JP4944595B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus introducing a transfer system to transfer a toner image formed on the surface of an image carrier 2 to a recording medium 5c, then, obtain an image formation object, wherein such a failure is suppressed that toner-scattering occurs before a toner image formed on an image carrier is transferred, without making the image forming apparatus large in size. <P>SOLUTION: Such a digital photoreceptor drum is used as an image carrier 2, that is an exposure source/latent image formation integrated type digital photoreceptor drum including a light emitting element matrix layer and a photoreceptor layer layered on the light emitting element matrix layer, and charged by a charging means. At a pre-transfer exposure, the light emitting pixel portion of the light emitting element matrix layer corresponding to the non-image formation part of the photoreceptor layer is made to emit light, and at least the non-image formation part on the photoreceptor layer is exposed several times or continuously, related to the same area. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus that forms an image using an electrophotographic system, such as a printer, a copier, and a facsimile machine.

  More specifically, the present invention relates to a transfer type image forming apparatus that obtains an image formed product by transferring a developer image formed on the surface of an image carrier onto a recording medium (recording material (transfer material, printing paper, etc.), intermediate transfer body). Is.

  Conventionally, in a transfer type image forming apparatus, as a transfer means for transferring a developer image (hereinafter referred to as a toner image) formed on the surface of an image carrier to a recording material, a corona transfer method, a roller transfer method, a belt transfer System and intermediate transfer body system.

  The corona transfer system is a system in which a charge having a characteristic opposite to the charging polarity of the toner is applied to the back surface of the recording material by a corona charger.

  The roller transfer system is a system in which an electric field is formed by pressing a conductive rubber roller to which a voltage is applied from the back surface of a recording material, or a dielectric roller having a dielectric film provided on the surface of the conductive rubber roller.

  The belt transfer system is a system in which a conductor or dielectric endless belt has both functions of conveying a recording material and forming an electrostatic field.

  In the intermediate transfer body method, the toner image formed on the surface of the image carrier is temporarily transferred to the intermediate transfer body (primary transfer). Then, the toner image on the intermediate transfer member is collectively transferred again onto the recording material (secondary transfer). In general, by performing the primary transfer a plurality of times, a toner image of a plurality of colors is formed on the intermediate transfer member, and the four-color toners are collectively transferred to the recording material by the secondary transfer. In addition, after superposing a plurality of colors on the image carrier (multiple development), the multiple development toner images may be collectively transferred onto the intermediate transfer member.

  In any transfer method, the transfer device forms a strong electric field between the recording material and the image carrier at the transfer position, and transfers the toner image on the image carrier to the recording material by electrostatic force. Have Further, it has a charge supplying function of supplying toner holding charge for holding the toner image on the recording material until the recording material is separated from the image carrier and fixed as a fixed image in the fixing device. .

  In various transfer systems, the surface of the image carrier is exposed (pre-transfer exposure) on the upstream side (before transfer) of the image carrier rotation direction from the position where the toner image on the image carrier is transferred to the recording medium. There is. It is known that such transfer pre-exposure enables stable transfer with a low transfer voltage (Non-Patent Document 1).

  However, according to the study by the present inventors, it is found that when pre-transfer exposure is performed, if the surface potential is lowered to approximately 0 V in one exposure (see Patent Document 1), the toner on the photoreceptor is scattered. ing.

  Conventionally, this is due to the fact that when pre-transfer exposure is performed, the toner blocks the exposure of the image bearing member to the surface of the photoreceptor, and a potential difference occurs in the direction in which the toner scatters between the image area and the non-image area. It is believed that. This will be described with reference to FIG.

That is, after the image carrier is uniformly charged to the potential V _d1 , the image portion on which the toner image is to be formed is exposed to E, and the potential is lowered to V _S to form an electrostatic latent image ((a in FIG. 18). )). Next, reversal development is performed using the toner T charged to the same polarity as the image carrier, and the toner particles T are adhered to the V _S portion to form a toner image (FIG. 18B). The toner image has a potential V _t with toner holdings charge. Next, pre-transfer exposure P is performed on the image bearing member carrying the toner image. By this exposure, the non-image portion potential is lowered to _Vd2 . On the other hand, the image portion potential is not lowered because the exposure P is shielded by the toner particles T in the image portion, and the toner holding charge remains even after the exposure, so that the image portion potential V _t becomes the non-image portion potential V. _It becomes higher than _d2 ((c) of FIG. 18). Therefore, a potential difference is generated at the boundary between the non-image area and the image area, and the toner image scatters d due to the electric attraction based on the potential difference.

  Therefore, there are a configuration in which pre-transfer exposure is performed with infrared light (see Patent Document 2) and a configuration in which pre-transfer exposure is performed from the back side (back side) of the image carrier (see Patent Document 3).

  FIG. 19 shows a diagram cited from Patent Document 2 regarding the surface potential of the image carrier after the pre-transfer exposure with infrared light. The PTL shown in FIG. 19 is pre-transfer exposure. The left side of FIG. 19 describes changes in the surface potential of the image carrier when exposure is performed with red light, which is conventionally performed. On the right side, the change in the surface potential of the image carrier when infrared light is used is written. FIG. 19 shows the state before the pre-transfer exposure and the lower portion after the pre-transfer exposure. Thus, it is described that when infrared light is used, there is no potential difference between the image portion and the non-image portion in order to transmit the toner image.

The configuration of Patent Document 3 in which pre-transfer exposure is performed from the back surface of the image carrier will be described with reference to FIG. In FIG. 20, 120C is a pre-transfer exposure, 11 is a charger, 12 is an exposure optical system, 13 is a developing device, 14 is an intermediate transfer belt, and 10 is a transparent photoreceptor having a photosensitive layer on a transparent substrate. With such a configuration, pre-transfer exposure can be performed from the back surface of the photosensitive layer using the pre-transfer exposure apparatus 120C. As a result, since there is no shielding by toner as in the case of infrared light, the potential difference between the image portion and the non-image portion can be eliminated.
“The Basics and Applications of Electrophotographic Technology” by the Electrophotographic Society, published by Corona, June 20, 1997, p. 190 JP-A-5-165383 JP-A-8-137165 Japanese Patent Laid-Open No. 11-316489

  However, even if these configurations are used, it has been found that toner scattering occurs on the image carrier due to a sudden change in surface potential caused by a single exposure. In addition, since a separate pre-exposure device is required, the size of the device increases.

