JPH09211993A - Developing device using liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make developing speed high, to eliminate the need of squeezing processing, to make high speed development compatible with development with uniform halftone density by forming a liquid toner layer in a state where electrostatically charged toner particles are gathered by impressing electric field, thenmaking it press-contact with a charge carrier and developing an image. SOLUTION: An electric field impressing roller 53 impresses the electric field on liquid developer adhering to the surface of a developing roller 51 so as to form the liquid toner layer in the state where the charged toner particles are gathered. In a state where the liquid toner layer is held, the roller 51 press- contacts with the charge carrier 7 where an electrostatic latent image is formed so as to develop the image. The charged toner particles forming the liquid toner layer are separated in accordance with the direction of the electric field formed between the roller 51 and the charge carrier 7, and the developer image corresponding to the latent image on the charge carrier 7 is formed. By impressing the electric field, a cleaning roller 63 removes the liquid developer 57 remaining on the surface of the roller 51 from the surface of the roller 51.

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 electrophotographic image forming apparatus or the like, and more particularly to a developing device using a liquid developer.

[0002]

2. Description of the Related Art Conventionally, in various printers, copying machines, etc., an electrophotographic process (so-called Carlson process) has been widely adopted as a method for forming an image. In this electrophotographic process, an image is formed on a recording sheet through a charging process → exposure process → developing process → transfer / peeling process. The surface of the charge carrier on which the photosensitive layer is formed is uniformly charged to, for example, a negative charge in the charging step, and is exposed by laser irradiation based on an image signal by a semiconductor laser beam or the like in the next exposure step. An electrostatic latent image is formed on the surface due to the decrease or disappearance of the negative charge of the part.

After the electrostatic latent image is formed on the surface of the charge carrier, the developer is supplied in the developing step, and the developer image is formed on the surface of the area corresponding to the electrostatic latent image. In this developing step, development is performed by a developing device using an electrophoretic developing method using, for example, a liquid developer.

In the developing device (hereinafter referred to as "electrophoretic developing device") 100 using this electrophoretic developing method,
As shown in FIG. 19, with respect to the developer support 102 made of a metal plate holding the liquid developer 101, a developing electric field portion is formed between the electrostatic latent image 103 and the charge carrier 104 having the electrostatic latent image 103 formed on the surface thereof. Develop close to each other to form 105. To the developer support 102, an appropriate voltage is applied to the electrostatic latent image 103 formed on the surface of the charge carrier 104 to prevent background stain.

Charged toner particles 10 in liquid developer 101
6 causes an electrophoretic phenomenon due to the potential difference between the developer support 102 and the electrostatic latent image 103 on the charge carrier 104, and the direction from the developer support 102 to the electrostatic latent image 103 on the charge carrier 104. Move to. That is, the liquid developer 1
The charged toner particles 106 in 01 are attracted to and adhere to the electrostatic latent image on the charge carrier 104 to form a developing toner layer 107. As shown in FIG. 20, the charge carrier 104 is peeled off from the developer support 102 with the charged toner particles 108 in the developing toner layer 107 attached, and the electrostatic latent image 1
A developer image is formed on the surface of the area corresponding to 03.

[0006]

However, in the above-described conventional electrophoretic developing device 100, since the charged toner particles 106 move in the developing electric field portion 105 by electrophoresis, the developing speed is extremely slow and it is suitable for high-speed developing. Didn't. Therefore, conventionally, it is necessary to supply a large amount of the liquid developer 101 to the developing electric field portion 105 or to supply a high concentration liquid developer 101 to the developing electric field portion 105 in order to speed up the development. It was

However, supplying a large amount of the liquid developer 101 to the developing electric field section 105 causes the size of the apparatus to be large, and using the high concentration liquid developer 101 causes the developing toner layer 107 by electrophoresis. Charged toner particles 108
However, there is a problem that extra charged toner particles 109 other than the above attach to the surface of the toner and cause the background stain and the attachment of the extra charged toner particles 109 to the image portion.

Further, in the electrophoretic developing device 100, since an extra liquid developer layer is formed on the charge carrier 104, the squeeze process is required. Conventionally, this squeeze treatment has been performed by an apparatus using an air knife squeeze, a corona squeeze, a reverse roller squeeze, or the like.

Further, in order to obtain an image of uniform halftone density by the electrophoretic developing device 100, in order to eliminate the influence of the flow pattern and unevenness of the liquid developer 101, the liquid developer 101 is developed in a stationary state. It was necessary to devise such as, and it was not compatible with speeding up.

The inventors of the present invention have found that an extra liquid developer layer is not formed on the charge carrier after development in a liquid developing apparatus which does not rely on electrophoresis, and further, even at high speed development, the halftone density is uniform. By earnestly researching an apparatus for obtaining an image having good property and graininess, by forming a liquid toner layer in a state where charged toner particles are gathered on a developer support in advance, and then developing by contacting with a charge carrier. , Found the solution.

Therefore, the present invention provides a developing device and a developing device using a liquid developer that achieves a high developing speed, a squeeze process not required, and a high speed developing and a uniform halftone density development. The present invention is proposed for the purpose of providing an image forming apparatus provided with the image forming apparatus.

[0012]

A developing device using a liquid developer according to the present invention that achieves this object is a liquid in which charged toner particles including at least a colorant and a resin are dispersed in an electrically insulating liquid. A developer containing portion containing the developer, a developing roller on which the liquid developer is evenly attached from the developer containing portion by a supply roller, and an electric field on the liquid developer attached to the surface of the developing roller. By applying an electric field to form a liquid toner layer in which charged toner particles are aggregated, and a liquid developer remaining on the surface of the developing roller by applying an electric field to the developing roller. And a cleaning roller for removing it from the surface.

In the developing device using the liquid developer according to the present invention configured as described above, the electric field applying roller applies an electric field to the liquid developer adhering to the surface of the developing roller to charge the toner particles. To form a liquid toner layer in a state of being collected. Then, the developing roller presses the charge carrier on which the electrostatic latent image is formed to perform development while the liquid toner layer in which the charged toner particles are collected is held. Then, the charged toner particles that have formed the liquid toner layer in which the charged toner particles are aggregated are separated according to the direction of the electric field formed between the developing roller and the charge carrier, and are separated on the charge carrier. To form a developer image corresponding to the latent image. After that, the cleaning roller applies an electric field to the liquid developer remaining on the surface of the developing roller,
The remaining liquid developer is removed from the surface of the developing roller.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. The developing device using the liquid developer according to the present invention is provided in the laser printer 10 as shown in FIGS.

