JP5055615B2 - Image forming apparatus and process cartridge - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image using an electrophotographic process, and more specifically, a so-called cleaner that does not have a cleaning device for discarding residual toner on an image carrier around the image carrier. The present invention relates to an image forming apparatus called a less type and a process cartridge equipped in the image forming apparatus.

  Conventionally, in an image forming apparatus that forms an image using an electrophotographic process, such as a copying machine, a facsimile machine, a printer, a plotter, or a complex machine of these, an untransferred toner on an image carrier for the purpose of downsizing the apparatus. A so-called cleaner-less system has been proposed in which the toner is temporarily recovered by a recovery member in contact with the image carrier and then discharged onto the image carrier again.

For example, in an image forming apparatus described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-252203), a transfer residual toner having a reversely charged polarity is collected by a collecting member and cleaned at a timing at the time of a non-image forming operation such as a job end. A system has been adopted in which the transfer residual toner collected by providing a mode or the like is returned to the image carrier.
However, in this method, when the discharged toner passes through the charging unit, the toner adheres to the charging unit and the charging member becomes dirty, thereby causing an image defect due to a decrease in the charging potential of the photosensitive member, and the charging unit replacement cycle. There was a problem that became shorter.

  Therefore, a configuration in which the charging roller is provided with a cleaning member has been proposed in the past, but a separate cleaning member, a collection container, etc. are required, and the apparatus becomes complicated and large, so the small size that is an advantage of the cleanerless system This is contrary to cost and cost reduction.

On the other hand, the image forming apparatus described in Patent Document 2 (Japanese Patent Laid-Open No. 6-102800) proposes a configuration in which a cleaning member for cleaning the photosensitive member is also in contact with the charging member. This configuration is characterized in that the toner discharging means from the photosensitive member and the charging member is shared.
However, in this configuration, there is no idea of a cleanerless system, and the cleaning member mechanically scrapes off the toner from the photoreceptor and the charging roller into the waste toner container. In particular, although a configuration using a brush as a cleaning unit is described, the toner is collected from the photosensitive member or the charging roller by mechanical rubbing, and the cleaned toner is accumulated in the brush. If the brush contacts the charging roller, the charging roller may be soiled. Furthermore, although flicker for preventing toner accumulation on the brush is provided, the flicker may cause toner scattering, which may cause contamination of the charging roller. In addition, a mechanism for contacting and separating the photosensitive member of the cleaning member and the charging roller is provided, but this function is intended to drop the toner accumulated when the charging roller is cleaned into the lower toner container using gravity. Therefore, the mechanism of the present invention is different from the mechanism of controlling the toner charge amount and electrostatically collecting the reversely charged toner.

  The disadvantages of the prior art as described above are caused by the non-uniformity of the charge amount of the transfer residual toner, and it is difficult to apply this configuration to the cleanerless system without controlling the charge amount. It is.

JP 2004-252203 A JP-A-6-102800

  In an image forming apparatus using an image bearing member (for example, a photosensitive member) and a non-contact charging roller, there is a merit that the transfer residual toner on the photosensitive member is difficult to adhere to the charging roller. It is difficult to return it to the photosensitive member again, and it is necessary to provide a dedicated cleaning device for the charging roller in order to prevent the charging failure of the photosensitive member due to toner contamination of the charging roller. For this reason, there has been a problem that the apparatus becomes larger and the number of members increases, resulting in an increase in cost.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an image forming apparatus capable of preventing the charging roller from being soiled by transfer residual toner on the image carrier and obtaining a stable image quality over a long period of time can be reduced in size and cost. It is another object of the present invention to provide a process cartridge mounted on the image forming apparatus.

In order to achieve the above object, the present invention adopts the following means.
According to the first aspect of the present invention, there is provided an image carrier that carries an electrostatic latent image, a charging roller that charges the surface of the image carrier in proximity to the image carrier, and a latent image on the image carrier. A latent image forming means for forming a toner image, a developing means for developing a toner image by attaching toner to the latent image on the image carrier, and a toner image on the image carrier directly on the recording material or on an intermediate transfer member In the image forming apparatus comprising at least a transfer means for transferring via a charge amount and a charge amount control means for controlling the charge amount of the transfer residual toner on the image carrier, the charge amount control means comprises the image carrier. A contact / separation mechanism that selectively contacts either of the charging rollers and a detection unit that detects the amount of toner adhering to the charge amount control unit. The contact with the charging roller is performed during non-image formation, When the charge amount control means is in contact with the image bearing member during image, voltage Vbr1 applied to the charge amount control means, when the surface potential of the image bearing member opposed to Vpc,
Vbr1 <Vpc
Satisfy the relationship
When the charge amount control means is in contact with the charging roller, the voltage Vbr2 applied to the charge amount control means is Vc when the potential of the metal core of the opposite charging roller is Vc.
Vbr2 <Vc
Satisfy the relationship
When the charge amount control means is in contact with the image carrier during non-image formation, the voltage Vbr3 applied to the charge amount control means is given by assuming that the surface potential of the opposite image carrier is Vpc.
Vbr3> Vpc
The discharge mode is set so as to satisfy the above relationship, and the discharge mode is executed according to the detection result of the detection means .

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the transfer residual toner remaining on the image carrier without being transferred by the transfer unit is collected simultaneously with the development by the developing unit. it shall be the features a.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the charge amount control means is a rotatable brush member.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the rotation direction of the brush member as the charge amount control means is opposite to the rotation direction of the charging roller. To do.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the toner used for image formation is in the range of 100 to 180 in terms of a shape factor SF-1 and has a shape. The coefficient SF-2 is in the range of 100 to 180 .

According to a sixth aspect of the present invention, there is provided a process cartridge which is mounted on the image forming apparatus according to any one of the first to fifth aspects and is configured to be detachable from the main body of the image forming apparatus. In addition, at least one of the developing unit and the charge amount control unit and the image carrier are integrally configured.

According to a seventh aspect of the present invention , a plurality of process cartridges according to the sixth aspect are provided, toner images of different colors are formed on image carriers of the plurality of process cartridges, and the toner images are directly or intermediately transferred to a recording material. It is characterized by being superimposed and transferred through a body to form a multicolor or full color image.