  SUMMARY An advantage of some aspects of the invention is to suppress scattering of a toner image on an image carrier before transfer without increasing the size of the apparatus.

A typical configuration of the image forming apparatus according to the present invention for achieving the above object is as follows:
A rotatable image carrier, a charging means for charging the image carrier, a developing means for developing an electrostatic latent image formed on the image carrier as a developer image, and the developer image as a transfer medium In an image forming apparatus having a transfer means for transferring and a control means,
The image carrier has a light emitting element matrix layer, and a photosensitive layer laminated on the light emitting element matrix layer and charged by the charging means,
The control means forms an electrostatic latent image on the charged surface of the photosensitive layer by causing each light emitting pixel portion of the light emitting element matrix layer to emit light corresponding to image data and exposing the photosensitive layer. Light emission corresponding to at least a non-image forming portion of the photosensitive layer between a latent image forming sequence and an image carrier rotating direction downstream from the developing unit and an image carrier rotating direction upstream from the transfer unit. And a pre-transfer exposure sequence in which the light emitting pixel portion of the element matrix layer portion is caused to emit light and is exposed a plurality of times in the same region as the at least non-image forming portion of the photosensitive layer.

Another typical configuration of the image forming apparatus according to the present invention for achieving the above object is as follows:
A rotatable image carrier, a charging means for charging the image carrier, a developing means for developing an electrostatic latent image formed on the image carrier as a developer image, and the developer image as a transfer medium In an image forming apparatus having a transfer means for transferring and a control means,
The image carrier has a light emitting element matrix layer, and a photosensitive layer laminated on the light emitting element matrix layer and charged by the charging means,
The control means forms an electrostatic latent image on the charged surface of the photosensitive layer by causing each light emitting pixel portion of the light emitting element matrix layer to emit light corresponding to image data and exposing the photosensitive layer. Light emission corresponding to at least a non-image forming portion of the photosensitive layer between a latent image forming sequence and an image carrier rotating direction downstream from the developing unit and an image carrier rotating direction upstream from the transfer unit. And a pre-transfer exposure sequence in which the light emitting pixel portion of the element matrix layer portion emits light to continuously expose at least the same area as the non-image forming portion of the photosensitive layer.

  According to the present invention, scattering of the developer image on the image carrier before transfer can be suppressed without increasing the size of the apparatus.

(1) Image Forming Unit FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus A in this embodiment. FIG. 2 is a partially enlarged view of FIG.

  The image forming apparatus A of this embodiment is a full-color digital electrophotographic printer of 1 drum-multiple developing system-intermediate transfer system.

  This printer A is a sheet-shaped recording material that can be used to print a full-color image or a mono-color image corresponding to electrical image data (image information signal) input from an external device C connected to a main body control circuit section B as a control means. It can be formed on the surface and output (printed out).

  The external device (host device) C is a personal computer, an image reader, a facsimile, or the like.

  The main body control circuit unit (controller) B exchanges various electrical information signals with the external device C. It also handles electrical information signals input from image forming process devices and sensors, command signals to image forming process devices, etc., and predetermined image forming sequence control. Operation control of the entire printer is executed in accordance with a control program or a reference table stored in the ROM or RAM.

This printer A has a rotating drum type electrophotographic photosensitive member 2 (rotatable image carrier) as an image carrier . The electrophotographic photoreceptor 2 is an exposure source-latent image forming integrated digital photoreceptor drum in which a photoreceptor layer is laminated on a light emitting element matrix layer. This digital photosensitive drum will be described later. A digital photosensitive drum (hereinafter abbreviated as “drum”) 2 is rotationally driven at a predetermined angular velocity in the counterclockwise direction indicated by an arrow about a drum shaft (center support shaft) 2a during execution of an image forming process. In this embodiment, the drum 2 is rotationally driven at a speed of 120 mm / s.

  Around the outer periphery of the drum 2, the first charger 3a, the first developer cartridge 4Y, the second charger 3b, the second developer cartridge 4M, the third charger 3c, and the third developer cartridge are arranged along the drum rotation direction. 4C, a fourth charger 3d, and a fourth developing cartridge 4Bk are provided. Further, an intermediate transfer belt unit 5 and a drum cleaner unit 6 are provided.

1) Charger 3
The first to fourth chargers 3 (a to d) are all charging means for charging the surface of the drum 2 and are corona dischargers. By using a corona discharger, the surface of the drum 2 is charged in a non-contact manner by corona discharge. Here, the scorotron charging method was used.

2) Developer cartridge 4
Each of the first to fourth developing cartridges 4 (Y, M, C, Bk) supplies a developer to the electrostatic latent image formed on the drum 2 to convert the electrostatic latent image into a developer image (toner). It is a developing means that visualizes (develops) as an image. Each developing cartridge 4 is a non-contact developing device (jumping developing device) using a two-component developer of toner + magnetic carrier as a developer.

  The developer toner of the first developer cartridge 4Y is yellow toner, and the developer toner of the second developer cartridge 4M is magenta toner. The developer toner of the third developing cartridge 4C is cyan toner, and the developer toner of the fourth developing cartridge 4Bk is black toner.

Each developing cartridge 4 (Y, M, C, Bk) has a developing roller 4a, a developing blade 4b, a stirring rod 4c, and a developing container 4d, and a developer (toner + carrier) is accommodated in the developing container 4d. is there. The developing roller 4 a is driven to rotate at a predetermined speed in a direction opposite to the rotation direction of the drum 2 at a portion facing the drum 2. The developer in the developing container 4d is stirred by the stirring rod 4c, and the toner is frictionally charged by sliding with the carrier. The agitated developer is conveyed to the developing roller 4a side, and is carried and conveyed by the developing roller 4a that rotates by adhering to the developing roller 4a by the magnetic force of the magnet roller in the developing roller 4a. Then, the layer thickness of the attached developer is regulated by the developing blade 4b, and the developer is coated on the developing roller 4a. The coated developer is conveyed to a development site which is a facing portion between the developing roller 4a and the drum 2 by the subsequent rotation of the developing roller 4a. Then, at the development site, the toner flies from the developing roller 4a side to the drum 2 side by the force of the electric field generated by the voltage (developing bias) applied to the drum 2 and the developing roller 4a, and the exposure on the digital photosensitive drum is performed. It adheres to a part (image forming part). That is, the electrostatic latent image formed on the drum 2 is developed as a toner image.

