JPH10301398A - Liquid developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developing device which is capable of reducing the occurrence of a defect in an image such as an image memory and a streaky noise by making the removal of toner remaining after development, stuck on a developing roller more efficient than that in a conventional device, in a liquid developing device for developing a latent image, so as to make it a visible toner image by supplying a liquid developer including the toner to an electrostatic latent image formed on an electrostatic latent image carrier, with a rotationally driven developing roller. SOLUTION: The liquid developing device 4 is for supplying the liquid developer D including the toner to the electrostatic latent image formed on the electrostatic latent image carrier 1 by the rotationally driven developing roller 41 and developing the latent image, to make it the visible toner image. A brush roller 42 is arranged in contact with the developing roller 41, at a position P3 nearer to the downstream side than an electrostatic latent image developing region P1, in the rotational direction a2 of the roller 41. Then, the brush roller 42 is rotationally driven so that in its contact region with the developing roller 41, the moving directions of the outer peripheries of both these rollers are opposite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic liquid developing apparatus used for developing an electrostatic latent image in an image forming apparatus such as an electrophotographic copying machine or a printer.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a printer, a surface of an electrostatic latent image carrier such as a photoconductor is generally charged, and an image is formed in the charged area based on image information. Exposure to form an electrostatic latent image, develop the latent image into a visible toner image, transfer this toner image to a recording material such as paper,
Fix it. What develops the electrostatic latent image into a visible toner image is a developing device.

[0003] The developing device includes a dry developing device and a liquid developing device (wet developing device). The dry developing device includes a developing roller and a developer. As the developer, a colorant (toner) or a toner to which a carrier having magnetism or the like is added is usually used. The dry developing device supplies the toner onto the electrostatic latent image carrier by charging the toner by friction charging or the like and holding the toner on the developing roller facing the electrostatic latent image carrier. The electrostatic latent image is adhered to the electrostatic latent image to form a visible toner image.

The dry toner used in the dry developing device floats in the air when escaping into the surrounding atmosphere, which may harm human health or pollute the surrounding environment. In general, those having a relatively large average particle size of about 10 μm are used. Since the dry toner has such a relatively large toner particle size, the resolution in development is not so high.

On the other hand, a liquid developing device includes a developing roller and a liquid developer. At present, the mainstream liquid developer is a colored fine particle (toner) mainly composed of a coloring agent and a binder resin, a charge controlling agent, It is a dispersion of a stabilizer and the like. It is considered that the charge of the toner is due to the ion adsorption of the charge control agent. The liquid developing device supplies the liquid developer containing the charged toner onto the electrostatic latent image carrier with a developing roller close to the electrostatic latent image carrier, causing the toner to adhere to the electrostatic latent image, The electrostatic latent image is converted into a visible toner image.

The toner used in the liquid developing device can be finely divided because it does not escape into the atmosphere, and a toner having an average particle size in the submicron range can be used. Therefore, the image formed by the liquid developing device is
A high-resolution image can be obtained as compared with an image formed by a dry developing device.

[0007]

However, in the liquid developing device, the toner can be dispersed in the carrier liquid to reduce the particle diameter of the toner, but there are also problems. That is, a part of the liquid developer supplied to the developing area facing the electrostatic latent image carrier by the developing roller is consumed for developing the electrostatic latent image, and the remaining liquid developer is used as a residual developer, and Is returned into the developing device with the rotation of. At this time, the residual toner contained in the residual developer adheres to the developing roller. If the residual toner is left as it is, it is transported to the developing area even during the next development, so that an image defect such as a so-called image memory occurs. Let it. For this reason, the liquid developing device is usually provided with a cleaning device that removes residual toner on the developing roller at a position downstream of the developing region in the rotation direction of the developing roller.

