JP3535400B2 - 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 an electrophotographic apparatus using a liquid developer.

[0002]

2. Description of the Related Art A wet electrophotographic apparatus using a liquid developer has an advantage that cannot be realized by a dry electrophotographic apparatus, and therefore its value is being reviewed in recent years. The advantage of the wet type electrophotographic device over the dry type electrophotographic device is that it is possible to use a very fine toner of submicron size to realize high image quality, and it is economical because a small amount of toner can obtain a sufficient image density. In addition, it is possible to realize a texture equivalent to that of printing (for example, offset printing), and to realize energy saving because the toner can be fixed on the paper at a relatively low temperature.

On the other hand, the conventional wet electrophotographic technique using a liquid toner has some problems. One of the problems is that a liquid developer using a high resistance or insulating petroleum solvent as a carrier solvent must be used to develop an electrostatic latent image.

That is, since the liquid developer is used, it is necessary to bring the developer into close contact with the surface of the photosensitive layer in the developing section, and a mechanism for positively supplying the developer by using a pump or the like is necessary for that. At this time, if the supply speed of the developer is too slow, the amount of toner carried to the image forming portion of the photosensitive layer will be insufficient, resulting in color loss and insufficient contrast.If the supply speed is too fast, excess toner will be supplied. As a result, there arises a problem that the image density becomes too high. In addition, if the supply rate is uneven, it causes unevenness in the density of the image, which causes a great discrepancy in the formation of a high-quality image, which is the greatest advantage of the wet electrophotographic system.

8 and 9 show examples of the construction of a conventional developing device of a wet electrophotographic apparatus. As shown in FIGS. 8 and 9, most of the conventional developing mechanisms of the wet electrophotographic apparatus have a structure in which the developing roller 30 is rotated, liquid developer is attached to the surface thereof, and the liquid developer is conveyed to the developing portion of the photosensitive drum 31. Has been taken. That is, the lower part of the developing roller 30 is immersed in the liquid developer reservoir housed in the container, and when the developing roller 30 rotates, the liquid developer adheres to the surface of the developing roller 30 and is conveyed accordingly. Then, the liquid developer is carried to a very small gap between the developing roller 30 and the photosensitive drum 31,
Develop.

In the developing device having such a structure, the liquid developer carrying speed is determined by the affinity between the surface of the developing roller 30 and the liquid developer, the rotation speed of the developing roller 30, the developing roller 30 and the liquid developer pool. Contact width of the developing roller 3
It is determined by the height of the liquid developer surface with respect to zero. Therefore, a control mechanism that keeps the liquid level height at a predetermined position is required.

In the developing device shown in FIG. 8, the liquid developer is
The liquid developer is supplied to the liquid developer reservoir from the bottom of the liquid developer reservoir by a circulation pump or the like, and in the developing device shown in FIG. 9, the liquid developer flows down from a nozzle above the liquid surface of the liquid developer, and Although the liquid is supplied to the developer reservoir, if the liquid surface is wavy during development due to the pulsation of the pump or the impact when it flows down, the contact width between the developing roller 30 and the liquid developer changes, and Affects the concentration.

There are other drawbacks to the method of immersing the developing roller 30 in the liquid developer pool. For example, if a roller having an extremely small diameter is used as the developing roller 30, the influence of the liquid level height error on the surface adhesion amount of the developing roller 30 becomes extremely large, and it becomes difficult to stabilize the above-described adhesion amount control. The stable supply of the developer becomes extremely difficult. Another problem is that a relatively large amount of liquid developer must always be contained in the container.

The liquid developer is, as described above, a toner dispersed in a petroleum solvent. This solvent evaporates relatively easily, and if it leaks out of the machine, it causes odor and allergic effects on the human body. For this reason, in the wet development mechanism, the liquid developer is supplied onto the photosensitive drum only during development so as to minimize the exposure time of the liquid developer to the air, and when it is not needed, it is collected in the tank. It is also necessary to store and devise to minimize the generation of solvent vapor.

