JP2000162877A - Liquid developing apparatus and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a satisfactory quantity of liquid toner possible to be uniformly fed with respect to a photoreceptor surface which rotates at a high speed. SOLUTION: A doctor blade 47 is disposed close to the periphery of a developing roller 45. The developing roller 45 is allowed to feed a liquid toner LT in a liquid toner container 42 on a photoreceptor drum 10 by letting the same stuck on the surface thereof through rotation, and to let an electrostatic latent image on the developing roller 45 surface be visualized (develop). By means of the doctor blade 47, bubbles B generated when the developing roller 45 is rotated at high speed are crushed, and unevenness of the liquid film of the liquid toner LT derive from the centrifugal force over the shaft AX direction is relaxed. Therefore, even if the developing roller 45 is made to rotate at the high speed, the liquid toner can be applied uniformly with respect to the photoreceptor drum 10 surface rotating at the high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developing apparatus for converting an electrostatic latent image on a photoreceptor into a toner image, and an electrophotographic apparatus using the same, such as an electrophotographic copying machine and an electrophotographic printer.

[0002]

2. Description of the Related Art As a liquid developing device in an electrophotographic apparatus such as an electrophotographic copying machine, a roller developing system is often used. In the roller developing type liquid developing device, the liquid toner is pumped up by being attached to the outer peripheral surface of the developing roller and supplied to the surface of the photoreceptor. The electrostatic latent image on the photoreceptor surface is developed and visualized by the liquid toner, and then transferred and fixed on a sheet.

[0003]

In such a liquid developing apparatus, when the developing roller supplies the liquid toner to the photoconductor, new liquid toner is always sufficiently supplied to the surface of the photoconductor. It is necessary to rotate the developing roller at a speed higher than the peripheral speed.

In order to increase the processing speed in the liquid developing device, the peripheral speed of the photoconductor must be increased. In this case, it is necessary to further increase the rotation speed of the developing roller as the peripheral speed of the photoconductor increases.

However, as shown in FIG. 8, when the rotation speed of the developing roller 145 around the central axis AX is further increased, a portion where the centrifugal force F exceeds the surface tension occurs, or the liquid toner LT B in the liquid film
The thickness of the liquid toner LT formed on the outer peripheral surface of the developing roller 145 becomes non-uniform due to the occurrence of, for example, and the supply of the liquid toner LT to the photoconductor surface becomes non-uniform, so that the image quality is reduced. Is reduced.

In view of the above problems, the present invention provides a liquid developing apparatus capable of uniformly supplying a sufficient amount of liquid toner to the surface of a photoreceptor orbiting at high speed, and an electrophotographic apparatus using the same. The purpose is to provide.

[0007]

According to a first aspect of the present invention, there is provided a liquid developing apparatus which visualizes an electrostatic latent image formed on a photoreceptor surface using a liquid toner. A developing device, comprising: a liquid toner container for storing liquid toner; and a rotatable developing roller provided at a position close to the photoconductor, wherein the liquid toner in the liquid toner container adhered to an outer peripheral surface thereof. A developing roller that supplies the photosensitive member by rotation, a doctor blade disposed at a position close to the outer peripheral surface of the developing roller,
It is characterized by having.

A liquid developing apparatus according to a second aspect is the liquid developing apparatus according to the first aspect, wherein the doctor blade is fixed with a predetermined gap between the doctor blade and an outer peripheral surface of the developing roller. It is characterized by that.

A liquid developing device according to a third aspect of the present invention is the liquid developing device according to the first aspect, wherein the doctor blade is resiliently biased toward the developing roller. The doctor blade is arranged so as to be in contact with the outer peripheral surface, and when the developing roller rotates, the doctor blade is lifted from the outer peripheral surface of the developing roller by a liquid film of liquid toner formed on the outer peripheral surface of the developing roller. Features.