However, the toner in the liquid developer has a small particle size, and the remaining toner corresponding to the non-image portion on the electrostatic latent image carrier that does not require toner adhesion is removed from the electrostatic latent image carrier. Since the electric field toward the developing roller is applied and the developing roller is in contact with the developing roller, such residual toner has a large adhesive force such as van der Waals force and mirror image force, and strongly adheres to the developing roller surface. ing. on the other hand,
The cleaning device includes a cleaning member such as a cleaning blade that simply comes into contact with the developing roller. The toner adhered strongly in this way has a small particle diameter, so that the toner easily slips through the cleaning member and has a streak. It is easy to cause an image defect such as a state image noise.

Further, some conventional liquid developing apparatuses are provided with a high-concentration liquid developer layer forming apparatus for efficiently developing with a liquid developer (a so-called electrodeposition type apparatus). There is. The high-concentration liquid developer layer forming apparatus includes an electrode along a developing roller surface provided at a position upstream of a developing region of an electrostatic latent image formed on the electrostatic latent image carrier in a rotating direction of the developing roller. Contains. A bias voltage that biases the toner floating in the carrier liquid toward the developing roller is applied to this electrode, so that the concentration of the toner in the liquid developer can be increased, and the development efficiency can be improved. it can.

[0010] In such a liquid developing device, the concentration of the toner in the developer that has passed through the developing area is high, and the wiping remaining by the cleaning device becomes remarkable. Accordingly, the present invention provides a liquid developer containing toner by a developing roller that is driven to rotate on an electrostatic latent image formed on an electrostatic latent image carrier,
A liquid developing device that develops the latent image into a visible toner image. The liquid developing device removes residual toner adhered to a developing roller after development more efficiently than a conventional device, and causes image defects such as image memory and streak noise. It is an object of the present invention to provide a liquid developing device that can reduce the amount of liquid.

[0011]

In order to solve the above-mentioned problems, the present invention supplies a liquid developer containing toner by a developing roller which is driven to rotate on an electrostatic latent image formed on an electrostatic latent image carrier. A liquid developing device for developing the latent image into a visible toner image, wherein a brush roller is disposed in contact with the developing roller at a position downstream of the electrostatic latent image developing area in the rotation direction of the developing roller. In addition, the present invention provides a liquid developing device, wherein the brush roller is driven to rotate in a contact area with the developing roller so that the outer peripheral movement directions of the two rollers are opposed to each other.

According to this liquid developing device, the brush roller is arranged in contact with the developing roller at a position downstream of the electrostatic latent image developing area in the rotating direction of the developing roller.
The brush roller is rotationally driven in the contact area with the developing roller so that the outer peripheral movement directions of the two rollers are opposed to each other, so that after development, residual toner that adheres to the developing roller and arrives at the brush roller is The brush roller which is turned so as to be opposed to the moving direction of the residual toner increases the chances of removing the residual toner, so that the residual toner can be removed more smoothly and more reliably than the conventional apparatus. In addition, the rotation of the brush roller also cancels the bias of the bristles, and the brush roller acts on the residual toner on the developing roller as a whole. Can make the toner amount on the developing roller uniform.

The material of the brush bristles constituting the brush roller may be any of an insulating material, a semiconductive material, and a conductive material. In the liquid developing device according to the present invention, in order to efficiently perform the development with the liquid developer, in the rotation direction of the developing roller,
An apparatus for forming a high-concentration liquid developer layer may be provided at a position upstream of the developing area.

In any case, a bias voltage is applied to the brush roller for attracting the toner adhered to the developing roller and arriving at the brush roller from the developing area with the rotation of the roller to the brush roller. A bias applying device can be provided. Thereby, in addition to the effect of mechanically removing the residual toner by the rotation of the brush roller, the effect of applying a bias voltage to the brush roller and sucking the toner to the brush roller is added. Adhered residual toner can be more efficiently removed than in the conventional apparatus.

