JP2010243529A - Endless belt and image forming apparatus provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an endless belt for efficiently removing deposits of the surface of an image carrier, without the accompaniment of toner consumption and suppress increase in the surface frictional resistance, and to provide an image forming apparatus provided with the belt. <P>SOLUTION: An intermediate transfer belt 5 is a three-layer conductive belt constituted of a base material layer 60, an elastic layer 61 and a coat layer 63. The coat layer 63 is in contact with a photoreceptor drum 1. Titanium oxide 65 is carried on the surface of the intermediate transfer belt 5; and when an electron beam is radiated at an acceleration voltage 10 kV with EPMA, element ratio of titanium on the surface of the intermediate transfer belt 5 obtained by a peak intensity ratio TiKα(4.51 eV) is 5-50 wt.%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an endless belt such as an intermediate transfer belt and a conveyance belt used in an image forming apparatus, and an image forming apparatus including the endless belt, and more particularly to polishing of a photoreceptor surface using the endless belt.

  In recent years, a photosensitive drum having an amorphous silicon (hereinafter also referred to as a-Si) photosensitive layer has been widely used as an image carrier of an image forming apparatus using an electrophotographic process. The a-Si photoconductor drum has high hardness and excellent durability, and its characteristics as a photoconductor are hardly deteriorated even after long-term use. In addition, the image carrier is excellent in environmental safety.

  In such an image forming apparatus using an a-Si photosensitive drum, when the photosensitive drum is charged using a charging device, ozone is generated by discharge from the charging device. The components in the air are decomposed by the ozone, and discharge products such as NOx and SOx are generated. Since this discharge product is water-soluble, it adheres to the photosensitive drum and enters into a roughness structure of about 0.1 μm on the surface of the photosensitive drum, so that it can be removed by a cleaning system used in a general-purpose machine. Can not. In a high humidity environment, the discharge product takes in moisture in the atmosphere and the resistance of the surface of the photoconductive drum is lowered. Therefore, the horizontal flow of the electric potential occurs at the edge portion of the electrostatic latent image formed on the surface of the photoconductive drum. Occurs, resulting in an image drift phenomenon.

  In addition, the adhesion of discharge products increases the frictional resistance on the surface of the photoconductor, lowering the transfer (primary transfer) efficiency from the photoconductor to the intermediate transfer body, image deterioration due to cleaning blade streaks, winding up of the edge of the cleaning blade, etc. The problem occurs. Furthermore, since the driving load of the photosensitive member increases, it causes a jitter.

  In view of this, a method for reducing the image flow by suppressing a decrease in resistance on the surface of the photosensitive drum with a simple configuration has been proposed. Patent Documents 1 and 2 disclose a toner (polishing toner) mixed with an abrasive and a polishing member. A method is disclosed in which the discharge product is removed without using a heater or the like by polishing the surface of the photoreceptor by the interaction of the (rubbing roller and cleaning blade).

  In the polishing system as described above, the surface of the photosensitive member is polished using the residual toner on the surface of the photosensitive member even during normal printing operation, but at the time of non-printing (when the apparatus is started up or in a standby mode after printing). A refresh mode is executed in which toner is printed or developed, and the toner is actively supplied to the polishing means in the photosensitive unit without being transferred to the recording medium and used for polishing the surface of the photosensitive member.

  However, even when the drum surface is rubbed with an abrasive member as in Patent Documents 1 and 2, depending on the charging conditions, the discharge product generation and adhesion rate becomes faster than the removal rate by the abrasive member, As a result, the friction coefficient of the drum surface increases, and filming of the toner external additive called a dash mark is likely to occur. In particular, in the case of a contact charging method including a charging member typified by a charging roller, the charging process on the surface of the photoconductor is performed by discharge near the surface, so that the discharge product tends to adhere to the surface of the photoconductor drum. Further, in order to realize a higher-speed image forming system, it is necessary to increase the charging bias applied to the charging member. However, as the charging bias is increased, the generation amount of discharge products increases.

  Further, once the generated dash mark cannot be removed by the rubbing roller, the edge portion of the cleaning blade is notched, and the external additive slipping through the edge portion adheres to the charging member. As a result, a problem that vertical stripes occur on the image occurs.

  Therefore, as a method for more effectively polishing the drum surface, Patent Document 3 discloses that a toner image formed on an image carrier during non-image formation is transferred onto a transfer member (transfer belt), and the transfer member and the image are transferred. There is provided an image forming apparatus in which an image carrier is polished using a transfer member carrying an abrasive-containing toner by providing a linear velocity difference between the carrier and the photosensitive drum (photosensitive drum) different from that at the time of image formation. It is disclosed.

Japanese Patent Laid-Open No. 11-3014 JP-A-11-133462 JP 2006-154475 A

  However, the method of Patent Document 3 has a problem in that the amount of toner consumed in other than the printing operation increases because the surface of the image carrier is polished using an abrasive-containing toner.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an endless belt that can efficiently remove deposits on the surface of an image carrier without toner consumption and suppress an increase in surface frictional resistance, and an image forming apparatus including the endless belt. The purpose is to do.

  In order to achieve the above object, the present invention provides an endless belt that rotates while contacting an image carrier at a predetermined pressure, and a metal oxide is supported on the surface of the endless belt, and the belt surface The element ratio of the metal constituting the metal oxide is 5% by weight or more and 50% by weight or less.

  According to the present invention, in the endless belt configured as described above, the metal oxide is titanium oxide.

  Further, the present invention is characterized in that the endless belt having the above-described configuration has an elastic layer of at least 100 μm or more.

