JP2013057811A - Cleaning device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device and an image forming apparatus in which the amount of toner taken by a cleaning brush member in the most downstream side can be reduced.SOLUTION: The cleaning device includes: a first cleaning brush member, which removes a normally-charged toner on a rotatable cleaning object; first voltage application means for applying voltage in the reverse polarity to the first cleaning brush member; a second cleaning brush member, which is disposed downstream the first cleaning brush member and removes a reversely-charged toner; second voltage application means for applying voltage in the normal charge polarity to the second cleaning brush member; a third cleaning brush member, which is disposed downstream the second cleaning brush member and removes a normally-charged toner; and third voltage applying means for applying voltage in the reverse polarity to the third cleaning brush member. The first voltage application means applies voltage in the reverse polarity that is large enough to reverse the charge polarity of the toner charged in the normal charge polarity into the reverse polarity to the first cleaning brush member.

Description

  The present invention relates to a cleaning device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the cleaning device.

  2. Description of the Related Art As an intermediate transfer belt cleaning device that removes transfer residual toner on an intermediate transfer belt in an intermediate transfer type image forming apparatus, a device that employs a cleaning device that removes toner using an electrostatic force is known.

  Patent Document 1 discloses a toner charged to a normal charged polarity of toner attached to an intermediate transfer belt that is rotatably stretched by a plurality of roller members, and a toner charged to a polarity opposite to the normal charged polarity of the toner. Has been described.

  The cleaning device includes a regular charged toner cleaning brush roller that removes toner charged to a normal charge polarity from the intermediate transfer belt, and a reverse charge toner cleaning brush roller that removes toner charged to a reverse polarity from the intermediate transfer belt. Is provided. At a position facing the regular charging toner cleaning brush roller, a regular charging toner cleaning facing roller in contact with the back surface of the intermediate transfer belt is grounded. In addition, a reversely charged toner cleaning counter roller is grounded at a position facing the reversely charged toner cleaning brush roller.

  Then, a voltage of the reverse polarity is applied to the regular charged toner cleaning brush roller by a power source. Then, between the regular charged toner cleaning brush roller and the regular charged toner cleaning counter roller, the regular charged toner on the intermediate transfer belt is attracted to the regular charged toner cleaning brush roller by electrostatic force due to the potential difference between the two. A strong electric field is formed. On the other hand, a voltage of the normal charging polarity is applied to the reversely charged toner cleaning brush roller by a power source. Then, the reversely charged toner on the intermediate transfer belt is attracted to the reversely charged toner cleaning brush roller by an electrostatic force between the reversely charged toner cleaning brush roller and the reversely charged toner cleaning counter roller due to the potential difference between the two. A strong electric field is formed.

  As a result, the toner charged to the regular charge polarity on the intermediate transfer belt is electrostatically attracted to the regular charge toner cleaning brush roller and removed from the intermediate transfer belt, and the toner charged to the reverse polarity is reversely charged toner cleaning brush. It is electrostatically attracted to the roller and removed from the intermediate transfer belt.

  In the image forming apparatus, a toner pattern is formed at a predetermined timing, and processing for improving image quality is performed. Specifically, a toner pattern is formed on the intermediate transfer belt at a predetermined timing, the toner pattern on the intermediate transfer belt is detected by an optical sensor or the like, and based on the detection result, image density adjustment and color overlay shift. To improve image quality. In addition, a toner pattern is formed between the sheets on the intermediate transfer belt and the toner in the developing device is refreshed to improve the image quality. The toner pattern formed on the intermediate transfer belt by such image quality improvement processing is not transferred from the intermediate transfer belt to a transfer body such as a recording paper, and is the same as the untransferred toner described above as untransferred toner. Removed with a cleaning device.

  However, in the cleaning device described in Patent Document 1, when an untransferred toner image having a large amount of toner adhered to the intermediate transfer belt, such as a toner pattern, is input, the toner cannot be completely removed from the intermediate transfer belt, resulting in poor cleaning. May occur.

  Accordingly, the inventors of the present application have developed a cleaning device in which three cleaning brush rollers are sequentially arranged in the rotational direction of the intermediate transfer belt in order to suppress the occurrence of such a cleaning failure. This cleaning device is provided with a pre-cleaning brush roller that is a first cleaning brush member that roughly removes toner of normal charging polarity on the most upstream side in the rotation direction of the intermediate transfer belt among the three cleaning brush rollers. A reversely charged toner cleaning brush roller, which is a second cleaning brush member for removing reversely charged toner, is provided downstream of the precleaning brush roller in the intermediate transfer belt rotation direction. Further, a regular charged toner cleaning brush roller, which is a third cleaning brush member for removing the toner of the regular charged polarity, is provided on the downstream side in the rotation direction of the intermediate transfer belt with respect to the reversely charged toner cleaning brush roller.

  As described above, by providing the pre-cleaning brush roller on the most upstream side in the rotation direction of the intermediate transfer belt among the three cleaning brush rollers, the toner of the regular charge polarity that occupies most of the toner constituting the untransferred toner image. Is roughly removed with a pre-cleaning brush roller. As a result, the amount of toner input to the reversely charged toner cleaning brush roller and the normally charged toner cleaning brush roller disposed downstream of the pre-cleaning brush roller in the intermediate transfer belt rotation direction is reduced. Therefore, the toner can be easily removed with the reversely charged toner cleaning brush roller or the regular charged toner cleaning brush roller, and the occurrence of defective cleaning can be suppressed.

  However, if the amount of untransferred toner is too large, the amount of toner input to the reversely charged toner cleaning brush roller or the regular charged toner cleaning brush roller will increase even if the toner is roughly removed by the precleaning brush roller. If a large amount of toner is input to the regular charged toner cleaning brush roller and a lot of toner is accumulated in the regular charged toner cleaning brush roller over time, the cleaning performance of the regular charged toner cleaning brush roller deteriorates.

  Here, even if the cleaning performance of the pre-cleaning brush roller or the reversely charged toner cleaning brush roller is deteriorated, the remaining cleaning brush roller provided on the downstream side in the rotation direction of the intermediate transfer belt with respect to the cleaning brush roller causes the intermediate transfer belt to remain on the intermediate transfer belt. The toner can be removed. On the other hand, among the three cleaning brush rollers, a cleaning brush roller is further provided on the downstream side in the intermediate transfer belt rotation direction than the regular charging toner cleaning brush roller provided on the most downstream side in the intermediate transfer belt rotation direction. Absent. Therefore, when the cleaning performance of the regular charged toner cleaning brush roller is lowered, there is a problem that the toner cannot be completely removed from the intermediate transfer belt and the cleaning property of the entire cleaning device is deteriorated.

  Up to now, the problem that occurs in the cleaning device that cleans the intermediate transfer belt has been described. However, the same problem may occur in the configuration in which the photosensitive member, the recording material conveyance belt, and the like are cleaned as the member to be cleaned.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a cleaning device capable of reducing toner input to the cleaning brush member on the most downstream side in the rotation direction of the cleaning target and the cleaning device. An image forming apparatus is provided.

  In order to achieve the above object, the invention of claim 1 is directed to a first cleaning brush member for electrostatically removing toner charged to a normal charge polarity on a rotatable member to be cleaned, and the first cleaning brush member. And a first voltage applying means for applying a voltage having a polarity opposite to the normal charging polarity, and being charged downstream of the first cleaning brush member in the rotation direction of the cleaning object and charged to the reverse polarity on the cleaning object. A second cleaning brush member that electrostatically removes the toner that has been removed; a second voltage applying unit that applies a voltage of the regular charge polarity to the second cleaning brush member; and a member to be cleaned than the second cleaning brush member. A third cleaning brush member which is provided on the downstream side in the rotation direction and electrostatically removes the toner charged to the regular charge polarity on the member to be cleaned; and the third cleaning brush And a third voltage applying unit that applies a voltage of the reverse polarity to the member, wherein the reverse polarity is such that the charge polarity of the toner charged to the normal charge polarity can be reversed to the reverse polarity. The voltage is applied to the first cleaning brush member by the first voltage applying means.

  In the present invention, the first voltage applying means applies a voltage having a reverse polarity such that the charging polarity of the toner charged to the normal charging polarity can be reversed to the reverse polarity. The toner charge distribution on the object to be cleaned that has not been removed by the one cleaning brush member is closer to the opposite polarity. As a result, the charge distribution of the toner input to the second cleaning brush member becomes closer to the reverse polarity, so the amount of the reverse polarity toner removed from the object to be cleaned by the second cleaning brush member can be increased accordingly. it can. Therefore, among the toner that has not been removed from the object to be cleaned by the first cleaning brush member, the amount of toner that is removed by the second cleaning brush member is increased, so that the toner that is input to the third cleaning brush member is reduced. be able to.

  As described above, according to the present invention, there is an excellent effect that toner input to the cleaning brush member on the most downstream side in the rotation direction of the cleaning target can be reduced.

6 is a graph showing the relationship between CL residual toner and charge amount (Q / M). FIG. 2 is a schematic configuration diagram illustrating a main part of the printer according to the first embodiment. FIG. 3 is an enlarged schematic configuration diagram in the vicinity of an intermediate transfer belt showing a gradation pattern and an optical sensor. FIG. 3 is an enlarged schematic view showing a chevron patch formed on the intermediate transfer belt. FIG. 4 is a schematic diagram of a toner consumption pattern transferred onto an intermediate transfer belt. The enlarged block diagram which expands and shows a belt cleaning apparatus and its periphery. The graph which shows the relationship between a brush applied voltage and the toner amount which the brush was not able to remove. FIG. 6 is a schematic diagram illustrating a maximum diameter MXLNG and a planar area AREA of a projected image with respect to a two-dimensional plane of toner particles. FIG. 4 is a schematic diagram for explaining a peripheral length PERI and a flat area AREA of a projected image with respect to a two-dimensional plane of toner particles. (A), (b), (c) is a figure which shows the shape of a toner typically, respectively. FIG. 3 is a schematic configuration diagram illustrating a main part of a tandem direct transfer printer according to a second embodiment.

[Embodiment 1]
Hereinafter, a so-called tandem type intermediate transfer type printer (hereinafter simply referred to as a printer) will be described as a first embodiment of an image forming apparatus to which the present invention is applied. First, the basic configuration of the printer will be described. FIG. 2 is a schematic configuration diagram illustrating a main part of the printer. The printer includes four process units 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). The four process units 6Y, 6M, 6C, and 6K have drum-shaped photoreceptors 1Y, 1M, 1C, and 1K, respectively. Around the photoreceptors 1Y, 1M, 1C, and 1K, charging devices 2Y, 2M, 2C, and 3K, developing devices 5Y, 5C, 1M, and 1K, drum cleaning devices 4Y, 4M, 4C, and 1K, a neutralization device (not shown) ) Etc. The process units 6Y, 6M, 6C, and 6K use Y, M, C, and K toners of different colors, but have the same configuration. Above the process units 6Y, 6M, 6C, and 6K, there is an optical writing unit (not shown) for irradiating the surface of the photoreceptors 1Y, 1M, 1C, and 1K with laser light L to write an electrostatic latent image. It is arranged.

  Below the process units 6Y, 6M, 6C, and 6K, a transfer unit 7 is disposed as a belt device including an endless intermediate transfer belt 8 that is a belt member. In addition to the intermediate transfer belt 8, a plurality of stretching rollers disposed inside the loop, a secondary transfer roller 18, a tension roller 16, a belt cleaning device 100, a lubricant application device 200, and the like disposed outside the loop. have.

  Inside the loop of the intermediate transfer belt 8, there are four primary transfer rollers 9Y, 9M, 9C, 9K, a driven roller 10, a drive roller 11, a secondary transfer counter roller 12, and three cleaning counter rollers 13, 14. 15 and an application brush opposing roller 17 are disposed. Each of these rollers functions as a stretching roller that stretches the intermediate transfer belt 8 around a part of its peripheral surface to stretch the belt. The cleaning counter rollers 13, 14, and 15 do not necessarily have to have a function of applying a constant tension, and may be driven to rotate as the intermediate transfer belt 8 rotates. The intermediate transfer belt 8 is moved endlessly in the clockwise direction in the drawing by the rotation of the driving roller 11 that is driven to rotate clockwise in the drawing by a driving means (not shown).