3) Intermediate transfer belt unit 5
The intermediate transfer belt unit 5 includes a primary transfer roller 5a, a secondary transfer roller 5b, an intermediate transfer belt 5c as an endless flexible transfer medium, a backup roller 5d, a tension roller 5e, a driving roller 5f, and a winding roller. 5g etc. An intermediate transfer belt (hereinafter abbreviated as a belt) 5c is stretched around five rollers including a primary transfer roller 5a, a backup roller 5d, a tension roller 5e, a driving roller 5f, and a winding roller 5g. . The winding roller 5g is a roller that urges the belt 5c in the direction in which the belt 5c is wound around the drum 2.

The primary transfer roller 5a and the secondary transfer roller 5b, which are transfer means, each include a cored bar and a cylindrical conductive foam rubber formed on the outer peripheral surface thereof. The diameter of the primary transfer roller 5a is 14 mm, and the diameter of the secondary transfer roller 5b is 16 mm. The volume resistance was set to 10 ⁶ to 10 ⁸ Ωcm for both the primary transfer roller 5a and the secondary transfer roller 5b. The backup roller 5d used was a metal roller surface coated with conductive rubber having a volume resistance of 10 ⁶ to 10 ⁸ Ωcm. Both ends of the primary transfer roller 5a are rotatably supported by bearing members, and are pressed against the drum 2 by a pressing force such as a spring via a belt 5c with a constant force. A contact portion between the drum 2 and the belt 5c is a primary transfer portion T1. The primary transfer voltage was applied by using a conductive resin for the end bearing.

  Further, both ends of the secondary transfer roller 5b are rotatably supported by bearing members, and are pressed against the backup roller 5d with a certain force via a belt 5c by a pressing means such as a spring. Yes. A contact portion between the secondary transfer roller 5e and the belt 5c is a secondary transfer portion T2. The secondary transfer voltage was applied by using a conductive resin for the end bearing.

  The material of the belt 5c may be a conductive endless belt made of a thermoplastic resin such as polycarbonate resin, PVDF (polyvinylidene fluoride), polyalkylene phthalate, or a blend material of PC (polycarbonate) / PAT (polyalkylene terephthalate). Further, conductive endless belts of thermoplastic resins such as ETFE (ethylene tetrafluoroethylene copolymer) / PC, ETFE / PAT, PC / PAT blend materials, and the like are conceivable.

Here, an endless belt 5c in which a conductive filler is dispersed in a polyimide resin excellent in mechanical properties and heat resistance and adjusted to a volume resistance of 10 ⁸ to 10 ¹⁴ Ωcm is used. A belt having a thickness of about 100 μm to 1 mm can be used. The belt 5c is rotationally driven by the driving roller 5f at a constant speed of 120 mm / s with the drum 2 in the clockwise direction of the arrow.

Here, as a typical embodiment, the configuration using the intermediate transfer belt is used for paper, but there is no problem even if the configuration using the transfer roller is used. In the case of using a transfer roller, the material used is an electron conductive type material in which EPDM (ethylene propylene) or urethane is used as a base material and conductive powder such as carbon is added. Alternatively, an ion conductive type in which ammonium tetrachloride is added to the base material is used. A transfer roller having a resistance value of 10 ⁵ to 10 ⁹ Ωcm is used.

4) Drum cleaner unit 6
The drum cleaner unit 6 is a cleaning unit that removes drum surface contaminants such as toner remaining on the surface of the drum 2 after the primary transfer of the toner image from the drum 2 to the belt 5c to clean the drum surface. Here, a blade cleaning device that wipes the drum surface with the cleaning blade 6a and scrapes contaminants from the drum surface is used. The cleaning blade 6a is attached to the waste toner container 6b in contact with the drum 2 in a counter posture with respect to drum rotation.

5) Image Forming Operation The main body control circuit B rotates the drum 2, which is an exposure source-latent image forming integrated digital photosensitive drum, based on the print start signal. Then, by applying −6 kV to the wire of the first charger 3a and −600V to the grid portion, the surface of the photosensitive layer of the drum 2 is charged to about −600V. The photosensitive layer of the drum 2 charged by the first charger 3a is selectively controlled to emit light from the main body control circuit unit B side according to an image signal input to the driving unit on the drum 2 side via the wireless interface. It is exposed by the light emitting pixel portion of the light emitting element matrix layer. By this exposure, the solid image portion potential of the photosensitive portion of the drum 2 is set to about −100 V, and an electrostatic latent image is formed on the drum surface. That is, the main body control circuit unit B emits light in the light emitting element matrix layer of the drum 2 corresponding to the image data and exposes the photoconductor layer in the latent image forming sequence to expose the photoconductor layer. An electrostatic latent image is formed on the charged surface. Here, an electrostatic latent image corresponding to the yellow component image of the full-color image information is formed. The electrostatic latent image is developed as a yellow toner image by the first developing cartridge 4Y. That is, by applying −400 V as a developing bias to the developing roller 4a of the first developing cartridge 4Y, the electrostatic latent image formed on the drum surface is reversely developed with the negatively charged yellow toner.

  Next, the drum 2 on which the yellow toner image is formed is charged again by the second charger 3b. Then, the main body control circuit unit B forms an electrostatic latent image corresponding to the magenta component image of the full color image information in the latent image forming sequence. The electrostatic latent image is developed by the second developing cartridge 4M, and a magenta toner image is superimposed on the yellow toner image on the drum 2.

  Next, the drum 2 on which the yellow toner image + magenta toner image is formed is charged again by the third charger 3c. Then, the main body control circuit unit B forms an electrostatic latent image corresponding to the cyan component image of the full-color image information in the latent image forming sequence. The electrostatic latent image is developed by the third developing cartridge 4C, and a cyan toner image is superimposed on the yellow toner image + magenta toner image on the drum 2.

  Next, the drum 2 on which the yellow toner image + magenta toner image + cyan toner image is formed is charged again by the fourth charger 3d. Then, the main body control circuit unit B forms an electrostatic latent image corresponding to the black component image of the full-color image information in the latent image forming sequence. The electrostatic latent image is developed by the fourth developing cartridge 4Bk, and a black toner image is superimposed on the yellow toner image + magenta toner image + cyan toner image on the drum 2.

