JP2002287508A - Wet developing device and wet image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make not only a wet developing device but also a wet image forming apparatus which are made small and light, further to widen the degree of freedom in the case of designing the color wet image forming apparatus on which a plurality of wet developing apparatuses are mounted and also to prevent the variance of the developing density of a plurality of wet developing apparatuses so as to improve image quality. SOLUTION: Liquid developer 16 in a developing tank 27 is carried and supplied to the developing area of a photoreceptor drum 11 by using a developing belt 30. Thus, the tank 27 is made larger to increase the storage quantity of the liquid developer, and the circulating supply system of the developer 16 is eliminated to miniaturize the developing device 17. The tank 27 is optionally arranged so as to freely set developer 16 carrying length or a developer 16 carrying path from the tank 27 to a developing area. Thus, the developing density of a color developed image is uniformized by arranging a plurality of developing tanks under nearly the same condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet developing apparatus for developing an electrostatic latent image formed on a latent image holding member using a liquid developer having toner particles to form a developed image, and a wet image forming apparatus. Related to the device.

[0002]

2. Description of the Related Art A wet image forming apparatus for obtaining a developed image by using a liquid developer can use a very fine toner particle of a submicron size so that high image quality can be realized and a sufficient image density can be obtained with a small amount of toner. In addition, it is economical because it is possible to obtain the same quality as printing (for example, offset printing), and has an advantage that energy can be saved because toner can be fixed on paper at a relatively low temperature.

In such a wet image forming apparatus,
Conventionally, in order to obtain a toner image by developing an electrostatic latent image formed on a photoconductor, for example, US Pat. No. 5,570,173
As described in Japanese Patent Application Laid-Open No. H10-157, a developing roller partially immersed in a liquid developer in a developing tank has been used. That is, a part of the developing roller immersed in the liquid developer is arranged to face the photoreceptor, and the developing roller is rotated at a high speed to form a liquid developer layer around the liquid developer to form a liquid developer layer. A meniscus is formed in a minute area between the developing rollers to develop the electrostatic latent image on the photoconductor. Furthermore, a squeeze roller that rotates at high speed is provided to prevent fogging of the developed image due to the adhesion of the excess liquid developer, and the excess liquid developer adhering to the surface of the photoconductor is removed. It was reused.

In order to mount a developing device using such a developing roller on a wet image forming apparatus, a developing tank occupying a large space must be arranged around the photosensitive member so that the developing roller faces the photosensitive member. Therefore, there has been a great restriction on the design of the developing device body or the wet image forming device. Moreover, in the conventional developing device, if the amount of immersion of the developing roller in the liquid developer in the developing tank is reduced to less than half, the liquid developer cannot be sufficiently supplied to the photosensitive member. Since the size is limited and the storage capacity of the liquid developer is small, a large circulation supply system for constantly replenishing the liquid developer is required, which leads to an increase in the size of the developing device and an increase in price. Had a problem.

An example in which the above-mentioned conventional developing device is mounted on a color wet image forming apparatus is disclosed in Japanese Patent Application Laid-Open No. 200-200200.
No. 0-98755, etc., the chargers 2Y to 2 around the photosensitive drum 1 like the wet image forming apparatus 7 shown in FIG.
K, an exposure position where the laser beams 3Y to 3K are irradiated, a developing roller 4b and a squeeze roller 4c in a developing tank 4a.
The example in which the image forming units 5Y to 5K for each color, which include the developing devices 4Y to 4K each having a

That is, as is apparent from FIG. 15, the developing devices 4Y to 4K for each color are arranged at different angles around the photosensitive drum 1. For this reason, in consideration of the prevention of leakage of the liquid developer, each of the developing devices 4Y to 4K is designed with a different size and shape of the developing tank 4a according to the arrangement position around the photosensitive drum 1, and furthermore, complete with a seal. The design was done.

[0007]

However, when the above-described developing device is used, a plurality of developing tanks 4a for each color have to be arranged around the photosensitive drum 1, so that the size of the photosensitive drum 1 is inevitably reduced. Consequently, the wet image forming apparatus 7
There is a problem that miniaturization of the device can be hindered.

Further, in the developing devices 4Y to 4K using the developing roller 4b described above, the developing roller 4b and the squeeze roller 4b are arranged in accordance with the positions of the developing devices 4Y to 4K.
There was also a problem that the rotation control of c had to be taken for each. That is, for example, in FIG.
In the developing device 4Y, the squeeze roller 4c is
In the developing device 4K, the squeeze roller 4c is in the upward direction of gravity, as compared to the downward direction of gravity with respect to a. Second, in the developing device 4Y, the supply direction of the liquid developer by the rotation of the developing roller 4b to the photosensitive drum 1 is a direction in which gravity is applied to the liquid developer, whereas in the developing device 4K, this direction is This is the direction against the gravity applied to the developer.

Third, for example, as shown in FIG.
When the developing tank 4a is arranged horizontally as in (a), the liquid developer 8 is filled up to the upper part of the developing roller 4b, whereas the developing tank 4a is filled as in (b). In the case where the liquid developer 8 is supplied in an inclined manner, the liquid developer 8 does not fill the lower half of the developing roller 4b even though the same amount of the liquid developer 8 is supplied. Therefore, the developing roller 4b
Is rotated at the same speed, the supply amount of the liquid developer 8 becomes smaller in (b) than in (a).

For the above-described first to third reasons, the difference in the arrangement of the developing devices 4Y to 4K around the photosensitive drum 1 depends on the supply amount of the liquid developer 8 by the developing roller 4b and the squeeze by the squeeze roller 4c. In order to keep recording a stable developed image at all times, the rotation speed of the developing roller 4b and the squeeze roller 4c is finely controlled in accordance with the respective arrangements. And the adjustment becomes complicated.

