JP2014062981A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly clean high-density toner even if cleaning performance is reduced in an electrostatic cleaning system, without wasting electric power.SOLUTION: An image forming device includes: a pre-cleaning brush roller 101 which removes transfer residual toner remaining after transferring a toner image formed on an intermediate transfer belt 8 to a recording sheet P, from the intermediate transfer belt and holds it; voltage application means which applies a voltage to electrostatically fix the transfer residual toner to the pre-cleaning brush roller; and voltage control means which applies a voltage larger in absolute value than in cleaning the transfer residual toner to the pre-cleaning brush roller, in cleaning non-transfer toner (high-density toner), such as a toner consumption pattern, on the intermediate transfer belt, which has passed through a secondary transfer area without being transferred to the recording sheet P.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.

  As a cleaning device employed in an image forming apparatus, a blade cleaning method in which a cleaning blade made of an elastic member is pressed against a peripheral surface of an image carrier that is a member to be cleaned to scrape and remove toner on the image carrier It has been known. 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. However, in the case of using a toner whose particle size is reduced and spheroidized, it is difficult to perform good cleaning with a general cleaning blade method. This is for the reason described below.

  That is, the cleaning blade removes the toner while rubbing the surface of the image carrier, but the edge portion of the cleaning blade is deformed by frictional resistance with the image carrier, so-called stick slip. A minute space is formed between the blades. The smaller the toner with a smaller particle size, the easier it is to enter this space, and the closer the toner that has entered the shape of a sphere is, the more likely the toner will rotate and the more easily the toner will roll. For this reason, the toner whose particle size has been reduced and spheroidized is likely to push up the cleaning blade and easily slip into the space between the cleaning blade and the image carrier.

  In the case of using a toner having a small particle size and a spherical shape, it is conceivable that the pressing force (linear pressure) of the cleaning blade against the image carrier is increased to prevent the toner from being trapped. 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 extended, such a problem related to durability must be avoided.

  On the other hand, an electrostatic cleaning method is known as a method for satisfactorily cleaning toner having a small particle size and a spherical shape. In this method, a toner having a polarity opposite to the charging polarity of the toner is applied to a cleaning member such as a conductive cleaning brush that is in contact with the image carrier to electrostatically remove the toner from the image carrier. . In the electrostatic cleaning method, two or more cleaning members including a cleaning member to which a positive voltage is applied and a cleaning member to which a negative voltage is applied are arranged for one image carrier. There is. In addition, there is also a type in which the toner charging polarity is aligned with one polarity by a non-contact charge applying device such as a corona charger and then cleaned with one cleaning member to which a voltage having a polarity opposite to the aligned charging polarity is applied. .

  In Patent Document 1, in order to always and satisfactorily remove the toner remaining on the intermediate transfer member, image formation is controlled so as to exert an appropriate cleaning performance according to the amount of toner remaining on the intermediate transfer member. A device has been proposed. This image forming apparatus is of an electrostatic cleaning type using two brush rollers. In this image forming apparatus, the image density of the toner image remaining on the intermediate transfer member is detected by the image density detection means, and the magnitude of the voltage applied to the brush roller is changed according to the detection result.

  In recent image forming apparatuses, toner forcibly replaces deteriorated toner in the developing device with new toner by discharging the deteriorated toner in the developing device onto the image carrier at a predetermined timing and forcibly consuming the toner. What performs consumption control is known. When this forced toner consumption control is performed, it is necessary to remove toner discharged from the developing device onto the image carrier (hereinafter referred to as “discharge toner”) from the image carrier by the cleaning member. In an image forming apparatus that performs such forced toner consumption control, not only untransferred residual toner that cannot be transferred but also discharged toner due to forced toner consumption control is targeted for cleaning.

  In general, in an image forming apparatus, when a jam occurs due to a conveyance failure of a recording material such as paper, a toner image in the middle of image formation remains on the image carrier. The toner image is also subject to cleaning.

  When toner discharged by forced toner consumption control or a toner image in the middle of image formation due to jamming is cleaned with a cleaning member for the image carrier, it is transferred to the transfer target, not the residual transfer toner remaining after transfer to the transfer target. The non-transfer toner that has passed through the transfer region without being cleaned is cleaned. In this case, it is necessary to clean the toner (high density toner) that adheres more per unit area than the untransferred toner with the cleaning member.

  As long as the cleaning member maintains a cleaning performance comparable to the initial cleaning performance, even such a high-density toner can be satisfactorily cleaned. However, in a situation where the cleaning performance of the initial stage cannot be maintained due to wear of the cleaning member due to use over time, the above-described high-density toner can be cleaned well even if the transfer residual toner can be cleaned well. There was a problem that it became difficult.

  This problem is caused by transferring a toner image in the middle of image formation due to discharged toner or jamming by toner forced consumption control to the outer peripheral surface of an endless recording material conveying member that conveys and conveys the recording material on the outer peripheral surface. The same occurs when cleaning is performed with the cleaning member for the material conveying member.

  According to the experiments by the present inventors, when an electrostatic cleaning type experimental machine using two or more brush rollers was subjected to an endurance test of 800,000 sheets, the outer diameter of the brush roller became thin due to deterioration. became. In this situation, although the transfer residual toner could be cleaned well, good cleaning could not be realized for the high density toner.

  More specifically, in this experimental machine, the toner on the image carrier is divided into two or more brush rollers and cleaned step by step. In the previous stage brush roller (brush roller located at the most upstream in the image carrier surface movement direction) used for a period of time, a part of the toner once moved on the brush roller at the time of cleaning is again with the rotation of the brush roller. A phenomenon occurs in which the toner is conveyed to a position facing the image carrier and is returned to the image carrier. The amount of the toner to be reversed tends to increase as the weight per unit area (hereinafter referred to as “toner M / A”) of the toner on the image carrier cleaned by the brush roller increases.

In the above experiment, when the toner M / A on the image carrier is 1.0 to 1.2 [mg / cm ² ], the toner M / A that returns (reattaches) to the image carrier after passing through the brush roller in the previous stage. Was around 0.05 [mg / cm ² ]. The reverse amount of 0.05 [mg / cm ² ] of toner is cleaned by the brush roller at the subsequent stage. At this time, if the brush roller at the rear stage maintains the initial cleaning performance, the cleaning can be performed satisfactorily. However, in a situation where the cleaning performance is low, the cleaning paper causes some cleaning failure and stains the transfer paper. A problem such as occurred.

  Here, it is conceivable to compensate for the decrease in the mechanical cleaning performance due to wear of the brush roller or the like by increasing the voltage applied to the brush roller and improving the electrostatic cleaning capability. However, when such a high voltage is applied to the brush roller, there is an excessive cleaning performance when cleaning the transfer residual toner, resulting in a problem of wasteful power consumption.

  The above problems are caused by transferring a toner image in the middle of image formation due to discharged toner or jam by toner forced consumption control to the outer peripheral surface of an endless recording material conveying member that carries and conveys the recording material on the outer peripheral surface, Even when cleaning is performed with the cleaning member for the recording material conveying member, it can occur similarly.

  Further, the image forming apparatus proposed in Patent Document 1 changes the magnitude of the voltage applied to the brush roller according to the amount of toner remaining on the intermediate transfer member. This is a technique for cleaning the toner satisfactorily. Therefore, the voltage applied to the brush roller is changed in accordance with the toner adhesion amount within the range assumed as the transfer residual toner, and good cleaning can be realized for the high density toner more than the transfer residual toner. is not.