  The present invention also provides an endless belt having the above-described configuration, an image forming unit that forms a toner image corresponding to an electrostatic latent image by attaching a toner containing an abrasive to the surface of the image carrier, and the image carrier. An image having a primary transfer means for sequentially laminating the toner images developed on the endless belt, and a secondary transfer means for transferring the toner images laminated on the endless belt onto a recording medium at a time. A refresh mode in which the image carrier and the endless belt are brought into contact with each other with a linear velocity difference between the image carrier and the endless belt different from that during image formation during non-image formation. It is characterized by being executable.

  The present invention also provides an endless belt having the above-described configuration, an image forming unit that forms a toner image corresponding to an electrostatic latent image by attaching a toner containing an abrasive to the surface of the image carrier, and the image carrier. An image forming apparatus comprising: a transfer unit that stacks the developed toner image on a recording medium conveyed by the endless belt, wherein the image carrier and the endless belt are formed during non-image formation. A refresh mode in which the image carrier and the endless belt are brought into contact with each other with a linear velocity difference different from that at the time of image formation between them can be executed.

  According to the present invention, in the image forming apparatus configured as described above, a linear velocity difference between the image carrier and the endless belt in the refresh mode is 5% to 80%.

  According to the present invention, in the image forming apparatus configured as described above, the image carrier is a photosensitive drum provided with an amorphous silicon photosensitive layer.

  According to the first configuration of the present invention, the metal oxide is supported on the surface of the endless belt, and the elemental ratio of the metal composing the metal oxide on the belt surface is 5% by weight or more and 50% by weight or less. Accordingly, the surface of the image carrier can be effectively polished without interposing a toner containing an abrasive, and the amount of abrasion of the photosensitive layer can be suppressed. Therefore, it can be suitably used for an image forming apparatus configured to polish the surface of an image carrier using an intermediate transfer belt or a conveyance belt.

  Further, according to the second configuration of the present invention, in the endless belt of the first configuration, titanium oxide that is widely used as a toner external additive and causes filming is supported on the belt surface. Once attached, the filming of titanium oxide on the surface of the image bearing member can be effectively suppressed by utilizing the property of titanium oxide that is more easily attached to the surface.

  According to the third configuration of the present invention, the contact nip between the image carrier and the belt is stabilized by providing the endless belt having the above first or second configuration with an elastic layer of at least 100 μm or more. This makes it possible to uniformly polish the surface of the image carrier. In addition, when an endless belt is used as an intermediate transfer belt, it is possible to prevent image dropout due to stress concentration.

  According to the fourth configuration of the present invention, the endless belt having any one of the first to third configurations is used as the intermediate transfer belt to which the toner images on the image carrier are sequentially transferred, and non-image formation is performed. In some cases, the refreshing mode in which the image carrier and the endless belt are brought into contact with each other with a linear velocity difference different from that during image formation between the image carrier and the endless belt can improve the polishing effect of the image carrier. It is possible to effectively suppress the increase in the coefficient of friction on the surface of the image carrier and the occurrence of filming. Further, the frequency of execution of the refresh mode can be reduced as compared with the conventional case, and wasteful toner consumption other than the printing operation can be suppressed.

  According to the fifth configuration of the present invention, the endless belt having any one of the first to third configurations is used as the transport belt for transporting the recording medium, and the image carrier is used during non-image formation. By carrying out a refresh mode in which the image carrier and the endless belt are brought into contact with each other with a linear velocity difference different from that at the time of image formation between the image carrier and the endless belt, the polishing effect of the image carrier is promoted and the image carrier is promoted. It is possible to effectively suppress the increase in the friction coefficient of the surface and the occurrence of filming. Further, the frequency of execution of the refresh mode can be reduced as compared with the conventional case, and wasteful toner consumption other than the printing operation can be suppressed.

  According to the sixth configuration of the present invention, in the image forming apparatus having the fourth or fifth configuration, the linear velocity difference between the image carrier and the endless belt in the refresh mode is 5% or more and 80% or less. By doing so, it is possible to suppress the amount of abrasion of the photosensitive layer by polishing the surface of the image carrier without excess or deficiency while maintaining the effect of suppressing filming.

  According to the seventh configuration of the present invention, in the image forming apparatus having any one of the fourth to sixth configurations, by using a photosensitive drum provided with an amorphous silicon photosensitive layer as an image carrier, an image can be obtained. The service life of the carrier becomes longer, contributing to higher image quality and lower running costs of the image forming apparatus.

1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment of the present invention. 1 is a block diagram showing a control path of an image forming apparatus according to a first embodiment. Cross-sectional enlarged view of the intermediate transfer belt Diagram showing the process of supporting titanium oxide on the surface of the intermediate transfer belt 6 is a flowchart showing a control procedure of a refresh mode executed in the image forming apparatus of the first embodiment. Schematic sectional view of an image forming apparatus according to a second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the first embodiment of the present invention. In the image forming apparatus (here, a rotary developing type color printer) 100, when performing a copying operation, the photosensitive drum 1 rotating counterclockwise in the drawing is uniformly charged by the charging device 2 in the apparatus main body. The The exposure unit 3 irradiates the photosensitive drum 1 with a laser beam based on the original image data input to an image input unit (not shown) from a personal computer or the like, and the electrostatic latent image on the photosensitive drum 1. Is formed.

  The photosensitive drum 1 is formed by laminating an amorphous silicon photosensitive layer on the surface of an aluminum drum, for example, and the surface is charged by a charging device 2 provided with a charging roller. Then, an electrostatic latent image in which charging is attenuated is formed on the surface that has received the laser beam from the exposure unit 3. As the photosensitive layer, an organic photosensitive layer (OPC photosensitive layer) is used in addition to the amorphous silicon photosensitive layer.