In view of the above, the present invention has been made to solve the above-mentioned problems, and it is possible to reduce the size of a wet image forming apparatus by obtaining a degree of freedom in the arrangement position and shape of a developing device.
Even in a color wet image forming apparatus, it is possible to obtain a uniform image density without requiring complicated control or adjustment for each of a plurality of developing apparatuses, and to easily obtain a developed image with high display quality. It is an object to provide an apparatus and a wet-type wet image forming apparatus.

[0012]

According to the present invention, as a means for solving the above problems, there are provided a housing for storing a liquid developer containing toner particles, and a porous elastic layer for holding the liquid developer. And a developing belt that extends between the housing and the developing area of the latent image holding member, and a compression member that compresses the developing belt near the developing area.

With this configuration, the present invention does not limit the size of the housing, and always keeps the housing for storing the liquid developer horizontal regardless of the arrangement of the developing area on the latent image holding member. In order to prevent leakage of the liquid developer, it is not necessary to individually consider the shape of the housing or complete a seal.

According to the present invention, as a means for solving the above problems, there is provided a latent image holding member for holding an electrostatic latent image on a surface, a charger for uniformly charging the latent image holding member, An exposure device that irradiates the charged latent image holding member with image light corresponding to image information to form an electrostatic latent image on the latent image holding member, and stores a liquid developer containing toner particles in a housing. A developing belt having a porous elastic layer for holding the liquid developer, and being stretched between the housing and the developing region of the latent image holding member; and compressing the developing belt in the vicinity of the developing region. A developing device for supplying a liquid developer to the electrostatic latent image to form a developer image, and a transfer device for transferring the developer image on the latent image holding member to a transfer material Are provided.

With this configuration, the present invention eliminates the need to arrange a housing for storing the liquid developer around the latent image holding member, so that the degree of freedom in the position of the developing device can be increased.
As a result, the size of the wet image forming apparatus can be reduced. In addition, the size and shape of the developing device can be unified, and a plurality of developing devices for each color can be arranged under substantially the same condition regardless of the arrangement of the developing area on the latent image holding member. Therefore, it is not necessary to individually control a plurality of developing devices, and a stable and high-quality developed image can be easily obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to a first embodiment shown in FIGS. An electrophotographic apparatus 10, which is a wet image forming apparatus, has a photosensitive drum 11, which is a latent image holding member and is formed by forming an organic or amorphous silicon photosensitive layer on a conductive substrate such as aluminum. . Around the photoreceptor drum 11, along with the rotation in the direction of the arrow m, a well-known corona charger or scorotron charger is used to uniformly charge the surface of the photoreceptor drum 11 to about +800 V.
2. Exposure unit 14 irradiated with laser beam 13 image-modulated by a laser exposure device (not shown), particle size 0.1 μm
A developing device 17 for sequentially developing an electrostatic latent image formed on the photosensitive drum 11 with a liquid developer 16 having toner particles of about 2 μm and a solvent for dispersing the toner particles is provided in order.

Downstream of the developing device 17 around the photosensitive drum 11, a drying device 18 for removing excess solvent on the photosensitive drum 11, a pressing roller 20, and the pressing roller 20 press-contact the photosensitive drum 11. After transferring a developed image composed of toner particles formed on the photoconductor drum 11 to the intermediate transfer roller 21 using the adhesive force of the toner particles, the image is transferred onto a sheet 22 serving as a transfer material. A transfer device 23 for performing pressure transfer is provided. Note that the transfer device is not limited to pressure transfer, and may perform electric field transfer using electrophoresis. At the time of transfer, a pressure roller or the like may be further heated to perform heat fixing simultaneously with pressure transfer or electric field transfer.

Further, a transfer device 23 around the photosensitive drum 11
Downstream, a cleaner 24 for removing the toner image remaining on the photosensitive drum 11 after the transfer of the toner image, and an erase lamp 26 for removing the residual charge are provided.

Next, the developing device 17 will be described in detail. A tension roller 28a is provided on the bottom surface of the developing tank 27, which is a housing for storing the liquid developer 16, and a transport roller 28b, which is a transport member, is provided at a position facing the development area of the photosensitive drum 11, and the tension is provided. Roller 28a
A developing belt 30 made of a porous material having flexibility such as sponge or foam is stretched between the transport rollers 28b. The developing belt 30 is nipped and compressed by the transport roller 28b and the photosensitive drum 11 while passing through the developing area. Also, the developing belt 30
To the developing bias power supply 31 via the transport roller 28b.
As a result, a developing bias of about +600 V is applied.

Next, the operation will be described. The photosensitive drum 11 is charged to about +800 V by the charger 12 according to the rotation in the direction of the arrow m by the start of the image forming process, and then selectively irradiated with the laser beam 13 modulated based on the image information by the laser exposure device (not shown). Non-image part is about +
At 800 V, the image portion forms an electrostatic latent image of about +200 V and reaches the development area.

On the other hand, in the developing device 17, the developing belt 30 absorbs the liquid developer 16 while being immersed in the liquid developer 16 in the developing tank 27. When the developing roller 30 wrapped between the tension roller 28a and the conveying roller 28b is rotated in the direction of the arrow o by the driving of the conveying roller 28b in the direction of the arrow n during development, the liquid developer 16 absorbed by the developing belt 30 is rotated. It is sequentially supplied to the development area. In the developing area, the developing belt 30 is compressed by being sandwiched between the transport roller 28 b and the photosensitive drum 11, and the liquid developer 16 absorbed in the developing belt 30 oozes out.

