JP5493410B2 - Cleaning device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a cleaning apparatus that cleans residual toner on an intermediate transfer member.

  Conventionally, in an image forming apparatus such as an electrophotographic copying apparatus, a toner image formed on an image carrier is primarily transferred to an intermediate transfer member, and the primary transfer image on the intermediate transfer member is secondarily transferred to a transfer material. What to do is known. In such an image forming apparatus, all of the primary transfer image formed on the intermediate transfer member remains on the intermediate transfer member without being secondarily transferred to the transfer material, and adversely affects the next transfer. Therefore, a cleaning device for cleaning the intermediate transfer member is provided. This cleaning device uses a brush or a roller as a cleaning member, and is widely used not only in a copying machine but also in a printer, a facsimile, a complex machine of these, and the like.

  In recent years, in color image forming apparatuses, which have been the mainstream, in addition to plain paper that has been widely used as a transfer material, the use of special transfer paper that is used for thermal transfer such as special paper with a rough surface or iron print as a design The frequency tends to increase. When such special paper is used, transfer defects may occur when transferring the toner image on the intermediate transfer member on which the color toners are superimposed, compared with the case of using plain paper, and the image quality is deteriorated. End up. In view of this, an intermediate transfer member carrying a toner image, for example, an intermediate transfer belt, is given elasticity to improve contact with special paper during transfer.

  Toners used in image formation tend to be smaller in size in order to meet the demands of higher image quality from users. From the viewpoint of reducing manufacturing costs and improving transfer rate, they are made spherical by a polymerization method instead of pulverized toner. The frequency of use is increasing. Along with this, in the blade cleaning system that has been mainly used as a means for removing toner remaining on the image carrier after image formation, the blade is made to contact the image carrier to remove the toner. If the degree of adhesion between the toner and the image carrier is low, the toner slips through and the cleaning property tends to deteriorate. If the blade is pressed against the image carrier with a strong pressure to prevent this, the blade will turn over and cause streaky or band-like cleaning failure, making it difficult to maintain stable cleaning performance. Become. Even a spherical toner can be cleaned if the linear pressure is extremely high (for example, 100 gf / cm or more), but the life is extremely shortened due to wear of the cleaning blade, scratches on the belt, and the like. The life of the cleaning blade when using a normal linear pressure of 20 gf / cm (the life until scraping occurs and a cleaning failure occurs) is about 120 kp, whereas the life of the cleaning blade when using a linear pressure of 100 gf / cm is about 120 kp. The lifetime is about 20 kp.

  In addition, it is well known that cleaning with a blade for spherical toner, which has good transferability, is inferior to that for ground (unshaped) toner. Further, when the blade is pressed against the elastic belt, the contact state becomes unstable and cleaning failure is likely to occur. Due to the transition between the intermediate transfer belt and the toner, the intermediate transfer belt cleaning device cannot be handled by the conventional blade system, and various improvements have been made. For example, in electrostatic cleaning, there is a problem that toner charged to the same polarity as the voltage applied to a cleaning member such as a cleaning roller or a cleaning brush cannot be removed, and a problem that a large amount of toner processing or multilayer toner processing cannot be performed instantaneously. In order to solve the problem, for example, “Patent Document 1” has been proposed.

  Conventionally, the toner to be cleaned (secondary transfer residual toner) has a charge distribution that is not as uniform and sharp as that after development, but a distribution from minus to plus across zero. In particular, electrostatic cleaning cannot be performed with a toner whose charge is near zero because the toner is not charged. Further, it is difficult to process a large amount of toner or a multi-layer toner, and a multi-layer toner process is also required during the process control described below.

  In order to maintain high image quality and high reliability, a color image forming apparatus must detect various characteristic values and feed back to the image control system. When a certain number of images are output repeatedly, toner replenishment control that controls the developer concentration at a constant level so that there is no change in color, or toner is transported from the toner cartridge containing the toner to the developer. When toner transport control is performed so that there is no toner clogging at the time, the toner concentration of the developer is detected by a magnetic sensor, and control for supplying toner or transporting toner when the toner concentration drop falls below a threshold is well known. It is. In addition to the magnetic sensor detection control, control is also performed in which a toner image is formed on the image carrier and the density is read by a photosensor. The control for reading a toner image with a photosensor is more configured to read each color toner on the intermediate transfer body after transferring each color toner to the intermediate transfer body than to read each toner color on the developed image carrier. Can be reduced and the cost is reduced. These toner images are not transferred to the transfer material, but are removed and collected by an intermediate transfer member cleaning device.

  In addition, control for correcting color misregistration is also performed. At this time, a toner image is formed on the intermediate transfer member and read by a photo sensor, and the amount of misregistration is detected to detect the latent image on the image carrier. Although the image writing position is corrected, the read toner image is removed and collected by the cleaning device without being transferred to the transfer material. As described above, in the intermediate transfer body cleaning device, untransferred toner may be processed in addition to residual transfer toner remaining on the intermediate transfer body after being transferred to the transfer material. Since the processing amount is 5 to 10 times as large as that, there is a problem that the margin of brush cleaning is lowered and cleaning cannot be performed.

In the technique disclosed in “Patent Document 1”, since the toner recovery member aligns the polarity of the toner with the regular charge and scrapes off a part of the toner, it seems that the above-described problem has been solved. However, the following problems have arisen.
A material having high resistance is used for the intermediate transfer belt of the image forming apparatus, but there is a tendency to use a belt having a reduced volume resistivity ρv in order to prevent afterimages and repeat fluctuations due to belt residual charges. In the example disclosed in “Patent Document 1”, the resistance is 106 to 1014 Ω · cm, and a low resistance belt of 106 Ω · cm can be used. However, when a low resistance belt is used, the polarity of the toner is difficult to control even if a voltage is applied by bringing the toner polarity control blade into contact with the belt holding the toner. This is because the toner held on the belt has a high resistance of 10 ¹⁰ to 10 ¹¹ Ω / cm ² , so that it is difficult to inject charges compared to the belt, and the voltage applied to the toner polarity control blade is the volume resistivity. This is because it flows to a metal counter roller that is grounded through a low belt. According to the study by the inventors, the Q / M value after polarity control did not become a desired value when a metal counter roller was used even with a belt having a volume resistivity of 108 Ω · cm.

  By the way, when performing polarity control with the polarity control member, it is necessary to control transfer residual toner and reverse transfer toner having various charge amount distributions to a single polarity. Since it is necessary to have a toner charge amount distribution that does not generate toner, it is necessary to apply a sufficient voltage to the polarity control member. As a result, the inventors have found that the toner charge amount after polarity control has a broader distribution than toner polarity control in a corona charger. Further, in order to control all the transfer residual toner processed by the polarity control member with a wide Q / d distribution as shown in FIGS. 8A and 8B to a single polarity, the transfer shown in FIG. A low charge amount toner such as the residual toner A becomes a single charge high charge amount toner after polarity control, and a positively charged toner such as the transfer residual toner B shown in FIG. Later, it becomes a unipolar low charge toner. Although the measurement variation was large, the Q / M value of the transfer residual toner A was approximately −10 to +10 μC / g, and the Q / M value of the transfer residual toner B was approximately +30 to +60 μC / g.

  It is well known that low charge toner is cleaned with a weak cleaning electric field and high charge toner is cleaned with a strong cleaning electric field. However, when the toner having a low charge amount is placed under a strong electric field, opposite polarity charges are injected and reattached on the image carrier. In other words, the toner after polarity control has a single charge but has a broad charge amount distribution from a low charge amount to a high charge amount as described above, so the applied voltage to the cleaning member is a high charge amount. It is necessary to set the applied voltage so that the low charge amount toner is not reattached by the charge injection while the voltage is high enough to clean the toner. In other words, the toner charge amount distribution needs to be such that cleaning is possible when the applied voltage to the cleaning member is constant.

  Here, since it takes a lot of time to measure the toner charge amount distribution, the Q / M value that can be measured in a relatively short time is used as the substitute characteristic. When the ratio of the negative polarity toner in the sampling toner for which the toner charge amount distribution is measured is a negative toner rate, the relationship between the negative toner rate and the Q / M value is measured under various conditions as shown in FIG. According to the study by the inventors, it has been found that the polarity of the toner to be measured is controlled to a substantially single polarity when measured by the toner charge amount distribution measuring method described below. The toner Q / M range when the toner of the image carrier can be cleaned when a voltage of opposite polarity is applied to the cleaning member is approximately −50 to −100 μC / g in the case of negative polarity. . The toner Q / M (amount of charge per unit weight of toner) and the toner charge amount distribution are measured as follows.

(Toner Q / M)
A toner patch pattern is formed on the image carrier, and after completion of each process such as development, transfer, and polarity control, the main switch of the image forming apparatus main body is forcibly turned off, and the apparatus is stopped in the middle of the image formation. While the toner image formed on the image carrier or the transfer belt is sucked with an air pump using a suction jig, the amount of coulomb of the toner is measured with a coulomb meter (Electrometer 617 manufactured by Kessley Co., Ltd.). The toner charge amount (μC / g) per unit weight is calculated from the weight of the sucked toner and the coulomb amount.

(Toner Q / d distribution)
Measure with an E-SPART analyzer manufactured by Hosokawa Micron. The toner adhering to the image carrier is blown off with air and dropped onto the measuring unit, and the particle size and the charge amount of each toner are measured. “Charge amount Q / toner particle size d” on the X axis, Y axis Is calculated and graphed by calculating “frequency (%) = preset (charge amount / toner particle size) number (number) / total number of samples (number)) × 100 in the range of histogram”.

  The polarity to be controlled is the relative polarity of the voltage applied to the polarity control member when the image carrier surface potential is used as a comparison target. For example, when the surface potential of the image carrier is −100 V and the voltage applied to the polarity control member is −700 V, “I want to control the toner to a negative polarity”. As described above, in the electrostatic cleaning method using toner polarity control + single polarity application brush, it is important that the polarity of the toner entering the cleaning brush is uniform and the charge amount is an appropriate value.

  As a second problem, there is a problem related to the stability of the polarity control member. In the present invention, as will be described later, a so-called conductive rubber blade obtained by adding carbon or an ionic conductive agent to a polyurethane rubber blade to impart conductivity is used as a polarity control member. This conductive rubber blade scrapes off the toner on the image carrier while having excellent conductivity, and the load on the surface of the image carrier is small compared to a hard material such as a metal blade. While having the advantage that the toner can be removed without damaging the surface, there is a disadvantage that the resistance value fluctuates depending on environmental conditions and use over time as compared with a metal blade that does not change its resistance value. According to the study by the inventors, it was found that the resistance increase is accelerated particularly when a large current (about 200 μA or more) flows. The reason for this has not been elucidated, but is thought to be caused by alteration of the conductive material. According to the study by the inventors, if the current flows through the polarity control member at 200 μA or more, the deterioration speed increases and it cannot be used for a long time, and if it is less than about 100 μA, it can be used without any problem although there is a slight increase in resistance. There was found. Therefore, it is necessary to prevent a large current from flowing when using the conductive rubber blade. When the volume resistance of the image carrier is high, even if a high voltage is applied to the polarity control member (conductive rubber blade), the current flowing toward the grounded opposing roller is small, so the polarity control performance is maintained. However, an increase in resistance of the polarity control member can be prevented.

