JP2007041364A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus where the pattern of an anilox roller is not left on a developing roller, so that the deterioration of an image on a recording medium is prevented. <P>SOLUTION: A carrier oil application roller 22Y is provided, immediately in front a nip formed by the developing roller 9Y and the anilox roller 8Y, and the carrier oil application roller 22Y is made to abut against the developing roller 9Y or the anilox roller 8Y. The carrier oil application roller 22Y applies liquid carrier to the surface of the developing roller 9Y, immediately in front developer is supplied to the developing roller 9Y from the anilox roller 8Y. Since the surface of the developing roller 9Y or the anilox roller 8Y is wetted with the liquid carrier, immediately in front the developer is supplied to the developing roller 9Y from the anilox roller 8Y, the pattern of the anilox roller 8Y is easily moderated, after the developer in the groove of the anilox roller 8Y has been transferred to the surface of the developing roller 9Y. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that develops an electrostatic latent image formed on a photoreceptor with a developer in which toner is dispersed in a carrier liquid made of silicon oil or mineral oil.

  2. Description of the Related Art Conventionally, a liquid developing type electrophotographic apparatus using a high viscosity liquid developer in which toner is dispersed in a carrier liquid made of silicon oil or mineral oil is known. In such an apparatus, it is necessary to uniformly supply the liquid developer to the developing roller used for developing the latent image on the photosensitive drum.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-34073) discloses a liquid toner developing type electrophotographic apparatus using a high viscosity liquid toner as a liquid developer, and an image support on which an electrostatic latent image is formed. A developing roller for supplying liquid toner in contact with the image support; and a large number of fine depressions on the surface, and the amount of liquid toner to be supplied is regulated by the numerous fine depressions, and the development is performed. A liquid toner developing type electrophotographic apparatus comprising a rotating roller applied to a roller is disclosed.

In Patent Document 2 (Japanese Patent Laid-Open No. 2003-173088), a used liquid developer is collected in a toner adjustment tank from an electrophotographic apparatus that develops using a highly viscous liquid developer, and the collected liquid developer is recovered. A toner concentration adjustment method for a toner recycling system is disclosed in which a high-concentration developer or carrier liquid is supplied according to the detected concentration of the liquid developer so as to be adjusted to a predetermined concentration and reused.
JP 2001-34073 A JP 2003-173088 A

  In the conventional liquid toner developing type electrophotographic apparatus disclosed in Patent Document 1, since the developing roller is structured to rotate together with the rotating roller (gravure roller), the rotating roller (gravure roller) is disposed on the developing roller. ) Pattern remains. The pattern remaining on the developing roller also remains when developing the latent image on the photosensitive drum, and finally also remains on the image transferred to the recording medium. Due to this influence, image quality is liable to be disturbed when trying to express a thin line on the recording medium. In particular, when plain paper or rough paper is used as the recording medium, voids are likely to occur.

  In the case of the prior art disclosed in Patent Document 1, for example, when an extreme printing sequence continues, such as printing an image biased to a specific color, the density fluctuation of the liquid toner may increase. This effect also affects the final printed image density and image quality.

  In order to adjust such fluctuations, the technique disclosed in Patent Document 2 can be used. However, the one disclosed in Patent Document 2 requires a large-scale configuration such as a toner adjustment tank, and the apparatus is expensive. There was a problem of becoming something.

  SUMMARY An advantage of some aspects of the invention is that an invention according to claim 1 is formed on a photosensitive member in an image forming apparatus that forms an image using a developer in which toner is dispersed in a carrier. A developing roller that develops the electrostatic latent image, an anilox roller that supplies a liquid developer to the developing roller, and a carrier oil application roller that contacts the developing roller or the anilox roller to apply a carrier. It is characterized by that.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the carrier oil application roller is provided immediately before a nip formed by the developing roller and the anilox roller. And

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the developer storage unit, and a toner concentration detection mechanism that detects the toner concentration of the developer in the developer storage unit, And a mechanism for separating or abutting the carrier oil application roller with respect to the developing roller or the anilox roller in accordance with an output from the toner concentration detection mechanism. To do.

  According to the present invention, since the carrier oil application roller that contacts the development roller or the anilox roller and applies the carrier is provided, the surface of the development roller or the anilox roller becomes wet with the liquid carrier, and the anilox roller After the developer in the groove is transferred to the surface of the developing roller, the anilox roller pattern is easily relaxed. Therefore, the developer on the developing roller hardly causes the anilox roller pattern to remain, and the influence of the anilox roller pattern is almost eliminated when the latent image on the photosensitive drum is developed by the developing roller. Finally, even when trying to express a thin line on the recording medium, there is no effect on the image quality, and even when plain paper or rough paper is used as the recording medium, voids are likely to occur. Occurrence disappears.

