JP5831792B2 - Cleaning device and image forming apparatus - Google Patents

Description

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

  In an image forming apparatus such as a copying machine, a facsimile, or a printer, an unnecessary toner that remains on the surface of an image carrier after the toner image is transferred from the image carrier such as a latent image carrier or an intermediate transfer member onto the transfer target. The toner is removed by a cleaning device. As a cleaning device, a blade cleaning system is known in which a cleaning blade made of an elastic member is pressed against a peripheral surface on an image carrier to scrape off toner on the image carrier. The blade cleaning method is widely used because of its simple structure and stable performance.

  In recent years, there has been an increasing demand for image quality improvement, and in order to meet the demand, toner particle size reduction and spheroidization have been promoted. By reducing the particle size, it is possible to obtain a high-definition image with higher accuracy and fineness, and by improving the spherical shape, it is possible to improve developability and transferability. As a method for obtaining such a toner having a reduced particle size and spheroidization, there is a polymerization method compared to the conventional pulverization method.

  However, in the case of using a toner having a small particle size and a spherical shape, it is difficult to completely dam the toner with a cleaning blade in a general blade cleaning method, and some toners are cleaning blades. Will slip through. In the case of using a toner having a small particle size and a spherical shape, it is conceivable to increase the pressing force (linear pressure) of the cleaning blade against the image carrier to prevent the toner from slipping through. However, if the pressing force is increased and a high load is applied, the wear of the image carrier and the cleaning blade advances, and the service life becomes extremely short. In recent years, since the life of the apparatus is required to be increased, such a problem related to durability must be avoided.

  On the other hand, there is an electrostatic cleaning method as a method for satisfactorily cleaning the toner whose particle size has been reduced and spheroidized. In this method, a toner having a polarity opposite to the charging polarity of the toner is applied to a conductive cleaning brush roller or the like in contact with the image carrier to electrostatically remove the toner from the image carrier.

  However, there are cases where the toner cannot be completely removed even by the electrostatic cleaning method. This is due to variations in the charge amount of the residual toner that reaches the cleaning brush roller, as will be described below. Most of the toner on the image carrier before transfer is charged to the normal charging polarity of the toner (in this description, negative polarity). In the transfer unit, the toner on the image carrier is transferred to the transfer target by receiving a transfer electric field having a polarity (positive polarity) opposite to the normal charge polarity of the toner, but the toner adheres to the image carrier and is transferred as it is. Some toner becomes a residual toner. The amount of charge of the untransferred toner shifts to the positive polarity side, for example, by receiving positive charge injection applied at the transfer portion. For this reason, the transfer residual toner on the image carrier has a broad charge distribution in which a positive polarity toner and a negative polarity toner are mixed. In the above electrostatic cleaning method, positive cleaning voltage is applied to the cleaning brush roller with a polarity opposite to the normal charging polarity of the toner, and electrostatic cleaning is performed. Therefore, it is difficult to collect toner that has shifted to positive polarity. End up.

  As an electrostatic cleaning device that addresses such a problem, Patent Document 1 discloses a cleaning device having a plurality of cleaning brushes to which voltages having different polarities are applied. Specifically, a cleaning brush to which a predetermined voltage having the same polarity (negative polarity) as the normal charging polarity of the toner is applied and a cleaning brush to which a predetermined voltage having a polarity (positive polarity) opposite to the normal charging polarity of the toner is applied. With. As a result, both the positive toner and the negative toner can be removed from the image carrier with cleaning brushes having different polarities. The toner on the brush collected by the cleaning brush is electrostatically collected by each collecting roller to which a voltage having a higher absolute value of each polarity is applied.

  However, in the configuration including the plurality of cleaning brushes, the toner on the cleaning brush (hereinafter referred to as a reversely charged toner cleaning brush) to which a voltage having the same polarity as the normal charging polarity of the toner is applied is reattached to the image carrier. There was a problem that cleaning failure occurred. This is due to the following reason.

  The reversely charged toner cleaning brush should basically have only toner having a polarity opposite to that of the normal charge polarity, but it was confirmed that the toner having the normal charge polarity was actually attached. This is because after the toner is removed by the cleaning brush, the polarity of the toner on the cleaning brush is reversed due to charge transfer between the brush / toner and between the toner / toner, discharge due to a potential difference with the recovery roller, and charge injection. May end up. In particular, the toner tends to return to the normal charge polarity when charged with the opposite polarity. For this reason, on the reverse polarity toner cleaning brush, it is considered that the polarity of the reversely charged toner is likely to be reversed, and the normal charge polarity is likely to occur.