When a bias voltage is applied to the brush roller, when the developing roller is conductive, the brush bristles are semiconductive so that a leak current does not occur from a local portion of the brush roller to the developing roller. It is desirable to adopt the one of the nature. As a material for the brush bristle, a semi-conductive fiber which can be applied with a bias voltage and has appropriate conductivity so that the bias voltage does not leak can be used. Specifically, but not limited to,
A semiconductive material having a resistance value in the range of 10 ⁵ to 10 ¹⁰ Ω · cm can be exemplified. The fiber materials include rayon, polyamide, acetate, vinylidene, vinylon,
Dispersion of resistance adjusting materials such as carbon black, carbon fiber, metal powder, metal whiskers, metal oxides, and semiconductor materials in resin fibers made of ethylene fluoride, benzoate, polyurethane, polyester, polyethylene, polyvinyl chloride, polypropylene, etc. What was made can be used. In this case, a desired resistance value can be obtained by the amount of dispersion. In the case where a liquid developer containing an organic solvent is used as the developer, among the resin materials described above,
It is preferable to use polyamide, fluorinated ethylene, polyurethane, polyethylene, or polypropylene having good solvent resistance.

Further, the bias applying device can apply a bias voltage obtained by superimposing an AC voltage on a DC bias voltage. The AC voltage is superimposed on the DC bias voltage to oscillate the residual toner after the development, thereby improving the detachment of the toner from the developing roller and the attraction to the brush roller. Thus, the present liquid developing apparatus has an effect of mechanically removing the residual toner by the rotation of the brush roller, an effect of sucking the brush roller by the DC bias voltage, and an AC voltage superimposed on the bias voltage. In addition to the effect of separating the toner from the developing roller and improving the attraction to the brush roller, residual toner adhering to the developing roller after development can be more efficiently removed.
In addition, the present liquid developing apparatus can reduce the occurrence of image defects such as image memory and streak noise as compared with the conventional apparatus.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus provided with an example of a liquid developing device according to the present invention. FIG. 2 is a side view of a main part of the liquid developing device shown in FIG. FIG. 3 is a side view of the liquid developing device shown in FIG. 2 provided with a high-concentration liquid developer layer forming device. 4 and 5 are side views of the liquid developing device shown in FIG. 3 provided with a bias applying device for applying a bias voltage to the brush roller.

The image forming apparatus shown in FIG. 1 includes a photosensitive member 1, a charging charger 2, a print head 3, a liquid developing device 4, a pre-transfer charger 5, a transfer roller 6, a cleaner 7, a fixing roller 8, and the like. Have. In this image forming apparatus, the laser beam emitted from the print head 3
The charged area on the photoconductor 1 uniformly charged by the charging charger 2 is exposed to form an electrostatic latent image corresponding to a document image on the photoconductor based on image data. This electrostatic latent image moves with the rotation of the photoconductor 1 in the a1 direction, is developed by the liquid developer D contained in the liquid developing device 4, and becomes a visible toner image. The surface of the photoconductor 1 holding the visible toner image containing the carrier liquid in the liquid developer D is made visible by the squeeze roller 43 provided in the liquid developing device 4 and the squeezing voltage applied from the power supply PW1 supplied thereto. While holding the toner image on the photoreceptor 1, only the carrier liquid is removed, and further, a sufficient charge is applied to transfer the toner by the pre-transfer charger 5 to which a voltage is applied from the power supply PW6. The process proceeds to the transfer section T. The liquid developing device 4 will be described in more detail later.

The transfer section T is provided with a transfer roller 6 to which a transfer voltage is applied from a power supply PW2 for sucking the visible toner image. The image is transferred onto the recording sheet S. The recording sheet S is supplied from a recording material supply unit (not shown), and is sent to the transfer unit T in synchronization with the toner image on the photoconductor 1 by a pair of timing rollers (not shown). And good transferability is secured over the entire surface of the sheet S. After the transfer of the toner image, the sheet S is conveyed to the fixing roller 8, where the toner image is fixed, and then discharged.

On the other hand, the toner remaining on the photosensitive member 1 without being transferred onto the recording sheet S by the transfer roller 6 is held, and moves to the cleaner 7 as the photosensitive member 1 rotates in the a1 direction. The cleaning roller 71 and the cleaning blade 72 provided on the cleaner 7 remove excess toner remaining on the surface of the photoreceptor 1 and prepare for the next image formation.