According to the first aspect of the present invention, the charge amount control means is provided with a contact / separation mechanism that selectively contacts either the image carrier or the charging roller, so that the charge amount of the residual transfer toner is optimized and charged. The two functions of cleaning the roller can be performed by one member, and miniaturization and cost reduction are achieved. As a result, the charge amount of the transfer residual toner on the image carrier becomes normal, so that the transfer residual toner becomes difficult to adhere to the charging roller. It is recovered when it comes into contact with the roller and can be returned to the image carrier again.
If the charge amount control means and the charging roller are brought into contact with each other during image formation, the discharge current is distributed to the charge amount control means, so that the charged potential of the photosensitive member may become unstable.
Accordingly, the invention according to claim 1 is characterized in that the contact of the charge amount control means by the contact / separation mechanism with the charging roller is performed at the time of non-image formation, and the charge amount control means is only at the time of non-image formation. By contacting the charging roller with the charging roller, it is possible to clean the toner attached to the charging roller without hindering the discharge of the charging roller. Further, the charge amount control means is always in contact with the image carrier during image formation in which transfer residual toner is generated, so that the entry of toner with an inappropriate charge amount to the charging roller can be minimized.
According to the first aspect of the present invention, when the charge amount control means is in contact with the image carrier, the voltage Vbr1 applied to the charge amount control means is such that the surface potential of the opposite image carrier is Vpc. Then, the relationship Vbr1 <Vpc is satisfied, and the residual transfer that passes through the charge amount control means (brush member) is reduced by making the bias applied to the charge amount control means smaller than the surface potential of the image carrier. In addition to frictional charging, charge can be injected into the toner, and the amount of charge can be controlled more efficiently. In addition, toner that is not normalized but remains in reverse polarity while passing through the brush member is once held in the brush by the electric field, and therefore does not adhere to the charging roller.
In the first aspect of the invention, when the charge amount control means is in contact with the charging roller, the voltage Vbr2 applied to the charge amount control means is such that the potential of the core metal of the opposite charging roller is Vc. Then, the relationship Vbr2 <Vc is satisfied, and the toner adhering to the charging roller is a transfer residual toner having a reverse polarity, but the bias applied to the charge amount control means is set to be higher than the potential of the core of the charging roller. By making it small, it becomes possible to collect the adhered toner from the charging roller to the brush member by an electric field when passing through the charge amount control means (brush member).
According to the first aspect of the present invention, when the charge amount control unit is in contact with the image carrier during non-image formation, the voltage Vbr3 applied to the charge amount control unit is the same as that of the opposite image carrier. It is characterized by having a mode (discharge mode) set so as to satisfy the relationship of Vbr3> Vpc where the surface potential is Vpc, and is temporarily held by the charge amount control means during non-image formation. By applying a voltage to the charge amount control means so that an electric field that discharges the reverse polarity toner to the image carrier is formed, the toner in the charge amount control means is discharged and the brush member is refreshed. In a long term, it is possible to repeatedly optimize the charge amount of the transfer residual toner on the image carrier and collect the toner adhering to the charging roller.

According to a second aspect of the invention, prior Symbol toner remaining on the image carrier without being transferred by the transfer means, said developing means are characterized by simultaneously recovering as the development, the so-called cleanerless structure By doing so, the waste toner mechanism around the image carrier can be eliminated, and the apparatus can be greatly reduced in size. Further, by reusing the transfer residual toner, the running cost can be reduced and the cost can be further reduced. In addition, waste toner can be greatly reduced, which can contribute to reducing the environmental load.

According to a third aspect of the invention, the pre-Symbol charge amount controlling means is characterized by a brush member rotatable by the charge amount controlling means and the brush member (e.g. brush roller), brush the rotation speed The triboelectric charging property can be controlled by changing the number of times of friction between the member and the toner. Therefore, the image carrier can be appropriately charged without excessively charging the toner. When the toner is excessively charged, the toner is difficult to separate from the image carrier due to the mirror image force, and as a result, toner fixation and afterimage are caused. However, the above-described configuration eliminates these problems. Further, the charging roller can increase the rubbing force by rotation and reliably collect the toner from the charging roller.

The invention according to claim 4 is characterized in that the rotation direction of the brush member which is the charge amount control means is opposite to the rotation direction of the charging roller at a position opposite to the rotation direction of the charging roller. Since the roller abuts, the number of times of contact between the brush member and the charging roller is greater than in the forward direction, and the toner collection efficiency is high. At the same time, the brush member appropriately polishes the surface of the charging roller, thereby preventing toner filming.

The invention described in claim 5 is characterized in that the toner used for image formation is in the range of 100 to 180 in terms of the shape factor SF-1 and in the range of 100 to 180 in terms of the shape factor SF-2. As the toner shape approaches the sphere, the transfer rate is improved, and the amount of residual toner can be minimized, resulting in a more stable cleaner-less system.

According to a sixth aspect of the present invention, the process cartridge is provided in the image forming apparatus according to any one of the first to fifth aspects , and is configured to be detachable from the main body of the image forming apparatus. Since at least one of the developing unit and the charge amount control unit and the image carrier are integrally configured, the image forming unit can be easily replaced and assembled, and the maintainability of the image forming apparatus can be improved. it can.

According to a seventh aspect, a plurality of profiles processes cartridge, to form a color different toner image on the image bearing member of the plurality of process cartridges, through the recording material directly or the intermediate transfer member the toner image By superimposing and transferring to form a multicolor or full-color image, a color image forming apparatus having the effect of any one of the first to ninth means and improved maintainability can be provided. .

  Hereinafter, the configuration, operation, and effects of the present invention will be described in detail based on the illustrated embodiments.

FIG. 1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. Here, an embodiment applied to an electrophotographic image forming apparatus will be described.
The image forming apparatus includes yellow (hereinafter referred to as “Y”), cyan (hereinafter referred to as “C”), magenta (hereinafter referred to as “M”), and black (hereinafter referred to as “K”). A color image is formed from four color toners.

  First, a basic configuration of the image forming apparatus will be described. This image forming apparatus includes four photoconductors 1Y, 1C, 1M, and 1K as image carriers in an image forming unit 30. Although a drum-shaped photoconductor is taken as an example here, a belt-shaped photoconductor can also be adopted. The photoconductors 1Y, 1C, 1M, and 1K are arranged in parallel along an intermediate transfer belt 10 as an intermediate transfer body, and are driven to rotate in the direction of the arrow in the drawing while being in contact with the intermediate transfer belt 10. . Each of the photoreceptors 1Y, 1C, 1M, and 1K is obtained by forming a photoconductive photosensitive layer on a relatively thin cylindrical conductive substrate and further forming a protective layer on the photosensitive layer. Further, an intermediate layer may be provided between the photosensitive layer and the protective layer.

  FIG. 2 is a schematic view showing a configuration around one of the four photoconductors 1Y, 1C, 1M, and 1K, and shows a configuration of one image forming unit. Since the configuration around each of the photoconductors 1Y, 1C, 1M, and 1K is the same, only the configuration of one image forming unit is illustrated, and the symbols Y, C, M, and K for color coding are omitted. is there.

  Around the photoreceptor 1, a charge amount control means 40 for controlling the charge amount of the transfer residual toner, a charging device 3 having a charging roller 2 as a charging means, and a developing device 5 as a developing means are arranged in this order. Here, the charge amount control means 40, the charging device 3, the developing device 5 and the photosensitive member 1 of the image forming unit shown in FIG. 2 are integrally formed in a cartridge (not shown) to form a process cartridge. Yes. The process cartridge is configured to be detachable from the image forming apparatus main body. That is, the image forming apparatus shown in FIG. 1 has a configuration in which four process cartridges are detachably arranged along the intermediate transfer belt 10.

  Further, a space is provided between the charging device 3 and the developing device 5 of the image forming unit (process cartridge) shown in FIG. 2 so that light emitted from the exposure device 4 as a latent image forming unit can pass to the photosensitive member 1. Is secured.

