JP2005292859A - Electrophotographic apparatus of liquid toner developing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent continuous formation of mottled patterns produced by developing, reducing the occurrence of the mottled patterns and to supply liquid toner to a surface of a developing roller flatly and uniformly while raising the rate of transferring. <P>SOLUTION: High viscosity liquid toner is used as liquid developer, a photoreceptor drum 10 forming an electrostatic latent image, a developing roller 22 coming into contact with the photoreceptor drum 10 and supplying the liquid toner and a gravure roller 24 are provided. The gravure roller 24 is provided with numerous fine indentions on its surface, quantity restriction of the supplied liquid toner is carried out by the numerous fine indentions and the liquid toner is applied to the developing roller 22, bias potential is applied to the developing roller and the rate of transferring is raised for the supplied liquid toner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic apparatus of a liquid toner developing system using a high viscosity liquid toner, and more particularly to an electrophotographic apparatus of a liquid toner developing system that forms a uniform toner layer on a developing roller.

  2. Description of the Related Art Conventionally, a liquid toner developing type electrophotographic apparatus using a high viscosity liquid toner in which solid particles such as a pigment are dispersed in a liquid carrier (oil) as a liquid developer is known (for example, Patent Document 1). reference). The powder toner has a problem that the toner scatters and a problem that the resolution is poor because the toner particles are as large as 7 to 10 μm, whereas such a liquid toner has a toner particle size of about 1 μm. In addition to being small and having a large charge amount, the toner image is hardly disturbed, and a high resolution can be realized.

  In addition, as a developing solution, a low-viscosity liquid toner in which toner is mixed in an organic solvent at a ratio of 1 to 2% uses an organic solvent that is harmful to the human body, and a large amount of toner is used because the toner concentration is low. Therefore, the problem of causing environmental problems may be caused. However, by using a high-viscosity and high-concentration developer constituted by dispersing a high-concentration toner in silicon oil or the like, such a problem is solved. It becomes possible to solve.

  FIG. 4 shows the overall configuration of such a conventional liquid toner developing type electrophotographic apparatus. In the figure, the photosensitive member 10 is charged to about 700 V by the charging device 11 and then exposed by the exposure device 12 to form an electrostatic latent image in which the potential of the exposed portion is about 100 V. The pre-wet apparatus 13 applies silicon oil having a viscosity of about 2.5 cSt to the surface of the photoreceptor 10 with a thickness of 4 to 5 μm.

  The developing device 14 is provided in association with yellow / magenta / cyan / black, and has a liquid viscosity of 400 to 4000 mPa · s, a carrier viscosity of 20 cSt, and a non-volatile high-viscosity and high-concentration liquid toner. Used as a developer. The developing roller is in contact with the photoconductor 10 so as to maintain a two-layer structure with the pre-wet liquid film on the photoconductor 10 and supplies liquid toner, and an electric field generated between the photoconductor 10 and the developing roller. Accordingly, the toner particles of the liquid developer are adhered to the photoreceptor 10.

  The intermediate transfer member 15 is biased to about −800 V and transfers the toner attached to the photosensitive member 10 in the order of yellow, magenta, cyan, and black in accordance with the electric field between the intermediate transfer member 15 and the photosensitive member 10. The pressure roller 19 fixes the toner of the intermediate transfer body 15 melted by the heating device 18 to the printing paper. The heating device 18 partially heats the surface of the intermediate transfer body 15 at a position before contacting the pressure roller 19.

  The developer is supplied to the developing roller by being transported while being thinly extended from the toner reservoir by the developer applying means, thereby forming a toner layer having a thickness of 2 to 3 μm on the developing roller. The The developing solution applying means is composed of a plurality of rotating rollers connected to each other, conveys the supplied liquid toner while being applied to the surface while being extended by the rotating roller, and is applied to the surface of the final-stage rotating roller. A liquid toner film is applied to the contact surface of the developing roller.

  However, a developer constituted by dispersing a high-concentration toner in silicon oil or the like has a high viscosity, so that it is not easy to uniformly apply it to the surface of the developing roller. If it is not possible to uniformly and uniformly supply the surface of the developing roller, a good image cannot be obtained.

  Conventionally, an automatic supply mechanism that controls a driving amount (supply amount) of a pump that supplies liquid toner is provided, and liquid toner is supplied by adjusting the hardness, surface roughness, roller interval, and the like of a pair of supply rollers. Was controlling. Although this method can ensure a considerable quality, it has the following problems.

  The layer thickness varies depending on the viscosity and particle size distribution of the toner. Therefore, it is necessary to compensate for viscosity change factors such as temperature.

Further, when the realistic roller hardness and surface roughness are combined with the current toner characteristics, the thickness of the toner layer determined between the supply rollers is not always freely selectable. Therefore, in order to determine the toner layer thickness to a certain amount, it may be necessary to adjust the rotational speed by providing a peripheral speed difference between the supply roller and the developing roller. This causes an unstable element such as jitter to be inherent in the roller drive system. In addition, excessive shear stress is applied to the toner as it passes between the rollers, which may cause solidification and precipitation.
Japanese Patent Laid-Open No. 11-25289

  Accordingly, the present invention solves such problems and, in an electrophotographic apparatus using a high-viscosity liquid toner, inhibits the continuous formation of mottled patterns caused by development, reduces the occurrence of mottled patterns, and develops a developing roller. An object of the present invention is to supply liquid toner uniformly and uniformly on the surface of the film with a high transfer rate.