  In this way, a full-color unfixed toner image is synthesized and formed on the drum 2 by superimposing four colors of yellow toner image + magenta toner image + cyan toner image + black toner image (multiple development method).

  The color order of the color toner images sequentially formed on the drum 2 is not limited to the above, and any color order configuration can be used.

  The full-color unfixed toner image reaches the primary transfer portion T1 by the subsequent rotation of the drum 2. The primary transfer roller 5a is applied with a primary transfer voltage of + 300V to + 800V having a polarity opposite to the charging polarity of the toner, and the full color is applied to the surface of the belt 5c rotating from the drum 2 side. Unfixed toner images are primary-transferred sequentially and collectively.

  Drum surface contaminants such as toner remaining on the surface of the drum 2 after the primary transfer of the toner image to the belt 5c are removed by the drum cleaner unit 6, and the drum surface is repeatedly used for image formation.

  The full-color unfixed toner image primarily transferred onto the belt 5c as described above is conveyed by the subsequent rotation of the belt 5c, and is a secondary transfer portion which is a contact portion between the belt 5c and the secondary transfer roller 5b. It reaches T2.

  On the other hand, at a predetermined control timing, the recording material is fed from the paper feed cassette 8 of the paper feed unit 7 disposed at the lower part of the printer main body. That is, a paper feed roller 9 attached to the paper feed cassette 8 and a pickup roller 10 attached to the printer main body are driven, and the recording material (not shown) on the paper feed cassette 8 is driven by the both rollers 9. Feed it in between. The recording material passes through the sheet path 11 and is sent to the registration unit 12. The registration unit 12 sends the recording material to the secondary transfer portion T2 at a timing at which the position of the leading end portion of the toner image on the belt 5c and the position of the leading end portion of the recording material are synchronized at the secondary transfer portion T2. The recording material that has entered the secondary transfer site T2 is nipped and conveyed at the secondary transfer site T2, and a secondary transfer voltage of about 1 kV to 3 kV is applied to the secondary transfer roller 5b during the conveyance process. The batch transfer of the four color superimposed toner images on the belt 5c is sequentially received.

  The recording material that has passed through the secondary transfer portion T2 is separated from the surface of the belt 5c, and is introduced into the heat-pressure type fixing unit 14 by the transport unit 13. The unfixed full-color toner image on the recording material is melted, mixed, and fixed on the recording material by applying heat and pressure by the fixing unit 14. Then, it passes through the vertical conveyance unit 15 and the paper discharge unit 16 and is discharged onto the face-down paper discharge tray 17 as a full-color image formed product.

  In the printer of this embodiment, the fixing unit 14 is a film heating type fixing device, and includes a fixing film, a pressure roller, a ceramic heater, and the like. Only the fixing nip formed by the fixing film and the pressure roller is centrally heated by the ceramic heater, so that the toner on the recording material is melted and fixed.

  Further, the transfer residual toner on the belt 5c after the secondary transfer of the toner image to the recording material is removed and collected by the belt cleaner unit 18.

  The above is the case of the full color image forming mode. In the case of a mono-color image forming mode such as monochrome, an image forming operation is performed by a developing cartridge of a designated color and a charger as a pair. The developing cartridges of the other colors and the chargers in combination with the developing cartridges do not perform an image forming operation.

(2) Digital photosensitive drum 2
3A is a longitudinal sectional view of the drum 2, FIG. 3B is an enlarged view of one end side (drive side), and FIG. 3C is an enlarged view of the other end side (non-drive side). FIG. 4 is a perspective view of the driving unit and the rotation phase detection unit of the drum 2.

  The digital photosensitive drum 2 is formed by laminating a self-luminous device part as a light emitting element matrix layer (light emitting element array), a function separating part, and a photosensitive part (photoreceptor layer) on a cylindrical substrate. This is a rotating drum type photosensitive device integrated with a light source and a latent image.

  Cylindrical flanges 31a and 31b are press-fitted coaxially with the drum 2 and fixed to the opening portions at both ends of the drum 2, and the drum shaft 2a is inserted between the flanges 31a and 31b. . Both flanges 31a and 31b are integrally fixed to the drum shaft 2a. The axis of the drum 2 and the axis of the drum shaft 2a are coaxially matched. Both ends of the drum shaft 2a protrude outward from the flanges 31a and 31b, and bearings 32a and 32b are fitted on the protruding shafts, respectively. In addition, a drum gear G2 is coaxially fitted to the driving shaft and is integrally fixed to the drum shaft 2a. An encoder wheel portion 33 for phase detection is provided on the outer peripheral portion (outer diameter portion) of the end of the flange 31a on the drive side. The bearings 32a and 32b are respectively held by the drum frame Pa and Pb.

  The drum gear G2 meshes with the drive gear GD as shown in FIG. Then, when the driving force is transmitted from the drive gear GD to the drum gear G2, the drum shaft 2a is rotationally driven. That is, the drum 2 is rotationally driven.

  FIG. 5 is a schematic diagram of the layer structure of the digital photosensitive drum 2 in this embodiment. This drum 2 is an exposure source in which three functional layers of a self-light emitting device unit 50 as a light emitting element matrix layer (light emitting element array), a function separating unit 60, and a photosensitive member unit 70 are laminated on a cylindrical substrate 40. -A rotary drum type photosensitive device integrated with latent image formation. FIG. 5 is a cross section in a plane including the drum axis of the drum 2 and including one of the second electrode lines arranged in parallel to the axis.

  Here, for convenience, in the following description, an annular first electrode line that is included in the self-light-emitting device unit 50 and makes one round in the circumferential direction of the cylindrical substrate is referred to as a “signal line”, and is also included in the self-light-emitting device unit 50. The linear second electrode line in the longitudinal direction of the cylindrical substrate is referred to as a “scan line”.

(2-1) Cylindrical substrate 40
In this embodiment, the cylindrical base 40 uses an aluminum cylinder (hereinafter referred to as a drum cylinder).

(2-2) Self-luminous device unit 50
The light-emitting device unit 50 includes a signal line (first electrode line) / scanning line (second electrode line) control unit (control circuit unit) 51, which are stacked in order from the inside to the outside with respect to the outer peripheral surface of the drum cylinder 40. , A signal line layer 52, an EL light emitting layer 53, and a scanning line layer 54.