A third problem is that polarity control cannot be performed when a low-resistance image carrier is used. The intermediate transfer belt of the image forming apparatus has a relatively high resistance. However, a belt having a reduced volume resistivity ρv tends to be used in order to prevent afterimages and repeat fluctuations due to belt residual charges. When such a low resistance belt is used, it is difficult to control the polarity of the toner even if a voltage is applied by bringing the polarity control member into contact with the belt holding the toner. Since the toner held on the belt has a high resistance of 10 ¹⁰ to 10 ¹¹ Ω, electric charges are less likely to be injected compared to the belt, and the voltage applied to the polarity control member is grounded via the belt having a low volume resistivity. Therefore, it is impossible to maintain the potential difference between the polarity control member and the surface of the image carrier, which is the function that is originally desired to be performed, and therefore the polarity control performance of the toner on the image carrier cannot be maintained. . As described above, in order to stabilize the polarity control performance, it is necessary to prevent a current from flowing in the direction of the opposing roller.

  SUMMARY An advantage of some aspects of the invention is that it provides a cleaning device that can satisfactorily control the polarity of residual toner and an image forming apparatus using the same.

According to the first aspect of the present invention, there is provided an electroconductive member for controlling the charging polarity of toner to be removed from the surface of the image bearing member in contact with the surface of the image bearing member, and electrostatically controlling the toner whose charging polarity is controlled. A cleaning member for cleaning, and a grounded opposing member provided in contact with the back side of the image carrier at a position facing the conductive member, and the image carrier has a volume resistivity of 1 × 10 ⁹ to 1 × 10 ¹⁴ Ωcm, and the opposing member is coated with a conductive resin or conductive rubber having a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹² Ωcm, and the image carrier and the opposing member are The conductive member is configured to be groundable.

A second aspect of the present invention is the cleaning apparatus according to the first aspect, further comprising a polarity control member made of conductive rubber as the conductive member .

According to a third aspect of the present invention, in the cleaning apparatus according to the second aspect , the polarity control member is a blade .

According to a fourth aspect of the present invention, there is provided an electroconductive member that controls the charging polarity of toner to be removed from the surface of the image bearing member in contact with the surface of the image bearing member, and the toner whose charging polarity is controlled electrostatically. A cleaning member for cleaning, and a grounded opposing member provided in contact with the back side of the image carrier at a position facing the conductive member and the cleaning member, and the image carrier has a volume resistivity. 1 × 10 ⁹ to 1 × 10 ¹⁴ Ωcm, and the opposing member is covered with a conductive resin or conductive rubber having a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹² Ωcm, and the image carrier and The conductive member and the cleaning member are configured to be groundable through the opposing member.

According to a fifth aspect of the present invention, in the cleaning apparatus according to any one of the first to fourth aspects, the cleaning member further includes conductive fibers from the outer periphery of the conductive cored bar in the diametrically outer side. A brush roller that is planted so as to extend to the surface and is rotatable while being in contact with the surface of the image carrier, and is capable of rotating while being in contact with the fiber and having an electrical resistance layer or insulating layer on its outer peripheral surface A roller, means for applying a voltage to the core, means for applying a voltage to the collection roller, a collection roller cleaner for scraping off the toner collected by the collection roller, and the collection roller in contact with the collection roller and a charge imparting mechanism to maintain the surface potential of the collection roller gives a charge to the surface of the roller constant, the brush roller resistance value is 10 ⁶ to 10 ⁸ Omega And wherein the door.

  According to a sixth aspect of the present invention, in the cleaning device according to the fifth aspect, the fibers further have a layer structure, and the layer structure does not expose a conductive material imparting conductivity to the fibers on the surface. It is characterized by having.

  According to a seventh aspect of the present invention, in the cleaning device according to the fifth or sixth aspect, a lubricant is brought into contact with the brush roller, the lubricant is applied to the image carrier through the brush roller, and the It has a blocking member for preventing the toner scattered from the brush roller from adhering to the image carrier.

According to an eighth aspect of the present invention, in the cleaning device according to the first or fourth aspect , the conductive resin or the conductive rubber is a tube .

According to a ninth aspect of the present invention, in the cleaning device according to any one of the first to eighth aspects, the image carrier is a belt .

A tenth aspect of the invention is an image forming apparatus having the cleaning device according to any one of the first to ninth aspects .

According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect , a photoconductor as the image carrier, a toner image forming unit for forming a toner image on the photoconductor, and a photoconductor on the photoconductor. Primary transfer means for primary transfer of the formed toner image to an intermediate transfer body as an image carrier, and secondary transfer means for secondary transfer of the toner image primarily transferred onto the intermediate transfer body to a recording material The cleaning device performs cleaning of the intermediate transfer member .
According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, the intermediate transfer member is a belt having an elastic layer having a thickness of 0.07 to 0.3 mm.
According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the tenth to twelfth aspects, the volume average particle diameter is 3 to 8 μm, and the volume average diameter (Dv) and the number average particle diameter ( A toner having a ratio (Dv / Dn) to Dn) in the range of 1.00 to 1.40 is used.

  According to the present invention, the polarity control performance can be obtained stably over time.

1 is a schematic front view of a main part of an image forming apparatus employing an embodiment of the present invention. 1 is a schematic front view of a main part of an image forming unit of an image forming apparatus employing an embodiment of the present invention. 1 is a schematic view of an intermediate transfer belt cleaning device employing a first embodiment of the present invention. It is the schematic for demonstrating the subject of this invention. It is a diagram which shows the relationship between the polarity control current in one Embodiment of this invention, and the Q / M value after polarity control. It is the schematic explaining the principle of toner polarity control of this invention. FIG. 6 is a diagram illustrating a relationship between a Q / M value and a negative toner rate in an embodiment of the present invention. In the first embodiment of the present invention, (a) When the polarity of the transfer residual toner is controlled by 50% plus and minus (b) When the polarity of the transfer residual toner is mostly positive (c) Mostly minus FIG. 6 is a diagram showing a Q / d distribution change when the polarity of the untransferred toner is controlled. It is a schematic enlarged view of the polarity control part used for the 1st Embodiment of the present invention. It is a graph which shows the blade conditions used for the 1st embodiment of the present invention. It is a table | surface which shows the blade conditions used for the 1st Embodiment of this invention. FIG. 6 is a schematic view of an intermediate transfer belt cleaning device that employs a second embodiment of the present invention. FIG. 6 is a schematic view of an intermediate transfer belt cleaning device used in a modification of the first embodiment of the present invention. It is a diagram which shows the cleaning property when resistance of the brush used for the 1st Embodiment of this invention is logR = 5,7,9. FIG. 10 is a schematic view of an intermediate transfer belt cleaning device that employs a modification of the second embodiment of the present invention. In the second embodiment of the present invention, (a) when the polarity of the transfer residual toner is controlled by 50% plus and minus (b) when the polarity of the transfer residual toner is mostly positive (c) most of the minus FIG. 6 is a diagram showing a Q / d distribution change when the polarity of the untransferred toner is controlled. 1 is a schematic front view illustrating a configuration around a photoconductor of an image forming apparatus employing an embodiment of the present invention. It is a schematic front view of the color printer as an image forming apparatus which employ | adopted the 3rd Embodiment of this invention. FIG. 3 is a schematic diagram schematically showing the shape of a toner in order to explain the shape factor SF-1 of the toner used in one embodiment of the present invention. FIG. 3 is a schematic diagram schematically showing the shape of a toner for explaining a toner shape factor SF-2 used in an embodiment of the present invention. FIG. 3 is a schematic diagram schematically illustrating the shape of a toner used in an embodiment of the present invention. It is a diagram which shows the relationship between logR and Q / M value after polarity control in one Embodiment of this invention. It is a diagram which shows the relationship between logR and Q / M value after polarity control in one Embodiment of this invention. FIG. 3 is a cross-sectional view illustrating a configuration of an intermediate transfer belt used in an embodiment of the present invention.

  FIG. 1 shows an internal configuration of a printer as an image forming apparatus employing a tandem indirect transfer system, and FIG. 2 shows details of an engine. This printer has four drum-shaped photoconductors 2a, 2b, 2c, and 2d arranged in parallel at substantially the center of the apparatus main body 1, and each of the photoconductors 2a to 2d can be rotated clockwise. It is configured. Around the photoreceptors 2a to 2d, which are image carriers, there are neutralization devices (not shown) that neutralize the surfaces of the photoreceptors 2a to 2d, charging devices 3a to 3d that uniformly charge the surfaces of the photoreceptors 2a to 2d, and lasers. An exposure device 4 for forming an electrostatic latent image on the charged portions of the photoconductors 2a to 2d by optical writing with light, developing devices 5a to 5d for developing the electrostatic latent image, and photoconductors 2a to 2d after transfer. Cleaning devices 7a to 7d for cleaning the surface are respectively provided. This printer employs a so-called tandem method using four photoconductors, and the image forming component configuration provided around each of the photoconductors 2a to 2d is a color material (developed by the developing devices 5a to 5d). The toner (color, yellow, magenta, cyan, black) is the same except for different colors (the components of the four sets of PCU will be described with the photoreceptor 2, the charging device 3, the developing device 5, and the cleaning device 7). The description of the same components in other colors is omitted).

  An intermediate transfer unit 10 is provided above the photoreceptors 2a to 2d. The intermediate transfer unit 10 has an intermediate transfer belt 11 as an image carrier as a member to be cleaned. The intermediate transfer belt 11 is wound around a driving roller 12, support rollers 13, 14, 15 and a counter roller 16. In FIG. 2, it is driven to run in the counterclockwise direction. The intermediate transfer belt 11 may have a multilayer structure or a single layer structure. For example, the base layer is made of a fluororesin, PVD sheet, or polyimide resin that has little elongation, and the surface thereof is smooth such as a fluororesin. In this embodiment, it is formed of a polyimide resin having a two-layer structure.

  At a position facing the photoconductors 2a to 2d across the intermediate transfer belt 11, primary transfer as primary transfer means for primary transfer of the toner images formed on the photoconductors 2a to 2d to the intermediate transfer belt 11 is performed. Rollers 6 a to 6 d are disposed, and an intermediate transfer belt cleaning device that removes residual toner remaining on the intermediate transfer belt 11 after secondary transfer by a secondary transfer roller 8 described later is disposed on the left side of the counter roller 16. 20 is arranged. The counter roller 16 has a function of applying a constant tension to the intermediate transfer belt 11 and also serves as a counter roller that is a counter member of the intermediate transfer belt cleaning device 20. The necessary condition as the counter roller does not necessarily have to have a function of applying a constant tension as described above, and a roller that rotates following the rotation of the image carrier may be the counter roller.

  A secondary transfer roller 8 as a secondary transfer unit is disposed at a position facing the driving roller 12 via the intermediate transfer belt 11. In this embodiment, the secondary transfer roller 8 is used as the secondary transfer unit. However, instead of the secondary transfer roller 8, a belt or the like that is stretched by several support rollers and drive rollers is used as the secondary transfer unit. Also good.

