JP2016085317A - Image formation apparatus, and static eliminating method for latent image carriers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make possible elongation of the service life of driving means while suppressing developer consumption.SOLUTION: An image formation apparatus equipped with a photoreceptor drum, an electrifying device that uniformly electrifies the surface of the photoreceptor drum, an exposing device that forms an electrostatic latent image by exposing the uniformly electrified surface of the photoreceptor drum, a developing device that develops the electrostatic latent image formed on the photoreceptor drum with a developer into a toner image and a photoreceptor drive motor that endlessly moves the photoreceptor drum. In this image formation apparatus, when to end image forming operation, drive by drive means is stopped after exposing the latent image carrier part, which is to be positioned between the point of exposure by exposing means and the point of development by developing means at the end of image forming operation at the time of having stopped drive by the driving means, and when to start image forming operation, after starting drive by the driving means, exposure over the latent image carrier is accomplished by the exposure means until the latent image carrier positioned at the point of exposure means by the exposing means reaches the point of exposure by the exposure means.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, a copying machine or the like using an electrophotographic method, and a method for discharging a latent image carrier that discharges a latent image carrier included in the image forming apparatus.

  Conventionally, an electrostatic latent image is formed by exposing the surface of a photosensitive member as a latent image carrier uniformly charged by a charging unit to the same polarity as the toner charging polarity by using an exposure unit to attenuate the potential. A toner image obtained by developing a formed electrostatic latent image with a developing means is known to be transferred to an intermediate transfer member, which is a transfer target, or a recording medium.

  In Patent Document 1, when the printing operation is completed, before the driving unit that drives the photosensitive member and the developing unit is stopped, the photosensitive member is rotated by one turn and the entire surface of the photosensitive member is exposed by the exposing unit. An image forming apparatus for discharging a body is disclosed. In such a configuration, when the driving unit is stopped at the end of the printing operation, the photosensitive member portion located upstream of the exposure point in the rotation (endless movement) direction of the photosensitive member, or downstream of the exposure point in the rotation direction of the photosensitive member. The position of the photosensitive member located is neutralized. Therefore, when starting the next printing operation, when the driving means is started, the photosensitive member portion that passes through the developing point before the uniformly charged photosensitive member portion reaches the developing point at the time of the printing operation. Are all static-eliminated. Therefore, if the development bias of the developing means is not applied until the uniformly charged photoconductor portion at the time of the printing operation reaches the development point, the photoconductor portion from the developing means (0 V). To (0V), carrier adhesion does not occur and toner adhesion does not occur.

  However, in the image forming apparatus disclosed in Patent Document 1 described above, at the end of the printing operation, before the driving unit is stopped, the entire circumference of the photoreceptor is in a state of being neutralized by exposure only for the exposure. Rotate the photoreceptor one extra turn. As described above, when the photosensitive member is rotated more than once every time the printing operation is completed, there arises a problem that the life of the driving unit is shortened.

  In order to solve the above-mentioned problems, the invention of claim 1 includes a latent image carrier, a charging means for uniformly charging the surface of the latent image carrier, and the surface of the latent image carrier that is uniformly charged. Exposure means for forming an electrostatic latent image by exposure, developing means for developing the electrostatic latent image formed on the latent image carrier as a toner image with a developer, and moving the latent image carrier endlessly In the image forming apparatus including the driving unit, when the image forming operation is finished, the driving unit is positioned between the exposure point by the exposure unit and the development point by the developing unit when the driving of the driving unit is stopped. After the latent image carrier portion is exposed by the exposure means, the drive means is stopped, and when the image forming operation is started, the drive means is started and before the drive is started. Located at the charging point by the above charging means Latent image carrier moiety is, until it reaches the exposure point by the exposure means, is characterized in that exposing the image bearing member on by the exposure means.

  According to the present invention, it is possible to obtain a specific effect that the life of the driving unit can be extended while suppressing the consumption of the developer.

FIG. 2 is a schematic diagram illustrating a schematic configuration of a printer 200 according to the present embodiment. 2 is an explanatory diagram of a control system of the printer 200. FIG. 6 is a timing chart showing a monochrome printing operation sequence of a conventional image forming apparatus. FIG. 3 is an enlarged schematic view of an image forming unit 11 and a transfer unit 20. 9 is a timing chart showing a full color printing operation sequence of a conventional image forming apparatus. 6 is a timing chart showing a monochrome printing operation sequence of the image forming apparatus of the present embodiment. FIG. 6 is a schematic diagram for explaining a charge removal process of the photosensitive drum according to the embodiment. 6 is a timing chart showing a full-color printing operation sequence of the image forming apparatus of the present embodiment.

Hereinafter, an embodiment of an image forming apparatus to which the present invention is applied will be described.
First, the configuration and operation of a full-color printer (hereinafter referred to as printer 200) that is an image forming apparatus according to the present embodiment will be described with reference to FIG.
FIG. 1 is a schematic diagram illustrating a schematic configuration of the printer 200.
As shown in FIG. 1, the printer 200 is a tandem intermediate transfer type printer, and includes four image forming units 11Y, 11M, 11C, and 11K for forming a full-color image on a sheet P that is a recording medium. The image forming unit 10 is provided. The image forming units 11Y, 11M, 11C, and 11K use toners of colors corresponding to yellow (Y), magenta (M), cyan (C), and black (K), respectively.
In addition, the four-color toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K, which are latent image carriers included in the image forming units 11 of the image forming unit 10, are linearly overlapped. A transfer unit 20 is also provided which, after being transferred, is secondarily transferred collectively onto a sheet P as a recording medium. The photosensitive drums 1Y, 1M, 1C, and 1K have a cylindrical shape of φ30, and rotate at a peripheral speed of 50 to 200 [mm / s].

  A paper feed unit 40 that feeds the paper P to the secondary transfer unit 23 of the transfer unit 20, a fixing unit 30 that fixes the toner image secondarily transferred by the secondary transfer unit 23 onto the paper P, and a fixing unit 30 The paper discharge unit 52 for discharging the paper P on which the toner image is fixed to the outside of the apparatus main body 100 is also provided. Also, there are a main body control unit 110 that is a control means for controlling the operation of each unit that is required to control the operation provided in the apparatus main body 100 and the device included in each unit, and each drive source, power supply device, waste toner container, and the like. I have.

The main parts and devices described above are arranged as follows.
At substantially the center in the apparatus main body 100, there are four primary transfer units 22Y, 22M, 22C, and 22K as primary transfer units, a secondary transfer unit 23 as a secondary transfer unit, and an intermediate transfer unit as an intermediate transfer member. A transfer unit 20 having a belt 21 and the like is disposed. The transfer unit 20 has an image forming unit 10 having four image forming units 11Y, 11M, 11C, and 11K in the upper part of the drawing, a paper feeding unit 40 in the lower part of the drawing, and a right side in the figure. The fixing unit 30 is disposed obliquely above, and the main body control unit 110 serving as control means is disposed obliquely to the left in the figure. A paper discharge unit 52 is disposed obliquely above and to the left of the fixing unit 30 in the figure. Between the paper discharge unit 52 and the fixing unit 30 and between the fixing unit 30 and the secondary transfer unit 23 of the transfer unit 20. In addition, between the secondary transfer unit 23 and the paper feeding unit 40, there is a conveyance path 50 for the paper P fed from the paper feeding unit 40. Further, the portion of the apparatus main body 100 where the paper discharge unit 52 is provided protrudes upward compared to the other portions, and a paper discharge port 53 is formed on the left side in the figure. A stacking tray portion 71 is formed on the top plate portion on the left side of the mouth 53 in the drawing.

  The image forming unit 10 includes image forming units 11Y, 11M, 11C, and 11K. Each image forming unit 11 has a color of yellow (Y), magenta (M), cyan (C), and black (K). A toner image separated into each color is formed on each photosensitive drum 1 by a corresponding developer. As described above, in the tandem type image forming apparatus, monochromatic toner images such as yellow (Y), magenta (M), cyan (C), and black (K) are mainly formed on the surface of the photosensitive drum 1. Each of the four image forming units 11Y, 11M, 11C, and 11K has a developing device 5 that uses a one-component developer. Further, each image forming unit 11 differs only in the color of the toner contained in the developer to be used, and the other basic configurations are substantially the same. Therefore, in the following description, it is particularly necessary to specify the color and arrangement. As long as Y, M, C, and K are omitted, description will be made. Further, the reference numerals of the constituent members of each image forming unit 11 will be described with reference to the reference numerals of the image forming unit 11K shown in FIG.