  The charge amount control means 40 of the image forming unit (process cartridge) shown in FIG. 2 is connected to the contact / separation means 41, and as shown in FIGS. 3 (A) and 3 (B), the photosensitive member 1 and the charging roller 2 are connected. Either one of them can be brought into contact with the contact / separation means 41. Here, as the contact / separation mechanism, for example, the contact / separation can be switched by the eccentric roller 41B and the spring 41C around the fulcrum 41A of the contact / separation means 41.

  The charge amount control means 40 comes into contact with the toner by contacting and rubbing the photoreceptor 1 or the charging roller 2. As a member constituting the charge amount control means 40, a brush member is desirable, and a brush roller is particularly preferable. The brush shape can increase the surface area, and can improve the recoverability of the transfer residual toner on the photoreceptor and the charging roller.

  For example, the brush-like roller 40 has a configuration in which brush fibers are planted around a metal base material. Here, conductive nylon fiber or the like was used, and the outer diameter of the brush was 10 mm. The density of the brush was set to 50000 (lines / inch ^ 2) to 150,000 (lines / inch ^ 2). As a result, it is possible to simultaneously collect toner from the photoreceptor 1 and release toner to the photoreceptor 1.

  Further, a power source (not shown) is connected to the metal base material of the brush-like roller 40 so that the voltage Vbr can be applied. This power supply is provided with a switch that can apply a plurality of voltages. The brush fiber of the brush roller 40 can be selected from styrene resin, acrylic resin, polyester resin, fluororesin, polyamide resin, and the like. In particular, a polyamide resin that is resistant to wear and has high strength is preferable. In order to increase the effect of bias application, this brush may contain conductive powder. As the conductive powder, carbon black such as acetylene black and furnace black, graphite, or metal powder such as copper and silver can be used. On the other hand, you may use the brush bar which is not a rotary body as another form of a brush member.

  The brush roller 40 is rotatably installed and rotates in the opposite direction at the contact position between the charging roller 2 and the brush. As a result, the toner collection efficiency on the charging roller can be increased, and a function of appropriately polishing the surface of the charging roller can be added. Therefore, toner filming of the charging roller 2 can be prevented, and the toner can be used for a long period of time.

  Next, the charging device 3 used in the image forming apparatus of the present invention will be described. The charging device 3 charges the photosensitive member 1 using proximity discharge. As a method of charging the photosensitive member 1 using proximity discharge, a contact charging method in which a rotatable roller-shaped charging member (hereinafter referred to as a charging roller) 2 is disposed in contact with the photosensitive member 1, and a charging roller 2 is used. There is a non-contact charging method in which is arranged in a non-contact manner on the photoreceptor 1. Here, when the present invention is applied to the contact charging method, it is necessary to use an elastic member that improves the contact property with the surface of the photoconductor and does not apply mechanical stress to the photoconductor. In this case, the width of the charging nip is widened, which makes it easier for toner and foreign matter to adhere to the charging roller side. In particular, in the cleanerless configuration, if the transfer residual toner passes through the charging portion and there are many opportunities to contact the charging roller 2, the charging roller becomes dirty and it is difficult to establish a cleanerless system. Therefore, in the present invention, the non-contact charging method is used in which the charging roller 2 is disposed so as to face at least the image forming area on the surface of the photoreceptor with a predetermined charging gap 114. As a result, the problem of charging roller contamination, which is a problem with the contact charging roller, can be largely eliminated.

  FIG. 4 is a diagram illustrating the configuration of the charging device used in the image forming apparatus of the present invention. A roller 121 constituting the charging roller 2 of the charging device includes a shaft portion 121a and a roller portion 121b. The roller part 121b can be rotated by the rotation of the shaft part 121a, and the part of the surface of the photosensitive member 1 facing the image forming area 111 where an image is formed is not in contact with the photosensitive member 1. The length of the roller 121 of the charging roller 2 is set to be slightly longer than the image forming area, and spacers 122 are provided at both ends in the longitudinal direction. By bringing these two spacers 122 into contact with the non-image forming regions 112 at both ends of the photosensitive member surface, a minute gap (charging gap) 114 is formed between the photosensitive member 1 and the roller portion 121b of the charging roller 2. ing. The minute gap 114 is configured such that the distance at the closest portion between the roller portion 121b of the charging roller 2 and the photosensitive member 1 can be maintained at 5 to 100 [μm]. A more preferable range of the gap 114 is 30 to 65 [μm], and is set to 50 μm in the apparatus of the present invention. Further, the shaft portion 121a is pressed against the photosensitive member side by a pressing spring 115 made of a spring. Thereby, the minute gap 114 can be accurately maintained. The roller 121 of the charging roller 2 rotates along with the surface of the photosensitive member via the spacer 122.

  A charging power source 116 is connected to the roller 121 of the charging roller 2. As a result, the surface of the photoconductor is uniformly charged by proximity discharge in a minute gap between the surface of the photoconductor and the surface of the charging roller. As the applied voltage, only a DC voltage which is a direct current component is applied in the present invention. An alternating voltage on which an AC voltage that is an AC component is superimposed may be used. However, in that case, a countermeasure in consideration of deterioration of the surface of the photoreceptor due to the AC voltage (eg, formation of a protective film by applying ZnSt) is required.

  The roller 121 of the charging roller 2 includes a cored bar (shaft part) 121a as a conductive support having a cylindrical shape and a roller part 121b made of a resistance adjusting layer formed on the outer peripheral surface of the cored bar. The surface of the roller portion 121b of the charging roller 2 is desirably hard. A rubber member can also be used as a member constituting the roller portion 121b. However, if the member is easily deformed, such as a rubber member, it is difficult to maintain the minute gap 114 between the photosensitive member 1 and the charging depending on the image forming conditions. Only the central part of the roller 2 may suddenly contact the surface of the photoreceptor. Since it is difficult to cope with the disturbance of the toner and the fluorine-containing resin caused when the charging roller 2 is locally / suddenly contacted with the surface of the photosensitive member, there is a deflection when the non-contact charging method is used. Less rigid members are desirable.

  Specific examples of the roller 121b of the charging roller 2 having a hard surface include, for example, a thermoplastic resin composition (polyethylene, polypropylene, polymethyl methacrylate, polystyrene, and co-polymers thereof) in which a resistance adjustment layer is dispersed in a polymer type ion conductive agent. And the like, and the surface of the resistance adjusting layer is treated with a curing film with a curing agent. The cured film treatment is performed, for example, by immersing the resistance adjustment layer in a treatment solution containing an isocyanate-containing compound, but may be performed by forming a cured treatment film layer on the surface of the resistance adjustment layer. . In this embodiment, the roller 121 of the charging roller 2 is formed with a diameter of 10 mm (diameter 10 mm).

  An electrostatic latent image corresponding to each color is formed on the surface of the photoreceptor 1 charged by the non-contact charging method using the charging roller 2 as described above by the exposure device 4. The exposure device 4 writes an electrostatic latent image corresponding to each color on the photoreceptor 1 based on image information corresponding to each color. The exposure apparatus 4 of this embodiment is a laser scanning type exposure apparatus composed of a laser light source composed of a semiconductor laser and the like, a coupling optical system, an optical deflector, a scanning optical system, and the like. Other types of exposure apparatus such as a linear exposure apparatus comprising an LED) array and image forming means may be employed.