Below the apparatus main body 1, a paper feed cassette 17 containing recording paper is disposed therein, and the uppermost recording paper in the paper feed cassette 17 is fed one by one by rotation of the paper feed roller. Then, it is conveyed to the registration roller pair 18. Above the secondary transfer roller 8, a fixing device 9 for fixing the transferred image transferred onto the recording paper is disposed. The secondary transfer roller 8 also has a sheet conveying function for conveying the recording paper after image transfer to the fixing device 9.

  In the printer having the above-described configuration, when an image forming operation is started by pressing a start key (not shown) or the like, the drive roller 12 is rotationally driven by the operation of a drive motor (not shown), and the support rollers 13, 14, 15 and the counter roller 16. Is driven to drive the intermediate transfer belt 11 in the direction of the arrow in FIG. At the same time, the photoconductors 2a to 2d rotate in the image forming units, and yellow, magenta, cyan, and black single-color images are formed on the photoconductors 2a to 2d, respectively. The formed single color images are sequentially superimposed and transferred onto the intermediate transfer belt 11 as the intermediate transfer belt 11 rotates to form a composite color image. On the other hand, recording sheets are fed one by one from the sheet feeding cassette 17, and the fed recording sheets are abutted against the registration roller pair 18 and temporarily stopped. Then, the registration roller pair 18 rotates in synchronization with the composite color image on the intermediate transfer belt 11, and the recording paper is fed between the intermediate transfer belt 11 and the secondary transfer roller 8. The composite color image is transferred to the fed recording paper by the action of the secondary transfer roller 8. The recording paper after the image transfer is sent to the fixing device 9 by the secondary transfer roller 8, and the transferred image is fixed by the action of heat and pressure in the fixing device 9 and then discharged outside the apparatus. Some toner remains on the intermediate transfer belt 11 after image transfer, and the intermediate transfer belt 11 is prepared for the next image formation by removing the residual toner by the intermediate transfer belt cleaning device 20.

  FIG. 3 shows a schematic configuration of the intermediate transfer belt cleaning device 20 adopting the first embodiment of the present invention. In the figure, the intermediate transfer belt cleaning device 20 is configured to place a polarity control blade 21, which is a conductive member for controlling the polarity of residual toner on the intermediate transfer belt 11, at a position facing the counter roller 16. The conductive brush 22, which is in contact with the surface, is a cleaning member for cleaning the polarity-controlled toner in the subsequent process of the polarity control blade 21, that is, on the downstream side in the running direction of the intermediate transfer belt 11. And a collecting roller 23 for collecting the toner adhering to the conductive brush 22; and a conductive roller as a collecting roller cleaner that scrapes the collected toner in contact with the surface of the collecting roller 23 and simultaneously applies a charge to the surface of the collecting roller 23. Collected in a waste toner tank (not shown) provided in the toner collection blade 24 and the apparatus main body 1 Coil member 25 for conveying, and a brush facing roller 28 or the like which is disposed at a position facing the electrically conductive brush 22 via the intermediate transfer belt 11.

  A brush surface charge imparting member (not shown) that imparts a charge to the surface of the conductive brush 22 may be added. This brush surface charge imparting member is a conductive member provided to supplement the potential to prevent the potential at the tip of the brush from lowering when a large amount of toner is collected on the brush, such as a metal round bar or It is a metal plate-like member. Further, since the surface of the intermediate transfer belt 11 is always rubbed by the polarity control blade 21, it is also effective to apply a lubricant to the surface with a brush from the viewpoint of protecting the surface of the intermediate transfer belt 11. In this case, it is good also as a structure apply | coated by making the electroconductive brush 22 contact | abut the solidified lubricant 32 (refer FIG. 12) mentioned later. In addition, a coating blade that forms a thin film on the surface of the intermediate transfer belt 11 with a lubricant applied with a brush may be provided to improve the lubricity.

  A configuration in which the lubricant is applied to the surface of the intermediate transfer belt 11 using a brush for applying a lubricant separately from the conductive brush 22 is also possible. According to this configuration, since the toner is always collected on the cleaning conductive brush 22, the toner and the lubricant are mixed with each other, and the toner once collected at the time of applying the lubricant adheres again to the intermediate transfer belt 11. It is possible to prevent the occurrence of malfunctions.

Next, the problem of the present invention will be described with reference to FIG. In the figure, symbol R1 indicates a toner polarity control blade resistance, and symbol R2 indicates an intermediate transfer belt resistance.
A conventional image forming apparatus uses a high-resistance intermediate transfer belt. As an example, the surface resistivity logR = 10.5 to 11.5, the volume resistivity logR = 10 to 11, and the thickness 100 μm. In this case, even if a voltage is applied to the polarity control blade 21, even if the opposing roller 16 (blade facing roller) that is grounded is a low-resistance material such as metal, the voltage applied from the polarity control blade 21 A large current did not flow through the thickness direction of the intermediate transfer belt 11 on the counter roller 16 side, and charge could be given to the residual toner on the intermediate transfer belt 11.

  In this manner, the intermediate transfer belt resistance R2 (the resistance obtained from the current flowing from the polarity control blade 21 to which the voltage is applied instead of the volume resistivity to the metal roller grounded via the intermediate transfer belt 11 and the applied voltage of the polarity control blade 21. When the value) is sufficiently large, a potential difference is generated between the surface potential of the intermediate transfer belt 11 and the polarity control blade 21, and the toner on the intermediate transfer belt 11 is charged, so that the polarity can be controlled. On the other hand, when the resistance R2 is not sufficiently large, a current flows to the ground via the intermediate transfer belt 11 and the counter roller 16, so that the toner cannot be charged and the polarity cannot be controlled. The intermediate transfer belt 11 whose resistance R2 is not sufficiently large is a belt having a low volume resistivity in a pseudo manner, and is used to prevent the occurrence of abnormal images due to residual charges. The belt used here had a volume resistivity R of log R = 8 when 100 V was applied.

  As described above, the toner polarity control experiment was performed by inserting the known resistor R3 between the metal facing roller and the ground in order to prevent the current from flowing too much. When three types of resistors R3 of 0.5M, 5M, and 20M are used and voltage is controlled by applying a voltage to the polarity control blade 21 by constant current control, the result shown in FIG. −100 μC / g could not be obtained. Although the current value can be suppressed to a low level only by connecting a resistor between the metal facing roller and the ground, the circuit shown in FIG. 6 is obtained. In the figure, the counter roller has a potential calculated by V3 = R3 × I. Therefore, it is considered that even if the resistance value of the known resistor R3 is increased, the potential of the opposing roller also increases, so that the Q / M value after polarity control does not change.

  As described above, when using an intermediate transfer belt whose resistance value is not sufficiently high, polarity control cannot be performed by measures such as simply using a conductive bearing having a predetermined resistance value so as to keep current small. It has been found. Therefore, even if a low resistance belt is used, a resistance layer is provided on the surface of the opposing roller so that the same polarity control as that of the high resistance belt can be performed, and thus the Q / M value after the target polarity control can be obtained. The possible polarity control could be performed.

  From the above, even when a relatively low resistance belt of logR = 8 was used, it seemed that polarity control was possible by providing a high resistance layer on the surface of the opposing roller. A serious problem occurred. It has been found that when the polarity control is continuously performed, the absolute value of the Q / M value decreases with time as shown in FIG. Hereinafter, this phenomenon will be described.

As shown in FIG. 22, a counter roller provided with a high resistance layer is used for a belt of log = 8, and a metal counter roller is used for a belt of log = 9 or more. When the image forming operation was performed on the sheet, in all cases, the Q / M value after polarity control could be controlled in the range of −50 to −100 μC / g. Thereafter, when the polarity control was continued up to 20000 sheets, it was found that the absolute value of the Q / M value after the polarity control was lowered and deviated from the desired range. The reason for this is not clear, but the physical phenomenon that controls toner polarity is considered to be dominated by the discharge phenomenon, and in order to stabilize this discharge, the surface of the image carrier must have the ability to hold charges. Has been found to be necessary. Therefore, even if a high resistance layer is provided on the surface of the opposing roller facing the polarity control member on the back side of the image carrier, the amount of current can be regulated, but the discharge cannot be stabilized. In order to always sustain the discharge from the polarity control member toward the surface of the image carrier, it is necessary to have a high resistance surface capable of holding electric charges, and the resistance required for the image carrier is the volume resistivity. The result of being 10 ⁹ to 10 ¹⁴ Ω · cm was obtained. When the volume resistivity exceeds 1 × 10 ¹⁴ Ω · cm, the volume resistance is the same as that of the image carrier, and when the image carrier is a photoconductor, the polarity can be controlled over 100,000 sheets over time. It is confirmed that the high resistance layer of the counter roller is unnecessary.

  Next, toner polarity control will be described with reference to FIGS. 8A, 8B, and 8C. 8 (a) and 8 (b) show the results shown in FIG. 2 under certain conditions based on data obtained by measuring the charge amount Q of each toner and the particle diameter d of the toner using an E-spurt analyzer manufactured by Hosokawa Micron. This represents a Q / d (unit: fC / μm) distribution when hundreds of transfer residual toner on the intermediate transfer belt 11 when an image is formed by an image device is sampled.

  FIG. 8A shows a case where the polarity of the transfer residual toner A in which plus and minus are 50% each is controlled by the polarity control blade 21, and FIG. When controlled, FIG. 8C shows the Q / d distribution change when the polarity control blade 21 controls the polarity of mostly negative untransferred toner.

  The transfer residual toner on the intermediate transfer belt 11 is a toner having a distribution in which positive polarity and negative polarity are mixed as shown as transfer residual toner A in FIG. 8A and transfer residual toner B in FIG. The intermediate transfer belt 11 is moved to the position of the polarity control blade 21 by the traveling of the intermediate transfer belt 11. Most of the toner is mechanically scraped off by the polarity control blade 21, but a so-called stick slip occurs in the polarity control blade 21, and a part of it slips through. The toner that has been mechanically scraped off naturally falls from the blade and is accommodated in the collecting unit, and is conveyed by the coil member 25 and collected in the waste toner collecting unit.

  A voltage having the same polarity (minus polarity) as the charging polarity of the toner is applied to the polarity control blade 21, and when the toner passes through the polarity control blade 21, the toner is charged to the normal charging polarity (minus polarity). . For example, when the applied voltage is set to −80 μA by constant current control, this control current value may change depending on conditions such as belt resistance and thickness. FIG. 8A and FIG. 8B show the Q / d distribution of the controlled toner. The Q / d distribution after the polarity control differs depending on the Q / d distribution of the transfer residual toner as the input toner (difference between the transfer residual toner A and the transfer residual toner B), but both can be controlled to be almost unipolar. . In addition, the non-transferred toner (toner at the time of process control) having a normal polarity and Q / d distribution in the case of FIG. 8C hardly changes or is slightly negative.

  Next, the details when the charging polarity of the toner passing through the polarity control blade 21 to which the voltage (negative polarity) having the same polarity as that of the toner is applied will be described. The surface resistivity of the polarity control blade 21 is logR = 6 to 9 Ω · cm, the contact pressure with the intermediate transfer belt 11 is 20 to 40 g / cm, and the counter contact is configured.