  The photosensitive drum 1 is a latent image carrier that carries an electrostatic latent image formed on the surface of the photosensitive drum 1 after being uniformly charged by the charging device 2 and then exposed by the exposure device 3. In addition, an image carrier that carries and conveys a toner image obtained by developing the electrostatic latent image formed on the surface by the developing device 5 until the toner image is primarily transferred onto the intermediate transfer belt 21 by the primary transfer unit 22. But there is. The photosensitive drum 1 is rotated (endlessly moved) by the rotational driving force of the photosensitive member driving motor, which is a latent image carrier driving motor.

  This printer 200 has two photosensitive member driving motors, one rotating the photosensitive drum 1 of the image forming unit 11K and the other rotating member included in the image forming unit 11K via a gear train. To drive. In addition, the other image forming units 11Y, 11M, and 11C receive a rotational driving force for each image forming unit 11 through a gear train, and further provide gears to the respective photosensitive drums 1 and other rotating bodies. A rotational driving force is transmitted through the row. In this printer 200, a belt drive motor that is a transfer member drive motor that drives the intermediate transfer belt 21 and a photoconductor drive motor that drives the photoconductor drum 1K are separately provided. You may use the same thing via.

  As shown in FIG. 1, each of the image forming units 11 is arranged around the photosensitive drum 1 with a charging device 2 having a charging roller as a charging unit disposed diagonally to the left of the photosensitive drum 1 as a starting point. The components are arranged in the following order in the clockwise direction in the figure. A charging device 2, an exposure device 3 as an exposure unit, a development device 5 as a development unit, a primary transfer unit 22 as a transfer unit, and a photoconductor cleaning device 7 as a latent image carrier cleaning unit are arranged. Here, the primary transfer unit 22 is disposed so as to face the photosensitive drum 1 via the intermediate transfer belt 21 and the intermediate transfer belt 21 which is a transfer member of the primary transfer unit 22 and is also a transfer target member of the primary transfer unit 22. And a primary transfer roller 9 as an application member.

  The charging device 2 is a contact-type charger having a roller-shaped charging roller connected to a charging high-voltage power source (see FIG. 2), which is one of power supply means. The charging roller rotates the surface of the photosensitive drum 1 (endless movement), and the surface of the photosensitive drum 1 is negatively charged by a charging bias applied with electric power supplied from the charging high-voltage power source to the charging device 2. For example, it is uniformly charged to −500 [V]. The charging bias is DC or a voltage in which AC is superimposed on DC.

  The exposure apparatus 3 is a photosensitive drum 1 that is uniformly charged by a laser beam scanner using a laser diode or an LED (Light Emitting Diode) array based on image data from an external device such as a personal computer connected to the printer 200. Expose the surface. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 1. Specifically, the uniformly charged photosensitive drum 1 is exposed based on the image data. An electrostatic latent image is formed by lowering the surface of the exposed portion to a negative polarity potential, for example, −50 [V], and negative-positive development in which the negatively charged toner is adhered by the developing device 5 is enabled. The exposure device 3 performs the surface of the photosensitive drum 1 after the transfer of the toner image from the photosensitive drum 1 to the intermediate transfer belt 21 which is a transfer target provided in the transfer unit 20 or before the formation of the electrostatic latent image. It also functions as a charge removal means for removing charge.

  The developing device 5 includes a developing roller 6 that is a developer carrying member, a part of which is exposed so as to face the photosensitive drum 1 from an opening of a developing container that is not labeled, and a supply that is not labeled A developing device of a one-component developing system having a roller. A doctor blade which is a developer layer thickness regulating member attached upstream of the developing roller 6 in the rotation direction of the developing container opening, an inlet seal attached to the end of the opening to which the doctor blade is not attached, a stirring paddle, etc. It also has the member. The electrostatic latent image formed by exposure of the exposure device 3 on the surface of the photosensitive drum 1 is included in the developer carried and conveyed by the developing roller 6 to the developing position where the photosensitive drum 1 and the developing roller 6 face each other. A toner image is attached to form a visible toner image (development).

  Specifically, the toner contained in the developer has a negative polarity due to the agitation by the supply roller and the agitation paddle in the developing container and the friction when the layer thickness is regulated by the doctor blade supported by the developing roller 6. To charge. A developing bias is applied to the developing roller 6 with electric power supplied to the developing device 5 from the developing high-voltage power source 125 of FIG. 2, which is one of power supply means, and faces the photosensitive drum 1 at the developing position. The surface of the developing roller 6 is charged to a negative polarity potential, for example, −200 [V]. By charging in this way, the developing roller 6 is caused by the potential difference of the exposed portion where the surface potential which is an electrostatic latent image on the photosensitive drum 1 is lowered, for example, +50 [V], for example, +150 [V]. A negative polarity toner is moved from and attached to the electrostatic latent image on the photosensitive drum 1 from the surface. The toner will be described later. An upper portion of the developing device 5 contains a replaceable developer, and is connected to the developing device 5, and a toner supply container 4 that supplies the developer into the developing container of the developing device 5 is disposed. In this embodiment, the toner supply container 4 directly supplies toner into the developing container. However, the toner supply container 4 may supply toner to the developing container by providing a supply path in the apparatus main body 100.

  The photoconductor cleaning device 7 scrapes off the remaining toner remaining on the photoconductor drum 1 without being primarily transferred from the photoconductor drum 1 to the intermediate transfer belt 21 from the photoconductor drum 1 and the photoconductor drum case. And a photosensitive member cleaning blade 8 which is a cleaning member to be removed. In addition, it has a residual toner conveyance screw that conveys the removed residual toner to one end side of the photoconductor cleaning case, and the residual toner conveyed to the one end side is conveyed by a conveyance tube and a coil in the tube connected to the waste toner container. It is conveyed into a waste toner container. The waste toner container is provided so as to be detachable from the apparatus main body 100. A sensor for detecting the amount of stored waste toner is provided in the apparatus main body 100. When the storage of waste toner exceeding a predetermined amount is detected, the operation unit A waste toner disposal instruction is displayed on the display panel (see FIG. 2).

  The transfer unit 20 includes four primary transfer portions 22Y, 22M, 22C, 22K, a secondary transfer portion 23, an intermediate transfer belt 21, and the like. Further, the intermediate transfer belt 21 is in contact with the photosensitive drums 1 of the image forming units 11Y, 11M, 11C, and 11K at the time of full-color image formation and only to the photosensitive drum 1K of the image formation unit 11K at the time of monochrome image formation. A belt contact / separation mechanism 29 that changes the trajectory of the transfer belt 21 is also provided. Further, a belt cleaning device 27 as an intermediate transfer member cleaning device and an optical sensor 28 are also provided.

  The intermediate transfer belt 21 is an intermediate transfer body that moves endlessly. The intermediate transfer belt 21 functions as a transfer member and a transfer target in each primary transfer section 22 and also functions as a transfer body in a secondary transfer section 23 that is a secondary transfer unit. It is also an image carrier. The intermediate transfer belt 21 is stretched by a transfer driving roller 24 which is also a secondary transfer counter roller on the right side in the figure, and is tensioned by a tension roller 26 which is driven and rotated on the left side in the figure.

  On the inner periphery of each image forming unit 11 between the transfer driving roller 24 and the tension roller 26 on the side facing each photosensitive drum 1, the following rotating body is disposed. The primary transfer roller 9 provided in each primary transfer unit 22, the cleaning counter roller 27b of the belt cleaning device 27, and the three support rollers 29a, b, c provided in the belt contact / separation mechanism. These rotators are the cleaning counter roller 27b, support roller 29a, primary transfer roller 9Y, primary transfer roller 9M, primary transfer roller 9C, support roller 29b, primary transfer from the upstream side in the moving direction of the intermediate transfer belt 21. The rollers 9K and the support rollers 29c are arranged in this order.