Although the squeezing device such as the squeezing roller 43 is integrated into the developing device 4 here, the squeezing device may be provided at a similar position as a separate structure from the developing device. The image forming apparatus shown in FIG. 1 electrostatically transfers the toner image on the photoreceptor 1 to the recording sheet S, and thermally transfers the roller 6 as a heat roller under an appropriate pressure. It may be something. In addition, the charge of the toner contained in the liquid developer is determined by performing regular development or
By changing the nature of the charge control agent depending on whether reversal development is performed, the charge control agent may be charged positively or negatively. The liquid developing device here is employed in an image forming apparatus for directly transferring a toner image on a photoreceptor to a recording sheet. However, the toner image is temporarily transferred to an intermediate transfer member such as an intermediate transfer belt. After that, it may be adopted in an image forming apparatus or the like that performs secondary transfer on a recording sheet.

Next, the liquid developing device 4 will be described in detail with reference to FIG. The liquid developing device 4 shown in FIG. 2 includes a developing roller 41 and a brush roller 42, and a liquid developer D
Contains. Then, a liquid developer D containing toner is supplied to the electrostatic latent image formed on the photoreceptor 1 by a developing roller 41 which is driven to rotate in the a2 direction, and the latent image is developed into a visible toner image. The developing roller 41
In the rotation direction a2, the brush roller 42 is arranged in contact with the developing roller 41 at a position P3 on the downstream side of the electrostatic latent image developing area P1, and the brush roller 42 is
In the contact area P4 with the roller 1, the rollers are rotationally driven in the direction a3 so that the outer peripheral moving directions of the two rollers are opposed to each other.

A developing bias voltage is applied to the developing roller 41 by a power source PW3 so that toner adheres to the electrostatic latent image formed on the photosensitive member 1. The liquid developer D contains a toner and a carrier liquid, and the toner is charged by ion adsorption of a charge control agent dispersed in the carrier. The charged toner is transferred to an electrostatic latent image developing area P1 by a developing roller 41 which rotates with the carrier liquid.
The photosensitive member 1 and the developing roller 41 are further pumped to the upstream position P2, and then move to the electrostatic latent image developing area P1 where the photosensitive member 1 and the developing roller 41 face each other, and adhere to the electrostatic latent image on the photosensitive member 1.

Toner D1 remaining without adhering to the electrostatic latent image
Are attached to the surface of the developing roller 41 and
In the first rotation direction a2, the position shifts to a position P3 on the downstream side of the electrostatic latent image developing area P1 and reaches the brush roller 42.
The residual toner D1 adhering to the developing roller 41 and arriving at the brush roller 42 is rotated in the direction a3 opposite to the moving direction of the residual toner D1.
The chances of being removed by the brush roller 42 increase, so that the remaining toner can be removed more smoothly and more reliably than the conventional device.

The rotation of the brush roller 42 also cancels the bias of the brush bristles 42a, and the brush roller 42 acts on the residual toner D1 on the developing roller 41 as a whole. Can be removed, and the amount of toner on the developing roller 41 at the time of development can be made uniform, and the occurrence of image defects such as image memory and streak noise can be reduced as compared with the conventional apparatus.

The material of the brush bristles 42a constituting the brush roller 42 may be any of an insulating material, a semiconductive material, and a conductive material. Next, another embodiment of the liquid developing device according to the present invention will be sequentially described with reference to FIGS. Liquid developing device 4 shown in FIG.
FIG. 5A shows a configuration in which the liquid developing device 4 shown in FIG. 2 includes a high-concentration liquid developer layer forming device 44 for efficiently developing the liquid developing device.

This high-concentration liquid developer layer forming apparatus 44
In the rotation direction a2 of the developing roller 41, the developing roller 41 is provided at a position P2 upstream of the electrostatic latent image developing area P1.
It includes an electrode 44a along one surface. This electrode 44a
To the developing roller 41, a bias voltage is applied from a power supply PW4 that biases the toner floating in the carrier liquid contained in the developer D to the developing roller 41 side. The toner density can be increased, and the development efficiency can be improved.