  The rotary type developing unit 4 that supplies toner onto the photosensitive drum 1 is a cartridge type yellow, magenta, cyan, and black developing device 4a, 4b, 4c in which a developing unit and a toner storage unit are integrated. And 4d, and the toner is attached to the electrostatic latent image on the photosensitive drum 1 by sequentially moving the four developing devices 4a to 4d to positions facing the photosensitive drum 1 as the developing unit 4 rotates. Thus, a toner image of each color is formed.

  The intermediate transfer belt 5 onto which the toner image is transferred is wound around the primary transfer rollers 6a and 6b, the belt driving roller 8 and the driven roller 9, and is rotated clockwise in the figure by driving means (not shown) while contacting the photosensitive drum 1. Rotate to. A sheet made of dielectric resin is used for the intermediate transfer belt 5, and a belt in which both ends thereof are overlapped and joined to form an endless shape, or a belt without a seam (seamless) is used.

  When the user inputs image formation start, a yellow toner image is formed on the photosensitive drum 1 at a predetermined timing. Then, the yellow toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 5 by the primary transfer rollers 6 a and 6 b to which a negative transfer bias (when positively charged toner is used) is applied. Thereafter, the toner remaining on the surface of the photosensitive drum 1 is removed by the cleaning device 7, and the developing unit 4 is rotated by a predetermined amount (here, 90 °), so that the magenta toner image is now converted into the photosensitive drum. 1 is transferred onto the intermediate transfer belt 5.

  Thereafter, cyan and black toner images are transferred onto the intermediate transfer belt 5 from the photosensitive drum 1 by the same method as described above. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. A secondary transfer roller 13 is pressed against the intermediate transfer belt 5 at a position facing the belt driving roller 8, and the surface of the intermediate transfer belt 5 is located downstream of the contact surface of the secondary transfer roller 13 in the belt rotation direction. A belt cleaning unit 14 for removing residual toner and paper dust is disposed.

  The sheet P is conveyed from the sheet feeding mechanism 10 via the sheet feeding roller 11 and the registration roller pair 12 toward the intermediate transfer belt 5 on which the toner image is formed as described above, and sequentially onto the surface of the intermediate transfer belt 5. The formed full-color toner image is transferred onto the paper P at a time by the secondary transfer roller 13 to which a negative transfer bias is applied. The sheet on which the toner image is transferred is conveyed to a fixing device 15 having a heating roller 15a and a pressure roller 15b, and the toner image is fixed. The paper P that has passed through the fixing device 15 is discharged to a discharge tray 18 through a paper conveyance path 16 and a discharge roller pair 17.

  On the other hand, when forming images on both sides of the paper P, a part of the paper P that has passed through the fixing device 15 is once protruded from the discharge roller pair 17 to the outside of the device. Thereafter, the paper P is distributed to the double-sided conveyance path 20 by the branching unit 19 by rotating the discharge roller pair 17 in the reverse direction, and is re-conveyed to the secondary transfer roller 13 with the image surface reversed. Then, after the next image formed on the intermediate transfer belt 5 is transferred to the surface of the sheet P on which the image is not formed by the secondary transfer roller 13 and conveyed to the fixing device 15 to fix the toner image, It is discharged to the discharge tray 18.

  Next, the cleaning device 7 will be described in detail. The cleaning device 7 includes a rubbing roller 7a and a cleaning blade 7b. The rubbing roller 7a is pressed against the photosensitive drum 1 at a predetermined pressure, and is driven to rotate in the same direction on the contact surface with the photosensitive drum 1 by a driving means (not shown). The speed is controlled faster than the peripheral speed of 1 (1.2 times here). Examples of the rubbing roller 7a include a structure in which a foam layer made of EPDM rubber and having an Asuka C hardness of 55 ° is formed as a roller body around a metal shaft. The material of the roller body is not limited to EPDM rubber, but may be rubber or foam rubber body of other materials, and those having an Asuka C hardness in the range of 10 to 90 ° are preferably used.

  A cleaning blade 7b is fixed in contact with the photosensitive drum 1 on the surface of the photosensitive drum 1 downstream of the contact surface with the rubbing roller 7a. As the cleaning blade 7b, for example, a polyurethane rubber blade having a JIS hardness of 78 ° is used, and is attached at a predetermined angle with respect to the tangential direction of the photosensitive member at the contact point. Note that the material, hardness, dimensions, amount of biting into the photosensitive drum 1, pressure contact force, and the like of the cleaning blade 7 b are appropriately set according to the specifications of the photosensitive drum 1.

  Residual toner removed from the surface of the photosensitive drum 1 by the rubbing roller 7a and the cleaning blade 7b is discharged to the outside of the cleaning device 7 as the recovery screw (not shown) rotates. As the toner used in the present invention, silica, titanium oxide, strontium titanate, alumina or the like is embedded in the toner particle surface as an abrasive and held so as to partially protrude on the surface. Those that are electrostatically attached to the surface are used.

  Then, by rotating the rubbing roller 7a with a speed difference with respect to the photosensitive drum 1 as described above, the surface of the photosensitive drum 1 is polished with the residual toner containing the abrasive, and the rubbing roller 7a and the cleaning roller are cleaned. The blade 7b removes moisture and contaminants on the drum surface together with the residual toner.

  Next, the control path of the image forming apparatus of the present invention will be described. FIG. 2 is a block diagram showing an example of a control path used in the image forming apparatus of the present invention. It should be noted that since various control of each part of the apparatus is performed when the image forming apparatus 100 is used, the control path of the entire image forming apparatus 100 becomes complicated. Therefore, here, a portion of the control path that is necessary for the implementation of the present invention will be mainly described.