As shown in FIG. 1, the laser printer 10 includes a drum photosensitive member 7, a cleaning mechanism portion 15 arranged in order along the periphery of the drum photosensitive member 7, an image forming process portion 16, and a transfer portion.・ Peeling mechanism 17 and this transfer
The peeling mechanism unit 17 includes a recording sheet supply unit 18 that supplies the recording sheet 25 and a discharge mechanism unit 19 that discharges the recording sheet 25 peeled from the drum photoconductor 7.

The drum photoconductor 7 has a photoconductive layer formed of an organic photoconductor or an inorganic photoconductor on the surface of a conductive substrate, and an arrow S in FIG.
It is driven to rotate in the direction indicated by.

As described above, the cleaning mechanism portion 15 is arranged along the rotation direction of the drum photosensitive member 7 and the image forming process portion 1 is provided.
6 is arranged before. Cleaning mechanism 15
Is composed of a blade 20 for removing the liquid developer 1 adhering to the surface of the drum photoconductor 7, a destaticizing lamp 21 for destaticizing the surface of the drum photoconductor 7 charged in the image forming process, and the like. In this state, the tip of the blade 20 of the drum photoconductor 7 is abutted against the drum photoconductor 7 to remove the liquid developer 1 remaining on the surface of the drum photoconductor 7. To be done.

The drum photoconductor 7 has a cleaning mechanism 1
In FIG. 5, the surface is subjected to the cleaning processing, and is rotationally driven to the image forming process unit 16 to form an image on the surface. The image forming process unit 16 includes a first charger 22.
And a laser exposure unit 23 and a developing device 24 which constitute exposure means.

The first charger 22 is provided in the vicinity of the surface of the drum photosensitive member 7 and is a corona charger that uniformly charges the surface of the drum photosensitive member 7 with negative charges.

The laser exposure unit 23 is operated in response to an image signal sent from a control unit (not shown), and selectively irradiates the surface of the drum photoconductor 7 with laser light through an optical system. The drum photoreceptor 7 removes the charged negative charges on the surface portion exposed by the irradiation of the laser beam, and an electrostatic latent image corresponding to the image signal is formed.

The drum photoconductor 7 is a laser exposure unit 2
After the electrostatic latent image is formed in 3, the developing device 24 is rotationally driven to perform a developing process. The developing device 24 is
As will be described in detail later, the liquid developer 1 is supplied to the surface of the drum photoconductor 7 to form a developer image from the electrostatic latent image. The drum photoconductor 7 is further rotated and the recording sheet 25 is supplied from the recording sheet supply unit 18.

The recording sheet supply unit 18 includes the paper feed cassette 2
The paper feeding mechanism 27, which omits the details of feeding the recording sheets 25 stored from 6 one by one, and the fed recording sheets 2
And a guide roller mechanism 28 that conveys the sheet 5. The recording sheet 25 is brought into close contact with the surface of the drum photoconductor 7 which is further rotated by being guided with a slight pressure applied thereto.

The drum photoconductor 7 has a recording sheet 25 on the surface.
It is driven to rotate in the state where it is in close contact. Therefore, the developer image formed on the surface of the drum photoconductor 7 is transferred to the recording sheet 25.

The recording sheet 2 is formed on the surface of the drum photosensitive member 7.
A transfer / peeling mechanism unit 17 is disposed at a position where 5 is superposed and rotated. The transfer / peeling mechanism unit 17 includes a second charger 29 and a peeling claw 30.

The second charger 29 applies a negative charge having a polarity opposite to the positive charge of the developer image formed on the surface of the drum photoconductor 7 from the non-transfer surface side to the entire surface of the recording sheet 25. It is uniformly charged.

The recording sheet 25 is peeled from the drum photosensitive member 7 and is discharged to the discharging mechanism section 19 along the peeling claw 30. The discharge mechanism unit 19 includes a plurality of conveyor belts 31 and a discharge roller 32 that convey the recording sheet 25, and a fixing device 3 that fixes the developer image on the conveyed recording sheet 25.
4 and a discharge tray 33 for receiving the recording sheet 25 on which the developer image is fixed. The fixing device 34 is composed of, for example, an electric heater, and heat-fixes the developer image by the liquid developer 1 transferred onto the recording sheet 25 to fix it on the recording sheet 25.

After the recording sheet 25 is peeled off, the drum photosensitive member 7 is rotationally driven to the cleaning mechanism section 15. Then, the drum photoconductor 7 is subjected to the charge removal and cleaning processing as described above in the cleaning mechanism section 15 and is rotationally driven again to the image forming process section 16 to perform the next image forming operation. Further, in the laser printer 10 equipped with this belt photosensitive member, the exhaust fan 35
Is provided.

As described above, the laser printer 10 is provided with the developing device 24 using the liquid developer. Hereinafter, the developing device 24 using this liquid developer will be described. In this description, it is assumed that the charged toner particles are positively charged. When the charged toner particles are negatively charged, the same explanation can be made by reversing the applied voltage.

The developing device 24 using this liquid developer is
As shown in FIG. 2, the liquid developer 1 described above, the developing roller 51 pressed against the surface of the drum photosensitive member 7, and the supply roller 5 sequentially arranged along the periphery of the developing roller 51.
4, an electric field applying roller 53, a cleaning roller 63 and the like.

The developing roller 51 has an outer diameter of 32 ± 0.
It is formed in a substantially cylindrical shape with a length of 05 mm. As shown in FIG. 3, the developing roller 51 includes a cored bar 60 formed of a metal conductive material such as aluminum, and the cored bar 60.
And a conductive elastic layer 61 in which an elastic member such as NBR rubber is laminated on the surface thereof, and a developing bias voltage is applied. The hardness of the conductive elastic layer 61 is set to 30 to 100 ° according to JIS · A. The developing roller 51 is shown in FIG.
As indicated by an arrow M therein, the drum photoconductor 7 is rotationally driven in a direction opposite to the rotational direction. Further, the developing roller 51 is
The conductive base 7A is rotationally driven at a linear velocity equal to the linear velocity of the grounded drum photosensitive body 7.

