JP2007171604A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can obtain images of high quality, has a developing roller and a toner compressing roller arranged close to each other, and uses liquid toner. <P>SOLUTION: The image forming apparatus is equipped with the developing roller that carries liquid toner having toner dispersed in carrier liquid, a photoreceptor on which latent image to be developed by the developing roller is formed, and the toner compressing roller which is arranged close to the developing roller, at a position prior to development to a photoreceptor by the developing roller and compresses the liquid toner. The apparatus is equipped with a rotating means of making the toner compressing roller irrotational, when image is formed, and rotating the toner compressing roller when no image is formed; a means of applying the carrier liquid on the toner compressing operation surface of the toner compressing roller; and a cleaning means of cleaning the toner compressing operation surface of the toner compressing roller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using liquid toner in which toner is dispersed in a carrier liquid.

As a prior art of an image forming apparatus using liquid toner, Japanese Patent Application Laid-Open No. 2002-278291 discloses a developing roller before development in an image forming apparatus that develops a latent image on a photoreceptor with a developing roller carrying liquid toner. A toner compression roller for compressing the liquid toner is placed in contact with or close to the developing roller, and independent voltages are applied to the developing roller and the toner compression roller, respectively. There has been disclosed an image forming apparatus in which the applied voltage of the developing roller is used to prevent image fogging and density unevenness and obtain a high quality image.
JP 2002-278291 A

  The toner compression roller of the prior art rotates with respect to the developing roller during image formation, and the toner compaction state fluctuates with the rotation period of the toner compression roller due to the influence of the rotational vibration of the toner compression roller. There is a problem that banding on images tends to occur. In addition, when the developing roller and the toner compression roller are arranged close to each other without contact, it is possible to avoid deterioration in image quality due to toner adhesion on the toner compression roller. Since the gap with the roller cannot be accurately maintained, the toner compression conditions are changed, and proper toner compression cannot be performed, so that a high-quality image cannot be obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that uses a liquid toner in which a developing roller capable of obtaining a high-quality image and a toner compression roller are arranged close to each other to solve the above problems.

  In order to solve the above problems, the first invention provides a developing roller for carrying a liquid toner in which a toner is dispersed in a carrier liquid, a photoreceptor on which a latent image developed by the developing roller is formed, and the developing In an image forming apparatus provided with a toner compression roller that is disposed close to the developing roller and compresses liquid toner at a position before development on the photosensitive member of the roller, the toner compression roller is non-rotated during image formation, and non-image formation is performed Rotation means for rotating the toner compression roller, means for applying a carrier liquid to the toner compression operation surface of the toner compression roller, and cleaning means for cleaning the toner compression operation surface of the toner compression roller. And

  According to the second aspect of the present invention, in the image forming apparatus according to the first aspect of the invention, after the rotation of the toner compression roller during non-image formation, the position of the toner compression roller disposed close to the developing roller during image formation is always the same position. It has the means to position so that it may become.

  According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect of the present invention, spacers that contact the developing roller are disposed at both ends of the toner compression roller, and a carrier liquid is applied to the spacer surface during image formation. It is characterized by.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the carrier recovered from the toner compression roller as a carrier liquid applied to a spacer of the toner compression roller or a toner compression operation surface. It is characterized by using a liquid.

According to the configuration of the first aspect of the present invention, the toner compression roller is non-contacting and non-rotating with respect to the developing roller at the time of image formation, so that toner under appropriate conditions can be obtained without causing vibrations and gap deviations. In the non-image formation, the toner compression operation surface of the toner compression roller is rotated and cleaned while applying the carrier liquid, so that the toner can be compressed under appropriate conditions during the image formation.
According to the configuration of the second aspect of the invention, the position of the toner compression roller with respect to the developing roller in the image forming diagram is always the same position, so that toner compression conditions such as a gap do not fluctuate and toner compression of appropriate toner is possible. It becomes.
According to the third aspect of the invention, the gap between the developing roller and the toner compression roller can be accurately maintained, and the carrier liquid supplied to the sliding surface between the spacer of the toner compression roller in a stopped state and the rotating developing roller during image formation Functions as a lubricant, prevents vibrations caused by sliding, and enables proper toner compression of toner.
According to the configuration of the fourth aspect of the invention, the carrier liquid applied to the spacer of the toner compression roller or the toner compression operation surface can be supplied from the nearest place.

    Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention.

  The intermediate transfer belt 70 is an endless belt stretched around a belt driving roller 82 and a driven roller 85, and is rotationally driven while being in contact with the photoreceptors 20Y, 20M, 20C, and 20K. Four primary transfer units 60Y, 60M, 60C, and 60K including the intermediate transfer belt 70, the primary transfer backup rollers 61Y, 61M, 61C, and 61K and the photoconductors 20Y, 20M, 20C, and 20K are arranged on the intermediate transfer belt 70. The color liquid toners are sequentially superimposed and transferred to form a full color liquid toner image.

  The secondary transfer unit 80 includes a secondary transfer roller 81, an intermediate transfer belt driving roller 82, a secondary transfer roller blade 83, and a secondary transfer roller cleaning liquid recovery unit 84, and is formed on the intermediate transfer belt 70. A liquid toner image or a full-color liquid toner image is transferred to a paper recording medium.

  A fixing unit (not shown) is a device for fusing a single color liquid toner image or a full color liquid toner image transferred onto a recording medium onto the recording medium to form a permanent image.

  The developing units 50Y, 50M, 50C, and 50K have a function of developing a latent image with yellow (Y) liquid toner, magenta (M) liquid toner, cyan (C) liquid toner, and black (K) liquid toner, respectively. ing.

  The developing units 50Y, 50M, 50C, and 50K are roughly supplied with developing toner containers 53Y, 53M, 53C, and 53K that store the liquid toners, and supply the liquid toners from the developing toner containers to the developing rollers 54Y, 54M, 54C, and 54K. Toner supply rollers 51Y, 51M, 51C, 51K, photoconductors 20Y, 20M, 20C, 20K charging units 30Y, 30M, 30C, 30K, and exposure unit 40Y for forming an electrostatic latent image on the charged photoconductor , 40M, 40C, 40K.

  Since the developing units 50Y, 50M, 50C, and 50K have the same configuration, the developing unit 50K will be described below.

  As shown in FIG. 1, a charging unit 30K, an exposure unit 40K, and a primary transfer unit 60K are mainly arranged along the rotation direction of the photoconductor 20K. The photoconductor 20K includes a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and can rotate around a central axis. In the present embodiment, the photoconductor 20K rotates clockwise.

  The charging unit 30K is a device for charging the photoconductor 20K. The exposure unit 40K has a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and irradiates the modulated laser onto the charged photoconductor 20K to form a latent image.

  The developing unit 50K is a device for developing the latent image formed on the photoconductor 20K using black (K) liquid toner. The developing unit 50K will be described later.

  The primary transfer unit 60K is a device for transferring the black liquid toner image formed on the photoreceptor 20K to the intermediate transfer belt 70.

  FIG. 2 is a cross-sectional view showing main components of the developing unit 50K. The developing toner container 53K contains black liquid toner for developing the latent image formed on the photoreceptor 20K. In the liquid toner used in this embodiment, solid particles having an average particle diameter of 1 μm in which a colorant such as a pigment is dispersed in a thermoplastic resin are dispersed in a liquid solvent such as an organic solvent, silicon oil, mineral oil, or edible oil. It is a non-volatile liquid toner at room temperature with a high viscosity (about 30 to 10000 mPa · s) that is added together with the agent and has a toner solid content concentration of about 25%.

  Liquid toner is supplied from the developing toner container 53K to the developing roller 54K by the toner supply roller 51K. The toner supply roller 51K is a cylindrical member, and is an aniloc roller that rotates clockwise as shown in FIG. 2 and has fine and uniform spiral grooves formed on the surface. The groove dimensions are such that the groove pitch is about 130 μm and the groove depth is about 30 μm.

