceptor 2 and the developer b sprayed near the end of the photoreceptor and flowing out to the outside of the photoreceptor 2 are connected to the weir-like convex portion 1.
1 and flows along the convex part to the center.
Then, the gap between the back surface of the photoreceptor 2 and the upper part of the weir-like convex portion 11 created by the thread-like guide 10 is filled with the developer, and the filled liquid comes into contact with the back surface of the photoreceptor 2 .
As a result, no air enters the back surface of the photoreceptor 2,
A sufficiently strong electric field strength can be obtained between the photoreceptor 2 and the main electrode 1, and an image with good fill-in can be obtained. According to experiments, the height x of the weir-like convex portion 11 (or the depth of the concave portion) is effective when it is 0.2 mm or more, and the best effect is obtained when it is about 1.0 mm. If it is less than 0.2 mm, the developer will not penetrate well and sufficient effects will not be obtained. It is effective to set the width y of the weir-like convex part 11 to about 1 mm, but if the weir-like convex part 11 is made of a good electrical conductor such as metal, the upper surface of the convex part acts as an auxiliary electrode close to the photoreceptor 2 and has a large area. It is best to provide a width of 10 to 50 mm as it is more effective. Contrary to the convex portion, the width of the concave portion (the interval between the weir-like convex portions 11) must be set to improve the flow of the liquid to the back surface of the photoreceptor 2, and is preferably 5 mm or more, and is preferably provided with a width of 15 to 50 mm. Good. As for the material of the weir-like convex portion 11, a good electrical conductor such as metal is most effective, but an insulating material such as plastic can also have a considerable effect. The weir-like convex portion 11 may be formed of a rod-like or thread-like material, and is made of nylon thread or the like with a diameter of 0.2 mm to 1.5 mm, and is formed at an angle of 3 to 5 perpendicular to or approximately close to the passing direction of the photoreceptor 2.
It is effective enough even if it is stretched out. Weir-like convex part 1
1 can be provided on the auxiliary electrode 3 by pasting a good electrical conductor such as metal or an insulating material such as plastic by known means such as screwing, welding, etc., but the surface of the auxiliary electrode 3 itself made of a good electrical conductor such as metal The grooves may be formed by cutting with a milling machine etc.
The unevenness may be formed by pressing. The thread-like guide 10 can be made of a material with good insulation properties such as nylon or Tetron, and its thickness is 50 μ to 1
Approximately mm is preferable. If the thickness is less than 50μ, there is a problem in terms of durability, and if the thickness is more than 1.5mm, the space above the photoreceptor 2 and the weir-like convex portion 11 cannot be filled with the developer, making it impossible to obtain a good image. Both ends of the thread-like guide 10 may be screwed to the auxiliary electrode 3 or may be attached with an adhesive or the like, and the thread-like guide 10 may be attached to the auxiliary electrode 3 in the same direction as the photoreceptor 2 or at a certain angle.
It is sufficient if it is provided so as to allow smooth passage. FIG. 7 shows another embodiment in which a gutter-like recess 16 is provided in the auxiliary electrode 3, and the developer flowing outside the width of the photoconductor 2 is sprayed near both ends of the photoconductor 2. The developer flowing out of the groove 2 flows into the gutter-like recess 16. The developer that has flowed into the gutter-like recess 16 gradually overflows, filling the gap between the back surface of the photoreceptor 2 and the auxiliary electrode 3 created by the thread-like guide 10 with the developer, and the filled liquid flows onto the back surface of the photoreceptor 2. come into contact with As a result, air does not enter the back surface of the photoreceptor 2, and a sufficiently strong electric field strength is obtained between the photoreceptor 2 and the main electrode 1, resulting in an image with good fill-in. It should be noted that the weir-like convex portion 11 and the gutter-like concave portion 16 are not limited to the shapes and numbers described in the embodiments, and may be a combination thereof. One or more can be provided. FIG. 8 shows a structure in which a plurality of weir-like convex portions 11 are alternately provided in an oblique manner. By providing the weir-like convex portions 11 in an oblique manner in this manner, the developer does not stay in the concave portions, and
It has the advantage that development can be performed well. As an actual performance comparison example, Table 2 shows the amount of adhered toner particles at the center of a large area solid (all black) expressed in terms of reflection density. The developer is an ELP toner type manufactured by Fuji Photo Film Co., Ltd., and the photosensitive couple is manufactured by the same company.
ELP Master, electrophotographic engraving machine is the company's ELP280
The experiment was conducted by replacing only the developing device.

[Table] 〓The higher the density, the better the image quality〓
Next, we conducted an experiment in which the filament guide 10 of this device was removed.
It has been found that both of the methods shown in the figure cause poor passage of the photoreceptor 2 and dirt on the back of the photoreceptor, and are not practical because they do not generate enough force to push the photoreceptor 2 away from the auxiliary electrode 3. As explained above, the present invention solves the problems of conventional wet developing devices, and provides an inexpensive device that has a simple structure and is easy to maintain, and its effects are extremely large.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the developing mechanism, Figure 2 is a diagram of the relationship between electric field strength and dielectric constant, Figure 3 is a conceptual diagram of the double jet system, Figure 4 is a conceptual diagram of the single jet system, and Figure 5 is the main diagram. FIGS. 6 to 8 are a cross-sectional view of the wet developing device of the invention, and perspective views of the electrode portion of the invention. DESCRIPTION OF SYMBOLS 1... Main electrode, 2... Photoreceptor, 3... Auxiliary electrode, 4, 5... Developer supply device, 6, 7... Feed roller, 8, 9... Squeezing roller, 10... Thread-shaped guide, 11... Weir-like convex portion, 12... Tank, 13
... pump, 14 ... liquid supply pipe, 15 ... discharge port, 16 ... gutter-shaped recess.

Claims (1)

[Scope of Claims] 1. In a wet electrophotographic developing device that develops an electrostatic latent image by simultaneously passing a liquid developer and a photoreceptor having an electrostatic latent image between two electrodes, At least one weir-like convex part or gutter-like concave part is provided on the surface of the electrode on the side that does not have an electrolatent image at a right angle to or at an angle close to the direction of passage of the photoreceptor, and the weir-like convex part Alternatively, a wet electrophotographic developing device characterized in that an insulating guide is provided above the concave portion of the gutter image at an angle parallel to or close to the path of the photoreceptor.