In this developing area, the developing belt 30
Is applied with a developing bias of about +600 V by a developing bias power supply 31 via a conveying roller 28b, so that the liquid developer 16 oozing out from the developing belt 30 is
The toner particles in the photosensitive drum 1 due to the developing bias
The electrostatic latent image on the photosensitive drum 11 is developed and visualized by being attached to the image part by an electric field in a direction of developing the image part on the photosensitive drum 11. It is desirable that the moving speed of the developing belt 30 rotated in the direction of the arrow o and the peripheral speed of the photosensitive drum 11 in the direction of the arrow m coincide with each other within an error range of about ± 5%. If the speed difference between the developing belt 30 and the photosensitive drum 11 is ± 5% or more, the developed image on the photosensitive drum 11 may be rubbed by the developing belt 30 and disturbed.

When the developing belt 30 passes through the developing area according to the rotation of the arrow o after the development is completed, the developing belt 30
Is released from being pinched by the transport roller 28b and the photosensitive drum 11, and the compressed portion returns to its original state.
The excess liquid developer 16 that has oozed out is absorbed again. Thereafter, the developing belt 30 is returned into the liquid developer 16 in the developing tank 27 and absorbs the liquid developer 16 again, so that the next development can be performed.

On the other hand, the photosensitive drum 11 has an arrow m after the development is completed.
The excess solvent is dried and removed by the drying device 18 according to the rotation in the direction, and then reaches the transfer device 23. Transfer device 2
In No. 3, the developer image on the photoconductor drum 11 is pressure-transferred to the intermediate transfer roller 21 pressed against the photoconductor drum 11 by the load of the pressure roller 20 due to the adhesive force of the toner particles, and further the intermediate transfer. The developed image is formed on the sheet 22 by being pressure-transferred from the roller 21 to the sheet 22 conveyed in the direction of the arrow p. Further, after the transfer is completed, the photosensitive drum 11 is cleaned of the residual toner image by the cleaner 24 and the residual charge is erased by the erasing lamp 26 to complete a series of image forming processes and prepare for the next image forming process.

If the liquid developer 16 in the developing tank 27 runs out during the image forming process as described above,
After the liquid developer 16 has been used up, a new liquid developer 1
Supply 6.

With such a configuration, when a part of the developing belt 30 is immersed in the liquid developer 16, the liquid developer 16 can be easily transported and supplied to the developing area on the photosensitive drum 11. Therefore, even if the developing tank 27 is enlarged and the storage amount of the liquid developer 16 is increased, it can be used up to the end, and the size of the developing tank is restricted as in a conventional apparatus using a developing roller. Without any problem, a developing tank of a required size can be easily obtained, and the degree of freedom in designing is widened. Therefore, it is of course possible to use a circulating supply system for the liquid developer. However, it is possible to adopt a method of replacing the new liquid developer 16 after the liquid developer 16 has been used up. The circulation supply system of the developer is not required, and the size and weight of the electrophotographic recording apparatus 10 can be significantly reduced, and the cost can be reduced. Further, even when a circulating supply system of the liquid developer is used, for example, the developing tank 27 may be used.
In order to supply the insufficient pigment component by measuring the concentration of the liquid developer 16 inside, the supply system can be simplified to the extent that the concentrated liquid developer is supplied.

With this configuration, the developing belt 30
Absorbs the excess liquid developer 16 when it is released from the compression caused by being pinched between the transport roller 28b and the photosensitive drum 11 after passing through the development area and is restored, so that the squeeze roller after development becomes unnecessary. The simplification of the developing device 17 makes it possible to reduce the size, weight, and cost, and consequently, the electrophotographic
In addition to the reduction in size and weight and the reduction in cost, the degree of freedom in arranging the developing device 17 in the electrophotographic apparatus 10 can be further increased. In the first embodiment, the structure and material of the developing device are not limited as long as the developing device uses the developing belt 30. For example, a conductive material may be used for the developing belt 30. When a developing bias is applied to the conductive developing belt 30 directly or via the conveying roller 28b, the developing belt 30 is more effectively provided with the developing bias, and the developing performance can be improved. 30
When the surplus liquid developer is absorbed from above the photoreceptor drum 11 by the restoration of the toner image, it is possible to prevent the toner particles adsorbed on the electrostatic latent image from being absorbed.

Further, the developing device 17 may be configured as the first to third modified examples shown in FIGS.

A first modification shown in FIG.
i) A developing belt 30 made of a porous body having flexibility using a conductive adhesive or the like on the surface of an endless belt-shaped reinforcing belt 30a formed of a conductive material such as a metal in a thin plate or mesh shape. Are bonded to reinforce the developing belt 30.

In this way, the tension roller 28a
In addition, the tension always generated by being stretched between the transport rollers 28b and the driving force for rotating the developing belt 30 are received by the reinforcing belt 30a, and these can be prevented from being applied to the developing belt 30. Accordingly, when the porosity of the developing belt 30 made of a flexible porous material such as urethane sponge is large, the tension roller 28a
Further, the developing belt 30 cannot sufficiently hold the liquid developer 16 due to the tension generated between the conveying rollers 28b, and there is no danger that the developing belt 30 will drip.
Can absorb and hold a sufficient amount of the liquid developer 16 and transport the liquid developer 16 to the developing area, thereby realizing good development.

The second modification shown in FIG.
7, a pressure roller 32 is provided opposite to the tension roller 28a around which the developing belt 30 is stretched, and the developing roller 30 is sandwiched between the tension roller 28a and the pressure roller 32, thereby allowing the developing belt 30 to move in the direction of the arrow o. This ensures that the liquid developer 16 is absorbed by the developing belt 30 and that the liquid developer 16 absorbed in the developing belt 30 is refreshed.