  The four primary transfer rollers 9Y, 9M, 9C, and 9K disposed inside the belt loop sandwich the intermediate transfer belt 8 between the photoreceptors 1Y, 1M, 1C, and 1K. As a result, primary transfer nips for Y, M, C, and K where the front surface of the intermediate transfer belt 8 and the photoreceptors 1Y, 1M, 1C, and 1K come into contact are formed. A primary transfer bias having a polarity opposite to that of the toner is applied to the primary transfer rollers 9Y, 9M, 9C, and 9K by a power source (not shown).

  Further, the intermediate transfer belt 8 is sandwiched between the secondary transfer counter roller 12 disposed inside the belt loop and the secondary transfer roller 18 disposed outside the belt loop. As a result, a secondary transfer nip where the front surface of the intermediate transfer belt 8 and the secondary transfer roller 18 abut is formed. Note that a secondary transfer bias having a polarity opposite to that of the toner is applied to the secondary transfer roller 18 by a power source (not shown). The paper transfer belt is bridged by the secondary transfer roller, several supporting rollers, and a driving roller, and the intermediate transfer belt 8 and the paper transfer belt are placed between the secondary transfer roller 18 and the secondary transfer counter roller 12. It is good also as a structure inserted | pinched.

  The three cleaning facing rollers 13, 14, and 15 disposed on the inner side of the belt loop are connected to the cleaning brush rollers 101, 104, and 107 of the belt cleaning device 100 disposed on the outer side of the belt loop. 8 is sandwiched. As a result, a cleaning nip is formed in which the front surface of the intermediate transfer belt 8 and the cleaning brush rollers 101, 104, and 107 come into contact with each other. The belt cleaning device 100 can be integrally replaced with the intermediate transfer belt 8. However, when the belt cleaning device 100 and the intermediate transfer belt 8 have different life settings, the belt cleaning device 100 is replaced with the intermediate transfer belt 8. May be independently detachable from the printer body. Details of the belt cleaning apparatus 100 will be described later.

  The printer includes a paper feed unit (not shown) having a paper feed cassette for storing the recording paper P and a paper feed roller for feeding the recording paper P from the paper feed cassette to the paper feed path. In addition, a registration roller pair (not shown) that receives the recording paper sent from the paper feeding unit and feeds it at a predetermined timing toward the secondary transfer nip is provided on the right side of the secondary transfer nip in the drawing. In addition, a fixing device (not shown) that receives the recording paper P sent out from the secondary transfer nip and fixes the toner image to the recording paper P is provided on the left side of the secondary transfer nip in the drawing. . Further, Y, M, C, and K toner supply devices (not shown) for supplying Y, M, C, and K toners to the developing devices 5Y, M, C, and K are provided as necessary.

  In recent years, in addition to plain paper that has been widely used as recording paper, special recording paper that is used for thermal transfer such as special paper having an uneven surface or iron print as a design has been increasingly used. When such special paper is used, transfer defects are more likely to occur when the toner image on the intermediate transfer belt 8 on which the color toners are superimposed is secondarily transferred onto the paper, as compared with conventional plain paper. Therefore, in the present printer, an elastic layer having low hardness is provided on the intermediate transfer belt 8 so that the toner layer and recording paper with poor smoothness can be deformed at the transfer nip portion. By providing the intermediate transfer belt 8 with an elastic layer having low hardness and making the intermediate transfer belt 8 elastic, the surface of the intermediate transfer belt 8 can be deformed following local irregularities. Thereby, without excessively increasing the transfer pressure with respect to the toner layer, good adhesion can be obtained, there is no loss of transfer of characters, and there is no transfer unevenness even on paper with poor smoothness, Transfer images with excellent uniformity can be obtained

  In this printer, the intermediate transfer belt 8 includes at least a base layer, an elastic layer, and a surface coat layer.

  Examples of the material used for the elastic layer of the intermediate transfer belt 8 include elastic members such as elastic material rubber and elastomer. Specifically, butyl rubber, fluorine rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene. Rubber, natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, polysulfide rubber, polynorbornene rubber, thermoplastic elastomer (for example, polystyrene series) , Polyolefins, polyvinyl chlorides, polyurethanes, polyamides, polyureas, polyesters, fluororesins) and the like can be used. However, it is not limited to the said material.

  The thickness of the elastic layer depends on the hardness and the layer structure, but is preferably in the range of 0.07 to 0.5 [mm]. More preferably, the range of 0.25-0.5 [mm] is good. Further, if the thickness of the intermediate transfer belt 8 is as thin as 0.07 [mm] or less, the pressure on the toner on the intermediate transfer belt 8 at the secondary transfer nip portion becomes high, and transfer deficiency is likely to occur. The toner transfer rate decreases.

  The hardness of the elastic layer is preferably 10 [°] ≦ HS ≦ 65 [°] (JIS-A). Although the optimum hardness differs depending on the layer thickness of the intermediate transfer belt 8, if the hardness is lower than 10 [°] (JIS-A), transfer deficiency tends to occur. On the other hand, when the hardness is higher than 65 [°] (JIS-A), it is difficult to stretch the roller, and since it is stretched by long-term stretching, there is no durability and early replacement is necessary. .

  The base layer of the intermediate transfer belt 8 is made of a resin with little elongation. Specifically, materials used for the base layer include polycarbonate, fluororesin (ETFE, PVDF, etc.), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, Styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer) Styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene) -Phenyl methacrylate copolymer, etc.), steel -Α-chloromethyl acrylate copolymer, styrene resin such as styrene-acrylonitrile-acrylate ester copolymer (monopolymer or copolymer containing styrene or styrene substitution product), methyl methacrylate resin, methacryl Acid butyl resin, ethyl acrylate resin, butyl acrylate resin, modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, chloride Pinyl-vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone Fat, ketone resins, ethylene - can be used ethyl acrylate copolymer, xylene resin and polyvinyl butyral resin, polyamide resin, one kind or two kinds or more selected from the group consisting of modified polyphenylene oxide resin. However, it is not limited to the said material.

  In addition, in order to prevent the elastic layer made of a rubber material having a large elongation from extending, a core layer made of a material such as a canvas may be provided between the base layer and the elastic layer. Examples of materials for preventing elongation used in the core layer include natural fibers such as cotton and silk, polyester fibers, nylon fibers, acrylic fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, and polyvinylidene chloride fibers. , One or more selected from the group consisting of synthetic fibers such as polyurethane fiber, polyacetal fiber, polyfluoroethylene fiber and phenol fiber, inorganic fibers such as carbon fiber and glass fiber, and metal fibers such as iron fiber and copper fiber Threaded or woven fabric can be used. Of course, the material is not limited to the above. The above-described yarn may be twisted in any manner, such as one or a plurality of filaments twisted, one-twisted yarn, various twisted yarns, double yarn, or the like. Further, for example, fibers of a material selected from the above material group may be blended. Of course, the yarn can be used after being subjected to an appropriate conductive treatment. On the other hand, the woven fabric can be any woven fabric such as knitted weave, and of course, a woven fabric that has been woven can also be used and can be subjected to a conductive treatment.

  The coat layer on the surface of the intermediate transfer belt 8 is for coating the surface of the elastic layer, and is composed of a layer having good smoothness. The material used for the coating layer is not particularly limited, but generally, a material that increases the secondary transferability by reducing the amount of toner adhering to the surface of the intermediate transfer belt 8 is used. For example, one or more of polyurethane, polyester, epoxy resin, etc., or a material that reduces surface energy and increases lubricity, such as fluororesin, fluorine compound, fluorocarbon, titanium oxide, silicon carbide, etc. One type or two or more types, or those having different particle sizes as required can be dispersed and used. Further, it is also possible to use a material such as a fluorine-based rubber material in which a heat treatment is performed to form a fluorine layer on the surface and the surface energy is reduced.

  If necessary, the base layer, the elastic layer, or the coating layer is, for example, carbon black, graphite, metal powder such as aluminum or nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, for the purpose of adjusting resistance. Conductive metal oxides such as potassium titanate, antimony oxide-tin oxide composite oxide (ATO), and indium oxide-tin oxide composite oxide (ITO) can be used. Here, the conductive metal oxide may be coated with insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate. However, it is not limited to the said material.

  The surface of the intermediate transfer belt 8 is coated with a lubricant by a lubricant coating device 200 in order to protect the belt surface. The lubricant application device 200 is a coating that abuts on the surface of the intermediate transfer belt 8 with a solid lubricant 202 such as a zinc stearate lump and a lubricant powder that comes into contact with the solid lubricant and is scraped off from the solid lubricant by rotation. And a coating brush roller 201 as a member.

  When image information is sent from a personal computer or the like, the printer rotates the drive roller 11 to move the intermediate transfer belt 8 endlessly. The stretching rollers other than the driving roller 11 are driven and rotated by the belt. At the same time, the photosensitive members 1Y, 1M, 1C, and 1K of the process units 6Y, 6M, 6C, and 6K are rotationally driven. Further, an electrostatic latent image is formed by irradiating the charged surface with laser light L while uniformly charging the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K with the charging devices 2Y, 2M, 2C, and 2K. To do. The electrostatic latent images formed on the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K are developed by the developing devices 5Y, 5M, 5C, and 5K, so that the Y, M on the photoreceptors 1Y, 1M, 1C, 1K are developed. , C, K toner images are obtained. The Y, M, C, and K toner images are primarily transferred while being superimposed on the front surface of the intermediate transfer belt 8 in the above-described primary transfer nips for Y, M, C, and K. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate transfer belt 8.

  On the other hand, in the paper feed unit, the recording paper P is sent out from the paper feed cassette one by one by the paper feed roller 27 and conveyed to the registration roller pair. Then, at a timing that can be synchronized with the four-color superimposed toner image on the intermediate transfer belt 8, the registration roller pair is driven to feed the recording paper P to the secondary transfer nip, and the four-color superimposed toner image on the belt is transferred. Batch transfer onto the recording paper P is performed. Thereby, a full-color image is formed on the surface of the recording paper P. The recording paper P after the formation of the full-color image is conveyed from the secondary transfer nip to a fixing device and subjected to a toner image fixing process.

  For the photoreceptors 1Y, M, C, and K after the Y, M, C, and K toner images are primarily transferred to the intermediate transfer belt 8, the remaining toner is cleaned by the drum cleaning devices 4Y, 4M, 4C, and 4K. Apply. Then, after neutralizing with a neutralizing lamp (not shown), it is uniformly charged with the charging devices 2Y, 2M, 2C, and 3K, and is ready for the next image formation. Further, the intermediate transfer belt 8 after the primary transfer to the recording paper P is subjected to a cleaning process for residual toner by the belt cleaning device 100.

  An optical sensor unit 150 is disposed on the right side of the K process unit 6K in the drawing so as to face the front surface of the intermediate transfer belt 8 with a predetermined gap. As shown in FIG. 3, the optical sensor unit 150 includes a Y optical sensor 151Y, a C optical sensor 151C, an M optical sensor 151M, and a K optical sensor 151K arranged in the width direction of the intermediate transfer belt 8. Each of these sensors is a reflection type photosensor, and reflects light emitted from a light emitting element (not shown) by a toner image on the front surface of the intermediate transfer belt 8 or the belt, and detects the amount of reflected light by a light receiving element (not shown). To do. A control unit (not shown) can detect the toner image on the intermediate transfer belt 8 or the image density (toner adhesion amount per unit area) based on the output voltage values from these sensors. .

In this printer, image density control for optimizing the image density of each color is executed when the power is turned on or every time a predetermined number of prints are performed.
In the image density control, first, gradation patterns Sk, Sm, Sc, and Sy of each color are automatically formed on the intermediate transfer belt 8 at positions facing the optical sensors 151Y, M, C, and K as shown in FIG. To do. The gradation pattern of each color is composed of 10 toner patches having an area of 2 [cm] × 2 [cm] having different image densities. The charging potentials of the photoreceptors 1Y, 1M, 1C, and 1K when creating the gradation patterns Sk, Sm, Sc, and Sy for each color are different from the uniform drum charging potential in the printing process and gradually increase in value. To do. Then, while forming a plurality of patch electrostatic latent images for forming a gradation pattern image on the photoreceptors 1Y, 1M, 1C, and 1K by scanning with laser light, they are used for Y, M, C, and K, respectively. Development is performed by the developing devices 5Y, 5M, 5C, and 5K. During this development, the value of the developing bias applied to the Y, M, C, and K developing rollers is gradually increased. By such development, gradation pattern images of Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. These are primarily transferred so as to be arranged at a predetermined interval in the main scanning direction of the intermediate transfer belt 8. At this time, the toner adhesion amount of the toner patch in the gradation pattern of each color is about 0.1 [mg / cm ² ] at the minimum and 0.55 [mg / cm ² ] at the maximum, and the toner Q / d distribution When measured, it is almost aligned with the regular charging polarity.