The supply roller 54 is the developing roller 51.
It is in close proximity to the surface of the device with a suitable gap. The supply roller 54 is formed in a substantially cylindrical shape having an outer diameter of 30 mm. The supply roller 54 is made of a metal conductive material such as aluminum, and is applied with a voltage having the same potential as that of the developing roller 51. Supply roller 54
Is rotationally driven in the direction opposite to the rotational direction of the developing roller 51, as indicated by an arrow N in FIG. Further, the supply roller 54 is rotationally driven at a linear velocity equal to the linear velocity of the developing roller 51.

The supply roller 54 supplies the liquid developer 1 onto the developing roller 51 by pre-weighing with a gravure coater. Therefore, the supply roller 54 is provided with a large number of cells, which are recesses of a pyramid type, a lattice type, or a linear type, on the surface. In the supply roller 54, the doctor blade 58 fills the cell space with the liquid developer 1, removes the excess liquid developer 1, and measures.

In addition to the gravure coater, the supply roller 54 is a blade coater for post-weighing the liquid developer 1 already supplied to the developing roller 51 by the blade, and the liquid developer already supplied to the developing roller 51 by the rod. 1
The liquid developer 1 which has already been supplied to the developing roller 51 by the roller, the squeeze coater which post-meters the liquid developer 1, and the liquid developer 1 which has been pre-metered on the supply roller 54.
Alternatively, a reverse roll coater that forms the sheet and rotates the supply roller 54 in the direction opposite to the developing roller 51 may be employed. The supply roller 54 can be rotationally driven in the direction opposite to the direction indicated by the arrow N in FIG.

A developer container 55 is disposed near the lower portion of the supply roller 54. An unused liquid developer 1 is contained in the developer container 55. In the developer container 55, a part of the peripheral surface of the supply roller 54 is the liquid developer 1.
Will be infiltrated into. The developer container 55 is made of a conductive material such as metal, and is applied with a voltage having the same potential as the supply roller 54. Further, one end of a doctor blade 58 is attached to the developer container 55. The other end of the doctor blade 58 is in contact with the supply roller 54 and removes the liquid developer 57 excessively attached to the surface of the supply roller 54. Further, the developer container 55
Is provided with a stirring roller 59 that stirs the liquid developer 1.

As shown in FIG. 2, the electric field applying roller 53 is positioned before the developing roller 51 is rotationally driven and comes into contact with the drum photosensitive member 7. The electric field applying roller 53 is shown in FIG.
As shown in FIG. 3, the meniscus 1A of the liquid developer 1 is pressed against the developing roller 51 so that the nip width is 1 mm, and a gap is formed between the developing roller 51 and the surface of the developing roller 51.
It is fixed so that it can be. Electric field applying roller 53
Is formed into a substantially cylindrical shape having an outer diameter of 14 mm.
The electric field applying roller 53 is made of a conductive material such as metal, and is applied with a positive voltage with respect to the potential of the developing roller 51. The electric field applying roller 53 is rotationally driven in the direction opposite to the rotational direction of the developing roller 51, as indicated by an arrow Q in FIG. Further, the electric field applying roller 53 is rotationally driven at a linear velocity equal to the linear velocity of the developing roller 51.

As shown in FIG. 2, the cleaning roller 63 is positioned after the developing roller 51 is rotationally driven and comes into contact with the drum photosensitive member 7, and is fixed by abutting on the surface of the developing roller 51. Further, the cleaning roller 63 is
The developing roller 51 is made of a conductive material such as metal.
A negative voltage is applied with respect to the potential. The outer diameter of the cleaning roller 63 is smaller than the outer dimension of the developing roller 51. The cleaning roller 63 is shown in FIG.
As indicated by an arrow U therein, the developing roller 51 is rotationally driven in a direction opposite to the rotating direction of the developing roller 51 at a linear velocity equal to the linear velocity of the developing roller 51.

A recovery container 52 is disposed near the lower part of the cleaning roller 63. Collection container 52
One end of a scraper 56 formed of an elastic member is attached to the. The other end of the scraper 56 is brought into contact with the cleaning roller 63 to remove the residual liquid developer 57 adhering to the surface of the cleaning roller 63.

In the developing device 24 using the liquid developer constructed as described above, first, the supply roller 54 is rotationally driven in the direction shown by the arrow N in FIG. The liquid developer 1 is drawn onto and adhered to. Next, as shown in FIG. 2, the supply roller 54 is further rotationally driven so that the excess liquid developer 1 is removed by the doctor blade 58 and weighed, and the liquid developer layer 4 is supplied. Then, the developing roller 51 is rotationally driven in a direction indicated by an arrow M in FIG. 4 along with the rotationally driving the supply roller 54, so that the surface of the developing roller 51 is covered with the liquid developer layer as shown in FIG. 4 is supplied.

At this time, the weight of the liquid developer layer 4 supplied to the developing roller 51 is large in proportion to the weight of the liquid developer layer 4 contained in the cells of the supply roller 54, as shown in FIG. Become. About 50% of the weight of the liquid developer layer 4 contained in the cells of the supply roller 54 is the developing roller 5.
It can be seen that it is supplied to 1. Here, the supply roller 54
The weight of the liquid developer layer 4 included in the cells of No. 2 increases with the depth d of the cells of the supply roller 4. this is,
When the concentration of the liquid developer layer 4 is 20% by weight, the cell depth d of the supply roller 54 is 0.1 mm, 0.2 mm, 0.
It is an experimental result obtained about three kinds of 3 mm.

The weight of the liquid developer layer 4 supplied to the developing roller 51 is, as shown in FIG.
It increases in proportion to the concentration of the liquid developer layer 4 contained in the cell. This is because the cell depth d of the supply roller 54 is 0.
The concentration of the liquid developer layer 4 at 2 mm is 10% by weight,
It is an experimental result obtained about three kinds, 20 weight% and 30 weight%.