  As shown in FIG. 2, the developing device 5 has a developing roller 5a as a developer carrying member partially exposed from the opening of the casing. Here, a two-component developer composed of a toner and a carrier is used, but a one-component developer not containing a carrier may be used. The developing device 5 receives toner of the corresponding color from the toner bottles 31Y, 31C, 31M, and 31K shown in FIG. The toner bottles 31Y, 31C, 31M, and 31K are configured to be detachable from the main body of the image forming apparatus so that they can be replaced individually. With such a configuration, only the toner bottles 31Y, 31C, 31M, and 31K may be replaced at the time of toner end. Therefore, other components that have not yet reached the end of their life when the toner ends can be used as they are, and the user's expense can be reduced.

  The toner replenished into the developing device 5 from the toner bottles 31Y, 31C, 31M, and 31K is conveyed while being agitated with the carrier by the agitating and conveying screw 5b, and is carried on the developing roller 5a. The developing roller 5a is composed of a fixed magnet roller as magnetic field generating means and a developing sleeve that rotates coaxially around the magnet roller. The carrier in the developer is transported to the developing region facing the photosensitive member 1 in a state where it stands on the developing sleeve of the developing roller 5a by the magnetic force generated by the magnet roller.

  Here, the developing roller 5 a moves in the same direction at a linear velocity faster than the surface of the photosensitive member 1 in a region facing the photosensitive member 1 (hereinafter referred to as “developing region”). Then, the carrier spiked on the sleeve of the developing roller 5 a supplies the toner adhered to the carrier surface to the surface of the photoconductor 1 while rubbing the surface of the photoconductor 1. At this time, a developing bias VB of −300 V is applied to the developing roller 5a from a power source (not shown), thereby forming a developing electric field in the developing region. Then, between the electrostatic latent image on the photoreceptor 1 and the developing roller 5a, an electrostatic force directed toward the electrostatic latent image side acts on the toner on the developing roller 5a. As a result, the toner on the developing roller 5 a adheres to the electrostatic latent image on the photoreceptor 1. By this adhesion, the electrostatic latent image on the photoreceptor 1 is developed into a corresponding color toner image.

  Further, the developing device 5 collects the transfer residual toner after the transfer simultaneously with the development. As will be described later, the untransferred toner on the photosensitive member whose charge has been normalized is electrostatically collected by positive charges on the carrier surface in the development region when it is carried to the development region. As a result, a so-called cleanerless system that does not require a cleaning device is provided, and the space around the photosensitive member is saved, and the size and cost of the device are reduced. Further, the cost can be further reduced by reusing the toner.

  The intermediate transfer belt 10 in the transfer device 6 is stretched around three support rollers 11, 12, and 13 and is configured to endlessly move in the direction of the arrow in the drawing. On the intermediate transfer belt 10, toner images on the photoreceptors 1Y, 1C, 1M, and 1K are transferred so as to overlap each other by an electrostatic transfer method. Although there is a configuration using a transfer charger in the electrostatic transfer system, a configuration using a transfer roller that generates little transfer dust is adopted here. Specifically, primary transfer rollers 14Y, 14C, 14M, and 14K as transfer devices 6 are disposed on the back surface of the portion of the intermediate transfer belt 10 that contacts the photoreceptors 1Y, 1C, 1M, and 1K, respectively. Here, a primary transfer nip portion is formed by the portions of the intermediate transfer belt 10 pressed by the primary transfer rollers 14Y, 14C, 14M, and 14K and the photoreceptors 1Y, 1C, 1M, and 1K. When transferring the toner images on the photoreceptors 1Y, 1C, 1M, and 1K onto the intermediate transfer belt 10, a positive bias is applied to each primary transfer roller. As a result, a transfer electric field is formed in each primary transfer nip portion, and the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are electrostatically attached to the intermediate transfer belt 10 and transferred.

  A belt cleaning device 15 for removing toner remaining on the surface of the intermediate transfer belt 10 is provided around the intermediate transfer belt 10. The belt cleaning device 15 is configured to collect unnecessary toner adhering to the surface of the intermediate transfer belt 10 with a fur brush and a cleaning blade. The collected unnecessary toner is transported from the belt cleaning device 15 to a waste toner tank (not shown) by a transport means (not shown).

  Further, a secondary transfer roller 16 is disposed in contact with the portion of the intermediate transfer belt 10 stretched around the support roller 13. A secondary transfer nip portion is formed between the intermediate transfer belt 10 and the secondary transfer roller 16, and transfer paper as a recording material is fed into this portion at a predetermined timing. This transfer paper is accommodated in a paper feed cassette 20 on the lower side of the exposure apparatus 4 in the drawing, and is conveyed to the secondary transfer nip portion by a paper feed roller 21, a registration roller pair 22, and the like. Then, the toner images superimposed on the intermediate transfer belt 10 are collectively transferred onto the transfer paper at the secondary transfer nip portion. At the time of the secondary transfer, a positive bias is applied to the secondary transfer roller 16, and the toner image on the intermediate transfer belt 10 is transferred onto the transfer paper by a transfer electric field formed thereby.

  A heat fixing device 23 as a fixing unit is disposed downstream of the secondary transfer nip portion in the transfer paper conveyance direction. The heat fixing device 23 includes a heating roller 23a with a built-in heater and a pressure roller 23b for applying pressure. The transfer paper that has passed through the secondary transfer nip is sandwiched between these rollers and receives heat and pressure. As a result, the toner on the transfer paper is melted and the toner image is fixed on the transfer paper. Then, the fixed transfer paper is discharged by a paper discharge roller 24 onto a paper discharge tray on the upper surface of the apparatus.

  Next, the untransferred toner remaining on the surface of the photoreceptor 1 after the image formation will be described. Among the transfer residual toners, there are a normally charged toner T0 charged to a normal polarity and a reverse charged toner T1 charged to a polarity opposite to the normal polarity. FIG. 5A is a graph showing the toner charge amount distribution immediately before the transfer of the toner carried on the photoreceptor 1. FIG. 5B is a graph showing the toner charge amount distribution of the untransferred toner remaining on the photoreceptor 1 after the transfer. As shown in FIG. 5A, the charge amount of the toner immediately before the transfer is distributed around -30 (μC / g), and most of the charge toner T0 is normally charged negatively. It is. On the other hand, the charge amount of the transfer residual toner is distributed around +5 (μC / g). Part of the untransferred toner has its toner charging polarity reversed to positive polarity due to discharge due to a potential difference between the positive polarity bias applied to the primary transfer roller 14 and the photoreceptor potential in the vicinity of the transfer region. As a result, the reverse transfer toner T1 that has been reversed to the positive polarity as indicated by the hatched portion in FIG. 5B exists in the transfer residual toner.