  The present invention has been made in view of the above problems, and the object of the present invention is to satisfactorily clean high-density toner even when the cleaning performance deteriorates in the electrostatic cleaning method without wastefully consuming electric power. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

  In order to achieve the above object, the present invention comprises an image carrier that moves on the surface, a toner image forming unit that forms a toner image on the image carrier based on image information, and an image carrier that is formed on the image carrier. Transfer means for transferring the transferred toner image to the transfer object in the transfer region, and transfer residual toner remaining on the image support after the toner image formed on the image support is transferred to the transfer object. An image forming apparatus comprising: a cleaning rotator that is removed from an image carrier and held; and a voltage applying unit that applies a voltage for electrostatically attaching the transfer residual toner to the cleaning rotator. In this case, when cleaning the non-transferred toner on the image bearing member that has passed through the transfer region without being transferred to the transfer target, a voltage having an absolute value larger than that for cleaning the transfer residual toner is applied. And having a voltage control means for performing a voltage increase control for applying the serial voltage applying means.

  The non-transferred toner on the image carrier that has passed through the transfer region without being transferred to the transfer medium is high in which the toner adheres at a higher density than the transfer residual toner that remains on the image support after being transferred to the transfer medium. It is a density toner. In the present invention, when such non-transfer toner (high-density toner) is cleaned, a voltage having an absolute value larger than that when the transfer residual toner is cleaned is temporarily applied to the cleaning rotator. As a result, the electrostatic attractive force for adhering the non-transfer toner (high-density toner) on the image carrier to the cleaning rotator is increased, and the holding force for electrostatically holding the toner attached to the cleaning rotator is also increased. As a result, it is possible to satisfactorily clean the non-transfer toner (high density toner) even when the cleaning performance deteriorates. In addition, since a voltage having a small absolute value is applied when cleaning the transfer residual toner, it is possible to suppress wasteful power consumption due to excessive cleaning performance.

  According to the present invention, it is possible to obtain an excellent effect that high-density toner can be satisfactorily cleaned even when the cleaning performance is deteriorated in the electrostatic cleaning method without wastefully consuming electric power.

1 is a schematic configuration diagram illustrating a main part of a printer according to an embodiment. FIG. 2 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. 6 is a schematic diagram illustrating a toner consumption pattern formed on the intermediate transfer belt. It is the schematic diagram which showed typically the belt cleaning apparatus and its surrounding structure in the printer. It is an expanded block diagram which expands and shows the belt cleaning apparatus and its periphery. It is a table | surface which shows an example of the data table in the structural example which changes an applied voltage according to temperature and humidity. It is a timing chart which shows operations, such as application bias control to a pre-cleaning brush roller and a pre-collection roller, and rotation speed control of a pre-cleaning brush in an example. FIG. 6 is a schematic diagram illustrating a maximum diameter MXLNG and a planar area AREA of a projected image with respect to a two-dimensional plane of toner particles. FIG. 6 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 typically the shape of a toner, respectively. FIG. 2 is a schematic configuration diagram illustrating a main part of a tandem direct transfer printer. FIG. 2 is a schematic configuration diagram illustrating 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 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, and 1K, charging devices 2Y, 2M, 2C, and 2K, developing devices 5Y, 5M, 5C, and 5K, drum cleaning devices 4Y, 4M, 4C, and 4K, and a charge eliminating 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. A transfer unit 7 having an endless intermediate transfer belt 8 is disposed below the process units 6Y, 6M, 6C, and 6K. 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, and 9K, a driven roller 10, a driving roller 11, a secondary transfer counter roller 12, and three cleaning counter rollers 13, 14 are provided. 15 and an application brush opposing roller 17 are disposed. Each of these rollers functions as a stretching roller that stretches the intermediate transfer belt 8 around a part of its peripheral surface to stretch the belt. The cleaning counter rollers 13, 14, and 15 do not necessarily have to have a function of applying a constant tension, and may be driven to rotate as the intermediate transfer belt 8 rotates. The intermediate transfer belt 8 is moved endlessly in the counterclockwise direction in the drawing by the rotation of the driving roller 11 that is driven to rotate counterclockwise in the drawing by a driving means (not shown).

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

  Further, the intermediate transfer belt 8 is sandwiched between the secondary transfer counter roller 12 disposed inside the belt loop and the secondary transfer roller 18 disposed outside the belt loop. Thus, a secondary transfer nip is formed in which the outer peripheral surface of the intermediate transfer belt 8 and the secondary transfer roller 18 come into contact with each other. Note that a secondary transfer bias having a polarity opposite to that of the toner is applied to the secondary transfer roller 18 by a power source (not shown). Further, the paper transfer belt is bridged by the secondary transfer roller, several support rollers, and the drive roller, and the intermediate transfer belt 8 and the paper transfer belt are interposed between the secondary transfer roller 18 and the secondary transfer counter roller 12. It is good also as a structure inserted | pinched.

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

  The printer includes a paper feed unit (not shown) having a paper feed cassette that stores recording paper P as a recording material, a paper feed roller that feeds the recording paper P from the paper feed cassette to a paper feed path, and the like. 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, 5M, 5C, and 5K 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 the case of conventional plain paper. Therefore, in the present printer, an elastic layer having low hardness is provided on the intermediate transfer belt 8 so that the toner layer and recording paper with poor smoothness can be deformed at the transfer nip portion. By providing the intermediate transfer belt 8 with an elastic layer having low hardness and making the intermediate transfer belt 8 elastic, the surface of the intermediate transfer belt 8 can be deformed following local irregularities. Thereby, without excessively increasing the transfer pressure with respect to the toner layer, good adhesion can be obtained, there is no loss of transfer of characters, and there is no transfer unevenness even on paper with poor smoothness, Transfer images with excellent uniformity can be obtained

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

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

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

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

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

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

  The coat layer on the surface of the intermediate transfer belt 8 is for coating the surface of the elastic layer, and is composed of a layer having good smoothness. The material used for the coating layer is not particularly limited, but generally, a material that increases the secondary transferability by reducing the amount of toner adhering to the surface of the intermediate transfer belt 8 is used. For example, one or more types of polyurethane, polyester, epoxy resin, etc., or materials that reduce surface energy and increase lubricity, such as fluorine fats, fluorine compounds, fluorocarbons, titanium oxide, silicon carbide, etc. Can be used by dispersing one type or two or more types or changing the particle size as required. 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. Although the lubricant application device 200 is provided in this embodiment, it may not be necessary depending on the toner used, the material of the intermediate transfer belt, and the surface friction coefficient, and it is not always necessary to apply it.

  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 photoconductors 1Y, 1M, 1C, and 1K are developed by the developing devices 5Y, 5M, 5C, and 5K, so that Y and M are formed on the photoconductors 1Y, 1M, 1C, and 1K. , C, K toner images are obtained. The Y, M, C, and K toner images are primarily transferred while being superimposed on the outer peripheral surface of the intermediate transfer belt 8 in the above-described primary transfer nips for Y, M, C, and K. As a result, a four-color superimposed toner image is formed on the outer peripheral surface of the intermediate transfer belt 8.

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

  For the photoreceptors 1Y, 1M, 1C, and 1K 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), the charging devices 2Y, 2M, 2C, and 2K are uniformly charged to prepare 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.