  Each toner pattern (Sk, Sm, Sc, Sy) formed on the intermediate transfer belt 8 passes through a position facing the optical sensor 151 as the intermediate transfer belt 8 moves endlessly. At this time, the optical sensor 151 receives an amount of light corresponding to the toner adhesion amount per unit area with respect to the toner patch of each gradation pattern.

  Next, the adhesion amount of each color toner pattern in each toner patch is calculated from the output voltage of the optical sensor 151 when each color toner patch is detected and the adhesion amount conversion algorithm, and the image forming condition is based on the calculated adhesion amount. Adjust. Specifically, a function (y = ax + b) indicating a straight line graph is calculated by regression analysis based on the result of detecting the toner adhesion amount on the toner patch and the development potential when each toner patch is imaged. Then, an appropriate development bias value is calculated by substituting a target value of image density into this function, and development bias values for Y, M, C, and K are specified.

  The memory stores an image forming condition data table in which several tens of development bias values and appropriate drum charging potentials individually corresponding to the values are associated in advance. For each of the process units 6Y, 6M, 6C, and 6K, a developing bias value closest to the specified developing bias value is selected from the image forming condition table, and the drum charging potential associated therewith is specified.

The printer also performs color misregistration correction processing when the power is turned on or whenever a predetermined number of prints are performed. In this color misregistration amount correction processing, Y, M, C, and K color toner images called chevron patches PV as shown in FIG. 4 are respectively provided at one end and the other end of the intermediate transfer belt 8 in the width direction. An image for color misregistration detection is formed. As shown in FIG. 4, the chevron patch PV has a predetermined pitch in the belt moving direction, which is the sub-scanning direction, with the toner images of each color of Y, M, C, and K inclined by about 45 [°] from the main scanning direction. Is a line pattern group arranged in. The amount of the chevron patch PV attached is about 0.3 [mg / cm ² ].

  By detecting each color toner image in the chevron patch PV formed at both ends in the width direction of the intermediate transfer belt 8, the position of each color toner image in the main scanning direction (photoconductor axial direction), the sub-scanning direction (belt movement) Direction) position, magnification error in the main scanning direction, and skew from the main scanning direction. The main scanning direction here refers to the direction in which the laser light is phased on the surface of the photosensitive member as it is reflected by the polygon mirror. For such Y, M, C toner images in the chevron patch PV, the optical sensor 151 reads the detection time difference from the K toner image. In the figure, the vertical direction of the paper surface corresponds to the main scanning direction, and after the Y, M, C, and K toner images are arranged in order from the left, the postures are different from those by 90 [°]. , Y toner images are further arranged. Based on the difference between the actual measurement value and the theoretical value of the detection time differences tyk, tmk, and tck with respect to K as the reference color, the shift amount in the sub-scanning direction of each color toner image, that is, the registration shift amount is obtained. Then, on the basis of the amount of registration deviation, the optical writing start timing for the photosensitive member 1 is corrected every other polygon mirror surface of the optical writing unit (not shown), that is, one scanning line pitch as one unit, and each color is corrected. To reduce the registration error of the toner image. Further, the inclination (skew) of each color toner image from the main scanning direction is obtained based on the difference in the amount of deviation in the sub-scanning direction between both ends of the belt. Based on the result, surface tilt correction of the optical system reflection mirror is performed to reduce skew of each color toner image. As described above, the color misregistration correction process is a process that corrects the optical writing start timing and surface tilt based on the detection timing of each toner image in the chevron patch PV to reduce registration deviation and skew deviation. By such a color misregistration correction process, it is possible to suppress the occurrence of color misregistration of an image due to a shift in the formation position of each color toner image with respect to the intermediate transfer belt 8 due to a temperature change or the like.

  Further, if the image forming operation with a low image area continues, the amount of old toner that stays in the developing device for a long time increases, so that the toner charging characteristics deteriorate and the image quality deteriorates when used for image formation (development capability decreases, Transferability decline). In order to prevent such old toner from staying in the developing device, the toner is discharged to a non-image area of the photosensitive member 1 at a fixed timing, and new toner is replenished to the developing device whose toner density has been lowered after the discharging to refresh the inside of the developing device. It has a refresh mode.

  A control unit (not shown) stores the toner consumption amount of each developing device 5Y, M, C, K and the operation time of each developing device 5Y, M, C, K, and at a predetermined timing, the developing device. Whether or not the toner consumption amount is equal to or less than the threshold value for the operation time of the predetermined period is checked for each developing device, and the refresh mode is executed for the developing device equal to or less than the threshold value.

When the refresh mode is executed, as shown in FIG. 5, a toner consumption pattern (a) is created in the non-image forming area corresponding to the space between the sheets of the photoconductor and transferred to the intermediate transfer belt 8. The adhesion amount of the toner consumption pattern (a) is determined based on the toner consumption amount with respect to the operation time of the developing device for a predetermined period, and the maximum adhesion amount per unit area is about 1.0 [mg / cm ² ]. There is. Further, when the toner Q / d distribution of the toner consumption pattern transferred to the intermediate transfer belt 8 is measured, it is almost aligned with the normal charging polarity.

  Each color gradation pattern, chevron patch, and toner consumption pattern formed on the intermediate transfer belt 8 are collected by the belt cleaning device 100. At this time, the belt cleaning device 100 must remove a large amount of toner from the intermediate transfer belt 8. However, in a conventional cleaning device comprising a polarity control means and a cleaning brush roller, a cleaning brush roller that removes positive polarity toner, and a cleaning brush roller that removes negative polarity toner, Untransferred toner images such as tone patterns, chevron patches, and toner consumption patterns could not be removed at once. In such a case, the toner on the intermediate transfer belt 8 that could not be cleaned may be transferred onto the recording paper during the next printing operation, resulting in an abnormal image.

  Therefore, the belt cleaning apparatus 100 of the printer is configured such that untransferred toner images such as each color gradation pattern, chevron patch, and toner consumption pattern can be removed at a time. A specific description will be given below.

  FIG. 6 is an enlarged configuration diagram showing the belt cleaning device 100 and its surroundings, which are characteristic points of the printer, in an enlarged manner.

  In FIG. 6, the belt cleaning device 100 has a pre-cleaning unit 100 a for roughly removing an untransferred toner image on the intermediate transfer belt 8, and a normal charging polarity (negative polarity) on the intermediate transfer belt 8. A reversely charged toner cleaning unit 100b that removes toner charged to a polarity (positive polarity) and a regular charged toner cleaning unit 100c that removes toner charged to a regular charged polarity on the intermediate transfer belt 8 are provided. Further, a transport screw 110 is provided as a transport means for transporting to a waste toner tank (not shown) provided in the image forming apparatus main body.

  The pre-cleaning unit 100a has a pre-cleaning brush roller 101 as a pre-cleaning brush member. Further, a pre-collecting roller 102 as a pre-collecting member that collects toner attached to the pre-cleaning brush roller 101, and a pre-scraping blade 103 as a pre-scraping member that contacts the pre-collecting roller 102 and scrapes the toner from the roller surface. have.

  Since most of the toner constituting the untransferred toner image is charged with a normal charging polarity (negative polarity), a voltage having a polarity (positive polarity) opposite to the normal charging polarity is applied to the pre-cleaning brush roller 101. The negative transfer toner on the intermediate transfer belt 8 is electrostatically removed. Further, a positive polarity voltage larger than that of the pre-cleaning brush roller 101 is applied to the pre-collection roller 102. In the belt cleaning device 100, a voltage to be applied to the pre-cleaning brush roller 101 is set so that 90% of the untransferred toner image is removed by the pre-cleaning brush roller 101.

  The reversely charged toner cleaning unit 100b is disposed downstream of the precleaning unit 100a in the moving direction of the intermediate transfer belt 8, and electrostatically charges toner charged to a polarity (positive polarity) opposite to the normal charging polarity (negative polarity) of the toner. The reversely charged toner cleaning brush roller 104 is a reversely charged toner cleaning brush member that is removed in an effective manner. Further, the reversely charged toner collecting roller 105 as a reversely charged toner collecting member for collecting the reversely charged toner attached to the reversely charged toner cleaning brush roller 104, and abutting against the reversely charged toner collecting roller 105 and scraping the reversely charged toner from the roller surface. A reversely charged toner scraping blade 106 is provided as a reversely charged toner scraping member. A negative voltage is applied to the reversely charged toner cleaning brush roller 104, and a negative voltage greater than that of the reversely charged toner cleaning brush roller 104 is applied to the reversely charged toner recovery roller 105. Further, the reversely charged toner cleaning unit 100b applies a negative charge to the toner on the intermediate transfer belt 8 so that the charge polarity of the toner on the intermediate transfer belt 8 is aligned with the normal charge polarity (negative polarity). It also has a function as a control means.

  The regular charging toner cleaning unit 100c is disposed downstream of the reverse charging toner cleaning unit 100b in the moving direction of the intermediate transfer belt 8, and is a regular charging toner cleaning brush member that electrostatically removes toner charged to the regular charging polarity. A charged toner cleaning brush roller 107 is provided. Further, the regular charged toner collecting roller 108 as a regular charged toner collecting member for collecting the regular charged toner attached to the regular charged toner cleaning brush roller 107 and the regular charged toner collecting roller 108 are abutted and scraped from the roller surface. A regular charged toner scraping blade 109 is provided as a regular charged toner scraping member. A positive voltage is applied to the normally charged toner cleaning brush roller 107, and a negative voltage greater than that of the normally charged toner cleaning brush roller 107 is applied to the normally charged toner recovery roller 108.

  As shown in FIG. 6, the cleaning units 100a, 100b, and 100c include cleaning power supply units 130, 132, and 134 for applying a voltage to the cleaning brush rollers 101, 104, and 107, and recovery rollers 102, 105, and 108, respectively. Are provided with recovery power supply units 131, 133, and 135 for applying a voltage to them. Each of the cleaning power supply units 130, 132, and 134 includes power supplies 130a, 132a, and 134a, and voltage detection units 130b, 132b, and 134b for detecting a voltage. Each of the recovery power supply units 131, 133, and 135 also includes power supplies 131a, 133a, and 135a, and voltage detection units 131b, 133b, and 135b for detecting a voltage.

  Further, the belt cleaning device 100 is provided with a polyurethane seal for preventing toner scattering. A first inlet seal 111a is disposed upstream of the precleaning unit 100a. A second inlet seal 111b is disposed upstream of the reversely charged toner cleaning unit 100b. A third inlet seal 111c is disposed upstream of the regular charged toner cleaning unit. Each of these inlet seals is disposed in contact with the intermediate transfer belt. By disposing these inlet seals upstream of the cleaning units, it is possible to prevent the toner accumulated in the cleaning units from leaking upstream.

  In addition, an insulating seal member 114 is provided at the outlet of the belt cleaning device 100. Thereby, scattering of toner from the normally charged toner cleaning brush roller 107 to the surroundings can be suppressed.

  The first inlet seal 111a, the second inlet seal 111b, the third inlet seal 111c, and the insulating seal member 114 also have a function of preventing leakage with the surroundings.