This is because, even if the developing belt 30 is formed of a porous material, for example, if the material is not lipophilic, the liquid developer 16 may not easily enter the capillary formed by the porous material. is there. In such a case, the pressure is released again by sandwiching and crushing the developing belt 30 between the tension roller 28a and the pressure roller 32,
The liquid developer 16 can be forcibly filled in the capillary formed by the porous body, and the developing belt 30 can absorb the liquid developer 16 without any problem. Incidentally, even if the developing belt 30 is made of a material having no lipophilicity, the liquid developer 16 is first absorbed into the inside of the capillary by using the pressure roller 32, and thereafter, the liquid developer 16 can be removed without any problem. It can be absorbed.

Furthermore, the liquid developer 16 dries in the capillary of the developing belt 30 because, for example, the electrophotographic apparatus has not been used for a long time, so that the new liquid developer 16 is not absorbed at the next use. In such a case, the liquid developer 16 in the capillary is broken by sandwiching and deforming the developing belt 30 between the tension roller 28a and the pressure roller 32 to revive the capillary. It is also possible to be absorbed. Further, since the developing belt 30 constantly passes between the tension roller 28a and the pressure roller 32, the absorbed liquid developer 16 is once pushed out, and then the liquid developer 16 is newly absorbed. Can be refreshed by constantly replacing the liquid developer 16 absorbed by the liquid developer.

A third modification shown in FIG.
a shows the photosensitive drum 11 after development by the developing belt 30;
The squeeze bias power supply 36 applies a squeeze bias of about 500 to 600 V to remove excess liquid developer on the surface, and further includes a squeeze roller 37 that rotates in the direction of arrow q. When the development is performed by the development belt 30, when the development belt 30 separates from the development area, the excess liquid developer 16 is absorbed by the development belt 30, so that the squeeze roller is unnecessary at a normal image forming speed. However, in the above-described first embodiment, when the image forming speed becomes high-speed recording of, for example, 40 ppm or more, the excess liquid developer absorbed by the developing belt 30 becomes insufficient, and the residual toner remains on the developed image. Since the amount of the liquid developer 16 increases and causes a white background fog, by scraping off the surplus liquid developer 16 with the squeeze roller 37, a clearer developed image can be obtained. Reference numeral 38 denotes the surplus liquid developer 16 removed by the squeeze roller 37.
It is a scraper that scrapes off.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, a color image is obtained by using a plurality of the developing devices of the first embodiment described above, and the other components are the same as those of the first embodiment. The same reference numerals are given to the same components as those described in the above embodiments, and detailed description thereof will be omitted.

This is a wet image forming apparatus according to the present embodiment.
The color electrophotographic apparatus 50 stores liquid developers 16Y to 16K having different colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively, as a developing apparatus. And four developing devices 17Y to 17K having the same structure as that used in the embodiment.
These developing devices 17Y to 17K can be reciprocated in the direction of arrows AA 'by a slide device (not shown).

The color electrophotographic apparatus 5 configured as described above
When the image forming process is started at 0, the photosensitive drum 11 is charged by the charger 12 according to the rotation in the direction of the arrow m, and then yellow image data, which is the first color image data of the image information, by a laser exposure device (not shown). Is selectively irradiated with the laser beam 13 modulated on the basis of the above, an electrostatic latent image corresponding to the yellow image is formed and reaches the development area.

On the other hand, a developing device 17Y for storing a yellow (Y) liquid developer 16Y is disposed in the developing area by sliding movement. The developing device 17Y rotates in the direction of arrow o between the tension roller 28a and the transport roller 28b, and 28
The photosensitive drum 11 is developed with the yellow (Y) liquid developer 16Y by the developing belt 30 compressed by being sandwiched between the photosensitive drum 11 and the photosensitive drum 11b. After that, the photosensitive drum 11 is dried by the drying device 18, and is rotated once to hold the yellow (Y) toner image without performing the transfer operation by the transfer device 23 and the cleaning operation by the cleaner 24. After only the residual charges are erased by the erase lamp 26, a second color image forming operation is performed.

That is, similarly to the formation of the yellow (Y) toner image of the first color, the photosensitive drum 11 is charged by the charger 12 and thereafter, the red light which is the image data of the second color of the image information by the laser exposure device. Exposure is performed based on the image data to form an electrostatic latent image corresponding to a red image. In the meantime, a developing device 17M for storing the magenta (M) liquid developer 16M is disposed in the developing area by sliding movement instead of the developing device 17Y for storing the yellow (Y) liquid developer 16Y. The body drum 11 is developed by the developing device 17M to form a yellow (Y) toner image and then form a magenta (M) toner image.

By repeating the same operation four times and rotating the photosensitive drum 11 four times, yellow (Y), magenta (M), cyan (C), and black (K) are sequentially formed on the photosensitive drum 11. After the toner image is superimposed to obtain a full-color toner image, the intermediate transfer roller 21 and the cleaner 24 are brought into contact with the photosensitive drum 11, and the full-color toner image is transferred by the transfer device 23 according to the rotation of the photosensitive drum 11 in the direction of the arrow m. A full-color developed image is formed on the sheet 22 by pressure transfer to the intermediate transfer roller 21 and further pressure transfer to the sheet 22. After the transfer, the photosensitive drum 11 is cleaned of the residual toner image by the cleaner 24 and the residual charge is erased by the erasing lamp 26 to complete a series of image forming processes and prepare for the next image forming process.