After the electrostatic latent image is developed by the high-concentration liquid developer D2 formed by such a device, the toner D1 remaining on the developing roller 41 adheres strongly to the surface of the developing roller 41. However, the brush roller 42 provided in the liquid developing device 4a generates the residual toner D strongly adhered to the surface of the developing roller 41 by the same operation as the brush roller 42 in the liquid developing device 4 shown in FIG.
1 can also be effectively removed.

The liquid developing device 4b shown in FIG. 4 has a configuration in which a bias applying device 45a is provided on the brush roller 42 of the liquid developing device 4a shown in FIG. The bias applying device 45a applies a bias voltage supplied from the power supply PW5 to the brush roller 42. The bias voltage of the bias applying device 45a adheres to the developing roller 41, and transfers the toner D1 arriving from the electrostatic latent image developing area P1 to the brush roller 42 with the rotation of the developing roller 41 in the direction a2 to the brush roller 42. Applied to the brush roller 42 for suction. Thus, the bias voltage supplied from the power source PW5 is applied to the brush roller 42, and the toner D1 is sucked into the brush roller 42, in order to mechanically remove the residual toner D1 by the rotation of the brush roller 42 in the direction a3. The effect is added, and the residual toner D1 adhering to the developing roller 41 after the development can be removed more efficiently than the conventional device.

Since a conductive roller is used for the developing roller 41, a leak current may occur between the brush roller 42 and the developing roller 41. 42b has a resistance of 1
Since a semiconductive material in the range of 0 ⁵ to 10 ¹⁰ Ω · cm is used, it is possible to prevent a leak current from a local portion of the brush roller 42 to the developing roller 41.

As a material of the brush bristles 42b, a semi-conductive fiber that can apply a bias voltage and has appropriate conductivity so that the bias voltage does not leak is used. For example, carbon black, carbon fiber, metal powder, metal whisker, metal A material in which a resistance adjusting material such as an oxide or a semiconductor material is dispersed can be used. In the case where a liquid developer containing an organic solvent is used as the developer, it is preferable to use polyamide, fluorine-containing ethylene, polyurethane, polyethylene, or polypropylene having good solvent resistance among the above resin materials.

Further, the liquid developing device 4c shown in FIG.
A bias applying device 45b is provided instead of the bias applying device 45a provided in the liquid developing device 4b shown in FIG. The bias applying device 45b superimposes an AC voltage supplied from the power supply AC on a DC bias voltage from the power supply PW5 applied to the brush roller 42.

As a result, the residual toner D1 after development is vibrated, so that the separation of the toner D1 from the developing roller 41 and the suction of the toner D1 to the brush roller 42 are improved. The liquid developing device 4c has an effect of mechanically removing the residual toner D1 by the rotation of the brush roller 42 in the direction a3, an effect of sucking the brush roller 42 by the DC bias voltage, and superimposing an AC voltage on the DC bias voltage. As a result, the effect of separating the toner D1 from the developing roller 41 and improving the attraction to the brush roller 42 is added, and the residual toner D1 adhering to the developing roller 41 after the development can be more efficiently removed.

As described above, any of the liquid developing devices 4, 4a, 4a
b and 4c can also efficiently remove the residual toner D1 adhering to the developing roller 41 after development, and can reduce the occurrence of image defects such as image memory and streak noise as compared with the conventional device. . Next, an evaluation experiment was performed on the performance of each of the developing devices shown in FIGS. 2 to 5, which will be described. A comparative experiment was also conducted, and will be described together.

