JPH10319725A - Liquid developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable image even for low viscosity developer by reducing the irregular amount of toner in a developer layer supplied to a latent image carrier, resulting from contact pressure when the developer layer on the developer carrier contacts with the latent image carrier. SOLUTION: An aggregating charging member 45 applies charge between toner particles in a developer thin layer on an endless belt 41 with glow discharge or non-pulse corona to aggregate the toner particles. A guide member 46 is put in contact with the back of the endless belt to apply tension, so that a space between the aggregating charging member and the endless belt can be made constant to prevent the irregular aggregation of toner due to the aggregating charging member. A charging roller 20 charges the toner particles aggregated in the developer thin layer, so that a fixed number of toner particles aggregated in the developer thin layer can be transferred to a static latent image on a photosensitive material 10 in a development area to form a toner image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a facsimile machine, a copying machine, a printer, or the like. The electrostatic latent image is visualized by bringing a thin layer of a liquid developer into contact with the surface of the latent image carrier. The present invention relates to a liquid developing device that is being developed, and more particularly to improvement of image quality.

[0002]

2. Description of the Related Art Conventionally, in a liquid developing apparatus using a high-viscosity and high-concentration liquid developer, when a liquid developer layer on a developer carrier comes into contact with a photoconductor as a latent image carrier. Various methods have been proposed for preventing image disturbance due to crushing of the liquid developer layer. For example,
No. 7-209922 discloses that, among the photoconductor and the developer carrier,
A liquid developing method and apparatus have been disclosed in which at least one of the members is made of a flexible member so as to disperse the contact pressure when the liquid developer layer on the developer carrier and the photosensitive member come into contact. Also, JP-A-7-152254, JP-A-7-152
No. 239615 discloses a liquid developing device in which a developer support is constituted by a loose sleeve or an elastic roller to disperse a contact pressure when a liquid developer layer on a developer carrier and a photosensitive member come into contact with each other. Have been.

[0003] When a high-viscosity liquid developer is used, if the developer comes into direct contact with the photoreceptor, it cannot be collected by a cleaning blade, or background contamination occurs in the development process. Therefore, 100mPa.s or more and 10,000Pa.
The above-mentioned JP-A-7-209922 using a high-viscosity developer of s or less, JP-A-7-152254, JP-A-7-239615, in the pre-wet on the photoreceptor surface before the development step, It prevents high viscosity developer from directly contacting the photoreceptor.

[0004]

If the contact pressure between the liquid developer layer on the developer carrying member and the photosensitive member is uneven, the thickness of the developer layer becomes unstable. As a result, the amount of the developer supplied to the photoconductor becomes uneven. Specifically, as the contact pressure increases, the thickness of the developer layer decreases, and the amount of the developer supplied to the photoconductor decreases. This unevenness in the amount of the developer supplied to the photosensitive member is particularly remarkable when the viscosity of the developer is low. Therefore, in order to reduce the unevenness of the developer amount, it is conceivable to increase the toner content of the liquid developer to increase the viscosity. However, when the viscosity of the developer is high, there is a problem that the developer is difficult to be transported.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to use a developer layer on a developer carrier and a latent image carrier for a low-viscosity developer. A stable image can be obtained by reducing the unevenness in the amount of toner in the developer layer supplied to the latent image carrier due to the contact pressure at the time of contact, and a margin for setting the contact pressure To provide a liquid developing device capable of ensuring the above.

[0006]

SUMMARY OF THE INVENTION A liquid developing apparatus according to the present invention forms a thin layer of a high-concentration liquid developer on an endless belt which is a developer carrier, and forms a liquid developer layer on the endless belt. In a liquid developing device that makes an electrostatic latent image visible by bringing the surface of the latent image carrier into contact with the surface of the latent image carrier, the liquid developing device is located upstream of the endless belt in the rotation direction of the developing region where the liquid developer layer and the surface of the latent image carrier come into contact An aggregating charging member for aggregating the toner particles in the liquid developer layer, and a guide member arranged to face the aggregating charging member, wherein the guide member is in contact with the back surface of the endless belt. The distance between the charging member for aggregation and the endless belt is kept constant.

Further, it is preferable that the guide member is formed of a guide roller or a curved guide plate, and the endless belt is curved by abutting the outer peripheral surface of the roller or the curved guide plate against the back surface of the endless belt.