  The toner regulating blade 52K includes a rubber portion made of urethane rubber or the like that contacts the surface of the toner supply roller 51K, and a metal plate that supports the outer rubber portion, and scrapes off the liquid toner remaining on the toner supply roller 51K. Remove.

  The developing roller 54K is a cylindrical member, and rotates counterclockwise around the central axis as shown in FIG. The developing roller 54K is provided with an elastic body such as conductive urethane rubber, a resin layer, and a rubber layer on the outer periphery of an inner core made of metal such as iron. The developing roller 54K is provided with a developing roller blade 58K and a developing roller cleaning liquid recovery unit 59K. The developing roller blade 58K is made of rubber or the like that contacts the surface of the developing roller 54K, and scrapes and removes the liquid toner remaining on the developing roller 54K. The developing roller cleaning liquid recovery unit 59K is a container for storing liquid toner scraped off by the developing roller blade 58K.

  The toner compression roller 55K is a cylindrical member, and includes a conductive resin or rubber layer on the surface layer of the metal roller. A voltage is applied to the toner compression roller 55K separately from the developing roller 54K, and a potential difference is provided between the two rollers. The toner compression roller 55K is disposed close to the developing roller 54K while maintaining a certain gap. Spacers 16 (see FIG. 3) are attached in the vicinity of both ends of the toner compression roller 55K as means for maintaining a gap between the developing roller 54K and the toner compression roller 55K. The toner compression roller 55K does not rotate during image formation. During non-image formation, it is rotated by the driving means 17 (see FIG. 3). Further, the driving unit 17 of the toner compression roller 55K includes a positioning unit 18 (see FIG. 3) so that the toner compression roller 55K and the developing roller 54K are always in the same position during image formation. The toner compression roller blade 56K is made of rubber or the like that comes into contact with the surface of the toner compression roller 55K, and the toner compression roller 55K rotates during non-image formation to clean and remove the liquid toner remaining on the toner compression roller 55K. The toner compression roller cleaning liquid recovery unit 57K is a container for storing the liquid toner scraped off by the toner compression roller blade 56K. The toner compression roller cleaning liquid recovery unit 57K is provided with a carrier liquid application roller 15 (see FIG. 3) that applies a carrier liquid to the toner compression operation surface of the toner compression roller 55K that rotates during non-image formation. The toner compression roller cleaning liquid recovery unit 57K is provided with an application unit (not shown) for applying a carrier liquid to the spacer 16 during image formation.

  The photoconductor 20K is a cylindrical member that is wider than the developing roller 54K and has a photosensitive layer formed on the outer peripheral surface thereof, and rotates clockwise around the central axis as shown in FIG. The photosensitive layer of the photoreceptor 20K is composed of an organic photoreceptor or an amorphous silicon photoreceptor.

  The charger 30K is provided upstream of the nip portion between the photoconductor 20K and the developing roller 54K. The charger 30K is applied with a bias having the same polarity as the liquid toner from a power supply device (not shown), and charges the photoconductor 20K. The charged photoconductor 20K is irradiated with laser from the exposure unit 40K to form a latent image. The formed latent image is developed by the developing roller 54K and is primarily transferred to the intermediate transfer belt 70 in the primary transfer unit 60K.

  Next, the operation of such an image forming apparatus will be described. Subsequently, the developing unit will be described by taking the developing unit 50K of the four developing units as an example.

The liquid toner in the developing toner container 53K has a solid concentration of 25%, a viscosity of 30 to 10,000 mPa · s, and the toner particles have a positive charge. The liquid toner is pumped up from the developing toner container 53K as the toner supply roller 51K rotates. The toner supply roller 51K rotates in the rotational direction of the normal developing roller 54K so that the surface speed thereof is the same as that of the developing roller 54K. The peripheral speed of the developing roller 54K is 200 mm / s.
The toner regulating blade 52K is in contact with the surface of the toner supply roller 51K, leaves the developer in the groove formed on the surface of the toner supply roller 51K, and scrapes off other excess developer. The amount of liquid toner supplied to the developing roller 54K is regulated. According to this regulation, the film thickness of the liquid toner applied to the developing roller 54K is quantified so as to be 6 μm. The liquid toner scraped off by the toner regulating blade 52K falls into the developing toner container 53K due to gravity.