  Regularly charged toner on the reversely charged toner cleaning brush is not collected by the collecting roller but accumulates on the reversely charged toner cleaning brush and reattaches to the image carrier. Among the plurality of cleaning brushes, in the configuration in which the reversely charged toner cleaning brush is disposed on the most downstream side with respect to the surface movement direction of the image carrier, when the normally charged toner is reattached to the image carrier, a cleaning defect is immediately generated. Further, in the configuration in which the regular charged toner cleaning brush is disposed on the downstream side of the reversely charged toner cleaning brush, the margin of the downstream regular charged toner cleaning brush is lost when the amount of the regular charged toner to be reattached increases. For this reason, if the cleaning brush deteriorates with time, the regular charged toner on the image carrier may not be reliably removed, which may cause a cleaning failure.

  As described above, the problem of the present invention is that the positive polarity toner and the negative polarity toner of the image carrier are electrostatically removed from the image carrier by a plurality of cleaning brushes to which voltages having different polarities are applied. Although the cleaning apparatus has been described, the present invention is not limited to this. The same occurs if the cleaning device is configured to form an electric field that electrostatically moves toners of different polarities on the image carrier to the plurality of cleaning members between the image carrier and the plurality of cleaning members. To do. As such a cleaning device, for example, by applying voltages having different polarities to a plurality of opposing members that face the cleaning member across the image carrier, and grounding the cleaning member, the image carrier and the plurality of cleaning devices are arranged. A configuration in which an electric field for moving toners having different polarities from each other is formed between the members.

  The present invention has been made in view of the above problems, and an object thereof is to provide a reversely charged toner among a plurality of cleaning members on which an electric field for moving toners of different polarities on an image carrier is formed. It is an object of the present invention to provide a cleaning device capable of suppressing poor cleaning due to toner reattachment from the cleaning member to the image carrier and obtaining good cleaning performance, and an image forming apparatus including the cleaning device.

In order to achieve the above object, the invention according to claim 1 is in contact with the surface of the image carrier that moves on the surface, and toners of different polarities on the image carrier on the surface of the image carrier. In a cleaning device comprising a plurality of cleaning members each forming an electrostatically moving electric field, and each collecting member for electrostatically moving and collecting the toner on the cleaning member to its own surface,
Reverse charging for recovering the reversely charged toner on the reversely charged toner cleaning member as a recovery member for the reversely charged toner cleaning member for moving the reversely charged toner charged to a polarity opposite to the normal charged polarity of the toner among the plurality of cleaning members. A toner collecting member, and a regular charged toner collecting member for collecting the regular charged toner on the reversely charged toner cleaning member ,
The regular charged toner collecting member collecting normal charged toner from the reverse charged toner cleaning member also serves as a collecting member collecting toner from the normal charged toner cleaning member adjacent to the reverse charged toner cleaning member. To do.

  In the present invention, the reversely charged toner cleaning member includes a reversely charged toner collecting member and a regular charged toner collecting member. According to this, the reversely charged toner on the reversely charged toner cleaning member can be electrostatically collected by the reversely charged toner collecting member, and the normally charged toner can be electrostatically collected by the normally charged toner collecting member. Therefore, toner does not accumulate on the reversely charged toner cleaning member. Therefore, reattachment of toner from the reversely charged toner cleaning member to the image carrier is prevented, and cleaning failure caused by reattachment can be prevented.

  According to the present invention, among a plurality of cleaning members on which an electric field for moving toners of different polarities on the image carrier is formed, the toner is reattached to the image carrier from the reversely charged toner cleaning member. There is an excellent effect that poor cleaning can be suppressed and good cleaning performance can be obtained.

1 is a schematic configuration diagram illustrating a main part of a printer according to an 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 illustrating a toner consumption pattern formed on the intermediate transfer belt. FIG. 2 is an enlarged configuration diagram of a belt cleaning device of the printer and its surroundings. The schematic diagram explaining the maximum diameter MXLNG and the planar area AREA of the projection image with respect to the two-dimensional plane of a toner particle. FIG. 4 is a schematic diagram for explaining a peripheral length PERI and a planar 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. 2 is a schematic configuration diagram illustrating a main part of a tandem direct transfer type printer. 1 is a schematic configuration diagram showing a main part of a monochrome printer.