In addition, since the developer density fluctuation can be adjusted on the developing roller or the anilox roller, the image quality of the printed matter can be maintained even when an extreme printing sequence continues.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing main components constituting the image forming apparatus according to the embodiment of the present invention. The developing units 50Y, 50M, 50C, and 50K are disposed in the lower part of the image forming apparatus, and the intermediate transfer belt 70 and the secondary transfer unit 80 are disposed in the upper part of the image forming apparatus.

  The development units 50Y, 50M, 50C, and 50K have a function of developing a latent image with a yellow (Y) developer, a magenta (M) developer, a cyan (C) developer, and a black (K) developer, respectively. ing. As the yellow (Y) developer, magenta (M) developer, cyan (C) developer, and black (K) developer, toners of various colors are dispersed in a liquid carrier. The developer storage units 3Y, 3M, 3C, and 3K of each development unit are supplied with toner of each color from the toner tanks 2Y, 2M, 2C, and 2K, and the carrier tank 1 is supplied with a liquid carrier through the pipe 10, Each developer unit is adjusted to an appropriate concentration in the developer storage units 3Y, 3M, 3C, and 3K. Since the developing units 50Y, 50M, 50C, and 50K have the same configuration, the developing unit 50Y will be described below.

  As shown in FIG. 1, the developing unit 50Y includes a charging unit 30Y, an exposure unit, a developing unit 50Y as an example of a developing device, and a primary transfer unit 60Y along the rotation direction of a photoreceptor 20Y as an example of an image carrier. have.

  The photoreceptor 20Y has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and is rotatable about a central axis. In the present embodiment, as shown by an arrow in FIG. Rotate clockwise.

  The charging unit 30Y is a device for charging the photoconductor 20Y. From an exposure unit (not shown), a latent image is formed on the charged photoreceptor 20Y by irradiating a laser in the optical path 40Y. The exposure unit has a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and irradiates a modulated laser onto the charged photoconductor 20Y based on an input image signal.

  The developing unit 50Y is a device for developing the latent image formed on the photoreceptor 20Y using a yellow (Y) developer. Details of the developing unit 50Y will be described later.

  The primary transfer unit 60Y is a device for transferring the yellow developer image formed on the photoreceptor 20Y to the intermediate transfer belt 70. When the four color developers are sequentially transferred by the primary transfer units 60Y, 60M, 60C, and 60K, a full color developer image is formed on the intermediate transfer belt 70.

  The intermediate transfer belt 70 is an endless belt stretched around a plurality of support rollers, and is rotationally driven while being in contact with the photoreceptors 20Y, 20M, 20C, and 20K.

  The secondary transfer unit 80 is a device for transferring a single color developer image or a full color developer image formed on the intermediate transfer belt 70 to a medium such as paper, film, or cloth.

  A fixing unit (not shown) is a device for fusing a single color developer image or a full color developer image transferred onto a medium onto a medium such as paper to form a permanent image.

  The intermediate transfer belt cleaning unit 90 is a device for scraping and removing the developer remaining on the intermediate transfer belt 70 by the cleaning blade 91 after the developer image is transferred by the secondary transfer unit 80.

  FIG. 2 is a sectional view showing main components of the developing unit according to the embodiment of the present invention. In FIG. 2, 1 is a carrier tank, and 2Y is a toner tank for yellow (Y) toner. The carrier tank 1 is provided in common for each color, and supplies a liquid carrier to each developer storage unit through the pipe 10.

  The developer storage unit 3Y is divided into a primary developer storage unit 5Y and a secondary developer storage unit 6Y. The toner tank 2Y and the carrier tank 1 supply toner and liquid carrier to the primary developer storage unit 5Y. A toner amount adjusting valve 25Y adjusts the amount of toner supplied from the toner tank 2Y to the primary developer storage unit 5Y. Reference numeral 24Y denotes a carrier amount adjusting valve that adjusts the amount of liquid carrier supplied from the carrier tank 1 to the primary developer storage unit 5Y via the carrier storage unit 4Y.