  On the right side of the K process unit 6K in the figure, the optical sensor unit 150 is disposed so as to face the outer peripheral surface of the intermediate transfer belt 8 with a predetermined gap. As shown in FIG. 2, the optical sensor unit 150 includes Y optical sensors 151Y, C optical sensors 151C, M optical sensors 151M, and K optical sensors 151K arranged side by side in the width direction of the intermediate transfer belt 8. . Each of these sensors is composed of a reflection type photosensor, and reflects light emitted from a light emitting element (not shown) by a toner image on the outer peripheral surface of the intermediate transfer belt 8 or the intermediate transfer belt, and the amount of reflected light is reflected by a light receiving element (not shown). Detect. 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, as shown in FIG. 2, gradation patterns Sk, Sm, Sc, Sy of each color are automatically formed on the intermediate transfer belt 8 at positions facing the optical sensors 151Y, 151M, 151C, 151K. To do. The gradation pattern of each color is composed of 10 toner patches having an area of 2 [cm] × 2 [cm] having different image densities. The charging potentials of the photoreceptors 1Y, 1M, 1C, and 1K when creating the gradation patterns Sk, Sm, Sc, and Sy for each color are different from the uniform drum charging potential in the printing process, and gradually increase in value. To do. Then, while forming a plurality of patch electrostatic latent images for forming a gradation pattern image on the photoreceptors 1Y, 1M, 1C, and 1K by scanning with laser light, they are used for Y, M, C, and K, respectively. Development is performed by the developing devices 5Y, 5M, 5C, and 5K. During this development, the value of the developing bias applied to the Y, M, C, and K developing rollers is gradually increased. By such development, gradation pattern images of Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. These are primarily transferred so as to be arranged at a predetermined interval in the main scanning direction of the intermediate transfer belt 8. At this time, the toner adhesion amount of the toner patch in the gradation pattern of each color is about 0.1 [mg / cm ² ] at the minimum and 0.55 [mg / cm ² ] at the maximum, and the toner Q / d distribution When measured, it is almost aligned with the regular charging polarity.

  The toner patterns Sk, Sm, Sc, Sy formed on the intermediate transfer belt 8 pass through the positions facing the optical sensors 151Y, 151M, 151C, 151K as the intermediate transfer belt 8 moves endlessly. At this time, the optical sensors 151Y, 151M, 151C, and 151K receive an amount of light corresponding to the toner adhesion amount per unit area with respect to the toner patch of each gradation pattern.

  Next, from the output voltages of the optical sensors 151Y, 151M, 151C, and 151K when each color toner patch is detected and the adhesion amount conversion algorithm, the adhesion amount of each color toner pattern in each toner patch is calculated, and the calculated adhesion is calculated. Adjust the imaging conditions based on the amount. 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 process unit 6Y, 6M, 6C, 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 correction process, the 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 of the intermediate transfer belt 8 in the width direction. 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 image 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, and C toner images in the chevron patch PV, the detection time difference from the K toner image is read by the optical sensors 151Y, 151M, 151C, and 151K. 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.

  In addition, if the image forming operation with a low image area continues, the amount of old toner that remains in the developing device for a long time increases, so the amount of deteriorated toner with deteriorated toner charging characteristics, etc. Deterioration of the image quality and the deterioration of image quality. In order to prevent such deteriorated toner from staying in the developing device, a refresh mode that is toner forced consumption control for forcibly discharging the toner from the developing device to the non-image area of the photoreceptor 1 is executed at a predetermined timing. New toner is replenished to the developing device whose toner density has been reduced by the forced discharge of the toner, whereby the deteriorated toner in the developing device is replaced with new toner.

  In the present embodiment, a toner consumption amount of each developing device 5Y, 5M, 5C, 5K and an operation time of each developing device 5Y, 5M, 5C, 5K are stored in a control unit (not shown). Then, at a predetermined timing, each developing device is checked whether or not the toner consumption amount is a small amount equal to or less than a threshold with respect to the operation time of the developing device within a predetermined period, and the refresh mode is executed for the developing device below the threshold.

When the refresh mode is executed, a toner consumption pattern is created in a non-image area corresponding to an interval between images (interval of paper) on the photosensitive member, and the developing device consumes toner when forming the toner consumption pattern. The toner consumption pattern thus formed is transferred to the intermediate transfer belt 8 and formed on the intermediate transfer belt 8 as shown in FIG. 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 on the intermediate transfer belt is about 1.2 [mg / cm ² ]. May be. Further, when the toner Q / d distribution of the toner consumption pattern (a) transferred to the intermediate transfer belt 8 is measured, it is substantially aligned with the normal charging polarity. In this embodiment, the size of the toner consumption pattern is 25 [mm] × 250 [mm].

  In the present embodiment, each color gradation pattern, chevron patch, and toner consumption pattern formed on the intermediate transfer belt 8 pass through the secondary transfer area as it is without being transferred in the secondary transfer area, and the belt cleaning device 100. For this reason, the belt cleaning device 100 must remove a large amount of high-density toner (high-density toner) from the intermediate transfer belt 8 at this time. However, in a conventional cleaning device including a polarity control means and a brush roller, and a conventional cleaning device including a brush roller that removes positive polarity toner and a brush roller that removes negative polarity toner, each color gradation pattern In addition, non-transferred toner such as chevron patches and toner consumption patterns could not be removed at a time. Therefore, the toner on the intermediate transfer belt 8 that could not be cleaned may be transferred onto the recording paper during the next printing operation, resulting in an abnormal image.

  Therefore, the belt cleaning apparatus 100 of the present embodiment employs the following configuration so that non-transfer toner such as each color gradation pattern, chevron patch, and toner consumption pattern can be removed at a time.

FIG. 5 is a schematic diagram schematically showing the belt cleaning device 100 and the surrounding configuration, which are characteristic points of the printer.
FIG. 6 is an enlarged configuration diagram showing the belt cleaning device and its surroundings in an enlarged manner.
In the figure, a belt cleaning device 100 has a pre-cleaning portion 100a for roughly removing non-transferred toner 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 100b that removes the toner charged to (positive polarity) and a regular charged toner cleaning unit 100c that removes the toner charged to the regular charge polarity on the intermediate transfer belt 8 are provided.

  The pre-cleaning unit 100a has a pre-cleaning brush roller 101 as a cleaning rotator that is a cleaning member. Further, a pre-collecting roller 102 as a collecting member for collecting toner adhering to the pre-cleaning brush roller 101, a pre-scraping blade 103 as a scraping member that contacts the pre-collecting roller 102 and scrapes the toner from the roller surface, And a flicker 116 that scrapes off the toner on the cleaning brush roller 101.

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

  Further, the pre-cleaning unit 100a is provided with a conveying screw 110 as a conveying means for conveying to a waste toner tank (not shown) provided in the image forming apparatus main body.

  The reversely charged toner cleaning unit 100b is disposed downstream of the pre-cleaning unit 100a in the moving direction of the surface of the intermediate transfer belt, and statically charges toner charged to a polarity (positive polarity) opposite to the normal charging polarity (negative polarity) of the toner. A reversely charged toner cleaning brush roller 104 is provided as a cleaning member that is electrically removed. Further, the reversely charged toner cleaning roller 105 as a recovery member for recovering the reversely charged toner attached to the reversely charged toner cleaning brush roller 104, and scraping off the reversely charged toner from the roller surface in contact with the reversely charged toner recovery roller 105 A reversely charged toner scraping blade 106 as a member and a flicker 117 for scraping off the toner on the reversely charged toner cleaning brush roller 104 are provided. A negative voltage is applied to the reversely charged toner cleaning brush roller 104, and a negative voltage greater than that of the reversely charged toner cleaning brush roller 104 is applied to the reversely charged toner recovery roller 105. Further, the reversely charged toner cleaning unit 100b applies a negative charge to the toner on the intermediate transfer belt 8 so that the charge polarity of the toner on the intermediate transfer belt 8 is aligned with the normal charge polarity (negative polarity). It also has a function as a control means.

  The normally charged toner cleaning unit 100c is disposed downstream of the reversely charged toner cleaning unit 100b in the direction of movement of the intermediate transfer belt surface, and is a normally charged toner cleaning that is a cleaning member that electrostatically removes toner charged to the normally charged polarity. A brush roller 107 is provided. Further, the regular charged toner collecting roller 108 as a collecting member for collecting the regular charged toner attached to the regular charged toner cleaning brush roller 107, and scraping off the regular charged toner from the roller surface by contacting the regular charged toner collecting roller 108. A regular charged toner scraping blade 109 as a member and a flicker 118 for scraping off the toner on the regular charged toner cleaning brush roller 107 are provided. A positive voltage is applied to the normally charged toner cleaning brush roller 107, and a positive voltage greater than that of the normally charged toner cleaning brush roller 107 is applied to the normally charged toner recovery roller 108.