  Each of the cleaning brush rollers 101, 104, and 107 includes a metal rotary shaft member that is rotatably supported, and a brush portion that includes a plurality of raised brushes that are erected on the peripheral surface thereof. The diameter is φ15 to 17 [mm]. The raised nail has a two-layer core-sheath structure in which the inside is made of a conductive material such as conductive carbon and the surface portion is made of an insulating material such as polyester. As a result, the lead has substantially the same potential as the voltage applied to the cleaning brush roller, and the toner can be electrostatically attracted to the raised surface. As a result, the toner on the intermediate transfer belt 8 is electrostatically attached to the raised hair by the action of the voltage applied to the cleaning brush roller. Moreover, you may comprise the raising | fluff of each cleaning brush roller 101,104,107 only with a conductive fiber. Moreover, you may make it the so-called oblique hair planted in the attitude | position inclined with respect to the normal line direction of a rotating shaft member. Further, the raising of the pre-cleaning brush roller 101 and the regular charging toner cleaning brush roller 107 may be a core-sheath structure, and the raising of the reverse charging toner cleaning brush roller 104 may be composed of only conductive fibers. By forming the raising of the reversely charged toner cleaning brush roller 104 with only conductive fibers, charge injection from the reversely charged toner cleaning brush roller 104 to the toner is likely to occur. Therefore, the reversely charged toner cleaning brush roller 104 can satisfactorily align the toner on the intermediate transfer belt 8 with negative polarity. On the other hand, the brushing of the pre-cleaning brush roller 101 and the regular charging toner cleaning brush roller 107 has a core-sheath structure, so that charge injection into the toner can be suppressed, and the toner on the intermediate transfer belt 8 is charged positively. To suppress. Thereby, it is possible to prevent the pre-cleaning brush roller 101 and the normally charged toner cleaning brush roller 107 from generating toner that cannot be removed electrostatically.

  Further, each cleaning brush roller 101, 104, 107 bites into the intermediate transfer belt 8 by 1 [mm], and the brushing at the contact position by the driving means (not shown) is opposite to the moving direction of the intermediate transfer belt 8. Rotate to move in the direction (counter direction). By rotating the raised hair so as to move in the counter direction at the contact position, the linear velocity difference between the cleaning brush roller and the intermediate transfer belt 8 can be increased. This increases the probability of contact with the raised hair until a portion of the intermediate transfer belt 8 passes through the contact range with the cleaning brush roller, and the toner can be removed from the intermediate transfer belt 8 satisfactorily.

  In the belt cleaning device 100, stainless steel (SUS) rollers are used as the collection rollers 102, 105, and 108. Each of the collecting rollers 102, 105, and 108 may be made of any material as long as it can perform the function of transferring the toner adhering to the brush roller from the brush to the collecting roller by the potential gradient between the raised brush and the collecting roller. Absent. For example, each of the collecting rollers 102, 105, and 108 is covered with a high resistance elastic tube of several [μm] to 100 [μm] on a conductive core metal or further coated with an insulating coating, and the roller resistance is set to log R = 12 to You may use what was 13 [(ohm)]. By using a stainless steel (SUS) roller as each of the collecting rollers 102, 105, and 108, there are merits that the cost can be reduced, the applied voltage can be kept low, and the power can be saved. On the other hand, by setting the roller resistance to logR = 12 to 13 [Ω], the charge injection into the toner during the collection to the collection roller is suppressed, and the toner has the same polarity as the applied voltage of the collection roller. It can suppress that a recovery rate falls.

  The regular charging toner cleaning unit 100c is disposed downstream of the reverse charging toner cleaning unit 100b in the moving direction of the intermediate transfer belt 8, and is a regular charging toner cleaning brush member that electrostatically removes toner charged to the regular charging polarity. A charged toner cleaning brush roller 107 is provided. Further, the regular charged toner collecting roller 108 as a regular charged toner collecting member for collecting the regular charged toner attached to the regular charged toner cleaning brush roller 107 and the regular charged toner collecting roller 108 are abutted and scraped from the roller surface. A regular charged toner scraping blade 109 is provided as a regular charged toner scraping member. A positive voltage is applied to the normally charged toner cleaning brush roller 107, and a negative voltage greater than that of the normally charged toner cleaning brush roller 107 is applied to the normally charged toner recovery roller 108.

  Further, a flicker may be disposed in contact with each brush roller in order to collect the toner adhering to the brush roller. When the toner on the cleaning brush roller is blown off by the flicker and the toner remaining on the brush is electrostatically moved to the collecting roller, the amount of toner remaining on the brush is reduced, so that the cleaning performance of the brush itself is improved.

  Next, the pre-cleaning brush roller 101 and the pre-cleaning counter roller 13, the reverse charging toner cleaning brush roller 104 and the reverse charging toner cleaning counter roller 14, and the regular charging toner cleaning brush roller 107 and the normal charging toner cleaning counter roller 15 are arranged. The relationship will be described. Since the arrangement relationship between the cleaning brush rollers 101, 104, 107 and the cleaning counter rollers 13, 14, 15 in the cleaning units 100a, 100b, 100c is the same, in the following description, the pre-cleaning brush roller 101 and the pre-cleaning roller The arrangement relationship with the cleaning counter roller 13 will be described as an example.

  The pre-cleaning counter roller 13 is an aluminum roller having a diameter of 14 [mm], and is driven to rotate by a frictional force between the intermediate transfer belt 8 and its surface. The pre-cleaning facing roller 13 is connected to the ground.

The conditions of the cleaning brush rollers 101, 104, and 107 are as follows.
・ Brush material: Conductive polyester (Contains conductive carbon inside the fiber, the fiber surface is polyester, so-called core-sheath structure)
Brush resistance: 10 ⁶ to 10 ⁸ [Ω]
・ Brush flocking density: 100,000 [lines / inch ² ]
・ Brush fiber diameter: about 25 to 35 [μm]
-Brush tipping treatment: Yes-Brush diameter φ: 15-17 [mm]

  The applied voltage to the pre-cleaning brush roller 101 is set so that good cleaning performance can be obtained when an untransferred toner image having a large amount of toner attached to the intermediate transfer belt 8 is input. Further, the reversely charged toner cleaning brush roller 104 is set high so that electric charge is injected into the toner on the intermediate transfer belt 8. Further, the brush flocking density, brush resistance, fiber diameter, applied voltage, fiber type, and brush fiber biting amount can be optimized by the system, and thus are not limited thereto. Examples of the types of fibers that can be used include nylon, acrylic, and polyester.

The conditions of each collection roller 102, 105, 108 are as follows.
・ Recovery roller core material: SUS303-G8
-Surface roughness Ra of the pre-collection roller 102: 1.6
-Surface roughness Ra of reversely charged toner collecting roller 105: 0.4
-Regularly charged toner collecting roller 108 surface roughness Ra: 0.8
The collection roller material, brush fiber biting amount, applied voltage, and surface roughness Ra can be optimized by the system, and are not limited thereto.

The conditions of each scraping blade 103, 106, 109 are as follows.
・ Blade contact angle: 20 [°]
・ Blade thickness: 0.08 [mm]
・ Blade material: SUS304H
-Blade linear pressure on pre-collection roller: 69 [gf / cm]
-Blade linear pressure on the reversely charged toner collecting roller: 32 [gf / cm]
-Blade linear pressure on the regular charged toner collection roller: 46 [gf / cm]
The blade contact angle, the blade thickness, and the linear pressure on the collection roller can be optimized by the system, and are not limited thereto.

Next, the cleaning operation of the belt cleaning device 100 will be described.
As shown in FIG. 6, the untransferred toner image and the untransferred toner image that have passed through the secondary transfer portion pass through the contact portion of the first inlet seal 111a, and are rotated by the intermediate transfer belt 8 at the position of the pre-cleaning brush roller 101. Be transported. A voltage having a polarity (positive polarity) opposite to the normal charging polarity of the toner is applied to the pre-cleaning brush roller 101, and an electric field formed by a potential difference between the surface potential of the intermediate transfer belt 8 and the pre-cleaning brush roller 101. Thus, the negatively charged toner on the intermediate transfer belt 8 is electrostatically attracted and moved to the pre-cleaning brush roller 101. The negative polarity toner that has moved to the pre-cleaning brush roller 101 is transported to a contact position with the pre-collection roller 102 to which a positive voltage having a larger value than that of the pre-cleaning brush roller 101 is applied. Then, the toner that has moved onto the pre-cleaning brush roller 101 is electrostatically adsorbed by the electric field formed by the potential difference between the surface potential of the pre-cleaning brush roller 101 and the surface potential of the pre-collecting roller 102, and the pre-collecting roller 102 The negative toner that has been moved upward and moved to the pre-collection roller 102 is scraped off from the surface of the pre-collection roller by the pre-scraping blade 103. The toner scraped off by the pre-scraping blade 103 is discharged out of the apparatus by the transport screw 110.

  In this embodiment, the voltage to be applied to each cleaning brush roller and each collection roller is determined at the timing before image formation when the image forming apparatus is activated. However, the timing for determining the applied voltage is not limited to this, and it may be during a preparatory operation from after image formation to before the next image formation.

  In the present embodiment, there are at least two power output methods for the pre-cleaning brush roller 101: a case where residual transfer toner is input and a case where non-transferred toner is input in a refresh mode or the like.

First, a power output method when executing a transfer residual toner cleaning mode for removing transfer residual toner will be described.
A voltage to be applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102 when cleaning the transfer residual toner is determined. First, at a predetermined timing, a power source 131a is controlled at a constant current by a control unit (not shown) to supply a current of 20 [μA] to the pre-collecting roller 102, and the power source 130a is controlled at a constant current by the control unit and pre-cleaning is performed. A current of 10 [μA] is supplied to the brush roller 101 and a current of 30 [μA] is supplied to the pre-cleaning brush roller 101 and the pre-collection roller 102. Then, the voltage at that time is detected by the voltage detectors 130b and 131b and determined as voltages to be applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102, respectively. The voltage determined in this way is applied to the pre-cleaning brush roller 101 from the power source 130a controlled at a constant voltage by the controller when cleaning the transfer residual toner, and from the power source 131a controlled at a constant voltage by the controller. Apply to the pre-collection roller 102.

  Here, the value of the current that flows when determining the voltage to be applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102 is a value obtained in advance by experiments. The value of the current passed through the pre-cleaning brush roller 101 is a voltage at which an optimum current flows between the intermediate transfer belt 8 to which the transfer residual toner adheres and the pre-cleaning brush roller 101, and the pre-cleaning brush roller 101 without transfer residual toner. Is a current value that flows between the pre-cleaning brush roller 101 and the intermediate transfer belt 8 when applied to. The value of the current passed through the pre-collection roller 102 is the voltage when the optimum current flows between the pre-cleaning brush roller 101 and the pre-collection roller 102 with the transfer residual toner attached to the pre-collection roller 102. This is the current value that flows between the pre-cleaning brush roller 101 and the pre-collecting roller 102 when there is no transfer residual toner when applied.

Next, a power output method in the case of executing an untransferred toner cleaning mode for removing untransferred toner will be described.
When cleaning the untransferred toner, the control unit (not shown) controls the power supply 131a at a constant current so that a current of 45 [μA] flows through the pre-collection roller 102, and the control unit controls the power supply 130a at a constant current. A current of 15 [μA] is supplied to the pre-cleaning brush roller 101, and a current of 60 [μA] is supplied to the pre-cleaning brush roller 101 and the pre-collection roller 102.

  The total current of the pre-cleaning brush roller 101 and the pre-collecting roller 102 here is a current that flows from the pre-cleaning brush roller 101 to the intermediate transfer belt 8 when cleaning the untransferred toner. It has been found that the current flowing from the pre-cleaning brush roller 101 to the intermediate transfer belt 8 greatly affects the cleaning performance. Therefore, the control unit detects the current flowing from the pre-cleaning brush roller 101 to the intermediate transfer belt 8, and controls the power supply 130a and the power supply 131a so that the optimum current flows, whereby a good cleaning property can be obtained. .

  Here, the value of the current passed through the pre-cleaning brush roller 101 and the pre-collection roller 102 is a value obtained in advance by experiments. The value of the current that flows to the pre-cleaning brush roller 101 is the voltage at which an optimum current flows for cleaning between the intermediate transfer belt 8 to which the untransferred toner adheres and the pre-cleaning brush roller 101, and the pre-cleaning brush roller 101 without the untransferred toner. Is a current value that flows between the pre-cleaning brush roller 101 and the intermediate transfer belt 8 when applied to. Further, the value of the current that flows through the pre-collection roller 102 is the voltage when the optimum current for collection flows between the pre-cleaning brush roller 101 and the pre-collection roller 102 with the untransferred toner attached to the pre-collection roller 102. This is the current value that flows between the pre-cleaning brush roller 101 and the pre-collecting roller 102 when there is no untransferred toner when applied.

  Further, the power output of the pre-cleaning brush roller 101 and the pre-collecting roller 102 may be set by the following method.