A liquid developing apparatus according to a fourth aspect is the liquid developing apparatus according to the second aspect, wherein the doctor blade includes a plurality of unit doctor blades, the developing roller and the plurality of unit doctor blades. The gap formed between each of them is gradually reduced as approaching the photoconductor in the direction of rotation.

According to a fifth aspect of the present invention, there is provided an electrophotographic apparatus comprising the liquid developing device according to any one of the first to fourth aspects.

In this specification, the term "close" means that both of them are close to each other with a predetermined gap, and that the distance between them is zero, that is, both are in contact with each other. It is a concept including

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <A. First Embodiment><OverallConfiguration> FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus 1 according to a first embodiment of the present invention. The electrophotographic apparatus 1 includes an image signal supply unit 100, a photosensitive drum 10, a charging unit 20,
Exposure unit 30, developing unit 40, squeeze roller 50, transfer unit 60, fixing unit 70, cleaner unit 80, and charge removing unit 9
0 is provided.

The charging unit 20 uniformly charges the surface of the photoconductive drum 10 having photoconductivity, and the exposing unit 30 controls the photoconductive drum 10 based on the image signal SG supplied from the image signal supplying unit 100. The surface of the photosensitive drum 10 is formed by selectively exposing the surface of the photosensitive drum 10 to remove (discharge) the charge in the exposed portion, thereby leaving the charge in the unexposed portion. The developing unit 40 performs liquid development for attaching a liquid toner to the electrostatic latent image formed on the surface of the photoreceptor drum 10 and visualizing the electrostatic latent image. After the squeeze roller 50 squeezes out the excess liquid toner, the transfer unit 60 transfers the spatial pattern of the liquid toner formed on the photosensitive drum 10 to the paper 2 on the transfer drum 61 of the transfer unit 60. Then, the fixing unit 70 fixes the transferred liquid toner on the paper 2 by heating. Further, the cleaner unit 80 including the sponge roller 81 and the wiper 83 removes the liquid toner slightly remaining on the photosensitive drum 10,
Further, the charge removing section 90 removes the charge on the surface of the photosensitive drum 10 by light and AC corotron. As described above, the photosensitive drum 10 rotates the charging unit 20, the exposure unit 30, the developing unit 40, and the squeeze roller 5 with the rotation in the direction of the arrow AR2.
0, undergo processing by the transfer unit 60, the cleaner unit 80, and the charge removing unit 90. Then, the electrophotographic apparatus 1 can form a predetermined image on the paper 2 in the transfer unit 60 and the fixing unit 70.

<Configuration of Developing Unit 40> Next, the developing unit 40 will be described with reference to an enlarged view of FIG. The developing unit 40 includes a liquid toner tank 41, a liquid toner container 42,
A supply path 43 having a pump P, a discharge path 44, a developing roller 45, a cleaning blade 46, and a doctor blade 47 are provided.

The liquid toner LT stored in the liquid toner tank 41 is pumped into the liquid toner container 42 via the supply path 43 by the operation of the pump P. Then, the liquid toner LT pumped into the liquid toner container 42 is stored in the liquid toner container 42, and a part of the liquid toner LT is discharged to the liquid toner tank 41 via the discharge path 44.
Thus, the liquid toner LT is supplied to the liquid toner container 4
2 is circulated. During the circulating supply, the flow rate of the pump P is controlled such that the liquid level of the liquid toner LT stored in the liquid toner container 42 is kept constant.

The developing roller 45 is provided at a position close to the photosensitive drum 10 so that a predetermined minute gap Δd1 exists between the developing roller 45 and the developing roller 45. It is immersed in the liquid toner LT. The outer peripheral surface 45S of the developing roller 45 is made of an elastic material such as urethane rubber or a rigid body such as stainless steel, copper, or Teflon (registered trademark of DuPont). As shown in the perspective view of FIG. 3, the developing roller 45 is rotatable about a central axis AX, and rotates the liquid toner of the liquid toner container 42 attached to the outer peripheral surface 45S of the photosensitive drum by rotation. Supply 10

The cleaning blade 46 is made of an elastic material such as urethane rubber, and is fixed at a position in contact with the outer peripheral surface 45S of the developing roller 45. The cleaning blade 46 is connected to the developing roller 45.
The liquid toner LT that has aggregated and adhered to the outer peripheral surface 45 </ b> S of the developing roller 45 is removed with the rotation of the developing roller 45.