  The intermediate transfer belt 21 is a transfer drive roller 24 that is also a secondary transfer counter roller on the right side in the drawing, and is stretched by a tension roller 26 that is driven to rotate on the left side in the drawing and is driven to rotate by a belt drive motor. The endless movement in the counterclockwise direction in FIG. The tension roller 26 absorbs the expansion and contraction of the intermediate transfer belt 21 that is expanded and contracted by the operation of the belt contact / separation mechanism 29 and whose trajectory is changed. The drive source of the transfer drive roller 24 and the image forming unit 1 can be independent or common. Since the drive of the image forming unit 1K and the transfer drive of the transfer drive roller 24 are often turned ON / OFF simultaneously, the drive of the image forming unit 1K and the transfer drive of the transfer drive roller 24 are performed in order to reduce the size and cost of the main body. It is desirable to make it common. As a transfer belt stretching mechanism, a tension roller 26 is pressed against both roller shafts by a spring.

  Further, the track of the intermediate transfer belt 21 changes as follows by the operation of the belt contact / separation mechanism 29. At the time of full-color image formation, the apex portions of the primary transfer roller 9 and the three support rollers 29a, 29b, 29c that contact the intermediate transfer belt 21 are the apexes of the transfer driving roller 24, the tension roller 26, and the cleaning counter roller 27b. The height in the vertical direction in the figure is higher than the portion. With this increase, the locus of the intermediate transfer belt 21 on the side facing the photosensitive drums 1 between the transfer driving roller 24 and the tension roller 26 protrudes upward in the figure between the support roller 29a and the support roller 29c. The intermediate transfer belt 21 is a locus of contact with the photosensitive drums 1Y, 1M, 1C, and 1K.

  During the monochrome printing operation, the support roller 29b, the primary transfer roller 9K, and the support roller 29c apex of the intermediate transfer belt 21 are in contact with the apexes of other rotating bodies that are in contact with the inner peripheral side of the intermediate transfer belt 21. The height in the vertical direction in the figure increases. With this increase, the locus of the intermediate transfer belt 21 on the side facing the photosensitive drums 1 between the transfer driving roller 24 and the tension roller 26 protrudes upward in the figure between the support roller 29b and the support roller 29c. The locus is such that the intermediate transfer belt 21 contacts only the photosensitive drum 1K.

Further, each of the photosensitive drums 1 of the image forming units 11Y, 11M, 11C, and 11K is opposed to the extended surface in the drawing of the intermediate transfer belt 21 that moves endlessly counterclockwise in the drawing. The image forming units 11 are arranged in the order of Y, M, C, and K from the upstream side in the endless movement direction. By arranging the image forming units 11 in this way, the toner images corresponding to the respective colors are superimposed on the intermediate transfer belt 21 from the photosensitive drums 1 on the intermediate transfer belt 21 during the full color printing operation. Next transfer is performed to form (carry) a full-color toner image.
On the other hand, during the monochrome printing operation, the toner image corresponding to black is primarily transferred onto the intermediate transfer belt 21 from the photosensitive drum 1K of the image forming unit 11K to form (carry) a monochrome toner image. At this time, the photosensitive drums 1 of the other image forming units 11Y, 11M, and 11C are separated from the intermediate transfer belt 21 as described above. For this reason, unnecessary endless movement of these photosensitive drums 1 can be stopped to extend their lifespan or reduce the power consumption of the image forming units 11Y, 11M, 11C.

The primary transfer roller 9 is an ion conductive roller (urethane + carbon dispersion, NBR, hydrin rubber) formed using a sponge roller having a diameter of 12 to 16 [mm] and adjusted to a resistance value of 10 ⁶ to 10 ⁸ [Ω]. ) Or an electronic conductive type roller (EPDM). Materials used for the intermediate transfer belt 21 include PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), TPE (thermoplastic elastomer), and carbon black. A resin film-like endless belt in which a conductive material such as the above is dispersed is used. In Examples described later, an intermediate transfer belt having a thickness of 90 to 160 [μm] and a width of 230 [mm] is used in a single-layer structure in which carbon black is added to TPE having a tensile modulus of 1000 to 2000 [Mpa]. . As electrical resistance, volume resistivity 10 ⁸ to 10 ¹¹ [Ω · cm] and surface resistivity 10 ⁸ to 10 ¹¹ [Ω / □] (both Mitsubishi) in an environment of 23 [° C.] 50 [%] RH. Measured with HirestaUP MCP-HT450 manufactured by Kagaku Co., Ltd., applied voltage 500 [V], applied time 10 [second]). The primary transfer roller 9 has been described above after the transfer of the toner image from the photosensitive drum 1 to the intermediate transfer belt 21 which is a transfer target provided in the transfer unit 20, and before the formation of the next electrostatic latent image. Along with the exposure means, it also functions as a static elimination means for neutralizing the surface of the photosensitive drum 1.

  The primary transfer unit 22 is a transfer member for performing primary transfer, and is used for primary transfer to the intermediate transfer belt 21 that is also a transfer target disposed opposite to the photosensitive drum 1 and the intermediate transfer belt 21. And a primary transfer roller 9 which is an application member for applying a primary transfer bias which is a voltage of the above. The primary transfer roller 9 is connected to a primary transfer high-voltage power supply 122 of FIG. 2 as one of power supply means, and a predetermined power is supplied to the intermediate transfer belt 21 by the power supplied from the primary transfer high-voltage power supply. A primary transfer bias (for example, a voltage in the range of +100 to +2000 [V]) is applied. Then, the surface of the intermediate transfer belt 21 facing the photosensitive drum 1 is charged to a positive polarity potential, and a transfer electric field is formed by a potential difference from the potential of the electrostatic latent image on the photosensitive drum 1 to form the photosensitive drum 1. The negative polarity toner image is primarily transferred to the intermediate transfer belt 21.

  The belt contact / separation mechanism 29 includes three support rollers 29a, 29b, 29c, a movable frame 29d, a holding frame 29e, an eccentric cam 29f serving as a track changing means for the intermediate transfer belt 21, a cam rotating shaft 29g, and an intermediate transfer contact / separation clutch. 29h and the like.

  The support rollers 29a, b, and c include a support roller 29a between the belt cleaning device 27 and the primary transfer roller 9Y, and a support roller 29b between the primary transfer roller 9C and the primary transfer roller 9K. A support roller 29 c is disposed between the tension rollers 26.

  The movable frame 29d is provided such that one end of the movable frame 29d is rotatable about the rotation shaft of the support roller 29c, and the rotation shafts of the support roller 29a, the primary transfer roller 9Y, the primary transfer roller 9M, and the primary transfer roller 9C. It consists of two side plates which hold | maintain freely from both sides.

  The holding frame 29e also serves as a holding frame for the transfer unit 20, and is mainly composed of two side plate members. The rotating body of the transfer unit 20 is rotatably held except for the support roller 29a, the primary transfer roller 9Y, the primary transfer roller 9M, and the primary transfer roller 9C that are rotatably held by the movable frame 29d. In addition, other components of the transfer unit 20 are also held.

  The secondary transfer unit 23 is disposed opposite to the transfer driving roller 24 via the intermediate transfer belt 21, the transfer driving roller 24, and the intermediate transfer belt 21, and the sheet P serving as a recording medium with the intermediate transfer belt 21. A secondary transfer roller 25 that is a secondary transfer member that sandwiches and conveys the toner.

As the transfer driving roller 24, polyurethane rubber (wall thickness: 0.3 to 1.0 [mm]), thin layer coating roller (wall thickness: 0.03 to 0.1 [mm]), or the like can be used. In this embodiment, a urethane coating roller (thickness: 0.05 [mm], φ19 [mm]) having a small diameter change due to temperature was used. The electric resistance value was set to 10 ⁶ [Ω] or less so as to be lower than that of the secondary transfer roller 25.

