JPH11344867A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with the adjustment, even if the fluctuation of a unit is present, and to prevent developing defects as a consequence of gradation unevenness of strips shape and deficiency of the liquid to be prevented in a wide range of developing device speed. SOLUTION: This wet system color image forming device is provided, with at least an image carrier 1, a means for forming the electrostatic latent image on a surface of the image carrier, a developing means of the turning system forming the toner image by feeding liquid developer 11 on the electrostatic latent image, and a means for removing the excessive developer on the image carrier after forming the toner image, and transferring means transferring the toner image formed on the surface of the image carrier to the surface of transfer material. In this case, between the image carrier 1 and the developing means, a plate-shaped body 18 is disposed on the developing area inlet side, and between the image carrier 1 and developing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand wet color image forming apparatus, and more particularly, to an on-demand wet color image which can be easily adjusted and can provide a good image in a wide range of developing device speeds. The present invention relates to a forming apparatus.

[0002]

2. Description of the Related Art An electrophotographic method using a liquid developer is used.
Conventionally, an on-demand type image forming method for recording an image on a transfer material generally employs the configuration shown in FIG.
In FIG. 7, the image carrier 1 as a photosensitive drum is rotated in the direction of the arrow in the figure. Around the image carrier 1, a charging device 2, an exposure device 3, a developing device (electrode) 4, a squeezing device 5, a transfer device 6, a cleaning blade 7, and a static eliminator 8 are arranged along the rotation direction of the image carrier 1. Is arranged.

In the process of rotating the image carrier 1, the surface (photosensitive surface) of the image carrier 1 is charged by the charging device 2, and then the surface of the image carrier 1 is exposed by the exposure device 3, and the surface is exposed. An electrostatic latent image 10 is formed. Next, a liquid developer 11 is applied to the surface of the image carrier 1 by a developing device (electrode) 4, and a toner image 12 is formed on the surface based on the electrostatic latent image.
To form The developing device 4 includes a liquid developer 11 in which (+) or (−) charged toner particles are dispersed in an insulating liquid.
Is supplied to the electrostatic latent image on the image carrier 1, and, for example, the (+) toner particles contained in the liquid developer are electrophoresed on the electrostatic latent image 10 and developed.

After the development, the squeezing device 5 removes excess insulating liquid of the toner image formed on the image carrier 1. The transfer material 13 is transported to the image carrier 1 by the transport roller 14, and a charge having a polarity opposite to that of the toner particles of the toner image 12 is applied from the back surface of the transfer material 13 by the transfer device 6, and Transfer material 13 to form toner particles
To transfer the toner image 12 to the transfer material 13. Then, the residual toner particles on the surface of the image carrier 1 are removed by the cleaning blade 7, and the charge remaining on the surface of the image carrier 1 is removed by the charge removing device 8.

However, in such a conventional image forming apparatus, there is a problem that density unevenness occurs depending on a supply liquid amount determined by the speed of the developing apparatus, and a speed range of a stable developing apparatus free from density unevenness is narrow. was there. This will be described with reference to FIGS. As shown in FIG.
In the developing region D, the gap between the image carrier 1 and the developing device 4 gradually narrows until the position P. Therefore, at the entrance 15 of the developing region, a reverse flow of the developer 14 which has been scooped up and supplied by the rotation of the developing device 4 is generated. As a result, as shown in FIG. Ripples 16 occur. FIG.
FIG. 9 is a conceptual diagram when a ripple occurs at a free interface in a conventional image forming apparatus. If the speed of the developing device is high,
This undulation becomes remarkable, and streak-like shading unevenness which is considered to be caused by this is generated.

On the other hand, when the speed of the developing device 4 is low, the amount of the developing solution 14 supplied is insufficient, and as shown in FIG. 4, air bubbles 17 enter the gap portion of the developing area, and the toner is not developed on the image carrier. There is a problem that development failure occurs. FIG. 4 is a conceptual diagram of a conventional image forming apparatus when bubbles enter the gap due to a small amount of developer supplied to the developing unit. To solve this problem, adjust the speed of the developing device to an appropriate value while checking the image quality.
Some action is possible. However, when the developing gap changes due to manufacturing variations of the developing unit, the optimum value of the developing speed changes. Therefore, there is a problem that the speed needs to be adjusted for each product.

