JPH10312113A - Wet-type image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image of good quality by uniformizing a layer of high- concentration liquid developer spread over a developer carrier. SOLUTION: A layer of liquid developer 56 formed by spreading liquid developer 56 over the surface of a developing belt 51 by a group of liquid-developer application rollers 57 is pressed with a fixed force by means of a developer press roller 60, thereby smoothing the surface of it. The layer of toner-having liquid developer whose surface has been smoothed is carried to a developing area, and an electrostatic latent image formed on a photoreceptive drum 1 is rendered visible, and thus a density-irregularity-free, uniform toner-image of good quality is formed on the photoreceptive drum 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for visualizing an electrostatic latent image formed by an electrophotographic system, electrostatic recording, an ion flow method or the like by using a liquid developer, and more particularly, to a uniform developing method. It is about the conversion.

[0002]

2. Description of the Related Art An image forming apparatus for visualizing an electrostatic latent image using a high-viscosity, high-concentration liquid developer is disclosed in, for example, Japanese Patent Application Laid-Open No.
No. 209922 and JP-A-7-239615. In this image forming apparatus, as shown in FIG. 6, the photosensitive drum 1 is uniformly positively charged by the charging roller 2 and then the pre-wet liquid reservoir 31 of the pre-wet liquid applying means 3
A pre-wet liquid 32 such as dimethylpolysiloxane oil or the like having a releasability and a chemical inertness stored in the photosensitive drum 1 is applied to the photoreceptor drum 1 by a pre-wet liquid application roller group 33 on the photosensitive drum 1. The photosensitive drum 1 coated with a uniform thickness and coated with the pre-wet liquid 32 is exposed to writing light 4 to form an electrostatic latent image. When this electrostatic latent image is formed, the portion of the surface of the photosensitive drum 1 that has been exposed to light loses its charge, and the portion of the surface that has not been exposed to light remains as an electrostatic latent image. This electrostatic latent image is visualized by the developing means 5.

The developing means 5 is a high-viscosity liquid developer in which toner, which is visualized particles, is dispersed at a high concentration in a developer solvent made of an insulating liquid such as dimethylpolysiloxane oil. A liquid developer 56 in a developer reservoir 55 is applied to a developing belt 51 wound around a plurality of rotating rollers 52, 53, 54 by a developer applying roller group 57 to visualize the image. To form a thin layer of the liquid developer 56. A potential between the minimum value and the maximum value of the latent image potential on the photosensitive drum 1 is applied to the developing belt 51 by bias applying means (not shown). The surface moving speed of the developing belt 51 is set to be equal to the surface moving speed of the photosensitive drum 1 so that a normal image is formed in the developing area. When the thin layer of the liquid developer on the developing belt 51 passes through the developing region in the vicinity of the photosensitive drum 1, in a region where the bias potential of the developing belt 51 is higher than the potential of the electrostatic latent image on the photosensitive drum 1, The toner of the liquid developer thin layer is transferred to the photosensitive drum 1, and in a region where the bias potential is lower than the latent image potential, the toner does not transfer to the photosensitive drum 1 and remains on the developing belt 51. The toner image formed on the photosensitive drum 1 is transferred onto the transfer paper 7 conveyed by the transfer roller 6 to which a bias is applied. The residual toner on the photosensitive drum 1 after the transfer process is removed by the cleaning blade 9 after the residual potential on the photosensitive drum 1 is erased by the quenching lamp 8. The residual toner on the developing belt 51 that has passed through the developing area is removed by the belt cleaning blade 5.
8 removed.

[0004]

In the developing means 5, when a liquid developer thin layer is formed on the developing belt 51, the liquid developer is supplied in the same manner as when a thin film ink is supplied to a plate in an offset printing machine or the like. 56 is a developer application roller group 57
In order to form a uniform liquid developer thin layer on the developing belt 51 with such a developing solution applying roller group 57, several to several tens of rollers are required. I need. As described above, when the number of rollers of the developer application roller group 57 increases, the structure becomes complicated and maintenance is not easy. If the number of rollers is reduced as much as possible in order to simplify the structure of the developer application roller group 57,
Many ribs were formed on the surface of the high-viscosity liquid developer thin layer applied to the developing belt 51, and it was difficult to make the liquid developer thin layer uniform.