The secondary transfer roller 25 is a sponge roller having a diameter of 16 to 25 [mm], an ion conductive roller (urethane + carbon dispersion, NBR, hydrin) adjusted to a resistance value of 10 ⁶ to 10 ⁸ [Ω], and electronic conductivity. A type of roller (EPDM) or the like is used. If the resistance value of the secondary transfer roller 25 exceeds the above range, it becomes difficult for the current to flow. Therefore, in order to obtain the required transfer property, a higher voltage must be applied, resulting in an increase in power supply cost. Since it is necessary to apply a high voltage, discharge occurs in the gap before and after the nip of the transfer portion, and white spots are lost due to the discharge on the halftone image. This is remarkable in a low temperature and low humidity environment (for example, 10 [° C.], 15 [%] RH). On the other hand, if the resistance value of the secondary transfer roller 25 falls below the above range, the transferability between the multi-color image portion (for example, three-color superimposed image) and the single-color image portion existing on the same image cannot be achieved. This is because a sufficient current flows even at a relatively low voltage to transfer the monochrome image portion. Since a voltage value higher than the optimum voltage for the single color image portion is required to transfer the multi-color image portion, if the voltage is set so that the multi-color image portion can be transferred, the transfer current will be excessive for the single color image and transfer efficiency will be reduced. Because it invites. The resistance values of the primary transfer roller 9 and the secondary transfer roller 25 are measured with a roller installed on a conductive metal plate and a load of 4.9 [N] on one side is applied to both ends of the core metal. It was calculated from the value of the current that flows when a voltage of 1 [kV] was applied between the metal core and the metal plate.

  The secondary transfer roller 25 is connected to the secondary transfer high-voltage power supply 123 of FIG. 2 as one of power supply means, the transfer drive roller 24 is grounded, and the secondary transfer nip of the intermediate transfer belt 21 is connected. The surface potential at the part is in the vicinity of 0 [V]. Power is supplied from the secondary transfer high-voltage power supply to the secondary transfer unit 23 in accordance with the timing at which the toner image on the intermediate transfer belt 21 passes through the secondary transfer nip formed by the secondary transfer roller 25, and a predetermined value is obtained. The positive transfer secondary transfer bias is applied to the secondary transfer roller 25. In accordance with this timing, the registration roller pair 51 between the secondary transfer unit 23 and the paper feed unit 40 in the transport path 50 is rotated and the paper P fed from the paper feed unit 40 is fed to the secondary transfer nip. Transport to.

  The secondary transfer nip is nipped and conveyed by the potential difference between the surface potential of the secondary transfer roller 25 charged by the secondary transfer bias and the surface potential of the intermediate transfer belt 21 in the vicinity of 0 [V]. A secondary transfer electric field is formed between the sheet P and the intermediate transfer belt 21. By the secondary transfer electric field, the toner image on the intermediate transfer belt 21 is secondarily transferred onto the paper P at the secondary transfer nip portion.

  The belt cleaning device 27 is an intermediate transfer member cleaning member that removes a belt cleaning case that is not provided with a reference numeral, residual toner that has not been secondarily transferred to the surface of the intermediate transfer belt 21, and attached external additives. A belt cleaning blade 27a is provided. Further, a conveying coil 27c that conveys residual toner and the like, a conveying tube that connects the belt cleaning case and the waste toner container, and a metal cleaning facing roller 27b that faces the belt cleaning blade 27a via the intermediate transfer belt 21 are also provided. Have. The belt cleaning device 27 is disposed at a position where the cleaning counter roller 27b is closest to the downstream side in the moving direction of the intermediate transfer belt 21 of the transfer driving roller 24. The transport coil 27c passes through the transport tube, and rotates to transport residual toner and the like removed by the belt cleaning blade 27a into a waste toner container. The waste toner container is the same as that for storing the residual toner removed by the photoconductor cleaning device 7.

  The optical sensor 28 is disposed so as to face the intermediate transfer belt 21 stretched by the tension roller 26 from the outside. The optical sensor 28 is a sensor that is used for adjusting image density and alignment by measuring the amount of toner (toner image) that is primarily transferred onto the intermediate transfer belt 21 and the position of each color. This is a combination of diffuse reflection methods.

  The fixing unit 30 applies heat and pressure to the toner image secondarily transferred onto the paper P by the secondary transfer unit 23 of the transfer unit 20 and fixes the toner image onto the paper P. The fixing unit 30 is in contact with the side on which the toner image is secondarily transferred by the secondary transfer unit 23 to apply heat, and the fixing roller 31 is disposed opposite to the fixing roller 31 to form a fixing nip portion. A pressure roller 32 that applies pressure while nipping and conveying the paper P with the roller 31 is provided.

  The paper discharge unit 52 discharges the paper P on which the toner image has been fixed by applying heat and pressure at the fixing unit 30 from the inside of the apparatus main body 100 onto the stacking tray unit 71 formed on the top of the housing 101. Is. A paper discharge roller pair 54 is provided which holds and conveys the paper P from a paper discharge port 53 formed in the housing 101.

  The paper feed unit 40 stores a plurality of papers P, and a paper cassette 41 that can be attached to and detached from the apparatus main body 100 (paper feed unit 40), and the paper P stored in the paper cassette 41 in the transport path 50. A sheet feed roller 42 and a separation roller 43 that are supplied separately are provided. The conveyance path 50 conveys the paper P supplied from the paper supply unit 40 to the secondary transfer unit 23, the fixing unit 30, and the paper discharge unit 52 of the transfer unit 20. It has a registration roller pair 51 provided on the upstream side in the transport direction and a plurality of transport roller pairs.

  The paper P, which is a transfer material, is set in the paper cassette 41 or the manual feed slot, and at the timing when the leading edge of the toner image on the surface of the intermediate transfer belt 21 reaches the secondary transfer position by the paper feed roller 42, the registration roller pair 51, and the like. The paper is fed together. The toner image on the intermediate transfer belt 21 is transferred to the paper P by applying a predetermined secondary transfer bias by the secondary transfer high-voltage power source 123 of FIG. The paper feed takes a vertical path. The paper P is separated from the intermediate transfer belt 21 by the curvature of the secondary transfer roller 25, and the toner image transferred onto the paper P is fixed by the fixing unit 30 and then discharged from the paper discharge port 53. There are the following two types of transfer methods. That is, an attractive transfer system that forms a secondary transfer electric field by applying a positive bias as a secondary transfer bias to the secondary transfer roller 25 and grounding the transfer drive roller 24, and a negative polarity on the transfer drive roller 24. This is a repulsive transfer method in which a secondary transfer electric field is formed by applying a bias and grounding the secondary transfer roller 25. In this embodiment, an attractive transfer method is used, and a current of +5 to 100 [μA] is applied by constant current control as a transfer bias during paper feeding.

Further, the image forming process speed is changed depending on the type of paper P as the transfer material. Specifically, when paper P having a basis weight of 100 [g / m ² ] or more is used, the image forming process speed is set to a half speed, and a transfer material is formed in a fixing nip constituted by a pair of fixing rollers by a normal material. By passing the image processing speed twice as long as the image process speed, it is possible to secure the fixing property of the toner image.

  The main body control unit 110 controls the operation of each unit that is provided in the apparatus main body 100 and requires operation control, and the devices included in each unit. The main body control unit 110 will be described with reference to FIG.

  FIG. 2 is an explanatory diagram of the control system of the printer 200. As shown in FIG. 2, the main body control unit 110 includes a central processing unit (CPU) 111, a memory including a ROM 112 and a RAM 113, input / output I / O ports 114 and 115, and the like. The I / O port 114 is connected to the operation unit 116. The I / O port 115 includes a sheet position detection unit 117, a temperature / humidity sensor 118, a photoconductor drive motor 119, a belt drive motor 120, an intermediate transfer contact / separation clutch 121, a primary transfer high voltage power source 122, a secondary transfer high voltage power source 123, It is connected to a charging high-voltage power supply 124, a development high-voltage power supply 125, an LED array 126, and the like.