  The signal line layer 52 is a layer of signal lines (sub-scanning signal line group) including a plurality of annular signal lines 52e separated by an insulator 52g and arranged at predetermined equal intervals in the longitudinal direction of the cylindrical substrate. is there.

  The scanning line layer 54 is separated by an insulator 54b (FIG. 9B (e)) and includes a scanning line group (main scanning) including a plurality of linear scanning lines 54a arranged at predetermined equal intervals in the circumferential direction of the cylindrical substrate. Signal line group).

  The group of annular signal lines 52e in the signal line layer 52 and the group of linear scanning lines 54a in the scanning line layer 54 constitute a form stretched in a vertical and horizontal lattice pattern as shown in the schematic diagram of FIG. The intersection of the signal line 52e and each scanning line 54a is a pixel portion.

  The function of the signal line / scanning line control unit 51 is ON / OFF control of each signal line 52e of the signal line layer 52 and each scanning line 54a of the scanning line layer 54. The gate 51b of the final stage driving TFT 51d is controlled to turn on / off the signal line 52e and the scanning line 54a. That is, each pixel is controlled independently. The source electrode of the driving TFT 51d is connected to the electrode pad 51e. The driving TFT 51d in FIG. 5 is a transistor on the signal line control circuit side, and the driving TFT 51d in FIG. 9 is a transistor on the scanning line control circuit side.

  The signal line / scanning line control unit 51 is obtained by transferring a control circuit formed on a glass substrate by a poly-Si process onto the drum cylinder 40 by a so-called device transfer method. 51a is a polysilicon layer (insulating layer) of a circuit formed by a poly-Si process, and is bonded to the surface of the drum cylinder 40. A driving driver (a constant current circuit, a lighting time control circuit, a shift register, a buffer, etc.) for the driving TFT 51d is formed on the same device.

  The signal line layer 52 includes interlayer insulating layers (insulating films) 52a and 52b, a plurality of annular signal lines 52e, and a through-hole electrode (large) 52c that is an interlayer electrode connected to the signal line 52e and the electrode pad 51e of the driving TFT 51d. And a through-hole electrode (small) 52d.

  The signal line 52e in the present embodiment is an Ag electrode having a width of 10 μm and has an annular shape that goes around the drum cylinder 40 once. The annular signal line 52e is separated by a partition wall 54b, which is an insulator, and is arranged in a large number at predetermined equal intervals in the drum cylinder longitudinal direction. In this embodiment, the mutual interval between the annular signal lines 52e is about 42 μm (pixel resolution 600 dpi), and 5120 lines (A4 paper portrait printing compatible) match the annular axis line of the signal line 52e with the drum axis line 2a. Are arranged to be. Each signal line 52e is connected to the electrode pad 51e of the driving TFT 51d through the through-hole electrodes 52d and 52c.

  The EL light emitting layer 53 constitutes a charge injection type fluorescent light emitting element using organic EL. In this embodiment, the signal line 52e side is a cathode made of metal electrode (Ag), and the scanning line 54a side is made an anode made of metal oxide (ITO). Therefore, a four-layer structure in which an electron transport layer (ETL), a light emitting layer (EML), a hole transport layer (HTL), and a hole injection layer (HIL) are stacked in this order from the signal line 52e side to the scanning line 54a side. did.

  The scanning line 54a of the scanning line layer 54 is a linear pattern electrode having a width of 10 μm and extending in the longitudinal direction of the drum cylinder. The scanning line 54a is separated by a partition wall 54b, which is an insulator, and is arranged at predetermined equal intervals in the circumferential direction of the cylindrical substrate. Multi-arrayed. Each scanning line 54a is formed of a transparent conductive oxide (ITO). In this embodiment, the mutual interval between the scanning lines 54 a is about 42 μm (pixel resolution 600 dpi), and 8374 scanning lines 54 a (φ112 drum, phase angle 0.043 degrees) are connected to the drum axis in the scanning line layer 54. They are arranged with parallel or crossing angles. Each scanning line 54a is connected to the electrode pad 51e of the driving TFT 51d through the through-hole electrodes 54c and 52c as shown in FIG. 9B (e).

(2-3) Function separation unit 60
The function separating unit 60 includes a transparent insulating / gas barrier layer (hereinafter referred to as a transparent insulating / barrier layer) 61 that is an insulating layer that electrically insulates the self-luminous device unit 50 from the photosensitive member unit 70, And a transparent conductive layer (transparent conductive film) 62 provided thereon. The transparent insulating / barrier layer 61 is a multilayered laminated film of an organic polymer film and a metal oxide thin film (Al ₂ O ₃ ). The transparent conductive layer 62 is formed by depositing ITO on the surface (cylindrical outer peripheral surface side) of the transparent insulating / barrier layer 61. As a result, the functional separation layer 60 maintains a high gas barrier performance with a visible light transmittance of 85% (λ = 520 nm).

(2-4) Photosensitive member 70
The photoconductor section 70 has an undercoat layer (UCL) 71, a carrier generation layer (CGL) 72, a carrier transfer layer (CTL) 73, and a protective layer 74 in order on the transparent conductive layer 62 of the function separating section 60. Are organic photoconductors (OPC).

  The basic configuration of the digital photosensitive drum 2 of the present embodiment is substrate / signal line driver / EL layer / signal line / scanning line / sealing barrier (transparent insulating film) / ITO / OPC. The signal line driver (drive unit) is divided into a plurality of parts. The signal line driver and the signal line have a vertical contact structure with a through hole. The scanning line driver is disposed outside the image area of the drum 2. The scanning line is ITO or ITO + auxiliary electrode. Top emission structure.

  In the digital photosensitive drum 2 of the present embodiment, the self light emitting device unit 50 includes a signal line / scanning line control unit 51, and a signal line layer 52 on the signal line / scanning line control unit 51. That is, the distance between the control unit 51 and the signal line 52e is shorter than the distance between the control unit 51 and the scanning line 54a. Since the electric signal is less likely to attenuate when the signal line 52e is closer to the control unit 51, the signal line 52e can be stably controlled.