However, in the above-mentioned developing mechanism, it is necessary to stock a relatively large amount of liquid developer at the time of development, and this is kept exposed to the air during the developing operation, so the solvent is relatively large. Evaporates easily. In particular, when the diameter of the developing roller 30 is increased, the opening area of the liquid developer becomes extremely large and the solvent evaporation is more likely to occur.

Therefore, a liquid developer supply device (US Pat. No. 5585900) of another system, which is not a system of immersing the roller in the liquid developer pool, will be described. In this type of liquid developer supply device, there is one developing roller for four colors of liquid developer, and transfer is performed for each color. The liquid developer is supplied to the developing roller directly on the surface of the developing roller by jetting from a plurality of nozzles arranged in the width direction of the developing roller. The jetted liquid developer is, after the surface of the developing roller is smoothed by a blade or a roller, carried to the photosensitive drum and developed.

In this system, it is easy to control the amount of the liquid developer carried in one development, and uneven development density is less likely to occur due to the uneven amount of the liquid developer. Further, since the liquid developer is ejected in a required amount during the developing operation, there is an advantage that the generation of solvent vapor from the liquid pool is small unlike the conventional example shown in FIGS.

However, in this structure, a liquid developer supply mechanism for uniformly ejecting in the width direction of the developing roller is required, and the piping for that requires an extremely large volume. In particular, since it serves as a mechanism for supplying the liquid developer from the front direction of the developing roller, in a structure in which a plurality of developing mechanisms are arranged in parallel, the developing mechanisms must be separated from each other. Also, when trying to make the piping itself smaller, the diameter of the pipe becomes smaller and it easily clogs, resulting in
It is impossible to realize a small device with this mechanism.

FIG. 10 shows a conventional example of still another structure. In the example shown in FIG. 10, the elastic blade 33 is pressed uniformly on the developing roller 30 in the width direction, or is arranged in a state of being in close proximity. This blade and developing roller 30
The liquid developer is continuously supplied from the side surface or the front surface of the cylindrical shaft of the developing roller 30 into the pseudo-triangular gap formed by (1) to form a temporary liquid pool. The amount of liquid developer in the liquid pool is balanced when the amount leaked from each gap and the amount supplied are balanced. When the developing roller 30 rotates, the liquid developer is scooped from the liquid pool and supplied to the photosensitive drum surface. . The liquid developer is supplied to the gap formed by the blade 33 at the same time as the development is started, and is stopped at the end of the development.

This system has a problem that it is difficult to reduce the size when the liquid developer is supplied from the front surface of the developing roller 30 as in the above example. Developing roller 30
Although it is possible to reduce the size in the case of supplying from the side surface in the axial direction, there arises a problem that the image at the end near the supply position becomes relatively dark. This is because in the liquid developer supply from the side surface direction, before the liquid developer uniformly flows in the width direction,
This is because the surface of the developing roller 30 at a position closer to the supply position is scooped up more and more, and as a result, the supply amount of the liquid developer increases toward the end closer to the supply position.

Therefore, the liquid developer cannot be fed onto the photosensitive drum in a uniform amount in the width direction. Further, when the liquid developer undulates due to the pulsation of the pump or the like, uneven density of development also occurs.

[0017]

As described above, in the conventional electrophotographic apparatus, both miniaturization of the apparatus and stable supply of the liquid developer to the photosensitive drum are achieved, and uniform development of the liquid developer is achieved. It was difficult to supply to the department.

In view of the above circumstances, the present invention is easy to miniaturize and has a simple structure. Further, regardless of the diameter of the developing roller, the liquid developer is less exposed to the air and the developing portion is not exposed. It is an object of the present invention to provide an electrophotographic apparatus capable of uniformly and stably supplying the liquid developer at a constant speed, thereby enabling stable image formation.

[0019]

[0020]

In order to solve the above problems, the present invention provides a latent image forming means for forming a latent image on a latent image holding member, and a liquid developer supplied to the latent image to make visible. In an electrophotographic apparatus having a developing means for forming an image, the developing means includes a developer carrying body carrying the liquid developer, and means for supplying the liquid developer to the developer carrying body, The means for supplying the liquid developer is arranged in the vicinity of the latent image holding member so as to face the latent image holding member and has a width substantially equal to or wider than the width of the latent image forming surface of the latent image holding member. And a guiding path for guiding the liquid developer overflowing on the latent image carrier side of the liquid developer primary storage section to the developer carrier. To do.