The evaluation experiments were carried out by mounting each of the developing devices according to the present invention shown in FIGS. 2 to 5 on an image forming apparatus of the type shown in FIG. Also, the comparative experiment
The developing devices shown in FIGS. 6 to 9 were mounted on an image forming apparatus of the type shown in FIG. The liquid developing devices 4d and 4e shown in FIGS. 6 and 7 have a position P downstream of the electrostatic latent image developing area P1 in the rotation direction a2 of the developing roller 41.
3, a brush roller 42 is disposed in contact with the developing roller 41, and the brush roller 42 is driven to rotate in the a4 direction in the contact area P4 with the developing roller 41 so that the outer peripheral moving directions of the two rollers are the same. The liquid developing device 4d shown in FIG. 6 includes a high-concentration liquid developer layer forming device 44.
It has.

The liquid developing devices 4f and 4g shown in FIGS.
Is a configuration in which a fixed cleaning member is brought into contact with the developing roller 41 at a position P3 downstream of the electrostatic latent image developing area P1 in the rotation direction a2 of the developing roller 41. The cleaning member is a cleaning blade 46 in the liquid developing device 4f, and is a fixed brush 47 in the liquid developing device 4g.

The experimental conditions are as follows. That is, the photoreceptor 1 is rotated in the a1 direction at a peripheral speed of 50 cm / sec to apply a charge from the charging charger 2 to charge the photoreceptor 1, to keep the surface potential at −600 V, and to develop without exposing. Was. In each of the experiments, the liquid developer was charged with a liquid developer D having a toner concentration of 3% by weight.
And the developing roller 41 is -300 V from the power supply PW3.
, And rotationally driven at a peripheral speed of 75 cm / sec. The distance between the photoconductor 1 and the developing roller 41 in the electrostatic latent image developing area P1 was set to 100 μm.

The developer D used here was a liquid developer in which an IP solvent 1620 (manufactured by Idemitsu Petrochemical Co., Ltd.) was used as a carrier liquid, and a polyester resin toner having an average particle diameter of 2 μm was dispersed in the liquid. It is. FIG.
For liquid developing apparatus having a high concentration liquid developer layer forming device 44 shown in FIG. 6, as will become an amount of toner adhering to the developing roller 41 to 0.8 mg / cm ^2, forming a high concentration liquid developer layer The bias voltage applied to the device 44 and the flow rate of the liquid developer D were adjusted. 4 and 5
Of the developing device, the brush roller 42 has about 10 ⁵ Ωc
m or more semiconductive brush bristles 42b.

In the liquid developing device 4 shown in FIG. 2, an experiment was conducted with the outer peripheral speed of the brush roller 42 being the same as the peripheral speed of the developing roller 41.
In the liquid developing device 4a shown in FIG. 5, the experiment was performed with the outer peripheral speed of the brush roller 42 being the same speed, twice and three times as high as the peripheral speed of the developing roller 41.
The liquid developing device 4 shown in FIG.
b, the outer peripheral speed of the brush roller 42 is
1 and the same speed as the peripheral speed of 1
V and -300 V DC voltage applied are referred to as Experimental Examples 5 and 6, respectively. The outer peripheral speed of the brush roller 42 is set to twice the peripheral speed of the developing roller 41, and An experiment in which a DC voltage of 300 V was applied was used as Experimental Example 7, and the peripheral speed of the brush roller 42 was set to three times the peripheral speed of the developing roller 41 in the liquid developing device 4c shown in FIG. Roller 4
2. DC voltage of -150V and peak TO peak 1k
Experimental example 8 is an experiment in which an AC voltage AC of 1 V and 1 kHz was superimposed and applied.

On the other hand, the liquid developing device 4 shown in FIGS.
As for d and 4e, the experimental results obtained by making the outer peripheral speed of the brush roller 42 twice the peripheral speed of the developing roller 41 are referred to as Comparative Experimental Example 1 and Comparative Experimental Example 2, respectively, and the liquid developing apparatus shown in FIGS. 4f and 4g are referred to as Comparative Experimental Example 3 and Comparative Experimental Example 4, respectively. In such an experimental example and a comparative experimental example, the liquid developing apparatus was continuously operated for one hour. The state of the residual toner on the developing roller immediately after cleaning by the cleaning brush 42,
Further, it was examined whether or not the residual toner spread on the photosensitive member.