  If there is an organic EL layer 53 between the signal line 52e and the scanning line 54a, the EL layer 53 can emit light by a PM (passive matrix) method. Therefore, when the control unit 51 is provided on the base body 40, it is possible to perform light emission control in the order of the layer structure of the control unit 51, the signal line layer 52, the EL layer 53, and the scanning line layer 54 from the base body 40 side. It is. In addition, it is possible to perform light emission control with the layer structure in the order of the control unit 51, the scanning line layer 54, the EL layer 53, and the signal line layer 52 from the base 40 side. In other words, it is possible to control light emission in either of the layer configurations 1) and 2). However, it can be said that 1) is better than 2). That is, the signal line 52e is more finely controlled than the scanning line 54a. This is because at which position in the longitudinal direction of the drum 2 the EL layer 53 is illuminated is determined by the image data signal, and the signal line 52e must be controlled according to the image data. On the other hand, the scanning line 54a is in charge of which position in the circumferential direction of the drum 2 shines the EL layer 53, and the control of the scanning line 54a is not changed by the image data. As described above, by arranging the signal line 52e to be finely controlled near the control unit 51, it is possible to suppress the attenuation of the data signal. In particular, since the control unit 51 is provided on the base body 40, the signal line 52e and the control unit 51 can be arranged close to each other.

  In the digital photosensitive drum 2 of the present embodiment, each scanning line 54a of the scanning line layer 54 is formed of a transparent conductive oxide (ITO). Since the scanning line 54 a is transparent, it does not prevent the light emitted from the EL layer 53 from going to the photosensitive member 70. As described above, the organic EL layer 53 is between the signal line 52e and the scanning line 54a. Therefore, either the signal line 52e or the scanning line 54a is always formed on the EL layer 53. Here, since the signal line 52e is formed in an annular shape, it is difficult to make an ITO signal line by sputtering or the like. On the other hand, since the scanning line 54a is linearly provided in the longitudinal direction of the drum 2, the ITO electrode line can be formed more easily than the annular signal line 52e. Therefore, the scanning line 54a is formed on the EL layer 53, and further, the scanning line 54a is formed of a transparent conductive oxide (ITO) so that the light emitted from the EL layer 53 is not disturbed. The body part 70 can be irradiated.

  The main body control circuit section B, which is a control means, emits light from each light emitting pixel section of the light emitting element matrix layer corresponding to the image data and exposes the photoreceptor layer, whereby an electrostatic latent image is formed on the charged surface of the photoreceptor layer. Form.

  With the simple means described above, an exposure source-photoreceptor integrated digital photosensitive drum can be mounted during the configuration of a conventional electrophotographic image forming process. Further, the writing position correction or the sub-scanning registration correction in the in-line color machine can be performed without being affected by fluctuations in the image forming speed.

(3) Manufacturing Process of Digital Photosensitive Drum 2 FIGS. 7 to 9 show an outline of a manufacturing process of the digital photosensitive drum 2 in this embodiment. FIG. 7 is a flowchart of the outline of the manufacturing process, and FIGS. 8 to 9 are process schematic diagrams of the manufacturing process.

Process P1: Formation of Control Circuit A signal line / scanning line control circuit (device) that is a circuit including signal line driving and I / F (interface) using a poly-Si process on the original substrate (glass substrate) Form.

Process P2: Device Transfer The device is peeled off from the original substrate, and the device is transferred onto the outer peripheral surface of the drum cylinder 40. That is, the signal line / scanning line control unit 51 is formed on the outer peripheral surface of the drum cylinder 40 ((a) in FIG. 8A).

  The device is bonded and fixed so as to wrap around the outer peripheral surface of the drum cylinder 40. At this time, in order to absorb the tolerance of the outer diameter dimension of the drum cylinder 40 and the winding peripheral length of the device, a seam having a gap of 250 μm or less remains in the winding portion of the device.

Process P3: Formation of Insulating Layer 52a Flanges 31a and 31b (FIG. 3) are attached to both ends of the drum cylinder 40. An organic polymer layer is formed as an interlayer insulating layer 52a on the outer peripheral surface of the drum on which the signal line / scanning line control unit 51 is formed ((b) of FIG. 8A).

  In this example, a 10 μm polyimide film was coated by dipping as the insulating layer 52a. By this step, the seam portion is filled, and the drum outer peripheral surface becomes a seamless continuous curved surface.

Process P4: Formation of Signal Line Layer 52 A via hole (large through hole) 52f is formed in the insulating layer 52a by laser processing toward the center of the signal line electrode pad 51e of the drive TFT 51d of the signal line / scanning line control unit 51 ( (C) of FIG. 8A).

  Next, the via hole 52f is embedded with a conductive paste. That is, the through-hole electrode (large) 52c is formed ((d) in FIG. 8B).

  Also, on the scanning line drive circuit side, the formation of the through hole (large) 52f for the scanning line 54a and the formation of the through hole electrode 52c are similarly performed ((a) and (b) of FIG. 9A).

  The outer peripheral surfaces of the insulating layer 52a and the through-hole electrode 52c are polished and smoothed by a CMP process.

  Next, by a photolithography process, a plurality of signal lines (first electrode lines) 52e are formed in a circular shape without a cut in the circumferential direction of the drum cylinder, separated from each other by an insulator 52g and arranged in the longitudinal direction of the drum cylinder. ((E), (f) of FIG. 8B).

  52f is a through hole (small), and 52g is an insulating partition for signal line patterning. A through-hole electrode 52d is formed in the through-hole (small) 52f portion, and is formed simultaneously with the formation of the signal line 52e. Each signal line 52e is connected to the electrode pad 51e of the driving TFT 51d through the through-hole electrodes 52d and 52c.

  A through hole (small) 52f is also formed on the scanning line driving circuit side ((c) in FIG. 9A).

Process P5: Formation of the organic EL layer 53 On the surface of the signal line layer 52, a plurality of partition walls made of an insulator for scanning line patterning are linear in the drum cylinder longitudinal direction and at a predetermined interval and width in the drum cylinder circumferential direction. 54b is formed (FIG. 8C (g), FIG. 9B (d)).

  Next, the organic EL layer 53 is formed by vapor deposition ((h) in FIG. 8C).