With this configuration, as in the first embodiment, since the liquid developer 16 is conveyed and supplied to the photosensitive drum 11 using the developing belt 30, the developing tank 27 can be made large and large. The liquid developer can be put to practical use without using a circulation supply system, and the size and weight of the developing devices 17Y to 17K can be reduced and the price can be reduced. In particular, in the color electrophotographic apparatus 50 using a plurality of developing devices 17, Can further reduce the size and weight and reduce the cost.

The color of the liquid developer for obtaining a color image and the number of colors used are arbitrary, and are not limited to yellow (Y), magenta (M), cyan (C), and black (K).

Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment differs from the second embodiment in that a plurality of developing devices are fixedly arranged around the photosensitive drum 11 and the length of the developing belt is adjusted according to the arrangement position. Otherwise, the configuration is the same as that of the above-described second embodiment. Therefore, the same components as those described in the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

The wet image forming apparatus of the present embodiment is
The color electrophotographic apparatus 60 is provided around the photosensitive drum 11,
Liquid developers 16Y having different colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively.
Four developing devices 62Y to 62K for storing ~ 16K are fixedly arranged. Although the developing tanks 63 of the developing devices 62Y to 62K are formed in the same shape, the developing belts 67 and 68, which are stretched over the tension roller 64 and the transport roller 66 and are made of a porous material such as a foam, are formed of developing devices. It differs depending on the arrangement positions of 62Y to 62K.

That is, in the yellow (Y) and black (K) developing devices 62Y and 62K, the long developing belt 67 is used.
The developing devices 62M and 62C for magenta (M) and cyan (C) use a short developing belt 68. Each transport roller 66 is reciprocally slidable in the direction of BB 'by a driving device (not shown) so that the developing belts 67 and 68 contact the photosensitive drum 11 only when performing development. .

The color electrophotographic apparatus 6 configured as described above
When the image forming process is started at 0, the photosensitive drum 11 is charged by the charger 12 according to the rotation in the direction of the arrow m, and then yellow image data, which is the first color image data of the image information, by a laser exposure device (not shown). Is selectively irradiated with the laser beam 13 modulated on the basis of the above, an electrostatic latent image corresponding to the yellow image is formed, and reaches the developing area of the yellow (Y) developing device 62Y.

At this time, only in the yellow (Y) developing device 62Y, the transport roller 66 is slid in the direction of arrow B, and the developing belt 67 is sandwiched between the photosensitive drum 11 and the transport roller 66, but the magenta (M) , Cyan (C) and black (K) developing devices 62M to 62K, the transport roller 66 is slid in the direction of arrow B ', and the developing belts 67 and 68 are separated from the photosensitive drum 11. Therefore, the photosensitive drum 11 is developed by the yellow (Y) developing device 62Y. After that, the photosensitive drum 11 is dried by the drying device 18, and is rotated once to hold the yellow (Y) toner image without performing the transfer operation by the transfer device 23 and the cleaning operation by the cleaner 24. After only the residual charges are erased by the erase lamp 26, a second color image forming operation is performed.

That is, similarly to the formation of the yellow (Y) toner image of the first color, the photosensitive drum 11 is charged by the charger 12 and thereafter, the red color, which is the image data of the second color of the image information, by the laser exposure device. Exposure is performed based on the image data to form an electrostatic latent image corresponding to a red image, and the image reaches a developing area of the magenta (M) developing device 62M.

At this time, only in the magenta (M) developing device 62M, the transport roller 66 is slid in the direction of arrow B, and the developing belt 68 is sandwiched between the photosensitive drum 11 and the transport roller 66, but the yellow (Y) , Cyan (C) and black (K) developing devices 62Y to 62K, the transport roller 66 is slid in the direction of arrow B ', and the developing belts 67 and 68 are separated from the photosensitive drum 11. Therefore, the photosensitive drum 11 is developed by the magenta (M) developing device 62M, and forms a magenta (M) toner image after forming a yellow (Y) toner image.

By repeating the same operation four times and rotating the photosensitive drum 11 four times, yellow (Y), magenta (M), cyan (C), and black (K) are sequentially formed on the photosensitive drum 11. After the toner image is superimposed to obtain a full-color toner image, the intermediate transfer roller 21 and the cleaner 24 are brought into contact with the photosensitive drum 11, and the full-color toner image is transferred by the transfer device 23 according to the rotation of the photosensitive drum 11 in the direction of the arrow m. A full-color developed image is formed on the sheet 22 by pressure transfer to the intermediate transfer roller 21 and further pressure transfer to the sheet 22. After the transfer, the photosensitive drum 11 is cleaned of the residual toner image by the cleaner 24 and the residual charge is erased by the erasing lamp 26 to complete a series of image forming processes and prepare for the next image forming process.

With this configuration, as in the second embodiment, since the developing belts 67 and 68 are used, the size of the developing tank 27 can be increased, and a large-scale circulating supply system of the liquid developer is not used. Development device 6
2Y to 62K can be reduced in size and weight, and the price can be reduced. In particular, in the color electrophotographic apparatus 60 using a plurality of developing devices 62, the effect of further reduction in size and weight and cost can be obtained.

When a plurality of developing devices 62Y to 62K are fixedly arranged, even if the distance from each developing tank 63 to the photosensitive drum 11 is different, the developing belts 67 and 6 are not used.
8 only by adjusting the length of each of the developing devices 62Y to 62K.
Can be operated under substantially the same conditions.
A good full-color developed image can be easily obtained without requiring complicated control for each of Y to 62K. Further, since the developing tank 63 does not have to be arranged around the photoconductor drum 11, the space around the photoconductor drum 11 can be saved, and the color electrophotographic apparatus 60 can be reduced in size and weight by downsizing the photoconductor drum 11. can get.