  The developer storage unit 3Y contains a developer composed of toner and liquid carrier for developing the latent image formed on the photoreceptor 20Y. The developer accommodated in the developer storage unit 3Y is a low concentration (about 1 to 2 wt%) and low viscosity with Isopar (trademark: exon) as a carrier, which is generally used conventionally, and is volatile at room temperature. It is not a volatile liquid developer having a property, but a non-volatile liquid developer having a high concentration and a high viscosity and having a non-volatile property at room temperature. That is, the liquid developer according to the present embodiment has a high concentration (5 of toner particles made of resin, pigment, and the like having an average particle size of about 0.1 to 5 μm in a non-volatile and insulating carrier liquid such as silicone oil. High viscosity (about 100 to 10,000 mPa · s) developer dispersed in about 40 wt%.

  In the primary developer storage unit 5Y, the stirring roller 7Y has a structure for stirring the developer. Further, the developer accommodated in the primary developer storage unit 5Y is transported to the secondary developer storage unit 6Y by appropriate means.

  The anilox roller 8Y supplies the developer from the secondary developer storage unit 6Y to the developing roller 9Y. As shown in FIG. 3, the anilox roller 8Y has a uniform and spiral groove on the surface of a metallic roller such as iron and is plated with nickel. The anilox roller 8Y in the present embodiment includes a groove having a trapezoidal cross section as the groove. FIG. 4 shows an example of the groove dimensions of the anilox roller 8Y. The groove pitch is about 170 μm, the peak width is about 45 μm, the valley width is about 30 μm, and the groove depth is about 50 μm.

  Further, the anilox roller 8Y has a surface pressed against the elastic layer of the developing roller 9Y in order to appropriately transfer the developer on the anilox roller 8Y to the developing roller 9Y.

  The anilox roller 8Y is rotatable about its central axis, and the central axis is below the rotation central axis of the developing roller 9Y. The anilox roller 8Y rotates in a direction (clockwise in FIG. 2) opposite to the rotation direction of the developing roller 9Y (counterclockwise in FIG. 2).

  The regulating blade 21Y contacts the surface of the anilox roller 8Y and regulates the amount of developer on the anilox roller 8Y. That is, the regulation blade 21Y plays a role of scraping off the excess developer on the anilox roller 8Y and measuring the developer on the anilox roller 8Y supplied to the development roller 9Y. The restriction blade 21Y is made of urethane rubber as an elastic body, and is supported by a restriction blade support structure (not shown) made of metal such as iron.

  The developing roller 9Y carries the developer and conveys it to the developing position facing the photoconductor 20Y in order to develop the latent image carried on the photoconductor 20Y with the developer.

  The developing roller 9Y is provided with an elastic layer as an example of an elastic portion having conductivity on the outer peripheral portion of an inner core made of metal such as iron. The developing roller 9Y is in pressure contact with each of the anilox roller 8Y and the photoconductor 20Y in a state of being elastically deformed with the elastic body serving as a pressure contact portion.

  Further, the developing roller 9Y can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 20Y. Further, the developing roller 9Y rotates in a direction (counterclockwise in FIG. 2) opposite to the rotation direction (clockwise in FIG. 2) of the photoconductor 20Y. When developing the latent image formed on the photoconductor 20Y, an electric field is formed between the developing roller 9Y and the photoconductor 20Y.

  The developing roller cleaning unit has a rubber developing roller cleaning blade 14Y in contact with the surface of the developing roller 9Y, and develops the developer remaining on the developing roller 9Y after the development is performed at the developing position. It is an apparatus for scraping and removing with a roller cleaning blade 14Y. The developer thus scraped off is collected in the remaining developer collecting unit 15Y provided in the developing roller cleaning unit, and further returned to the primary developer storage unit 5Y.

  The developer thin film formed on the current developing roller 9Y in this way reaches the developing position (that is, the pressure contact position with the photoconductor 20Y) facing the photoconductor 20Y by the rotation of the developing roller 9Y. The latent image formed on the photoconductor 20Y is subjected to development at a position under an electric field of a predetermined magnitude.

  The squeeze roller 16Y is a mechanism for recovering the liquid carrier on the photoconductor 20Y. The recovered liquid carrier is scraped off by the squeeze roller cleaning blade 17Y and stored in the carrier liquid recovery unit 18Y. The liquid carrier stored in the carrier liquid recovery unit 18Y is stored in the carrier storage unit 4Y through the pipe 10.

  The photoconductor cleaning unit includes a rubber photoconductor cleaning blade 12Y in contact with the surface of the photoconductor 20Y and a photoconductor cleaning liquid recovery unit 13Y. After the image of the yellow developer image formed on the photoreceptor 20Y is transferred to the intermediate transfer belt 70 by the primary transfer unit 60Y, the developer remaining on the photoreceptor 20Y is removed from the photoreceptor cleaning unit. It is scraped off by the photoreceptor cleaning blade 12Y.