Process P6: Formation of Scan Line Layer 54 A scan line 54a is formed into a pattern by sputtering ITO using a shadow mask ((i) in FIG. 8C, (e) in FIG. 9B). At this time, a through-hole electrode (interlayer electrode) 54c between the scanning line 54a and the through-hole (large) 52c on the scanning line driving circuit side is also formed simultaneously.

  By the above processes P1 to P6, the light emitting device unit 50 is formed on the outer peripheral surface of the drum cylinder 40 by sequentially stacking the signal line / scanning line control unit 51, the signal line layer 52, the EL light emitting layer 53, and the scanning line layer 54. It is formed.

Process P7 <Transparent Insulation / Formation of Barrier Layer 61>
A polymer (PEN) layer and a metal oxide (Al ₂ O ₃ ) layer are alternately and continuously deposited as a transparent insulating / barrier layer 61 on the outer peripheral surface of the self-luminous device part 50 formed as described above. To form a film ((j) in FIG. 8D).

Process P8: Formation of Transparent Conductive Layer 62 On the outer peripheral surface of the transparent insulating / barrier layer 61, ITO is deposited as the transparent conductive layer 62 by sputtering ((k) in FIG. 8D).

  By the processes P7 and P6 described above, the function separating portion 60 having gas barrier properties, surface conductivity, and visible light permeability is formed on the outer peripheral surface of the self-luminous device portion 50.

Process P9: Formation of Photosensitive Member 70 On the outer peripheral surface of the function separating portion 60, as the photosensitive member 70, an undercoat layer (UCL) 71, a carrier generation layer (CGL) 72, a carrier transfer layer (CTL) are formed by dipping coating. ) 73 and a protective layer 74 are formed to form an organic photoreceptor (OPC) layer.

  All processes of film formation, photolithography, and through-hole electrode formation for forming the self-luminous device section 50, the function separating section 60, and the photoreceptor section 70 are processes from the drum outer peripheral surface side.

  By the manufacturing processes P1 to P9 described above, the small-diameter digital photosensitive drum 2 that is seamless in the drum circumferential direction can be realized.

  That is, a discontinuous portion, that is, a seam remains on the drum circumference until the signal line / scanning line control circuit of the process P2 is transferred to the device and formed on the drum cylinder 40. However, the drum outer diameter portion after the interlayer insulating layer 52a is formed in the process P3 has a seamless cylindrical surface shape. Further, in the subsequent process, the signal line 52e is formed in an annular shape, and the scanning line 54a is arranged symmetrically with respect to the drum rotation axis.

  With the above configuration, a seamless pixel matrix having light emitting points (pixels) near the intersection of the signal line 52e and the scanning line 54a is formed. That is, a seamless and small-diameter digital photosensitive drum 2 is manufactured. Thereby, the size of the printer main body can be reduced by including the exposure device. The stability of the output image against vibration and load fluctuation is improved.

(4) Driving Method of Digital Photosensitive Drum 2 FIG. 10 is a block diagram of a driving circuit for the digital photosensitive drum 2.

  Transmission and reception of electrical information signals including image data between the main body control circuit B of the printer A and the control circuit on the side of the digital photosensitive drum 2 that is driven to rotate is performed by a wireless interface.

  In this embodiment, the light emitting pixels on the drum 2 side are driven by passive matrix (PM) driving by sequentially selecting the scanning lines 54a. That is, the drive circuit sequentially selects the scanning lines 54a of the scanning line layer 54, and drives the signal lines 52e of the signal line layer 52 in synchronization with the scanning lines 54a. As a result, the circuit is driven in a line sequential manner in which a light emitting pixel portion in the vicinity of a point where the scanning line 54a and the signal line 52e intersect is caused to emit light to form a light emission pattern corresponding to image data.

  In this embodiment, the number of scanning lines 54a is 8374, the scanning line interval is about 42 μm (resolution 600 dpi), the image forming speed is 120 mm / s, and the steady scanning cycle is about 352 μs (scanning frequency 2.8 KHz). Select sequentially.

  The scanning line potential is controlled to + potential when selected and 0 V (GND) when not selected. By controlling ON / OFF of the scanning line in synchronization with the selection of the scanning line, a light emission pattern corresponding to the image data on the scanning line is formed. In this embodiment, the signal line 52e is set to about 0V (GND) when not selected and + 5V when not selected. By setting the non-selection potential of the scanning line 54a and the selection potential of the signal line 52e substantially equal, light emission on the non-selected scanning line is prevented.

  The phase detection configuration of the digital photosensitive drum 2 in this embodiment will be described with reference to FIG. FIG. 4 shows the drive side end of the digital photosensitive drum 2.

  The drum 2 is provided with an encoder wheel portion 33 for phase detection at an outer diameter portion of a driving side drum flange 31 a fixed coaxially with the drum 2 at an end portion of the drum cylinder 40. Therefore, if the drum 2 is driven to rotate, the encoder wheel unit 33 also rotates together with the drum 2. The encoder wheel portion 33 is provided coaxially with the central axis of the drum 2.

  The phase division pattern of the encoder wheel unit 33 maintains the phase relationship with the scanning line 54 a of the scanning line layer 54 of the drum 2.

  The encoder wheel portion 33 is an etching pattern of black Cr formed on the outer diameter portion of the drum flange 31a made of aluminum alloy. In this embodiment, the number of decomposition is 8374 divisions (4174 divisions for each of the AB phases), and 0 inspection is performed. Has outgoing Z phase.

  On the other hand, the phase detector 34 is a reflection type photodetector with Z-phase detection, and is fixed to the drum frame. The phase division pattern of the encoder wheel unit 33 is detected by the phase detector 34. The detection signal of the phase detector 34 is input to the phase detection circuit internal counter (FIG. 10) of the main body control circuit unit B. The rotation angle of the drum 2 is obtained by adding the A / B phase output detected by the phase detector 34 to the internal counter of the main body control circuit unit B. The internal counter operates in a mode that is reset when the Z phase that is the reference position of the drum 2 is detected.

  When the image formation start trigger is issued, the main body control circuit B detects the current phase of the drum 2 from the current value of the internal counter in the scanning line selection control unit (FIG. 10), and the scanning line to be driven for exposure. 54a is selected. That is, at the time of image formation, the main body control circuit unit B calculates the phase of the drum 2 with respect to the drum frame based on the output signal from the phase detector 34, and determines the scanning line to be driven based on this value. At the time of writing trigger, the writing scanning line 54a on the drum is selected from the current phase of the drum 2. Writing scanning is performed in synchronization with the current phase pulse of the drum 2.