In the case of the third embodiment, the distance from the exposure unit 14 to which the laser beam 13 is irradiated for each color to the development area of each of the developing devices 62Y to 62K is different. For this reason, this is not a problem when the image forming speed is high, but when the image forming speed is low, the potential of the electrostatic latent image at the time of development differs for each color when the photosensitive drum 11 having a large dark attenuation is used. In some cases. Therefore, when the image forming speed is low, it is desirable to use a photosensitive drum having a small dark decay.
, Depending on the distance to the development area of each color, charging voltage,
It is desirable to adjust the exposure amount and the developing bias. Incidentally, as in the fourth modification shown in FIG.
If the transport rollers 71 of Y to 70K are arranged close to each other around the photosensitive drum 11 and the developing belts 73Y to 73K are stretched between the transport rollers 71 and the tension roller 72, the exposure unit 14 Thus, the difference in the distance to the development area for each color can be reduced, the potential difference of the electrostatic latent image in the development area for each color due to dark decay can be reduced, and a stable full-color developed image can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Around the photosensitive drum 11 of the color electrophotographic apparatus 80 which is a wet image forming apparatus, yellow (Y), magenta (M), and cyan (C) are sequentially formed on the photosensitive drum 11 along the rotation in the direction of arrow m. ) And black (K) image forming units 81Y to 81K for forming images using liquid developers of yellow (Y), magenta (M), cyan (C), and black (K). Although each of the image forming units 81Y to 81K has a different color of the liquid developer and a different shape of the developing belt in the developing device,
Other than that, the configuration is basically the same, so that the yellow (Y) image forming unit 81 arranged upstream
Y will be described with reference to other image forming units 81M to 81M.
As for 1K, the same portions are denoted by the same reference numerals and suffixes indicating the respective colors, and description thereof is omitted.

The yellow (Y) image forming unit 81Y
Is a well-known corona charger or scorotron charger, which uniformly charges the surface of the photosensitive drum 11 to about +800 V, and a laser modulated by a laser exposure device (not shown) based on yellow image data. A developing unit 86Y that develops an electrostatic latent image formed on the photoconductor drum 11 with an exposure unit 84Y that is selectively irradiated with the beam 83Y and a liquid developer 16Y that includes toner particles and a solvent that disperses the toner particles. Has become.

Downstream of each of the image forming units 81Y to 81K around the photosensitive drum 11, a transfer device 23 comprising a drying device 18, a pressure roller 20, and an intermediate transfer roller 21 for transferring a developed image to a sheet 22 by pressure, and a cleaner. 24, an erase lamp 26 is provided.

The developing tank 8 of each of the developing devices 86Y to 86K
7 are formed in the same shape, but tension rollers 8
8 and the developing belts 90 to 9
In No. 2, supply routes and supply distances of the liquid developers 16Y to 16K differ depending on the arrangement positions of the developing devices 86Y to 86K.

That is, in the yellow (Y) and black (K) developing devices 86Y and 86K, the developing belts 90 and 9 are used.
2 is a tension roller 88 to a transport roller 9
The path is bent by a guide roller 96 provided between the developing tank 87 and each developing area from the developing tank 87. In the magenta (M) and cyan (C) developing devices 86M and 86C, the developing belt 91 is linearly stretched between the tension roller 93 and the transport roller 94, and is transferred from the developing tank 87 to the respective developing areas. Has reached.

The color electrophotographic apparatus 8 configured as described above
When the image forming process is started at 0, the photosensitive drum 11 is charged by the charger 82Y in the image forming unit 81Y according to the rotation in the direction of the arrow m, and is based on the yellow image data which is the image data of the first color of the image information. Is selectively irradiated with the modulated laser beam 83Y, an electrostatic latent image corresponding to a yellow image is formed, and a yellow (Y) developing device 8 is formed.
In the 6Y developing area, yellow (Y) is developed by the liquid developer 16Y of yellow (Y) oozed from the developing belt 90 sandwiched between the photosensitive drum 11 and the transport roller 94.
Is formed.

Similarly, the subsequent image forming units 81M to 81K sequentially form the photosensitive drum 11 on the photosensitive drum 11. The magenta (M), cyan (C), and black (K) toner images are superimposed to form a full-color developed image. Thereafter, the photosensitive drum 11 reaches the transfer device 23 after being dried by the drying device 18, and pressure-transfers the full-color toner image to the intermediate transfer roller 21, further pressure-transfers it to the paper 22, and prints the full-color developed image on the paper 22. Form. After the transfer, the photosensitive drum 11 is cleaned of the residual toner image by the cleaner 24 and the residual charge is erased by the erasing lamp 26 to complete a series of image forming processes and prepare for the next image forming process.

With this configuration, similarly to the second embodiment, the development is performed using the developing belts 90 to 92, so that the developing tank 87 can be made large, and a large-scale liquid developer circulating supply system can be used. Development device 81
Y to 81K can be reduced in size and weight, and the price can be reduced. In particular, in the color electrophotographic apparatus 80 using a plurality of developing devices 81, the effects of further reduction in size and weight and cost can be obtained.

Further, when a plurality of developing devices 81Y to 81K are fixedly arranged, unlike a developing device using a developing roller, the shape of each developing device is not changed so that a developing tank is arranged around a photosensitive drum. And a developing tank 87 having the same shape is arranged in a predetermined space under substantially the same conditions, and the developing belts 90 to 92 are respectively bent so that the liquid developer 1 is
Only by changing the supply distance and supply path of 6Y to 16K,
A good full-color developed image can be easily obtained without requiring complicated control. Further, since the developing tank 87 does not have to be arranged around the photosensitive drum 11, the degree of freedom in design is increased, the space around the photosensitive drum 11 can be reduced, and the size of the photosensitive drum 11 can be reduced. The size and weight of the color electrophotographic apparatus 80 can be reduced.