The doctor blade 47 has an outer peripheral surface 45 that is parallel to the longitudinal direction (direction C) of the developing roller 45 (see FIG. 3).
It is arranged at a position close to S. In the present embodiment, the doctor blade 47 is a rigid body made of a material such as stainless steel or copper. As shown in FIG. 4, even when the developing roller 45 is not rotating (when stopped), the blade tip 47t and the developing roller 45 is fixed so as to have a predetermined minute gap Δd2 between itself and the outer peripheral surface 45S. This gap Δd2 is preferably set to be larger than the gap Δd1. For example, when Δd1 is about 100 μm,
Δd2 can be from about 100 μm to about 200 μm. As will be described later, the doctor blade 47 plays a large role in the present invention.

<Operation of Developing Unit 40> Next, the operation of the developing unit 40 will be described with reference to FIG. When the developing roller 45 rotates around the central axis AX in the direction of the arrow AR1 in a state where a part thereof is immersed in the liquid toner LT in the liquid toner container 42, the developing roller 45 The outer surface 45S of the toner LT is
To form a liquid film of the liquid toner LT. The thickness of this liquid film is Δd3 near the liquid surface F1.

Here, when the rotation of the developing roller 45 is increased, air B is generated near the liquid level F1 due to the presence of air above the liquid level F1, and the air bubbles B are generated by the liquid toner LT.
Will be present in the liquid film.

However, in the present embodiment, the doctor blade 47 has a value Δd2 smaller than Δd3.
Are arranged between the developing roller 45 and the developing roller 45. Therefore, the film thickness of the liquid toner LT, which was Δd3 near the liquid level F1, is reduced to Δd2 by the doctor blade 47, and at the same time, the bubbles B are crushed and disappear. After that, the liquid film formed on the outer peripheral surface of the developing roller 45 further approaches the photosensitive drum 10 by the rotation of the developing roller 45 and is supplied to the photosensitive drum 10. As described above, the doctor blade 47 eliminates the bubble B, thereby avoiding the above-described problem caused by the bubble B and moving the liquid film of the liquid toner LT supplied to the photosensitive drum 10 in the direction C (see FIG. 3). Over the entire surface.

Further, even when the bubble B is not completely eliminated by the doctor blade 47, the same effect can be obtained by pulverizing the large-diameter bubbles into small-diameter bubbles. This is because, when the large-diameter bubbles are eliminated, a situation in which the liquid toner LT is not supplied on the photosensitive drum 10 can be substantially avoided.

Further, the gap between the doctor blade 47 and the developing roller 45 has a constant value Δd2 in the longitudinal direction (direction C). The unevenness of the film thickness due to the centrifugal force caused by the high-speed rotation can be reduced.

As described above, the developing unit 40 supplies a sufficient amount of the liquid toner L to the surface of the photosensitive drum 10 circulating at high speed.
T can be supplied uniformly. Therefore, the electrophotographic apparatus 1
Can perform high-speed processing using the developing unit 40.