  The developing roller 54K coated with the liquid toner is close to the toner compression roller 55K downstream of the nip portion with the toner supply roller 51K. The toner compression roller 55K is not rotated during image formation, and a voltage higher than the voltage applied to the developing roller 54K is applied. Therefore, the toner on the developing roller 54K moves to the developing roller 54K side when passing through the nip with the toner compression roller 55K, and only the carrier liquid containing almost no toner particles is collected in the toner compression roller 55K. . As a result, the toner particles are gently coupled to form a film. As a result, the toner moves quickly in the developing unit, and the image density is improved.

  The photoreceptor 20K uses amorphous silicon, and charges the surface to about +600 V by applying about +5.5 kV to the wire of the corona charger 30K upstream of the nip portion with the developing roller 54K. After charging, a latent image is formed by the exposure unit 40K so that the potential of the image portion becomes + 25V. In the developing nip portion formed between the developing roller 54K and the photoconductor 20K, a bias + 400V applied to the developing roller 54K and a latent image (image portion + 25V, non-image portion + 600V) applied to the photoconductor 20K are formed. According to the electric field, the toner particles selectively move to the image portion on the photoconductor 20K. Thereby, a toner image is formed on the photoconductor 20K. Since the carrier liquid is not affected by the electric field, it is separated at the exit of the developing nip between the developing roller 54K and the photoconductor 20K, and adheres to both the developing roller 54K and the photoconductor 20K.

  The photosensitive member 20K that has passed through the developing nip portion passes through the nip portion with the intermediate transfer belt 70, and primary transfer is performed. The primary transfer backup roller 61K is applied with a voltage of about −200 V having the opposite polarity to the charging characteristics of the toner particles, and the toner particles on the photoconductor 20K are primarily transferred to the intermediate transfer belt 70 and transferred to the photoconductor 20K. Only the carrier liquid remains. The carrier liquid remaining on the photoconductor 20K is scraped off by the photoconductor blade 21K downstream of the primary transfer unit and collected by the photoconductor cleaning liquid collection unit 22K.

  The toner image primarily transferred onto the intermediate transfer belt 70 by the primary transfer unit 60K is directed to the secondary transfer unit 80. A voltage of −1000 V is applied to the secondary transfer roller 81 of the secondary transfer unit 80, and is maintained at 0 V to the intermediate transfer belt driving roller 82. The toner particles on the intermediate transfer belt 70 are recorded on paper or the like. Secondary transferred to the medium.

  The toner compression roller 55K, which is a characteristic configuration of the present invention, will be described with reference to FIGS. The toner compression roller 55K has spacers 16 wound around both ends thereof. The spacer 16 is in contact with the non-developing portion at both ends of the developing roller 54K, and forms a gap between the developing roller 54K and the toner compression roller 55K. By accurately maintaining the gap, it is possible to compress the toner appropriately.

  The toner compression roller 55K is not rotated during image formation, that is, during toner compression. Since the toner compression roller 55K is stopped during the toner compression operation, image defects such as banding due to rotational shake can be suppressed. Further, since the toner compression roller 55K is stopped, a peripheral speed difference is always generated between the toner compression roller 55K and the developing roller 54K, so that it is possible to eliminate development defects caused by uneven toner supply.

  During the toner compression operation, the developing roller 54K rotates and the toner compression roller 55K does not rotate. Therefore, the spacers 16 disposed at both ends of the toner compression roller 55K are in contact with and slide on both ends of the developing roller 54K. . A carrier liquid is applied to the surface of the spacer 16 by an application means (not shown) disposed in the toner compression roller cleaning liquid recovery part 57K, and the carrier liquid functions as a lubricant.