The polarity control blade 21 is an elastic body made of, for example, polyurethane rubber, and is made conductive by kneading carbon black or other ionic conductive agent. Its surface resistance is 2 × 10. ^{About 5 to} 5 × 10 ⁹ Ω · cm ² is desirable. The blade conditions are as shown in FIGS. The polarity control blade 21 is composed of a plate-like member bonded on a sheet metal, and has two types of thicknesses of 2.4 mm and 2.8 mm, a free length of 7 and 9 mm, and a hardness of 60 to 80 with a JIS-A hardness meter. A rebound resilience of 45% was used, but other values can be used. The thickness is preferably in the range of 1 to 3 mm. If the thickness is too thin, it is difficult to ensure the amount of pressing to the intermediate transfer belt 11 due to the surface of the intermediate transfer belt 11 and the undulation of the polarity control blade 21 itself. Hardness should just be in the range of 40-85 with a JIS-A hardness meter. In the brush cleaning method shown in this embodiment, the toner amount per unit area that can be brush-cleaned (hereinafter referred to as M / Amg / cm ² ) is about 0.1 mg / cm ² , and the M / Since A is much larger than this value, the slip-through amount from the polarity control blade 21 needs to be reduced to about 0.1 mg / cm ² or less.

  When the toner is sandwiched between the polarity control blade 21 and the intermediate transfer belt 11, the toner is discharged by the discharge of a minute gap between the entrance and the exit of the wedge formed by the intermediate transfer belt 11 and the polarity control blade 21. Is charged to the same polarity as the applied voltage, as shown in FIG. 8A and FIG. 8B as “after passing through the blade (current −80 μA applied)”.

  As described above, the characteristic value of the Q / d distribution is used in confirming whether or not the polarity is controlled. However, since it takes considerable time to measure the Q / d distribution, as described above, A Q / M value that can be easily measured was substituted. As shown in FIG. 7, the polarity of the toner to be measured is controlled to be almost a single polarity, that is, “after passing through the blade (current −)” in FIGS. 8 (a), 8 (b), and 8 (c). The range of the Q / M value of the toner of “80 μA)” was approximately −50 to −100 μC / g in the case of negative polarity. Therefore, in the following description, the target value for toner polarity control will be described as −50 to −100 μC / g.

  Next, the relationship between the intermediate transfer belt resistance and the polarity control will be described with reference to FIG. As described above, the intermediate transfer belt used in the conventional image forming apparatus uses a surface resistivity logR = 10.5 to 11.5, a volume resistivity logR = 10 to 11 and a thickness of 100 μm. In this case, even if a voltage is applied to the polarity control blade 21, even if the grounded counter roller 16 (blade facing roller) is a low resistance material such as metal, the voltage control blade 21 applies the voltage to the counter roller. A large current did not flow through the thickness direction of the intermediate transfer belt 11 on the side 16, and charge could be given to the residual toner on the intermediate transfer belt 11. As described above, when the intermediate transfer belt resistance R2 is sufficiently large, a potential difference is generated between the surface of the intermediate transfer belt 11 and the polarity control blade 21, and the toner on the intermediate transfer belt 11 is charged. Control is possible. On the other hand, if the intermediate transfer belt 11 whose resistance R2 is not sufficiently large is used, a current flows to the ground via the intermediate transfer belt 11 and the counter roller 16 when a voltage is applied to the polarity control blade 21, so that the toner is charged. There was a problem that polarity control could not be performed without being given. The intermediate transfer belt whose resistance R2 is not sufficiently large is a belt having a low volume resistivity, and is used to prevent abnormal images due to residual charges. The intermediate transfer belt 11 used in this embodiment has a volume resistivity R of 100V and a log R = 8.

  The intermediate transfer belt 11 is applied with −80 μA using a stainless counter roller 16 having no resistance layer on the surface, the counter roller 16 is grounded, and an A3 size magenta monochromatic solid image is output. When the upper residual toner passes through the polarity control blade 21, the image forming apparatus is turned off to forcibly stop the intermediate transfer belt 11, and before and after the position where the polarity control blade 21 is in contact with the intermediate transfer belt 11. When the Q / M value was measured, the Q / M value of the toner on the intermediate transfer belt 11 before the blade was only about −30 μC / g, and the target Q / M value was not obtained. The target Q / M value could not be obtained even when the voltage applied to the polarity control blade 21 was variously changed to −40 μA, −60 μA, and −100 μA.

A configuration and method capable of performing toner polarity control by the polarity control blade 21 even when the intermediate transfer belt 11 having such a low intermediate transfer belt resistance R2 is used will be described with reference to FIGS. FIG. 9 is an enlarged view of the polarity control unit of FIG.
As shown in FIG. 9, the resistance layer 26 is provided on the surface of the opposing roller 16 with a thickness of 50 to 300 μm. By adopting the configuration having the resistance layer 26 that covers the surface of the opposing roller 16 as a resistor, the resistance of the opposing roller 16 can be set to a desired value with an inexpensive configuration. The shaft of the opposing roller 16 and the roller base are made of metal and are grounded. Examples of the material constituting the resistance layer 26 include a nylon tube, a PVDF tube, a polyimide tube, and a conductive rubber tube mixed with a conductive agent. Further, acrylic coating, silicone coating (for example, coating with PC (polycarbonate) containing silicone particles), ceramic coating, fluorine coating, or the like may be applied to the surface. The thickness of the coating layer is appropriately selected. For example, in the case of a UV curable acrylic coating, it is about 3 to 20 μm. In the case of this configuration, even if the intermediate transfer belt resistance R2 is low, the toner can be charged with the resistance layer 26 on the surface of the counter roller 16, and the polarity control is performed for up to about 2000 sheets as a result of the experiment. Could be done. The principle will be described below with reference to the block diagram shown in FIG. 5 and the circuit diagram shown in FIG.

  In the above-described configuration, the polarity control blade 21 serves as an electrode, and thus it is desirable that the surface resistance or volume resistance is sufficiently low. In this embodiment, a conductive blade prepared by adding carbon and an ionic conductive agent as a conductive agent to polyurethane rubber is used, and log R = 5 to 6 or more in order to maintain the mechanical strength and elasticity as a rubber blade. It is necessary to make the addition amount so that the resistance value becomes. That is, in order to maintain the mechanical strength, it is desirable not to increase the addition amount of the conductive agent so much. Therefore, the role of the electrode is preferably low resistance, and in order to maintain the toner scraping performance as a blade, it is necessary to have as high resistance as possible with logR = 5 to 6 or more. It was found that logR = about 5-9. However, as described above, there is a problem that the resistance of the blade increases with the passage of time of use, and if the resistance of the conductive blade at the time of a new article is set high, the blade resistance increases with time, for example, the polarity control blade voltage is increased. When the constant current control is used, the necessary voltage value rises to a considerably high voltage, which causes a problem that a high cost power source capable of outputting a high voltage is required. Therefore, in order to maintain two performances of scraping off the toner while controlling the polarity of the toner, the resistance value of the toner polarity control blade is preferably logR = 5-9.

  With this configuration, the polarity of the untransferred toner can be made uniform with a simple configuration, and the amount of toner entering the conductive brush 22 can be reduced. In addition, the image carrier surface can be made less likely to be scratched compared to a metal blade, and good image formation can be performed.

  A resistance layer (resistance: R3) having a resistance equivalent to the resistance R2 of the intermediate transfer belt 11 is provided on the surface layer of the opposing roller 16. In the model of FIG. 6, assuming that the resistance of the polarity control blade 21 is R1, the resistance of the intermediate transfer belt 11 is R2, and the resistance of the surface layer of the counter roller 16 is R3, the total resistance R of this circuit is roughly R = R1 + R2 + R3. It is estimated. However, the resistances R1, R2, and R3 are values measured under the same condition as the contact width of each member and the same condition as the voltage application condition in the apparatus configuration for controlling the charging polarity of the toner. In addition, since each member of the intermediate transfer belt 11, the polarity control blade 21, and the resistance layer has a so-called “medium resistance” resistance value, the resistance value varies depending on the environment and usage time, and is measured several times under the same conditions. Even so, the measured values may vary slightly.

  As can be seen from FIG. 6, the voltage applied to the toner whose polarity is to be controlled is proportional to the ratio of the intermediate transfer belt resistance to the total resistance of the circuit. Therefore, it is originally desirable that the resistance of the intermediate transfer belt is high, but there are cases where lowering the resistance is an indispensable condition due to problems such as residual charges in the intermediate transfer belt 11 as described above. Therefore, when the low resistance intermediate transfer belt is employed, it is necessary to make R2 / R as large as possible and make the current flowing through the polarity control blade 21 as small as possible. For that purpose, R1 + R3 is preferably equal to or slightly larger than R2. In the range of the assumed intermediate transfer belt resistance and polarity control blade resistance, if (R1 + R3) <R2, the current value increases and polarity control cannot be performed.

  Based on the above, the following examination was conducted. In the experiment, the secondary transfer current value is set higher than usual so that the performance can be understood, and the Q / M value of the residual toner on the intermediate transfer belt 11 before toner polarity control is set to +30 μC / g. A voltage controlled to −80 μA by a constant current control power source was applied to ground the counter roller 16 and the toner Q / M value after contact with the polarity control blade 21 was investigated. Here, since the volume resistivity R of the intermediate transfer belt 11 is logR = 8 when a voltage of 100 V is applied, it is considered that a counter roller surface layer having a larger resistance value is desirable. Therefore, the volume resistivity logR = 8-14. Up to this point was investigated. A conductive nylon tube having a volume resistivity logR = 8, 9 and thicknesses of 100 μm and 150 μm, and a conductive PVDF tube having a volume resistivity logR = 10 to 14 and a thickness of 100 μm wound around the surface is used as an opposing roller for the polarity control blade 21. A polarity control experiment was conducted after installation. The results are shown in the table below.

表１から明らかなように、体積抵抗率ｌｏｇＲ＝８〜１２の範囲において良好な極性制御が可能であった。また、極性制御可能な対向ローラ表層の場合、極性制御電流値はー６０〜―８０μＡであった。この極性制御電流値は大きければ大きいほど極性制御後Ｑ／Ｍ値の絶対値が大きくなる傾向があるが、電流値が大きすぎるとＱ／Ｍ値の絶対値が低下するため各条件によって適正値がある。その理由は詳細には判明していないが、電流値が大きすぎると放電が過剰に起こり、空気中のイオンを電離してそのイオンが正負共にトナーに付着するためであると考えられる。このように、対向ローラの表層に体積抵抗率ｌｏｇＲ＝８〜１２の抵抗層を設けることにより、低抵抗中間転写ベルトにおいても初期的には良好にトナー極性制御を行うことができた。

As apparent from Table 1, good polarity control was possible in the range of volume resistivity logR = 8-12. Further, in the case of the opposite roller surface layer capable of polarity control, the polarity control current value was −60 to −80 μA. The larger the polarity control current value is, the larger the absolute value of the Q / M value after polarity control tends to be. However, if the current value is too large, the absolute value of the Q / M value decreases. There is. The reason for this is not known in detail, but it is considered that excessive discharge occurs when the current value is too large, ionizing ions in the air, and the ions adhere to the toner both positively and negatively. As described above, by providing a resistance layer having a volume resistivity logR = 8 to 12 on the surface layer of the counter roller, toner polarity control can be satisfactorily controlled even in the low resistance intermediate transfer belt initially.