Further, it is preferable that the guide member is formed using a conductive material, and the guide member keeps the potential of the endless belt in contact with the guide member constant.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid developing apparatus according to the present invention is used in an image forming apparatus such as a copying machine, a facsimile machine, or a printer. In order to visualize the image by using a developer, an endless belt as a developer carrier, a developing tank for storing the developer, and a lower portion of the roller are immersed in the developer in the developing tank. With the set up pump roller,
An application roller for thinning the developer pumped from the pumping roller and applying the developer to the endless belt; and an endless belt from a development area where the developer thin layer applied on the endless belt by the application roller and the photoconductor contact. An aggregating charging member disposed opposite to the developer thin layer upstream in the rotation direction, a guide member disposed opposite to the aggregating charging member across the endless belt, and an endless belt stretched together with a plurality of belt rollers to form an endless belt. And a charging roller for charging the belt.

The aggregating charging member is composed of, for example, an electrode disposed apart from the endless belt surface, and generates glow discharge or pulseless corona. Then, by discharging, a charge is applied between the toner particles in the thin developer layer on the endless belt to aggregate the toner particles. The guide member abuts on the back surface of the endless belt to add tension, and to prevent the endless belt from vibrating and bending, thereby maintaining a constant distance between the aggregation charging member and the endless belt, and using the aggregation charging member. Stabilizes discharge and prevents aggregation unevenness of toner caused by the aggregation charging member. The charging roller charges the stably aggregated toner particles in the developer thin layer by the aggregating charging member, so that a certain amount of the aggregated toner in the developer thin layer is formed on the electrostatic latent image on the photoconductor in the developing area. Is transferred to form a toner image.

As described above, by providing the aggregating charging member that generates glow discharge or pulseless corona, the toner particles in the thin developer layer on the endless belt are aggregated, and the aggregating charging member and the endless belt are also aggregated. The guide member that keeps the distance between the toner particles constant stabilizes the discharge by the aggregating charging member and prevents uneven aggregation of the toner particles. Without
A fixed amount of toner agglomerated in the developer thin layer can be supplied to the electrostatic latent image on the photoreceptor, and a stable image can be obtained.

Further, for example, a guide roller or a curved guide plate is used as the guide member, a tension is applied by bringing the outer peripheral surface of the roller or the curved guide plate into contact with the back surface of the endless belt, and the tension member is arranged to face the aggregation charging member. It is good to curve the endless belt which was done. As a result, since the developer thin layer corresponding to the counter electrode is curved when discharged by the charging member for aggregation, the charges are concentrated and released between the toner particles in the curved developer thin layer, and the developer is discharged. The toner in the thin layer can be surely aggregated, and the image can be reliably stabilized.

Further, it is desirable that the guide member is formed using a conductive material, and the guide member is, for example, grounded in order to keep the potential of the endless belt in contact with the guide member constant. In this case, when a charge is applied between the toner particles in the developer thin layer by discharging the aggregation charging member,
The guide member drops the electric charge flowing out through the endless belt to the ground through the contact surface. Thus, it is possible to prevent, for example, the outflow of the charge from hindering the transfer of the toner in the developer thin layer to the electrostatic latent image on the photoconductor and the hindrance to the application of the developer thin layer to the endless belt. it can.

[0014]

FIG. 1 is a configuration diagram showing the configuration of an embodiment of the present invention. As shown in the figure, the liquid developing device 40 is applied to an image forming apparatus 1 such as an electrophotographic copying machine, and the image forming apparatus 1 includes a photoconductor 10 as a latent image carrier and a photoconductor 1
Charging roller 20 arranged along the rotation direction around
, An exposure unit 30, a liquid developing device 40, a transfer roller 50, a cleaning unit 60, and a charge removing unit 70. The charging roller 20 uniformly charges the photoconductor 10 rotated and driven in the direction of the arrow. Exposure unit 3
Numeral 0 denotes an optical system (not shown) which forms an electrostatic latent image on the photoconductor 10 by forming and projecting reflected light from a document. The liquid developing device 40 transfers the thinned liquid developer toner to the electrostatic latent image on the photoconductor 10 in a development area where the liquid developer previously thinned and held and the photoconductor 10 are in contact with each other. To form a toner image. The transfer roller 50 applies the photosensitive member 1 to the transfer paper conveyed in the
The toner image formed at 0 is transferred. Then, the transfer paper 6 onto which the toner image has been transferred is separated from the photoconductor 10 by a separation device (not shown), and is discharged from the device after being subjected to a fixing process by a fixing device (not shown). The cleaning device 60 collects and removes the untransferred toner remaining on the photoconductor 10 after the transfer. The charge removing device 70 removes the charge remaining on the photoconductor 10 in preparation for the next charging.