  When such a reversely charged toner T1 is transported to the charging region of the charging device 3 while adhering to the photosensitive member 1, even when the non-contact charging roller 2 is used as described above, the toner flies by the electric field. As a result, it is electrostatically attracted and attached to the surface of the charging roller 2 to which the negative charging bias is applied. Furthermore, since it is a non-contact charging roller 2, it is difficult for the toner once attached to the roller to return to the photoreceptor 1, and is accumulated on the roller. When the toner adheres to the surface of the charging roller 2, the resistance value and surface state of the charging roller 2 change, resulting in uneven charging start voltage with the surface of the photoreceptor 1. As a result, even if the same charging bias as that when the reversely charged toner T1 is not attached is applied to the charging roller 2, the surface of the photoreceptor 1 does not become uniform at a desired potential of −500 (V). As a result, image density unevenness may also occur.

  In addition, when the toner adheres to a very small part of the surface of the charging roller 2, the current due to the charging bias may be concentrated toward the portion where the toner is not adhered. Thus, when the same charging bias as that in the case where toner is not attached is applied to the charging roller 2, the charging potential on the surface of the photoreceptor 1 becomes higher than a desired potential. As a result, the potential of the portion exposed by the exposure device 4, that is, the electrostatic latent image portion is shifted to the negative polarity side, and the image density is lowered.

  Further, when the toner adheres to almost the entire surface of the charging roller 2 and the surface of the charging roller 2 is coated with the toner, the charging ability is lowered, and the surface potential of the photosensitive member 1 is higher than the desired potential. Go down. As a result, the potential of the portion that is not exposed by the exposure device 4, that is, the non-electrostatic latent image portion (white background portion) approaches the developing bias applied to the developing roller 5a. As a result, the toner that is not sufficiently charged adheres to the background portion on the photoreceptor 1 and an abnormal image such as background stain occurs. In particular, in the case of the non-contact charging roller 2, there is a problem that the change in the charging potential of the photosensitive member due to the contamination of the charging roller is larger than that of the contact charging roller.

  On the other hand, among the transfer residual toner, there is a regular charged toner T0 that remains negative. Even if the regular charging toner T0 is transported to a position facing the charging roller 2 of the charging device 3, if the charging bias is applied, it does not adhere to the surface of the charging roller 2 and reaches the developing region. As a result, most of the regular charged toner T0 attached to the carrier on the developing roller 5a of the developing device 5 is collected.

Therefore, a small and stable cleanerless system can be constructed by performing the following three processes.
First, as a first step, the transfer residual toner having a reverse polarity is normally charged by a brush roller 40 as charge amount control means, and then passed through a charging portion and collected by development. The reverse polarity toner that exists in a small amount of probability adheres to the charging roller 2. However, as a second step, the brush roller 40 is brought into contact with the charging roller 2 by the contact / separation mechanism described above and adheres to the charging roller 2. The toner is collected into the brush roller 40. The reverse polarity toner collected and accumulated by the brush-like roller 40 is gradually normally charged by the contact between the photoconductor 1 and the brush-like roller 40 and discharged to the photoconductor 1, but there are also accumulated reverse-polarity toners. . Therefore, as a third step, the reverse polarity toner accumulated in the brush roller 40 is discharged from the brush roller 40 onto the photosensitive member 1 using the discharge mode to refresh the brush roller 40.

These processes are described in detail below.
Here, as shown in FIG. 6, voltages are applied to members around the photoconductor of each image forming unit of the image forming apparatus of this embodiment so that each bias can be applied. Specifically, the voltage Vbr is applied to the brush roller 40 serving as a charge amount control means, the voltage Vc is applied to the charging roller 2 of the charging device 3, the voltage Vb is applied to the developing roller 5a of the developing device 5, and the primary transfer roller 14 is applied to the primary transfer roller 14. A voltage Vt is applied.

  First, the process of normal charging the transfer residual toner having the reverse polarity, which is the first process, by the brush roller 40 as the charge amount control means will be described below. This process is performed in an image forming mode in which image formation is performed. As shown in FIG. 7, the brush-like roller 40 is in contact with the photosensitive member 1, and each bias is set. Note that the bias shown in FIG. 7 mainly indicates the direction of polarity, and the magnitude of the bias varies depending on the location.

The brush-like roller 40 rotates with the circumferential speed difference from the photosensitive member 1 in the direction of the arrow in FIG. 7, and when the surface potential of the opposing photosensitive member 1 is Vpc,
Vbr1 <Vpc
A voltage is applied so as to satisfy the relationship. As a result, in the brush contact area where the brush roller 40 and the photosensitive member 1 are in contact with each other, an electric field is formed in which a negative charge is injected to the reverse polarity (plus) transfer residual toner on the photosensitive member. , (B) to (c), the charge amount distribution can be changed. Furthermore, it also has the function of normalizing the charge amount by frictional charging by rubbing of the brush-like roller 40. Further, the toner that is not normalized here but remains in reverse polarity is collected and accumulated on the brush-like roller 40 by this electric field. Thus, the reverse polarity toner can be prevented from entering the charging device 3 as much as possible.
The bias values in this embodiment are Vbr1 = −500 [V], Vpc = −50 [V], Vc = −1300 [V], Vb = −350 [V], and Vt = 1000 [V].

  Next, the process of collecting the toner adhering to the charging roller 2 as the second process by the brush roller 40 will be described below. This process is performed at the time of non-image formation, which is an operation in a non-image area where image formation is not performed. As shown in FIG. 8, the brush roller 40 contacts the charging roller 2 and each bias is switched. Is set to If the brush roller 40 as the charge amount control means and the charging roller 2 are brought into contact with each other at the time of image formation, the discharge potential is distributed to the charge amount control means, so that the charging potential of the photoreceptor 1 may become unstable. There is sex. Therefore, the toner adhering to the charging roller 2 can be collected without interfering with the discharge of the charging roller 2 by contacting the charging roller 2 with the brush roller 40 serving as the charge amount control means only during non-image formation. Further, since the brush roller 40 as the charge amount control means is always in contact with the photosensitive member 1 at the time of image formation in which the transfer residual toner is generated, it is possible to minimize the reverse polarity toner from entering the charging roller 2. .

The brush roller 40 serving as the charge amount control means rotates counterclockwise with the charging roller 2 in the direction of the arrow in FIG. 8, and the potential applied to the metal core (shaft portion) of the opposite charging roller 2 at that time is Vc. Then,
Vbr2 <Vc
Meet the relationship. As a result, in the brush contact area where the brush roller 40 and the charging roller 2 are in contact, the transfer residual toner having the opposite polarity (plus) attached to the charging roller 2 is drawn toward the brush roller 40 by the electric field. To the brush-like roller 40. However, this electric field is preferably a smaller electric field than the electric field between the brush roller 40 and the photoreceptor 1 in the previous step. This is because when a strong electric field is formed and electric charge is injected, the transfer residual toner is made negative on the charging roller, and may not be collected by the brush roller 40. Here, the reverse polarity toner is moved from the charging roller 2 to the brush roller 40 by the movement of the reverse polarity toner due to the weak electric field and the mechanical brush-like roller 40 is rubbed.
The bias values in this embodiment are Vbr2 = −200 [V], Vc ′ = 0 [V], Vb ′ = + 200 [V], and Vt ′ = − 500 [V].