From the above, it seemed that polarity control was possible by providing a high resistance layer on the surface of the opposing roller even when a relatively low resistance belt of logR = 8 was used. When the polarity control is continuously performed, it has been found that the absolute value of the Q / M value decreases with time as shown in FIG. 22. Therefore, the polarity control member is opposed to the back side of the image carrier. Although the amount of current can be regulated even if a high resistance layer is provided on the surface of the opposite roller, the polarity control member conducts when the surface is in contact with the surface of the image carrier, and the current flows. The body can not sustain a stable discharge. In order to always maintain the discharge from the polarity control member toward the surface of the image carrier, it is considered necessary to have a high resistance surface capable of holding charges.

  On the other hand, even in the case of an image carrier having a high volume resistivity that has been considered not to require a high resistance layer on the opposing roller, the absolute value of the Q / M value after polarity control over time as shown in FIG. It was found that the value decreased. This is because the blade resistance did not fluctuate greatly over time although there was some fluctuation, so the change in contact condition such as sag or wear of the polarity control member caused the change between the polarity control member and the image carrier. It is considered that the minute gap, which is the discharge location between the contact area and the polarity control member and the image carrier, is gradually changed to a state where discharge is difficult to occur.

  From the above results, in order to further stabilize the discharge, the polarity control can be performed by using the high resistance counter roller originally used for improving the polarity controllability of the low resistance belt for the belt having a high volume resistivity. The current flowing from the member to the opposing roller with the shaft core grounded is further reduced, and the dielectric thickness of the discharge nip, where the discharge is occurring, is increased to increase the charge held on the surface of the image carrier, thereby preventing the discharge. An experiment was conducted for the purpose of stabilization. The results are shown in FIG.

In FIG. 23, polarity control is performed using an image carrier with log R = 8 to 12.5 and a counter roller provided with a high resistance layer on the surface, and the polarity control Q is applied after 2000 sheets and 20000 sheets, respectively. / M value measured. As shown in the figure, the absolute value of the Q / M value after polarity control after 20,000 sheets decreased in the image carrier with logR = 8, but after 20,000 sheets in the image carrier with logR = 9 to 12.5. Also, the Q / M value after the polarity control was almost the same as that after 2000 sheets. From this, it was confirmed that the resistance of the image carrier needs to have a volume resistivity in the range of 1 × 10 ⁹ to 1 × 10 ¹⁴ Ωcm. Here, when the volume resistivity is larger than 1 × 10 ¹⁴ Ωcm, the volume resistivity is equivalent to that of the photoconductor, and the photoconductor having a volume resistivity of 1 × 10 ¹⁴ Ωcm in which the image carrier is coated with a photosensitive layer on an aluminum drum. As a result, it was confirmed that polarity control was performed over 100,000 sheets over time, and it was found that the high resistance layer of the opposing roller is unnecessary.

  Next, a cleaning operation after toner polarity control will be described. In FIG. 3, the toner charged to the normal charging polarity by the polarity control blade 21 is transported by the travel of the intermediate transfer belt 11 to a position corresponding to the conductive brush 22. The conductive brush 22 is made of conductive polyester, and a collection roller 23 is provided so as to be in contact with the conductive brush 22. The conductive brush 22, the collection roller 23, and the coil member 25 are rotationally driven by driving means (not shown). A voltage (positive polarity) opposite to the charging polarity of the toner is applied from the power source to the metal core of the conductive brush 22, and the toner that has passed through the polarity control blade 21 is electrostatically adsorbed. The toner that has moved onto the conductive brush 22 moves from the power source to the collecting roller 23 applied with a positive polarity voltage higher than that of the conductive brush 22 by a potential gradient. The toner on the collection roller 23 is scraped off by the conductive collection blade 24 and is discharged out of the apparatus by the coil member 25 or returned to the developing unit. In order to maintain the surface potential of the collection roller 23, a positive polarity voltage equal to or higher than the voltage applied to the core of the collection roller 23 is applied to the conductive collection blade 24. The brush facing roller 28 has a resistance layer having a volume resistance value equal to or greater than the volume resistance value of the image carrier on the surface thereof. If the volume resistance value is close to insulation, the counter roller cannot play the role of an electrode, so an extremely high resistance value must be avoided. It is necessary to set the resistance value so that the cleaning electric field can be maintained and the conductive brush current is low, and the volume resistance value is preferably logR = 6-8.

  FIG. 13 is an embodiment in which the opposing roller of the polarity control blade 21 also serves as the opposing roller of the conductive brush 22. If the resistance values required for the surface layers of both opposed rollers are almost the same, the functions can be demonstrated without any problems even if the opposed rollers are used in common, and the number of parts is reduced to save space. Can also contribute.

Specific configuration conditions of the conductive brush 22 and the collection roller 23 are as follows. The conductive brush 22 is made of brush material: conductive polyester (a so-called core-sheath structure in which conductive carbon is embedded inside the fiber and the fiber surface is polyester), brush resistance: 10 ⁷ Ω (applied voltage: 100 to 600 V), brush Axial applied voltage: 1000 V, brush flocking density: 100,000 / inch ² , fiber diameter of about 25 to 35 μm, brush tip fall-over treatment, brush diameter φ16 mm, but not limited thereto.

FIG. 14 shows the cleaning performance when the brush resistance R is logR = 5, 7, and 9. Since the applied voltage is large at log R = 9, the power supply cost increases. When logR = 5, current easily flows through the intermediate transfer belt 11. Therefore, the toner is charged with a positive polarity at a lower voltage than when logR = 7 and is reattached to the intermediate transfer belt 11. Therefore, the condition of logR = 7 is most suitable. Therefore, by setting the resistance value of the conductive brush 22 to 10 ⁶ to 10 ⁸ Ω, it becomes difficult for the toner to reattach to the intermediate transfer belt 11 from the conductive brush 22, and the intermediate transfer belt 11 can be cleaned well. It can be carried out.

  The amount of brush fiber biting into the intermediate transfer belt 11 is 1 mm. The brush fiber is conductive as a whole, but the fiber surface is covered with an insulating layer. By having an insulating layer on the fiber surface, it is difficult for current to flow when the brush and the intermediate transfer belt 11 contact each other, and it is difficult for excessive current to flow when the brush fiber electrostatically attracts toner from the intermediate transfer belt 11. Therefore, the toner of the opposite polarity is not given to the toner, and the possibility that the toner once captured by the brush adheres on the intermediate transfer belt 11 is reduced. However, even if such a brush is used, if a voltage sufficient to destroy the insulating layer on the fiber surface and flow current is applied to the brush shaft, the toner is returned to the intermediate transfer belt 11 as a result. Care must be taken when setting the voltage value. In addition, if the brush is formed in a roll shape and then subjected to slanting treatment that tilts the hair in one direction, the conductive agent exposed on the fiber cross section becomes difficult to come into contact with the intermediate transfer belt 11, so that charge injection into the toner is further performed. And the margin of cleaning performance is improved.

The collection roller 23 is made of a collection roller core material: stainless steel, a collection roller surface material: PVDF (thickness: 100 μm), an acrylic UV curable resin layer (thickness: 3-5 μm), and a brush fiber biting amount into the collection roller: 1 mm. Recovery roller mandrel applied voltage: +1400 V, conductive recovery blade 24 has conductive carbon-containing polyurethane rubber volume resistance: 10 ⁶ Ω · cm (measured at a temperature of 25 ° C. and a humidity of 50%), blade contact angle: 20 °, blade thickness: 2.8 mm, amount of blade biting into the collection roller: 0.6 mm, voltage applied to the collection blade: 2400 V, however, the brush resistance is 1 mm of conductive brush 22 biting into a 10 mm diameter stainless steel roller , Rotate them at 200 mm / sec, apply a voltage to the brush core, measure the current, and calculate the resistance. One in which the.

  As the collection roller 23, a stainless steel core (diameter 16 mm) having PVDF with a thickness of 100 μm and a surface having an acrylic UV curable resin layer (hereinafter referred to as a high resistance roller) was used. . The roller resistance is calculated by applying a voltage of 1000 V under a temperature of 10 ° C. and a humidity of 15% and a temperature of 32 ° C. and a humidity of 80%, respectively, and the volume resistance value is logR = 12-13. The same applies not only to the roller used in this embodiment, but also to a conductive core metal covered with a high resistance elastic tube of several μm to 100 μm, or further insulatively coated to make the roller resistance logR = 12-13. Get performance. Further, the conductive recovery blade 24 for cleaning the recovery roller 23 is formed of conductive polyurethane rubber, and voltages having the same polarity are applied to the conductive brush 22, the recovery roller 23, and the conductive recovery blade 24, respectively.

  Next, the conductive recovery blade 24 will be described. A voltage is applied to the core of the collecting roller 23 and the surface potential is measured to be the same as the applied voltage. However, when a large amount of toner is processed during the cleaning operation, the surface potential of the collecting roller 23 is Decreases with toner processing. When the surface potential of the collection roller 23 decreases, a potential difference from the brush tip potential (hereinafter referred to as a collection potential difference) cannot be ensured, and the ability to collect toner from the conductive brush 22 decreases. For this reason, the recovery potential difference can be secured if the image forming operation is for one A4 size sheet, but if the processing toner of the conductive brush 22 is increased due to the continuous printing operation, the recovery potential difference cannot be secured and the conductivity is increased. There is a problem that toner is discharged from the conductive brush 22 onto the intermediate transfer belt 11 in a state where toner is accumulated in the brush 22. For this reason, the collection performance is maintained by applying a voltage to the collection blade as a conductive collection blade and applying a charge to the surface of the collection roller 23 to maintain the collection potential difference.

  Such a voltage application to the polarity control blade 21 for maintaining the recovery potential difference is not so necessary when the polarity control blade 21 is a new one because there is little toner that slips through. However, when the polarity control blade is used for a long time, the amount of toner passing through increases, or the toner passing through from the polarity control blade 21 increases in a low temperature and low humidity environment than in a high temperature and high humidity environment. is there. Although various cleaning conditions have been described above, the materials and voltage values to be used are not limited to these, and should be appropriately selected.

  By the way, in order to achieve high image quality in the image forming apparatus and the reproduction of the same color by repeating the same image, control for adjusting the image forming process conditions as necessary in order to keep the image density constant. Has been done in the past.

  For example, the developer must be triboelectrically charged by mixing toner and carrier and the toner charge amount must be constant, but the toner charge amount is attenuated after several hours from the previous image forming operation. If an image is formed immediately without performing the stirring operation, there is a problem that the developing amount on the image carrier increases with a low toner charge amount. In addition, if continuous image formation is performed, the toner density in the developing device decreases, so it is necessary to supply toner to the developing device. However, in order to supply toner without excess or deficiency, a developer (mixed toner and carrier) is required. There is a method of replenishing toner by detecting the toner concentration in the toner) with a sensor or the like that detects the magnetic permeability of the developer. In addition, in order to improve detection accuracy, a toner pattern having a size of several centimeters × several centimeters for each color is created on the transfer belt while changing the charging bias and developing bias, and then the image density is read by a photo sensor. Thus, the relationship between the image density and the development potential (the difference between the development bias and the photoreceptor surface potential) is obtained, and the image is always set to the target density based on the image density and development potential data table stored in the control unit. Control for determining and correcting the charging bias and the developing bias is also performed. In the present embodiment, ten toner patterns having an area of 2 cm × 2 cm each having a different image density are formed on each color intermediate transfer belt and read by a photo sensor.