  The carrier oil application roller 22Y is in contact with the surface of the developing roller 9Y or the anilox roller 8Y and applies the liquid carrier to the developing roller 9Y. FIG. 2 shows a state where the carrier oil application roller 22Y is in contact with the developing roller 9Y. However, even if the carrier oil application roller 22Y is in contact with the anilox roller 8Y, it is unique to the present invention. The effect can be obtained. The carrier oil application roller 22Y is made of metal and receives the supply of the liquid carrier through a pipe from the carrier storage unit 4Y as shown in FIG. The carrier oil application roller 22Y is provided immediately before the nip formed by the developing roller 9Y and the anilox roller 8Y, as shown in the drawing. That is, the liquid carrier is applied to the surface of the developing roller 9Y or the anilox roller 8Y immediately before the developer is supplied from the anilox roller 8Y to the developing roller 9Y.

  With such a configuration, immediately before the developer is supplied from the anilox roller 8Y to the developing roller 9Y, the surface of the developing roller 9Y or the anilox roller 8Y is wetted with the liquid carrier, so the developer in the groove of the anilox roller 8Y. Is transferred to the surface of the developing roller 9Y, the anilox roller pattern is easily relaxed. Therefore, the developer on the developing roller 9Y is hardly left with an anilox roller pattern, and even when the developing roller 9Y develops the latent image on the photosensitive drum 20Y, the anilox roller pattern has almost no influence. Disappear. Eventually, even when trying to express thin lines on the recording medium, there is no effect on the image quality, and even when plain paper or rough paper is used as the recording medium, voids are not generated. Disappear.

  As shown in FIG. 5, the carrier oil application amount regulating blade 19Y contacts the surface of the carrier oil application roller 22Y and adjusts the amount of liquid carrier that the carrier oil application roller 22Y supplies to the developing roller 9Y. 5 is an enlarged view of a contact portion between the carrier oil application roller 22Y and the carrier oil application amount regulating blade 19Y. The carrier oil application amount regulating blade 19Y is made of urethane rubber as an elastic body, and is supported by a regulating blade support structure (not shown) made of metal such as iron. The carrier oil application amount adjusting valve 23Y adjusts the amount of liquid carrier supplied to the carrier oil application roller 22Y.

  Furthermore, by providing a mechanism for separating the carrier oil application roller 22Y from the developing roller 9Y, the amount of liquid carrier supplied from the carrier oil application roller 22Y to the developing roller 9Y can be controlled.

  For such control, it is necessary to detect the toner density of the developer. The toner density detection is performed by detecting the torque of the motor for operating the stirring roller 7Y in the developer storage unit 3Y. To do. That is, the relationship between the viscosity of the developer and the current output from the motor torque is grasped, and when the output current fluctuates more than usual, it is determined that a change has occurred in the toner density of the developer, Control is performed such that the carrier oil application roller 22Y is separated from the developing roller 9Y.

  For example, assuming that the toner concentration of the developer in the developer storage unit 3Y is 25% by weight, if the toner concentration varies up to ± 2%, the density and image quality of the image recorded on the recording medium are greatly affected. Absent. When the change in the toner density is more than that, it is necessary to make an adjustment to suppress the change.

  Therefore, when the toner concentration of the developer in the developer storage unit 3Y varies by + 2% or more than usual, the carrier oil application roller 22Y is brought into contact with the developing roller 9Y, and the developer concentration transferred to the developing roller 9Y is within an appropriate range. Adjust so that it is inside. On the other hand, when the toner density of the developer in the developer storage unit 3Y fluctuates by more than −2% than usual, the carrier oil application roller 22Y is adjusted to be separated from the developing roller 9Y.

  FIG. 6 shows the case where the carrier oil application roller 22Y is brought into contact with the surface of the anilox roller 8Y. The surface of the anilox roller 8Y immediately after the liquid carrier is applied to the anilox roller 8Y by the carrier oil application roller 22Y. An enlarged view of the state is also shown. As described above, the surface of the anilox roller 8Y includes a groove having a trapezoidal cross section and is divided into a peak portion and a valley portion. When the liquid carrier is applied to the anilox roller 8Y, carrier oil is present at the peak as shown. When the developer in the groove of the anilox roller 8Y is transferred to the surface of the developing roller 9Y at the nip between the developing roller 9Y and the anilox roller 8Y, the carrier oil existing in this peak also moves to the developing roller 9Y. As a result, the anilox roller pattern on the developing roller 9Y is easily relaxed.