Further, the liquid developer has a high viscosity in which toner is dispersed at a high concentration, unlike physical properties of ink of an offset printing machine, and a large number of coating rollers are provided even when an offset printing machine is used. Ribs were formed and it was difficult to make the liquid developer thin layer uniform.

[0006] When the liquid developer thin layer applied to the developing belt is non-uniform, not only the effect of removing the background stain on the photosensitive drum by the pre-wet liquid during development is reduced, but also the image is uniformly developed. A problem that the operation cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages, and has been made in view of the fact that a high-concentration liquid developer applied to a developer carrier can have a uniform developer layer to form a high-quality image. It is an object to obtain an image forming apparatus.

[0008]

SUMMARY OF THE INVENTION A wet image forming apparatus according to the present invention provides a transparent and pre-wet liquid having a dielectric property on an image carrier before visualizing an electrostatic latent image formed on the image carrier. A wet-type image forming apparatus that develops an electrostatic latent image on an image carrier with charged visualized particles contained in a high-concentration liquid developer applied in a thin layer on a developer carrier after development. A high-concentration liquid developer applied in a thin layer on the developer carrier is pressed, and a developer pressing means for smoothing the surface of the visualized particle layer is applied to the developer carrier in a thin layer. It is provided on the downstream side of the developer applying means in the moving direction of the developer carrying member.

It is preferable to provide a particle layer forming means for aggregating the visualized particles in the thinned developer between the developer applying means and the developer pressing means.

It is preferable that the developer press-contact means is a rotary roller close to the surface of the developer carrier. Further, a bias potential for attracting the visualized particles to the surface of the developer carrier may be applied to the developer pressing means.

Further, it is preferable to provide a cleaning means for removing the developer and the solvent adhering to the surface of the rotary roller.

It is desirable to use a charging roller in which the surface of a conductive member is coated with a high electric resistance member as the rotating roller.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing means for visualizing an electrostatic latent image formed on a photoreceptor by an electrophotographic method in the wet image forming apparatus of the present invention is wound around a plurality of rotating rollers and moves on the surface of the photoreceptor. A developing belt that moves in the counterclockwise direction at the same surface moving speed as the speed, and a developer coating roller that applies the liquid developer in the developer reservoir to the developing belt to form a thin layer of the liquid developer on the surface of the developing belt. In addition to a roller group and a belt cleaning blade, it has a corona charger and a developer pressing roller.
The corona charger and the developer pressure roller are the developer application rollers.
The roller group and the developing belt are provided between the developing area adjacent to the photoreceptor, and the developer pressing roller is provided downstream of the corona charger in the moving direction of the developing belt. This developer press roller is made of a conductive member having a surface layer coated with a high-resistance material, for example, an aluminum roller having a surface layer hard-anodized. The surface potential is higher than the surface potential of the developing belt. A high bias potential is applied. A cleaning blade is also attached to the developer pressing roller.

A liquid developer layer formed by applying a liquid developer to the surface of the developing belt with a developing solution applying roller group includes:
Since the toner has a high viscosity in which the toner is dispersed at a high concentration, rib-like irregularities are formed on the surface to make the surface uneven. When the liquid developer layer passes through the position of the corona charger, electric charges are injected from the corona charger, and the toner particles in the liquid developer layer exert a strong cohesive force between the toner particles and the developing belt to act as toner particles. Is aggregated to form a toner layer on the developing belt, and is separated from the floating solvent layer. When the separated toner layer passes through the position of the developer pressing roller, the separated toner layer comes into contact with the developer pressing roller and is pressed with a constant force, so that the surface of the toner layer is smoothed. This surface is smoothed and a toner layer of uniform density is sent to the developing area to visualize the electrostatic latent image formed on the photoreceptor, and a uniform and good quality toner image without density unevenness is formed on the photoreceptor. .

When the surface of the toner layer is smoothed,
Since a bias potential that is higher than the surface potential of the developing belt is applied to the developer pressing roller, it is possible to suppress the toner particles from adhering to the developer pressing roller and to form a uniform toner layer. It can be pressed with force. Further, since the surface layer of the developer pressing roller is formed of a high resistance material, it is possible to prevent an electric leak from occurring between the developer pressing roller and the developing belt. The surface of the toner layer can be stably smoothed.