The toner adhesion amount minimum 0.1 mg / cm ² at this time, a maximum of 0.55 mg / cm ² or so, when measuring the toner Q / d distribution are aligned substantially normal charging polarity (FIG. 8 (c) reference). Further, color misregistration adjustment may be performed in order to superimpose toner images of respective colors without misalignment. A color misregistration correction pattern similar to the toner pattern described above is created on the intermediate transfer belt, and is read by a sensor to measure the image position and control to correct the writing position is also performed. At this time, a solid pattern with a high image density is created on the intermediate transfer belt so that the sensor does not detect it erroneously.

At this time, the toner adhesion amount is determined as yellow, magenta, cyan, black, yellow, magenta, cyan, and black in a predetermined color order in the intermediate transfer belt running direction with a constant image density and a constant size toner pattern. The position of each color pattern is read by a photo sensor arranged in a non-contact state opposite to the intermediate transfer belt, and the amount of deviation is calculated to shift the timing of writing the deviation from the correct position on the photoconductor. It is corrected by. At this time, the toner adhesion amount is about 0.3 mg / cm ² .

  As described above, a toner image that is not transferred onto the transfer sheet is created on the intermediate transfer belt 11 at various timings, and the toner pattern must be collected by the intermediate transfer belt cleaning device 20. However, in the conventional blade cleaning device, it may be difficult to remove the residual toner on the intermediate transfer belt 11 at a time when the blade tip deteriorates due to long-term use. In such a case, the residual toner on the intermediate transfer belt 11 that could not be cleaned is transferred onto the transfer paper during the next printing operation, resulting in an abnormal image.

  Therefore, as described above, the polarity control blade 21 and the electrostatic cleaning device are combined when there is toner to be processed by the intermediate transfer belt cleaning device 20 without being transferred to a transfer material such as transfer paper. Therefore, the amount of toner carried to the conductive brush 22 can be reduced, and the non-transferred toner has the same polarity as the regular charging polarity and is unipolar with or without polarity control. By applying a voltage having a polarity opposite to the charging polarity to the conductive brush 22, the recovery roller 23, and the conductive recovery blade 24, the cleaning can be performed satisfactorily.

  In addition, even if the polarity control blade 21 deteriorates due to long-term use and the amount of toner passing through the polarity control blade 21 increases, the polarity of the toner carried to the conductive brush 22 remains the normal polarity. The conductive brush 22 can perform sufficient cleaning. Further, since a voltage is applied to the conductive recovery blade 24, the function of maintaining the surface potential of the recovery roller 23 works even if a lot of toner is carried to the conductive brush 22, and the recovery performance does not deteriorate, so that it can be maintained for a long time. The surface of the intermediate transfer belt 11 can be maintained normally, which can contribute to a long life. Here, there is not much problem in using the conductive brush 22 for a long period of time, and the brush fibers used in the present embodiment are less likely to fall down even when used for a long period of time. There was no problem that the amount of biting into the belt 11 was reduced and the cleaning was poor.

  Next, a second embodiment of the intermediate transfer belt cleaning device 20 according to the present invention will be described with reference to FIG. The embodiment shown in FIG. 12 is different from the embodiment shown in FIG. 3 in that the lubricant 32 is brought into contact with the conductive brush 22 and the lubricant 32 is applied to the intermediate transfer belt 11 via the conductive brush 22. In FIG. 12, the same members as those in FIG. 3 are denoted by the same reference numerals.

  In this embodiment, since the surface of the intermediate transfer belt 11 is constantly rubbed by the polarity control blade 21, a lubricant 32 is applied to protect the surface of the intermediate transfer belt 11 and reduce the wear amount of the polarity control blade 21. ing. In this configuration, the solidified lubricant 32 is disposed at a position where it comes into contact with the conductive brush 22 after contact with the collection roller 23, and the lubricant is applied via the conductive brush 22. The lubricant 32 is pressed against the conductive brush 22 by the urging force of a spring 33 provided on a support member 34 fixed to the casing of the intermediate transfer belt cleaning device 20, and the lubricant 32 becomes smaller with time. However, it is configured so as to come into contact with the conductive brush 22 appropriately by the urging force of the spring 33. As the lubricant 32, a fatty acid metal salt is suitable, and among them, zinc stearate, calcium stearate, iron stearate, copper stearate, magnesium palmitate, calcium palmitate, manganese oleate, lead oleate and the like are suitable. By applying the lubricant 32 to the intermediate transfer belt 11, the surface of the intermediate transfer belt 11 is protected and the wear of the polarity control blade 21 is reduced, so that a good image forming operation can be performed over a long period of time.

In order to prevent the toner floating in the intermediate transfer belt cleaning device 20 from coming out of the cleaning device, the gap between the intermediate transfer belt 11 and the intermediate transfer belt 11 is shielded by using the outlet seal 35 shown in FIG. It has been found that the toner adhering to the brush strikes the lubricant 32 as the conductive brush 22 rotates, and adheres to the intermediate transfer belt 11 in the region A in FIG. In view of this, a shielding member 36 shown in FIG. The shielding member 36 is disposed such that a urethane rubber sheet having a thickness of 200 μm is attached to the casing of the cleaning device and the amount of biting into the conductive brush 22 is 1 mm. The pasting allowance with the casing is 3 mm, and the protruding amount is 7 mm. The material of the shielding member 36 is not limited to urethane rubber, and may be any material having insulation and flexibility. The thickness is not limited to 200 μm as long as it is not caught by the rotation of the brush and is not splashed by the air flow caused by the rotation of the brush. Thereby, the scattered toner from the conductive brush 22 can be prevented from adhering to the photoreceptor 2 via the intermediate transfer belt 11, and toner contamination of the photoreceptor 2 after cleaning can be prevented.
The toner transfer control of the intermediate transfer belt cleaning device 20 shown in FIGS. 12 and 15 is the same as that of the intermediate transfer belt cleaning device 20 shown in FIG. 3, but the voltage applied to the polarity control blade 21 is, for example, controlled by constant current control. 80 μA.

  FIG. 16A shows the case where the polarity of the transfer residual toner A in which the positive polarity and the negative polarity are 50% each is controlled by the polarity control blade 21, and FIG. When the polarity is controlled by the blade 21, FIG. 16C is a Q / d distribution change diagram when the polarity control blade 21 controls the polarity of mostly untransferred toner having a negative polarity.

  The transfer residual toner on the intermediate transfer belt 11 becomes a toner having a distribution in which positive polarity and negative polarity are mixed as shown as transfer residual toner A in FIG. 16A and transfer residual toner B in FIG. The intermediate transfer belt 11 is transported to a position corresponding to the polarity control blade 21 by traveling. Although most of the toner is mechanically scraped off by the polarity control blade 21, so-called stick-slip occurs and a part of it slips through. The toner that has been mechanically scraped off falls naturally from the blade, is accommodated in the collection unit, is conveyed by the coil member 25, and is collected in the waste toner collection unit.

  A voltage having the same polarity (minus polarity) as the charging polarity of the toner is applied to the polarity control blade 21, and when the toner passes through the polarity control blade 21, the toner is charged to a normal charging polarity (minus polarity). FIGS. 16A and 16B show the controlled toner Q / d distributions when the applied voltage is −2000 V, respectively. The Q / d distribution after the polarity control differs depending on the Q / d distribution of the transfer residual toner as the input toner (difference between the transfer residual toner A and the transfer residual toner B), but both can be controlled to be almost unipolar. .

  FIG. 17 is a diagram showing a detailed configuration of a unit around the photoconductor 2, which is one of the image forming portions for four colors shown in FIG. 2, and the photoconductor cleaning device 7d will be described below. . Since the other photoconductor cleaning devices 7a to 7c are the same, the following explanation will be made with the subscript d omitted.

  The photoconductor cleaning device 7 has a polarity control blade 71 for controlling the polarity of the untransferred toner on the photoconductor 2 in a mode of contacting the surface of the photoconductor 2, and a subsequent process of the polarity control blade 71. Includes a conductive brush 72 for cleaning the polarity-controlled toner, a recovery roller 73 for recovering the toner adhering to the conductive brush 72 from the brush, and scraping the recovered toner in contact with the surface of the recovery roller 73. At the same time, a conductive recovery blade 74 for applying a charge to the surface of the recovery roller 73 and a coil member 75 for transporting the recovered toner to a waste toner tank (not shown) provided in the image forming apparatus main body are provided. Further, in order to protect the surface of the photoreceptor 2 in the charging process, the solidified lubricant 76 is brought into contact with the conductive brush 72 and the lubricant 76 is applied to the surface of the photoreceptor 2 by the conductive brush 72. It is configured. The lubricant 76 is pressed against the conductive brush 72 by an urging force of a spring 77 provided on a support member 78 fixed to the casing, and the urging force of the spring 77 even if the lubricant 76 becomes smaller with time. Therefore, the conductive brush 72 is appropriately contacted.

  The shielding member 79 is disposed such that a urethane rubber sheet having a thickness of 200 μm is attached to the casing of the cleaning device 7 so that the amount of biting into the conductive brush 72 is 1 mm. The pasting allowance with the casing is 3 mm, and the protruding amount is 7 mm. The material of the shielding member 79 is not limited to urethane rubber, and any material having insulating properties and flexibility may be used. The thickness is not limited to 200 μm as long as it does not get caught by the rotation of the brush and is not splashed by the air flow caused by the rotation of the brush.

  A color printer employing the third embodiment of the present invention is shown in FIG. In the figure, a color printer includes a photosensitive drum 101 as an image carrier, a writing optical unit 107, a black developing device 102a, a cyan developing device 102b, a magenta developing device 102c, a yellow developing device 102d, an intermediate transfer device 110, and a paper transfer device. 103, a fixing device (not shown) and the like.

  The photosensitive drum 101 rotates counterclockwise. Around the photosensitive drum 101, a photosensitive member cleaning device 104, a static elimination lamp 105, a charger 106, and developing devices 102a to 102d are arranged. A writing optical unit 107 is connected to a color scanner. The color image data is converted into an optical signal, and optical writing corresponding to the image of the original is performed to form an electrostatic latent image on the surface of the photosensitive drum 101.

  The developing devices 102a to 102d include a developing sleeve that rotates by bringing the ears of the developer into contact with the surface of the photosensitive drum 101 in order to develop the electrostatic latent image, and a developer that rotates to pump up and stir the developer. Has paddles, etc. The toner in each developing device is negatively charged in this embodiment by stirring with a ferrite carrier, and each developing sleeve is supplied with a negative DC voltage Vdc by a developing bias power source as a developing bias applying means (not shown). A developing bias on which Vac is superimposed or a developing bias of only a DC voltage is applied, and the developing sleeve is biased to a predetermined potential with respect to the metal substrate layer of the photosensitive drum 101.