  The precleaning unit 100 a and the reversely charged toner cleaning unit 100 b are partitioned by a first insulating seal member 112, and the first insulating seal member 112 is in contact with the precleaning brush roller 101. By partitioning the precleaning unit 100a and the reversely charged toner cleaning unit 100b with the first insulating seal member 112, a discharge occurs between the precleaning brush roller 101 and the reversely charged toner cleaning brush roller 104, or reverse charging. It is possible to prevent the toner removed by the toner cleaning unit 100b from reattaching to the pre-cleaning brush.

  The reversely charged toner cleaning unit 100b and the regular charged toner cleaning unit 100c are partitioned by a second insulating seal member, and the second insulating seal member 113 is in contact with the reversely charged toner cleaning brush roller 104. Yes. By separating the reversely charged toner cleaning unit 100b and the normally charged toner cleaning unit 100c by the second insulating seal member 113, a discharge occurs between the reversely charged toner cleaning brush roller 104 and the normally charged toner cleaning brush roller 107. Or the toner removed by the normally charged toner cleaning unit 100c can be prevented from reattaching to the reversely charged toner cleaning brush roller 104.

  In addition, a third insulating seal member 114 that abuts the regular charged toner cleaning brush roller 107 is provided at the outlet of the cleaning device 100. Thereby, it is possible to suppress the occurrence of discharge between the normally charged toner cleaning brush roller 107 and the tension roller 16.

  Further, the belt cleaning device 100 is provided with an inlet seal 111 and a waste toner case 115. The waste toner case 115 stores the toner removed by the reversely charged toner cleaning unit 100b and the regular charged toner cleaning unit 100c. Further, the waste toner case 115 is detachably attached to the belt cleaning device 100, and the toner collected in the waste toner case 115 is removed by removing the waste toner case 115 from the cleaning device 100 during maintenance or the like. It can be done.

  In the belt cleaning device 100, the toner removed by the reversely charged toner cleaning unit 100b and the regular charged toner cleaning unit 100c is stored in the waste toner case 115, but the configuration is not limited thereto. For example, a reversely charged toner cleaning unit 100b and a regular charged toner cleaning unit 100c are provided by providing a conveyance member that conveys toner to the conveyance screw 110 at the bottom of the belt cleaning device 100, or by providing an inclined surface toward the conveyance screw 110 at the bottom. The toner removed in step 1 may be transported to a waste toner tank (not shown) provided in the image forming apparatus main body by the transport screw 110. In addition to the transport screw, a second transport screw that transports the toner removed by the reversely charged toner cleaning unit 100b and the regular charged toner cleaning unit 100c to a waste toner tank (not shown) provided in the image forming apparatus main body. It may be provided.

  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 in the range of 14 [mm] to 22 [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 normally charged 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, the cleaning brush rollers 101, 104, and 107 bite into the intermediate transfer belt 8 by about 1 [mm], and the brushed parts are brought into contact with the intermediate transfer belt surface moving direction by a driving means (not shown). Rotates to move in the opposite 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 to 10 ⁸ [Ω]
・ Brush flocking density: 100,000 [lines / inch ² ]
・ Brush fiber diameter: about 25 to 35 [μm]
-Brush tipping treatment: None-Brush diameter φ: 15-17 [mm]
-Brush fiber biting amount into the intermediate transfer belt 8: 1 [mm]
The applied voltage to the pre-cleaning brush roller is set so that good cleaning performance can be obtained when high density (high density) non-transfer toner on the intermediate transfer belt is input in the initial cleaning performance. . The reverse charging toner cleaning brush roller 104 is set to have a high absolute value so that charges are injected into the toner on the intermediate transfer belt 8. Further, the brush flocking density, brush resistance, fiber diameter, applied voltage, fiber type, and brush fiber biting amount can be optimized by the system, and thus are not limited thereto. Examples of the types of fibers that can be used include nylon, acrylic, and polyester.

The conditions of each collection roller 102, 105, 108 are as follows.
・ Recovery roller core material: SUS303
-Brush fiber biting amount into the collection roller: 1.5 [mm]
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.
・ Recovery roller core material: SUS304
・ 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 of this embodiment will be described.
As shown in FIG. 5, the untransferred toner and non-transferred toner that have passed through the secondary transfer portion are transferred to the position of the pre-cleaning brush roller 101 by the rotation of the intermediate transfer belt 8 beyond the contact portion of the inlet seal 111. Is done. A voltage having a polarity (positive polarity) opposite to the normal charging polarity of the toner is applied to the pre-cleaning brush roller 101, and an electric field formed by a difference in surface potential between the intermediate transfer belt 8 and the pre-cleaning brush roller 101 is applied. Then, the negatively charged toner on the intermediate transfer belt 8 is electrostatically attracted and moved to the pre-cleaning brush roller 101. The negative polarity toner that has moved to the pre-cleaning brush roller 101 is transferred to a contact position with the pre-collection roller 102 to which a positive polarity voltage having a larger absolute value than the pre-cleaning brush roller 101 is applied. Then, the toner that has moved onto the pre-cleaning brush roller 101 is electrostatically adsorbed by the electric field formed by the potential difference between the surface potential of the pre-cleaning brush roller 101 and the surface potential of the pre-collecting roller 102, and the pre-collecting roller 102 The negative toner that has been moved upward and moved to the pre-collection roller 102 is scraped off from the surface of the 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.

  At this time, a voltage is applied to the pre-collection roller 102 for the purpose of collecting as much toner as possible attached to the pre-cleaning brush roller 101. This is because when a large amount of toner remaining on the pre-cleaning brush roller 101 remains, the toner removing ability from the intermediate transfer belt 8 to the pre-cleaning brush roller 101 decreases. When cleaning the transfer residual toner, the potential difference between the surface potential of the pre-cleaning brush roller 101 and the surface potential of the pre-collecting roller 102 is set to about 400 [V], for example.

  In this embodiment, when cleaning the toner consumption pattern, since the absolute value of the bias applied to the pre-cleaning brush roller 101 is increased, it is necessary to increase the bias applied to the pre-collection roller 102 accordingly. At this time, it is desirable that the potential difference between the surface potential of the pre-cleaning brush roller 101 and the surface potential of the pre-collection roller 102 is larger than that during cleaning of the transfer residual toner. This is because when the toner consumption pattern is cleaned, the amount of toner adhering to the pre-cleaning brush roller 101 increases. Therefore, such a large amount of toner is moved to the pre-collection roller 102 side and returned to the intermediate transfer belt 8. This is because it is necessary to reduce the amount of water.

  However, when cleaning the transfer residual toner, if a large potential difference is formed as in the case of cleaning the toner consumption pattern, excessive current flows into the toner when the toner moves to the pre-collection roller 102, and the charge of the toner In some cases, the toner charge polarity is reversed, and the toner on the pre-collection roller 102 may be reattached to the pre-cleaning brush roller 101. In this case, the amount of toner returning to the intermediate transfer belt 8 is increased.

In this embodiment, when the toner M / A to be cleaned by the pre-cleaning brush roller 101 is about 0.5 [mg / cm ² ] or more, the pre-cleaning brush roller is more effective than the case of cleaning the transfer residual toner. The absolute value of the bias applied to 101 is increased. At this time, the potential difference between the surface potential of the pre-cleaning brush roller 101 and the surface potential of the pre-collection roller 102 is increased accordingly. As a result, even when the toner M / A is a high density toner having a toner M / A of 0.5 [mg / cm ² ] or more, good cleaning properties are obtained.