First, a power output method when executing a transfer residual toner cleaning mode for removing transfer residual toner will be described.
At a predetermined timing, the pre-collection roller 102 is supplied with a voltage higher by +400 [V] than the voltage of the pre-cleaning brush roller 101, and the power source 130a and the power source 131a controlled by the control unit from the power source 130a and the pre-cleaning brush roller. A current of 30 [μA] is supplied in accordance with 101 and the pre-collection roller 102. Then, the voltage at that time is detected by the voltage detectors 130b and 131b and determined as voltages to be applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102, respectively. The voltage determined in this way is applied to the pre-cleaning brush roller 101 from the power source 130a controlled at a constant voltage by the controller when cleaning the transfer residual toner, and from the power source 131a controlled at a constant voltage by the controller. Apply to the pre-collection roller 102.

Next, a power output method in the case of executing an untransferred toner cleaning mode for removing untransferred toner will be described.
When cleaning the untransferred toner, the pre-collection roller 102 is applied with a voltage that is +400 [V] larger than the voltage of the pre-cleaning brush roller 101. A current of 60 [μA] is passed in accordance with the pre-cleaning brush roller 101 and the pre-collection roller 102. Thus, the total current of the pre-cleaning brush roller 101 and the pre-collecting roller 102 is the current that flows from the pre-cleaning brush roller 101 to the intermediate transfer belt 8 when cleaning the untransferred toner.

  At this time, the refresh mode image has a rectangular shape and a specific shape is calculated from the immediately preceding image area. The length in the main scanning direction (longitudinal direction) is constant at 260 [mm]. When performing the constant current control as described above, if the length in the longitudinal direction is not constant, the current flow into the non-image portion changes, and an appropriate cleaning electric field is not applied to the toner image. As a result, cleaning failure occurs.

  As described above, the voltage application method applied to the pre-cleaning brush roller 101 and the pre-collection roller 102 is changed between cleaning of residual toner and cleaning of untransferred toner such as in the refresh mode. Since the image distance in the longitudinal direction of the input toner is constant in the refresh mode, it is only necessary to supply a constant cleaning current. For this reason, even when resistance unevenness such as local hair fall occurs in the circumferential direction of the pre-cleaning brush roller 101 or when resistance unevenness occurs in the circumferential direction of the intermediate transfer member, it is preferable to flow a constant current. Cleaning is possible. In addition to this, even when resistance unevenness occurs in the circumferential direction due to adhesion unevenness of the adhesive that initially bonds the pre-cleaning brush roller 101 and the core metal, the effect is exhibited. In addition, the control time of the applied voltage is shortened, and even when a short-term system resistance change occurs, a constant current flows, so that an optimum cleaning operation can always be performed.

  The transfer residual toner has a different image area on the intermediate transfer belt 8, and therefore a bias that is constant current controlled so that a constant current flows between the intermediate transfer belt 8 and the pre-cleaning brush roller 101 is applied to the pre-cleaning brush. When applied to the roller 101, a current easily flows to a non-image portion having a smaller resistance than the image portion on the intermediate transfer belt 8, so that a current for removing the toner is insufficient and an appropriate cleaning electric field is not applied to the toner. As a result, defective cleaning occurs. Therefore, in this embodiment, as described above, a voltage at which an optimum cleaning current flows between the intermediate transfer belt 8 and the pre-cleaning brush roller 101 is determined in advance, and the determined voltage is transferred to the intermediate transfer belt 8. When the residual toner is removed, it is applied to the pre-cleaning brush roller 101 by constant voltage control to remove the transfer residual toner on the intermediate transfer belt 8, thereby obtaining good cleaning properties.

  Next, the negative toner, the positive toner, and the positive transfer residual toner of the untransferred toner image on the intermediate transfer belt 8 that could not be removed by the pre-cleaning brush roller 101 are placed at the position of the reversely charged toner cleaning brush roller 104. Be transported.

  The reversely charged toner cleaning brush roller 104 is applied with a voltage having the same polarity (negative polarity) as the normal charging polarity of the toner, and is formed by a potential difference between the intermediate transfer belt 8 and the surface potential of the reversely charged toner cleaning brush roller 104. The positively charged toner on the intermediate transfer belt 8 is electrostatically attracted and moved to the reversely charged toner cleaning brush roller 104 by the electric field. At the same time, the polarity of the toner on the intermediate transfer belt 8 is made negative by charge injection or discharge.

  The positive polarity toner that has moved to the reversely charged toner cleaning brush roller 104 is transferred to a contact position with the reversely charged toner recovery roller 105 to which a negative polarity voltage larger than that of the reversely charged toner cleaning brush roller 104 is applied. The The toner that has moved onto the reversely charged toner cleaning brush roller 104 is electrostatically adsorbed by an electric field formed by the potential difference between the surface potential of the reversely charged toner cleaning brush roller 104 and the surface potential of the reversely charged toner recovery roller 105. Then, the toner is moved onto the reversely charged toner collecting roller 105.

  The positive toner moved to the reversely charged toner collecting roller 105 is scraped off from the surface of the collecting roller by the reversely charged toner scraping blade 106.

  The voltage applied to the reversely charged toner cleaning brush roller 104 and the reversely charged toner recovery roller 105 is determined.

  In this embodiment, the intermediate transfer belt 8 rotates at 352 [mm / sec], and the distance in the intermediate transfer belt moving direction between the pre-cleaning brush roller 101 and the reversely charged toner cleaning brush roller 104 is 20 [mm. ]. In this embodiment, the reversely charged toner is 20 [mm] ÷ 352 [mm / sec] = 0.06 [sec] after the voltage applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102 is determined. The voltage applied to the cleaning brush roller 104 and the reversely charged toner collecting roller 105 is determined. At this time, the voltage is continuously applied to the pre-cleaning brush roller 101 and the pre-collection roller 102. In this way, the effect of the electric charge applied to the intermediate transfer belt 8 from the pre-cleaning brush roller 101 and the pre-collecting roller 102 is taken into consideration, and then applied to the reversely charged toner cleaning brush roller 104 and the reversely charged toner collecting roller 105. The voltage to be determined can be determined.

A method of outputting power when executing the transfer residual toner cleaning mode and the non-transfer toner cleaning mode will be described.
First, a voltage to be applied to the reversely charged toner cleaning brush roller 104 and the reversely charged toner collecting roller 105 when cleaning the untransferred toner and the untransferred toner is determined. At a predetermined timing, the control unit (not shown) controls the power source 133a at a constant current to flow a current of −20 [μA] to the reversely charged toner collecting roller 105, and the control unit controls the power source 132a at a constant current and reverses the current. A current of −7 [μA] is supplied to the charged toner cleaning brush roller 104, and a current of −27 [μA] is supplied to the reversely charged toner cleaning brush roller 104 and the reversely charged toner recovery roller 105. The voltage at that time is detected by the voltage detectors 132b and 133b and determined as voltages to be applied to the reversely charged toner cleaning brush roller 104 and the reversely charged toner recovery roller 105, respectively. The voltage determined in this way is applied to the reversely charged toner cleaning brush roller 104 from the power supply 132a controlled at the constant voltage by the control unit when cleaning the untransferred toner and the untransferred toner, and the control unit supplies the constant voltage. The toner is applied to the reversely charged toner collecting roller 105 from the controlled power source 133a.

  Next, the toner that has been shifted to the negative polarity by the reversely charged toner cleaning brush roller 104 and the negative polarity toner that could not be removed by the pre-cleaning brush roller 101 are transferred to the regular charged toner cleaning brush roller 107 by the rotation of the intermediate transfer belt 8. Be transported. The polarity of the toner transferred to the normally charged toner cleaning brush roller 107 is negatively controlled by the reversely charged toner cleaning brush roller 104. Further, the toner on the intermediate transfer belt 8 is almost removed by the pre-cleaning brush roller 101 and the reversely charged toner cleaning brush roller 104. Therefore, a very small amount of toner is transferred to the regular charged toner cleaning brush roller 107.

  Regularly charged toner cleaning brush roller 107 has a negative polarity, and a very small amount of toner on intermediate transfer belt 8 is applied with a voltage having a polarity (positive polarity) opposite to the normal charged polarity of the toner. The toner is electrostatically attached to the charged toner cleaning brush roller 107, collected from the regular charged toner cleaning brush roller 107 to the regular charged toner collecting roller 108, and scraped off from the regular charged toner collecting roller 108 by the regular charged toner scraping blade 109. It is.

  The voltage to be applied to the normally charged toner cleaning brush roller 107 and the normally charged toner collecting roller 108 is determined. In this embodiment, the distance in the moving direction of the intermediate transfer belt between the reversely charged toner cleaning brush roller 104 and the regular charged toner cleaning brush roller 107 is 20 [mm]. Regularly charged toner cleaning brush roller 107 after 20 [mm] ÷ 352 [mm / sec] = 0.06 [sec] after the voltage applied to reversely charged toner cleaning brush roller 104 and reversely charged toner collecting roller 105 is determined. The voltage applied to the normally charged toner collecting roller 108 is determined. At this time, the voltage continues to be applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102, the reversely charged toner cleaning brush roller 104 and the reversely charged toner collecting roller 105. By doing so, the influence of the charge applied to the intermediate transfer belt 8 from the pre-cleaning brush roller 101 and the pre-collecting roller 102 and the application from the reversely charged toner cleaning brush roller 104 and the reversely charged toner collecting roller 105 to the intermediate transfer belt 8 are achieved. The voltage applied to the normally charged toner cleaning brush roller 107 and the normally charged toner collecting roller 108 can be determined in consideration of the influence of the charged charges.

A method of outputting power when executing the transfer residual toner cleaning mode and the non-transfer toner cleaning mode will be described.
First, a voltage to be applied to the regular charged toner cleaning brush roller 107 and the regular charged toner collection roller 108 when the untransferred toner and untransferred toner are cleaned is determined. At a predetermined timing, a control unit (not shown) performs constant current control of the power source 135a to cause a current of 13 [μA] to flow through the normally charged toner collecting roller 108, and the control unit controls constant current of the power source 134a to perform normal charging. A current of 6 [μA] is supplied to the toner cleaning brush roller 107, and a current of 19 [μA] is supplied to the regular charged toner cleaning brush roller 107 and the normal charged toner recovery roller 108. The voltage at that time is detected by the voltage detectors 134b and 135b, and determined as voltages to be applied to the regular charged toner cleaning brush roller 107 and the regular charged toner collection roller 108, respectively. The voltage thus determined is applied to the normally charged toner cleaning brush roller 107 from the power supply 134a controlled at the constant voltage by the control unit when cleaning the untransferred toner and the untransferred toner, and the control unit supplies the constant voltage. The toner is applied to the regular charged toner collecting roller 108 from the controlled power source 135a.

  The voltage applied to the pre-cleaning brush roller 101, the pre-collecting roller 102, the reversely charged toner cleaning brush roller 104, the reversely charged toner collecting roller 105, the regular charged toner cleaning brush roller 107, and the regular charged toner collecting roller 108 is determined. The predetermined timing is recalculated every time a predetermined number of transfer materials are passed. In the present embodiment, the predetermined number is set to 100, but is not limited to this number. The predetermined timing may be recalculated at the end of the printing operation or may be before the printing operation. In addition, it is recalculated when the usage environment changes or when it does not operate for a long time.

  As described above, according to the belt cleaning device 100, by providing the pre-cleaning brush roller 101, the negative-polarity toner that covers most of the untransferred toner image by the pre-cleaning brush roller 101 is roughly removed. As a result, the amount of toner input to the reversely charged toner cleaning brush roller 104 and the normally charged toner cleaning brush roller 107 can be reduced. The toner on the intermediate transfer belt 8 transferred to the regular charged toner cleaning brush roller 107 at the most downstream in the intermediate transfer belt moving direction has not been removed by the pre-cleaning brush roller 101 or the reversely charged toner cleaning brush roller 104. The amount of toner is very small. Further, the toner is negatively aligned by the reversely charged toner cleaning brush roller 104. Therefore, the remaining toner can be satisfactorily removed by the normally charged toner cleaning brush roller 107. As a result, even an untransferred toner image in which a large amount of toner is attached to the intermediate transfer belt 8 can be satisfactorily removed from the intermediate transfer belt 8.

  Further, the transfer residual toner having a smaller amount of toner than the untransferred toner image can be satisfactorily removed by the pre-cleaning brush roller 101, the reversely charged toner cleaning brush roller 104, and the regular charged toner cleaning brush roller 107.