  When this second step is completed, the brush-like roller 40 again comes into contact with the photosensitive member 1 and returns to the first step to perform image formation. At this time, the reverse polarity toner collected from the charging roller 2 is accumulated in the brush roller 40, but in the first step, charge injection is always performed in the brush contact area, so most of the reverse polarity toner is normally charged. Thus, it is discharged onto the photoreceptor. However, the reverse polarity toner that is not normally charged is discharged from the brush-like roller 40 by performing a discharge process that is a third process shown below.

  Next, the discharge process of the reverse polarity toner accumulated in the brush roller 40, which is the third process, will be described below. This step is performed during non-image formation, which is an operation in a non-image area where image formation is not performed. As shown in FIG. 9, the brush-like roller 40 comes into contact with the photosensitive member 1 and each bias is switched. Is set to

The brush-like roller 40 rotates in the direction of the arrow in FIG. 9, and when the surface potential of the opposing photoconductor 1 is Vpc,
Vbr3> Vpc
A voltage is applied so as to satisfy the relationship. As a result, in the brush contact area where the brush-like roller 40 and the photosensitive member 1 are in contact, the toner of reverse polarity (plus) adhering to the brush-like roller 40 is pulled toward the photosensitive member 1 by the electric field, and the brush-like roller 40. To the photosensitive member 1. The reverse polarity toner returned from the brush-like roller to the photoreceptor 1 first passes through the charging roller 2. At this time, since the bias applied to the charging roller 2 is switched to 0 [V] as shown in FIG. 9, the reversely charged toner is not attracted to the charging roller 2 by an electric field, and the charging roller is maintained as it is. 2 and the photoreceptor 1 pass through. Next, the reverse polarity toner that has passed through the charging roller 2 passes through the developing portion of the developing device 5. At this time, since the bias applied to the developing roller 5a is switched to the positive polarity as shown in FIG. 9, the reverse polarity toner passes through the developing device without returning. For this reason, there is no possibility of color mixing or toner scattering due to poorly charged toner. Next, the reverse polarity toner that has passed through the developing unit enters the transfer unit. Here, as shown in FIG. 9, the transfer bias is set to a reverse polarity to that during normal image formation, and a transfer electric field is formed in the direction in which the reverse polarity toner is transferred from the photosensitive member to transfer the transfer bias to an intermediate transfer belt or the like. Reverse polarity toner is transferred to the material. Thereafter, the reverse polarity toner is collected by a cleaning member installed downstream of the intermediate transfer belt.
The bias values in this embodiment are Vbr3 = + 300 [V], Vc ′ = 0 [V], Vb ′ = + 200 [V], and Vt ′ = − 500 [V].

Next, the concrete timing which can be implemented when performing said 2nd process and 3rd process is demonstrated.
As specific timings for performing the second step and the third step, basically, the photosensitive member 1 moves during operation outside the image forming area (non-image forming), in the following cases. It can be implemented.
1) Pre-processing (from start of print job to before image formation)
2) Between papers (between image formation areas during continuous print jobs)
3) Post-processing (from the end of image formation until the end of the print job and the photoreceptor stops)
4) When the power is turned on and when returning from the sleep state 5) During regular computer operation other than the image forming job (color adjustment, registration correction, image forming condition adjustment, etc. are performed during the so-called waiting time)
6) During return operation after an abnormal stop such as jam handling or cover open

Next, specific conditions for returning to the first step or the third step after the second step and an example of the control are shown below.
The image forming apparatus according to the present exemplary embodiment includes a detection unit that detects the amount of toner attached to the brush-like roller 40, and a control unit of the image forming apparatus (not shown) performs the third step based on the determination of the detection unit. Is determined as shown in the flowchart of FIG.
In the flowchart of FIG.
START: Start image forming job
1 ^st Process: First process
2 ^nd Process: the second step
3 ^rd Process: a third step Mb: sensed brush toner amount M0: a predetermined amount of toner
END: End of image forming job (returns to START for continuous printing)
It is.

  Here, as a specific embodiment for controlling whether or not the third step is performed based on the judgment of the detection means, as in the following (1), means for indirectly estimating the toner amount of the brush roller 40 And a method of controlling using a means for directly measuring the characteristic value of the brush roller 40 and detecting the toner amount, as in (2).

(1) Control using indirect detection means There are the following three types of control using indirect detection means.
(1-1) A counter for accumulating the number of printed sheets is provided. When the predetermined number is reached, the process proceeds to the third step.
(1-2) A counter for integrating the number of rotations of the photosensitive member is provided, and when the predetermined number of times is reached, the process proceeds to the third step.
(1-3) A pixel counter capable of integrating the output image area for each color is provided. When the predetermined number of pixels is reached, the process proceeds to the third step.

(2) Control using direct detection means There are the following two types of control using direct detection means.
(2-1) A resistance measuring unit for measuring the resistance value of the brush of the brush roller 40 is provided, and when the predetermined resistance value is reached, the process proceeds to the third step (when the toner adhering to the brush increases, the resistance value of the brush Increase). As the resistance measuring means, for example, as shown in FIG. 11, an electrode E that contacts the brush roller 40, a power source (electrode bias applying power source) Ve for applying a voltage to the electrode E, and a current flowing through the power source Ve are detected. And a voltage applied to the brush roller 40 by a brush bias application power source Vbr at a predetermined timing to measure the resistance value of the brush.
(2-2) A toner amount measuring means for measuring the amount of toner adhering to the brush of the brush-like roller 40 is provided. When the toner amount reaches a predetermined amount, the process proceeds to the third step. As the toner amount measuring means, for example, as shown in FIG. 12, an optical sensor PD for detecting a diffuse reflection component of light, a transparent electrode TE, and a power source (electrode bias applying power source) Ve for applying a voltage to the electrode are provided. Then, a voltage at which toner adheres to the transparent electrode TE is applied at a predetermined timing, and light is projected onto the toner attached to the transparent electrode TE from the light emitting portion d1 of the photosensor PD from the side opposite to the brush roller 40. The amount of toner can be detected by receiving the irregular reflection component by the light receiving portion d2 of the optical sensor PD (the intensity of the irregular reflection light increases according to the amount of toner). Here, assuming that the amount of toner adhering to the transparent electrode TE is proportional to the amount of toner adhering to the brush of the brush-like roller 40, the amount of toner adhering to the brush is detected.

  As described above, in the image forming apparatus according to the present exemplary embodiment, a contact / separation mechanism is provided so that the brush roller 40 serving as the charge amount control unit contacts only one of the photosensitive member 1 and the charging roller 2. As a result, it is possible to perform two functions, that is, the optimization of the charge amount of the transfer residual toner and the cleaning of the charging roller 2 with one member, thereby achieving miniaturization and cost reduction. As a result, the charge amount of the transfer residual toner on the photosensitive member is normalized, so that the transfer residual toner becomes difficult to adhere to the charging roller 2, and the brush-like roller 40 is also attached to the charging roller 2 when it adheres to the charging roller 2. It is collected when it contacts the charging roller 2 and can be returned to the photoreceptor 1 again.