<B. Second Embodiment> The second embodiment is the same as the first embodiment except for the configuration of the doctor blade. The doctor blade 47A of the present embodiment is an elastic body made of a rubber having solvent resistance such as urethane rubber, and as shown in FIG. When the developing roller 45 is not rotating (stopped), the outer peripheral surface 45S of the developing roller 45 and the blade tip 4 of the doctor blade 47A are urged toward the outer peripheral surface 45S.
7t. Then, as shown in FIG. 6, when the developing roller 45 rotates in the direction of the arrow AR1, the developing roller 45 causes the liquid toner LT in the liquid toner container 42 to adhere to the surface thereof to form a liquid film of the liquid toner LT. I do. At this time, the doctor blade 47A is pushed up by the liquid film of the liquid toner LT formed on the surface of the developing roller 45, and floats from the developing roller 45, so that a gap is formed between the doctor blade 47A and the developing roller 45. When the rotation of the developing roller 45 is stabilized in a steady state, a gap Δd2 similar to that of the first embodiment is formed between the doctor blade 47A and the developing roller 45. Therefore, similarly to the first embodiment, the liquid toner LT on the surface of the developing roller 45
The bubbles B in the liquid film are crushed, and the influence of the centrifugal force due to the high-speed rotation of the developing roller 45 is reduced.
Non-uniformity of the film thickness can be corrected.

The doctor blade 47A may be formed by processing a material such as stainless steel or copper into a thin plate to have the same elasticity as described above.

<C. Third Embodiment> The third embodiment is the same as the first embodiment except for the configuration other than the doctor blade. As shown in FIG. 7, the doctor blade 47B of the present embodiment includes a plurality of (three) unit doctor blades 47Ba, 47Bb, and 47Bc. The blade tips of the unit doctor blades 47Ba, 47Bb, 47Bc have gaps Δea, Δeb,
Δec. These gaps formed between the developing roller 45 and each of the plurality of doctor blades 47Ba, 47Bb, 47Bc gradually decrease as the developing roller 45 approaches the photosensitive drum 10 in the direction of the rotation AR1, and Δea>. It has a relationship of Δeb> Δec.

When the developing roller 45 rotates, the developing roller 45 moves the liquid toner LT in the liquid toner container 42.
To form a liquid film of the liquid toner LT. Δd3 near the liquid level F1 (normally, Δd3> Δe
The film thickness of the liquid toner LT which was a) is reduced to Δea by the doctor blade 47Ba, then reduced to Δeb by the doctor blade 47Bb, and further reduced to Δec by the doctor blade 47Bc. Thus, the bubbles B in the liquid film of the liquid toner LT on the surface of the developing roller 45 are crushed and disappear.
Since the doctor blade 47B eliminates the bubbles B, the above-described problem caused by the bubbles B can be avoided, and the liquid film of the liquid toner LT supplied to the photosensitive drum 10 can be made uniform. Further, the influence of the centrifugal force due to the high-speed rotation of the developing roller 45 is reduced, and the unevenness of the film thickness can be corrected.

It is preferable that Δec be the same gap as Δd2 in the first and second embodiments. Further, according to the present embodiment, a plurality of doctor blades 47 are provided.
By adjusting the thickness of the liquid film to be gradually reduced by B, the film thickness can be made uniform in a stepwise manner, so that the degree of uniformity can be improved. In addition, when the difference between Δd3 and Δec (Δd2) is large, the effect of uniformization is particularly large.

<D. Modification> In the second embodiment,
By making the doctor blade 47A itself elastic, the doctor blade 47A
A gap is formed between the developing roller 45 and the developing roller 45. However, the present invention is not limited to this, and a structure may be employed in which a rigid doctor blade is biased toward the developing roller 45 by an elastic body such as a spring.

In the above embodiment, the rotation direction AR1 of the developing roller 45 and the rotation direction AR2 of the photosensitive drum 10 are opposite, but may be the same. In any case, it is sufficient if the developing roller 45 rotates at a peripheral speed equal to or higher than that of the photosensitive drum 10 so that new liquid toner LT can always be supplied to the surface of the photosensitive drum 10.