In order to check for residual toner adhering to the developing roller and the photoreceptor, the developing roller and the photoreceptor are dried, a transparent tape is adhered to the surfaces thereof, and the toner adhering to the transparent tape together with the transparent tape is peeled off. The transmission density of those transparent tapes was measured. In such an experiment, whether or not toner has adhered to the developing roller or the photoreceptor despite the cleaning of the developing roller is determined by the presence or absence of streak noise during normal image formation, image memory, and background fog. Since it is related to the presence / absence of the occurrence of a streak, etc., evaluation of streak noise and evaluation of dirt and background fog which cause image memory were performed according to the following criteria. The mark “○” indicates that no image defects that pose a practical problem will occur, and the mark “△” indicates that the image defects are within an acceptable range.
“X” marks indicate that unacceptable image defects occur.

Evaluation of streak noise ○ No residual toner on developing roller △ No residual toner on developing roller but on photoreceptor × Residual toner on photoreceptor Evaluation of dirt and background fog ○ Clean on developing roller Densitometer measurement: toner concentration 0.2 on developing roller surface
△) Residual toner is on the developing roller but not on the photoreceptor (measured by densitometer: toner concentration 0.2 on developing roller surface)
(Measured value of densitometer: toner concentration of 0.2 or less on photoconductor surface) × There is residual toner on photoconductor (Measured value of densitometer: toner concentration of 0.2 on photoconductor surface) Each experiment Are summarized in the following table. In addition, (brush roller peripheral speed / developing roller peripheral speed) = θ, and in the contact area of the brush roller with the developing roller, the rotation direction in which the outer peripheral movement directions of both rollers are opposite to each other is C, and the brush roller has the same direction Is the rotation direction F.

High-concentration liquid Implementation Brush / Development Brush-row Streaks Soil, ground Developer layer Form Roller peripheral speed ratio By-noise skin fogging device Figure (Rotation direction) Asbestos application Evaluation Evaluation Example 1 None Figure 2 θ = 1 (C) No ○ ○ Experimental Example 2 Yes Figure 3 θ = 1 (C) No ○ △ Experimental Example 3 Yes Figure 3 θ = 2 (C) No ○ ○ Experimental Example 4 Yes Figure 3 θ = 3 (C) No ○ ○ Experimental Example 5 Yes Figure 4 θ = 1 (C) -150V ○ ○ Experimental Example 6 Yes Figure 4 θ = 1 (C) -300V ○ ○ Experimental Example 7 Yes Figure 4 θ = 2 (C) -300V ○ ○ Experimental example 8 Yes Fig. 5 θ = 3 (C) -150V ○ ○ (AC voltage with peak TO peak 1kV: 1kHz superimposed on DC bias application voltage to brush roller) Comparative experimental example 1 Yes Fig. 6 θ = 2 ( F) None △ × Comparative Example 2 None Figure 7 θ = 2 (F None ○ × Comparative Example 3 None Figure 8-None × × Comparative Example 4 None Figure 9-None × × As a result, all of Comparative Example 1 to Comparative Example 4 to which the present invention was not applied were stained. In the background fog evaluation, residual toner may be present on the photoreceptor, which may cause image defects such as an image memory.

In Comparative Experimental Example 1 and Comparative Experimental Example 2, in addition to the possibility that toner adheres to the photoreceptor 1 and cause image defects such as fog, the brush roller 42 and the developing roller 41 Since the outer peripheral movement directions are the same in the contact area, the brush roller 42 and the developing roller 41
The toner tends to enter the gap between the developing roller 41 and the toner, so that the toner tends to adhere to the film on the developing roller 41 (a so-called filming phenomenon). In Comparative Experimental Example 3, the cleaning performance of the residual toner adhered to the developing roller 41 by the blade 46 provided is not sufficient, and there is a strong possibility that image defects such as streak noise may occur. In Comparative Example 4, the removal of the residual toner adhering to the developing roller 41 is not stabilized due to the bias of the brush bristles of the fixed brush 47, and image defects such as streak noise may occur.