  The paper position detection unit 117 calculates the position of the paper P from the timing when the registration roller pair 51 of FIG. In addition, the temperature / humidity sensor 118 acquires environmental information in the apparatus main body 100. Further, as described above, the intermediate transfer contact / separation clutch 121 is arranged so that the photosensitive drums 1 and the intermediate transfer belt 21 included in the image forming units 11 of other colors are separated from each other when the monochrome image is formed. 21 trajectories are switched.

As described above, in this embodiment, the example in which the present invention is applied to the tandem-type intermediate transfer type printer 200 that uses the intermediate transfer belt 21 that is a belt-shaped intermediate transfer member has been described. The configuration is not limited. For example, the present invention can also be applied to a tandem direct transfer method using a transfer conveyance belt that is a belt-shaped transfer conveyance body, and a monochrome-compatible image forming apparatus that uses a rotating body such as a transfer roller as a transfer conveyance member.
Further, although the present invention has been described with respect to an example in which the present invention is applied to the printer 200 having the developing device 5 that uses a single component developer in each image forming unit 11, the present invention is limited to such a configuration. It is not a thing. For example, the present invention can be applied to an image forming apparatus having a developing device using a two-component developer in each image forming unit.

Next, a single color printing operation sequence of the conventional image forming apparatus will be described.
FIG. 3 is a timing chart showing a monochrome printing operation sequence of a conventional image forming apparatus. FIG. 4 is an enlarged schematic view of the image forming unit 11 and the transfer unit 20. The drive motor shown in FIG. 3 is a common drive source for the photosensitive drum 1 and the transfer drive roller 24 of the image forming unit 11.

  In the conventional image forming apparatus, when the printing operation is started, the driving motor starts to be driven, and the photosensitive member portion that is uniformly charged (−600 V) after passing through the charging point by the charging device 2 is developed by the developing device 5. During the period until the development point is reached, the photoconductor portion that is uniformly charged during the previous printing operation may pass through the development point.

  At this time, if the photoconductor portion passing through the development point remains in the uniformly charged state during the previous printing operation during this period, the toner does not move from the developing means to the photoconductor. However, when the printing operation is started after being left for a long time from the previous printing operation, the photosensitive member portion passing through the development point is at 0 V due to the potential attenuation. In this case, when the developing bias of the developing unit is applied, toner movement from the developing unit to the photoconductor occurs. As a result, wasteful toner consumption occurs.

  On the other hand, as a method of suppressing the generation of such wasteful toner consumption after being left for a long time from the previous printing operation, the photosensitive portion charged by the charging device 2 in the current printing operation is developed at the development point. There is a method in which the developing bias of the developing device 5 is not applied until it passes. However, with this method, when the printing operation is started within a short time after the end of the previous printing operation, the photosensitive member portion (−600 V) passing through the developing device 5 and the developing means (0 V) during the above period. In this case, a strong electric field that attracts the carrier charged to the positive polarity toward the photosensitive member is formed. Therefore, the problem of carrier adhesion may occur.

  Therefore, in the single color printing operation sequence of the conventional image forming apparatus, when the printing operation is finished, the photosensitive drum 1 is rotated once so that the entire circumference of the photosensitive body is neutralized by exposure before the drive motor is stopped. It is rotating too much. Specifically, for example, when a command for starting black monochrome printing is issued, the development bias and the charging bias in FIG. 3 start to be output at time t0 before the drive motor starts to be driven. The charging roller 2a of the charging device 2 of FIG. 1 is rotated with the rotation (endless movement) of the photosensitive drum 1, and has a negative polarity applied by the power supplied to the charging device 2 from the charging high-voltage power supply 124 of FIG. The surface of the photosensitive drum 1 is uniformly charged to a negative polarity potential by the charging bias. The surface of the developing roller 6 is charged to a positive polarity potential by a positive polarity developing bias applied to the developing roller 6 of the developing device 5 of FIG. 1 by the power supplied from the development high voltage power source 125 of FIG. The developing bias starts to be switched from a positive polarity output to a negative polarity output at time t3 when time T10 (= (L1 + L2) / V) has elapsed from time t2 when the driving of the driving motor is stabilized. From time t4, the surface of the developing roller 6 facing the photosensitive drum 1 is charged to a negative polarity potential. 4, L1 is the distance from the charging nip (charging point) to the exposure point, and L2 is the distance from the exposure point to the developing nip (developing point). V is the peripheral speed of the photosensitive drum 1. In FIG. 3, T1 is a time for which the output of the developing bias is stabilized, and T2 is a time for which the output of the charging bias is stabilized. T6 is L2 / V.

  The drive motor shown in FIG. 3 starts driving at time t1 when the longer one of the charging bias output stabilization time T1 and the development bias output stabilization time T2 is used as a trigger. The drive motor is stopped at time t9 when the exposure for static elimination by the exposure apparatus 3 in FIG. T3 in FIG. 3 is a time period from time t1 when the drive motor starts to be driven to time t2 when the rotation of the photosensitive drum 1 and the transfer drive roller 24 is stabilized. T7 is the time from the time t9 when the drive stop of the drive motor is started to the time t10 when the drive is stopped.

  The primary transfer bias shown in FIG. 3 is supplied from the primary transfer high-voltage power supply 122 shown in FIG. 2 to the primary transfer roller 9 at a time t4 when a predetermined time T4 elapses from a time t2 when the drive motor is stably driven. To start output (for example, +1000 [V]). The transfer bias output stop is started at time t9 when the exposure for the static elimination by the exposure apparatus 3 is completed. 3 is a time required for the rotation of the photosensitive drum 1 to reach the transfer nip of the primary transfer roller 9 from the charging point by the charging device 2.

  The secondary transfer bias shown in FIG. 3 is applied from the secondary transfer high-voltage power supply 123 in FIG. 2 to the secondary transfer roller at time t6 after time T5 has elapsed from the time t5 when printing exposure is started according to print data to be described later. 25 to start output of positive polarity. Thereafter, the output of the secondary transfer bias is stopped at time t7 when the printing exposure stops. 3 is a transfer nip of the primary transfer roller 9 where the photosensitive member portion that has passed the exposure point by the exposure means in the rotation of the photosensitive drum 1 in the direction of the arrow in FIG. 4 as indicated by the broken line in FIG. Is the sum of the time required to reach the transfer nip and the time required for the photoreceptor portion that has passed the transfer nip of the transfer nip of the primary transfer roller 9 to reach the transfer nip of the secondary transfer roller 25 in the rotation of the intermediate transfer belt 21. is there. The output stop timing of the secondary transfer bias can be implemented at the timing of static elimination exposure, and the leading edge / rear edge of the sheet of the sheet position detecting means 117 shown in FIG. It is also possible to carry out according to the passage detection timing.

  The exposure by the exposure apparatus 3 in FIG. 1 includes two types of exposure, that is, printing exposure according to print data and static elimination exposure for neutralizing the surface of the photosensitive drum 1 in FIG. The exposure is the same as in the case. The time for performing the static elimination exposure is a time T20 corresponding to the neutralization of the entire surface of the photosensitive drum 1, and this time T20 can be expressed as L3 / V. L3 is the circumferential length of the photosensitive drum 1, and V is the circumferential speed of the photosensitive drum 1. At the end of the printing operation, the photosensitive drum 1 is moved endlessly by one turn by driving the drive motor, and the charge is eliminated by exposure, so that the entire surface of the photoreceptor is discharged. As a result, when the next printing operation is started, the photosensitive member portion that passes through the developing point by the developing device 5 during the period until the uniformly charged photosensitive member portion reaches the developing point by the developing device 5. Is in a state where the charge has been removed, and toner adhesion and carrier adhesion to the photoreceptor portion can be suppressed.