Further, according to the present invention, the latent image forming means for forming an electrostatic latent image on the latent image holding member, and the liquid developing for supplying a liquid developer to the electrostatic latent image to form a visible image. A liquid developer supply device of an electrophotographic apparatus, comprising: a developing means having a developer carrying body for carrying a developer, the liquid developer supplying device being disposed in the vicinity of the latent image carrying body so as to face the latent image carrying body. The liquid developer primary storage portion having a width substantially equal to or wider than the width of the image forming surface, and the liquid developer overflowing on the side of the latent image holding body of the liquid developer primary storage portion is loaded with the developer. There is provided a liquid developer supply device, characterized in that the liquid developer supply device is provided with a guiding path leading to a body.

According to the electrophotographic apparatus and the liquid developer supplying apparatus of the present invention configured as described above, a sufficient and sufficient amount of the liquid developer at the time of developing the electrophotographic liquid developing is stably supplied to the developing section. It is possible to stabilize the image.

The electrophotographic apparatus and the liquid developer supply apparatus of the present invention can further have the following aspects.

(1) The liquid surface of the liquid developer in the liquid developer primary storage portion is at a position higher in the direction of gravity than the portion on the developer carrier on which the liquid developer is supplied.

(2) The guide path for guiding the liquid developer to the developer carrying member has one end attached to the latent image holding member side of the liquid developer primary storage unit and the other end contacting the latent image holding member. It must be a flat plate-shaped member placed in the vicinity.

(3) The liquid developer primary storage portion has a liquid developer inlet on the side or bottom and a liquid developer recovery port on the bottom, and the introduction of the liquid liquid developer from the liquid developer inlet is a print. It is performed at the start, and the liquid liquid developer is collected from the liquid developer recovery port when the printing operation is stopped. (4) The liquid developer primary storage section overflows, passes through the guide path, and carries the developer. And a means for detecting the height of the liquid surface of the developer carrier that has flowed into the liquid developer pool surrounded by the body, and controls the supply speed of the liquid developer supplied to the liquid developer primary storage section. By maintaining the height of the liquid surface of the liquid developer pool constant, thereby maintaining a predetermined image density.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be shown below to explain the present invention more specifically and in detail.

FIG. 1 shows an image forming section of an electrophotographic apparatus according to an embodiment of the present invention. In the electrophotographic apparatus shown in FIG. 1, the latent image carrier 1 is a photosensitive drum having a structure in which an organic or amorphous silicon photosensitive layer is provided on a conductive substrate. The latent image carrier 1 receives the first exposure 3a by the image-modulated laser beam after the surface of the photosensitive layer is uniformly charged by the well-known first corona charger or scorotron charger 2a. ,
An electrostatic latent image is formed on the surface of the photosensitive layer. Thereafter, the electrostatic latent image is visualized by the first developing device 4a containing the liquid developer.

The liquid developer or toner particles attached to the electrostatic latent image may be directly transferred to the transfer step and transferred to the sheet by the transfer device, but here, the second step is continued.
The second electrostatic latent image is formed by the second charger 3a and the second laser exposure 3a, and the second developer of a color different from the liquid developer stored in the first developing device 4a is stored. It is developed by the second developing device 4b. Therefore, after the second development, two color toner images are formed on the latent image carrier 1.

Similarly, the third and fourth developments are carried out,
A full-color toner image is formed on the latent image carrier 1.
This toner image is transferred to the paper by the transfer device, but at that time, it may be directly transferred to the paper or may be transferred to the paper 9 through the intermediate transfer medium 6 as illustrated in FIG. good. In the transfer from the latent image carrier 1 to the intermediate transfer medium 6 and the transfer from the intermediate transfer medium 6 to the sheet 9, either transfer by electric field or transfer by pressure (and heat) can be used. . The liquid developer is
Generally, many of them can be fixed on a sheet at room temperature, but the intermediate transfer medium 6 or the like may be heated to perform fixing by heat.
Such an image forming process is described in, for example, US Pat.
No. 70,173, No. 4,202,675 and the like, which are conventionally known processes.