The arrangement of the image forming units around the photoreceptor drum 11 in the fourth embodiment is arbitrary, and the design, such as the path and length of the developing belt, can be changed completely freely. For example, a fifth modification shown in FIG. 10 or a sixth modification shown in FIG. 11 may be used.

In a fifth modification shown in FIG. 10, the yellow (Y), magenta (M), cyan (C), and black (K) image forming units 95Y to 95K are arranged on the upstream side in the rotation direction of the photosensitive drum 11. The arrangement of the transfer device 110 including the intermediate transfer roller 111 and the pressure roller 112 is changed. The developing devices 96Y to 96K of the image forming units 95Y to 95K use developing tanks 96 of the same shape, and each of the developing belts 100 to 103 stretched between the tension roller 97 and the transport roller 98 provided in the developing area. The path is bent by the guide roller 104.

In this manner, after forming the full-color developer image, a longer distance for removing the excess solvent from the photosensitive drum 11 to the transfer device 110 can be ensured. Transfer efficiency can be improved.

A sixth modification shown in FIG. 11 is a developing device having exactly the same shape in which yellow (Y), magenta (M), cyan (C), and black (K) liquid developers 16Y to 16K are stored, respectively. The yellow (Y), magenta (M), cyan (C), and black (K) image forming units 113Y to 113K provided with the devices 112Y to 112K are collectively arranged below the photosensitive drum 11.

In this way, the developing device 112 can be standardized to a single type, and the design and manufacturability can be improved.

Next, a fifth embodiment of the present invention will be described with reference to FIG. The fifth embodiment is different from the first embodiment in that the developing belt of the developing device of the first embodiment is not in contact with the photosensitive drum, and the other components are the same as those of the first embodiment. Therefore, the same components as those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The developing belt 121 of the developing device 120 of the present embodiment has a flexible porous layer 123 formed on a reinforcing belt 122 and a conductive mesh belt 124 made of metal or the like formed thereon. It is made up of A developing bias is directly applied to the mesh belt 124 by a developing bias power supply (not shown). Developing belt 12
1 is stretched between the tension roller 28a and the transport roller 28b. On the other hand, separately from the developing belt 121
A first drive roller 126 meshing with a sprocket (not shown) formed on the reinforcing belt 122,
And a second drive roller 127.

The driving speed of the developing belt 121 by the first driving roller 126 is several percent lower than the driving speed of the developing belt 121 by the second driving roller 127.
As a result, tension is applied to the developing belt 121 from the first drive roller 126 to the second drive roller 127, and the flexible porous layer 123 is moved near the transport roller 28b by the tension as shown in FIG. The portion of the photosensitive drum 11 facing the development area is crushed.
Therefore, the developing belt 123 does not come into contact with the photosensitive drum 11.

Since the outer layer of the developing belt 121 is the mesh belt 124, the crushed porous layer 1
The liquid developer 16 that has oozed out of 23 passes through the mesh belt 124 to form a meniscus 128 between the liquid developer 16 and the photosensitive drum 11. Since a developing bias is applied to the mesh belt 124, an electric field in the direction of developing the electrostatic latent image on the liquid developer 16 acts on the meniscus 128 to develop the electrostatic latent image on the photosensitive drum 11. It will be. If the porous layer 123 and the mesh belt 124 are made conductive, it becomes possible to apply a developing bias via the transport roller 28b as in the first embodiment. After passing through the developing area, the tension is weakened and the developing belt 121
Of the photoconductive drum 11
The surplus liquid developer on the upper side is absorbed by the porous layer 123 again.

With this configuration, as in the first embodiment, since the developing belt 121 is used, the developing tank 2 is used.
7 can be made large, and can be put to practical use without using a large-scale circulating system or supply system for the liquid developer, and the developing device 17 can be reduced in size and weight and in price. Further, after passing through the developing area, the developing belt 121 returns from the crushed state, so that the surplus liquid developer 16 can be absorbed and the squeeze roller becomes unnecessary.

Further, in the case of performing development by bringing the developing belt into contact with the photosensitive drum, a difference of several percent or more in the speed between the developing belt and the photosensitive drum causes rubbing of the developed image, resulting in poor image quality. Since the developing belt 121 and the photosensitive drum 11 are not in contact with each other, the peripheral speed of the photosensitive drum 11 and the peripheral speed of the developing belt 121 need to be strictly adjusted. The effect of disappearing is obtained. Therefore, for example, since the developing belt 121 is formed of the flexible porous layer 123 or the like, the developing belt 12
Even if the peripheral speed of 1 greatly changes, or if the speed difference greatly changes partially due to unexpected vibration, etc.,
There is no risk of rubbing of the developed image
The deterioration of the developed image due to the speed difference between the photosensitive drum 11 and the photosensitive drum 11 can be prevented, and the display quality can be improved.

Further, the developing belt 121 and the photosensitive drum 1
1 is not in contact, the peripheral speed of the developing belt 121 can be increased irrespective of the peripheral speed of the photoconductor drum 11, and in the case of high-speed recording that requires a large amount of liquid developer. Even if it is, a sufficient concentration can be obtained. The structure and material of the developing device in the fifth embodiment are not limited as long as the photosensitive drum and the developing belt are not in contact with each other. For example, the seventh modified example shown in FIG. An eighth modified example shown in FIG.

In a seventh modification shown in FIG. 13, the transport roller 130 around which the developing belt 121 is wound is a hollow roller having a large number of through-holes 131, and a squeeze nozzle 132 is provided inside the hollow in the direction of the development end position. Install
Excess liquid developer after passing through the developing area is forcibly sucked in the direction of arrow r by vacuum (not shown).

In this way, the surplus liquid developer after development can be more reliably suctioned and removed by using the squeeze nozzle 132 in addition to suction by restoring the development belt 121 after passing through the development area.

In this modification, the hollow conveying roller may be a roller formed of metal or resin and having a large number of through holes, or may be formed of a porous ceramic.

In an eighth modification shown in FIG. 14, instead of using the first drive roller 126 and the second drive roller 127 to crush the porous layer 123 by applying tension,
In the developing area, the photosensitive drum 11 and the developing belt 12
1, a conductive mesh guard 133 to which a developing bias is applied is provided. Then, by sandwiching the developing belt 121 between the mesh guard 133 and the transport roller 28b, the porous layer 123 is crushed to exude the liquid developer 16, and a meniscus 134 is formed between the photosensitive drum 11 and the developing layer. Do. Mesh guard 133
The excess liquid developer is sucked in the porous layer 123 which is restored after being released from being held between the sheet and the transport roller 28b.

With this configuration, since the tension is not applied to the developing belt 121, the restoring property of the developing belt 121 after passing through the developing area is good, and the excess liquid developer can be sufficiently sucked. Further, since the developing bias is directly applied to the mesh guard 133, the developing performance can be improved.

The present invention is not limited to the above-described embodiment, and can be changed without departing from the spirit of the present invention. There is no particular limitation as long as it can be transported to the development area of the body. The latent image holding member may also be a photoreceptor belt having a photoreceptor layer formed on the surface of a rotatable annular elastic belt, or the transfer means may be directly transferred from the photoreceptor drum to the paper without an intermediate transfer roller. It is optional. Further, when a color image is obtained, the color may not be superimposed on the latent image holding member, but may be superimposed on the intermediate transfer member.

[0081]

As described above, according to the present invention, the size of the housing for storing the liquid developer is not restricted and the degree of freedom in designing the developing device is increased. Also, by increasing the size of the housing to increase the storage amount of the liquid developer, it is not necessary to use a large-scale circulating supply system of the liquid developer as in the related art. Pricing is possible. Further, since the squeeze roller is not required, the size and weight of the developing device can be reduced, and the cost can be reduced. Further, by mounting such a developing device, it is possible to reduce the size, weight, and cost of the wet image forming apparatus.

Further, in the case of a color wet image forming apparatus, the degree of freedom in designing a plurality of developing devices is increased and a plurality of developing devices can be arranged under substantially the same conditions. The complicated control performed to prevent the variation in the development density caused by the difference in the position is not required, and a stable color developed image can be easily obtained. Further, since the space for disposing the developing device around the latent image holding member can be significantly reduced, the size of the latent image holding member can be reduced, and the size and weight of the color wet image forming apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an electrophotographic apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a developing device according to the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram illustrating a part of a developing belt according to a first modified example of the invention.

FIG. 4 is a schematic configuration diagram illustrating a part of a developing belt according to a second modified example of the invention.

FIG. 5 is a schematic configuration diagram illustrating a developing device according to a third modification of the present invention.

FIG. 6 is a schematic configuration diagram illustrating an electrophotographic apparatus according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram illustrating an electrophotographic apparatus according to a third embodiment of the present invention.

FIG. 8 is a schematic configuration diagram illustrating an electrophotographic apparatus according to a fourth modification of the present invention.

FIG. 9 is a schematic configuration diagram illustrating an electrophotographic apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram illustrating an electrophotographic apparatus according to a fifth modification of the present invention.

FIG. 11 is a schematic configuration diagram illustrating an electrophotographic apparatus according to a sixth modification of the present invention.

FIG. 12 is a schematic configuration diagram illustrating a part of a developing belt according to a fifth embodiment of the present invention.

FIG. 13 is a schematic configuration diagram illustrating a part of a developing belt according to a seventh modified example of the invention.

FIG. 14 is a schematic configuration diagram illustrating an electrophotographic apparatus according to an eighth modification of the present invention.

FIG. 15 is a schematic configuration diagram showing a conventional electrophotographic apparatus.

16A and 16B are schematic configuration diagrams showing a conventional developing device, in which FIG. 16A shows a case where the developing tank is horizontal, and FIG. 16B shows a case where the developing tank is inclined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Electrophotographic apparatus 11 ... Photoconductor drum 12 ... Charger 13 ... Laser beam 14 ... Exposure part 16 ... Liquid developer 17 ... Developing device 18 ... Drying device 20 ... Pressure roller 21 ... Intermediate transfer roller 22 ... Paper 23 ... Transfer device 24 ... Cleaner 26 ... Erase lamp 27 ... Development tank 28a ... Tension roller 28b ... Transport roller 30 ... Development belt 31 ... Development bias 32 ... Pressure roller 37 ... Squeeze roller

Claims (2)

[Claims] 1. A housing for storing a liquid developer containing toner particles, and a porous elastic layer for holding the liquid developer. A wet developing device comprising: a developing belt to be transferred; and a compression member that compresses the developing belt near the developing area. 2. A latent image holding member for holding an electrostatic latent image on a surface thereof, a charger for uniformly charging the latent image holding member, and an image information on the uniformly charged latent image holding member. An exposing device that forms an electrostatic latent image on the latent image holding body by irradiating corresponding image light; and a porous elastic body that stores a liquid developer containing toner particles in a housing and holds the liquid developer. A developing belt having a layer and extending from the housing to the developing area of the latent image holding member; and a compression member for compressing the developing belt near the developing area, wherein the electrostatic latent image A developing device for supplying the liquid developer to the developer to form a developer image, and a transfer device for transferring the developer image on the latent image holding member to a transfer material. apparatus.