  A toner image of each color is sequentially formed on the photosensitive drum 101, and the formation order can be selected as appropriate. The intermediate transfer device 110 includes an intermediate transfer belt 111, a belt cleaning device 113, and the like. The intermediate transfer belt 111 is stretched around a driving roller 112, a bias roller 115, a cleaning facing roller 116, a driven roller 114, and other driven roller groups, and is driven and controlled by a driving motor (not shown).

  By applying a voltage to the bias roller 115, the toner image formed on the photosensitive drum 101 is primarily transferred onto the intermediate transfer belt 111. The primary transfer bias voltage is applied by appropriately adjusting between 1000V and 2000V from the first color to the fourth color.

The secondary transfer bias voltage is 30 μA, the photoreceptor potential is −80 to −130 V in the image area, −500 to −700 V in the background area, the toner density is 5 to 10 wt% for each color, and the toner charge amount (in the developing device) is each color − 10 to -25 μC / g, transfer roller is a hydrin rubber roller coated with a PFE tube, volume resistivity is 10 ⁹ Ω · cm, intermediate transfer belt is carbon-dispersed fluororesin ETFE (ethylene tetrafluoroethylene), intermediate The electric resistance of the transfer belt is 10 ¹⁰ Ω · cm in terms of volume resistivity and 10 ⁹ Ω in terms of surface resistivity, and the intermediate transfer belt cleaning device 20 shown in FIG. Use.

  An AC voltage + DC voltage or a DC voltage is applied to the paper transfer device 103 to collectively transfer the superimposed toner images on the intermediate transfer belt 111 onto the recording paper. When an image forming cycle is started in the color copying machine having the above-described configuration, the photosensitive drum 101 is rotated counterclockwise and the intermediate transfer belt 111 is rotated clockwise by a driving motor (not shown). As the intermediate transfer belt 111 rotates, black toner image formation, cyan toner image formation, magenta toner image formation, and yellow toner image formation are performed. Finally, black, cyan, magenta, and yellow are overlaid on the intermediate transfer belt 111 in this order. Thus, a toner image is formed.

  Black toner image formation is performed as follows. The charger 106 uniformly charges the photosensitive drum 101 to about −700 V with negative charge by proximity roller charging. The semiconductor laser from the writing optical unit 107 performs raster exposure based on the black color image signal. When this raster image is exposed, on the surface of the photosensitive drum 101 that is initially charged uniformly, the electric charge proportional to the amount of exposure light disappears in the exposed portion, and a black electrostatic latent image is formed. When the black electrostatic latent image on the black developing sleeve comes into contact with the black electrostatic latent image, the toner does not adhere to the portion where the charge of the photosensitive drum 101 remains, that is, the portion without charge, that is, Black toner is attracted to the exposed portion, and a black toner image similar to the electrostatic latent image is formed. The black toner image formed on the photosensitive drum 101 is applied to the surface of the intermediate transfer belt 111 that is driven at a constant speed in contact with the photosensitive drum 101 by the operation of the intermediate transfer device 110 as follows. The toner image is transferred from the photosensitive drum 101 to the intermediate transfer belt 111 (hereinafter referred to as belt transfer).

  The bias roller 115 is applied with a bias voltage having a polarity opposite to that of the toner on the photosensitive member 101 from a power source (not shown), and in this embodiment, a positive polarity bias voltage is applied, and the intermediate transfer belt portion wound around the bias roller 115 is the photosensitive member 101. In contact with the surface, in this state, the intermediate transfer belt 111 travels in the direction indicated by the arrow in FIG. 18 by the rotation of the driving roller 112 driven by a motor (not shown). The photosensitive member 101 and the intermediate transfer belt 111 are controlled to move in the same direction at the contact portion between them and to move at a constant speed. Since a voltage having a polarity opposite to that of the toner is applied to the bias roller 115, when the black toner image on the photoconductor 101 reaches the primary transfer region which is a contact portion between the photoconductor 101 and the intermediate transfer belt 111, The black toner image is electrostatically attracted to the surface of the intermediate transfer belt 111 and is primarily transferred to the surface of the intermediate transfer belt 111.

  Some untransferred residual toner on the photoconductor drum 101 is cleaned by the photoconductor cleaning device 104 in preparation for reuse of the photoconductor drum 101. The toner collected here is stored in a waste toner tank (not shown) via a collection pipe. When the cleaning device 7 shown in FIG. 17 is used as the photoconductor cleaning device 104, good cleaning properties can be obtained. The surface of the photosensitive drum 101 after the belt transfer is cleaned by the photosensitive member cleaning device 104 and then uniformly discharged by the discharging lamp 105.

  On the intermediate transfer belt 111, toner images of four colors are formed by sequentially aligning black, cyan, magenta, and yellow toner images sequentially formed on the photosensitive drum 101 on the same surface, and in the next transfer step. The four color toner images are collectively transferred to the recording paper by the paper transfer device 103. If the intermediate transfer belt cleaning device 20 shown in FIGS. 3 and 15 is used as the cleaning device for the intermediate transfer belt 111 shown in this embodiment, good cleaning properties can be obtained. In addition, by using an intermediate transfer belt 111 having an elastic layer with a thickness of 0.07 to 0.3 mm, it is possible to transfer the toner satisfactorily even to a transfer material having irregularities on the surface, and high quality. Images can be obtained.

  The intermediate transfer belt 11 used in the image forming apparatus shown in this embodiment has at least a base layer 51, an elastic layer 52, and a surface coat layer 53 as shown in FIG. By having this, the transfer nip portion can be deformed with respect to the toner layer and the paper having low smoothness. According to this configuration, since the intermediate transfer belt 11 can be deformed following local unevenness, good adhesion can be obtained without excessively increasing the transfer pressure with respect to the toner layer. It is possible to obtain a transfer image excellent in uniformity with no transfer unevenness in a solid portion or the like even on a sheet having no transfer omission and low smoothness.

  Examples of the material used for the elastic layer 52 include elastic members such as elastic material rubber and elastomer, and specifically include butyl rubber, fluorine-based rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene rubber, and natural rubber. , Isoprene rubber, styrene-butadiene rubber, butadiene rubber, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, polysulfide rubber, polynorbornene rubber, thermoplastic elastomer (for example, polystyrene, polyolefin, One kind or two or more kinds selected from the group consisting of polyvinyl chloride, polyurethane, polyamide, polyurea, polyester, and fluororesin) can be used. However, it is not limited to the above materials.

  The thickness of the elastic layer 52 is preferably 0.07 to 0.5 mm, although it depends on the hardness and the layer configuration. When the intermediate transfer belt cleaning device is of a blade type, if it has a thickness of 0.3 mm or more, the intermediate transfer belt may be bent due to the pressing force of the cleaning blade or the cleaning blade may be pushed into the intermediate transfer belt 11. However, in the present invention, the smaller the contact area between the polarity control blade 21 and the intermediate transfer belt 11, the more stable discharge is performed, so the contact pressure of the polarity control blade 21 can be reduced. Even if the thickness of the elastic layer 52 exceeds 0.3 mm, the smooth movement of the intermediate transfer belt 11 is not hindered. Therefore, the function of reducing the residual toner amount input to the conductive brush 22 by the polarity control blade 21 and the function of controlling the Q / M value of the residual toner can be compatible.

  When the thickness of the intermediate transfer belt 11 is 0.07 mm or less, the pressure on the toner on the intermediate transfer belt 11 at the secondary transfer nip portion is increased, and transfer loss is likely to occur, and the toner transfer rate is further reduced. . The hardness of the elastic layer 52 is preferably 10 ≦ HS ≦ 65 (JIS-A). Although the optimum hardness varies depending on the layer thickness of the intermediate transfer belt 11, if the hardness is lower than 10 ° JIS-A, transfer deficiency tends to occur. On the other hand, when the hardness is higher than 65 ° JIS-A, it is difficult to stretch the roller, and since it is stretched by long-term stretching, the durability is low and early replacement is necessary.

  The base layer 51 is composed of a resin with little elongation. Specifically, the material used for the base layer 51 is polycarbonate, fluororesin (ETFE, PVDF, etc.), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene- Butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-acrylic) Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer) Polymer, styrene-ethyl methacrylate copolymer, Styrene-phenyl methacrylate copolymers, etc.), styrene resins such as styrene-α-methyl acrylate acrylate copolymers, styrene-acrylonitrile-acrylate ester copolymers (monopolymers containing styrene or styrene-substituted products, or Copolymer), methyl methacrylate resin, butyl methacrylate resin, ethyl acrylate resin, butyl acrylate resin, modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride Resin, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, Use one or more selected from the group consisting of ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin, polyamide resin, modified polyphenylene oxide resin, etc. be able to. However, it is not limited to the above materials.

  For example, a method may be employed in which a core layer made of a material that prevents elongation, such as canvas, is provided on the base layer 51 and a resilient layer 52 is formed thereon. Examples of materials for preventing elongation used in the core layer include natural fibers such as cotton and silk, polyester fibers, nylon fibers, acrylic fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, and polyvinylidene chloride fibers. , One or more selected from the group consisting of synthetic fibers such as polyurethane fiber, polyacetal fiber, polyfluoroethylene fiber and phenol fiber, inorganic fibers such as carbon fiber and glass fiber, and metal fibers such as iron fiber and copper fiber Threaded or woven fabric can be used. However, it is not limited to the above materials. These yarns may be twisted in any manner, such as one or a plurality of filaments twisted, a single twisted yarn, various twisted yarns, a double yarn or the like. Further, fibers of a material selected from the above material group may be blended, and the yarn may be used after being subjected to an appropriate conductive treatment. As the woven fabric, any woven fabric such as knitted fabric can be used, and a cross-woven fabric can be used and can be subjected to conductive treatment.

  The coat layer 53 is for coating the surface of the elastic layer 52 with, for example, a fluororesin, and is made of a layer having good smoothness. The material used for the coating layer 53 is not particularly limited, but generally, a material that reduces the toner adhesion to the surface of the intermediate transfer belt 11 and increases the secondary transferability is used. For example, polyurethane, polyester, epoxy resin One type or two or more types. In addition, a material for reducing the surface energy and improving the lubricity, for example, fluororesin, fluorine compound, carbon fluoride, titanium oxide, silicon carbide, etc., one or more kinds of particles, or the particle size is changed as necessary. It is also possible to use a dispersed product. Further, a material such as a fluorine-based rubber material in which a heat treatment is performed to form a fluorine layer on the surface to reduce the surface energy may be used.

  The base layer 51, the elastic layer 52, and the coat layer 53 are, for example, carbon black, graphite, metal powder such as aluminum or nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, titanium for the purpose of adjusting resistance as necessary. Conductive metal oxides such as potassium acid, antimony oxide-tin oxide composite oxide (ATO), and indium oxide-tin oxide composite oxide (ITO) can be used. The conductive metal oxide may be coated with insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate. However, it is not limited to the above materials.