Next, as shown in FIG. 4, the electric field applying roller 53 is brought into contact with the surface of the liquid developer layer 4 on the developing roller 51 in this state. At this time, the electric field applying roller 53
Is rotated in a direction indicated by an arrow Q in FIG. 4 along with the developing roller 51 that is rotationally driven, so that the entire surface of the liquid developer layer 4 formed on the developing roller 51 is brought into contact with. .

Further, the electric field applying roller 53 causes an electrophoretic phenomenon by applying an electric field to the charged toner particles 5A in the liquid developer layer 4 according to the potential difference between the electric field applying roller 53 and the developing roller 51. At this time, the charged toner particles 5A in the liquid developer layer 4 are attracted to the developing roller 51 having a lower potential than the electric field applying roller 53, and are positively charged by the electric field applying roller 53 and the developing roller 51.
The charged charged toner particles 5B are, as shown in FIG.
The liquid toner layer 6 is moved to the developing roller 51 and gathered on the developing roller 51 side to form the liquid toner layer 6.

The developing roller 51 having the liquid toner layer 6 formed on its surface is further driven to rotate in the direction indicated by an arrow M in FIG. At this time, the developing roller 51
As shown in FIG. 7, a negative voltage −V _b is applied to the conductive base 7A of the drum photoconductor 7. Drum photoconductor 7
Is brought into contact with the surface of the liquid toner layer 6 on the developing roller 51 in this state. At this time, the liquid toner layer 6 will be described in detail below, but as shown in FIG.
To form a developer image from the electrostatic latent image on the drum photoconductor 7.

The drum photosensitive member 7 is a conductive base 7A.
The photosensitive layer 7B is not limited to the one having the photosensitive layer 7B formed on the surface thereof, but an electrostatic latent image layer may be formed on the surface of the dielectric with, for example, a charging needle.

At this time, when the above-described developing device 70 is implemented as a printer for expressing gradation, the developing device 70 using this liquid developer continuously changes the surface potential of the drum photoconductor 7. Thus, the thickness of the liquid toner layer 6 developed on the drum photoconductor 7 can be continuously changed.

When the above-described developing device 70 is implemented as this binary printer, the liquid toner layer 6 is entirely left on the developing roller 51 side with a margin to form a white portion, or the liquid toner layer 6 is used. All drum photoreceptor 7
It can be developed on the side to create black areas.

After this, the cleaning roller 63 is moved to the position shown in FIG.
In this state, the surface of the liquid developer 57 remaining on the developing roller 51 is brought into contact with the surface of the liquid developer 57, as shown in FIG. At this time, the cleaning roller 63 is driven to rotate in the direction indicated by the arrow U in FIG. 2 along with the developing roller 51 that is driven to rotate, so that the entire surface of the liquid developer 57 remaining on the developing roller 51 is covered. Touched over.

Further, the cleaning roller 63 applies an electric field to the remaining liquid developer 57 according to the potential difference between the cleaning roller 63 and the developing roller 51. At this time, the remaining liquid developer 57 is sucked by the cleaning roller 63 having a lower potential than the developing roller 51, moves to the cleaning roller 63, and adheres thereto.

The remaining liquid developer 57 attached to the surface of the cleaning roller 63 is removed by the scraper 56 as shown in FIG.
It is scraped off from the surface and is collected in the collection container 52.
The liquid developer 57 collected in the collecting container 52 is sent to the developer container 55 and reused after the concentration of the toner particles is controlled by controlling the concentration.

Now, the results of experiments on the relationship between the linear velocities of the electric field applying roller 53 and the developing roller 51 and the charging potential of the electric field applying roller 53 will be described. This experiment is
On the developing roller 51 having an outer diameter of 30 mm, the electric field applying roller 53 having an outer diameter of 14 mm and the nip width of 1 m are arranged.
This is performed by pressing the charged toner particles 5A on the developing roller 51 so that the charged toner particles 5A are in contact with each other. At this time, the electric field applying roller 5
A bias voltage of +360 V is applied to 3.
The charged toner particles 5B on the developing roller 53 are weighed by the gravure coater of the supply roller 54.

In the above experimental results, as shown in FIG. 9, the linear velocity of the electric field applying roller 53 and the developing roller 51 was 200.
Electric field application roller 53 immediately after charging even when the pressure is increased to mm / s
The charging potential due to was constant at a value of 90V. Therefore, the solid content weight of the charged toner particles 5A on the developing roller 51 is 0.19 mg / c, which corresponds to a transmission density of 2.5, regardless of the linear velocities of the electric field applying roller 53 and the developing roller 51.
It can be seen that it was m ² .

On the other hand, it has been confirmed from a charging experiment using a flat plate that the charged toner particles 5A have a charging potential of 70 to 100 V when the solid content weight is 0.19 mg / cm ² . Therefore, in the above experiment, it can be said that the charging potential reaches the saturation point and the charged toner particles 5A on the developing roller 51 are completely charged.

In the above experiment, the nip width between the electric field applying roller 53 and the developing roller 51 is 1 as described above.
mm, the electric field applying roller 53 and the developing roller 5
When the linear velocity of 1 is 200 mm / s, the time during which the electric field is applied to the charged toner particles 5A is 5 ms. The charged toner particles 5A need to be completely separated from the electric charge within this 5 ms.

By the way, as shown in FIG. 10, about 35 times the charging is obtained by the current measurement using the parallel plate electrodes 81 and 82.
I know that it takes ms. This parallel plate electrode 8
The current measurement using Nos. 1 and 82 is performed assuming that the moment when the charged toner particles 5A enter the gap formed between the electric field applying roller 53 and the developing roller 51 is the moment when the switch 83 is turned on. In addition, this current measurement is performed when the current has completely flowed when the formation of the liquid toner layer 6 in which the charged toner particles 5A are charged and collected is completed. Therefore, in this current measurement, as shown in FIG. 11, it was found that it takes about 35 ms from the moment the switch 83 is turned on until the current flows completely. From this, it is considered that the charged toner particles 5A are not sufficiently charged unless the linear velocities of the electric field applying roller 53 and the developing roller 51 are about 28 m / s or less.