  As described above, the absolute values of the bias applied to the pre-cleaning brush roller 101 and the bias applied to the pre-collection roller 102 are increased in a very short time when cleaning high density toner such as a toner consumption pattern. is there. For this reason, it is possible to reduce power consumption as compared with the case where such a high applied bias is applied also during cleaning of the residual toner. Further, since temperature rises of the pre-cleaning brush roller 101, the pre-collecting roller 102, and the flicker 116 can be suppressed, toner sticking can be prevented.

  The rotational speed (surface linear velocity) of the pre-cleaning brush roller 101 when cleaning the transfer residual toner is about 400 [mm / sec] when the linear velocity of the intermediate transfer belt 8 is 600 [mm / sec]. By doing so, the linear velocity difference is set to 150%. If the linear velocity difference is increased too much, the cleaning performance is improved, but the frictional heat is increased when the pre-cleaning brush roller 101 is flicked by the flicker 116 or the pre-collecting roller 102, which causes a problem of toner fixation. is there. In the toner of the present embodiment, fixing occurs at about 40 to 60 [° C.], so it is difficult to continuously increase the linear velocity difference to about 200%. However, in the case of a low density (low density) toner such as a transfer residual toner, if the linear speed difference is about 130% for cleaning this, good cleaning properties can be maintained, so that the toner can be reduced to 150%. It is set.

  On the other hand, when cleaning the toner consumption pattern, it is desirable to set the rotational speed (surface linear velocity) of the pre-cleaning brush roller 101 so that the linear velocity difference from the intermediate transfer belt 8 is 200% or more. . This is because when cleaning high density toner such as a toner consumption pattern, higher cleaning performance is required than when cleaning residual toner. Then, by increasing the rotational speed (surface linear velocity) of the pre-cleaning brush roller 101 so that the linear velocity difference with the intermediate transfer belt 8 is 200% or more, the high-density toner such as the toner consumption pattern can be reduced. Also good cleaning properties could be secured.

  As described above, according to the present embodiment, the absolute value of the bias applied to the pre-cleaning brush roller 101 and the rotation speed are increased during cleaning of high-density toner such as a toner consumption pattern, so that most of the high-density toner is removed. The toner having normal charging polarity (negative polarity) can be roughly removed, and the polarity of the toner can be reversed and reattached to the intermediate transfer belt 8 due to charge injection or discharge. Accordingly, it is possible to prevent an excessive amount of toner from being input to the reversely charged toner cleaning brush roller 104 and the regular charged toner cleaning brush roller 107 even during high density toner cleaning. Therefore, even if the reversely charged toner cleaning brush roller 104 and the regular charged toner cleaning brush roller 107 have deteriorated equivalent to 800,000 prints, the toner can be removed satisfactorily. As a result, even when high-density toner adheres to the intermediate transfer belt 8, it can be satisfactorily removed from the intermediate transfer belt 8.

  Further, in this embodiment, negative charge is injected into the toner on the intermediate transfer belt 8 by the reversely charged toner cleaning brush roller 104, and the charge polarity of the toner passing through the regular charged toner cleaning brush roller 107 is made negative. Although the polarity control to align is performed, such polarity control may not necessarily be performed depending on the toner condition and the image forming condition. In this embodiment, the regular charged toner cleaning unit 100c is provided on the most downstream side in the belt moving direction, but the reversely charged toner cleaning unit 100b may be provided on the most downstream side in the belt moving direction. In this case, the normal charge toner cleaning brush roller 107 injects positive charge into the toner on the intermediate transfer belt 8, and the polarity control is performed so that the charge polarity of the toner passing through the normal charge toner cleaning brush roller 107 is made positive. Alternatively, the polarity control may not be performed.

  In this embodiment, the positively charged toner on the intermediate transfer belt 8 is removed by the reversely charged toner cleaning brush roller 104. However, the reversely charged toner cleaning unit 100b is changed to a polarity control unit, and the intermediate transfer belt is changed. 8 may be configured not to remove the positive polarity toner. In this case, the toner on the intermediate transfer belt 8 that has passed through the pre-cleaning brush roller 101 is made to have a negative polarity by the polarity control unit and is sent to the normally charged toner cleaning brush roller 107 downstream in the belt moving direction from the polarity control unit. Be transported. Then, the negatively charged toner is removed by the normally charged toner cleaning brush roller 107. As a means for injecting negative charge into the toner on the intermediate transfer belt 8 in the polarity control unit, a conductive brush, a conductive blade, a corona charger, or the like may be used. Also, instead of aligning the charging polarity of the toner to negative polarity, arrange a cleaning brush roller to which a negative voltage is applied downstream of the polarity control unit in the belt moving direction so that it is aligned to positive polarity. A configuration in which toner having a positive polarity on the intermediate transfer belt is removed may be employed. Even in such a configuration, when the high-density toner is cleaned, the high-density toner is roughly removed from the intermediate transfer belt 8 by the pre-cleaning brush roller 101, so that the amount of toner transferred to the polarity control unit is excessive. It will never increase. Therefore, even when cleaning high-density toner, the polarity control unit can satisfactorily align the toner on the intermediate transfer belt 8 with one polarity. As a result, the toner on the intermediate transfer belt 8 can be satisfactorily electrostatically removed by the cleaning brush roller disposed downstream of the polarity control unit.

  In this embodiment, a voltage is applied to each collecting roller 102, 105, 108 and each cleaning brush roller 101, 104, 107. However, each collecting roller 102, 105, 108 is a metal roller, and the collecting roller is used. Alternatively, the voltage may be applied only to the first electrode. In this case, a bias voltage somewhat lower than the bias voltage applied to the recovery roller is applied to the cleaning brush roller in a form through the contact portion with the recovery roller due to a potential drop due to the fiber resistance of the cleaning brush roller. It becomes a state. Thereby, a potential difference is formed between the collection roller and the cleaning brush roller, and the toner can be electrostatically moved from the cleaning brush roller to the collection roller by a potential gradient in the direction of the collection roller.

  Further, since the brush resistance varies depending on the use environment, it may be controlled to change the applied voltage for each environment. The applied voltage is stored in advance in a table in the internal memory of the main body, the applied voltage corresponding to the temperature and humidity at that time is read from the value of the temperature and humidity sensor, and the pre-cleaning brush roller 101 and the pre-collecting roller 102 are biased. Apply. For example, as this table, for example, a table having the contents of the table shown in FIG. 7 is stored as the internal memory of the main body, and the set value is changed according to environmental conditions.

〔Example〕
Here, an example of the belt cleaning apparatus 100 of the present embodiment will be described.
FIG. 8 is a timing chart showing operations such as bias control applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102 and control of the number of rotations of the pre-cleaning brush in this embodiment.
In this embodiment, when the refresh mode is executed, a toner consumption pattern is formed from a point of 15 mm from the start of the sheet interval. In this embodiment, the linear velocity of the intermediate transfer belt 8 is 600 [mm / sec], the outer diameter of the pre-cleaning brush roller 101 is 15 [mm], and the brush rotation speed (surface linear velocity) is 400 [mm]. / Sec]. Further, when cleaning the transfer residual toner, the bias applied to the pre-cleaning brush roller 101 is +2000 [V], and the bias applied to the pre-collection roller 102 is +2400 [V].

  The bias applied to the pre-cleaning brush roller 101 is raised from +2000 [V] to +2300 [V] at the timing when the sheet interval (non-image area) enters the cleaning area of the pre-cleaning brush roller 101. By raising the applied bias in this way, even when high-density toner such as discharged toner adheres on the intermediate transfer belt 8 between the sheets, it can be satisfactorily removed from the intermediate transfer belt 8.