[0007]

SUMMARY OF THE INVENTION In view of the above problems, the inventors of the present invention do not need to make adjustments even if there is a variation in units, and have a streak-like density unevenness and a liquid shortage in a wide range of the developing device speed. The present inventors have intensively studied to develop an image forming apparatus capable of effectively preventing development defects and the like caused by the image formation. As a result, the present inventors have made it possible to eliminate the free interface of the developing solution by providing a plate-like body between the image carrier and the developing means on the entrance side of the developing area, and this problem can be solved. Was found to be resolved. The present invention has been completed from such a viewpoint.

[0008]

That is, the present invention provides an image carrier, a means for forming an electrostatic latent image on the surface of the image carrier, and a method for supplying a liquid developer to the electrostatic latent image to form a toner. A rotary developing unit for forming an image, a unit for removing excess liquid developer on the surface of the image carrier after forming the toner image, and a transfer material for transferring the toner image formed on the surface of the image carrier. A wet color image forming apparatus comprising at least transfer means for transferring to the surface of the image carrier, between the image carrier and the developing means,
Another object of the present invention is to provide a wet type color image forming apparatus, wherein a plate-like body is provided on the developing area entrance side. Here, the development area entrance side refers to the front side of the development area with respect to the rotation direction of the image carrier. In other words, the distance between the image carrier and the developing device gradually increases due to the rotation of the image carrier. (gap)
Means the side going to the shortest position. By providing a plate-shaped body on the entrance side of the development area, it is possible to eliminate a free interface formed by a backflow of the supplied developer near the entrance, and to stably supply the liquid developer. It is.

When the apparatus of the present invention is used,
The speed range of the developing device capable of obtaining a stable image without unevenness in density is widened, and image defects due to an increase or decrease in the amount of supply liquid are significantly reduced. In other words, when the speed of the developing device is high, the generation of ripples at the entrance of the development area due to the backflow of the developer is suppressed, and as a result, the occurrence of streak-like unevenness in the image, which is considered to be caused by the ripples, is avoided. it can. On the other hand, when the speed of the developing device is low, it is possible to suppress the occurrence of defective development due to the intrusion of bubbles into the gap portion of the developing area, and to reduce the burden of adjusting the speed for each product due to the change in the developing gap. By using the apparatus of the present invention, it is possible to reduce image defects, to improve the handling efficiency and to reduce the cost. Hereinafter, the present invention,
This will be described in detail.

[0010]

DETAILED DESCRIPTION OF THE INVENTION A wet color image forming apparatus according to the present invention comprises an image carrier, means for forming an electrostatic latent image on the surface of the image carrier, and a liquid developer supplied to the electrostatic latent image. Rotating developing means for forming a toner image by means of an image carrier, means for removing excess liquid developer on the surface of the image carrier after forming the toner image, and the toner formed on the surface of the image carrier. In an image forming apparatus having at least a transfer unit for transferring an image to a surface of a transfer material, a plate-like body for eliminating a free interface of a developer near an entrance of a development region is provided between the image carrier and the development unit. It is provided. In the image forming apparatus of the present invention, as long as each of the above units is provided, other units may be additionally provided. The means for forming an electrostatic latent image on the surface of the image carrier includes, for example, charging the surface of the image carrier to (+) or (-) by a charging device or the like. Means for removing the excess liquid developer on the surface of the image carrier after the formation of the toner image includes, for example, providing a squeezing device after development. As the transfer means for transferring the toner image formed on the surface of the image carrier to the surface of the transfer material, for example, the transfer material is conveyed to the image carrier, and the transfer device has a polarity opposite to that of the toner particles on the transfer material. , The toner particles on the image carrier are attracted to the transfer material, and the toner image is transferred to the transfer material.