However, in practice, in such charging by the electric field applying roller 53, at least the linear velocity of the electric field applying roller 53 and the developing roller 51 is 200 mm / s.
Even if it is (effective charging time 5 ms), it is sufficiently charged. As described above, the reason why the linear velocity can be sufficiently charged even at a relatively high linear velocity of 200 mm / s is that when the electric field applied by the electric field applying roller 53 causes a separation phenomenon between the charged toner particles 5A and the electric charge. Charged toner particles 5A are generated by the rotating operation of the electric field applying roller 53 and the developing roller 51.
If the charge is separated from the electric charge, it takes about 35 ms until the charged toner particles 5A reach the developing roller 51 completely.
It is presumed that it is not necessary to spend time.

As described above, according to the developing device 24 using the liquid developer, the liquid developer 1 is attached to the developing roller 51, and the liquid toner layer 6 is formed by applying the electric field, and then the drum is formed. Since the toner is developed by being pressed against the photoreceptor 7, the charged toner particles 5A are not moved as in the electrophoretic developing device 100, but the liquid toner layer 6 is formed by the direction of the electric field formed in the liquid toner layer 6 with the pressing. The development is performed after being separated, and high-speed development is possible.

Further, a developing device 2 using this liquid developer
No. 4 does not form an extra liquid developer layer 4 on the drum photoconductor 7 because the liquid toner layer 6 is formed on the developing roller 51 and then contacts the drum photoconductor 7 under pressure. Then, the extra liquid developer layer 4 which was necessary
No need for squeeze processing.

Further, in the developing device 24 using this liquid developer, if the liquid toner layer 6 is formed on the developing roller 51, the liquid toner is changed depending on the direction of the electric field formed in the liquid toner layer 6 with the pressure contact. Since the layer 6 is separated and the development is performed, the charged charged toner particles 5B faithfully corresponding to the density of the charges on the drum photoconductor 7 are developed, thereby easily developing a uniform halftone density developer image. Can be obtained.

Further, in the developing device 24 using this liquid developer, since the liquid toner layer 6 is formed on the developing roller 51, the concentration of the charged toner particles 5B charged in the liquid developer 1 to be used. Even if the value is high, there is no problem such as background stain in the conventional electrophoretic developing device 100 and adhesion of extra charged charged toner particles 5B to the image portion,
The use of high concentration liquid developer 1 is enabled.

Therefore, according to the developing device 24 using the liquid developer, the developing speed is high, the squeeze process is not necessary, the uniformity of the halftone density and the graininess can be easily obtained, and further, the high density can be obtained. Since a liquid developer can be used,
A high-definition image of liquid development can be easily realized at high speed with a small developing device.

Further, a developing device 2 using this liquid developer
In No. 4, the electric field applying roller 53 applies an electric field to the liquid developer 1 attached to the surface of the developing roller 51, so that the liquid toner layer 6 in which the charged toner particles 5B are aggregated can be formed at high speed. .

Further, in the developing device 24 using this liquid developer, the developing roller 51 has the conductive elastic layer 61 laminated on the surface of the cored bar 60, so that the drum photosensitive member 7 is uniformly contacted. In contact with each other, the liquid developer 1 is reliably supplied to the drum photoconductor 7.

Further, in the developing device 24 using this liquid developer, the developing roller 51 has the conductive elastic layer 61 laminated on the surface of the core metal 60, and the supply roller 54 measures the liquid developer 1 by the gravure coater. By doing so, the supply roller 54 is brought into uniform contact with the developing roller 51, and the liquid developer 1 is reliably supplied to the developing roller 51.

Further, in the developing device 24 using this liquid developer, the cleaning roller 63 is the developing roller 51.
By applying an electric field to the remaining liquid developer 57, the remaining liquid developer 57 is surely removed from the surface of the developing roller 51, and the developing roller 51 is prevented from being damaged as compared with the scraping with a blade or the like. To be done.

The liquid developing device 24 of this embodiment includes a core metal 60 made of a metal conductive material such as aluminum.
The developing roller 51 is composed of a conductive elastic layer 61 in which an elastic member such as NBR rubber is laminated on the surface of the core metal 60, but as shown in FIG. 12, it is formed of a metal conductive material such as aluminum. Core 60 and a conductive elastic layer 61 in which an elastic member such as HTV rubber is laminated on the surface of the core 60.
The developing roller may be composed of the conductive elastic layer 61 and the conductive surface layer 62 in which an elastic member such as a PTA tube is laminated on the surface of the conductive elastic layer 61.

The liquid developing device 24 of this embodiment is also used.
In addition to the above-described electric field applying roller 53, the charged toner particles 5A in the liquid developer layer 4 may be charged by a corona charger or an electric field applying electrode plate to form the liquid toner layer 6.

Further, the liquid developer device 2 of this embodiment
In addition to the above-described cleaning roller 63, a cleaning roller having a low altitude or an endless belt-shaped cleaning belt may be used as the cleaning roller 4.

The developing device 24 using the liquid developer according to the present invention can be applied not only to the laser printer 10 described above, but also to other image forming apparatuses such as the laser printer 40. As shown in FIG. 13, the laser printer 40 has the same basic configuration as the laser printer 10 described above, but has a configuration in which a belt photoconductor 41 is provided instead of the drum photoconductor 7. It has features. In the following description, the same members as the laser printer 10 described above,
The same components will be denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 13, the laser printer 40 has a belt photosensitive member 7 which is run endlessly by being stretched between a plurality of roller groups 12 to 14, and a traveling path of the belt photosensitive member 7 in order. The cleaning mechanism section 15 provided
An image forming process section 16, a transfer / peeling mechanism section 17,
The transfer / peeling mechanism unit 17 includes a recording sheet supply unit 18 for supplying the recording sheet 25 and a discharge mechanism unit 19 for discharging the recording sheet 25 separated from the belt photoconductor 7.

The belt photosensitive member 7 is, as shown in FIG.
A photosensitive layer 7B made of an organic photoconductor or an inorganic photoconductor is formed on the surface of a conductive substrate 7A, and the start end and the end are joined to form an endless belt. A group of rollers for moving the belt photosensitive member 7 is composed of a plurality of rollers 12 to 14 including a driving roller 13. The belt photosensitive member 7 is stretched around these rollers 12 to 14 to form a substantially right-angled triangular running path, and is driven to run in a direction indicated by an arrow R in FIG. In the image forming process section 16,
The developing device 24 using the liquid developer described above is provided. Here, the theory of development performed using the present developing apparatus will be explained and verification by theory experiment will be performed. First, we will explain the theory.