The liquid developing device 40 rotates in the direction of the arrow at substantially the same speed as the photoconductor 10 in order to develop an electrostatic latent image on the photoconductor 10 using a liquid developer (hereinafter referred to as a developer). Endless belt 41 as a developer carrying member, developing tank 42 for storing developer, and developing tank 4
2, a drawing roller 43 disposed so as to be immersed in the developer, a coating roller 44 for thinning the developer drawn from the drawing roller 43 and applying it to the endless belt 41, The endless belt 41 and the aggregating charging member 45 arranged opposite to the developer thin layer on the upstream side in the rotation direction of the endless belt 41 from the developing area where the thin developer layer applied on the belt 41 and the photoconductor 10 are in contact with each other. A guide member 4 disposed opposite to the aggregation charging member 45
6 and endless belt 41 by first and second belt rollers 41
a and 41b, and a charging roller 41c for charging the endless belt 41.

The aggregating charging member 45 is, for example, an endless belt 4.
It consists of a wire charging member provided with a grit or a metal roller or a metal plate provided with an intermediate resistor on the surface layer, which is disposed at a distance of 50 to 100 μm from one surface, and generates glow discharge or non-pulse corona. By performing such discharge, an electric charge is applied between the toner particles in the developer thin layer applied by the application roller 44, and the electric charges generated between the toner particles aggregate the toner particles by an electric field generated in the gap. This suppresses the toner particles from flowing and scattering in the developer thin layer. The guide member 46 is an endless belt 41
And a tension F is applied to the back surface of the substrate. As a result, as shown in FIG. 3, the flexibility of the endless belt 41 causes the belt 41 to vibrate and bend as shown by a broken line, and thereby the distance from the charging member 45 for aggregation to the surface of the endless belt 41,
That is, the fluctuation of the air gap d can be suppressed, and the distance between the aggregation charging member 45 and the endless belt 41 can be kept constant. Therefore, the aggregation charging member 5 can stably discharge, and by applying a fixed amount of charge between the opposed toner particles in the developer layer, aggregation unevenness of the toner particles can be prevented. And the charging roller 41
c charges the toner particles stably aggregated in the developer thin layer by the aggregation charging member 45, so that the electrostatic latent image on the photoreceptor 10 in the developing region shown in FIG. A certain amount of toner particles aggregated therein are transferred to form a toner image free from image disorder and density unevenness due to fluctuations in the contact pressure between the thin developer layer 5 and the photoconductor 10.

As described above, by providing the aggregating charging member 45 for generating glow discharge or pulseless corona, the toner particles in the thin developer layer on the endless belt 41 are aggregated,
Further, by providing a guide member 46 for maintaining a constant distance between the aggregation charging member 45 and the endless belt 41, the discharge by the aggregation charging member 45 is stabilized to prevent aggregation unevenness of the toner particles. A certain amount of toner aggregated in the thin developer layer can be supplied to the electrostatic latent image on the photoconductor 10 without being affected by the uneven contact pressure between the layer and the photoconductor 10, and a stable image can be obtained. be able to. Further, even with a low-viscosity developer, a stable image can be obtained without unevenness in the amount of toner supplied to the photoconductor 10. Furthermore, even when the contact pressure is high, the amount of toner supplied to the photoreceptor 10 is less likely to be uneven, so that a margin for setting the contact pressure can be secured.

Further, in the above description, the guide member 46 that abuts on the back surface of the endless belt 41 to apply the tension F has been described, but the guide member 46 may be, for example, a guide roller 46a shown in FIG. ), The tension F is applied by abutting the outer surface of the roller 46a or the curved guide plate 46b on the back surface of the endless belt 41, and the endless belt 41 facing the charging member 45 for aggregation is used. It is good to bend. In this case, since the developer thin layer corresponding to the counter electrode of the aggregation charging member 45 is curved, the electric charge is generated between the toner particles in the curved developer thin layer when discharged by the aggregation charging member 45. Can be released in a concentrated manner. Therefore, the toner in the thin developer layer on the endless belt 41 can be surely aggregated.

As described above, the guide roller 46a or the curved guide plate 46b is provided as the guide member 46 which abuts on the back surface of the endless belt 41 and applies the tension F, and the endless belt 41 facing the charging member 45 for aggregation is bent. By doing so, when the discharge is performed by the aggregating charging member 45, the charge is concentrated and released to the curved portion of the developer thin layer, so that the toner in the developer thin layer can be surely aggregated, The image can be reliably stabilized.