  Further, in the image forming apparatus of this embodiment, the transfer residual toner that is not transferred by the transfer unit and remains on the photosensitive member is collected by the developing device 5 at the same time as the development. The waste toner mechanism around the body can be eliminated, and the apparatus can be greatly reduced in size. Further, by reusing the transfer residual toner, the running cost can be reduced and the cost can be further reduced. In addition, waste toner can be greatly reduced, which can contribute to reducing the environmental load.

  Further, in the image forming apparatus of this embodiment, the contact of the brush roller 40 with the charging roller 2 by the contact / separation mechanism is performed at the time of non-image formation, and the brush roller 40 and the charging roller 2 are contacted only at the time of non-image formation. By doing so, the toner adhering to the charging roller 2 can be cleaned without disturbing the discharge of the charging roller 2. Further, the brush roller 40 is always in contact with the photosensitive member 1 at the time of image formation in which the transfer residual toner is generated, and the entry of toner with an inappropriate charge amount to the charging roller 2 can be minimized.

  Further, in the image forming apparatus of the present embodiment, the charge amount control means is, for example, the brush-like roller 40, so that the triboelectric chargeability can be controlled by changing the number of times of friction between the brush-like roller 40 and the toner according to the number of rotations. it can. Therefore, the photoreceptor 1 can be appropriately charged without excessively charging the toner. Further, if the toner is excessively charged, it becomes difficult for the toner to separate from the photoreceptor 1 due to the mirror image force, and as a result, toner fixation and an afterimage are caused. However, the above configuration eliminates these problems. Further, the charging roller 2 can increase the rubbing force by rotation and reliably collect the toner from the charging roller 2.

  Further, in the image forming apparatus of this embodiment, since the brush roller 40 and the charging roller 2 are in contact with each other in the counter direction, the number of contact between the brush roller 40 and the charging roller 2 is larger than that in the forward direction, and the toner collection efficiency is increased. Is expensive. At the same time, the brush roller appropriately polishes the surface of the charging roller, thereby preventing toner filming.

  Further, in the image forming apparatus of this embodiment, when the brush-like roller 40 is in contact with the photoreceptor 1, the voltage Vbr1 applied to the brush-like roller 40 is such that the surface potential of the opposing photoreceptor 1 is Vpc. , Vbr1 <Vpc is satisfied, and the bias applied to the brush-like roller 40 is made smaller than the surface potential of the photosensitive member 1, whereby the transfer residual toner passing through the brush-like roller 40 is frictionally charged. In addition to charge injection, the charge amount can be controlled more efficiently. Further, toner that is not normalized but remains in reverse polarity while passing through the brush-like roller 40 is once held in the brush by an electric field, and therefore does not adhere to the charging roller 2.

  Furthermore, in the image forming apparatus of this embodiment, when the brush roller 40 is in contact with the charging roller 2, the voltage Vbr2 applied to the brush roller 40 is the potential of the core metal of the opposite charging roller 2 Vc. Then, the relationship Vbr2 <Vc is satisfied, and the toner adhering to the charging roller 2 is a transfer residual toner having a reverse polarity, but the bias applied to the brush roller 40 is set to the potential of the core of the charging roller 2. By making it smaller than that, the adhering toner can be collected from the charging roller 2 to the brush roller 40 by an electric field when passing through the brush roller 40.

  Further, in the image forming apparatus of the present embodiment, when the brush roller 40 is in contact with the photoreceptor 1 during non-image formation, the voltage Vbr3 applied to the brush roller 40 is the surface of the opposing photoreceptor 1. When the potential is Vpc, a reverse polarity toner temporarily held by the brush roller 40 during non-image formation is provided by providing a mode (discharge mode) that is set to satisfy the relationship of Vbr3> Vpc. By applying a voltage to the brush roller 40 so that an electric field that discharges the toner to the photosensitive member 1 is formed, the toner in the brush roller 40 is discharged and the brush roller 40 is refreshed. In particular, the charge amount of the transfer residual toner on the photosensitive member can be optimized and the toner adhering to the charging roller 2 can be collected repeatedly.

Next, toner used in the image forming apparatus having the above-described configuration will be described.
The toner suitably used in the image forming apparatus of the present embodiment includes a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent are dispersed in an organic solvent. 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 between a polyhydric alcohol (PO) and a polycarboxylic acid (PC) is carried out in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, and heated to 150 to 280 ° C. 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-diisocyanatomethylcaproate, 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, polyisocyanates; Those blocked with caprolactam or the like; and combinations 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, low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1, when a urea-modified polyester is used, the urea content in the ester is lowered and hot offset resistance is deteriorated.

  The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 wt%, the low-temperature fixability deteriorates.

  The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester will be low, and the hot offset resistance will deteriorate.

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

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

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

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

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

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

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

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

  By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the gloss when used in the full-color image forming apparatus 100 are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.

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

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

The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If it is less than 45 ° C., the heat resistance of the toner deteriorates, and if it exceeds 65 ° C., the low-temperature fixability becomes insufficient.
In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

(Coloring agent)
As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher , Yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Sayred, Parachlor Ortonito Aniline 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, Thio Indigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red Polyazo 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, Lid Russian nin 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 PSY VP2038, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEG VP2036, copy charge NX VP434 (manufactured by Hoechst), LRA-901, LR-147 which is a boron complex (Nippon Carlit) Manufactured), copper phthalocyanine, perylene, quinacridone, azo series Fee, a sulfonic acid group, a 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. 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 petrolatum. And petroleum wax. In addition to these natural waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax, and synthetic waxes such as esters, ketones, and ethers can be used. Furthermore, fatty acid amides such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbon, and low molecular weight crystalline polymer resin, poly-n-stearyl methacrylate, poly-n- A crystalline polymer having a long alkyl group in the side chain such as a homopolymer or copolymer of polyacrylate such as lauryl methacrylate (for example, a copolymer of n-stearyl acrylate-ethyl methacrylate, etc.) can also be used. .

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

(External additive)
Inorganic fine particles are preferably used as an external additive for assisting the fluidity, developability and chargeability of the toner particles. The primary particle diameter of the inorganic fine particles is preferably 5 × 10 −3 to 2 μm, and particularly preferably 5 × 10 −3 to 0.5 μm. Moreover, it is preferable that the specific surface area by BET method is 20-500 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 size of 5 × 10-2 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, a fluidity-imparting agent is not detached from the toner, a good image quality that does not cause fireflies and the like is obtained, and a reduction in residual toner is further achieved. .

  Titanium oxide fine particles are excellent in environmental stability and image density stability, but have a tendency to deteriorate the charge rise characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, this side effect is affected. It can be considered large. However, when the addition amount of the hydrophobic silica fine particles and the hydrophobic titanium oxide fine particles is in the range of 0.3 to 1.5 wt%, the charge rising characteristics are not greatly impaired, and the desired charge rising characteristics can be obtained, that is, printing or copying. Even if the above is repeated, stable image quality can be obtained.