As shown in FIG. 14, when the development is completed, the thickness of the liquid toner layer 6A remaining on the developer support 2 side is d ₁ , and the developed liquid toner layer 6 on the charge carrier 9 side.
When the thickness of B is d _{2 and} the thickness of the liquid toner layer 6 formed on the developer support 2 before development is d _t , the thickness d _t of the liquid toner layer 6 is _expressed by the following formula (1) ).

D _t = d ₁ + d ₂ (1) When the potential of the liquid toner layer 6A in the thickness direction from the developer support 2 is V ₁ , the potential V ₁ is It is represented by 2).

V ₁ = ρd ₁ ² / 2ε ₀ ε _t (Equation 2) In the above Equation (1), ρ is the charge density of the liquid toner layer 6B, ε ₀ is the dielectric constant of vacuum, and ε _t Is the liquid toner layer 6
The relative permittivity of B, d _1, is the thickness of the liquid toner layer 6B remaining on the developer support 2.

When the toner potential of the liquid toner layer 6B in the thickness direction from the charge carrier 9 is V ₂ , the toner potential V ₂ is represented by the following formula (3).

V ₂ = ρd ₂ ² / 2ε ₀ ε _t + ρd _p d ₂ / ε ₀ ε _t (Equation (3)) where ρ in the above equation (2) is the charge density of the liquid toner layer 6 B, ε ₀ Is the vacuum permittivity, ε _t is the liquid toner layer 6B
Relative permittivity, ε _p is the relative permittivity of the charge carrier 9, and d ₂ is
The thickness of the liquid toner layer 6B remaining on the charge carrier 9, d
_p is the thickness of the photosensitive layer 9B of the charge carrier 9.

The voltage applied to the developer support 2 is {-V
_b }, if the surface potential of the charge carrier 9 is {−V _p },
The total potential of the developer support 2 and the liquid toner layer 6A remaining on the developer support 2 after development is {V ₁ -V _b }, and the charge carrier 9 and the charge carrier 9 after development also remain on the same. The total potential of the liquid toner layer 6A is {−V _p + V ₂ }.

When the developing device 24 described above is implemented as a printer for expressing gradation, the developing device 24 using this liquid developer continuously changes the surface potential of the charge carrier 9 so that the charge carrier 9 is charged. The thickness of the liquid toner layer 6 developed on the body 9 can be varied continuously.

After the development, this is the total potential of the developer support 2 and the liquid toner layer 6A remaining thereon {V ₁ -V
_b } and the total potential {-V _p + V ₂ } of the charge carrier 9 and the liquid toner layer 6B developed on the charge carrier 9 are _expressed by the following formula (4).
In this case, the toner potential V ₁ and the toner potential V ₂ that are equal to each other exist as shown in FIG.

-V _p + V ₂ = V ₁ -V _b (4) The liquid toner layer 6 near the point where the formula (4) is satisfied is the developer supporting layer on the side close to the developer supporting body 2. At the side closer to the charge carrier 9 in the body 2 direction, an attractive force is applied toward the charge carrier 9 respectively. Therefore, the liquid toner layer 6 is separated into the liquid toner layer 6A on the side of the developer support 2 and the liquid toner layer 6B on the side of the charge carrier 9 at the point where the expression (4) is established. The size of separation of the liquid toner layer 6 can be obtained by solving for d ₂ using the equations (1), (2), and (3).

D ₂ = {1 / (d _t / ε _t + d _p / ε _p )} × {(V _p −V _b ) ε ₀ / ρ + d _t ² /2εt}...Equation (5) where: By substituting the obtained value of d ₂ into the equation (1) and obtaining d ₁ , the following equation (3 ′) is obtained.

D ₁ = d _t −d ₂ (3 ') That is, when V ₁ and V ₂ that satisfy the equation (4) exist, d ₁ and d _{2 are each} one by one. Then, the respective values are obtained by the equation (5) and the equation (3 ′). Further, the developing device 24 using this liquid developer is represented by the formula (4)
When it is carried out within the range where is satisfied, the liquid toner layer 6 developed on the charge carrier 9 by continuously changing the surface potential {-Vp} of the charge carrier 9 as is clear from the formula (5).
The thickness d _{2 of} B can be varied continuously. Therefore, the developing device 24 using the liquid developer is suitable for the case where the developing device 24 is used in a range in which the formula (4) is satisfied, and as a printer that expresses gradation as shown in FIG.

When the above-described developing device 24 is implemented as a binary printer, the liquid toner layer 6 is entirely left on the side of the developer support 2 with a margin to form a white portion, or the liquid toner is formed. The entire layer 6 can be developed on the charge carrier 9 side to form a black portion.

This is as shown in FIG. 15 and FIG.
This is a case where {V ₁ -V _b } and {-V _p + V ₂ } are not equal.

First, consider the case where the positively charged liquid toner layer 6 remains entirely on the developer support 2 side as shown in FIG. If the value of V ₁ at this time is V _{1 (t)} , the state of the potential in this case is −V _p > V _{1 (t)} −V _b (V ₂ = 0) (6) Becomes

In the formula (6), the potential on the developer support 2 side {V _{1 (t)} −V _b } is the potential on the charge carrier 9 side {−V _p }.
Means that the liquid toner layer 6 is positively charged.
Hold the state of being attracted toward the developer support 2. As a result, the thickness of the liquid toner layer 6B developed on the charge carrier 9 becomes zero. That is, in the case of the formula (4), d ₁ = d _t and d ₂ = 0 are always satisfied.

Therefore, when the developing device 24 using the liquid developer is used as, for example, a black and white binary printer, the liquid toner layer 6 is entirely supported by the developer under the condition of the expression (6). It can be left on the No. 2 side, and is suitable for the conditions for forming white areas.