  In synchronization with this, the bias applied to the pre-collection roller 102 is also raised from +2400 [V] to +3000 [V]. As a result, the high-density toner attached on the pre-cleaning brush roller 101 can be moved onto the pre-collection roller 102. Therefore, there is little toner remaining on the pre-cleaning brush roller 101 without being collected by the pre-collecting roller 102. Therefore, even with high-density toner, the amount of toner returning from the pre-cleaning brush roller 101 to the intermediate transfer belt 8 can be reduced. In addition, since the potential difference when cleaning the transfer residual toner is low, the toner on the pre-collection roller 102 is prevented from reattaching to the pre-cleaning brush roller 101 during cleaning of the transfer residual toner, and the intermediate transfer belt 8. The amount of toner that reverts back to can be reduced.

The applied biases (+2300 [V], +3000 [V]) after the pulling up are attached to the pre-cleaning brush roller 101 at the rear end of the toner consumption pattern in the refresh mode, and this is collected by the pre-collecting roller 102. It is sufficient to apply only during the period until The application time at this time may be a very short time of 0.11 [sec] from the following equation (1).
{(15 [mm] +25 [mm] + 15 × π / 2 [mm]} ÷ 600 [mm / sec]
= 0.11 [sec] (1)

  As described above, according to the present embodiment, a high bias is applied to the pre-cleaning brush roller 101 and the pre-collecting roller 102 in only a very short time of 0.11 seconds. Therefore, it is possible to suppress power consumption as compared with the case where such a high bias is applied also during cleaning of the transfer residual toner. Further, the temperature rise of the pre-cleaning brush roller 101, the pre-recovery roller 102 and the flicker 116 can be suppressed, and toner sticking can be prevented.

  In this embodiment, the brush rotation speed of the pre-cleaning brush roller 101 is changed from 400 [mm / sec] to 600 [mm / sec] in synchronism with the change in the applied bias of the pre-cleaning brush roller 101 and the pre-collecting roller 102. ]. As a result, the cleaning performance temporarily increases, and good cleaning performance can be exhibited even with a high-density toner such as a toner consumption pattern. In addition, since the brush rotation speed is raised only for a very short time, the temperature rise of the pre-cleaning brush roller 101 due to the frictional heat of the flicker 116 and the pre-collecting roller 102 is small, and the problem of toner sticking does not occur.

  In the timing chart shown in FIG. 8, the refresh mode is not executed during the third sheet interval. This is because a toner consumption pattern is not formed between the sheets.

  In the above-described embodiment, only the pre-cleaning brush roller 101 positioned at the most upstream in the belt movement direction among the three cleaning brush rollers 101, 104, and 107 is applied to the absolute value of the applied bias and the brush rotation speed when cleaning the high-density toner. The control which raises was performed. However, at least one of the remaining two cleaning brush rollers 104 and 107 may be controlled to increase the absolute value of the applied bias and the brush rotation speed when cleaning the high density toner. As a result, the overall toner removal performance of the belt cleaning device 100 during the cleaning of the high density toner is improved, so that a better cleaning property can be obtained.

  Further, at least one of the remaining two cleaning brush rollers 104 and 107 may be controlled to increase the absolute value of the applied bias without increasing the brush rotation speed when cleaning high density toner. As a result, the overall toner removal performance of the belt cleaning device 100 during the cleaning of the high density toner is improved, so that a better cleaning property can be obtained.

  Further, at least one of the remaining two cleaning brush rollers 104 and 107 may be controlled to increase the brush rotation speed without increasing the absolute value of the applied bias when cleaning high density toner. As a result, the overall toner removal performance of the belt cleaning device 100 during the cleaning of the high density toner is improved, so that a better cleaning property can be obtained.

In the above-described embodiment, the control for increasing the absolute value of the bias applied to the cleaning brush roller and the brush rotation speed is performed during the cleaning of the high density toner, but the transfer residual toner when forming the high density image is removed. In this case, control for increasing the absolute value of the bias applied to the cleaning brush roller and the brush rotation speed may be performed. In this case, based on the image information input to the printer, the toner adhesion amount is grasped from the image area and the like, and when this is larger than a predetermined amount, a cleaning brush roller is applied when cleaning the transfer residual toner. Control for increasing the absolute value of the bias and the brush rotation speed may be performed. Specifically, for example, when the average transfer residual toner amount in the belt width direction of the intermediate transfer belt 8 is 0.2 [mg / cm ² ] or more, the cleaning brush roller is used for cleaning the transfer residual toner. Control to increase the absolute value of applied bias and brush rotation speed is performed. As a result, even when a large amount of untransferred toner is input to the belt cleaning device 100, the cleaning performance can be improved by an amount necessary for this, and efficient electrostatic cleaning can be realized. The threshold for determining whether or not to perform this control need not be the average amount of residual toner in the intermediate transfer belt 8 in the belt width direction. For example, the maximum transfer residual toner in the belt width direction of the intermediate transfer belt 8 may be used. It may be a value or a minimum value.

  Further, when the image density (toner adhesion amount per unit area) of the toner on the intermediate transfer belt 8 detected by the optical sensor unit 150 is larger than a predetermined amount set in advance, the absolute value of the bias applied to the cleaning brush roller, Control for increasing the brush rotation speed may be performed. In this case, since whether or not to perform the control is determined according to the amount of toner actually input to the belt cleaning apparatus 100, more efficient electrostatic cleaning can be realized.

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. 9 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1. The shape factor SF-1 represents the ratio of the roundness of the toner shape and is represented by the following formula (2). 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) (2)
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. 10 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 the unevenness of the toner shape, and is represented by the following formula (3). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × 100 / (4π) (3)
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-isocyanatomethyl caproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; phenol derivatives, oximes, caprolactam And a combination of two or more of these. The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5/1, the low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1/1, when a urea-modified polyester is used, the urea content in the ester becomes low and hot offset resistance deteriorates. The content of the 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 B1 to B5 blocked amino groups (B6) 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 polyhydric carboxylic acid (PC) are heated to 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxy titanate, 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 elongation reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator may be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those obtained by blocking them (ketimine compounds).

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

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

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

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

  The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If the temperature is lower than 45 ° C., the heat resistance of the toner is deteriorated.

  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 masterbatch and the binder resin, or may be added when dissolved and dispersed in an organic solvent.

(External additive)
Inorganic fine particles are preferably used as an external additive for assisting the fluidity, developability and chargeability of the toner particles. The primary particle diameter of the inorganic fine particles is preferably 5 × 10 ⁻³ to 2 [μm], particularly preferably 5 × 10 ^{−3 to} 0.5 [μm]. Moreover, it is preferable that the specific surface area by BET method is 20-500 [m < ² > / g]. The use ratio of the inorganic fine particles is preferably 0.01 to 5 wt% of the toner, and particularly preferably 0.01 to 2.0 wt%. Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Among these, as the fluidity imparting agent, it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using particles having an average particle diameter of 5 × 10 ⁻⁴ μm or less, the electrostatic force and van der Waals force with the toner are remarkably improved. Even when stirring and mixing inside the developing device is performed to obtain a good image quality that does not cause the release of the fluidity imparting agent from the toner and does not generate firefly, etc., and further reduces the residual toner. It is done. 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, Ltd.), Megafac F-110, F-120, F-113, F-191, F-812, F-833 (manufactured by Dainippon Ink, Inc.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fgentent F-100, F150 (manufactured by Neos).