  There is no problem with the start timing of the static elimination exposure of the photoconductor drum 1 as long as the photoconductor drum 1 is moved endlessly around one turn when the drive motor is stopped, so it is not necessary to match the output OFF timing of the secondary transfer bias. For example, exposure for neutralization of the photosensitive drum 1 is started during the secondary transfer bias output. Driven by a period until the photosensitive member portion that has passed through the exposure point by the exposure device 3 reaches the exposure point again, that is, at the timing when the neutralization of the entire surface of the photosensitive drum 1 is completed by moving the photosensitive drum 1 endlessly for one round. What is necessary is just to start a motor stop. The timing for starting to stop the drive motor is as follows. This is the case after the toner remaining on the transfer belt after the secondary transfer is removed by the photoconductor cleaning blade 8 which is a cleaning member of the photoconductor cleaning device 7 of FIG. If the driving means for the photosensitive drum 1 and the transfer driving roller 24 in FIG. 1 also serves as the driving means for the fixing unit 40, the rear end of the transfer material is formed by the fixing roller 31 and the pressure roller 32 of the fixing unit 30. This is a case where the drive can only be stopped after passing through the fixing nip.

Next, a full color printing operation sequence of a conventional image forming apparatus will be described.
FIG. 5 is a timing chart showing a full color printing operation sequence of the conventional image forming apparatus.
As an operation different from the single color printing operation sequence shown in FIG. 3, the time T8 shown in FIG. 5 is shifted for each color at time t5 to time 8 which is the timing of exposure for printing by the exposure means corresponding to the print data. Thus, the toner images of the respective colors are superimposed on the intermediate transfer belt 21 shown in FIG. Then, during the secondary transfer bias output, exposure for static elimination of each photosensitive drum 1 of the image forming units 11Y, 11M, 11C, 11K is started. The entire surface of each photoconductive drum 1 is neutralized by moving the photoconductive drum 1 endlessly more than once so that the photoconductive portion that has passed the exposure position by the exposure means reaches the exposure location again. T8 in FIG. 5 is the time required for a certain position of the intermediate transfer belt 21 to rotate and move between the primary transfer nips of adjacent image forming units (for example, 80 [mm]).

  As described above, in the conventional static elimination process of the photoconductor in the image forming apparatus, the entire surface of the photoconductor drum is exposed by moving the photoconductor drum endlessly once at the end of the printing operation. Therefore, the photosensitive drum is rotated by an extra one turn. As a result, there arises a problem that the life of the driving means is shortened. As a method for solving this problem, a method for neutralizing a latent image carrier according to this embodiment is proposed below.

Next, a monochrome printing operation sequence of the image forming apparatus according to the present embodiment will be described.
FIG. 6 is a timing chart showing a monochrome printing operation sequence of the image forming apparatus according to the present embodiment. FIG. 7 is a schematic diagram for explaining the charge removal processing of the photosensitive drum according to the present embodiment.
In the single color printing operation sequence in the image forming apparatus of the present embodiment shown in FIG. 6, when the printing operation is finished, as shown in FIG. After the exposure device 3 exposes the photosensitive member portion that is positioned between the development point by the developing device 5, the drive motor is stopped. As a result, the photosensitive member portion in the region from the exposure point to the development point (the region indicated by the range A in FIG. 7A) is in a neutralized state. At the time of starting the printing operation, exposure is performed after the photosensitive member portion located at the charging point by the charging device 2 before driving the driving motor drives the driving motor at time t1 when the driving motor starts to be driven. The exposure device 3 exposes the photosensitive member until the exposure point by the device 3 is reached. As a result, the photosensitive member portion in the region from the charging point to the exposure point (the region indicated by the range B in FIG. 7B) is in a neutralized state. At the same time as the charge removal, the region of the photoreceptor portion that has passed through the charging device 2 (the region indicated by the range C in FIG. 7B) is uniformly charged.

  Specifically, when starting the printing operation, driving of the drive motor is started and exposure is performed at time t1, which is a timing triggered by the longer one of the charging bias output stabilization time T1 and the development bias output stabilization time T2. The device 3 is turned on. The exposure for static elimination is stopped at time t3 when L1 / V (= T30) time has elapsed from time t2 when the drive of the drive motor is stabilized. As a result, exposure is performed by the exposure device 3 for a period until the portion of the photoreceptor that has passed the charging point by the charging device 2 reaches the exposure point by the exposure device 3. As a result, the photosensitive member portion in the region from the charging point to the exposure point by the charging device 2 (the region indicated by the range B in FIG. 7B) is neutralized. Although the timing at which the exposure apparatus 3 is turned on is the time t1 when the drive motor starts to be driven, it may be the time t2 when the drive motor is stabilized. When the neutralizing exposure is performed before the printing operation is started and the monochrome printing operation is completed, the neutralizing exposure is started at time t8 of the output OFF timing of the secondary transfer bias. The static elimination exposure is stopped at time t10 when L2 / V (= T40) time elapses from time t8. As a result, the area from the exposure point to the development point (the middle range in FIG. 7A) is exposed by the exposure device 3 during the period until the photosensitive member portion that has passed the exposure point reaches the development point by the development device 5. The photosensitive member portion in the region (A) is in a static-removed state.

Next, a full color printing operation sequence of the image forming apparatus according to the present embodiment will be described.
FIG. 8 is a timing chart showing a full-color printing operation sequence of the image forming apparatus of this embodiment. In the full-color printing operation sequence in the image forming apparatus of this embodiment shown in FIG. 8, the exposure apparatus 3 is turned on at time t2 when the drive motor is stabilized in each image forming unit. Thereafter, the static elimination exposure is stopped at time t3 when L1 / V (= T30) time elapses, in which the photosensitive member portion that has passed the charging point by the charging device 2 reaches the exposure point from the charging point. As a result, the exposure device is exposed on the photosensitive member until the photosensitive member portion located at the charging point by the charging device 2 before driving the driving motor reaches the exposure point by the exposure device 3 after driving the driving motor. 3 to expose. As a result, each photosensitive member portion in the region from the charging point to the exposure point (the region indicated by the range B in FIG. 7B) is in a neutralized state. After the exposure for static elimination before the start of driving of the drive motor is performed, the exposure for static elimination is started at time t11 of the output OFF timing of the secondary transfer bias when the full color printing operation is finished. The static elimination exposure is stopped at time t13 when L2 / V (= T40) time elapses from time t11. As a result, after the exposure device 3 exposes the photosensitive member portion that is located between the exposure point by the exposure device 3 and the development point by the development device 5 when the drive motor is stopped, the drive motor is driven. To stop. As a result, each photosensitive member portion in the region from the exposure point to the development point (the region indicated by the range A in FIG. 7A) is in a neutralized state.

  As described above, according to the present embodiment, when the printing operation is started, the photosensitive member portion located between the exposure point and the development point before driving the drive motor is used when the previous printing operation ends. Is in a state of being neutralized. When starting the printing operation, the photosensitive member portion located between the charging point and the exposure point before driving the driving motor is exposed by the exposure device by driving the driving motor at the start of the current printing operation. As a result, the static electricity is removed. When starting the printing operation, the photosensitive member portion located upstream of the charging point in the rotation direction of the photosensitive member before driving the drive motor was uniformly charged by the charging device at the start of the current printing operation. Can be in a state. As a result, at the start of the printing operation, all the photosensitive member parts passing through the development point were discharged during the period until the photosensitive member portion that was uniformly charged by the charging device at the time of the printing operation reached the development point. Can be in a state. At the end of the printing operation, the moving distance that is necessary to rotate the photoconductor to neutralize the photoconductor is the moving distance between the exposure point and the development point. For this reason, the driving time of the driving motor can be shortened and the life of the driving motor can be shortened as compared with the conventional image forming apparatus in which the photosensitive drum is rotated more than one turn to neutralize the photosensitive drum at the end of the printing operation. Can be extended. Specifically, when one sheet per job is full color and A4 size paper is passed horizontally, the rotation distance of the conventional image forming unit is 1200 [mm], from the charging nip of the charging device 2 to the developing nip of the developing device 5 The distance of the area section is 21.4 [mm], and the circumference of the photosensitive drum 1 is 96 [mm]. The rotation distance of the image forming unit when the charge removal process of this embodiment is performed is 1200− (96−21.4) [mm]. It was possible to save about 7% as the rotation distance of the image forming unit.