Hereinafter, the present invention will be described more specifically with reference to the accompanying drawings (FIGS. 1 and 5). Embodiment An example of the entire configuration of the apparatus of the present invention is shown in FIG.
Such a configuration is mentioned. In FIG. 5, a plate-like body (thin plate) is disposed in the developing unit including the developing device 4 and the image carrier 1 in the present invention, for example, as shown in FIG. First, FIG.
, The image carrier 1 as a photosensitive drum rotates in the direction of the arrow in the figure. Around the image carrier 1, a charging device 2, an exposure device 3, a developing device (electrode) 4, a squeezing device 5, a transfer device 6, a cleaning blade 7, and a static eliminator 8 are arranged along the rotation direction of the image carrier 1. Is arranged. The charging device 2 is connected to a power supply (not shown). Also, the transfer device 6
For example, a corona charger can be used, which is connected to a power supply.

In the process of rotating the image carrier 1, the surface (photosensitive surface) of the image carrier 1 is charged to, for example, (+) by the charging device 2, and then the image carrier 1 is charged by the exposure device 3.
Is exposed to form an electrostatic latent image on this surface in the same manner as in the above-mentioned conventional method. Next, the liquid developer 11 is applied to the surface of the image carrier 1 by the developing device (electrode) 4, and a toner image is formed on this surface based on the electrostatic latent image. The liquid developer 11 is formed by dispersing (+) or (−) charged toner particles in an insulating liquid. Here, for example, the toner particles are charged to (+). Therefore, the developing device 4 supplies the liquid developer 11 to the electrostatic latent image on the image carrier 1 and causes the (+) toner particles contained in the liquid developer to electrophoretically migrate to the electrostatic latent image 10 for development.

Next, after development, the squeeze device 5
Excess insulating liquid of the toner image formed on the image carrier 1 is removed. Then, the transfer material 13 is transported to the image carrier 1 by the transport roller 14, and a charge having a polarity opposite to that of the toner particles of the toner image, for example, a charge of (−) is applied from the back surface of the transfer material 13 by the transfer device 6. Then, the toner particles forming the toner image on the image carrier 1 are attracted to the transfer material 13, and the toner image is transferred to the transfer material 13. Then, the cleaning blade 7
Removes the toner particles remaining on the surface of the image carrier 1, and then removes the electric charge remaining on the surface of the image carrier 1 by the charge removing device 8. As a result, a new image can be formed on the image carrier 1. After passing through the developing area D, the toner adhering to the developing electrode 4 is removed by the scraping device 9.

In the apparatus according to the present embodiment, the developing section including the developing device 4 and the image carrier 1 is arranged, for example, as shown in FIG. In FIG. 1, 1
Reference numeral 8 denotes a plate-like body (for example, a thin plate), which is formed from the upper surface of the adjusting shim 20 installed on the liquid supply pipe 19 and the developing region D
And the thin plate tip 21 is in contact with the image carrier 1 via the liquid film. As shown in FIG. 1, in the developing area D, the gap between the image carrier 1 and the developing device 4 gradually narrows. However, in the present embodiment,
Since the thin plate tip 21 is in contact with the image carrier 1 via the liquid film, the free interface of the developing solution near the developing region entrance 15 is eliminated. That is, the supplied developer flows backward, and the backflow does not cause waving at the free interface of the meniscus formed at the entrance of the developing area. This is the same even if the speed of the developing device is high and the supply amount of the developer per unit time increases.