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

  The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage 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 of the isocyanate group structure of the polyester prepolymer (A) with 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.
FIGS. 11A, 11B, and 11C are diagrams schematically illustrating toner shapes.
In FIGS. 11A, 11B, and 11C, 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. 11B) is 0.5 to 1.0, and the ratio of the thickness to the minor axis (r3 / r2) (FIG. 11C )) 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 according to the present invention can be applied not only to the belt cleaning device 100 that cleans the outer peripheral surface of the intermediate transfer belt 8, but also to the cleaning device 500 for the paper conveying belt 51 as shown in FIG. . As shown in FIG. 12, a paper transport belt 51 as a member to be cleaned used in an image forming apparatus of a tandem type direct transfer system is a photoreceptor 1Y, 1M, 1C, 1K by transfer rollers 59Y, 59M, 59C, 59K. In contact with each other to form primary transfer nips for Y, M, C, and K. Then, in the process of conveying the recording paper P from the left side to the right side in the drawing along with its endless movement while holding the recording paper P on its surface, the primary transfer nip for Y, M, C, and K is used. In order. Thus, Y, M, C, and K toner images are superimposed and primarily transferred onto the recording paper P. Contamination such as toner (unnecessary toner) adhering to the paper conveyance belt 51 after passing through the primary transfer nip for K is removed by the conveyance belt cleaning device 500. The optical sensor unit 150 is disposed so as to face the outer peripheral 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. The toner pattern which is the high density toner detected by the optical sensor unit 150 is removed by the transport belt cleaning device 500.

  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 according to the present invention can also be applied to the drum cleaning device 4 as shown in FIG. Non-transferred toner (high-density toner) such as a toner consumption pattern when the refresh mode for refreshing the inside of the developing device 5 is executed and a toner image on the photosensitive member when a paper jam occurs is input to the drum cleaning device 4. The By applying the cleaning device of the present invention to the drum cleaning device 4, the non-transfer toner input to the drum cleaning device 4 can be satisfactorily removed.

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 image carrier such as an intermediate transfer belt 8 that moves on the surface, toner image forming means such as process units 6Y, 6M, 6C, and 6K that form toner images on the image carrier based on image information, and the image carrier Transfer means such as a secondary transfer roller 18 for transferring a toner image formed on the body to a transfer medium such as recording paper P in a transfer area such as a secondary transfer area, and toner formed on the image carrier A cleaning rotating body such as a pre-cleaning brush roller 101 that removes and holds transfer residual toner remaining on the image carrier after the image is transferred to the transfer body, and the transfer residual toner as described above. In an image forming apparatus having voltage applying means for applying a voltage for electrostatically adhering to a cleaning rotator to the cleaning rotator, the image forming apparatus passes through the transfer region without being transferred to the transfer target. Voltage control means for performing voltage increase control for applying a voltage having a larger absolute value to the voltage application means when cleaning non-transferred toner such as a toner consumption pattern on the image bearing member. It is characterized by having.
According to this aspect, when non-transfer toner having a higher density than the transfer residual toner is input to the cleaning rotator, the cleaning rotator temporarily applies a voltage whose absolute value is larger than that when cleaning the transfer residual toner. Apply to. As a result, the electrostatic attractive force for adhering the non-transfer toner (high-density toner) on the image carrier to the cleaning rotator is increased, and the holding force for electrostatically holding the toner attached to the cleaning rotator is also increased. As a result, it is possible to satisfactorily clean the non-transfer toner (high density toner) even when the cleaning performance deteriorates. In addition, since a voltage having a small absolute value is applied when cleaning the transfer residual toner, it is possible to suppress wasteful power consumption due to excessive cleaning performance.

(Aspect B)
In the aspect A, the toner image forming means forms a toner image developed with the toner in the developing device 5 on the image carrier, and the toner in the developing device is formed on the image carrier. Toner forced control for controlling toner consumption for cleaning the toner (toner consumption pattern) on the image carrier that has been discharged and passed through the transfer region without being transferred to the transfer target as the non-transfer toner. It has a consumption control means.
According to this, image quality can be improved by replacing the deteriorated toner in the developing device with new toner, and the toner consumption pattern at that time can be cleaned well.

(Aspect C)
In the aspect A or B, the cleaning rotary body is driven to rotate, and the cleaning rotary body is driven to rotate at a higher rotational speed than the case where the transfer residual toner is cleaned when the non-transfer toner is cleaned. Drive control means for performing rotational acceleration control for controlling the rotation drive means.
According to this, since the cleaning performance at the time of cleaning the non-transfer toner (high density toner) on the image carrier is temporarily increased, the non-transfer toner (high density toner) can be used even when the cleaning performance deteriorates. It becomes possible to clean well. In addition, since the rotational speed of the cleaning rotator when cleaning the transfer residual toner is low, it is possible to suppress the occurrence of toner fixation due to frictional heat with a member such as flicker that contacts the cleaning rotator.

(Aspect D)
In the aspect C, the drive control unit is configured to clean the toner remaining after the transfer of the toner image as the toner adhesion amount of the toner image formed based on the image information specified based on the image information increases. The rotation driving means is controlled so that the rotation speed of the cleaning rotator is increased.
Accordingly, efficient electrostatic cleaning can be realized also in cleaning of the transfer residual toner.

(Aspect E)
In the aspect C, the toner adhesion amount detection unit such as the optical sensor unit 150 that detects the toner adhesion amount of the toner image formed on the image carrier is provided, and the drive control unit includes the toner adhesion amount detection unit. The rotation driving means is controlled so that the larger the toner adhesion amount detected by the toner, the higher the rotational speed of the cleaning rotating body when cleaning the transfer residual toner of the toner image.
According to this, more efficient electrostatic cleaning can be realized also in cleaning of transfer residual toner.

(Aspect F)
In any one of the above embodiments A to E, two or more cleaning members (cleaning brush rollers 101, 104, 107) for cleaning the toner on the image carrier are arranged side by side in the image carrier surface movement direction. The cleaning rotator is a cleaning member such as a pre-cleaning brush roller 101 positioned at the most upstream of the image carrier surface movement direction among the two or more cleaning members, and the voltage control means removes the non-transfer toner. When cleaning, the voltage increase control is not performed for cleaning members (cleaning brush rollers 104 and 107) other than the cleaning rotator.
According to this, it is possible to efficiently clean the high density toner.

(Aspect G)
In any one of the above aspects C to E, two or more cleaning members (cleaning brush rollers 101, 104, 107) made of a rotating body for cleaning the toner on the image carrier are arranged in the image carrier surface movement direction. The cleaning rotator is a cleaning member such as a pre-cleaning brush roller 101 located at the most upstream of the image carrier surface movement direction among the two or more cleaning members, and the voltage control means When cleaning the non-transfer toner, the voltage increase control is not performed on the cleaning members (cleaning brush rollers 104 and 107) other than the cleaning rotator, and the drive control means Cleaning members other than cleaning rotators (cleaning For even Guburashirora 104 and 107), and it performs the rotation speed increasing control.
According to this, when cleaning high-density toner, it is possible to exhibit high cleaning performance while suppressing power consumption due to voltage increase control.

(Aspect H)
In any one of the above embodiments C to E, two or more cleaning members (cleaning brush rollers 101, 104, and 107) for cleaning the toner on the image carrier are arranged side by side in the image carrier surface movement direction. The cleaning rotator is a cleaning member such as a pre-cleaning brush roller 101 located at the most upstream of the image carrier surface movement direction among the two or more cleaning members, and the drive control means removes the non-transfer toner. When cleaning, the cleaning member other than the cleaning rotator (cleaning brush rollers 104 and 107) is not subjected to the rotation acceleration control, and the voltage control means is configured to perform the cleaning rotator when cleaning the non-transferred toner. Non-cleaning member (cleaning brush low Characterized in that it also performs the voltage increasing control for 104 and 107).
According to this, at the time of cleaning of high density toner, it is possible to exhibit high cleaning performance while suppressing toner fixation due to rotational acceleration control.

(Aspect I)
In any one of the above aspects A to H, the image carrier may be an intermediate member such as an intermediate transfer belt 8 on which a plurality of toner images formed on a latent image carrier such as the photoreceptor 1 are sequentially superimposed and transferred. It is a transfer member.
Since a high-density toner adheres to the intermediate transfer member, a higher effect can be obtained by performing the above-described voltage increase control or the like in cleaning the intermediate transfer member.