  Hereinafter, as an embodiment of an image forming apparatus to which the present invention is applied, a so-called tandem type intermediate transfer type printer (hereinafter simply referred to as a printer) will be described. First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing 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, 1K, charging devices 2Y, 2M, 2C, 3K, developing devices 5Y, 2M, 3C, 3K, drum cleaning devices 4Y, 4M, 4C, 4K, 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, four primary transfer rollers 9Y, 9M, 9C, 9K, a driven roller 10, a driving roller 11, a secondary transfer counter roller 12, and three counter rollers 13, 14 are provided. 15 and an application brush facing 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 counter roller 13, 14, 15 does 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. Thus, primary transfer nips for Y, M, C, and K are formed in which the surface of the intermediate transfer belt 8 and the photoreceptors 1Y, 1M, 1C, and 1K abut. 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 surface of the intermediate transfer belt 8 and the secondary transfer roller 18 abut is formed. 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.

  Further, the three opposing rollers 13, 14, and 15 disposed inside the belt loop are intermediate transfer belts between the cleaning brush rollers 101, 104, and 107 of the belt cleaning device 100 disposed outside the belt loop. 8 is sandwiched. As a result, a cleaning nip is formed in which the 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 device 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, A transfer image having 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.

  Further, the hardness HS 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. The printer includes the lubricant application device 200, which may be appropriately provided depending on the toner to be used, the material of the intermediate transfer belt 8, and the surface friction coefficient.

  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 primary-transferred superimposed on the surface of the intermediate transfer belt 8 at 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 surface of the intermediate transfer belt 8.

  On the other hand, in a paper feed unit (not shown), the recording paper P is sent out from the paper feed cassette one by one by the paper feed roller 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 surface of the intermediate transfer belt 8 with a predetermined gap. As shown in FIG. 2, 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 comprises a reflection type photosensor, and reflects light emitted from a light emitting element (not shown) by the surface of the intermediate transfer belt 8 or a toner image on the belt, and detects the amount of reflected light by a light receiving element (not shown). 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 Sy, Sm, Sc, Sk of each color are automatically formed at positions facing the optical sensors 151Y, 151M, 151C, 151K on the intermediate transfer belt 8 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 Sy, Sm, Sc, and Sk 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 (Sy, Sm, Sc, Sk) 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 process, Y, M, C, and K color toner images called chevron patches PV as shown in FIG. 3 are respectively provided at one end and the other end in the width direction of the intermediate transfer belt 8. An image for color misregistration detection is formed. As shown in FIG. 3, 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, a toner consumption pattern having an area of 25 [mm] × 250 [mm] as shown in FIG. 4 is created in the non-image forming area corresponding to the space between the sheets of the photoreceptor, and the intermediate transfer is performed. Transferred onto the belt 8. The adhesion amount of the toner consumption pattern 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 may be about 1.2 [mg / cm ² ]. 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 brush roller, or a cleaning device having a brush roller that removes positive polarity toner and a brush roller that removes negative polarity toner, each color gradation Untransferred toner images such as 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, in the belt cleaning device 100 of this printer, untransferred toner images that are transferred to the belt cleaning device 100 without being transferred to the recording paper P such as each color gradation pattern, chevron patch, and toner consumption pattern are removed at a time. Configured to be able to.

FIG. 5 is an enlarged configuration diagram of the belt cleaning device 100 and its surroundings of the printer.
In the figure, a belt cleaning device 100 includes a pre-cleaning unit for roughly removing an untransferred toner image on the intermediate transfer belt 8 and a polarity opposite to the normal charging polarity (negative polarity) on the intermediate transfer belt 8 ( A reversely charged toner cleaning unit that removes toner charged to a positive polarity) and a regular charged toner cleaning unit that removes toner charged to a regular charge polarity on the intermediate transfer belt 8 are provided. In addition, an entrance seal (not shown) is provided at the entrance of the belt cleaning device 100.

  The pre-cleaning unit has a pre-cleaning brush roller 101 as a pre-cleaning 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.

  Most of the toner constituting the untransferred toner image is charged with a normal charging polarity (negative polarity). The pre-cleaning brush roller 101 is grounded, and a voltage having the same polarity (negative polarity) as the normal charging polarity of the toner is applied to the pre-cleaning brush facing roller 13 so that the negative polarity toner on the intermediate transfer belt 8 is electrostatically applied. Configured to remove. A positive voltage is applied to the pre-collection roller 102.

  Further, the pre-cleaning unit includes a transport screw 110 as a transport unit for transporting to a waste toner tank (not shown) provided in the image forming apparatus main body.