Next, consider the case where the positively charged liquid toner layer 6 is entirely developed on the side of the charge carrier 9 as shown in FIG. If the value of V ₂ at this time is V _{2 (t)} , the state of the potential in this case is −V _p + V _{2 (t)} <− V _b (V ₁ = 0) (7) Becomes

Equation (7) is for the positively charged liquid toner layer 6
Are all developed on the charge carrier 9 side, the potential {-V _p + V _{2 (t)} } on the charge carrier 9 side is still lower than the potential {-V _b } on the developer support 2 side. This means that all of the positively charged liquid toner layer 6 is kept attracted to the charge carrier 9 side. As a result, the developer support 2
The thickness of the liquid toner layer 6A remaining on the side becomes zero. That is, in the case of the equation (4), d ₁ = 0 and d ₂ =
_dt .

Therefore, when the developing device 24 using the liquid developer is used as a binary printer, the liquid toner layer 6 is entirely developed on the charge carrier 9 side with a margin under the condition of the expression (7). It is suitable for the conditions when making a black part.

After that, the liquid developer 57 remaining on the electric field applying roller 3 and the developer support 2 is scraped off from the surface of the electric field applying roller 3 by the scraper 56 and collected in the collecting container 54. The recovered liquid developer 1 is reused after the concentration of the toner particles is optimized.

The charge carrier 9 is not limited to the one having the photosensitive layer 9B formed on the surface of the conductive substrate 9A, but an electrostatic latent image layer is formed on the surface of the dielectric by, for example, a charging needle. It may be one.

Next, verification by theoretical experiments will be performed. The liquid developer 1 used in this experiment is CBR-405 manufactured by Dainippon Ink and Chemicals, Inc. in a concentration of 5% (% by weight).
The product was diluted with Exoper Chemical Co., Ltd. product name: Isopar G.

The liquid toner layer 6 was formed as follows. Liquid developer 1 is put between metal electrodes having a gap of 50 μm, and 500 V is applied. The charged toner particles 5B migrate to the negative electrode side, and the liquid toner layer 6 in which the charged toner particles are collected is formed. The surface potential of the toner layer immediately after charging is about 200V. The surface potential of the liquid toner layer 6 decays with time as shown in FIG. 17, but the decay time constant τ until the potential reaches 1 / e of the peak value is about 23 seconds.

Next, a charge carrier is pressed against the liquid toner layer 6 formed between the metal electrodes for development, and a transparent electrode is vapor-deposited instead of the organic photoconductor (hereinafter abbreviated as OPC). The polyethylene terephthalate (hereinafter abbreviated as PET) film having a thickness of 50 μm was used. First, several seconds after the liquid toner layer 6 was formed, the above-mentioned PET, which had been uniformly charged to various electric potentials, was brought into pressure contact with it to perform the development of the present invention. In addition, after the liquid toner layer is formed on the metal electrode supporting the liquid toner layer 6,
A bias voltage of 60 volts is applied.

FIG. 18 shows the transmission density of the liquid toner layer 6B developed on the PET film 6 and the transmission density on the PET film 6 obtained by measurement after the development was performed by changing the charging potential {-V _p } of the PET film 6. the surface potential of the developed liquid toner layer 6B in the {-V _P + V _2}, the surface potential {V ₁ -V of remaining on the developer carrier 2 the liquid toner layer 6A
_b }.

[0096] The surface potential of the developed on the PET film 6 after development liquid toner layer _{6B {-V P + V 2}} , the surface potential of the liquid toner layer 6A remaining on the developer carrier 2 {V ₁ - V _b } is a substantially equal value, and as the charging potential {−V _p } of the PET film 6 increases in the negative direction,
You can see that it is decreasing. Further, it can be seen that the thickness of the liquid toner layer 6B developed on the PET film increases as the charging potential {-V _p } of the PET film increases in the negative direction. From this, this experiment is based on Equation (4)
It can be seen that this is an experiment for confirming that the above holds and that the results verify the equation (5).

In the experimental example, the positive developing device for developing with the charged toner particles 5B having a polarity opposite to that of the electrostatic latent image has been described, but the charged toner particles having the same polarity as the charge polarity of the charge carrier 9 are used. Of course, a reversal developing device which develops a portion where the gap is removed is also possible.

In order to verify the case where the positively charged charged toner particles 5B are developed on the negatively charged charge carrier 9, the expressions (4), (6) and (7) have been used so far. ), The conditional expressions are as follows: V _p + V ₂ = V ₁ + V _b (Equation (4 ′) V _p > V _{1 (t)} + V _b (V ₂ = 0) ... Equation (6 ′) V _p + V _{2 (t)} <V _b (V ₁ = 0) ... Formula (4 ′), Formula (6 ′), Formula (7 ′)
Is not only the positive developing device that develops with the charged toner particles 5B charged with the opposite polarity to the electrostatic latent image, but also the place where the charge is removed using the charged toner particles charged with the same polarity as the charge carrier 9 is charged. The development conditions can be expressed for each reversal developing device that develops.

That is, the formula (4 ') is a general formula representing the conditions under which equilibrium potential separation development occurs, and the formula (6') is such that the liquid toner layer 6 is entirely left on the developer support 2 side. The general formula representing the condition, Formula (7 ′), is a general formula representing the condition that the liquid toner layer 6 is entirely developed on the charge carrier 9 side.

Although the indirect transfer type electrophotographic printer using the photoconductor has been described above with respect to the embodiments of the developing device and the image forming apparatus using the liquid developer of the present invention, the developing device and the image forming apparatus of the present invention are described. Is naturally applied to electrophotographic copying machines, microfilm reader printers, facsimiles and the like.

Of these apparatuses, it is naturally applicable to an image forming apparatus which forms an electrostatic latent image on a charge carrier by an ion flow system or a multi-stylus system without using a photoconductor.

Further, it is naturally applied to a direct type electrostatic plotter or printer in which an electrostatic latent image is formed on a recording medium which is a charge carrier by an ion flow system or a multi-stylus system and the recording medium is directly developed. It

Further, the direct method using a photoconductor is naturally applied to an electrophotographic plate making machine or the like.

In the embodiment of the developing device using the liquid developer, a monochrome printer, that is, a monochrome printer has been described, but the invention is also applicable to a color printer.