  Further, even if the resistance value of the intermediate transfer belt 8 or each of the cleaning brush rollers 101, 104, and 107 changes due to environmental changes and deterioration with time, it is possible to apply an optimum voltage for cleaning. . However, each cleaning brush roller 101, 104, 107 or each collection roller depends on a change in the rotational speed of the intermediate transfer belt 8, each cleaning brush roller 101, 104, 107, each collection roller 102, 105, 108, etc. Since the optimum current value for the cleaning that flows in 102, 105, and 108 is different, it is not limited to this.

  Further, the belt cleaning device 100 removes positive toner on the intermediate transfer belt 8 by the reversely charged toner cleaning brush roller 104, but the reverse charge toner cleaning unit 100b performs polarity control so that the toner has a negative polarity. In other words, the positive toner on the intermediate transfer belt 8 may not be removed. In this case, the toner on the intermediate transfer belt 8 that has passed through the pre-cleaning brush roller 101 is aligned to a negative polarity by the polarity control unit, and is a regular charged toner cleaning brush that is downstream of the polarity control unit in the direction of movement of the intermediate transfer belt. It is transferred to the roller 107. Then, the negatively charged toner is removed by the normally charged toner cleaning brush roller 107.

  As a means for injecting negative charge into the toner on the intermediate transfer belt 8 in the polarity control unit, a conductive brush, a conductive blade, a corona charger, or the like may be used. Also, instead of aligning the charging polarity of the toner to negative polarity, arrange a cleaning brush roller to which a negative voltage is applied downstream of the polarity control unit in the belt moving direction so that it is aligned to positive polarity. A configuration in which toner having the same positive polarity on the intermediate transfer belt 8 is removed may be employed. Even in such a configuration, since the toner of the untransferred toner image is roughly removed from the intermediate transfer belt 8 by the pre-cleaning brush roller 101, the amount of toner transferred to the polarity control unit is reduced. Therefore, the polarity control unit can satisfactorily align the toner on the intermediate transfer belt 8 with one polarity. As a result, the toner on the intermediate transfer belt 8 can be satisfactorily electrostatically removed by the cleaning brush roller disposed downstream of the polarity control unit in the intermediate transfer belt moving direction. Therefore, even if an untransferred toner image to which a large amount of toner is attached is input to the belt cleaning device 100, it can be satisfactorily cleaned.

  In the belt cleaning device 100, a voltage is applied to each of the collecting rollers 102, 105, and 108 and each of the cleaning brush rollers 101, 104, and 107. A configuration in which a voltage is applied only to the collection rollers 102, 105, and 108 may be employed. In this case, a bias voltage somewhat lower than the bias voltage applied to the recovery roller is applied to the cleaning brush roller in a form through the contact portion with the recovery roller due to a potential drop due to the fiber resistance of the cleaning brush roller. It becomes a state. Thereby, a potential difference is formed between the collection roller and the cleaning brush roller, and the toner can be electrostatically moved from the cleaning brush roller to the collection roller by a potential gradient in the direction of the collection roller.

[Example 1]
FIG. 7 shows the relationship between the brush applied voltage and the amount of toner that could not be removed by the brush.
Only one brush is set, and a certain amount of solid pattern is removed with this brush, and the amount of toner remaining on the belt is measured. A voltage obtained by adding 400 [V] from the brush shaft is applied to the collection roller. The horizontal axis represents the voltage applied to the brush shaft, and the vertical axis represents the amount of toner remaining on the belt. The graph is convex downward, and the applied voltage on the right side of the lowest point A is reverse adhesion. At this time, the applied voltage is as follows. The process linear velocity is 600 [mm / s].

  In the present embodiment, the pre-cleaning brush roller 101 uses the pre-cleaning brush roller 101 and the intermediate transfer belt 8 in consideration of variations in resistance, power supply bias fluctuation (about 5% of power output fluctuation), and the like. The pre-cleaning brush roller 101 has a voltage value of 10 to 20% on the positive polarity side from the lowest point so that substantially all the toner that could not be removed from the intermediate transfer belt 8 is charged to the positive polarity. Is applied.

Pre-cleaning brush roller 101: +2400 [V]
Pre-collection roller 102: +2800 [V]
Reverse charged toner cleaning brush roller 104: -2600 [V]
・ Reversely charged toner collecting roller 105: -3000 [V]
Regularly charged toner cleaning brush roller 107: +1000 [V]
Regularly charged toner collection roller 108: +1400 [V]

FIG. 1 shows the relationship between the amount of toner remaining on the intermediate transfer belt 8 after cleaning by the pre-cleaning brush roller 101 (CL residual toner) and the amount of toner charge (Q / M). The amount of toner input to the pre-cleaning brush roller 101 is about 1.0 [mg / cm ² ], and the charge amount (Q / M) of the toner is about −50 [μC / g].

  As can be seen from FIG. 1, when the current passed through the pre-cleaning brush roller 101 is +87 [μA], the amount of CL remaining toner is minimized, and the toner charge amount (Q / M) is approximately 0 [μC / g]. . If the current passed through the pre-cleaning brush roller 101 is further increased, the toner charge amount (Q / M) becomes positive. That is, at a current of +87 [μA] or more, the charging polarity of the toner removed by the pre-cleaning brush roller 101 is reversed from the negative polarity to change to the positive polarity. At this time, it is considered that a part of the toner removed by the pre-cleaning brush roller 101 returns to the intermediate transfer belt 8 and adheres in reverse.

  By setting the voltage applied to the pre-cleaning brush roller 101 to a reverse adhesion voltage, the polarity distribution of the toner entering the reversely charged toner cleaning brush roller 104 becomes closer to the positive polarity, and a large amount is collected by the reversely charged toner cleaning brush roller 104. . As a result, the amount of toner input to the normally charged toner cleaning brush roller 107 can be reduced. Therefore, the amount of toner accumulated on the regular charging toner cleaning brush roller 107 with time decreases, and the deterioration of the cleaning performance of the regular charging toner cleaning brush roller can be suppressed, and deterioration of the cleaning performance of the entire cleaning device can be suppressed.

[Example 2]
In this embodiment, when there is discharged toner discharged from the developing device 5 between the sheets on the intermediate transfer belt 8 (non-image portion) in the refresh mode, the pre-cleaning brush roller 101 is applied when the discharged toner is removed. The voltage is changed from when the transfer residual toner is removed, and the voltage when removing the discharged toner is set to a voltage that is reversely attached.

  In each of the cleaning rollers 101, 104, 107 and each of the collection rollers 102, 105, 108, a voltage to be applied when removing the transfer residual toner from the intermediate transfer belt 8 and a toner discharged from the intermediate transfer belt 8 are removed. The applied voltage is as follows. The process linear velocity is 600 [mm / s].

・ Pre-cleaning brush roller 101
When removing transfer residual toner: +2400 [V]
When discharging toner is removed: +3000 [V]
・ Pre-collection roller 102
When removing residual toner: +2800 [V]
When discharging toner is removed: +3400 [V]
・ Reversely charged toner cleaning brush roller 104
When removing transfer residual toner and discharging toner: -2600 [V]
・ Reversely charged toner collection roller 105
When removing transfer residual toner and discharging toner: -3000 [V]
Regularly charged toner cleaning brush roller 107
When removing transfer residual toner and discharging toner: +1000 [V]
Regularly charged toner collection roller 108
When removing transfer residual toner and discharging toner: +1400 [V]

  Although the charge polarity of the discharged toner is a negative polarity, the polarity distribution of the discharged toner becomes closer to the positive polarity by setting the voltage to be reversely attached to the pre-cleaning brush roller 101. Therefore, most of the discharged toner that could not be removed from the intermediate transfer belt 8 by the pre-cleaning brush roller 101 is collected by the reversely charged toner cleaning brush roller 104. As a result, the amount of toner input to the normally charged toner cleaning brush roller 107 can be reduced. Therefore, the amount of toner accumulated on the regular charging toner cleaning brush roller 107 with time decreases, and the deterioration of the cleaning performance of the regular charging toner cleaning brush roller can be suppressed, and deterioration of the cleaning performance of the entire cleaning device can be suppressed. At this time, the applied voltage is as follows.

[Example 3]
In this embodiment, when the transfer residual toner is removed from the intermediate transfer belt 8 (normal time), a voltage at the lowest point A in FIG. 7 is applied to the pre-cleaning brush roller 101, and the developing device 5 is in the refresh mode. When the discharged toner discharged from the intermediate transfer belt 8 to the intermediate transfer belt 8 is removed from the intermediate transfer belt 8, a voltage that causes reverse adhesion is applied.

  In each of the cleaning rollers 101, 104, 107 and each of the collection rollers 102, 105, 108, a voltage to be applied when removing the transfer residual toner from the intermediate transfer belt 8 and a toner discharged from the intermediate transfer belt 8 are removed. The applied voltage is as follows. The process linear velocity is 600 [mm / s].

・ Pre-cleaning brush roller 101
When removing transfer residual toner: +1700 [V]
When discharging toner is removed: +3000 [V]
・ Pre-collection roller 102
When removing transfer residual toner: +2100 [V]
When discharging toner is removed: +3400 [V]
・ Reversely charged toner cleaning brush roller 104
When removing transfer residual toner and discharging toner: -2600 [V]
・ Reversely charged toner collection roller 105
When removing transfer residual toner and discharging toner: -3000 [V]
Regularly charged toner cleaning brush roller 107
When removing transfer residual toner and discharging toner: +1000 [V]
Regularly charged toner collection roller 108
When removing transfer residual toner and discharging toner: +1400 [V]

  The amount of toner remaining after transfer varies depending on the image pattern. For example, there is less transfer residual toner for characters and lines than for solid portions. When a voltage that causes reverse adhesion is applied to the pre-cleaning brush roller 101, the polarity distribution of the transfer residual toner of the character or line that enters the reversely charged toner cleaning brush roller 104 becomes strongly positive. As a result, the transfer residual toner is hardly removed by the reversely charged toner cleaning brush roller 104. This is because the adhesive force between the toner and the intermediate transfer belt 8 becomes too strong. Therefore, in this embodiment, when the transfer residual toner is removed from the intermediate transfer belt 8 (normal time), a voltage that is the lowest point A in FIG. 7 is applied to the pre-cleaning brush roller 101. As a result, the polarity distribution of the transfer residual toner of characters and lines entering the reversely charged toner cleaning brush roller 104 can be suppressed from becoming strongly positive and the transfer residual toner can be removed favorably by the reversely charged toner cleaning brush roller 104. can do.

Next, toner that is preferably used in the printer will be described.
The toner suitably used in this printer preferably has a volume average particle diameter of 3 to 6 [μm] in order to reproduce minute dots of 600 [dpi] or more. A toner having a ratio (Dv / Dn) of volume average particle diameter (Dv) to number average particle diameter (Dn) in the range of 1.00 to 1.40 is preferable. The closer (Dv / Dn) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

  The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. FIG. 8 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is expressed by the following formula 1. This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.

  When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

  FIG. 9 is a diagram schematically illustrating the shape of the toner in order to explain the shape factor SF-2. The shape factor SF-2 indicates the ratio of unevenness in the shape of the toner, and is expressed by the following formula 2. A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100 / (4π).

  When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

  Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated. When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  In addition, a toner suitably used for a color printer is a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent are dispersed in an organic solvent. Is a toner obtained by carrying out at least one of crosslinking and elongation reaction in an aqueous solvent. Hereinafter, the constituent material and the manufacturing method of the toner will be described.

(polyester)
The polyester is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include dihydric alcohol (DIO) and trihydric or higher polyhydric alcohol (TO). (DIO) alone or a mixture of (DIO) and a small amount of (TO) preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among them, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

  Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC). (DIC) alone and (DIC) with a small amount of (TC) Mixtures are preferred. Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).

  The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1. The polycondensation reaction between polyhydric alcohol (PO) and polycarboxylic acid (PC) is heated to 150 to 280 [° C.] in the presence of a known esterification catalyst such as tetrabutoxy titanate or dibutyltin oxide, and reduced in pressure as necessary. The produced water is distilled off to obtain a polyester having a hydroxyl group. The hydroxyl value of the polyester is preferably 5 or more, and the acid value of the polyester is usually 1 to 30, preferably 5 to 20. By giving an acid value, it tends to be negatively charged, and furthermore, when fixing to a recording paper, the affinity between the recording paper and the toner is good and the low-temperature fixability is improved. However, when the acid value exceeds 30, there is a tendency to deteriorate with respect to the stability of charging, particularly environmental fluctuation. The weight average molecular weight is 10,000 to 400,000, preferably 20,000 to 200,000. A weight average molecular weight of less than 10,000 is not preferable because offset resistance deteriorates. On the other hand, if it exceeds 400,000, the low-temperature fixability is deteriorated.