Further, in the above, the charge is applied between the toner particles in the thin developer layer on the endless belt 41 by the discharge of the charging member 45 for aggregation, but for example, as shown in FIG. When a charge is applied between the toner particles in the developer thin layer by discharging, for example, the charge 5a flowing out through the endless belt 41 causes the toner particles in the developer thin layer charged by the charging roller 41c to become neutral. Photoconductor 1
The repelling force between the endless belt 41 and the endless belt 41 is prevented by inhibiting the transfer of the toner to the electrostatic latent image on the endless belt 41 or charging the toner particles in the developer, for example, by flowing out the electric charge 5a into the coating roller 44 or the like. It is conceivable that it occurs and hinders application. Therefore, as shown in FIG. 6, a guide member 46 formed of a conductive material is connected to, for example, a ground G in order to keep the potential of the endless belt 41 in contact with the guide member 46 constant. Accordingly, when the charge is applied between the toner particles in the thin developer layer by discharging the charging member 45 for aggregation, the guide member 46 transfers the charge 5a flowing out through the endless belt 41 through the contact surface. To the ground G to remove it. By making the guide member 46 sufficiently larger than the electrode of the aggregating charging member 45, the outflowing charges 5a can be reliably grounded.
It is desirable to drop it.

As described above, the guide member 46 is formed by using a conductive material, the potential of the endless belt 41 in contact with the guide member 46 is kept constant, and the aggregating charging member 45 discharges to reduce the developer thinning. When an electric charge is applied between the toner particles in the layer, the electric charge 5a flowing out through the endless belt 41 is removed. It is possible to prevent the transfer of the toner of the layer or the application of the thin developer layer to the endless belt 41 beforehand, thereby further stabilizing the image.

[0022]

As described above, the present invention aggregates toner particles in a thin developer layer on an endless belt by providing an aggregation charging member that generates glow discharge or pulseless corona. By providing a guide member that keeps the distance between the charging member for aggregation and the endless belt constant, the discharge by the charging member for aggregation is stabilized to prevent uneven aggregation of toner particles. A fixed amount of toner aggregated in the thin developer layer can be supplied to the electrostatic latent image on the photoconductor without being affected by the uneven contact pressure, and a stable image can be obtained. Further, even with a low-viscosity developer, a stable image can be obtained without unevenness in the amount of toner supplied to the photoconductor. Furthermore,
Even when the contact pressure is high, unevenness in the amount of toner supplied to the photoconductor is less likely to occur, so that a margin for setting the contact pressure can be secured.

Further, a guide roller or a curved guide plate is provided as a guide member which abuts on the back surface of the endless belt to apply tension, and the endless belt facing the aggregation charging member is curved, so that the aggregation charging member can be used. The electric charge is concentrated and discharged to the curved portion of the developer thin layer when discharged, so that the toner in the developer thin layer can be surely aggregated, and the image can be reliably stabilized. Can be.

Further, the guide member is formed using a conductive material, the potential of the endless belt in contact with the guide member is made constant, and the charging member for aggregating discharges the toner particles in the developer thin layer. When an electric charge is applied in between, the electric charge flowing through the endless belt is removed, so that the discharged electric charge inhibits the transfer of the toner of the developer thin layer to the electrostatic latent image on the photoconductor, for example. In addition, it is possible to prevent the application of the thin developer layer to the endless belt, and to further stabilize the image.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a developing process of the embodiment.

FIG. 3 is a diagram illustrating a state of an endless belt when a guide member is not provided.

FIG. 4 is a configuration diagram illustrating a configuration of a second embodiment.

FIG. 5 is a diagram showing a state of charges flowing out through an endless belt.

FIG. 6 is a configuration diagram illustrating a configuration of a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Photoreceptor 20 Charging roller 30 Exposure unit 40 Liquid developing device 41 Endless belt 42 Developing tank 43 Pumping roller 44 Application roller 45 Aggregation charging member 46 Guide member 50 Transfer roller 60 Cleaning unit 70 Static elimination unit

Claims (3)

[Claims] A thin layer of a high-concentration liquid developer is formed on an endless belt as a developer carrier, and the liquid developer layer on the endless belt is brought into contact with the surface of the latent image carrier to form an electrostatic latent image. In the liquid developing device for visualizing an image, the liquid developer layer is disposed to face the liquid developer layer upstream of the endless belt in the direction of rotation of the endless belt from the developing region where the surface of the latent image carrier is in contact with the liquid developer layer. An aggregating charging member for aggregating the toner particles, and a guide member disposed opposite to the aggregating charging member, wherein the guide member abuts on the back surface of the endless belt to maintain a constant distance between the aggregating charging member and the endless belt. A liquid developing device characterized by holding. 2. The liquid developing device according to claim 1, wherein the guide member comprises a guide roller or a curved guide plate, and an outer peripheral surface of the roller or the curved guide plate abuts against a back surface of the endless belt to curve the endless belt. . 3. The liquid developing apparatus according to claim 1, wherein the guide member is formed using a conductive material, and the guide member keeps the potential of the endless belt in contact with the guide member constant.