  Even when the carrier oil application roller 22Y is brought into contact with the surface of the anilox roller 8Y, a mechanism for separating / contacting the carrier oil application roller 22Y described above is provided, and the carrier oil application roller 22Y is separated according to the toner concentration of the developer. The contact can be controlled.

  FIG. 7 shows a carrier oil application roller according to another embodiment of the present invention. In this embodiment, as a mechanism for supplying a liquid carrier to the developing roller 9Y, a carrier oil application roller 22Y made of a sponge-like material having numerous pores on the surface is used. As the sponge-like material having pores, porous polytetrafluoroethylene (trade name: Gore-Tex, manufactured by Japan Gore-Tex Co., Ltd.) disclosed in JP-A No. 2002-287551 is used. As the roller structure of the carrier oil application roller 22Y, the one disclosed in Japanese Patent Laid-Open No. 2002-287551 can be adopted.

  In this embodiment, an oil holding layer for holding carrier oil is provided in the roller, and the liquid carrier is supplied to the developing roller 9Y so as to exude the liquid carrier from the oil holding layer. As described above, since the liquid carrier from the oil retaining layer in the roller is used, it is not necessary to supply the liquid carrier to the carrier oil application roller 22Y through the pipe from the carrier storage unit 4Y. In addition, since the liquid carrier from the oil retaining layer is used up, the carrier oil application roller 22Y can be configured to be replaceable together with the cartridge when the developer storage unit is formed into a cartridge.

In FIG. 7, the carrier oil application roller 22Y is shown in contact with the developing roller 9Y. However, as described above, the carrier oil application roller 22Y may be in contact with the anilox roller 8Y. . Even when a sponge-like material is used as the carrier oil application roller 22Y, a mechanism for separating and contacting the carrier oil application roller 22Y is provided, and the carrier oil application roller 22Y is separated and contacted according to the toner concentration of the developer. Can be controlled.

1 is a diagram illustrating main components constituting an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which showed the main components of the developing unit. It is a perspective conceptual diagram showing the surface of the anilox roller 8Y. It is sectional drawing which shows the shape of the groove | channel provided in the anilox roller 8Y surface. It is a figure which shows a mode that the amount of liquid carriers is adjusted with a carrier oil application amount regulation blade. It is a figure which shows the state which contacted the carrier oil application roller 22Y to the anilox roller 8Y. It is a figure which shows the carrier oil application roller which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Carrier tank, 4Y ... Carrier storage part, 5Y ... Primary developer storage part, 6Y ... Secondary developer storage part, 7Y ... Agitation roller, 8Y ... Anilox roller, 9Y: Development roller, 10: Piping, 12Y: Photoconductor cleaning blade, 13Y: Photoconductor cleaning liquid recovery unit, 14Y: Development roller cleaning blade, 15Y: Residual developer recovery Part, 16Y ... squeeze roller, 17Y ... squeeze roller cleaning blade, 18Y ... carrier liquid recovery part, 19Y ... carrier oil application amount regulation blade, 21Y ... regulation blade, 22Y ... carrier Oil application roller, 23Y... Carrier oil application amount adjustment valve, 24Y... Carrier amount adjustment valve, 25Y. -Amount adjusting valve 2Y, 2M, 2C, 2K ... toner tank 3Y, 3M, 3C, 3K ... developer storage unit 20Y, 20M, 20C, 20K ... photoconductors 30Y, 30M, 30C, 30K ... Charging units 40Y, 40M, 40C, 40K ... Exposure unit optical paths 50Y, 50M, 50C, 50K ... Developing units 60Y, 60M, 60C, 60K ... Primary transfer unit 70 ... Intermediate transfer belt 80 ... Secondary transfer unit 90 ... Intermediate transfer belt cleaning unit

Claims (3)

In an image forming apparatus that forms an image using a developer in which toner is dispersed in a carrier,
A developing roller for developing the electrostatic latent image formed on the photoreceptor;
An anilox roller for supplying a liquid developer to the developing roller;
An image forming apparatus comprising: a carrier oil applying roller that contacts the developing roller or the anilox roller and applies a carrier. The image forming apparatus according to claim 1, wherein the carrier oil application roller is provided immediately before a nip formed by the developing roller and the anilox roller. A developer storage unit;
A toner concentration detection mechanism for detecting the toner concentration of the developer in the developer storage unit,
2. The mechanism according to claim 1, further comprising a mechanism for separating or abutting the carrier oil application roller with respect to the developing roller or the anilox roller in accordance with an output from the toner concentration detecting mechanism. Item 3. The image forming apparatus according to Item 2.

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