[0105]

As described above, according to the developing device using the liquid developer of the present invention, the charged toner particles are collected by applying the electric field while adhering the liquid developer to the developing roller. After the liquid toner layer in the state is formed, the toner is developed by being brought into pressure contact with the charge carrier, so that the charged toner particles are not moved as in the electrophoretic development, but the electric field of the electric field formed in the liquid toner layer is produced together with the pressure contact. The liquid toner layer is separated according to the direction and development is performed, which enables high-speed development.

In the developing device using the liquid developer, since the liquid toner layer in which the charged toner particles are gathered is formed on the developing roller, the liquid toner layer is brought into pressure contact with the charge carrier, so that the excess charge is not formed on the charge carrier. Liquid developer layer is not formed,
The extra squeeze treatment of the liquid developer layer, which was necessary in the conventional electrophoretic development, is unnecessary.

Further, in the developing device using this liquid developer, if the liquid toner layer in which the charged toner particles are collected is formed on the developing roller, it is formed in the liquid toner layer together with the pressure contact. Since the liquid toner layer is separated according to the direction of the electric field for development, the charged toner particles corresponding to the density of the charges on the charge carrier are developed, thereby easily developing the developer with a uniform halftone density. It is possible to obtain an image.

Furthermore, in the developing device using this liquid developer, since the liquid toner layer in which the charged toner particles are collected is formed on the developing roller, the charged toner particles of the liquid developer to be used are Even if the density is high, there is no problem of background stains in the conventional electrophoretic developing device and adhesion of extra charged toner particles to the image area, and it is possible to use a high density liquid developer.

Therefore, according to the developing device using the liquid developer of the present invention, the developing speed is high, the squeeze process is not required, and the uniformity of halftone density and the graininess can be easily obtained. Since a high-concentration liquid developer can be used, a high-definition image of liquid development can be easily realized at high speed with a small developing device.

Further, in the developing device in which the liquid developer is desired to be used, the electric field applying roller applies an electric field to the liquid developer adhering to the surface of the developing roller, so that the charged toner particles are aggregated in the liquid toner layer. Can be formed at high speed.

Further, in the developing device using this liquid developer, the cleaning roller applies an electric field to the liquid developer remaining on the developing roller, whereby the remaining liquid developer is surely removed from the surface of the developing roller. In addition, the developing roller is prevented from being damaged.

[Brief description of drawings]

FIG. 1 is a schematic view showing a laser printer including a developing device using a liquid developer according to the present invention.

FIG. 2 is a schematic view showing a developing device using a liquid developer according to the present invention.

FIG. 3 is a cross-sectional view showing a supply roller that constitutes the developing device.

FIG. 4 is a schematic view shown for explaining a state in which a liquid developer layer is formed on a developing roller by the developing device.

FIG. 5 is a characteristic diagram showing the relationship between the weight of the liquid developer layer contained in the cells of the supply roller and the weight of the liquid developer layer supplied to the developing roller.

FIG. 6 is a characteristic diagram showing the relationship between the concentration of the liquid developer layer and the weight of the liquid developer layer supplied to the developing roller.

FIG. 7 is a schematic diagram showing a state in which a developer image is formed on a drum photoconductor by the developing device.

FIG. 8 is a schematic view showing a state in which a developer image is formed on a drum photoconductor by the developing device.

FIG. 9 is a characteristic diagram showing the relationship between the linear velocities of the electric field applying roller and the developing roller and the charging potential of the electric field applying roller.

FIG. 10 is a configuration diagram showing a measurement circuit used for current measurement.

FIG. 11 is a characteristic diagram showing a current value measured by current measurement.

FIG. 12 is a cross-sectional view showing another supply roller which constitutes the developing device.

FIG. 13 is a schematic view showing another laser printer including the developing device.

FIG. 14 is a schematic diagram for explaining a state in which equilibrium potential separation development occurs.

FIG. 15 is a schematic diagram for explaining a state in which the liquid toner layer is wholly left on the developer support side.

FIG. 16 is a schematic diagram for explaining a state in which the liquid toner layer is entirely developed on the charge carrier side.

FIG. 17 is a characteristic diagram showing the surface potential of toner particles.

FIG. 18 shows the transmission density of the liquid toner layer developed on the PET film obtained by the measurement after development and the surface potential of the liquid toner layer developed on the PET film {−V _p + V
₂ ] and a surface potential {V ₁ -V _b } of the liquid toner layer remaining on the developer support.

FIG. 19 is a schematic view showing a state in which a developer image is formed on a charge carrier by a developing device using a conventional liquid developer.

FIG. 20 is a schematic diagram showing a state in which a developer image is formed on a charge carrier by the developing device using the liquid developer.

[Explanation of symbols]

 1 Liquid Developer 5A Charged Toner Particles 5B Charged Charged Toner Particles 6 Liquid Toner Layer 7 Drum Photoconductor 24 Developing Device Using Liquid Developer 51 Developing Roller 53 Electric Field Applying Roller 54 Supplying Roller 55 Developer Container 57 Remaining Liquid Developer 63 Cleaning roller

Claims (5)

[Claims] 1. A developer container containing a liquid developer in which charged toner particles composed of at least a colorant and a resin are dispersed in an electrically insulating liquid, and a liquid developer is supplied from the developer container. A developing roller uniformly attached to the surface by a roller, and an electric field applying roller that forms a liquid toner layer in which charged toner particles are aggregated by applying an electric field to the liquid developer attached to the surface of the developing roller And a cleaning roller for removing the remaining liquid developer from the surface of the developing roller by applying an electric field to the liquid developer remaining on the surface of the developing roller. A developing device using a liquid developer, characterized in that a developing roller holding a layer is pressed against a charge carrier on which an electrostatic latent image is formed to perform development. . 2. The developing device using the liquid developer according to claim 1, wherein the cleaning roller applies an electric field in a direction in which the liquid developer remaining on the surface of the developing roller is attracted. 3. The developing device using the liquid developer according to claim 1, wherein the cleaning roller is rotationally driven in a direction opposite to the rotational direction of the developing roller. 4. The developing device using the liquid developer according to claim 1, wherein the cleaning roller has a linear velocity equal to that of the developing roller. 5. The liquid developer according to claim 1, wherein the cleaning roller removes the remaining liquid developer from the surface of the developing roller after the development of the charge carrier by the developing roller. Development device.