  If the toner compression operation is continued while the adjacent toner compression roller 55K is stopped during image formation, toner particles adhere to the toner compression operation surface of the toner compression roller 55K, and the image quality gradually deteriorates. Therefore, the toner compression roller 55K is rotated by the drive motor 17 for cleaning the toner compression roller 55K during non-image formation, that is, during non-toner compression operation. At this time, the carrier liquid is applied to the toner compression operation surface of the toner compression roller 55K by the carrier liquid application roller 15 disposed in the toner compression roller cleaning liquid recovery unit 57K. By applying the carrier liquid, cleaning with the toner compression roller blade 56K can be performed efficiently.

  After the cleaning of the toner compression roller 55K is completed, the rotation of the toner compression roller 55K is stopped. Since the toner compression roller 55K performs the toner compression operation in the stopped state at the time of image formation, it is important from the viewpoint that the toner compression condition does not fluctuate so that the toner compression operation surface is always at the same position with respect to the developing roller 54K. is there. Therefore, in the present invention, the positioning means 18 for the toner compression roller 55K is provided.

  4A, 4B and 4C show an embodiment of the positioning means 18. FIG. In the embodiment of FIGS. 4A, 4B, and 4C, a groove or the like is formed at a predetermined position at the end of the toner compression roller 55K, and the positioning means 18 is engaged with the groove, so that the toner compression roller 55K. The position relative to the developing roller 54K during the toner compression operation is always held at the same position. In addition to the embodiment shown in the figure, as a positioning means, an electromagnetic brake, a means such as energization of a stepping motor may be used.

It is a figure which shows embodiment of this invention. It is a figure which shows embodiment of this invention. It is a figure which shows embodiment of this invention. (A) (b) (c) It is a figure which shows embodiment of this invention.

Explanation of symbols

15: Carrier liquid application roller, 16: Spacer, 17: Drive motor, 18: Positioning means 20Y, 20M, 20C, 20K: Photoconductor 21K: Photoconductor blade, 22K: Photoconductor cleaning liquid recovery unit 30Y, 30M, 30C , 30K: Corona chargers 40Y, 40M, 40C, 40K: Exposure units 50Y, 50M, 50C, 50K: Development units 51Y, 51M, 51C, 51K: Toner supply rollers 53Y, 53M, 53C, 53K: Development toner containers 54Y, 54M, 54C, 54K: developing roller 52K: toner regulating blade, 55K: toner compression roller, 56K: toner compression roller blade, 57K: toner compression roller cleaning recovery unit, 58K: development roller blade, 59K: development roller cleaning liquid recovery unit 60Y, 60M, 0C, 60K: the primary transfer unit 61Y, 61M, 61C, 61K: primary transfer backup roller 70: intermediate transfer belt

Claims (4)

A developing roller carrying liquid toner in which toner is dispersed in a carrier liquid; a photosensitive member on which a latent image developed by the developing roller is formed; and the developing roller at a position of the developing roller before development on the photosensitive member And a toner compression roller that is disposed adjacent to and compresses the liquid toner, a rotating means that rotates the toner compression roller when the image is not formed and rotates the toner compression roller when the image is formed, and a carrier liquid. An image forming apparatus comprising: means for applying the toner compression operation surface of the toner compression roller; and cleaning means for cleaning the toner compression operation surface of the toner compression roller. 2. The image forming apparatus according to claim 1, further comprising means for positioning so that the position of the toner compression roller disposed close to the developing roller during image formation is always the same after the rotation of the toner compression roller during non-image formation. The image forming apparatus described in 1. The image forming apparatus according to claim 1, wherein spacers that contact the developing roller are disposed at both ends of the toner compression roller, and a carrier liquid is applied to a surface of the spacer during image formation. 4. The image formation according to claim 1, wherein the carrier liquid collected from the toner compression roller is used as a carrier liquid applied to a spacer or a toner compression operation surface of the toner compression roller. apparatus.

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