  The reversely charged toner cleaning unit is disposed downstream of the precleaning unit in the moving direction of the intermediate transfer belt 8, and electrostatically charges the reversely charged toner charged to the opposite polarity (positive polarity) to the normal charging polarity (negative polarity) of the toner. And a reversely charged toner cleaning brush roller 104 as a reversely charged toner cleaning member to be removed. 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.

  The reversely charged toner cleaning brush roller 104 is grounded, a positive voltage is applied to the reversely charged toner cleaning brush facing roller 14, and a negative voltage is applied to the reversely charged toner recovery roller 105. Yes. The reversely charged toner cleaning unit serves as a polarity control unit that applies a negative charge to the toner on the intermediate transfer belt 8 and aligns the charge polarity of the toner on the intermediate transfer belt 8 with the normal charge polarity (negative polarity). It also has the function of

  Here, the reversely charged toner adhering to the reversely charged toner cleaning brush roller 104 may easily return to the normal charge polarity (negative polarity), and the polarity of the reverse polarity toner is reversed by charge injection or discharge, and the reversely charged toner cleaning brush Regularly charged toner is present on the roller 104. Therefore, in the printer of this embodiment, the normal charging toner collecting roller 108 as a normal charging toner collecting member that collects the normal charging toner attached to the reversely charged toner cleaning brush roller 104, and the roller in contact with the normal charging toner collecting roller 108 A regular charged toner scraping blade 109 is provided as a regular charged toner scraping member that scrapes the reversely charged toner from the surface. A positive voltage is applied to the normally charged toner collecting roller 108. Accordingly, the normally charged toner attached to the reversely charged toner cleaning brush roller 104 can be collected, and the normally charged toner is not accumulated on the reversely charged toner cleaning brush roller 104. For this reason, reattachment of the normally charged toner onto the intermediate transfer belt 8 on the reversely charged toner cleaning brush roller 104 is suppressed, and the cleaning margin of the normally charged toner cleaning brush roller 107 located downstream is improved. Thereby, even if the cleaning brush roller deteriorates with time, the toner on the intermediate transfer belt 8 can be surely removed, and the occurrence of defective cleaning can be suppressed.

  The normally charged toner cleaning unit is disposed on the downstream side in the moving direction of the intermediate transfer belt 8 with respect to the reversely charged toner cleaning unit, and normally charged toner cleaning for electrostatically removing the normally charged toner charged to the normally charged polarity (negative polarity). It has a regular charged toner cleaning brush roller 107 as a member. In addition, as a normally charged toner collecting member for collecting normally charged toner attached to the normally charged toner cleaning brush roller 107, the normally charged toner collecting roller 108 in contact with the above-described reversely charged toner cleaning brush roller 104 is a normally charged toner. Also in contact with the cleaning brush roller 107. The normally charged toner cleaning brush roller 107 is grounded, and a negative voltage is applied to the normally charged toner cleaning brush facing roller 15. The normally charged toner collecting roller 108 is applied with a negative voltage greater than that of the normally charged toner cleaning brush roller 107.

  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 16 [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. Further, the raised brushes of the cleaning brush rollers 101, 104, and 107 may be composed of only conductive fibers instead of the two-layered core-sheath structure. 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 apparatus 100, SUS rollers are used as the collecting rollers 102, 105, and 108. Each of the collection rollers 102, 105, and 108 is made of any material as long as it can perform the function of transferring the toner adhering to the cleaning brush roller from the brush to the collection roller by the potential gradient between the raised brush and the collection roller. It doesn't matter. 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 SUS roller as each of the collection rollers 102, 105, 108, there is an advantage 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 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 ^6-8 [Ω]
-Rotating shaft member applied voltage [V]:
Pre-cleaning brush roller 101: Ground (0 [V])
Reversely charged toner cleaning brush roller 104: Ground (0 [V])
Regularly charged toner cleaning brush roller 107: Ground (0 [V])
・ Brush flocking density: 100,000 [lines / inch ² ]
・ Brush fiber diameter: about 25 to 35 [μm]
-Brush tipping treatment: None-Brush diameter φ: 15-16 [mm]
-Brush fiber biting amount into the intermediate transfer belt 8: 1 [mm]
The brush flocking density, brush resistance, fiber diameter, applied voltage, fiber type, and brush fiber biting amount can be optimized by the system, and are not limited thereto. Examples of the types of fibers that can be used include nylon, acrylic, and polyester.