Further, the solvent layer adhering to the developer pressing roller is removed by a cleaning blade so that the surface of the developer pressing roller is always clean, so that the toner layer is continuously and stably formed. Can be smoothed.

In addition, charges are injected from a corona charger into the liquid developer layer formed on the developing belt, and a strong cohesive force acts between the toner particles in the liquid developer layer and between the toner particles and the developing belt. A toner layer is formed on the developing belt by aggregating the toner particles, so that a toner layer having a uniform density can be formed when pressed by a developer pressure roller, and is of good quality and stable on the photosensitive member. Toned toner image can be formed.

Further, since a bias potential is applied to the developer pressure roller, toner can be aggregated and the surface can be smoothed by the developer pressure roller even if the corona charger is omitted. The configuration of the means can be simplified.

[0019]

FIG. 1 is a block diagram of one embodiment of the present invention.
As shown in the drawing, a charging roller 2, a pre-wet liquid applying unit 3, a developing unit 5, and a transfer roller are disposed along a photosensitive drum 1 rotating clockwise in an image forming / transferring unit of a wet image forming apparatus. 6 and a quenching lamp 8 and a cleaning blade 9. The photoreceptor drum 1 is uniformly positively charged by the charging roller 2 and then is releasably stored in the pre-wet liquid reservoir 31 by the pre-wet liquid applying means 3 and has a chemically inactive liquid having dielectric properties, for example, A pre-wet liquid 32 such as dimethylpolysiloxane oil is applied with a uniform thickness by a pre-wet liquid application roller group 33. The photosensitive drum 1 coated with the pre-wet liquid 32 is exposed to writing light 4 to form an electrostatic latent image. The electrostatic latent image is visualized by the developing means 5 to form a toner image, and the formed toner image is transferred to the transfer paper 7 by the transfer roller 6. The residual toner on the photosensitive drum 1 is removed by the cleaning blade 9 after the residual potential on the photosensitive drum 1 is erased by the quenching lamp 8.

The developing means 5 includes a plurality of rotating rollers 52,5.
Developing belt 51 wound counterclockwise at the same surface moving speed as the surface moving speed of the photosensitive drum 1
And a developing solution reservoir 55, a developing solution application roller group 57 and a belt cleaning blade 58, as well as a corona charger 5
9 and a developer pressing roller 60. Developing belt 51
Denotes a photosensitive drum 1 by bias applying means (not shown).
The potential between the minimum value and the maximum value of the latent image potential is applied. The developer application roller group 57 applies the liquid developer 56 in the developer reservoir 55 to the development belt 51 and
A thin layer of the liquid developer 56 is formed on one surface. The corona charger 59 and the developer pressing roller 60 are provided between the developer application roller group 57 and the developing area where the developing belt 51 is close to the photosensitive drum 1. The developer pressing roller 60 is a corona charger. It is provided downstream of the charger 59 in the moving direction of the developing belt 51. The corona charger 59 injects a positive charge to the developer layer applied on the developing belt 51 by the developer applying roller group 57, and causes toner particles in the developer layer and the toner particles to be in contact with the developing belt 51. The toner particles are aggregated by applying a strong aggregating force between the developing belt 5 and the developing belt 5.
A toner layer is formed on 1. The developer pressing roller 60 presses the toner layer on the developing belt 51, and the surface speed is set to be the same as the moving speed of the developing belt 51. The pressing force of the developer pressing roller 60 against the developing belt 51 is so strong that the developer is not blocked on the upstream side of the contact portion between the developer pressing roller 60 and the developing belt 51. If the pressure is too low, the effect of pressing the toner particles is reduced. On the other hand, if the pressure is too strong, the toner layer cannot pass through the contact portion. This developer pressing roller
La 60 is a conductive member having a surface layer coated with a high-resistance material, for example, an aluminum roller having a surface layer hard-anodized.
A bias potential which is higher than the surface potential of No. 1 is applied. It is preferable that the potential difference between the surface of the developer pressing roller 60 and the surface of the developing belt 51 is so high that no discharge occurs between the regions sandwiched between them. The developer pressing roller 60 is provided with a cleaning blade 61 for removing the developer, mainly the solvent, attached to the surface thereof.