On the other hand, in Experimental Examples 1 to 8 using the respective developing devices according to the present invention, the amount of residual toner is reduced in all the devices due to the above-described operation. It was possible to reduce the occurrence of image defects such as shape noise.

[0046]

According to the present invention, a liquid developer containing toner is supplied to a latent image formed on an electrostatic latent image carrier by a developing roller which is driven to rotate, and the latent image is made visible toner. A liquid developing device for developing an image, which is capable of efficiently removing residual toner adhered to a developing roller after development as compared with a conventional device and reducing the occurrence of image defects such as image memory and streak noise. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus provided with an example of a liquid developing device according to the present invention.

FIG. 2 is a side view of a main part of the liquid developing device shown in FIG.

FIG. 3 is a side view of a developing device in which a high-concentration liquid developer layer forming device is provided in the liquid developing device shown in FIG. 2;

FIG. 4 is a side view of the developing device in which a bias applying device for applying a voltage to a brush roller is provided in the liquid developing device shown in FIG. 3;

FIG. 5 is a side view of the developing device in which the bias applying device shown in FIG. 4 applies a bias voltage obtained by superimposing an AC voltage on a DC bias voltage.

FIG. 6 is a sectional view of a main part of a liquid developing device used in a comparative experiment example.

FIG. 7 is a cross-sectional view of a main part of another liquid developing device used in a comparative experimental example.

FIG. 8 is a cross-sectional view of a main part of still another liquid developing device used in a comparative experimental example.

FIG. 9 is a cross-sectional view of a main part of still another liquid developing device used in a comparative experimental example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Laser printer head 4, 4a, 4b, 4c, 4d, 4e, 4f, 4g Liquid developing device 41 Developing roller 42 Brush roller 42a Brush bristle 42b Semiconductive brush bristle 43 Squeeze roller 44 High density Liquid developer layer forming device 44a Electrode 45a, 45b Bias applying device 46 Cleaning blade 47 Cleaning fixed brush D Liquid developer D1 Residual toner D2 High concentration liquid developer P1 Electrostatic latent image developing area P2 Electrostatic latent in developing roller rotation direction Position upstream of the image development area P3 Position downstream of the electrostatic latent image development area in the rotation direction of the development roller P4 Contact area between the brush roller and the development roller 5 Pre-transfer charger 6 Transfer roller 7 Cleaner 71 Cleaning roller 72 Cleaning blade 8 Fixing Laura S Recording sheet T Transfer unit PW1, PW2, PW3, PW4, PW5, PW6, A
C power supply

Continued on the front page (72) Inventor Toshimitsu Fujiwara 2-3-113 Azuchicho, Chuo-ku, Osaka Osaka International Building Minolta Co., Ltd. (72) Inventor Masaharu Kanazawa 2-3-13 Azuchicho, Chuo-ku, Osaka Osaka Inside the International Building Minolta Co., Ltd. (72) The inventor Shuji Iino 2-3-1-13 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd.

Claims (4)

[Claims] A liquid for developing a latent image into a visible toner image by supplying a liquid developer containing toner by a developing roller that is driven to rotate to the electrostatic latent image formed on the electrostatic latent image carrier. A developing device, wherein a brush roller is arranged in contact with the developing roller at a position downstream of the electrostatic latent image developing area in the rotation direction of the developing roller, and the brush roller is in a contact area with the developing roller. A liquid developing device which is driven to rotate so that the outer peripheral movement directions of the two rollers are opposed to each other. 2. The liquid developing device according to claim 1, further comprising a high-concentration liquid developer layer forming device at a position upstream of the developing region in a rotation direction of the developing roller. 3. A bias application for applying a bias voltage to the brush roller for attracting the toner adhering to the developing roller and arriving at the brush roller from the developing area with the rotation of the roller to the brush roller. 3. The liquid developing device according to claim 1, further comprising an apparatus. 4. The liquid developing device according to claim 3, wherein said bias applying device applies a bias voltage obtained by superimposing an AC voltage on a DC bias voltage.