[0033]

As described above, claims 1 to 4 are as described above.
According to the liquid developing device described in the above, a developing roller that supplies the liquid toner in the liquid toner container to the photoconductor by rotation,
A doctor blade arranged at a position close to the developing roller. Since this doctor blade uniformly adjusts the thickness of the liquid toner on the outer peripheral surface of the developing roller,
It is possible to prevent the film thickness from becoming uneven due to the centrifugal force caused by the rotation of the developing roller. Further, even when bubbles are generated in the liquid toner film on the outer peripheral surface of the developing roller due to high-speed rotation of the developing roller, the generated bubbles can be crushed by the doctor blade, so that the film thickness of the liquid toner can be made uniform. it can. Therefore, a sufficient amount of liquid toner can be uniformly supplied by rotating the developing roller at a high speed with respect to the surface of the photoreceptor that rotates at a high speed.

In particular, according to the liquid developing device of the present invention, the gap formed between each of the plurality of unit doctor blades and the developing roller becomes closer to the photosensitive member in the direction of rotation of the developing roller. Since the thickness of the liquid toner is gradually reduced, the thickness of the liquid toner formed on the outer peripheral surface of the developing roller can be gradually reduced to be uniform. Therefore, the degree of uniformity can be further improved.

According to the electrophotographic apparatus of the present invention, the same effects as those of the liquid developing apparatus of the present invention can be obtained. The processing speed of the electrophotographic apparatus as a whole can be improved by improving the image quality.

[Brief description of the drawings]

FIG. 1 is a side view showing a schematic structure of an electrophotographic apparatus 1 according to a first embodiment of the present invention.

FIG. 2 is an enlarged side view showing a schematic configuration near a developing unit 40.

FIG. 3 is a perspective view schematically showing a developing roller 45 and a doctor blade 47.

FIG. 4 is a schematic side view showing a doctor blade 47 (when the developing roller 45 is stopped).

FIG. 5 is a schematic side view showing a doctor blade 47A (when a developing roller 45 is stopped) of a second embodiment.

FIG. 6 is a schematic side view showing a doctor blade 47A (at the time of rotation of a developing roller 45) according to a second embodiment.

FIG. 7 is a schematic side view showing a doctor blade 47B (when a developing roller 45 is rotating) of a third embodiment.

FIG. 8 is a conceptual diagram illustrating a state of a liquid toner LT during rotation of a developing roller 145 according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrophotographic apparatus 2 Paper 10 Photoreceptor drum 20 Charging part 30 Exposure part 40 Development part 41 Liquid toner tank 42 Liquid toner container 43 Supply path 44 Discharge path 45, 145 Developing roller 45S Outer peripheral surface (of developing roller) 46 Cleaning blade 47 , 47A, 47B Doctor blade 47Ba, 47Bb, 47Bc Unit doctor blade 60 Transfer unit 70 Fixing unit B Bubble LT Liquid toner LT

Claims (5)

[Claims] 1. A liquid developing device for visualizing an electrostatic latent image formed on a surface of a photoreceptor by using a liquid toner, comprising: a liquid toner container for storing the liquid toner; A rotatable developing roller provided at a position, the developing roller supplying the liquid toner in the liquid toner container adhered to the outer peripheral surface to the photoconductor by rotation, and a developing roller proximate to the outer peripheral surface of the developing roller. And a doctor blade disposed at a position where the liquid developing device moves. 2. The liquid developing device according to claim 1, wherein the doctor blade is fixed with a predetermined gap between the doctor blade and an outer peripheral surface of the developing roller. . 3. The liquid developing device according to claim 1, wherein the doctor blade is disposed so as to be in contact with an outer peripheral surface of the developing roller while being elastically urged toward the developing roller. And a liquid film of liquid toner formed on an outer peripheral surface of the developing roller when the developing roller rotates, whereby the doctor blade floats up from an outer peripheral surface of the developing roller. 4. The liquid developing device according to claim 2, wherein the doctor blade includes a plurality of unit doctor blades, and is formed between the developing roller and each of the plurality of unit doctor blades. The liquid developing device according to claim 1, wherein the gap gradually decreases as approaching the photoconductor in the direction of rotation. 5. An electrophotographic apparatus comprising the liquid developing device according to claim 1. Description: