JPH0922194A - Wet type developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel device capable of attaining development for a high-quality image not having irregularities in a density, surface fogging, etc., at high speed, without especially adopting a complicated large-sized constitution. SOLUTION: The wet type developing device is provided with an intermediate developer carrier 2 which is arranged to abut on an electrostatic latent image carrier 1 and capable of applying a fixed developing bias voltage and a wet type developing means 3 for uniformly developing the intermediate developer carrier 2 with a liquid developer and constituted so that the intermediate developer carrier 2 has the first development with the liquid developer by the wet type developing means 3, to uniformly carry a toner layer and a carrier liquid by a specific amount and the second development for developing an electrostatic latent image formed on the electrostatic latent image carrier 1 is attained by the intermediate developer carrier 2 uniformly carrying the toner layer and carrier liquid by the specified amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image recording device such as a copying machine or a printer, and more particularly, to an electrostatic latent image formed on an electrostatic latent image carrier in a carrier liquid. The present invention relates to a wet developing device that visualizes a visible image using a liquid developer in which toner particles are dispersed.

[0002]

2. Description of the Related Art Conventionally, as a technique relating to this type of wet developing device, for example, a wet recording device described in USP 5,231,454 and JP-A-4-156488 and JP-A-4-238375 are disclosed. The described wet developing device and the like have already been proposed.

The wet recording apparatus described in US Pat. No. 5,231,454, as shown in FIG. 12, is an electrostatic latent image carrier 1 on which an electrostatic latent image is formed by a well-known electrophotographic process.
00, a roll-shaped developing electrode 10 having a large diameter.
1 is arranged. The roll-shaped developing electrode 101 is rotationally driven in the direction opposite to the electrostatic latent image carrier 100 in the liquid developing section A. Then, on the electrostatic latent image carrier 100, on the upstream side of the liquid developing section A which is close to the roll-shaped developing electrode 101, a predetermined one of yellow, magenta, cyan and black colors is selected by the liquid developer supply nozzle 102. The liquid developers 103Y, 103M, 103C, and 103K of the colors are ejected and supplied. The liquid developers 103Y, 103M, 103 of yellow, magenta, cyan, and black
C and 103K are the liquid developers 103Y and 103 of the respective colors.
Liquid developer tanks 104Y, 104M, 104C, 104K containing M, 103C, 103K are supplied with liquid developer 103Y, 103 of a predetermined color via a pump 105.
M, 103C and 103K are liquid developer supply nozzles 102
It is supplied to. In the liquid developing section A, as shown in FIG. 13, according to the developing electric field formed by the difference between the electrostatic latent image potential on the electrostatic latent image carrier 100 and the developing bias voltage of the roll-shaped developing electrode 101. The toner in the liquid developer is moved and adhered onto the electrostatic latent image carrier 100 to form a toner image 106. In FIG. 13, the electrostatic latent image is formed by the positive charge 107, and the toner 106 in the liquid developer 103 is the negatively charged toner 106.

Further, as shown in FIG. 13, the excess developing solution 108 adheres to the roll-like developing electrode 101 and is collected in the liquid developing section A after the developing process is completed, but this is not enough. For the purpose of collecting the excess developer 108 that remains with the toner image on the electrostatic latent image carrier 100, as shown in FIG.
An excess developer control roller 109 is arranged on the downstream side of the above, and the excess developer 108 is removed.

Further, the liquid developer 103 attached and collected on the roll-shaped developing electrode 101 is collected and reused by the collecting means 110Y, 110M, 110C and 110K provided for each color. At the same time, the surface of the roll-shaped developing electrode 101 has the collecting means 110Y, 110M,
It is cleaned by 110C and 110K.

In the wet recording apparatus disclosed in US Pat. No. 5,231,454, the liquid developer 10 in the liquid developing section A is used.
Since the circulation of No. 3 is good, the decrease in image density due to the lack of the developer hardly occurs. Further, since the large-diameter roll-shaped developing electrode 101 is used to increase the area facing the electrostatic latent image carrier 100 and the liquid developing section A is widened, the development speed can be increased. have.

On the other hand, in the latter wet developing devices disclosed in Japanese Patent Laid-Open Nos. 4-156488 and 4-238375, as shown in FIG. 14, an electrostatic latent image carrier 100 and a small diameter contacting the electrostatic latent image carrier 100 are provided. Having a roll-shaped developing electrode 111 of
These electrostatic latent image carrier 100 or roll-shaped developing electrode 1
Liquid developer 103 is evenly applied to any one of the liquid developer supply nozzles 112, and electrostatic latent image carrier 100
Development is performed in the vicinity B of the contact portion of the roll-shaped developing electrode 111.

Since a very small gap is formed in the vicinity B of the contact portion between the electrostatic latent image carrier 100 and the roll-shaped developing electrode 111, a strong developing electric field is generated. Further, in the vicinity B of the contact portion, since the liquid developer 103 applied to the electrostatic latent image carrier 100 or the roll-shaped developing electrode 111 forms the developer pool 113, the vicinity of the contact portion B has high speed and high speed. It has a feature that high-definition liquid development is possible.

Further, the roll-shaped developing electrode 111 is
Since it is pressed against the electrostatic latent image carrier 100, it has an effect of squeezing the developing solution at the same time as the development, and the developer 103 that did not contribute to the development does not pass through the contact portion B and the non-image portion is not formed. It also has the feature that no background fog occurs.

[0010]

However, the above-mentioned prior art has the following problems. First, in the case of the wet type recording apparatus adopting the non-contact developing method described in the former USP 5,231,454, as shown in FIG. 12, the electrostatic latent image carrier 1 is discharged from the liquid developer supply nozzle 102.
Since the liquid developer 103 is directly supplied onto the liquid developer 00 and the development is performed in the non-contact liquid developing portion A, unevenness in density is likely to occur due to uneven supply of the liquid developer 103 supplied from the liquid developer supply nozzle 102. There is a problem. Further, in the case of the wet type recording apparatus adopting the non-contact developing method, since the development is performed even in a large gap (distance) between the roll-shaped developing electrode 101 and the electrostatic latent image carrier 100, the electrostatic latent image is formed. There is also a problem that the edge effect of the developing electric field that acts on the edge portion of the image is large, and that the tailing phenomenon and the density unevenness easily occur at the rear end portion of the solid image portion due to the effect. Further, in the case of the wet type recording apparatus adopting this non-contact developing method, the liquid developer supply nozzle 102
The liquid developer 103 is directly supplied from above to the electrostatic latent image carrier 100 and the electrostatic latent image carrier 100 is developed by the liquid developer 103 flowing to the liquid developing section A. There is also a problem that a flow pattern is likely to occur in a developed image.

Further, in the case of the wet recording apparatus adopting the non-contact developing system, the toner 106 moves in the gap between the electrostatic latent image carrier 100 and the roll-shaped developing electrode 101 by electrophoresis according to the developing electric field. However, since the development area A is large, the development speed is relatively slow, and it is difficult to obtain a sufficient image density at high speed. Further, in order to increase the speed, the liquid development section A should be further widened. In this case, the roll-shaped developing electrode 101 may be used.
It is necessary to further increase the diameter of the above components, which causes another problem of increasing the size of the device.

Further, in the case of the wet type recording apparatus adopting the non-contact developing method, it is difficult to regulate the uniform minute developing gap in manufacturing, and as described above, the density unevenness and the flow pattern caused by the gap are caused. There is a problem that it occurs.

On the other hand, in the case of the latter type wet developing apparatus described in Japanese Patent Laid-Open No. 4-156488 and Japanese Patent Laid-Open No. 4-238375, as shown in FIG.
Liquid developer 10 supplied from the developer supply nozzle 112
Not only density unevenness due to uneven supply of 3 is likely to occur,
Since the development is performed even in a large gap between the roll-shaped developing electrode 111 and the electrostatic latent image carrier 100, the edge effect is large, and the circulation of the liquid developer 103 stored in the developer storage portion 113 is poor, so that the flow occurs. However, on the contrary, the liquid developer 103 accumulated in the developing solution reservoir 113 depending on the amount of toner consumption depending on the size of the image portion.
However, there is a problem in that the density of the toner changes and uneven density tends to occur.

In the case of the latter wet developing device, the excess toner passes through the contact portion B between the two unless the roll-shaped developing electrode 111 is pressed against the electrostatic latent image carrier 100 with a considerably high pressure. And the fog is generated, and conversely, the roll-shaped developing electrode 111 is attached to the electrostatic latent image carrier 1.
When it is pressed against 00 with a high pressure, the contact part B of both
In the above, there is a problem that the toner image is crushed and the reproducibility of fine lines is deteriorated, the contour of the high density image portion is blurred, and the developed toner is squeezed to cause density unevenness.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and its object is to prevent density unevenness, background fog, etc. without taking a particularly complicated and large structure. It is an object of the present invention to provide a novel wet developing device capable of developing a high quality image which does not exist at high speed.

[0016]

As shown in FIG. 1, a wet developing apparatus according to a first aspect of the present invention is designed to transfer an electrostatic latent image formed on an electrostatic latent image carrier 1 to a carrier liquid. In a wet type developing device which develops with a liquid developer having toner dispersed therein to form a visible image, it is arranged so as to contact the electrostatic latent image carrier 1 and a predetermined developing bias voltage can be applied. An intermediate developer carrying member 2 and a wet developing means 3 for uniformly developing with a liquid developer on the intermediate developer carrying member 2 are provided. First development is carried out on the developer carrying member 2 so as to uniformly carry a predetermined amount of toner layer and carrier liquid,
Second development for developing the electrostatic latent image formed on the electrostatic latent image carrier 1 is performed by using the intermediate developer carrier 2 on which the predetermined amount of toner layer and carrier liquid are uniformly carried. It is configured to do.

Further, a wet developing apparatus according to a second aspect of the present invention is the wet developing apparatus according to the first aspect, wherein the image portion potential of the electrostatic latent image formed on the electrostatic latent image carrier is The potential contrast with the developing bias voltage applied to the intermediate developer carrier is made larger than the potential contrast required to develop the toner amount that achieves the desired maximum density of the final recorded image, and the wet development The predetermined toner amount developed on the intermediate developer bearing member by the means is set to the minimum toner amount necessary to achieve the desired maximum density of the final recorded image.

Further, the wet developing device according to claim 3 of the present invention is the wet developing device according to claim 1 or 2, wherein the wet developing means is on the periphery of the intermediate developer carrier. A toner layer thickness adjusting means which is in contact with the intermediate developer bearing member and is rotated in the same direction at the same peripheral speed and which has at least a roll member to which a bias voltage can be applied is disposed in the subsequent stage.

The wet developing device according to claim 4 of the present invention is the wet developing device according to any one of claims 1 to 3, wherein the amount of toner developed on the intermediate developer carrying member. And the amount of toner on the intermediate developer carrier after passing through the contact portion between the electrostatic latent image carrier and the intermediate developer carrier and the electrostatic latent image after passing through the contact portion. A toner amount sensor that detects at least one of the toner amounts on the image carrier is provided, and the contact pressure between the intermediate developer carrier and the electrostatic latent image carrier is adjusted based on the signal from the toner amount sensor. To do.

[0020]

The wet developing device according to the present invention has the following actions.

First, as shown in FIG. 1, the wet developing means 3 is used.
Thus, the intermediate developer carrier 2 is uniformly developed. This development is performed by a developing bias voltage (hereinafter, referred to as V _D ) applied to the developing electrode 4 of the wet developing means 3 and a developing bias voltage (hereinafter, referred to as V _T ) applied to the intermediate developer carrier 2. The toner in the liquid developer adheres to and deposits on the surface of the intermediate developer carrier 2 by electrophoresis.

This development is carried out until the developing electric field is neutralized by the charge of the toner developed and attached to the intermediate developer carrier 2. Therefore, by controlling V _D and V _T , it is possible to accurately and uniformly control the amount of toner developed on the intermediate developing carrier 2.

Further, since the wet developing means 3 only needs to uniformly develop the intermediate developer carrier 2, it is not necessary to consider the background fog in the non-image area, and a high-concentration liquid developer is used. It is possible to Thereby, the wet developing means 3
Thus, development on the intermediate developer carrying member 2 can be performed at high speed.

Further, the toner developed on the intermediate developer carrying member 2 is subjected to an electrical restraining force, an adhesive force between the toner and the intermediate developer carrying member 2, and an adhesive force between the toners. It is in a state of being semi-fixed and attached on the carrier 2.

Further, the wet developing means 3 is provided with a liquid amount control means as required, so that the amount of carrier liquid adhered to the intermediate developer carrying member 2 can be arbitrarily controlled. As a result, the flow of the adhered toner on the intermediate developer carrier 2 caused by the excessive carrier liquid, liquid spillage due to the diaphragm effect at the contact portion (C in the figure) with the electrostatic latent image carrier 1, and the like. Can be prevented more reliably.

Next, the electrostatic latent image formed on the electrostatic latent image carrier 1 is developed by the intermediate developer carrier 2 to which a controlled amount of toner layer is attached.

FIG. 2 is an enlarged view of a contact portion C between the electrostatic latent image carrier 1 and the intermediate developer carrier 2.

The intermediate developer carrying member 2 is elastically contacted with the electrostatic latent image carrying member 1 at an appropriate pressure and rotates in the same direction at the same peripheral speed. The toner 5 attached in a semi-fixed state to the intermediate developer carrier 2 and the carrier liquid 6 whose liquid amount is regulated
Is conveyed to the contact portion C with the electrostatic latent image carrier 1 as the intermediate developer carrier 2 rotates.

Here, the appropriate pressure of the contact portion C means
The toner layer 5 adhered to the intermediate developer carrier 2 in a semi-fixed state has such a pressure that it is not disturbed by the diaphragm effect at the contact portion C, and almost all of the transported toner is in the contact portion C.
Pass through.

Further, a very small gap is formed in the vicinity of the contact portion C between the electrostatic latent image carrier 1 and the intermediate developer carrier 2, and the electrostatic latent image is formed in this gap. The image portion potential of the electrostatic latent image on the carrier 1 (hereinafter, referred to as V ₁ ) and the non-image portion potential (hereinafter, referred to as V _BKG )
And a developing bias V _T applied to the intermediate developer carrying member generates a strong developing electric field. Further, in the contact portion C, a very strong developing electric field is generated via the transported toner layer 5.

Then, the toner layer 5 conveyed to the contact portion C
As shown in FIG. 2, due to the developing electric field at the contact portion C, in the image portion of the electrostatic latent image, the electrostatic latent image carrier 1 is directed, and in the non-image portion, the intermediate developer carrier 2 is directed. When receiving an electric attraction force and passing through the contact portion C, the electrostatic latent image carrier 1 and the intermediate developer carrier 2 are moved according to the developing electric field.
The upper part is divided and a second development is performed.

According to this method, the toner layer 5 is conveyed to the contact portion C (developing portion) in a semi-fixed state on the intermediate developer carrying member 2 and is not affected by the liquid flow. Further, since development is not carried out where the distance between the electrostatic latent image carrier 1 and the intermediate developer carrier 2 is large, the edge effect does not occur. Further, since the amount of toner supplied to the contact portion C is controlled to be constant, there is no characteristic that density unevenness due to excess or deficiency of toner does not occur.

In addition, the toner layer 5 conveyed to the contact portion C
Is separated from the state of contact with the electrostatic latent image through a very small gap and is developed, which enables high-definition development. Also, since this development does not rely on toner electrophoresis, high-speed development is possible. Is possible.

Further, since the toner layer 5 is subjected to the pressure contact effect at the contact portion C, the toner image 7 is in a tightened state, so that the transfer in the subsequent process can be favorably performed.

Further, according to the wet type developing apparatus of the present invention, the non-image portion potential V _BKG of the electrostatic latent image formed on the electrostatic latent image carrier 1 and the intermediate developer carrier 2 are applied. The potential contrast with the developing bias voltage V _T (cleaning potential contrast) is controlled to be larger than the potential contrast when the intermediate developer carrier 2 is developed by the wet developing means 3.

As a result, all the toner 8 on the intermediate developer carrier 2 which is in contact with the non-image portion of the electrostatic latent image on the electrostatic latent image carrier 1 is electrically electrically charged to the intermediate developer carrier 2. Since it is strongly attracted to the top, it does not adhere to the non-image portion on the electrostatic latent image carrier 1 when it comes out from the contact portion C, and the occurrence of background fog can be effectively suppressed.

Next, the operation of the wet developing apparatus according to the second aspect of the present invention will be described.

The electrostatic latent image formed on the electrostatic latent image carrier 1 generally contains noise during the formation process, and the electrostatic latent image itself has potential unevenness.

In particular, in the case of a digital image, it is originally a binary image in terms of density and the image portion potential V ₁ to be developed is
If there is noise, uneven density occurs remarkably.

Therefore, according to the wet type developing device of the second aspect of the present invention, the image portion potential of the electrostatic latent image formed on the electrostatic latent image carrier 1 and the intermediate developer carrier 2 are formed. The potential contrast with the applied developing bias voltage V _T is made larger than the potential contrast required to develop the toner amount that achieves the desired maximum density of the final recorded image, and the wet developing means 3 causes the intermediate The predetermined toner amount developed on the developer carrying member 2 is set to the minimum toner amount necessary for achieving the desired maximum density of the final recorded image.

As a result, excessive toner may be developed or the amount of toner that has been potential-developed may become insufficient, particularly due to the level of the image portion potential of the electrostatic latent image in the binary image as described above. It is possible to reduce uneven density due to noise of the electrostatic latent image itself.

Further, the toner on the intermediate developer carrying member 2 which is brought into contact with the image portion of the electrostatic latent image is electrically strongly attracted to the electrostatic latent image carrying member 1, so that the contact portion C is When it passes, the toner is favorably peeled off from the intermediate developer carrying member 2 and the toner remaining on the intermediate developer carrying member 2 disappears, and image defects such as density unevenness resulting from this can be prevented.

Further, in the wet developing apparatus according to the third aspect of the present invention, in the wet developing apparatus, an electrostatic latent image is provided on the periphery of the intermediate developer carrier 2 at a stage subsequent to the wet developing means 3. Before the contact portion C with the carrier 1, the intermediate developer carrier 2
The toner layer thickness adjusting means having at least a roll member that is in contact with the roller and is rotated in the same direction at the same peripheral speed and to which the developing bias voltage can be applied is arranged.

As a result, by tightening the toner layer 5 on the intermediate developer carrying member 2, the toner layer 5 conveyed to the contact portion C with the electrostatic latent image carrying member 1 is not likely to be disturbed. Moreover, the allowable range of the contact pressure of the contact portion C can be widened.

According to a fourth aspect of the present invention, in the wet developing apparatus, the amount of toner developed on the intermediate developer carrier 2 and the electrostatic latent image carrier 1 and the intermediate developer in the wet developer apparatus. Amount of toner on the intermediate developer carrier 2 after passing through the contact portion C with the developer carrier 2 and amount of toner on the electrostatic latent image carrier 1 after passing through the contact portion C A toner amount sensor for detecting at least one of the above is disposed, and the contact pressure between the intermediate developer carrier 2 and the electrostatic latent image carrier 1 is adjusted based on a signal from the toner amount sensor.

As a result, the contact pressure between the electrostatic latent image carrier 1 and the intermediate developer carrier 2 can be stably adjusted to the appropriate pressure as described above over time, resulting in poor development. It is possible to reliably prevent the occurrence of the above.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

FIG. 3 shows a wet electrophotographic printer mechanism section which is an embodiment of a wet recording apparatus to which the liquid developing apparatus according to the present invention is applied. Of course, the present invention can be applied to all image forming apparatuses using a liquid developer other than the electrophotographic method.

In FIG. 3, reference numeral 20 denotes a photosensitive drum as an electrostatic latent image bearing member.
Is a known photosensitive member having solvent resistance to the liquid developer used, and is driven at a predetermined rotational speed in the direction of the arrow by a driving device (not shown). As the electrostatic latent image carrier 20,
The liquid developer used may be any known and photosensitive drum or belt having solvent resistance.

Around the photosensitive drum 20, a charging scorotron 21, an image exposing device 26, and an intermediate developing device as an intermediate developer carrying member which constitutes a part of the wet developing device 13 according to the embodiment of the present invention. Roll 15 and transfer drum 2
2, a cleaning device 23, and an erase lamp 24 are arranged. A wet developing means 14 for uniformly developing a predetermined amount of liquid developer on the intermediate developing roll 15 is arranged below the intermediate developing roll 15.

At the time of image formation, the photosensitive drum 20 is rotationally driven in the direction of the arrow by a driving device (not shown). The surface of the photoconductor drum 20 is first uniformly charged to a predetermined potential by the charging scorotron 21. In this embodiment, the surface of the photoconductor drum 20 is configured to be positively and uniformly charged. As described above, on the surface of the photosensitive drum 20 that is uniformly charged, the laser ROS 26 (Raste
The image is exposed by the r Output Scanner), and an electrostatic latent image corresponding to the image exposure is formed.

After that, the electrostatic latent image formed on the photoconductor drum 20 is developed into a toner image by a developing process which will be described in detail later, and the developed toner image is once shown on the transfer drum 22. Then, the recording paper 25 is transferred onto the recording paper 25 by the transfer roll 35 and finally subjected to a fixing process, and the recording paper 25 is discharged to the outside of the apparatus. At that time, when a color image is formed, the toner images of a predetermined number of colors may be superposed on the transfer drum 22 and finally transferred onto the recording paper 25. The toner images of a predetermined number of colors on the transfer drum 22 may be directly superposed on the transfer drum 22, but the recording paper 2 may be placed on the transfer drum 22.
It is of course possible to transfer the toner images of a predetermined number of colors in a superposed state on the recording paper 25 held on the transfer drum 22 in the state of holding 5.

After the transfer, the cleaning device 23 removes the residual adhered substances from the photosensitive drum 20, and the erase lamp 24 erases the residual charges, thereby preparing for the next image recording step.

By the way, the wet type developing apparatus according to this embodiment is arranged so as to contact the electrostatic latent image carrier, and an intermediate developer carrier capable of applying a predetermined developing bias voltage, and the intermediate developer carrier. A wet developing means for uniformly developing with a liquid developer on the body, and a predetermined amount of toner layer and carrier liquid on the intermediate developer carrier using the liquid developer by the wet developing means. The first development for carrying is carried out, and the electrostatic latent image formed on the electrostatic latent image carrying body is developed by using the intermediate developer carrying body carrying the predetermined amount of toner layer and carrier liquid. 2 is configured to be developed.

That is, the wet developing device 13 is shown in FIG.
As shown in FIG. 3, an intermediate developing roll 15 as an intermediate developer carrying member that comes into contact with the surface of the photoconductor drum 20, and a wet developing unit 14 that uniformly develops a predetermined amount of liquid developer on the intermediate developing roll 15. It consists of and.

As the intermediate developing roll 15, for example, conductive fine particles are dispersed in rubber having a solvent resistance to the liquid developer to be used, and the conductive fine particles are dispersed on the outer periphery of a conductive roll-shaped substrate made of a metal cylinder or the like. What coat | covered the elastic body layer which adjusted the sex is used. Fluorine-based rubber (for example, product name “Viton rubber”) is used as an example of the rubber material of the elastic body layer, and as the conductive fine particles, for example,
Carbon particles are used. The intermediate developing roll 15 may be provided with an insulating outermost layer. As the insulating outermost layer, a fluorine-based rubber layer in which conductive fine particles are not dispersed is used, or A body film (for example, PET film product name “Mylar film”) wound and adhered is used. The thickness of the elastic layer of the intermediate developing roll 15 is not particularly limited, but the thickness of the outermost insulating layer is preferably set to about 10 to 30 μm.

As the wet developing means 14, any type of wet developing device can be used as long as it has at least a developing electrode and has a liquid amount regulating function. It is possible to use, for example, one using a developing electrode in the shape of a circle.

In this embodiment, the wet developing means 14 is formed so as to have the same polar radius as the intermediate developing roll 15 as shown in FIG.
5, a plate-shaped developing electrode 27 opposed to each other via a minute gap, an intermediate developing roller 15, and a roll member 28 rotatably arranged via a minute gap are used.

In the wet developing means 14, the liquid developer is supplied from the developer tank (not shown) to the small gap G between the plate-shaped developing electrode 27 and the intermediate developing roller 15 through the pump through the slit 29. It is being supplied.

Further, as the liquid developer used in the wet developing means 14, any known liquid developer can be used. For example, a high resistance petroleum solvent (for example, manufactured by Exxon Corporation) is used as a carrier liquid. Toner particles composed of pigment and acrylic resin in this carrier liquid, a charge control agent that adjusts the polarity and charge amount of the toner particles, and promote dispersion of the toner particles and maintain dispersion stability. A liquid developer formed by dispersing a dispersion stabilizer and the like is included.

A developing bias voltage V _D is applied to the plate-like developing electrode 27 by a power source 36 and a developing electric field generated by a potential difference from the developing bias voltage V _T applied by the power source 37 to the intermediate developing roll 15. Accordingly, the toner particles in the liquid developer are electrophoresed, adhere to and deposit on the surface of the intermediate developing roller 15, and development (first development) is performed. Here, the developing bias voltage V _D applied to the plate-shaped developing electrode 27 and the intermediate developing roll 15
By controlling the developing bias voltage V _T applied to the intermediate developing roller 15, it is possible to accurately control the amount of toner developed on the intermediate developing roller 15.

Further, since the wet developing means 14 has only to uniformly develop the intermediate developing roll 15, it is not necessary to consider the background fog in the non-image area as in the normal development, and high density liquid developing is possible. Since the agent can be used, this first development can be performed at high speed.

Further, after passing through the plate-shaped developing electrode 27, the excess carrier liquid adhering to the intermediate developing roll 15 is removed by the roll member 28 as shown in FIG. The roll member 28 is rotationally driven by a rotary drive mechanism (not shown), and is normally rotated in a direction opposite to the rotational direction of the intermediate developing roll 15 as shown by the arrow in the figure. Further, the roll member 28 is the intermediate developing roll 1
In order to stably form a minute gap with the tracking roller 5, the tracking roller members 30 that are rotatably contacted with the peripheral surface of the intermediate developing roller 15 are provided at both ends of the roller member 28.

As a result, the excess carrier liquid adhering to the intermediate developing roll 15 is removed by the shearing force generated according to the speed difference between the surface of the intermediate developing roll 15 and the surface of the roll member 28. Further, by controlling the gap between the intermediate developing roll 15 and the roll member 28 and the rotation speed of the roll member 28, the amount of carrier liquid remaining on the intermediate developing roll 15 can be arbitrarily controlled. Further, if the bias voltage can be applied to the roll member 28 as needed so as to have the effect of the developing electrode, the speed of the first development can be further increased. The roll member 28 is provided with a scraper 31 so as to scrape off and collect the excess developer adhering to the roll member 28.

Further, the toner 16 uniformly developed on the intermediate developing roll 15 receives an electric binding force by the developing bias voltage V _T applied to the intermediate developing roll 15, and also has an intermediate property with the toner. Due to the adhesive force with the developing roll 15 and the adhesive force between the toners, the toner is carried in a semi-fixed state on the intermediate developing roll 15.

As shown in FIG. 5, the semi-fixed toner layer 16 in which the amount of the toner adhered onto the intermediate developing roll 15 and the carrier liquid 17 in which the liquid amount is regulated are as shown in FIG.
As the intermediate developing roll 15 rotates, the photosensitive drum 2
It is conveyed to the contact portion C with 0. This intermediate developing roll 15
Is elastically contacted with the photoconductor drum 20 and is rotated at the contact portion C so as to move in the same direction as the photoconductor drum 20 at the same speed.

Here, the contact pressure at the contact portion C between the intermediate developing roll 15 and the photosensitive drum 20 is such that the toner layer 16 on the intermediate developing roll 15 is not disturbed by the diaphragm effect at the contact portion C. It is set to pressure.

Further, a very small gap is formed in the vicinity of the contact portion C between the photosensitive drum 20 and the intermediate developing roller 15, and this minute gap has a small gap.
A strong developing electric field is formed by the image portion potential V ₁ and the non-image portion potential V _{BKG of} the electrostatic latent image formed on the photosensitive drum 20 and the developing bias voltage V _T applied to the intermediate developing roll 15. There is. In the contact portion C,
The image portion potential V ₁ and the non-image portion potential V _{BKG of the} electrostatic latent image and the intermediate developing roll 1 through the conveyed toner layer 16.
With the developing bias voltage V _{T of} 5, a very strong developing electric field is directly generated.

Toner layer 16 conveyed to the contact portion C
As shown in FIG. 5, due to the developing electric field at the contact portion C, an electrostatic attraction force is applied to the photosensitive drum 20 in the image portion of the electrostatic latent image and to the intermediate developing roll 15 in the non-image portion. When the toner is received and comes out of the abutting portion C, the photosensitive drum 20 and the intermediate developing roll 15 follow the developing electric field.
The upper part is separated and development (second development) is performed.

After the second development is completed, the toner layer is uniformly formed on the intermediate transfer roll 15 again by the first development by the liquid developing means 14, and the second continuous development is performed.
Can be developed. However, even when the first development is performed again on the intermediate transfer roll 15,
If a significant difference in toner layer thickness occurs between the part where toner is consumed and the part where toner is not consumed,
As shown in FIG. 4, the toner remaining on the intermediate transfer roll 15 is collected in the liquid developing means 14 by the scraping member 32 arranged in the liquid developing means 14, and the collected toner is reused. Alternatively, the first development may be newly performed again.

By the way, according to the wet type developing apparatus of this embodiment, since the electrostatic latent image on the photosensitive drum 20 is not developed by the electrophoresis of the toner, it is not affected by the flow of the developing solution, and High-speed development is possible. Furthermore, since the electrostatic latent image and the toner are separated from the contact state via a very small gap and developed, high-definition development becomes possible.

Further, since the toner layer 16 is pressed against the contact portion C, the toner image becomes tight,
Good transfer in the subsequent process. At the same time, since the excess carrier liquid is squeezed at the contact portion C, it is not necessary to remove the excess liquid on the photosensitive drum 20 after development.

As the intermediate developing roll 15, as described above, an elastic roll or a roll covered with an elastic body is used so as to come into elastic contact with the photosensitive drum 20. When an endless belt is used as the intermediate developer carrier instead of a roll, an elastic layer is provided in the belt structure, or the photosensitive member is contacted with the photosensitive drum 20 from the back side of the belt to the photosensitive member. The rotatable support member that presses and supports the drum 20 may be made of an elastic body.

As a result, at the contact portion C with the photosensitive drum 20, the contact portion C is reliably formed even at a low pressure that does not squeeze the conveyed toner layer 16, and the photosensitive drum 20 and A contact failure between the two due to the eccentricity of the intermediate developer carrying member 15 is eliminated, and a development failure resulting therefrom can be prevented. Further, by elastically abutting the photosensitive drum 20 and the intermediate developer carrying member 15, it is possible to uniformly remove the excess carrier liquid 17 by squeezing.

Further, in this embodiment, an endless roll or belt used as the intermediate developer carrying member 15 is coated with an insulating material or a high resistance material. As a result, it is possible to prevent the development density from decreasing and the development unevenness from occurring due to the leakage of the electrostatic latent image on the intermediate developer carrying member 15 and the photosensitive drum 20.

Further, in this embodiment, as shown in FIG. 6, the non-image portion potential V _BKG of the electrostatic latent image formed on the photosensitive drum 20 and the development applied to the intermediate developer carrier 15. The contrast V ₃ (cleaning potential contrast) with the bias voltage V _T is controlled so as to be higher than the potential contrast V ₄ when the intermediate developing roll 15 is developed by the wet developing means 14.

As a result, all the toner on the intermediate developing roll 15 which is in contact with the non-image portion of the electrostatic latent image on the photosensitive drum 20 is electrically strongly adsorbed on the intermediate developing roll 15. When it comes out from the contact portion C, it does not adhere to the non-image portion on the photoconductor drum 20, and it is possible to effectively prevent the occurrence of background fog.

Further, in the wet developing apparatus according to this embodiment, at least the toner amount necessary for achieving the maximum density of the final recorded image must be developed and supplied onto the intermediate developer carrier 15 by the wet developing means 14. Because I have to
The larger the electrostatic capacitance C _{T of the} endless roll or belt used as the intermediate developer carrying member 15, the more advantageous the potential contrast when developing the intermediate developing unit 15 by the liquid developing unit 14 can be reduced. Is.

Second Embodiment FIGS. 7 to 9 show a second embodiment of the present invention.
The same parts as those in the above-described embodiment will be described with the same reference numerals. In the second embodiment, the image portion potential of the electrostatic latent image formed on the electrostatic latent image carrier and the intermediate developer carrier. The potential contrast with the developing bias voltage applied to the body is made larger than the potential contrast required to develop the toner amount that achieves the desired maximum density of the final recorded image, and the intermediate developing is performed by the wet developing means. The predetermined toner amount developed on the agent carrier is set to the minimum toner amount required to achieve the desired maximum density of the final recorded image.

That is, with respect to the bias voltage V _T applied to the intermediate developing roll 15, the photosensitive drum 2 is usually used.
With the voltage between the image portion potential V ₁ of the electrostatic latent image formed on 0 and the non-image portion potential V _BKG , only the toner amount necessary to achieve the maximum density of the final recorded image is developed. Selected to produce a development contrast of.

However, the electrostatic latent image formed on the photosensitive drum 20 may include noise during the formation process, and the electrostatic latent image itself may have potential unevenness. For example, the photoconductor drum 20 is uniformly charged by the charging scorotron 21, but here, charging unevenness as shown in FIG. 7 occurs first. Further, when an image is exposed on the photoconductor drum 20, exposure unevenness due to noise of the laser ROS 26 also occurs. Further, potential unevenness due to charging ability of the photoconductor drum 20 and uneven light attenuation also occurs.

In particular, in the case of a digital image, since it is an image which is originally binary in terms of density, if the potential V ₁ to be developed has noise as shown in FIG. The density unevenness is noticeable.

Therefore, the wet developing device according to the second embodiment is used.
In the case of, as shown in FIG. 9, the image portion potential of the electrostatic latent image
V₁And the developing bias voltage applied to the intermediate developing roll 15.
Pressure V _TPotential contrast (development potential contrast)
Is required to achieve the maximum density of the final recorded image.
Potential greater than the potential contrast to which the amount of toner is attached
Image part potential of electrostatic latent image so as to form contrast
V₁And development bias voltage V_THas been selected. Also, the liquid
It is developed on the intermediate developing roll 15 by the body developing means 14.
The controlled, predetermined amount of toner is the maximum darkness of the final recorded image.
Is set to the minimum amount of toner needed to achieve
You.

As a result, it is possible to cancel the uneven density due to the height of the image portion potential of the electrostatic latent image as described above in the binary image without developing the toner more than necessary. It is possible to reduce the density unevenness of the developed image due to the noise of the latent image itself.

Further, the toner on the intermediate developing roller 15 which is in contact with the image portion of the electrostatic latent image is strongly attracted to the photosensitive drum 20 electrically, and therefore, when passing through the contact portion C, the toner is intermediate. The toner is satisfactorily peeled off from the developing roller 15, and the toner remaining on the intermediate developing roller 15 is eliminated, so that it is possible to prevent image defects such as uneven density of the developed image due to this.

Specifically, the developing potential contrast required to develop the toner amount required to achieve the desired maximum density of the final recorded image on the photosensitive drum 20 used in this embodiment is as shown in FIG. As shown in 9, it was 350V.

The electrostatic capacity C _T of the intermediate developing roller 15 used in this embodiment is the electrostatic capacity C _T of the photosensitive drum 20.
A developing potential contrast of about 175V was required in order to develop and supply by the liquid developing means 14 a toner amount which is about twice _P and which is necessary to achieve the desired maximum density of the final recorded image.

When the photosensitive drum 20 is first charged to 850 V (target potential) as shown in FIG. 9, ± 2
A potential unevenness of about 0 V was confirmed, and the image portion (non-exposed portion) potential at the developing position (contact portion C with the intermediate developing roll 15) was 750 V ± 30 V. In addition, the photosensitive drum 2
The non-image area (exposed area) potential of 0 was 75V ± 15V.

Therefore, in this embodiment, as shown in FIG. 9, the photosensitive drum 20 was charged to 850 V and a voltage of 300 V was applied to the intermediate developing roller 15 as the developing bias voltage V _T. Therefore, the development potential contrast is 45
It was set to 0V ± 30V. Further, as shown in FIG. 6, a bias voltage V _{D of} 125 V is applied to the developing electrode 27 of the liquid developing means 14 so as to achieve the desired maximum density of the final recorded image on the intermediate developing roll 15. A large amount of toner was developed and supplied.

Under the above electrical conditions, a high-quality image without density unevenness and background fog could be formed at high speed.

Third Embodiment FIG. 10 shows a third embodiment of the present invention. The same parts as those of the above-mentioned embodiment are designated by the same reference numerals, and a description will be given.
In the third embodiment, on the periphery of the intermediate developer carrying member and after the wet developing means, the intermediate developer carrying member is brought into contact with the intermediate developer carrying member to rotate in the same direction at the same peripheral speed, and a bias voltage is applied. The toner layer thickness adjusting means having at least a possible roll member is arranged.

In the wet type recording apparatus according to this embodiment, as shown in FIG. 10, after the liquid developing means 14 on the circumference of the intermediate developing roll 15, the intermediate developing roll 15 is brought into contact with the same developing speed in the same direction. Toner layer thickness adjusting means 3 that has an elastic roll member 33 that is rotated and to which a bias voltage can be applied and that adjusts the thickness of the toner layer 16 on the intermediate developing roll 15.
5 are arranged.

The toner layer thickness adjusting means 35 uses the elastic pressure applied by the elastic roll member 33 and the electrical action by applying a bias voltage in the direction of pressing the toner layer 16 onto the intermediate developing roll 15. Layer 1
6 is squeezed to adjust the thickness (tighten).
As the bias voltage applied to the elastic roll member 33, a bias voltage having the same polarity as the toner is selected. Further, as described above, since the bias voltage V _T having a polarity opposite to that of the toner is applied to the intermediate developing roll 15, the elastic roll member 33 may be grounded.

As a result, the adhesive force between the intermediate developing roll 15 and the toner layer 16 and between the toners is increased, so that the toner layer 16 is less likely to be disturbed by the contact portion C between the photosensitive drum 20 and the intermediate developing roll 15. Therefore, stable development (second development) becomes possible.

The elastic roll member 33 is cleaned by the blade 34 which is in contact with the elastic roll member 33.

Fourth Embodiment FIG. 11 shows a fourth embodiment of the present invention. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals, and a description will be given.
In the fourth embodiment, the amount of toner developed on the intermediate developer carrying member and the intermediate developer carrying member after passing through the contact portion between the electrostatic latent image carrying member and the intermediate developer carrying member. A toner amount sensor for detecting at least one of the upper toner amount and the toner amount on the electrostatic latent image carrier after passing through the abutting portion is provided, and the intermediate amount is detected based on a signal from the toner amount sensor. The contact pressure between the developer bearing member and the electrostatic latent image bearing member is adjusted.

In the wet recording apparatus according to the fourth embodiment, the toner amount T1 developed on the intermediate developing roller 15 and the intermediate developing roller after passing through the contact portion C between the photosensitive drum 20 and the intermediate developing roller 15 are used. Toner amount T2 on the photosensitive drum 20 after passing through the contact portion C.
The toner amount sensors 40, 41, and 42 for detecting the above are arranged, and the contact pressure between the intermediate developing roller 15 and the photoconductor drum 20 is adjusted based on the signals of these toner amount sensors 40, 41, and 42.

As a simple control example of the fourth embodiment,
First, the value of the toner amount T1 is detected, and then the values of the toner amounts T2 and T3 when the entire surface maximum density image is formed are detected.
The contact pressure is adjusted so that T3 and T2 = 0. This is because when the contact pressure of the contact portion C is too high, the toner layer 1
Since 6 is narrowed, T1> T2 + T3, and when the contact pressure of the contact portion C is too low, the developing effect decreases, so that T1> T3 and T2 ≠ 0. The contact pressure is adjusted.

Although not shown in this embodiment, the intermediate developing roll 15 is provided with an air cylinder for the photosensitive drum 20.
The air pressure is controlled by the signals from the sensors 40, 41 and 42, so that the contact pressure between the photoconductor drum 20 and the intermediate developing means 15 is adjusted to an appropriate pressure as described above. It is designed to be adjusted stably over time. It should be noted that the use of the air cylinder is, of course, only one example and is not limited to this.

By doing so, an appropriate contact pressure between the photosensitive drum 20 and the intermediate developing means 15 can be stably realized,
It is possible to realize stable image formation.

Further, in this embodiment, the bias voltage applied to the developing electrode 27 of the liquid developing means 14 is finely adjusted according to the value of the toner amount T1 to finely control the toner amount to be developed on the intermediate developing roll 15. Is configured to do.

Various sensors can be used as the sensor for detecting the toner amount. In this embodiment, a sensor for detecting the toner amount by utilizing the light reflection intensity is used.

[0103]

According to the wet developing apparatus of the first aspect of the present invention, a predetermined amount of liquid developer is semi-distributed on the intermediate developer carrier. Since the electrostatic latent image is carried in a fixed state and the electrostatic latent image is contact-developed by the semi-fixed developer at the contact portion between the intermediate developer carrying body and the electrostatic latent image carrying body, density unevenness or background fog is caused. It is possible to form a high-definition image without a high speed.

According to the wet type developing device of the second aspect of the present invention, the relationship between the developing potential contrast and the supplied toner amount is devised as described above,
In particular, it is possible to remove the density unevenness due to the potential unevenness of the electrostatic latent image in the binary image.

Further, according to the wet developing device of the third aspect of the present invention, the toner layer thickness adjusting means is provided on the periphery of the intermediate developer carrying member to tighten the toner layer on the intermediate developer carrying member. With this configuration, the toner layer is less likely to be disturbed by the contact portion with the electrostatic latent image carrier, and stable image formation can be realized.

Further, according to the wet developing device of the fourth aspect of the present invention, the contact pressure between the electrostatic latent image carrier and the intermediate developer carrier can be adjusted based on the signal from the toner amount detection sensor. Therefore, an appropriate contact pressure can be stably realized, and stable image formation can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an image forming apparatus to which a wet developing device according to the present invention is applied.

FIG. 2 is an enlarged configuration diagram showing a contact portion between an electrostatic latent image carrier and an intermediate developer carrier.

FIG. 3 is a block diagram showing an embodiment of an image forming apparatus to which the wet developing device according to the present invention is applied.

FIG. 4 is a configuration diagram showing a first developing section of a wet developing apparatus according to an embodiment of the present invention.

FIG. 5 is an enlarged configuration diagram showing a contact portion between a photosensitive drum and an intermediate developing roller.

FIG. 6 is a graph showing a developing potential according to an embodiment of the present invention.

FIG. 7 is a graph showing the potential of the wet developing apparatus according to the second embodiment of the present invention.

FIG. 8 is a graph showing the potential of the wet type developing device according to the second embodiment of the present invention.

FIG. 9 is a graph showing the potential of the wet type developing device according to the second embodiment of the present invention.

FIG. 10 is a block diagram showing a wet developing device according to a third embodiment of the present invention.

FIG. 11 is a configuration diagram showing a wet developing device according to a fourth embodiment of the present invention.

FIG. 12 is a configuration diagram showing a conventional wet recording apparatus.

FIG. 13 is an enlarged configuration diagram showing the developing unit in FIG.

FIG. 14 is a block diagram showing another conventional wet developing device.

[Explanation of symbols]

1 electrostatic latent image carrier, 2 intermediate developer carrier, 3 liquid developing means, 4 developing electrode.

Claims (4)

[Claims] 1. A wet developing apparatus for forming a visible image by developing an electrostatic latent image formed on an electrostatic latent image bearing member with a liquid developer in which toner is dispersed in a carrier liquid. An intermediate developer carrier which is arranged so as to be in contact with the electrostatic latent image carrier and is capable of applying a predetermined developing bias voltage, and uniformly develops by using a liquid developer on the intermediate developer carrier. Wet developing means, and the first developing is performed by the wet developing means to uniformly carry a predetermined amount of the toner layer and the carrier liquid on the intermediate developer carrier using the liquid developer. Second development for developing the electrostatic latent image formed on the electrostatic latent image carrier is performed by using the toner layer and the intermediate developer carrier on which the carrier liquid is uniformly carried. Wet developing device. 2. The wet developing apparatus according to claim 1, wherein an image portion potential of the electrostatic latent image formed on the electrostatic latent image carrier and a developing bias voltage applied to the intermediate developer carrier. Has a potential contrast greater than that required to develop a toner amount that achieves a desired maximum density of the final recorded image, and a predetermined amount developed on the intermediate developer carrier by the wet developing means. A wet developing device, wherein the toner amount is set to the minimum toner amount required to achieve a desired maximum density of the final recorded image. 3. The wet developing device according to claim 1, wherein the intermediate developer carrier is provided on the periphery of the intermediate developer carrier and after the wet developing means. A wet developing device characterized in that a toner layer thickness adjusting means having at least a roll member which is rotated in the same direction at the same peripheral speed and to which a bias voltage can be applied is arranged. 4. The wet developing device according to claim 1, wherein the amount of toner developed on the intermediate developer carrier, the electrostatic latent image carrier, and the intermediate developer. At least one of the amount of toner on the intermediate developer carrier after passing through the contact portion with the carrier and the amount of toner on the electrostatic latent image carrier after passing through the contact portion is detected. A wet developing device comprising a toner amount sensor, and adjusting the contact pressure between the intermediate developer bearing member and the electrostatic latent image bearing member based on a signal from the toner amount sensor.