As described above, in the present embodiment, since the thin plate or the like is provided, the free interface of the developer is eliminated near the entrance of the developing region, and even if the supply amount of the liquid increases, the level of the liquid near the developing region can be reduced. Rippling does not occur, and it is possible to suppress the occurrence of stripe-like uneven shading. In addition, even if there is a change in the gap between the image bearing member and the developing device due to a variation in the product, the structure has a structure in which the entrance of the developing region is sealed, so that air bubbles are less likely to be caught and development defects can be suppressed. . The device according to the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the technical idea of the present invention. Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0016]

Example 1 and Comparative Example 1 Using the apparatus of the present invention shown in FIG. 5, an experiment was conducted by changing the speed of the developing device and examining shading unevenness due to an excessive amount of liquid and a defective developing region due to insufficient amount of liquid. (Example 1).
In order to investigate the effect of the present invention, FIG.
(Comparative Example 1) was performed using the conventional apparatus shown in FIG. FIG. 6 shows the results. In FIG. 6, the developing speed is shown as a parameter on the horizontal axis, and the frequency of occurrence of defects is shown on the vertical axis. In the figure, ○ indicates the frequency of occurrence of shading unevenness in the case of the thin plate of the present embodiment, ● indicates the frequency of development failure when the thin plate of the present embodiment is present, and △ indicates the frequency of occurrence of uneven shading in the conventional apparatus. And ▲ indicate the frequency of occurrence of development failure in the conventional apparatus. From the frequency of occurrence of these inconveniences, the stable region of the developing device speed with the thin plate of the present embodiment is in the range indicated by A in FIG. 6, and the stable region of the developing device speed in the conventional device is B It turned out that it was the range shown by. From the results of FIG. 6, if the apparatus of the present invention with the thin plate attached is used,
It has been found that the stable speed range A of the developing device is significantly larger than the stable speed range B of the conventional device. This eliminates the need for adjusting the speed of the developing device, which is required each time a unit is replaced, and improves image stability and reliability.

[0017]

According to the image forming apparatus of the present invention, no adjustment is required even if there is a variation in units, and development defects due to stripe-like uneven shading and insufficient liquid can be prevented in a wide range of the developing device speed. That is, according to the apparatus of the present invention, the speed range of the developing device capable of obtaining a stable image without density unevenness is widened, and image defects due to an increase or decrease of the supply liquid amount are significantly reduced. When the speed of the developing device is high, generation of ripples at the entrance of the development region due to the backflow of the developer is suppressed, and as a result, generation of stripe-like uneven shading of an image, which is considered to be caused by the ripples, can be avoided. In addition, when the speed of the developing device is low, it is possible to suppress the occurrence of defective development due to the intrusion of air bubbles into the gap portion of the developing region, and to reduce the burden of adjusting the speed for each product due to the change in the developing gap, thereby facilitating easy development. A good image can be obtained. And
By using the apparatus of the present invention, it is possible to improve the handleability and reduce the cost as the number of image defects decreases.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically illustrating a developing unit of an image forming apparatus of the present invention.

FIG. 2 is a configuration diagram schematically illustrating a developing unit of a conventional image forming apparatus.

FIG. 3 is a conceptual diagram when a ripple occurs at a free interface in a conventional image forming apparatus.

FIG. 4 is a conceptual diagram when air bubbles enter a gap in a conventional image forming apparatus.

FIG. 5 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

FIG. 6 is a diagram illustrating a relationship between a developing device speed and a failure occurrence frequency in the embodiment.

FIG. 7 is a schematic configuration diagram illustrating a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charging device 3 Exposure device 4 Developing device 5 Squeeze device 6 Transfer device 7 Cleaning blade 8 Static eliminator 9 Scraping device 10 Electrostatic latent image 11 Liquid developer 12 Toner image 13 Transfer material 14 Transport roller 15 Development area Inlet 16 Rippling 17 Bubbles 18 Thin plate (plate-like body) 19 Liquid supply pipe 20 Shim 21 Thin plate tip D Development area P position

Claims (1)

[Claims] 1. An image carrier, means for forming an electrostatic latent image on the surface of the image carrier, and a rotary developing means for supplying a liquid developer to the electrostatic latent image to form a toner image Means for removing excess liquid developer on the surface of the image carrier after formation of the toner image, and at least transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a transfer material. An image forming apparatus comprising: a wet-type color image forming apparatus, wherein a plate-shaped member is provided between the image bearing member and the developing means on a developing area entrance side.