The conditions of each cleaning brush facing roller 13, 14, 15 are as follows.
-Opposite roller material: SUS
・ Counter roller applied voltage:
Pre-cleaning brush facing roller 13: -2400 [V]
Reversely charged toner cleaning brush facing roller 14: +1600 [V]
Regularly charged toner cleaning brush facing roller 15: -800 [V]
The material of the opposing roller and the applied voltage can be optimized by the system, and are not limited thereto.

The conditions of each collection roller 102, 105, 108 are as follows.
・ Recovery roller core material: SUS
-Brush fiber biting amount into the collection roller: 1.5 [mm]
・ Collecting roller cored bar voltage:
Pre-collection roller 102: + 400V
Reversely charged toner collection roller 105: −400 [V]
Regularly charged toner collecting roller 108: +400 [V]
The collection roller material, brush fiber entrapment amount, and applied voltage 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: 0.1 [mm]
・ Blade biting amount into collection roller: 1.0 [mm]
The blade contact angle, the blade thickness, and the amount of biting into the collection roller can be optimized by the system, and are not limited thereto.

Next, the cleaning operation of the belt cleaning apparatus 100 will be described.
As shown in FIG. 4, the untransferred toner image and the untransferred toner image that have passed through the secondary transfer portion pass through an entrance seal (not shown) and are transferred to the position of the pre-cleaning brush roller 101 by the rotation of the intermediate transfer belt 8. The pre-cleaning brush roller 101 is grounded, and a voltage having the same polarity (negative polarity) as the normal charging polarity of the toner is applied to the pre-cleaning brush facing roller 13. Thus, the negatively charged toner on the intermediate transfer belt 8 is electrostatically adsorbed to the pre-cleaning brush roller 101 by an electric field formed by the potential difference between the intermediate transfer belt 8 and the surface potential of the pre-cleaning brush roller 101. Move. The negative polarity toner that has moved to the pre-cleaning brush roller 101 is transferred to a contact position with the pre-collection roller 102 to which a positive polarity voltage has been 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 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.

  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 grounded, and a voltage having a polarity (positive polarity) opposite to the normal charging polarity of the toner is applied to the reversely charged toner cleaning brush facing roller 14. As a result, the positively charged toner on the intermediate transfer belt 8 is electrostatically adsorbed by the electric field formed by the potential difference between the intermediate transfer belt 8 and the surface potential of the reversely charged toner cleaning brush roller 104 to perform reversely charged toner cleaning. Move to brush roller 104. 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 toner moved to the reversely charged toner cleaning brush roller 104 is transferred to a contact position with the reversely charged toner collecting roller 105 to which a negative voltage is applied. 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.

  Further, the negatively charged toner that is present on the reversely charged toner cleaning brush roller 104 and returns to the normal charge by reversing the polarity with time due to charge injection and discharge, and the normal charge toner collecting roller 108 to which a positive voltage is applied. To the contact position. The negatively charged toner on the reversely charged toner cleaning brush roller 104 is electrostatically adsorbed by an electric field formed by a potential difference between the surface potential of the reversely charged toner cleaning brush roller 104 and the surface potential of the normally charged toner collecting roller 108. Then, the toner is moved onto the regular charged toner collecting roller 108. The negative polarity toner that has moved to the regular charged toner collecting roller 108 is scraped off from the surface of the collecting roller by the regular charged toner scraping blade 109.

  Next, the toner 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. The polarity of toner transferred to the normally charged toner cleaning brush roller 107 is controlled to be negative 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 small amount of toner is transferred to the regular charged toner cleaning brush roller 107.

  The normal charging toner cleaning brush roller 107 is grounded, and a voltage having the same polarity (negative polarity) as the normal charging polarity of the toner is applied to the normal charging toner cleaning brush facing roller 15. As a result, a very small amount of intermediate transfer belt 8 aligned with the negative polarity transferred to regular charged toner cleaning brush roller 107 by the electric field formed by the potential difference between intermediate transfer belt 8 and regular charged toner cleaning brush roller 107 surface potential. The upper toner is electrostatically attracted and moved to the normally charged toner cleaning brush roller 107. The negative toner moved to the regular charged toner cleaning brush roller 107 is transferred to a contact position with the regular charged toner collecting roller 108 to which a negative voltage is applied. The toner that has moved onto the regular charged toner cleaning brush roller 107 is electrostatically adsorbed by the electric field formed by the potential difference between the surface potential of the regular charged toner cleaning brush roller 107 and the surface potential of the regular charged toner recovery roller 108. Then, the toner is moved onto the regular charged toner collecting roller 108. The negative polarity toner that has moved to the regular charged toner collecting roller 105 is scraped off from the surface of the collecting roller by the regular charged toner scraping blade 109.