Next, the toner used in the image forming apparatus of this embodiment will be described.
[Synthesis of Polyester 1]
In a reaction vessel equipped with a condenser, a stirrer and a nitrogen inlet tube, 235 parts of bisphenol A ethylene oxide 2-mole adduct, 525 parts of bisphenol A propylene oxide 3-mole adduct, 205 parts of terephthalic acid, 47 parts of adipic acid and dibutyl 2 parts of tin oxide was added, reacted at normal pressure 230 [° C.] for 8 hours, and further reacted at a reduced pressure of 10 to 15 [mmHg] for 5 hours. Then, 46 parts of trimellitic anhydride was added to the reaction vessel, and 180 [ [Polyester 1] was obtained by reacting at room temperature for 2 hours. [Polyester 1] had a number average molecular weight of 2600, a weight average molecular weight of 6900, Tg of 44 [° C.], and an acid value of 26.

[Synthesis of Prepolymer 1]
In a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, 682 parts of bisphenol A ethylene oxide 2-mole adduct, 81 parts of bisphenol A propylene oxide 2-mole adduct, 283 parts of terephthalic acid, trimellitic anhydride 22 And 2 parts of dibutyltin oxide were added, reacted at 230 ° C. under normal pressure for 8 hours, and further reacted under reduced pressure of 10-15 [mmHg] for 5 hours to obtain [Intermediate Polyester 1]. [Intermediate Polyester 1] had a number average molecular weight of 2,100, a weight average molecular weight of 9,500, Tg of 55 [° C.], an acid value of 0.5, and a hydroxyl value of 49.
Next, 411 parts of [Intermediate polyester 1], 89 parts of isophorone diisocyanate, and 500 parts of ethyl acetate are placed in a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, and reacted at 100 [° C.] for 5 hours. [Prepolymer 1] was obtained. [Prepolymer 1] had a free isocyanate weight% of 1.53 [%].

[Create master batch 1]
Carbon black (Regal 400R manufactured by Cabot Corporation): 40 parts, Binder resin: Polyester resin (Sanyo Kasei RS-801 Acid value 10, Mw 20000, Tg 64 [° C.]): 60 parts, Water: 30 parts are mixed in a Henschel mixer. Thus, a mixture in which water was soaked into the pigment aggregate was obtained. This was kneaded for 45 minutes with two rolls set at a roll surface temperature of 130 [° C.] and pulverized to a size of 1 [mm] with a pulverizer to obtain [Masterbatch 1].

[Preparation of Pigment / WAX Dispersion 1 (Oil Phase)]
545 parts of [Polyester 1], 181 parts of paraffin wax, and 1450 parts of ethyl acetate are charged in a container equipped with a stirring bar and a thermometer, heated to 80 [° C.] under stirring, and maintained at 80 [° C.] for 5 hours. Then, it was cooled to 30 [° C.] in 1 hour. Next, 500 parts of [Masterbatch 1], 100 parts of charge control agent (1) and 100 parts of ethyl acetate were charged in a container and mixed for 1 hour to obtain [Raw material solution 1].
[Raw material solution 1]
1500 parts were transferred to a container, and using a bead mill (Ultra Visco Mill, manufactured by Imex), liquid feeding speed 1 [kg / hr], disk peripheral speed 6 [m / sec], 0.5 [mm] zirconia beads Carbon black and WAX were dispersed under the conditions of 80% by volume filling and 3 passes. Next, 425 parts and 230 parts of [Polyester 1] were added, and one pass was performed with a bead mill under the above conditions to obtain [Pigment / WAX Dispersion 1]. It was adjusted by adding so that the solid content concentration of [Pigment / WAX Dispersion 1] (130 [° C.], 30 minutes) was 50 [%].

[Water phase creation process]
Ion-exchanged water 970 parts, 25 [wt%] aqueous dispersion 40 parts of organic resin fine particles for dispersion stabilization (styrene copolymer of styrene-methacrylic acid-butyl acrylate-methacrylic acid ethylene oxide adduct sulfate) , 140 parts and 90 parts of a 48.5 [%] aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7: manufactured by Sanyo Chemical Industries) were mixed and stirred to obtain a milky white liquid. This is designated as [Aqueous Phase 1].

[Emulsification process]
[Pigment / WAX Dispersion 1] 975 parts, 2.6 parts of isophoronediamine as amines, TK homomixer (manufactured by Tokushu Kika) at 5,000 [rpm] for 1 minute, [Prepolymer 1] Add 88 parts and mix for 1 minute at 5,000 [rpm] with a TK homomixer (manufactured by Tokushu Kika), add 1200 parts of [Aqueous Phase 1], and rotate at 8,000 to 13 with a TK homomixer. The mixture was mixed for 20 minutes while adjusting at 1,000 [rpm] to obtain [Emulsified slurry 1].

[Desolvation process]
[Emulsion slurry 1] was charged into a container equipped with a stirrer and a thermometer, and the solvent was removed at 30 [° C.] for 8 hours to obtain [Dispersion slurry 1].

[Washing and drying process]
[Dispersion Slurry 1] After filtering 100 parts under reduced pressure,
(1): 100 parts of ion-exchanged water was added to the filter cake, mixed with a TK homomixer (at 12,000 rpm for 10 minutes), and then filtered. The filtrate at this time was milky white.
(2): 900 parts of ion exchange water is added to the filter cake of (1) above, ultrasonic vibration is applied, and the mixture is mixed with a TK homomixer (30 minutes at a rotation speed of 12,000 [rpm]), and then filtered under reduced pressure. did. This operation was repeated so that the electric conductivity of the reslurry liquid was 10 [μC / cm] or less.
(3): 10% hydrochloric acid was added so that the reslurry liquid of the above (2) had a pH of 4, and the mixture was filtered as it was with a three-one motor for 30 minutes.
(4): 100 parts of ion-exchanged water was added to the filter cake of (3) above, mixed with a TK homomixer (at a rotation speed of 12,000 [rpm] for 10 minutes), and then filtered. This operation was repeated so that the reslurry liquid had an electric conductivity of 10 [μC / cm] or less to obtain [Filter Cake 1]. [Filtration cake 1] was dried at 42 ° C. for 48 hours in a circulating drier, and sieved with an opening of 75 μm mesh to obtain [Mother toner 101]. The average circularity is 0.974, the volume average particle diameter (Dv) is 6.3 [μm], the number average particle diameter (Dp) is 5.3 [μm], and Dv / Dp is 1.19. A toner base having a distribution was obtained.

  For 100 parts of the toner base obtained by the above preparation method, 1 part of commercially available silica fine powder H20TM (manufactured by Clariant Japan; average primary particle size 12 [nm], no silicone oil treatment), RY50 [manufactured by Nippon Aerosil Co., Ltd.] ; Average primary particle size 40 [nm], with silicone oil treatment] 2 parts are mixed with a Henschel mixer, and the coarse particles and aggregates are removed by passing through a sieve with an opening of 60 [μm], thereby removing toner. Obtained.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A latent image carrier such as the photosensitive drum 1; a charging means such as a charging device 2 for uniformly charging the surface of the latent image carrier; and a surface of the uniformly charged latent image carrier to be exposed to electrostatic latent image. An exposure unit such as an exposure device 3 that forms an image, a developing unit such as a developing device 5 that develops an electrostatic latent image formed on the latent image carrier as a toner image with a developer, and an endless latent image carrier In an image forming apparatus including a driving unit such as a photosensitive member driving motor 119 to be moved, when the driving of the driving unit is stopped, the exposure point by the exposure unit and the development point by the developing unit are stopped when the driving unit is stopped. After exposing the latent image carrier portion to be positioned between the exposure means, the drive means is stopped, and when starting the image forming operation, the drive means is started and then the drive is started. Before starting, Latent image carrier portion, until it reaches the exposure point by the exposure means to expose the upper latent image carrier by the exposure means.
According to this, as described in the above embodiment, when the image forming operation ends, the latent image carrier portion that is located between the exposure point and the development point when the driving unit is stopped is exposed to the exposure unit. After the exposure, the driving of the driving means is stopped. On the other hand, when the image forming operation is started, the latent image carrier is located until the portion of the latent image carrier located at the charging point before driving the driving unit reaches the exposure point after driving the driving unit. The body is exposed by exposure means. According to this aspect, when starting the image forming operation, the latent image carrier portion positioned between the exposure point and the developing point before driving the driving unit is used when the previous image forming operation ends. It is in a state where it has been neutralized. In addition, when starting the image forming operation, the latent image carrier portion located between the charging point and the exposure point before driving the driving unit drives the driving unit at the start of the current image forming operation. And it will be in the state discharged by exposing by the exposure means. When the image forming operation is started, the latent image carrier portion located upstream of the charging point upstream in the endless movement direction of the latent image carrier before driving the driving unit is used when the current image forming operation is started. It can be made to be uniformly charged by the charging means. As a result, at the start of the image forming operation, the latent image carrier that passes through the development point for a period until the latent image carrier portion that is uniformly charged by the charging means during the image forming operation reaches the development point. All the parts can be in a static-removed state.
Further, according to this aspect, at the end of the image forming operation, the latent image carrier portion that is located between the exposure point and the development point when the driving unit is stopped is discharged in order to discharge the latent image by the exposure unit. The endless movement distance that requires the endless movement of the image carrier is the endless movement distance between the exposure point and the development point. Therefore, the driving time of the driving means can be shortened as compared with the conventional image forming apparatus in which the latent image carrier is moved endlessly for one round to neutralize the latent image carrier at the end of the image forming operation, It is possible to extend the life of the driving means.
At the start of the image forming operation, driving of the driving means for exposing and neutralizing the exposure by the exposure means is performed to uniformly charge the latent image carrier passing through the charging point by the charging means. It is the drive performed simultaneously with the drive of a means. Since this drive does not endlessly move the latent image carrier, the drive time of the drive means does not increase.