  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 (methylcellosolve, 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).

  Moreover, as the cationic surfactant, aliphatic quaternary ammonium such as aliphatic primary, secondary or secondary amic acid, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt which has a right fluoroalkyl group is used. Salt, 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) Smoke), Megafac F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footage 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 names are PB-200H (manufactured by Kao Corporation), SGP (manufactured by Soken Co., Ltd.), Techno Examples include polymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), and micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.).
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, the high-speed shearing method is preferable in order to make the particle size of the dispersion 2 to 20 μm. When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C.

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

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

(5) A charge control agent is injected into the toner base particles obtained above, and then inorganic fine particles such as silica fine particles and titanium oxide fine particles are externally added to obtain a toner.
The injection of the charge control agent and the external addition of the inorganic fine particles are performed by a known method using a mixer or the like.
Thereby, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the true spherical shape and the rugby ball shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. be able to.

Next, the shape of the toner will be described.
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. FIGS. 13A and 13B are diagrams schematically illustrating the shape of the toner in order to explain the shape factor SF-1 and the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape, and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting toner onto a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) 2 / AREA} × (100π / 4) Formula (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). This is a value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π.
SF-2 = {(PERI) 2 / AREA} × (100 / 4π) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.) and introducing it into an image analyzer (LUSEX3: manufactured by Nireco). 100 pieces were analyzed and 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 photosensitive member becomes a point contact, so that the adsorbing force between the toners becomes weak, and thus the fluidity becomes high. The attracting power with the body also becomes weaker, and the transfer rate becomes higher. On the other hand, if any of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  In the image forming apparatus of the present invention, the toner used for image formation is in the range of 100 to 180 in terms of the shape factor SF-1 and in the range of 100 to 180 in terms of the shape factor SF-2. Since the transfer rate is improved by approaching the sphere, the amount of residual toner can be minimized, and a more stable cleaner-less system can be configured.

1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a main part of a configuration of one image forming unit of the image forming apparatus illustrated in FIG. 1. It is a figure which shows an example of a structure and operation | movement of the contact / separation means of a charge amount control means. FIG. 3 is an explanatory diagram of a configuration of a charging device used in the image forming apparatus of the present invention. (A) is a graph showing the toner charge amount distribution immediately before the transfer of the toner carried on the photoconductor, (b) is a graph showing the toner charge amount distribution of the untransferred toner remaining on the photoconductor after the transfer, (c) ) Is a graph showing a toner charge amount distribution when negative charge injection is performed on a transfer residual toner having a reverse polarity (plus) on the photosensitive member. FIG. 3 is an explanatory diagram of a bias voltage applied to members around the photoconductor of the image forming unit shown in FIG. 2. It is a figure which shows the setting state of the bias at the time of performing a 1st process in the image creation part shown in FIG. It is a figure which shows the setting state of the bias at the time of performing a 2nd process in the image creation part shown in FIG. It is a figure which shows the setting state of the bias at the time of performing a 3rd process in the image creation part shown in FIG. It is a flowchart which shows an example of the control which determines whether a 3rd process is performed by judgment of a detection means. It is a figure which shows an example of a direct detection means, Comprising: It is a figure which shows the structural example of the resistance measurement means which measures the resistance value of the brush of a brush-like roller. It is a figure which shows another example of a direct detection means, Comprising: It is a figure which shows the structural example of the toner amount measurement means which measures the quantity of the toner adhering to the brush of a brush-like roller. FIG. 6 is a diagram schematically illustrating the shape of a toner in order to explain the shape factor SF-1 and the shape factor SF-2 of the toner.

Explanation of symbols

1 (1Y, 1C, 1M, 1K): photoconductor (image carrier)
2: Charging roller 3: Charging device 4: Exposure device (latent image forming means)
5: Developing device (developing means)
5a: developing roller 5b: stirring and conveying screw 6: transfer device (transfer means)
10: Intermediate transfer belt (intermediate transfer member)
11, 12, 13: Support roller 14 (14Y, 14C, 14M, 14K): Primary transfer roller 15: Belt cleaning device 16: Secondary transfer roller 20: Paper feed cassette 21: Paper feed roller 22: Registration roller pair 23: Heat fixing device (fixing means)
24: Paper discharge roller 31Y, 31C, 31M, 31K: Toner bottle 40: Brush roller (charge amount control means)
41: Contact / separation means (contact / separation mechanism)

Claims (7)

An image carrier for carrying an electrostatic latent image;
A charging roller that charges the surface of the image carrier in a non-contact manner in proximity to the image carrier;
Latent image forming means for forming a latent image on the image carrier;
Developing means for developing a toner image by attaching toner to the latent image of the image carrier;
Transfer means for transferring the toner image on the image carrier to a recording material directly or via an intermediate transfer member;
Charge amount control means for controlling the charge amount of the transfer residual toner on the image carrier;
In an image forming apparatus comprising at least
A contact / separation mechanism for selectively bringing the charge amount control means into contact with either the image carrier or the charging roller ;
Detecting means for detecting the amount of toner adhering to the charge amount control means ,
The contact of the charge amount control means to the charging roller by the contact / separation mechanism is performed during non-image formation,
When the charge amount control means is in contact with the image carrier at the time of image formation, the voltage Vbr1 applied to the charge amount control means is given by assuming that the surface potential of the opposing image carrier is Vpc.
Vbr1 <Vpc
Satisfy the relationship
When the charge amount control means is in contact with the charging roller, the voltage Vbr2 applied to the charge amount control means is Vc when the potential of the metal core of the opposite charging roller is Vc.
Vbr2 <Vc
Satisfy the relationship
When the charge amount control means is in contact with the image carrier during non-image formation, the voltage Vbr3 applied to the charge amount control means is given by assuming that the surface potential of the opposite image carrier is Vpc.
Vbr3> Vpc
Equipped with a discharge mode set to satisfy the relationship
The image forming apparatus, wherein the discharge mode is executed based on a detection result of the detection unit. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the transfer residual toner remaining on the image carrier without being transferred by the transfer means is collected simultaneously with development by the developing means. The image forming apparatus according to claim 1 or 2,
The image forming apparatus according to claim 1, wherein the charge amount control means is a rotatable brush member . The image forming apparatus according to claim 3 .
The image forming apparatus according to claim 1, wherein a rotation direction of the brush member serving as the charge amount control unit is opposite to a rotation direction of the charging roller . The image forming apparatus according to any one of claims 1 to 4, wherein:
An image forming apparatus characterized in that the toner used for image formation is in the range of 100 to 180 in terms of the shape factor SF-1 and in the range of 100 to 180 in terms of the shape factor SF-2 . A process cartridge that is mounted on the image forming apparatus according to any one of claims 1 to 5 and configured to be detachable from the image forming apparatus main body.
A process cartridge comprising at least one of the charging roller, the developing unit, and the charge amount control unit, and the image carrier . A plurality of process cartridges according to claim 6,
Forming toner images of different colors on the image carriers of the plurality of process cartridges, and transferring the toner images onto a recording material directly or via an intermediate transfer member to form a multicolor or full color image An image forming apparatus.

Images