  In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting a terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines. Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-isocyanatomethyl caproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; phenol derivatives, oximes, caprolactam And a combination of two or more of these. The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5/1, the low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1/1, when a urea-modified polyester is used, the urea content in the ester becomes low and hot offset resistance deteriorates. The content of the polyisocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 [wt%], preferably 1 to 30 [wt%], more preferably 2 to 20 [wt%]. If it is less than 0.5 [wt%], the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 [wt%], the low-temperature fixability deteriorates. The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester will be low, and the hot offset resistance will deteriorate.

  Next, as amines (B) to be reacted with the polyester prepolymer (A), a divalent amine compound (B1), a trivalent or higher polyvalent amine compound (B2), an amino alcohol (B3), an amino mercaptan (B4) ), Amino acid (B5), and amino acid block of B1 to B5 (B6).

  Examples of the divalent amine compound (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′-diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′-dimethyldicyclohexyl). Methane, diamine cyclohexane, isophorone diamine, etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine, etc.) and the like. Examples of the trivalent or higher polyvalent amine compound (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan. Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the compound (B6) obtained by blocking the amino group of B1 to B5 include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

  The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2. When [NCO] / [NHx] is more than 2/1 or less than 1/2, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.

  The urea-modified polyester may contain a urethane bond together with a urea bond. The molar ratio of the urea bond content to the urethane bond content is usually 100/0 to 10/90, preferably 80/20 to 20/80, and more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated.

  The urea-modified polyester is produced by a one-shot method or the like. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150 to 280 [° C.] in the presence of a known esterification catalyst such as tetrabutoxy titanate and dibutyltin oxide, and are produced while reducing the pressure if necessary Water is distilled off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with polyvalent isocyanate (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, this (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a urea-modified polyester.

  When reacting (PIC) and when reacting (A) and (B), a solvent may be used if necessary. Usable solvents include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.) and ethers And those inert to isocyanates (PIC), such as tetrahydrofuran (such as tetrahydrofuran).

  In addition, in the crosslinking and / or extension reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator can be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those obtained by blocking them (ketimine compounds).

  The weight average molecular weight of the urea-modified polyester is usually 10,000 or more, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. If it is less than 10,000, the hot offset resistance deteriorates. The number average molecular weight of the urea-modified polyester or the like is not particularly limited when the above-mentioned unmodified polyester is used, and may be a number average molecular weight that can be easily obtained to obtain the weight average molecular weight. When the urea-modified polyester is used alone, its number average molecular weight is usually 2000-15000, preferably 2000-10000, more preferably 2000-8000. When it exceeds 20000, the low-temperature fixability and the glossiness when used in a full-color image forming apparatus are deteriorated.

  By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the glossiness when used in a full-color image forming apparatus are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.

  The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.

  The weight ratio of unmodified polyester to urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.

  The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 [° C.], preferably 45 to 60 [° C.]. If the temperature is less than 45 [° C.], the heat resistance of the toner deteriorates, and if it exceeds 65 [° C.], the low-temperature fixability becomes insufficient.

  In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

(Coloring agent)
As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher , Lead yellow, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR1, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R) , Tartrazine rake, quinoline yellow rake, anthrazan yellow BGL, isoindolinone yellow, bengara, red lead, lead vermilion, cadmium red, cadmium mercurial red, antimon vermilion, permanent red 4R, para red, phissa red Parachlor ortho nitro Nirin Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine B, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, Riazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalo Cyanine green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The content of the colorant is usually 1 to 15 [wt%], preferably 3 to 10 [wt%] based on the toner.

  The colorant can also be used as a master batch combined with a resin. As a binder resin to be kneaded together with the production of the master batch or the master batch, a polymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyl toluene or the like, or a copolymer of these and a vinyl compound, Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be mentioned, and these can be used alone or in combination.

(Charge control agent)
Known charge control agents can be used, such as nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified 4 Secondary ammonium salts or compounds, tungsten simple substances or compounds, fluorine activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives. Specifically, Bontron 03 of a nigrosine dye, Bontron P-51 of a quaternary ammonium salt, Bontron S-34 of a metal-containing azo dye, E-82 of an oxynaphthoic acid metal complex, E-84 of a salicylic acid metal complex , Phenolic condensate E-89 (above, Orient Chemical Industries, Ltd.), quaternary ammonium salt molybdenum complex TP-302, TP-415 (above, Hodogaya Chemical Co., Ltd.), quaternary ammonium salt copy Charge PSYVP2038, copy blue PR of triphenylmethane derivative, copy charge NEG VP2036 of quaternary ammonium salt, copy charge NX VP434 (manufactured by Hoechst), LR1-901, LR-147 which is a boron complex (manufactured by Nippon Carlit) ), Copper phthalocyanine, perylene, quinacridone, azo face , Sulfonate group, carboxyl group, and polymer compounds having a functional group such as quaternary ammonium salts. Of these, substances that control the negative polarity of the toner are particularly preferably used.

  The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 0.2 to 5 parts by weight is preferable. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the charge control agent is reduced, the electrostatic attraction with the developing roller is increased, the developer fluidity is lowered, and the image density is lowered. Invite.

(Release agent)
As a release agent, a low melting point wax having a melting point of 50 to 120 [° C.] works more effectively as a release agent in the dispersion with the binder resin between the fixing roller and the toner interface. Effective against high temperature offset without applying a release agent such as oil to the fixing roller. Examples of such a wax component include the following. Examples of waxes and waxes include plant waxes such as carnauba wax, cotton wax, wood wax and rice wax, animal waxes such as beeswax and lanolin, mineral waxes such as ozokerite and cercin, and paraffin, microcrystalline, And petroleum waxes such as petrolatum. In addition to these natural waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax, and synthetic waxes such as esters, ketones, and ethers can be used. Furthermore, fatty acid amides such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbon, and low molecular weight crystalline polymer resin, poly-n-stearyl methacrylate, poly-n- A crystalline polymer having a long alkyl group in the side chain such as a homopolymer or copolymer of polyacrylate such as lauryl methacrylate (for example, a copolymer of n-stearyl acrylate-ethyl methacrylate, etc.) can also be used. .

  The charge control agent and the release agent can be melt-kneaded together with the master batch and the binder resin, and of course, they may be added when dissolved and dispersed in the organic solvent.

(External additive)
Inorganic fine particles are preferably used as an external additive for assisting the fluidity, developability and chargeability of the toner particles. The primary particle diameter of the inorganic fine particles is preferably 5 × 10 ⁻³ to 2 [μm], particularly preferably 5 × 10 ^{−3 to} 0.5 [μm]. Moreover, it is preferable that the specific surface area by BET method is 20-500 [m < ² > / g]. The use ratio of the inorganic fine particles is preferably 0.01 to 5 [wt%] of the toner, and particularly preferably 0.01 to 2.0 [wt%]. Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Among these, as the fluidity imparting agent, it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using particles having an average particle diameter of 5 × 10 ⁻⁴ [μm] or less, both electrostatic force and van der Waals force with the toner are remarkably improved. Even with stirring and mixing in the developing device to obtain the charge level, the fluidity-imparting agent is not detached from the toner, and good image quality that does not cause firefly and the like can be obtained, and the residual toner is further reduced. Is planned. Titanium oxide fine particles are excellent in environmental stability and image density stability, but have a tendency to deteriorate the charge rise characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, this side effect is affected. It can be considered large. However, when the addition amount of the hydrophobic silica fine particles and the hydrophobic titanium oxide fine particles is in the range of 0.3 to 1.5 [wt%], the charge rising characteristics are not greatly impaired, and the desired charge rising characteristics can be obtained. Stable image quality can be obtained even when copying is repeated.

  Next, a toner manufacturing method will be described. Here, although a preferable manufacturing method is shown, it is not limited to this.

(Toner production method)
(1) A toner material solution is prepared by dispersing a colorant, unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent in an organic solvent.
The organic solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal after toner base particle formation. Specifically, toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, methyl ethyl ketone, Methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, and carbon tetrachloride are preferable. The usage-amount of an organic solvent is 0-300 weight part normally with respect to 100 weight part of polyester prepolymers, Preferably it is 0-100 weight part, More preferably, it is 25-70 weight part.

(2) The toner material liquid is emulsified in an aqueous medium in the presence of a surfactant and resin fine particles.
The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.

  The amount of the aqueous medium used relative to 100 parts by weight of the toner material liquid is usually 50 to 2000 parts by weight, preferably 100 to 1000 parts by weight. If the amount is less than 50 parts by weight, the dispersion state of the toner material liquid is poor, and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by weight, it is not economical.

Further, in order to improve the dispersion in the aqueous medium, a dispersant such as a surfactant and resin fine particles is appropriately added.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, fatty acid amide derivatives, polyhydric alcohols Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine And the like.

  Further, by using a surfactant having a fluoroalkyl group, the effect can be obtained in a very small amount. Preferred anionic surfactants having a fluoroalkyl group include fluoroalkyl carboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [ω-fluoroalkyl (C6-C11 ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [ω-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carvone Acids and metal salts, perfluoroalkylcarboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- ( 2-Hydroxyethyl) Perful Olooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Can be mentioned.

  Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-101. DS-102 (manufactured by Daikin Industries, Ltd.), Megafac F-110, F-120, F-113, F-191, F-812, F-833 (manufactured by Dainippon Ink, Inc.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fgentent F-100, F150 (manufactured by Neos).

  In addition, examples of the cationic surfactant include aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, and perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salts. , Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (manufactured by Asahi Glass), Florard FC-135 (manufactured by Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Manufactured), MegaFuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footgent F-300 (Neos), and the like.

  The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage which exists on the surface of a toner base particle becomes the range of 10-90 [%]. For example, polymethyl methacrylate fine particles 1 [μm] and 3 [μm], polystyrene fine particles 0.5 [μm] and 2 [μm], poly (styrene-acrylonitrile) fine particles 1 [μm], trade name is PB- 200H (manufactured by Kao Corporation), SGP (manufactured by Sokensha), technopolymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.) and the like. In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.

  As a dispersant that can be used in combination with the above resin fine particles and inorganic compound dispersant, the dispersed droplets may be stabilized by a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Bodies such as acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl, methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ-hydroxy Propyl, acrylic acid-3-chloro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Luric acid esters, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, or compounds containing vinyl alcohol and a carboxyl group Esters such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, vinyl pyridine, vinyl pyrrolidone, vinyl Nitrogen compounds such as imidazole and ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, poly Xoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxy Polyoxyethylenes such as ethylene nonylphenyl ester, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

  The dispersion method is not particularly limited, and known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. Among these, in order to make the particle size of the dispersion 2 to 20 [μm], a high-speed shearing method is preferable. When a high-speed shearing disperser is used, the number of rotations is not particularly limited, but is usually 1000 to 30000 [rpm], preferably 5000 to 20000 [rpm]. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 [° C.] (under pressure), preferably 40 to 98 [° C.].

(3) At the same time as the preparation of the emulsion, the amines (B) are added to cause a reaction with the polyester prepolymer (A) having an isocyanate group.
This reaction involves molecular chain crosslinking and / or elongation. The reaction time is selected depending on the reactivity between the isocyanate group structure of the polyester prepolymer (A) and the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is generally 0 to 150 [° C.], preferably 40 to 98 [° C.]. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.

(4) After completion of the reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles.
In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, the solvent base is removed to produce spindle-shaped toner base particles. . Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. Remove. It can also be removed by operations such as enzymatic degradation.

(5) A charge control agent is injected into the toner base particles obtained above, and then inorganic fine particles such as silica fine particles and titanium oxide fine particles are externally added to obtain a toner. The injection of the charge control agent and the external addition of the inorganic fine particles are performed by a known method using a mixer or the like.

  Thereby, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the true spherical shape and the rugby ball shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. be able to.