(Aspect B)
In (Aspect A), the light source of the exposure means is an LED. According to this, as described in the above embodiment, it is possible to reduce the size by using the LED as the light source of the exposure means.

(Aspect C)
In (Aspect A), the light source of the exposure means is a laser diode. According to this, as described in the above embodiment, the cost can be suppressed by using the laser diode as the light source of the exposure means.

(Aspect D)
A latent image carrier such as the photosensitive drum 1; a charging means such as a charging device 2 for uniformly charging the surface of the latent image carrier; and a surface of the uniformly charged latent image carrier to be exposed to electrostatic latent image. An exposure unit such as an exposure unit 3 that forms an image; a developing unit such as a development unit 5 that develops an electrostatic latent image formed on the latent image carrier as a toner image with a developer; A transfer means such as a primary transfer roller 9 for transferring a developed toner image from the latent image carrier to the transfer medium by a transfer electric field formed between the transfer belt 21 and the transfer object; and the latent image carrier. In a method for neutralizing a latent image carrier used in an image forming apparatus including a driving unit such as a photoconductor driving motor 119 that moves the endlessly, an exposure unit when driving of the driving unit is stopped when the image forming operation is finished. Located between the exposure point by and the development point by the developing means After the latent image carrier portion is exposed by the exposure means, the driving means is stopped, and when the image forming operation is started, the driving means is started and then the charging means is started before the driving is started. The latent image carrier is exposed by the exposure unit until the portion of the latent image carrier that has been located at the charging point is reached by the exposure unit.
According to this, as described in the above embodiment, when the image forming operation is started, the latent image carrier portion located between the exposure point and the development point before driving the driving unit is When the image forming operation is completed, the charge is removed. In addition, when starting the image forming operation, the latent image carrier portion located between the charging point and the exposure point before driving the driving unit drives the driving unit at the start of the current image forming operation. And it will be in the state discharged by exposing by the exposure means. When the image forming operation is started, the latent image carrier portion located upstream of the charging point upstream in the endless movement direction of the latent image carrier before driving the driving unit is used when the current image forming operation is started. It can be made to be uniformly charged by the charging means. As a result, at the start of the image forming operation, the latent image carrier that passes through the development point for a period until the latent image carrier portion that is uniformly charged by the charging means during the image forming operation reaches the development point. All the parts can be in a static-removed state.
Further, according to this aspect, at the end of the image forming operation, the latent image carrier portion that is located between the exposure point and the development point when the driving unit is stopped is discharged in order to discharge the latent image by the exposure unit. The endless movement distance that requires the endless movement of the image carrier is the endless movement distance between the exposure point and the development point. Therefore, the driving time of the driving means can be shortened as compared with the conventional image forming apparatus in which the latent image carrier is moved endlessly for one round to neutralize the latent image carrier at the end of the image forming operation, It is possible to extend the life of the driving means. At the start of the image forming operation, driving of the driving means for exposing and neutralizing the exposure by the exposure means is performed to uniformly charge the latent image carrier passing through the charging point by the charging means. It is the drive performed simultaneously with the drive of a means. For this reason, this driving does not endlessly move the latent image carrier, so that the driving time of the driving means does not increase.

DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging device 2a Charging roller 3 Exposure device 4 Toner supply container 5 Developing device 6 Developing roller 7 Photoconductor cleaning device 8 Photoconductor cleaning blade 9 Primary transfer roller 10 Image forming unit 11 Image forming unit 20 Transfer unit 21 Intermediate transfer belt 22 Primary transfer unit 23 Secondary transfer unit 24 Transfer drive roller 25 Secondary transfer roller 26 Tension roller 27 Belt cleaning device 27a Belt cleaning blade 27b Cleaning counter roller 27c Conveying coil 28 Optical sensor 29a Support roller 29b Support roller 29c Support roller 30 Fixing unit 31 Fixing roller 32 Pressure roller 40 Paper feeding unit 41 Paper cassette 42 Paper feeding roller 43 Separating roller 50 Transport path 51 Registration roller pair 52 Paper ejection unit 53 Paper ejection port 54 Paper ejection roller pair 71 Stacking tray unit 10 0 apparatus main body 101 casing 110 main body control unit 111 central processing unit (CPU)
112 ROM
113 RAM
114 I / O port 115 I / O port 116 Operation unit 117 Paper position detection means 118 Temperature / humidity sensor 119 Photoconductor drive motor 120 Belt drive motor 121 Intermediate transfer contact / separation clutch 122 Primary transfer high-voltage power supply 123 Secondary transfer high-voltage power supply 124 Charge high voltage power supply 125 Development high voltage power supply 126 LED array

Japanese Patent No. 3457083

Claims (4)

A latent image carrier, a charging means for uniformly charging the surface of the latent image carrier, an exposure means for exposing the uniformly charged surface of the latent image carrier to form an electrostatic latent image, and the latent image carrier. An image forming apparatus comprising: a developing unit that develops an electrostatic latent image formed on an image carrier as a toner image with a developer; and a driving unit that moves the latent image carrier endlessly.
At the end of the image forming operation, the latent image carrier portion that is located between the exposure point by the exposure unit and the development point by the developing unit when the driving of the driving unit is stopped is the exposure unit. After the exposure, the driving unit is stopped, and when the image forming operation starts, the driving unit starts driving and is positioned at a charging point by the charging unit before starting the driving. An image forming apparatus in which the latent image carrier is exposed by the exposure unit until the latent image carrier part reaches the exposure point by the exposure unit. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the light source of the exposure means is an LED. The image forming apparatus according to claim 1.
The light source of the exposure means is a laser diode. A latent image carrier, a charging means for uniformly charging the surface of the latent image carrier, an exposure means for exposing the uniformly charged surface of the latent image carrier to form an electrostatic latent image, and the latent image carrier. Discharging the latent image carrier used in an image forming apparatus comprising: a developing unit that develops the electrostatic latent image formed on the image carrier as a toner image with a developer; and a driving unit that moves the latent image carrier endlessly. In the method
At the end of the image forming operation, the latent image carrier portion that is located between the exposure point by the exposure unit and the development point by the developing unit when the driving of the driving unit is stopped is the exposure unit. After the exposure, the driving unit is stopped, and when the image forming operation starts, the driving unit starts driving and is positioned at a charging point by the charging unit before starting the driving. A method of neutralizing a latent image carrier, wherein the latent image carrier is exposed by the exposure unit until the latent image carrier part reaches the exposure point by the exposure unit.

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