FIG. 2 shows the developing section of the electrophotographic apparatus according to the first embodiment of the present invention. 2 (a) is a front view, FIG.
(B) is a side view. In FIG. 2, the developing device 4 arranged around the photosensitive drum 1 includes a developing roller 10, a liquid developer primary storage portion 11 arranged laterally of the developing roller 10 in parallel with an axis, and one end of which is a liquid. Primary developer storage 1
1 and the other end is the developing roller 10
Feeding blade 12 arranged so as to come into contact with or close to
And have.

Two supply pipes 13 are connected to the bottom of the liquid developer primary storage portion 11, and the liquid developer adjusted to a predetermined concentration from a liquid developer tank (not shown) passes through the pipe 13 to form a liquid. The developer is supplied to the primary storage unit 11. The supply of the liquid developer is performed by a pump or the like (not shown), and the liquid developer is supplied to the liquid developer primary storage unit 11 or the liquid developer remaining in the liquid developer primary storage unit 11 is collected. Can also be done with this pump.

Developing roller 1 of liquid developer primary storage section 11
The side surface on the 0 side has a wall height lower than that of other portions, and one end of the supply blade 12 is attached to the edge thereof. As described above, the blade 12 is arranged such that the other end thereof is in contact with or in close proximity to the generatrix of the developing roller 10, and has a surface so as to descend obliquely from the liquid developer primary storage portion 11 toward the developing roller 10. It is inclined.

For example, the developing roller 3 of the supply blade 12
If the vicinity of 0 is made of an elastic material such as smooth urethane rubber having oil resistance, the supply blade 12 can be brought into contact with the surface of the developing roller 10 with a considerably strong force.
By doing so, the supply blade 12 can also be used as a cleaning blade. It is also possible to dispose the supply blade 12 with a slight gap between it and the developing roller 10.

The primary storage unit 11 and the supply blade 12 are arranged in the vicinity of the developing roller 10 with a width at least equal to or larger than the image forming portion on the developing roller 10. The developing roller 10 is rotatably held in the developing container 14 by a drive source (not shown). A pipe for collecting the excess liquid developer is attached to the lower part of the developing container 14.

FIG. 2B shows the liquid developer primary storage unit 11.
FIG. 6 is a view of the image forming apparatus viewed from a direction orthogonal to the rotation axis of the developing roller 30. A plurality of (two in the drawing) supply pipes 13 are connected to the bottom surface of the liquid developer primary storage unit 11. Although it is possible to provide a larger number of pipes 13, there is a drawback that the mechanism becomes complicated, and it is preferable to use as few pipes as possible.

In the developing device configured as described above, development is performed by rotating the developing roller 10 in the direction shown by the arrow in the figure. At this time, the pump (not shown)
Through the supply pipe 13, to the liquid developer primary storage section 11,
The liquid developer is sent out at a predetermined rate per unit time. When the liquid developer is sent to the liquid developer primary storage unit 11,
The liquid level in the storage unit 11 immediately rises, and the supply blade 12
Overflow from the side surface. At this time, regardless of the position of the pipe 13, the liquid developer uniformly overflows over the entire width of the supply blade 12, so that the liquid developer flows toward the developing roller 10 substantially uniformly in the width direction, and the supply blade 12 and the developing roller 10 To form a pseudo-triangular liquid developer pool composed of

The liquid developer pool is formed by the developing roller 10.
Since there is no cover in the axial direction, the liquid developer leaks from this axial portion. The height of the liquid surface of the liquid developer pool is
Determined by the amount of liquid developer supplied from the liquid developer primary storage unit 11 per unit time, the amount of liquid developer leaking from the liquid developer reservoir, and the amount of liquid developer attached to the developing roller 10 and conveyed to the developing unit. It

As the height of the liquid surface of the liquid developer pool increases, the amount of the leaked liquid developer also increases, and the height of the liquid surface of the liquid developer pool is uniquely determined. The amount of the liquid developer adhering to the surface of the developing roller 10 and conveyed to the developing unit per unit time is determined by the contact width (wetting width) of the liquid developer in the figure,
And the rotation speed of the developing roller 10. The contact width of the liquid developer is determined by the height of the liquid surface of the liquid developer pool.