(Aspect J)
An image carrier such as the photosensitive member 1 that moves on the surface, a toner image forming unit such as a charging device or a developing device 5 that forms a toner image on the image carrier based on image information, and a toner image forming unit that is formed on the image carrier. Formed on the image carrier, and a recording material conveying member such as an endless paper conveying belt 51 which conveys a recording material such as recording paper P onto which the transferred toner image is finally transferred. Transfer means such as a transfer roller 59 for transferring the toner image to the recording material carried on the recording material conveying member in the transfer region, and the recording when transferring the toner image on the image carrier to the recording material. A cleaning rotating body such as a pre-cleaning brush roller 101 for removing unnecessary toner adhering to the outer peripheral surface of the material conveying member from the recording material conveying member and holding it, and the unnecessary toner adhering to the cleaning rotating body electrostatically Electricity to make Transfer of gradation patterns, chevron patches, toner consumption patterns, etc. transferred to the recording material conveying member as they are without being transferred to the recording material in an image forming apparatus having a voltage applying means for applying to the cleaning rotator When cleaning toner (high-density toner), voltage control means for performing voltage increase control for applying a voltage having a larger absolute value to the voltage application means than when cleaning the unnecessary toner is provided.
According to this aspect, when the transfer toner having a higher density than the unnecessary toner is input to the cleaning rotator, a voltage having a larger absolute value is temporarily applied to the cleaning rotator than when unnecessary toner is cleaned. . This increases the electrostatic attractive force that causes the transfer toner (high-density toner) on the recording material conveying member to adhere to the cleaning rotator, and also increases the holding force that electrostatically holds the toner attached to the cleaning rotator. As a result, it is possible to satisfactorily clean the transfer toner (high density toner) even when the cleaning performance deteriorates. In addition, when cleaning unnecessary toner, since a voltage having a small absolute value is applied, power consumption can be suppressed wastefully due to excessive cleaning performance.

(Aspect K)
In any one of the above aspects A to J, the toner has a shape factor SF1 of 100 to 150.
According to this, high-quality image formation can be realized.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 4 Drum cleaning device 5 Developing device 6 Process unit 8 Intermediate transfer belt 9 Primary transfer rollers 13, 14, 15 Cleaning opposing roller 18 Secondary transfer roller 51 Paper transport belt 59 Transfer roller 100 Belt cleaning device 100a Pre Cleaning unit 100b Reverse charged toner cleaning unit 100c Regular charged toner cleaning unit 101 Blur cleaning brush roller 102 Pre-collection roller 103 Pre scraping blade 104 Reverse charged toner cleaning brush roller 107 Regular charged toner cleaning brush roller 150 Optical sensor unit 151 Optical sensor 200 Lubricant application device 500 Conveyor belt cleaning device

JP 2006-251030 A

Claims (11)

An image carrier that moves on the surface;
Toner image forming means for forming a toner image on the image carrier based on image information;
Transfer means for transferring the toner image formed on the image carrier to a transfer target in a transfer region;
A cleaning rotator that removes and holds the transfer residual toner remaining on the image carrier after the toner image formed on the image carrier is transferred to the transfer body;
In an image forming apparatus comprising: a voltage applying unit that applies a voltage for electrostatically adhering the transfer residual toner to the cleaning rotator.
When cleaning the non-transferred toner on the image carrier that has passed through the transfer region without being transferred to the transfer target, a voltage having an absolute value larger than that when cleaning the transfer residual toner is applied to the voltage applying unit. An image forming apparatus comprising voltage control means for performing voltage increase control. The image forming apparatus according to claim 1.
The toner image forming means forms a toner image developed with toner in a developing device on the image carrier,
The toner in the developing device is discharged onto the image carrier, and the toner on the image carrier that has passed through the transfer region without being transferred to the transfer body is cleaned as the non-transfer toner. An image forming apparatus comprising toner forced consumption control means for performing toner forced consumption control. The image forming apparatus according to claim 1 or 2,
A rotation driving means for rotating the cleaning rotating body;
A drive control means for performing rotational acceleration control for controlling the rotational drive means so as to rotationally drive the cleaning rotating body at a rotational speed faster than that for cleaning the untransferred toner when cleaning the non-transfer toner; An image forming apparatus comprising: The image forming apparatus according to claim 3.
The drive control means determines the cleaning rotating body when cleaning the transfer residual toner of the toner image as the toner adhesion amount of the toner image formed by the image information specified based on the image information increases. An image forming apparatus, wherein the rotation driving unit is controlled so that a rotation speed is increased. The image forming apparatus according to claim 3.
A toner adhesion amount detecting means for detecting a toner adhesion amount of a toner image formed on the image carrier,
The rotation control unit is configured to increase the rotation speed of the cleaning rotating body when cleaning the transfer residual toner of the toner image as the toner adhesion amount detected by the toner adhesion amount detection unit increases. An image forming apparatus that controls the image forming apparatus. The image forming apparatus according to any one of claims 1 to 5,
Two or more cleaning members for cleaning the toner on the image carrier are arranged side by side in the image carrier surface movement direction;
The cleaning rotator is a cleaning member located at the most upstream of the image carrier surface movement direction among the two or more cleaning members,
The image forming apparatus according to claim 1, wherein when the non-transfer toner is cleaned, the voltage control unit does not perform the voltage increase control on a cleaning member other than the cleaning rotator. The image forming apparatus according to any one of claims 3 to 5,
Two or more cleaning members made of a rotating body for cleaning the toner on the image carrier are arranged side by side in the image carrier surface movement direction,
The cleaning rotator is a cleaning member located at the most upstream of the image carrier surface movement direction among the two or more cleaning members,
When the non-transfer toner is cleaned, the voltage control means does not perform the voltage increase control for a cleaning member other than the cleaning rotator,
The image forming apparatus according to claim 1, wherein when the non-transfer toner is cleaned, the drive control unit performs the rotation acceleration control for a cleaning member other than the cleaning rotator. The image forming apparatus according to any one of claims 3 to 5,
Two or more cleaning members for cleaning the toner on the image carrier are arranged side by side in the image carrier surface movement direction;
The cleaning rotator is a cleaning member located at the most upstream of the image carrier surface movement direction among the two or more cleaning members,
When the non-transfer toner is cleaned, the drive control unit does not perform the rotation acceleration control for a cleaning member other than the cleaning rotator,
The image forming apparatus according to claim 1, wherein when the non-transfer toner is cleaned, the voltage control unit also performs the voltage increase control on a cleaning member other than the cleaning rotator. The image forming apparatus according to any one of claims 1 to 8,
The image forming apparatus, wherein the image carrier is an intermediate transfer member to which a plurality of toner images formed on the latent image carrier are sequentially superimposed and transferred. An image carrier that moves on the surface;
Toner image forming means for forming a toner image on the image carrier based on image information;
An endless recording material transporting member that transports the recording material onto which the toner image formed on the image carrier is finally transferred, supported on the outer peripheral surface;
Transfer means for transferring a toner image formed on the image carrier to a recording material carried on the recording material conveying member in a transfer region;
A cleaning rotator that removes and holds unnecessary toner adhering to the outer peripheral surface of the recording material conveying member when the toner image on the image carrier is transferred to the recording material;
In an image forming apparatus comprising: a voltage applying unit that applies a voltage for electrostatically attaching the unnecessary toner to the cleaning rotator.
Voltage increase control for applying a voltage having a larger absolute value to the voltage applying means when cleaning the transfer toner transferred to the recording material conveying member as it is without being transferred to the recording material than when cleaning the unnecessary toner An image forming apparatus comprising voltage control means for performing the above. The image forming apparatus according to any one of claims 1 to 10,
An image forming apparatus, wherein the toner has a shape factor SF1 of 100 to 150.

Images