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

The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. FIG. 19 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π) / 4 Formula (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

FIG. 20 is a diagram schematically showing the shape of the toner for explaining the shape factor SF-2. The shape factor SF-2 indicates the ratio of unevenness in the shape of the toner, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × 100 / (4π) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent. Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco), and analyzing and calculating the shape factor. did. When the shape of the toner is close to a sphere, the contact state between the toner and the toner or the toner and the photoconductor becomes point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The adsorbing power of the ink becomes weak and the transfer rate increases. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  In addition, a toner suitably used for a color printer includes a toner material solution in which a polyester prepolymer having a functional group containing at least a nitrogen atom, a polyester, a colorant, and a release agent are dispersed in an organic solvent. It is a toner obtained by crosslinking and / or elongation reaction therein. 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) is 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 Lumpur acids (ethylene oxide, propylene oxide, butylene oxide, etc.) adducts. Among these, 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 a mixture of (DIC) and a small amount of (TC) Is 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) , Naphthalenedicarboxylic acid, etc.). 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 polyvalent carboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polycarboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the acid anhydride or lower alkyl ester (methyl ester, ethyl ester, isopropyl ester, etc.) of the above-mentioned thing.

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

  In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting the terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines. Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-isocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; phenol derivatives, oximes, caprolactam And a combination of two or more of these. The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably 4 as the equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. / 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 polyisocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance 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 isocyanate groups is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2.5 on average. It is. When the number is less than 1 per molecule, the molecular weight of the urea-modified polyester is lowered and the hot offset resistance is deteriorated.

  Next, as the 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 B1 to B5 amino group blocked (B6) include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

  The ratio of the amines (B) is the equivalent ratio [NCO] / [NHx] of the isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and the amino groups [NHx] in the 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 less than 2 or 1/2, the molecular weight of the urea-modified polyester becomes low and the hot offset resistance deteriorates.

  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, more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated.

  The urea-modified polyester is produced by a one-shot method or the like. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150 to 280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc. 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 as 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 device are deteriorated.

  By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the glossiness when used in a full-color image forming apparatus are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond. The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.

  The weight ratio of unmodified polyester to urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If the temperature is lower than 45 ° C., the heat resistance of the toner is deteriorated. Since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

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

  The colorant can also be used as a master batch combined with a resin. As the 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, polyvinyltoluene, or a substituted product thereof, 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 resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be mentioned, and these can be used alone or in combination.

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

  The amount of charge control agent used is determined by the toner production method including the type of binder resin, the presence or absence of additives used as necessary, and the dispersion method, but 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 force with the developing roller is increased, and the flowability of the developer and the image density are reduced. 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, or 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 ~2μm, it is particularly preferably 5 × ¹⁰ -3 ~0.5μm. Moreover, it is preferable that the specific surface area by BET method is 20-500 m < ² > / g. The use ratio of the inorganic fine particles is preferably 0.01 to 5 wt% of the toner, and particularly preferably 0.01 to 2.0 wt%. Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Among these, as the fluidity-imparting agent, it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using particles having an average particle diameter of 5 × 10 ⁻⁴ μm or less, the electrostatic force and van der Waals force with the toner are remarkably improved. Even when stirring and mixing inside the developing device is performed in order to obtain a toner, a fluidity-imparting agent is not detached from the toner, a good image quality that does not cause firefly and the like is obtained, and a residual toner is further reduced. . 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, the copying can be repeated. Stable image quality can be obtained even if it is performed.

  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, an 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 preferred. The amount of the organic solvent used is usually 0 to 300 parts by weight, preferably 0 to 100 parts by weight, and more preferably 25 to 70 parts by weight with respect to 100 parts by weight of the polyester prepolymer.

  (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 contains an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be a thing. 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 .

  By using a surfactant having a fluoroalkyl group, the effect can be increased 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).

  Cationic surfactants include aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, aliphatic quaternary ammonium salts such as perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, benza Luconium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (Asahi Glass), Florard FC-135 (Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Megafac F-150, F-824 (manufactured by Dainippon Ink, Inc.), Xtop EF-132 (manufactured by Tochem Products), and Footgent F-300 (manufactured by Neos).

  The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage which exists on the surface of a toner base particle may be 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), SGP (manufactured by Soken Co., Ltd.), Technopolymer There are SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), Micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.) and the like. In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.

  As a dispersant that can be used in combination with the resin fine particles and the inorganic compound dispersant described above, 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, etc., 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 chloride, methacrylic chloride, vinyl pyridine, vinyl pyrrolidone, vinyl Homopolymers or copolymers such as nitrogen-containing compounds such as imidazole and ethyleneimine or those having a heterocyclic ring thereof, polyoxyethylene, polyoxypropylene , Polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxyethylene nonyl Polyoxyethylenes such as phenyl esters, 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 type, a high-speed shear type, a friction type, a high-pressure jet type, 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. The number of rotations when using a high-speed shearing disperser 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) The amine (B) is added simultaneously with the preparation of the emulsion, and the reaction with the polyester prepolymer (A) having an isocyanate group is performed. 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. . In addition, when an acid or alkali-soluble material such as calcium phosphate salt is used as the dispersion stabilizer, the calcium phosphate salt is removed from the toner base particles by, for example, washing with water after dissolving the calcium phosphate salt with an acid such as hydrochloric acid. To do. It can also be removed by an operation such as degradation with an enzyme.

  (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 sphere and the rugby ball shape can be controlled, and the surface morphology is also controlled between the smooth one and the umeboshi shape. Can do.

  The toner has a substantially spherical shape and can be represented by the following shape rule. 21A, 21B, and 21C are diagrams schematically showing the shape of the toner. In FIGS. 21A, 21B, and 21C, when a substantially spherical toner is defined by a major axis r1, a minor axis r2, and a thickness r3 (where r1 ≧ r2 ≧ r3), the main toner is defined. The toner usable in the invention has a ratio of the major axis to the minor axis (r2 / r1) (see FIG. 21B) of 0.5 to 1.0, and a ratio of the thickness to the minor axis (r3 / r2). (See FIG. 21C) is preferably in the range of 0.7 to 1.0. If the ratio of the major axis to the minor axis (r2 / r1) is less than 0.5, the distance from the true sphere shape is inferior, resulting in poor dot reproducibility and transfer efficiency, and high quality image quality cannot be obtained. Further, when the ratio of thickness to short axis (r3 / r2) is less than 0.7, it becomes close to a flat shape, and a high transfer rate like a spherical toner cannot be obtained. In particular, when the ratio of the thickness to the short axis (r3 / r2) is 1.0, the rotating body has the long axis as the rotation axis, and the fluidity of the toner can be improved. In addition, r1, r2, and r3 were measured while taking and observing photographs with a scanning electron microscope (SEM) while changing the angle of view.

  In the above-described configuration, an example in which a color printer is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited to this, and other apparatuses such as a copying machine, a facsimile, a plotter, and a multi-function machine thereof can be used. The present invention can also be applied to an image forming apparatus.

2,101 Image carrier (photoconductor)
6 Primary transfer means (primary transfer roller)
8 Secondary transfer means (secondary transfer roller)
11.111 Image carrier (intermediate transfer belt)
16 Opposing member (counter roller)
20 Cleaning device (intermediate transfer belt cleaning device)
21, 71 Conductive member (polarity control blade)
22, 72 Cleaning member (conductive brush)
23, 73 Recovery roller 24, 74 Recovery roller cleaner (conductive recovery blade)
26 Resistance layer 32, 76 Lubricant 36, 79 Shield member 104 Cleaning device (photoconductor cleaning device)

Japanese Patent No. 39002823

Claims (13)

A conductive member that controls the charging polarity of toner to be removed from the image bearing member by contacting the surface of the image bearing member, a cleaning member that electrostatically cleans the toner whose charging polarity is controlled, and the conductive member And a grounded counter member provided in contact with the back side of the image carrier at a position facing the photosensitive member, and the image carrier has a volume resistivity of 1 × 10 ⁹ to 1 × 10 ¹⁴ Ωcm. And the opposing member is covered with a conductive resin or conductive rubber having a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹² Ωcm, and the conductive member is grounded via the image carrier and the opposing member. A cleaning device characterized in that it is configured. The cleaning device according to claim 1.
A cleaning apparatus having a polarity control member made of conductive rubber as the conductive member. The cleaning device according to claim 2, wherein
The cleaning apparatus according to claim 1, wherein the polarity control member is a blade. A conductive member that controls the charging polarity of toner to be removed from the image bearing member by contacting the surface of the image bearing member, a cleaning member that electrostatically cleans the toner whose charging polarity is controlled, and the conductive member and a counter member which are provided ground contact sexual member and the rear surface side of the image bearing member at a position opposed to the cleaning member, said image bearing member is a volume resistivity of ¹ × 10 9 ~1 × 10 ¹⁴ a [Omega] cm, and the opposing member is a volume resistivity is covered by ^{1 × 10 8 ~1 × 10 12} Ωcm conductive resin or conductive rubber, the conductive via the image carrier and the counter member A cleaning device characterized in that the cleaning member and the cleaning member can be grounded. In the cleaning device according to any one of claims 1 to 4,
The cleaning member is a brush roller that can be rotated while being in contact with the surface of the image carrier, in which the conductive fibers are planted from the outer periphery of the conductive core metal so as to extend outward in the diameter direction. A collecting roller that is rotatable while being in contact with the fiber and has an electrical resistance layer or insulating layer on its outer peripheral surface; means for applying a voltage to the core; means for applying a voltage to the collecting roller; A collection roller cleaner that scrapes off the toner collected on the collection roller, and a charge applying mechanism that contacts the collection roller and applies a charge to the surface of the collection roller to maintain a constant surface potential of the collection roller; The brush roller has a resistance value of 10 ⁶ to 10 ⁸ Ω. The cleaning device according to claim 5, wherein
The cleaning device according to claim 1, wherein the fibers have a layer structure, and the layer structure has a conductive material that imparts conductivity to the fibers in a manner that does not expose the surface. The cleaning device according to claim 5 or 6,
A blocking member that brings a lubricant into contact with the brush roller, applies the lubricant to the image carrier via the brush roller, and prevents toner scattered from the brush roller from adhering to the image carrier. A cleaning device comprising: The cleaning device according to claim 1 or 4,
The cleaning apparatus, wherein the conductive resin or the conductive rubber is a tube. In the cleaning device according to any one of claims 1 to 8,
The cleaning apparatus according to claim 1, wherein the image carrier is a belt.   An image forming apparatus comprising the cleaning device according to claim 1. The image forming apparatus according to claim 10.
A photoconductor as the image carrier, a toner image forming unit for forming a toner image on the photoconductor, and a toner image formed on the photoconductor are primarily transferred to an intermediate transfer body as an image carrier. Primary transfer means and secondary transfer means for secondary transfer of the toner image primarily transferred onto the intermediate transfer member onto a recording material, and the cleaning device performs cleaning of the intermediate transfer member. An image forming apparatus. The image forming apparatus according to claim 11.
The image forming apparatus, wherein the intermediate transfer member is a belt having an elastic layer having a thickness of 0.07 to 0.3 mm. The image forming apparatus according to any one of claims 10 to 12,
A toner having a volume average particle diameter of 3 to 8 μm and a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) in the range of 1.00 to 1.40 is used. An image forming apparatus.

Images