From the above, if the rotation speed of the developing roller 10 and the liquid developer supply amount per unit time are set to predetermined values,
It is possible to obtain an arbitrary contact width and the amount of liquid developer attached to the developing roller 10. The excess solvent leaked from the liquid developer reservoir is collected from the lower portion of the developing container and is again transported by the pump to the liquid developer supply unit.

Further, in FIG. 2, the excess liquid developer remaining on the developing roller 10 after development is squeezed by the supply blade 12 and similarly collected, but as shown in FIG. 3, a separate squeeze blade is used. 20 may be provided and collected separately. This relates to the second embodiment of the present invention, and is an effective configuration when the excess liquid developer after development needs to be cleaned in another step.

When the development is completed, the pump is reversed to promptly collect the excess liquid developer in the developing tank through the pipe 13 to evaporate the solvent from the remaining liquid developer and to remove the toner to each part. It is possible to prevent sticking and the like.

FIG. 4 is a view showing the developing section of the electrophotographic apparatus according to the third embodiment of the present invention, in which the supply pipe 13 is
An example is provided below both end surfaces of the liquid developer primary storage unit 11. FIG. 4A is a front view and FIG. 4B is a side view.
As described above, by supplying the liquid developer from both end surfaces of the liquid developer primary storage unit 11, it is possible to smoothly supply the liquid developer without causing the liquid surface of the liquid developer to wavy.

FIG. 5 is a view showing the developing section of the electrophotographic apparatus according to the fourth embodiment of the present invention, and the supply pipe 1
3 is provided in the lower part of the side surface of the liquid developer primary storage portion 11 opposite to the surface facing the developing roller 10. FIG. 5A is a front view and FIG. 5B is a side view. By arranging the supply pipe 13 in this way, the same effect as that of the example shown in FIG. 4 can be obtained.

FIG. 6 is a view showing an electrophotographic apparatus according to the fifth embodiment of the present invention, showing an example in which the developing devices shown in FIG. 2 are arranged for each color. That is, the developing device 4 for yellow (Y)
a, a magenta (M) developing device 4b, a cyan (C) developing device 4c, and a black (K) developing device 4d are arranged facing the latent image holding member. Incidentally, the developing devices 4a, 4
The squeeze rollers 21a ...
21d are arranged respectively. These squeeze rollers 21a to 21d are arranged to remove the solvent adhering to the latent image holding body together with the toner particles.

Next, in the developing section of the electrophotographic apparatus according to the sixth embodiment of the present invention, the height of the liquid surface of the liquid developer pool, the contact width (wetting width) of the liquid developer and the image density are compared. The relationship will be described with reference to FIG. 7. First, the contact width (wetting width) of the liquid developer is proportional to the height of the liquid surface of the liquid developer pool. Next, the image density is proportional to the contact width (wetting width) of the liquid developer. Therefore, the image density is proportional to the height of the liquid surface of the liquid developer pool. The height of the liquid surface of the liquid developer pool changes depending on the supply speed of the liquid developer supplied to the liquid developer primary storage unit 11. Therefore, it is possible to control the image density by controlling the supply speed of the liquid developer.

That is, a sensor for detecting the height of the liquid surface of the liquid developer reservoir is provided, and the height of the liquid surface of the liquid developer reservoir is detected by this sensor to control the supply speed of the liquid developer. As a result, it is possible to always maintain a predetermined image density. Further, it is possible to easily control the density of the image density.

In the above-described embodiment of the present invention, the liquid developer can be supplied to the developing roller 30 uniformly in the width direction. Further, by providing the supply buffer unit (liquid developer primary storage unit) which is a temporary storage unit, the influence of pulsation of the pump or the like can be reduced as compared with the case of directly supplying without the supply buffer unit. Further, since the amount of the liquid developer attached to the developing roller 30 at the time of development can be arbitrarily set, it is possible to stably supply the liquid developer in an amount necessary and sufficient for the development, and further Efficient development is possible without having to circulate a large amount of solvent.

Since the primary storage unit does not need to immerse the developing roller 30, it can be made extremely small. Moreover, there is no need for a detection mechanism such as detection of the liquid level of the liquid developer.
With a simple configuration, the above effects can be realized with a minimum number of control elements. Also, unnecessary evaporation of the solvent from the liquid developer can be suppressed to a minimum.

[0050]

As described above, according to the present invention,
It is possible to stably supply the necessary and sufficient amount of the liquid developer to the developing section during the electrophotographic development in which the liquid development is performed, and thereby to obtain the electrophotographic apparatus capable of stabilizing the image. Moreover, the apparatus has very few control elements and has a simple structure, and the evaporation of the solvent from the liquid developer is extremely small. Moreover, there is no need to provide a reservoir conventional such large liquid developer, fried yo if caused to circulate minimum of the liquid developer, it is very efficient.

As described above, according to the present invention, stable development is performed with a simple structure, and the evaporation of the solvent is small,
Further, it becomes possible to provide an electrophotographic apparatus capable of efficiently using the liquid developer.

[Brief description of drawings]

FIG. 1 is a diagram showing an image forming unit of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a developing unit of the electrophotographic apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a developing unit of an electrophotographic apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a developing unit of an electrophotographic apparatus according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a developing unit of an electrophotographic apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a diagram illustrating an image forming unit of an electrophotographic apparatus according to a fifth exemplary embodiment of the present invention.

FIG. 7 is a diagram showing a developing unit of an electrophotographic apparatus according to a sixth embodiment of the present invention.

FIG. 8 is a diagram showing a configuration example of a developing device of a conventional electrophotographic apparatus.

FIG. 9 is a diagram showing a configuration example of a developing device of a conventional electrophotographic apparatus.

FIG. 10 is a diagram showing a configuration example of a developing device of a conventional electrophotographic apparatus.

[Explanation of symbols]

1 ... Latent image carrier (photosensitive drum) 2a, 2b, 2c, 2d ... Charger 3a, 3b, 3c, 3d ... Laser exposure 4a, 4b, 4c, 4d ... Developing device 5 ... Transfer device 6 ... Intermediate transfer member 7 ... Pressure roller 8 ... Cleaner 9 ... Paper 10 ... Developing roller 11 ... Liquid developer primary storage section 12 ... Liquid developer supply blade 13 ... Liquid developer supply and recovery pipe 14 ... Developing container 20 ... Cleaning blade 30 ... Developing roller 31 ... Photosensitive drum 30 ... Blade

Claims (2)

(57) [Claims] 1. A latent image forming means for forming a latent image on a latent image carrier and a liquid developer, and the carried liquid developer is used as the latent image forming means.
A developer carrier for supplying the image to the image carrier to develop the latent image.
And the latent image holding member is disposed in the vicinity of the latent image holding member and faces the latent image holding member.
Approximately or wider than the width of the latent image forming surface of the holder
It has a width and stores the liquid developer to be supplied to the developer carrier.
A liquid developer primary storage portion for storing, and an odor on the side of the latent image carrier of the liquid developer primary storage portion.
For guiding the overflowing liquid developer to the developer carrier
And overflows from the liquid developer primary storage section and passes through the conduit.
Liquid development surrounded by the channel and the developer carrier
Detects the height of the liquid surface of the liquid developer that has flowed into the reservoir
And the height of the liquid level detected by the detecting means.
The liquid developer supplied to the liquid developer primary storage section.
The supply speed of the image developer is set to the height of the liquid surface of the liquid developer pool.
And a means for controlling so as to maintain a constant value . 2. The liquid developer primary storage portion has a liquid developer introduction port on a side surface or a bottom surface and a liquid developer recovery port on a bottom surface, and the introduction of the liquid developer from the liquid developer introduction port is a printing image. performed at the beginning, the liquid from the liquid developer collecting port
The electrophotographic apparatus according to claim 1, wherein the body developer is collected when the printing operation is stopped.