The operation when the thin layer toner particles of the liquid developer 56 applied to the developer application roller group 57 on the developing belt 51 by the developing means 5 configured as described above are aggregated and smoothed. 2 will be described with reference to FIG. The liquid developer layer 21 formed by applying a liquid developer 56 to the surface of the developing belt 51 with a thickness of several μm to several tens μm by a developer coating roller group 57 has toner dispersed at a high concentration. As shown in FIG. 2, ribs and the like are formed on the surface to make the surface non-uniform. This non-uniformity of the surface largely occurs along a direction orthogonal to the moving direction of the developing belt 51. A corona charger 59 is provided on the liquid developer layer 21.
Then, a strong cohesive force is exerted between the toner particles in the liquid developer layer 21 and between the toner particles and the developing belt 51 to aggregate the toner particles to form the toner layer 22 on the developing belt 51. Then, it is separated from the solvent layer 23 that has emerged. Here, the aggregated toner layer 22 is a developer layer having a high toner concentration, and the raised solvent layer 23 is a developer layer having a very low toner concentration. When the separated toner layer 22 passes through the position of the developer pressing roller 60, the toner layer 22 comes into contact with the developer pressing roller 60 and is pressed with a constant force, so that the surface of the toner layer 22 is smoothed. When the surface of the toner layer 22 is smoothed, a bias potential which is higher than the surface potential of the developing belt 51 is applied to the developer pressing roller 60, so that the developer pressing roller 60 Can be suppressed, and the toner layer 22 can be pressed with a uniform force. Thus, the toner layer 22
Since the surface layer of the developer pressing roller 60 for smoothing the surface of the developing roller is made of a high-resistance material, electric leakage occurs between the developer pressing roller 60 and the developing belt 51. Can be prevented, and the surface of the toner layer 22 can be stably smoothed.

The toner layer 22 and the developer pressing roller 6
The solvent layer 23 located between 0 and adheres to the developer pressure roller 60 and is peeled off from the developing belt 51. By removing the solvent layer 23 adhering to the developer pressing roller 60 with the cleaning blade 61, the surface of the developer pressing roller 60 can be always kept clean and continuously stable. Thus, the surface of the toner layer 22 can be smoothed. Further, the solvent layer 23 adhered to the developer pressing roller 60
Is removed by the cleaning blade 61, so that the formation of an extra liquid nip upstream of the contact portion between the developer pressing roller 60 and the developing belt 51 can be suppressed, and the developer pressing roller 60 is removed. The ribs of the toner layer 22 and the solvent layer 23 which are newly generated immediately after passing through the contact portion between the toner layer and the developing belt 51 can be suppressed as much as possible.

As described above, the toner layer 22 having a uniform surface and a uniform density is sent to the developing area, and the electrostatic latent image formed on the photosensitive drum 1 is visualized. Therefore, a uniform and high quality toner image without density unevenness can be formed on the photosensitive drum 1.

In the above embodiment, the case where the cleaning blade 61 is provided on the developer pressing roller 60 has been described. However, even if the cleaning blade 61 is omitted, the same operation as the above embodiment can be obtained. be able to. In this case, FIG.
As shown in FIG. 7, the solvent layer 23 attached to the developer pressing roller 60 becomes a steady state in a state where a layer 23a having a certain thickness is formed on the surface of the developer pressing roller 60, and After passing through the developer pressure roller 60, the solvent layer 23b remains on the developing belt 51 in addition to the toner layer 22, and the surface of the remaining solvent layer 23b is newly formed by the developer pressure roller 60. There is unevenness that has occurred. However, since the surface of the aggregated toner layer 22 is smoothed by the pressing effect of the developer pressing roller 60, the density unevenness of the finally obtained image can be reduced. That is, if the surface of the agglomerated toner layer 22 is not uniform, the surface is not smoothed by a weak pressure at the time of contact with the photoreceptor 1, but the remaining solvent layer 2
This is because 3b is easy to be smoothed when it comes into contact with the photoreceptor 1 even when the surface is non-uniform, and it is hard to cause density unevenness.