  The liquid toner developing type electrophotographic apparatus of the present invention uses a high-viscosity liquid toner as a liquid developer, and contacts the photosensitive drum 10 on which the electrostatic latent image is formed with the liquid toner. A developing roller 22 to be supplied and a gravure roller 24 to which a bias potential is applied to the developing roller are provided. The gravure roller 24 has a large number of fine depressions on the surface, applies the liquid toner to be supplied to the developing roller 22 while regulating the amount of the liquid toner by the fine depressions, and applies a bias potential to the developing roller. Apply to increase the transfer rate of the liquid toner to be supplied.

  The present invention comprises a gravure roller having a large number of fine depressions on the surface, the amount of liquid toner to be supplied is regulated by the numerous fine depressions and applied to the developing roller (or development belt), In addition, since the gravure roller applies a bias potential to the developing roller, in an electrophotographic apparatus using a high-viscosity liquid toner, the continuous formation of the mottled pattern generated by development is hindered. The generation can be reduced, the liquid toner can be supplied uniformly and uniformly to the surface of the developing roller, and the transfer rate of the liquid toner supplied from the gravure roller can be increased.

  Hereinafter, the present invention will be described in detail according to embodiments. FIG. 1 is a view exemplifying a high-viscosity liquid toner supply mechanism in a liquid toner developing type electrophotographic apparatus including the present invention. In the figure, 10 is a photosensitive drum (image support), 22 is a developing roller, 24 is a gravure roller, and 25 is a blade.

  The developing roller 22 is in contact with the photosensitive drum 10 so as to maintain a two-layer structure with the pre-wet liquid film on the photosensitive drum 10 according to a normal technique, and supplies the liquid toner to the photosensitive drum 10. The toner particles of the liquid developer are attached to the photosensitive drum 10 in accordance with the electric field generated therebetween. The gravure roller 24, which is a feature of the present invention, rotates in contact with the developing roller 22, and applies liquid toner supplied by appropriate means on the surface of the gravure roller 24 to the developing roller with a uniform thickness.

  The gravure roller is a rotating roller having a structure similar to a gravure plate used for gravure printing. As is well known, gravure printing is one type of intaglio printing technique. This is because the depth and area of the recesses change, so that the way ink is applied to the surface of the printing paper changes, and the lightness and darkness appear. Similarly, the gravure roller 24 of the present invention also has many fine depressions formed on the surface thereof. For example, 100 to 400 depressions per inch can be formed with a pitch of 0.2 to 0.04 mm and a depth of 10 to 100 μm.

  The reason why the developing roller is uneven is that the toner is broken and separated by the two rollers at the roller outlet. At that time, the unevenness is continuously formed, and unevenness is generated one after another. On the other hand, since the gravure roller has a large number of indentations on the surface, a certain amount of layers can be formed by putting toner in these indentations and transferring them to the developing roller. By dividing the toner layer in a minute area, it is possible to inhibit the continuous formation of unevenness and obtain a uniform toner layer.

  A blade 25 is provided on the surface of the gravure roller 24 so as to abut against the moving direction of the surface of the gravure roller so as to scrape off the liquid toner on the surface. FIG. 2 is a view for explaining the operation of the blade 25. As shown in the figure, by scraping off excess liquid toner with the blade 25, a certain amount of toner layer regulated by a large number of fine depressions is accurately formed.

  The blade 25 can be formed of a metal such as stainless steel. Further, by using a blade made of rubber such as urethane having a hardness of 70 degrees or more, the toner from the surface to a certain depth can be scraped off. Further, instead of the blade, a roller for scraping off the liquid toner on the surface of the gravure roller can be used.

  3 uses a developing belt 23 having a belt structure in place of the developing roller shown in FIG. Similarly, the gravure roller 24 can inhibit the continuous formation of unevenness and supply a uniform and constant amount of liquid toner.

  A bias potential can be applied to the gravure roller 24 with respect to the developing roller 22 or the developing belt 23 to increase the transfer rate from the gravure roller 24.

FIG. 3 is a diagram illustrating a supply mechanism of a high-viscosity liquid toner in the liquid toner developing type electrophotographic apparatus including the present invention. It is a figure for demonstrating the effect | action of a braid | blade. FIG. 2 is a view showing an example in which a developing belt having a belt structure is used instead of the developing roller shown in FIG. 1. 1 is a diagram illustrating an overall configuration of a conventional liquid toner developing type electrophotographic apparatus.

Explanation of symbols

10 Photosensitive drum (photoconductor)
DESCRIPTION OF SYMBOLS 11 Charging device 12 Exposure device 13 Pre-wet device 14 Developing device 15 Intermediate transfer member (roller)
16 Blade 17 Static eliminating device 18 Heating device 19 Pressure roller 22 Developing roller 23 Developing belt 24 Gravure roller 25 Blade

Claims (4)

A liquid toner developing type electrophotographic apparatus using a high viscosity liquid toner as a liquid developer,
An image support on which an electrostatic latent image is formed;
A developing roller for supplying liquid toner in contact with the image support;
A rotating roller having a large number of fine depressions on the surface, applying the liquid toner to be supplied to the developing roller while regulating the amount of the supplied liquid toner, and applying a bias potential to the developing roller When,
A liquid toner developing type electrophotographic apparatus comprising: 2. The liquid toner developing type electrophotographic apparatus according to claim 1, wherein the application of the bias potential changes a transfer rate of the liquid toner to the developing roller. The liquid toner developing type electrophotographic apparatus according to claim 1, wherein the developing roller has a belt structure. 2. The liquid toner developing type electrophotographic apparatus according to claim 1, further comprising scraping off excess liquid toner by bringing another rotating roller into contact with the surface of the rotating roller.

Images