  In the belt cleaning device 100 of FIG. 5, the normally charged toner collecting roller 108 is in contact with both the oppositely charged toner cleaning brush roller 104 and the normally charged toner cleaning brush roller 107 that are adjacent to each other. The reversely charged toner cleaning brush roller 104 and the normally charged toner cleaning brush roller 107 share the normally charged toner collecting roller 108 as a collecting roller for collecting negatively charged toner. The polarity of the voltage applied to the normally charged toner collecting roller 108 for collecting the normally charged toner from the reversely charged toner cleaning brush roller 104 and the normally charged toner collecting roller 108 for collecting the normally charged toner from the normally charged toner cleaning brush roller 107 Since the polarity of the voltage applied to is the same, there is no problem even if they are shared. For this reason, size reduction and cost reduction of an apparatus can be achieved. It should be noted that it is of course possible to provide separate regular charged toner collection rollers for the reversely charged toner cleaning brush roller 104 and the regular charged toner cleaning brush roller 107, respectively.

  Further, in the belt cleaning device 100 of FIG. 5, a voltage is applied to the cleaning brush facing rollers 13, 14, 15 facing the cleaning brush rollers 101, 104, 107 across the intermediate tension belt 8, and the cleaning brushes are respectively applied. The rollers 101, 104, and 107 are grounded. Thus, an electric field for moving toners of different polarities is formed between the intermediate transfer belt 8 and the cleaning brush rollers 101, 104, and 107, respectively. As described above, in the configuration in which each cleaning brush roller side is grounded, even if the reversely charged toner cleaning brush roller 104 and the normally charged toner cleaning brush roller 107 are shared by the reversely charged toner cleaning brush roller 104, the cleaning brush roller and the recovery roller are used. And the potential difference can be kept constant.

  In addition to this configuration, by applying a voltage to the cleaning brush rollers 101, 104, and 107, toners having different polarities are moved between the intermediate transfer belt 8 and the cleaning brush rollers 101, 104, and 107. Of course, an electrostatic cleaning device configured to form an electric field may be used.

  As described above, the belt cleaning device 100 includes the normal charging toner cleaning brush roller 107 that electrostatically removes the toner having the normal charging polarity on the intermediate transfer belt 8 by applying a voltage having a polarity opposite to the normal charging polarity of the toner, and the toner. And a reversely charged toner cleaning brush roller 104 that electrostatically removes toner having a polarity opposite to the normal charge polarity on the intermediate transfer belt 8 by applying a voltage having the same polarity as the normal charge polarity. The belt cleaning device 100 is disposed upstream of the regular charging toner cleaning brush roller 107 and the reverse charging toner cleaning brush roller 104 with respect to the surface movement direction of the intermediate transfer belt 8 and applies a voltage having a polarity opposite to the normal charging polarity of the toner. In addition, a pre-cleaning brush roller 101 that electrostatically removes toner having a normal charging polarity is provided. With such a configuration, when an untransferred toner image containing a large amount of toner charged to a normal charge polarity is input to the belt cleaning device 100, the pre-cleaning brush roller 101 can roughly charge the normal image of the untransferred toner image. Polarly charged toner can be removed. As a result, the amount of toner input to the normally charged toner cleaning brush roller 107 and the reversely charged toner cleaning brush roller 104 disposed downstream of the pre-cleaning brush roller 101 in the belt movement direction is reduced. Thus, the toner charged to the normal charging polarity that could not be removed by the pre-cleaning brush roller 101 can be satisfactorily removed by the regular charging toner cleaning brush roller 107. In addition, the charged toner can be satisfactorily removed by the reversely charged toner cleaning brush roller 104 to the polarity opposite to the normal charged polarity. The regular charged toner removed from the intermediate transfer belt 8 by the pre-cleaning brush roller 101 is collected from the pre-cleaning brush roller 101 by the pre-collecting roller 102. The reversely charged toner removed from the intermediate transfer belt 8 by the reversely charged toner cleaning brush roller 104 is recovered from the reversely charged toner cleaning brush roller 104 by the reversely charged recovery roller 105. The normally charged toner removed from the intermediate transfer belt 8 by the normally charged toner cleaning brush roller 107 is recovered from the normally charged toner cleaning brush roller 107 by the normally charged recovery roller 108. Even if the reversely charged toner moved from the intermediate transfer belt 8 on the reversely charged toner cleaning brush roller 104 reverses its polarity and becomes a normally charged toner, the normally charged toner is reversely charged by the normally charged recovery roller 108. Collected from the cleaning brush roller 104. Thereby, there is no possibility that the toner is reattached from the reversely charged toner cleaning brush roller 104 to the intermediate transfer belt. Therefore, even if an untransferred toner image is input to the belt cleaning device, the untransferred toner image can be satisfactorily removed from the intermediate transfer belt.