Further, even if the corona charger 59 is omitted, the toner in the liquid developer layer 21 is agglomerated to form the toner layer 2.
2 and the solvent layer 23, and the surface of the toner layer 22 can be smoothed. In this case, as shown in the explanatory views of FIGS. 4 and 5, the toner in the liquid developer layer 21 is aggregated by the bias potential applied to the At the position of the roller 60, the toner layer 22 and the solvent layer 23 are separated, and at the same time, the surface of the toner layer 22 is smoothed. In this case, the solvent layer 23 has a corona charger 5
9 is more likely to remain than when the toner layer 9 is provided, however, the toner layer 22 and the solvent layer 2 are
Since the toner layer 22 is pressed into contact with the toner layer 22 at the same time, the toner layer 22 can be reliably smoothed.

[0026]

As described above, according to the present invention, the liquid developer layer formed by applying the liquid developer to the surface of the developing belt by the developer applying roller group is maintained at a constant force by the developer pressing means. To smooth the surface and send the liquid developer layer containing the smoothed toner to the development area to visualize the electrostatic latent image formed on the photoreceptor. An image can be formed on the photoreceptor;

Further, before the surface of the liquid developer layer is smoothed, electric charges are injected into the liquid developer layer by a corona charger so that the toner particles in the liquid developer layer and between the toner particles and the developing belt are strong. A toner layer is formed on the developing belt by aggregating the toner particles by acting on the cohesive force, and the surface of the toner layer is smoothed, so that the toner layer having the smoothed surface can be sent to the developing area, A uniform and high quality toner image without density unevenness can be stably formed on the photosensitive member.

Further, by using a developer pressing roller as a rotating member as the developer pressing means, the toner layer can be pressed with a uniform force, and the toner layer can be made to have a uniform density. And a good quality toner image can be stably formed on the photosensitive member.

When smoothing the surface of this toner layer,
Since a bias potential that is higher than the surface potential of the developing belt is applied to the developer pressing roller, it is possible to suppress the toner particles from adhering to the developer pressing roller and to form a uniform toner layer. It can be pressed with force.

Further, since the surface layer of the developer pressing roller is made of a high resistance material, it is necessary to prevent the occurrence of electric leakage between the developer pressing roller and the developing belt. Thus, the surface of the toner layer can be stably smoothed.

Further, the solvent layer adhering to the developer pressing roller is removed with a cleaning blade so that the surface of the developer pressing roller is always clean, so that the toner layer is continuously and stably formed. Can be smoothed.

Further, since a bias potential is applied to the developer pressure roller, toner aggregation and surface smoothing can be performed by the developer pressure roller even if the corona charger is omitted, and development is performed. The configuration of the means can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the operation of the embodiment.

FIG. 3 is an explanatory diagram showing the operation of the second embodiment.

FIG. 4 is an explanatory diagram showing the operation of the third embodiment.

FIG. 5 is an explanatory diagram showing the operation of the fourth embodiment.

FIG. 6 is a configuration diagram of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging roller 3 pre-wet liquid applying means 5 developing means 6 transfer roller 51 developing belt 55 developing solution reservoir 57 developing solution applying roller group 58 belt cleaning blade 59 corona charger 60 developer pressing roller 61 Cleaning blade

Claims (6)

[Claims] 1. A method for applying a transparent pre-wet liquid having a dielectric property on an image carrier before visualizing the electrostatic latent image formed on the image carrier, and then forming a thin layer on the developer carrier. In a wet image forming apparatus that develops an electrostatic latent image on an image carrier with charged visualized particles contained in a high-concentration liquid developer applied, a high-concentration liquid developer coated in a thin layer on the developer carrier A developer pressing means for pressing the developer to smooth the surface of the visualized particle layer; a developer applying means for applying a high-concentration developer to the developer carrier in a thin layer; A wet type image forming apparatus provided on the side. 2. A wet image forming method according to claim 1, further comprising a particle layer forming means for aggregating the visualized particles in the thinned developer between the developer applying means and the developer pressing means. apparatus. 3. A wet image forming apparatus according to claim 1, wherein said developer pressing means is a rotary roller close to the surface of the developer carrier. 4. A bias potential for attracting the visualized particles to the surface of the developer carrying member is applied to the rotating roller.
The wet image forming apparatus as described in the above. 5. The wet image forming apparatus according to claim 4, wherein said rotary roller is provided with cleaning means for removing a developer and a solvent attached to the surface of said rotary roller. 6. The rotating roller according to claim 4, wherein the rotating roller is a charging roller having a high resistance member coated on the surface of a conductive member.
The wet image forming apparatus as described in the above.