  The control unit 90 includes a central processing unit (CPU) 91 as a central processing unit, a read only memory (ROM) 92 that is a read-only storage unit, a random access memory (RAM) 93 that is a read / write storage unit, A plurality of (two in this case) that transmit a control signal to each device in the temporary storage unit 94, the counter 95, and the image forming apparatus 100 for storing image data and the like, and receive an input signal from the operation unit 50. The I / F (interface) 96 is provided. Further, the control unit 90 can be arranged at an arbitrary location inside the apparatus main body.

  The ROM 92 stores a control program for the image forming apparatus 100, data necessary for control, and the like that are not changed during use of the image forming apparatus 100. The RAM 93 stores necessary data generated during the control of the image forming apparatus 100, data temporarily required for controlling the image forming apparatus 100, and the like. The ROM 92 (or RAM 93) also stores the number of printed sheets for determining whether or not execution of a refresh mode described later is necessary. The counter 95 adds up the number of printed sheets and counts it. Note that the number of times may be stored in the RAM 93, for example, without providing the counter 95 separately.

  In addition, the control unit 90 transmits a control signal from the CPU 91 to the respective units and apparatuses in the image forming apparatus 100 through the I / F 96. In addition, a signal indicating the state and an input signal are transmitted from each part or device to the CPU 91 through the I / F 96. The parts and devices controlled by the control unit 90 include, for example, the charging device 2, the developing unit 4, the primary transfer rollers 6a and 6b, the image forming unit 21 including the cleaning device 7, the secondary transfer roller 13, the fixing device 15, and the like. Examples thereof include an image input unit 40, a bias control circuit 41, and an operation unit 50.

  When the image forming apparatus 100 is a printer as shown in FIG. 1, the image input unit 40 is a receiving unit that receives image data transmitted from a personal computer or the like. When the image forming apparatus 100 is a copying machine, Scanning optical system equipped with a scanner lamp that illuminates the document during copying and a mirror that changes the optical path of the reflected light from the document, a condensing lens that focuses the reflected light from the document and forms an image It is an image reading unit composed of a CCD or the like that converts image light into an electrical signal. The image signal input from the image input unit 40 is converted into a digital signal and then sent to the temporary storage unit 94.

  The bias control circuit 41 is connected to the charging bias power source 42, the developing bias power source 43, the transfer bias power source 44, and the belt cleaning bias power source 45, and operates each of these power sources by an output signal from the control unit 90. Each of these power supplies applies a predetermined bias to the charging device 2, the developing devices 4 a to 4 d, the primary transfer rollers 6 a and 6 b, the secondary transfer roller 13, and the belt cleaning unit 14 in accordance with a control signal from the bias control circuit 41. .

  The operation unit 50 is provided with a liquid crystal display unit 51, LEDs 52 indicating various states, and a numeric keypad 53, and the user operates the operation unit 50 to input instructions, thereby making various settings of the image forming apparatus 100. And execute various functions such as image formation. The liquid crystal display unit 51 displays the state of the image forming apparatus 100, displays the image forming status and the number of copies, and can be used as a touch panel to perform various settings such as functions such as double-sided printing and black-and-white reversal, magnification setting, and density setting. It has become. The numeric keypad 53 is used for setting the number of copies to be printed and for inputting the other party's FAX number when the image forming apparatus 100 also has a FAX function.

  In addition, the operation unit 50 includes a start button for instructing the user to start image formation, a stop / clear button used when the image formation is stopped, and various settings of the image forming apparatus 100 in a default state. A reset button or the like is provided for use.

  Next, the polishing operation on the surface of the photosensitive drum in the image forming apparatus of the present invention will be described. As described above, the photosensitive drum 1 is not sufficiently polished only by providing a linear velocity difference between the rubbing roller 7a and the photosensitive drum 1 and polishing the drum surface using the residual toner after image formation. There is also. Therefore, in the image forming apparatus of the present invention, the intermediate transfer belt 5 having a highly polished metal oxide supported on the surface is used. For example, the image forming apparatus is in a copy start state from a power-off state or a sleep (power saving) mode. When starting up, a polishing operation (hereinafter referred to as a refresh mode) is performed in which the intermediate transfer belt 5 and the photosensitive drum 1 are brought into contact with each other with a predetermined linear velocity difference different from that during image formation.

  Thereby, impurities on the surface of the photosensitive drum 1 can be removed in a short time, the polishing effect on the surface of the photosensitive drum 1 is promoted, and an increase in the friction coefficient on the drum surface is suppressed over a long period of time, and a printing operation is performed. This is an effective polishing system that can also suppress consumption of toner other than the above. The duration per refresh mode is appropriately set according to the configuration of the photosensitive layer to be used, the usage environment of the apparatus, the refresh mode execution interval, and the like. For example, the temperature and humidity around the photosensitive drum may also be detected and the duration may be changed based on the temperature and humidity difference from the outside of the apparatus.

  Further, the refresh mode is automatically started when the cumulative number of printed sheets from the previous execution of the refresh mode reaches a predetermined number or according to the temperature / humidity inside or outside the apparatus detected by the temperature / humidity sensor. Alternatively, it may be started by an input operation by the user.

  Next, the configuration of the intermediate transfer belt 5 will be described in detail. FIG. 3 is a schematic cross-sectional view showing a configuration example of the intermediate transfer belt of the present invention. The intermediate transfer belt 5 is a conductive belt having a three-layer structure including a base material layer 60, an elastic layer 61, and a coat layer 63. The coat layer 63 is in contact with the photosensitive drum 1 (see FIG. 1). The base material layer 60 is a basic material constituting the intermediate transfer belt 5 and imparts a predetermined rigidity, withstands the processing conditions when laminating the elastic layer 61 and the coat layer 63, and further manufacture of the intermediate transfer belt 5. In this case, it is preferable that the material is excellent in workability, heat resistance, slipperiness, and other physical properties. As a material of the base material layer 60, for example, PVDF (polyvinylidene fluoride), polyimide resin, or the like is preferably used.

  The elastic layer 61 imparts elasticity to the intermediate transfer belt 5 to prevent image dropout due to stress concentration. When an elastic belt including an elastic layer 61 of at least 100 μm or more is used as the intermediate transfer belt 5, the contact nip between the drum and the belt is easy to stabilize and uniform polishing is preferable. As a material of the elastic layer 61, for example, hydrin rubber, chloroprene rubber, polyurethane rubber or the like is used. The coat layer 63 protects the elastic layer 61. As the material of the coat layer 63, acrylic, silicon, fluororesin, or the like is used.

In addition, the structure which does not contain the base material layer 60, the structure which contains other layers other than the base material layer 60, the elastic layer 61, and the coat layer 63 may be sufficient, and not only a laminated structure but only the elastic layer 61 is sufficient. A layer structure may be adopted. The surface resistivity of the intermediate transfer belt 5 is preferably 1 × 10 ⁻¹⁰ to 1 × 10 ⁻¹² Ω / □, and the surface hardness is preferably about 10 to 60 in terms of MD-1 hardness.

  A titanium oxide 65 is supported on the surface of the intermediate transfer belt 5. A method of supporting titanium oxide 65 on the belt surface will be described with reference to FIG. As shown in FIG. 4, the intermediate transfer belt 5 is wound around two stretching rollers 70a and 70b, and a coating roller 71 is disposed at a position facing the stretching roller 70a to be brought into contact with the intermediate transfer belt 5. Further, the doctor roller 73 is brought into contact with the coat roller 71 on the upstream side in the rotation direction of the roller with respect to the contact position of the intermediate transfer belt 5, and the application brush 75 is brought into contact with the contact position of the doctor blade 73 on the upstream side in the rotation direction of the roller. Keep it.

  Then, the tension roller 70a (or 70b) is driven to rotate the intermediate transfer belt 5 clockwise at a predetermined linear speed (for example, 100 mm / sec), and the coat roller 71 is used to bring the surface of the intermediate transfer belt 5 to the surface. Titanium oxide 65 is deposited. The coating roller 71 rotates at a linear speed of, for example, 1.2 times with respect to the intermediate transfer belt 5, and supplies titanium oxide 65 to the belt surface and rubs the belt surface with titanium oxide 65. Thereby, titanium oxide 65 adheres to the belt surface. As the coating roller 71, for example, a foaming roller made of EPDM rubber is used.

  The application brush 75 rotates counterclockwise on the surface facing the coating roller 71, and the titanium oxide 65 pumped up by the application brush 75 is applied to the surface of the coating roller 71. The doctor blade 73 plays a role of making the titanium oxide 65 on the coating roller 71 uniform and at the same time making the amount of titanium oxide on the coating roller 71 constant. As the doctor blade 73, for example, a SUS blade having a thickness of 50 μm is used.

  Titanium oxide may significantly increase the surface resistance of the belt when attached to the belt surface. Therefore, it is preferable to use titanium oxide imparted with conductivity. Specifically, titanium oxide (rutile type) conductively treated with antimony-containing tin oxide (ATO) is preferably used.

  By the way, the titanium oxide 65 is still attached to the intermediate transfer belt 5 just by being applied by the coating roller 71, and is immediately detached from the belt surface. Accordingly, a discharge roller 79 connected to an AC power supply 77 is disposed at a position facing the stretching roller 70b and is brought into contact with the intermediate transfer belt 5, and an AC voltage (for example, Vpp = 2.0 kV, frequency 4 kHz) is applied to the discharge roller 79. Is applied. As a result, discharge occurs at a very small interval between the intermediate transfer belt 5 and the discharge roller 79, and discharge products adhere to the surface of the intermediate transfer belt 5.

  This discharge product contains NOx, and adheres to the belt surface more firmly as the belt surface and the surrounding humidity are higher. The discharge product plays a role in firmly attaching the highly hygroscopic titanium oxide 65, and the titanium oxide 65 does not peel off by simple friction. The amount of titanium oxide supported on the belt surface can be controlled by the discharge processing time by the discharge roller 79, and the amount of titanium oxide supported on the belt surface increases as the discharge processing time increases.

As the discharge roller 79, a so-called charging roller coated with conductive rubber is used, but a metal roller may be used as it is. However, if there is a local agglomerated portion of the conductive agent on the belt, the trace of the local leak may become a leak trace, so a roller coated with conductive rubber having a volume resistivity of 1 × 10 ⁵ Ω · cm or less Are preferably used.

  By executing the refresh mode using the intermediate transfer belt 5 thus manufactured, it is possible to prevent filming of the external additive on the drum surface and effectively suppress an increase in the surface friction coefficient. .

  The amount of titanium oxide 65 supported on the surface of the intermediate transfer belt 5 can be measured using EPMA (Electron Probe Micro Analysis). EPMA detects constituent elements by measuring the spectrum of characteristic X-rays emitted by the transition of inner-shell electrons of the elements that make up a substance when irradiated with an accelerated electron beam, and the element ratio (concentration) The solid sample can be analyzed almost nondestructively.

  In the present invention, the elemental ratio of titanium on the surface of the intermediate transfer belt 5 determined by the peak intensity ratio of TiKα (4.51 eV) when irradiated with an electron beam by EPMA at an acceleration voltage of 10 kV is 5 wt% or more and 50 wt%. % Of the intermediate transfer belt 5 is used. When the element ratio of titanium is less than 5% by weight, the effect of suppressing filming on the surface of the photosensitive drum is small and the surface friction coefficient is increased. On the other hand, when the elemental ratio of titanium exceeds 50% by weight, the abrasion amount of the photosensitive layer on the surface of the photosensitive drum is increased, and the useful life of the photosensitive drum is shortened.

  It should be noted that a metal oxide other than titanium oxide such as zinc oxide may be carried on the intermediate transfer belt 5 as long as it has a polishing effect on the photosensitive drum 1. However, titanium oxide is widely used as a toner external additive, and is a substance that causes filming on the photosensitive drum 1 and that once titanium oxide is adhered, it is more likely to adhere on the titanium oxide. Therefore, by preliminarily supporting titanium oxide on the intermediate transfer belt 5, titanium oxide, which is an external toner additive, is preferentially adhered to the intermediate transfer belt 5 side to perform filming on the photosensitive drum 1. It can be effectively suppressed. Therefore, titanium oxide is particularly preferable among the metal oxides.

  FIG. 5 is a flowchart illustrating an example of a refresh mode executed in the image forming apparatus according to the first embodiment. With reference to FIG. 1 and FIG. 2, the execution procedure of the refresh mode will be described along the steps of FIG.

  First, when the printing process is started by a user operating the operation panel 50 or a personal computer (step S1), the counter 95 counts the number of printed sheets n (step S2), and whether or not the designated number of sheets has been printed. Is determined (step S3).

  After the printing is completed, the control unit 90 determines whether or not the cumulative number of printed sheets from the previous refresh mode execution has reached a predetermined number (step S4). The linear velocity is decelerated to half that at the time of image formation (step S5). As a result, a linear velocity difference of 50% is generated between the photosensitive drum 1 and the intermediate transfer belt 5, so that titanium oxide is supported on the surface. The photosensitive drum 1 is rubbed by the intermediate transfer belt 5 to polish the drum surface.

  Thereafter, it is determined whether or not a predetermined time has passed (step S6). If the predetermined time has passed, the drum linear velocity is restored (step S7), the intermediate transfer cleaning bias is turned ON, and the intermediate transfer belt 5 is turned on. The upper residual toner is removed (step S8). Then, it is determined whether or not the intermediate transfer belt 5 has made one revolution (step S9). After the intermediate transfer belt 5 has made one revolution, the intermediate transfer cleaning bias is turned off (step S10) and the refresh mode is terminated. If the predetermined number of sheets has not been reached in step S4, the intermediate transfer cleaning bias is turned on immediately after the printing is finished, the residual toner on the intermediate transfer belt 5 is removed, and the process ends (steps S8 to S10).

  According to the above procedure, it is possible to effectively suppress an increase in the frictional resistance of the drum surface by the polishing operation using the intermediate transfer belt 5, and it is possible to continuously output a good image. In addition, useless toner consumption other than the printing operation can be suppressed. Furthermore, the frequency of execution of the refresh mode can be reduced as compared with the conventional case, and the duration time per refresh mode can be shortened, and the image forming efficiency can be increased.

  Note that the control shown in FIG. 5 is merely an example, and can be appropriately changed according to the specifications of the apparatus. For example, in the control of FIG. 5, the linear velocity of the photosensitive drum 1 is reduced to ½ that during image formation to create a linear velocity difference between the photosensitive drum 1 and the intermediate transfer belt 5. Instead of the drum 1, the linear speed of the intermediate transfer belt 5 may be reduced.

  The difference in linear velocity between the photosensitive drum 1 and the intermediate transfer belt can be appropriately changed according to the amount of titanium oxide supported on the surface of the intermediate transfer belt 5, the duration of the refresh mode, and the like. For example, when the element ratio of titanium on the belt surface is 5% by weight or more and 50% by weight or less, the linear velocity difference is set in the range of 5% to 80% in consideration of the filming suppression effect and the amount of abrasion of the photosensitive layer. Is preferred. When the linear velocity difference is less than 5%, a sufficient filming suppression effect cannot be obtained. Also, if the linear velocity difference exceeds 80%, the amount of abrasion of the photosensitive layer increases, and the durability of the photosensitive drum decreases, and the polishing in the drum longitudinal direction is caused by variations in drum / belt tension in the drum longitudinal direction. Unevenness is likely to occur.

  In addition, a method of accelerating the linear velocity of the photosensitive drum 1 or the intermediate transfer belt 5 to create a linear velocity difference between the photosensitive drum 1 and the intermediate transfer belt 5 is possible. In this case, the photosensitive drum 1 Alternatively, since the load on the motor that drives the intermediate transfer belt 5 increases, it is preferable to reduce the linear velocity of either the photosensitive drum 1 or the intermediate transfer belt 5.

  FIG. 6 is a schematic diagram showing the configuration of the image forming apparatus according to the second embodiment of the present invention. The present embodiment is a tandem type color image forming apparatus in which image forming units 21a to 21b provided corresponding to images of four colors (yellow, cyan, magenta, and black) are arranged, and charging devices 2a to 2d. , Exposure units (LED heads) 3a to 3d, developing devices 4a to 4d, and cleaning devices 7a to 7d are provided in the respective image forming units 21a to 21b. Further, an endless conveying belt 80 for sequentially conveying the paper P to the image forming units 21a to 21b instead of the intermediate transfer belt 5 is disposed so as to contact the lower portions of the photosensitive drums 1a to 1d. The toner images of the respective colors formed on the photosensitive drums 1a to 1d by 81a to 81d are sequentially transferred onto the paper P.

  Also in the present embodiment, titanium belt is supported on the belt surface, and the conveyance belt 80 having a titanium element ratio of 5% to 50% on the belt surface is used to form the conveyance belt 80 and the photosensitive drum 1a during non-image formation. The refresh mode in which a contact is made with a linear velocity difference between ˜1d is executed.

  As a result, the surfaces of the photosensitive drums 1a to 1d can be sufficiently polished without consuming wasteful toner using the conveyor belt 80, and an increase in the friction coefficient of the drum surface can be effectively suppressed. Further, the duration and execution frequency per refresh mode are also reduced. Since the detailed method and execution procedure of the refresh mode are the same as those in the first embodiment, description thereof is omitted.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the photosensitive drum may be stopped or intermittently rotated while the intermediate transfer belt or the conveyance belt is rotated during the refresh mode, or the intermediate transfer belt or the conveyance belt may be rotated while the photosensitive drum is rotated. It may be stopped or intermittently rotated. Hereinafter, the effects of the present invention will be described in more detail with reference to examples.

[Preparation of intermediate transfer belt]
Carbon black (MA # 100, manufactured by Mitsubishi Chemical Corporation) was added as a conductive filler to 100 parts by weight of the polyamideimide precursor solution, and dispersed using three rolls to adjust the varnish. Further, NMP (N-methyl-2-pyrrolidone) was used as a solvent for viscosity adjustment. The obtained varnish is applied to the peripheral surface of a cylindrical mold, and is heated and cured using an oven while rotating the mold to prevent dripping, and a base layer made of polyamideimide resin having a thickness of 80 μm is obtained. It was. A silicone primer (Primer No. 4 manufactured by Shin-Etsu Chemical Co., Ltd.) was thinly applied to the surface of the obtained base material layer.

  On the other hand, 100 parts by weight of two-part addition polymerization liquid silicone rubber (KE1606 manufactured by Shin-Etsu Chemical Co., Ltd.), 15 parts by weight of carbon black (Ketjen Black EC manufactured by Mitsubishi Chemical Co., Ltd.) as a conductive filler, silicone oil (Shin-Etsu Chemical Co., Ltd.) 50 parts by weight of RTV thinner manufactured by the company was added and dispersed using three rolls. Silicone oil and a silicone rubber curing agent were added to the obtained mixture and mixed using a high-speed rotary stirrer (HM-500 manufactured by Keyence Corporation) to obtain an elastic layer composition.

  Leveling and setting the liquid silicone component at room temperature for 30 minutes while applying the obtained composition to the surface of the base material layer formed on the cylindrical mold and rotating the mold at a low speed to prevent dripping Went. Thereafter, heating was performed to accelerate the curing, the silicone rubber was cured, and the base material layer and the elastic layer were integrated.

  Next, an aqueous carbon black dispersion was added to a polyether anionic urethane resin emulsion (Yodosol RX-7 manufactured by Nippon SC) and mixed using a high-speed rotary stirrer to obtain a composition for a surface layer. The obtained composition was applied to the surface of the elastic layer formed on the cylindrical mold, and air-dried at room temperature for 30 minutes while rotating the mold at a low speed to prevent dripping, and then at 140 ° C. Baking was performed for 45 minutes to form a surface layer having a thickness of 20 μm.

  Titanium oxide was supported on the surface of the intermediate transfer belt 5 having the three-layer structure of the base material layer, the elastic layer, and the surface layer obtained by the above-described procedure, using the apparatus shown in FIG. As the titanium oxide, a rutile type titanium oxide conductively treated with antimony-containing tin oxide was used. The weight ratio of titanium element on the surface of the intermediate transfer belt when the discharge treatment time by the discharge roller 79 was changed was measured. The titanium element weight ratio was determined by EDX measurement using a scanning electron microscope (JEOL JSM-6380LV manufactured by JEOL Ltd.). That is, the titanium element weight ratio on the surface of the intermediate transfer belt was determined from the peak intensity ratio of TiKα (4.51 eV) when irradiated with an electron beam at an acceleration voltage of 10 kV. The results are shown in Table 1.

  As is clear from Table 1, the weight ratio of titanium element on the surface of the intermediate transfer belt increased as the discharge treatment time increased. From this result, it was confirmed that the amount of titanium oxide supported on the belt surface can be controlled by adjusting the discharge treatment time.

  Using the image forming apparatus as shown in FIG. 1, the polishing effect on the drum surface by the intermediate transfer belt of the present invention was evaluated. As a test method, after 10 test images with a printing rate of 5% were printed, one job was performed until the photosensitive drum surface was rubbed for one round of the intermediate transfer belt with a predetermined belt / drum linear velocity difference. . Visual observation of drum surface filming after repeating the above job 1,000 times (after printing 10,000 sheets) while changing the titanium element ratio and belt / drum linear velocity difference on the surface of the intermediate transfer belt. The surface friction coefficient μ was measured. Further, the amount of abrasion of the photosensitive layer was measured at three locations (left, middle, and right) on the drum surface.

  The titanium element ratio on the surface of the intermediate transfer belt was determined by EDX measurement using a scanning electron microscope (JEOL JSM-6380LV manufactured by JEOL Ltd.). The results are shown in Table 2. In Table 2, the column “Filming occurrence” is indicated as “◯” when no filming is observed, “Δ” when slightly generated, and “X” when markedly generated. In the “determination” column, a case where the filming is good (increased friction coefficient) and the photosensitive layer is scraped is good, and the occurrence of filming or the amount of scraping of the photosensitive layer is recognized. The case where there is no practical problem is indicated by Δ, and the case where there is a practical problem is indicated by ×.

  As is clear from Table 2, in the present inventions 1 to 9 in which the titanium element ratio on the belt surface is 5% by weight or more and 50% by weight or less and the belt / drum linear velocity difference is 5% to 80%, The friction coefficient was as low as 2.5 to 4.5, and no filming was observed. Further, the abrasion amount of the photosensitive layer was less than 1,000 mm.

  Titanium element ratio of 21.5 wt%, 31.0 wt%, 42.2 wt%, the present invention 10-12 having a belt / drum linear velocity difference of 25%, and a belt / drum linear velocity difference of 85% In the inventions 13 and 14, the amount of abrasion of the photosensitive layer was slightly increased, but no filming was observed. Further, in the present inventions 15 and 16 in which the belt / drum linear velocity difference was 3%, the friction coefficient of the drum surface was slightly high as 6.1 to 6.2, and the occurrence of filming was slightly recognized.

  On the other hand, in Comparative Example 1 in which the titanium element ratio was 3.5% by weight, the friction coefficient of the drum surface was as high as 6.5, and the occurrence of filming was recognized remarkably. On the other hand, in Comparative Example 2 in which the titanium element ratio was 56.0% by weight, the abrasion amount of the photosensitive layer exceeded 1,000 mm, and there was a problem in the durability of the photosensitive drum.

  From the above results, it was confirmed that when the titanium element ratio on the surface of the intermediate transfer belt is 5% by weight or more and 50% by weight or less, the filming suppression effect is high and the amount of abrasion of the photosensitive layer can be suppressed. It was also confirmed that the belt / drum linear speed difference is preferably in the range of 5% to 80%.

  INDUSTRIAL APPLICABILITY The present invention can be used for an endless belt such as an intermediate transfer belt or a conveyance belt that rotates while contacting an image carrier with a predetermined pressure, and supports the metal oxide on the surface of the endless belt and the belt surface. The elemental ratio of the metal constituting the metal oxide is 5% by weight or more and 50% by weight or less. Thus, it is possible to provide an endless belt that can effectively polish the surface of the image carrier without interposing a toner containing an abrasive, and can reduce the consumption of unnecessary toner and extend the life of the image carrier. it can.

  In addition, since titanium oxide is supported as a metal oxide, titanium oxide, which is widely used as an external toner additive, is preferentially applied to the belt surface by utilizing the property of titanium oxide that easily adheres to it once attached. The filming on the surface of the image carrier can be effectively suppressed.

  In addition, by using an endless belt having an elastic layer of at least 100 μm or more, the contact nip between the image carrier and the belt is easily stabilized, and uniform polishing is possible. Further, it is possible to prevent the image dropout phenomenon when used as an intermediate transfer belt.

  Further, the endless belt of the present invention is used as an intermediate transfer belt to which toner images on the image carrier are sequentially transferred or as a transport belt for transporting a recording medium, and between the image carrier and the endless belt. By executing a refresh mode in which the image carrier and the endless belt are brought into contact with each other with a linear velocity difference different from that at the time of image formation, the polishing effect of the image carrier is promoted and the friction coefficient on the surface of the image carrier is increased. The image forming apparatus can effectively suppress the occurrence of filming. Further, the frequency of execution of the refresh mode can be reduced as compared with the conventional case, and wasteful toner consumption other than the printing operation can be suppressed.

  Further, by making the difference in linear velocity between the image carrier and the endless belt in the refresh mode 5% or more and 80% or less, the surface of the image carrier is polished without excess or deficiency while maintaining an appropriate filming suppression effect. Thus, the amount of abrasion of the photosensitive layer can be suppressed.

1 Photosensitive drum (image carrier)
2 Charging device 3 Exposure unit 4 Developing device 5 Intermediate transfer belt (endless belt)
6a, 6b Primary transfer roller (primary transfer means)
7 Cleaning device 9 Secondary transfer roller (secondary transfer means)
19 Belt cleaning unit 21 Image forming section 65 Titanium oxide 80 Conveying belt (endless belt)
81a to 81d Transfer roller (transfer means)
90 control unit 100 image forming apparatus

Claims (7)

An endless belt that rotates while contacting the image carrier with a predetermined pressure,
A metal oxide is supported on the surface of the endless belt, and an element ratio of the metal constituting the metal oxide on the belt surface is 5% by weight or more and 50% by weight or less. .   The endless belt according to claim 1, wherein the metal oxide is titanium oxide.   The endless belt according to claim 1, wherein the endless belt has an elastic layer of at least 100 μm or more. An endless belt according to any one of claims 1 to 3,
An image forming unit that forms a toner image corresponding to an electrostatic latent image by attaching a toner containing an abrasive to the surface of the image carrier;
Primary transfer means for sequentially laminating toner images developed on the image carrier on the endless belt;
A secondary transfer means for transferring the toner image laminated on the endless belt onto a recording medium at a time, and an image forming apparatus comprising:
During non-image formation, a refresh mode in which the image carrier and the endless belt are brought into contact with each other with a linear velocity difference different from that during image formation between the image carrier and the endless belt can be executed. An image forming apparatus. An endless belt according to any one of claims 1 to 3,
An image forming unit that forms a toner image corresponding to an electrostatic latent image by attaching a toner containing an abrasive to the surface of the image carrier;
An image forming apparatus comprising: a transfer unit that stacks a toner image developed on the image carrier on a recording medium conveyed by the endless belt;
During non-image formation, a refresh mode in which the image carrier and the endless belt are brought into contact with each other with a linear velocity difference different from that during image formation between the image carrier and the endless belt can be executed. An image forming apparatus.   6. The image forming apparatus according to claim 4, wherein a linear velocity difference between the image carrier and the endless belt in the refresh mode is 5% to 80%.   The image forming apparatus according to claim 4, wherein the image bearing member is a photosensitive drum provided with an amorphous silicon photosensitive layer.

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