Next, toner that is preferably used in the printer will be described.
The toner preferably 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. 6 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 represented 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.
SF-1 = {(MXLNG) 2 / AREA} × (100π) / 4 Formula (1)
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. 7 is a diagram schematically showing 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 represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π.
SF-2 = {(PERI) 2 / AREA} × 100 / 4π (2)
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 crosslinking and / or 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 of polyhydric alcohol (PO) and polycarboxylic acid (PC) is performed at 150 to 280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, while reducing the 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-isocyanatomethylcaproate, 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 polyvalent isocyanate 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 deteriorates, 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 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc., and water produced while reducing the pressure as necessary. Distill 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 it 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% by weight, preferably 3 to 10% by weight, 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. The effect on high temperature offset is exhibited without applying a release agent such as oil. 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, 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], and particularly preferably 5 × 10 −3 to 0.5 [μm]. Moreover, it is preferable that the specific surface area by BET method is 20-500 [m2 / 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 size of 5 × 10 −4 μm or less, the electrostatic force and van der Waals force with the toner are markedly improved. Even when stirring and mixing inside the developing device is performed, a fluidity-imparting agent is not detached from the toner, a good image quality that does not cause fireflies and the like is obtained, and a reduction in residual toner is further achieved. . 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 added 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, that is, repeated copying. Stable image quality can be obtained even if

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), MegaFuck F-110, F-
120, F-113, F-191, F-812, F-833 (Dainippon Ink Co., Ltd.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (Manufactured by Tochem Products Co., Ltd.), Footent F-100, F150 (manufactured by Neos), and the like.

  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 existing on the surface of the toner base particles is in the range of 10 to 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. 8A, 8B, and 8C are diagrams schematically showing the shape of the toner. 8A, 8B, and 8C, 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. The ratio of the major axis to the minor axis (r2 / r1) (see FIG. 8B) is 0.5 to 1.0, and the ratio of the thickness to the minor axis (r3 / r2) (FIG. 8C )) 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.

  Further, the cleaning device of the present invention can be applied not only to the belt cleaning device 100 that cleans the front surface of the intermediate transfer belt but also to the cleaning device 500 for the paper conveying belt 51 as shown in FIG. . As shown in FIG. 9, 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. 12, 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 cleaning device of the present invention to the transport belt cleaning device 500, the toner pattern formed on the paper transport belt 51 can be removed satisfactorily, and the back surface of the recording paper is prevented from being stained with toner. can do.

  The cleaning device of the present invention can also be applied to a drum cleaning device 4 as shown in FIG. An untransferred toner image such as a toner consumption pattern when a refresh mode for refreshing the inside of the developing device is executed and a toner image on the photosensitive member when a paper jam occurs is input to the drum cleaning device 4. By applying the cleaning device of the present invention to the drum cleaning device 4, it is possible to satisfactorily remove the untransferred toner image input to the drum cleaning device 4.