  The toner has a substantially spherical shape and can be represented by the following shape rule. 10A, 10B, and 10C are diagrams schematically illustrating the shape of the toner. 10A, 10B, and 10C, when a substantially spherical toner is defined by a major axis r1, a minor axis r2, and a thickness r3 (where r1 ≧ r2 ≧ r3), the toner is defined. The ratio of the major axis to the minor axis (r2 / r1) (see FIG. 10B) is 0.5 to 1.0, and the ratio of the thickness to the minor axis (r3 / r2) (FIG. 10C )) Is preferably in the range of 0.7 to 1.0. When the ratio of the major axis to the minor axis (r2 / r1) is less than 0.5, the dot reproducibility and transfer efficiency are inferior because of being away from the true spherical shape, and high-quality image quality cannot be obtained. On the other hand, if the ratio of thickness to minor axis (r3 / r2) is less than 0.7, the shape is close to a flat shape, and a high transfer rate like a spherical toner cannot be obtained. In particular, when the ratio of the thickness to the minor axis (r3 / r2) is 1.0, the rotating body has a major axis as a rotation axis, and the fluidity of the toner can be improved.

  Note that r1, r2, and r3 were measured with a scanning electron microscope (SEM) while changing the angle of field of view and taking pictures.

  Note that the configuration of the belt cleaning device 100 of the present embodiment can also be applied to the drum cleaning device 4 shown in FIG. Untransferred toner images such as toner remaining after transfer during normal image formation, a toner consumption pattern when a refresh mode is executed to refresh the inside of the developing device 5, and a toner image on the photoreceptor 1 when a paper jam occurs, Input to the drum cleaning device 4. By applying the configuration of the belt cleaning device 100 to the drum cleaning device 4, it is possible to satisfactorily remove the toner image input to the drum cleaning device 4.

[Embodiment 2]
The second embodiment of the image forming apparatus to which the present invention is applied will be described below.
The configuration of the belt cleaning device 100 described in the first embodiment is not limited to the cleaning device that cleans the front surface of the intermediate transfer belt, and can be rotated by a driving roller 52, a driven roller 53, or the like as shown in FIG. The present invention can also be applied to a conveyor belt cleaning device 500 that cleans the surface of the stretched paper conveyor belt 51.

  As shown in FIG. 11, a paper transport belt 51 as a member to be cleaned used in an image forming apparatus of a tandem type direct transfer system comes into contact with the photoreceptors 1Y, 1M, 1C, 1K, and Y, M, C, A primary transfer nip for K is formed. Then, in the process of conveying the recording paper P from the left side to the right side in the figure along with its endless movement while holding the recording paper P on its surface, the primary transfer nip for Y, M, C, K is used. In order. As a result, the Y, M, C, and K toner images are superimposed and primarily transferred onto the recording paper P. Contamination such as toner adhering to the paper transport belt 51 after passing through the primary transfer nip for K is removed by the transport belt cleaning device 500. The optical sensor unit 150 is disposed so as to face the front surface of the paper transport belt 51 with a predetermined gap.

  Also in the printer shown in FIG. 11, image density control and positional deviation amount correction control are performed at a predetermined timing, a predetermined toner pattern (gradation pattern, chevron patch) is formed on the paper transport belt 51, and the optical sensor unit 150. Then, the toner pattern is detected, and a predetermined correction process is executed based on the detection result. A toner pattern which is an untransferred toner image detected by the optical sensor unit 150 is removed by the conveyor belt cleaning device 500. Thus, the paper transport belt 51 has a function as an image carrier that carries a toner image.

  By applying the same configuration as the belt cleaning device 100 described in the first embodiment to the conveyance belt cleaning device 500, the toner pattern formed on the paper conveyance belt 51 can be favorably removed, and the back surface of the recording paper can be removed. It is possible to suppress contamination with toner and the like.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A first cleaning brush member such as a pre-cleaning brush roller 101 that electrostatically removes toner charged to a normal charging polarity on an object to be cleaned such as a rotatable intermediate transfer belt 8 and a normal charging to the first cleaning brush member A first voltage applying unit such as a power source 130a for applying a voltage having a polarity opposite to the polarity, and a toner which is provided downstream of the first cleaning brush member in the rotation direction of the cleaning target and is charged to a reverse polarity on the cleaning target. A second cleaning brush member such as a reverse polarity toner cleaning brush roller 104 to be removed electrostatically; a second voltage applying means such as a power source 132a for applying a voltage of normal charging polarity to the second cleaning brush member; and a second cleaning. Toner that is provided downstream of the brush member in the rotational direction of the cleaning object and charged to the normal charging polarity on the cleaning object is electrostatically A belt cleaning device 100 including a third cleaning brush member such as a normally charged toner cleaning brush roller 107 to be removed and a third voltage applying unit such as a power source 134a for applying a reverse polarity voltage to the third cleaning brush member; In the cleaning device, the first voltage applying means applies a voltage having a reverse polarity such that the charging polarity of the toner charged to the normal charging polarity can be reversed to the reverse polarity, to the first cleaning brush member. According to this, as described in the above embodiment, it is possible to reduce the input toner to the third cleaning brush member, and it is possible to suppress the deterioration of the cleaning performance of the entire cleaning device.
(Aspect B)
In (Aspect A), when the untransferred toner is removed from the object to be cleaned, the first voltage is set to a reverse polarity voltage having such a magnitude that the charge polarity of the toner charged to the normal charge polarity can be reversed to the reverse polarity. The applying means applies to the first cleaning brush member. According to this, as described in the above embodiment, the polarity distribution of the untransferred toner can be made closer to the positive side, and the toner removability with the second cleaning brush member can be improved.
(Aspect C)
In (Aspect A) or (Aspect B), application to the first cleaning brush member when the amount of cleaning residual toner on the object to be cleaned that has passed through the portion facing the first cleaning brush member is minimized. The first voltage applying means applies a voltage 10% to 20% higher than the voltage value to the opposite polarity side to the first cleaning brush member. According to this, as described in the above embodiment, regardless of variations in the resistance of the pre-cleaning brush roller 101 and the intermediate transfer belt 8 and fluctuations in the bias of the power supply (a fluctuation of about 5% of the power output), etc. Almost all the toner that could not be removed from the object to be cleaned by the first cleaning brush member can be charged with a reverse polarity.
(Aspect D)
An image comprising: an image carrier that carries a toner image; a toner image forming unit that forms a toner image on the surface of the image carrier; and a cleaning unit that removes toner as adhering material adhering to the surface of the image carrier. In the forming apparatus, the cleaning device of (Aspect A), (Aspect B) or (Aspect C) is used as the cleaning means. According to this, as described in the above embodiment, the toner on the image carrier can be removed satisfactorily.
(Aspect E)
An image carrier, a toner image forming unit that forms a toner image on the image carrier, a primary transfer unit that primarily transfers the toner image formed on the image carrier onto the intermediate transfer member, and an intermediate transfer member In the image forming apparatus including a secondary transfer unit that transfers a carried toner image to a recording material, and a cleaning unit that removes toner that is attached to the surface of the intermediate transfer member, the cleaning unit includes (Aspect A) The cleaning device of (Aspect B) or (Aspect C) was used. According to this, as described in the above embodiment, the toner on the intermediate transfer member can be satisfactorily removed.
(Aspect F)
An image carrier, a toner image forming unit for forming a toner image on the image carrier, a transfer unit for transferring the toner image formed on the image carrier to a recording material, and a transfer position of the recording material to the transfer position by the transfer unit In an image forming apparatus including a belt-shaped recording material conveying member to be conveyed and a cleaning unit that removes toner that is attached to the surface of the recording material conveying member, the cleaning unit includes (Aspect A) and (Aspect B). ) Or (Aspect C). According to this, as described in the above embodiment, the toner on the recording material conveying member can be favorably removed.
(Aspect G)
In (Aspect D), (Aspect E), or (Aspect F), when the shape factor SF-1 of the toner is 100 to 150, good image formation can be performed.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 4 Drum cleaning device 5 Developing device 6 Process unit 7 Transfer unit 8 Intermediate transfer belt 9 Primary transfer roller 10 Driven roller 11 Drive roller 12 Secondary transfer counter roller 13 Pre-cleaning counter roller 16 Tension roller 17 Application brush Counter roller 18 Secondary transfer roller 27 Paper feed roller 51 Paper transport belt 52 Drive roller 53 Drive roller 100 Belt cleaning device 100a Pre-cleaning unit 100b Reverse charged toner cleaning unit 100c Regular charged toner cleaning unit 101 Pre-cleaning brush roller 102 Pre-collecting roller 103 scraping blade 104 reversely charged toner cleaning brush roller 105 reversely charged toner recovery roller 106 scraping blade 107 regular charged toner Cleaning brush roller 108 Regularly charged toner collecting roller 109 Scraping blade 110 Conveying screw 111a First inlet seal 111b Second inlet seal 111c Third inlet seal 114 Insulating seal member 130 Cleaning power supply unit 130a Power supply 130b Voltage detection unit 131 Recovery power supply unit 131a Power supply 131b Voltage detection unit 132 Cleaning power supply unit 132a Power supply 132b Voltage detection unit 133 Recovery power supply unit 133a Power supply 133b Voltage detection unit 134 Cleaning power supply unit 134a Power supply 134b Voltage detection unit 135 Recovery power supply unit 135a Power supply 135b Voltage detection unit 150 Optical sensor unit 151 Optical sensor 200 Lubricant coating device 201 Coating brush roller 202 Solid lubricant 500 Conveying belt cleaning device

JP 2008-76858 A

Claims (7)

A first cleaning brush member that electrostatically removes toner charged to a regular charge polarity on a rotatable cleaning target;
First voltage applying means for applying a voltage having a polarity opposite to the normal charging polarity to the first cleaning brush member;
A second cleaning brush member that is provided downstream of the first cleaning brush member in the rotation direction of the cleaning object and electrostatically removes the toner charged to the opposite polarity on the cleaning object;
Second voltage applying means for applying a voltage of the normal charging polarity to the second cleaning brush member;
A third cleaning brush member that is provided downstream of the second cleaning brush member in the rotation direction of the cleaning object and electrostatically removes the toner charged to the regular charging polarity on the cleaning object;
A cleaning device comprising: a third voltage applying unit configured to apply the reverse polarity voltage to the third cleaning brush member;
The first voltage applying means applies a voltage of the reverse polarity such that the charge polarity of the toner charged to the normal charge polarity can be reversed to the reverse polarity, to the first cleaning brush member. And a cleaning device. The cleaning device according to claim 1.
When the untransferred toner is removed from the object to be cleaned, the voltage of the reverse polarity is set so that the charge polarity of the toner charged to the normal charge polarity can be reversed to the reverse polarity. A cleaning device applying to a member. The cleaning device according to claim 1 or 2,
When the amount of residual toner remaining on the object to be cleaned that has passed through the position facing the first cleaning brush member is minimized, the voltage applied to the first cleaning brush member is 10 on the opposite polarity side. A cleaning apparatus, wherein the first voltage applying means applies an increased voltage of [%] to 20 [%] to the first cleaning brush member. An image carrier for carrying a toner image;
Toner image forming means for forming a toner image on the surface of the image carrier;
In an image forming apparatus comprising: a cleaning unit that removes toner that is an adhering matter adhering to the surface of the image carrier;
An image forming apparatus using the cleaning device according to claim 1, 2 or 3 as the cleaning means. An image carrier;
Toner image forming means for forming a toner image on the image carrier;
Primary transfer means for primarily transferring the toner image formed on the image carrier onto a belt-like intermediate transfer member;
Secondary transfer means for transferring a toner image carried on the intermediate transfer member to a recording material;
In an image forming apparatus comprising: a cleaning unit that removes toner that is attached to the surface of the intermediate transfer member;
An image forming apparatus using the cleaning device according to claim 1, 2 or 3 as the cleaning means. An image carrier;
Toner image forming means for forming a toner image on the image carrier;
Transfer means for transferring a toner image formed on the image carrier to a recording material;
A belt-like recording material conveying member for conveying the recording material to a transfer position by the transfer means;
In an image forming apparatus comprising: a cleaning unit that removes toner that is attached to the surface of the recording material conveying member;
An image forming apparatus using the cleaning device according to claim 1, 2 or 3 as the cleaning means. The image forming apparatus according to claim 4, 5 or 6.
An image forming apparatus, wherein the toner has a shape factor SF-1 of 100 to 150.

Images