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)
An electric field is formed in contact with the surface of the image carrier such as the intermediate transfer belt 8 that moves on the surface, and electrostatically moves toners of different polarities on the image carrier to their surfaces. The cleaning device includes a plurality of cleaning members such as a plurality of cleaning brush rollers 104 and 107, and respective recovery members that electrostatically move the toner on the cleaning member to the surface of the cleaning member. As a toner collecting member on a reversely charged toner cleaning member such as a reversely charged toner cleaning brush roller 104 for moving a reversely charged toner charged to a polarity opposite to the normal charged polarity of the toner among a plurality of cleaning members. A reversely charged toner collecting member such as a reversely charged toner collecting roller 105 in which an electric field for electrostatically moving the reversely charged toner is formed, and a normally charged toner for collecting an electric field for electrostatically moving the normally charged toner Both regular charged toner collecting members such as a roller 109 are provided. According to this, as described in the above embodiment, it is possible to prevent the toner from accumulating in the reversely charged toner cleaning member and causing a cleaning failure.
(Aspect B)
In (Aspect A), the normally charged toner collecting member for collecting the normally charged toner from the reversely charged toner cleaning member is normally charged from the normally charged toner cleaning member such as the normally charged toner cleaning roller 107 adjacent to the reversely charged toner cleaning member. It also serves as a regular charged toner collecting member for collecting toner. According to this, as described in the above embodiment, the cleaning device can be reduced in size and cost.
(Aspect C)
In (Aspect A) or (Aspect B), a voltage is applied to opposing members such as the cleaning brush opposing rollers 14 and 15 that oppose each cleaning member with the image carrier such as the intermediate tension belt 8 interposed therebetween, and each cleaning is performed. By grounding the member, an electric field for moving toners of different polarities is formed between the image carrier and each cleaning member. According to this, as described in the above embodiment, the potential difference between the cleaning member and the recovery member can be kept constant.
(Aspect D)
In an image forming apparatus for forming an image on a recording paper as a recording material by finally transferring a toner image formed on the image bearing member from the image bearing member onto a recording material, The cleaning device of (Aspect A), (Aspect B) or (Aspect C) is used as a cleaning device for cleaning the transfer residual toner remaining on the toner. Thereby, as described in the above embodiment, high-quality image formation can be realized.

4Y, M, C, K: Drum cleaning device 8: Intermediate transfer belt 13, 14, 15: Cleaning counter roller 51: Paper transport belt 100: Belt cleaning device 101: Pre-cleaning brush roller 102: Pre-collecting roller 103: Pre-scraping Removal blade 104: Reversely charged toner cleaning brush roller 105: Reversely charged toner recovery roller 106: Reversely charged toner scraping blade 107: Regularly charged toner cleaning brush roller 108: Regularly charged toner recovery roller 109: Regularly charged toner scraping blade 500: Conveyor belt cleaning device

JP 2007-072398 A

Claims (4)

A plurality of cleanings in contact with the surface of the image carrier that moves on the surface, and between the image carrier and an electric field that electrostatically moves toners of different polarities on the image carrier to their surfaces. In a cleaning apparatus comprising a member and each recovery member that electrostatically moves the toner on the cleaning member to its surface and recovers the toner,
Reverse charging for recovering the reversely charged toner on the reversely charged toner cleaning member as a recovery member for the reversely charged toner cleaning member for moving the reversely charged toner charged to a polarity opposite to the normal charged polarity of the toner among the plurality of cleaning members. A toner collecting member, and a regular charged toner collecting member for collecting the regular charged toner on the reversely charged toner cleaning member ,
The regular charged toner collecting member collecting normal charged toner from the reverse charged toner cleaning member also serves as a collecting member collecting toner from the normal charged toner cleaning member adjacent to the reverse charged toner cleaning member. Cleaning device to do. In the cleaning apparatus of 請 Motomeko 1,
By applying voltages having different polarities to a plurality of opposing members that face the plurality of cleaning members across the image carrier and grounding the plurality of cleaning members, the image carrier and the plurality of members are grounded. An electric field for moving toners having different polarities from each other is formed between the cleaning member and the cleaning member.   A plurality of cleanings in contact with the surface of the image carrier that moves on the surface, and between the image carrier and an electric field that electrostatically moves toners of different polarities on the image carrier to their surfaces. In a cleaning apparatus comprising a member and each recovery member that electrostatically moves the toner on the cleaning member to its surface and recovers the toner,
  Reverse charging for recovering the reversely charged toner on the reversely charged toner cleaning member as a recovery member for the reversely charged toner cleaning member for moving the reversely charged toner charged to a polarity opposite to the normal charged polarity of the toner among the plurality of cleaning members. A toner collecting member, and a regular charged toner collecting member for collecting the regular charged toner on the reversely charged toner cleaning member,
By applying voltages having different polarities to a plurality of opposing members that face the plurality of cleaning members across the image carrier and grounding the plurality of cleaning members, the image carrier and the plurality of members are grounded. An electric field for moving toners having different polarities from each other is formed between the cleaning member and the cleaning member.   In an image forming apparatus for forming an image on a recording material by finally transferring a toner image formed on the image bearing member from the image bearing member onto a recording material, An image forming apparatus using the cleaning device according to claim 1 as a cleaning device for cleaning the residual transfer residual toner.

Images