  FIG. 11 shows the drive timing. One strobe cycle corresponds to a scanning line selection cycle. In this embodiment, all the signal lines 5120 are divided into five segments for control. For this reason, the light emission is performed in a time-sharing manner in which each segment is sequentially driven with a time of about 50 μs.

  The luminescent pixel data is latched in the LINEn + 1 data in the frame in which the scanning line LINEn emits light. Light emission data (4-bit data including light emission time information) of 1024 segments is transferred to the signal drive circuit in a time division manner and latched into the buffer.

  FIG. 12 shows a block diagram of data transfer. The segment (Segment) is selected by the address (ADDR) generated by the control unit, and the data (DATA) is transferred to the corresponding segment. Here, the frequency of the data (DATA) transfer clock (CLK) is 20 MHz.

  With the above configuration, in the self-light-emitting device unit 50, in the vicinity of a portion where the scanning line 54a of the selected pixel intersects with the signal line 52e by line-sequential selection of the scanning line 54a and ON / OFF driving of the signal line 52e synchronized therewith. A fluorescent spot is generated by the organic EL layer 53. By directly exposing the photoconductor portion 70 laminated thereon with the fluorescent spot, a charge density distribution on the photoconductor surface, that is, an electrostatic latent image is formed. The exposure amount is determined by the exposure area, sensitivity, and exposure time of the digital photosensitive drum.

  That is, the main body control circuit unit B forms an electrostatic latent image on the charged surface of the photoconductor layer by causing each light emitting pixel unit of the light emitting element matrix layer to emit light corresponding to the image data and exposing the photoconductor layer. To do.

(5) Suppression of scattering before transfer of toner image As described above, the four-color superimposed toner image formed on the digital photosensitive drum 2 is transferred to the contact portion between the drum 2 and the belt 5 for transfer to the belt 5c. To the primary transfer site T1.

The main body control circuit unit B performs the process from the formation of the fourth color toner image (here, the black toner image) to the primary transfer portion T1 (hereinafter referred to as the primary transfer roller position) by the fourth developing cartridge 4Bk. In the meantime, a pre-transfer exposure sequence is executed. That is, the fourth developing cartridge drum rotation direction downstream of the 4Bk in (image bearing member rotational direction downstream side), the primary transfer drum rotating direction upstream side of the roller 5a (image bearing a transfer means is the last developing means Pre-transfer exposure is performed between the upstream side of the body rotation direction) .

  In the printer of the present embodiment, the rotation angle α (FIG. 2) of the drum 2 is from the development site (development position) of the fourth development cartridge 4Bk of the fourth color as the final development means to the primary transfer roller position. There are about 50 degrees.

According to the study by the present inventors, in order to effectively suppress the toner image scattering before transfer,
It has been found that the pre-transfer exposure to the photoreceptor may be performed as follows. That is, for at least the same area of the non-image forming portion on the surface of the photoconductor, the surface potential of the photoconductor is not brought close to about 0V by one pre-exposure exposure, but long time transfer with a small amount of light is performed on the same area of the photoconductor surface. Pre-exposure is performed, and finally the photoreceptor surface potential is set to approximately 0V.

A pre-transfer exposure method that takes this into account will be described below. A pre-exposure position transfer in the present embodiment, the change in surface potential on the drum 2 of the non-image portion (non-image formation point) and the image portion (image forming positions) shown in FIG. 13. The upper side of FIG. 13 shows the drum 2 and the intermediate transfer belt 5.
c is a conceptual diagram, and pre-transfer exposure locations are shown with angles.

  The pre-transfer exposure is performed by a sequence in which the light emitting pixel portion of the light emitting element matrix layer of the drum 2 is controlled to emit light while the drum 2 rotates from the developing portion of the fourth developing cartridge 4Bk for the fourth color to the primary transfer roller position. This is done by exposing the part.

  The lower side of FIG. 13 shows changes in the surface potential of the drum 2 due to the above-described pre-transfer exposure. The horizontal axis indicates the drum pre-transfer exposure position on the upstream side in the drum rotation direction with respect to the primary transfer roller position as a reference (0 position). The vertical axis represents the surface potential on the drum 2. However, the potential increases negatively as it goes on the vertical axis. A solid line indicates a non-image portion potential, and a broken line indicates an image portion potential.

With respect to the same area of the non-image forming portion and the image forming portion on the photoreceptor surface, the first pre-transfer exposure is started at a drum rotation angle position of about 30 degrees upstream of the primary transfer roller position in the drum rotation direction. Next, the second pre-transfer exposure is started at a drum rotation angle position of about 20 degrees. Finally, the third pre-transfer exposure is started at a drum rotation angle position of about 10 degrees. The pre-transfer exposure time for the first, second and third times was 1 μs. As a result, the surface potential of the non-image portion of the drum 2 was lowered stepwise so that it would be −300 V after the third pre-transfer exposure. That is, by this multiple exposure, the surface potential of the photoreceptor layer becomes
| Non-image forming part potential |> | Image forming part potential |
To satisfy this relationship.

In this way, by performing light emission control on the light emitting pixel portion of the light emitting element matrix layer of the drum 2, pre-transfer exposure is performed in a sequence in which the same region of the non-image forming portion and the image forming portion on the photoreceptor surface is exposed multiple times. . That is, the light emitting pixel portion of the light emitting element matrix layer corresponding to at least the non-image forming portion of the photosensitive layer is caused to emit light downstream of the developing unit in the drum rotation direction and upstream of the transfer unit in the drum rotation direction. Compared to the case where the surface potential of the drum 2 is lowered to −300 V in one pre-transfer exposure by executing a pre-transfer exposure sequence in which exposure is performed a plurality of times for at least the same area as the non-image forming portion of the photosensitive layer. Further, the toner image scattering due to the pre-transfer exposure can be stably suppressed, and the apparatus can be miniaturized.

  FIG. 14 shows changes in the pre-transfer exposure position and the surface potential of the non-image area and the image area on the drum 2 in this embodiment.

In this embodiment, the first transfer is performed at the drum rotation angle position of about 5 degrees upstream of the primary transfer roller position in the drum rotation direction with respect to the same area of the non-image forming portion and the image forming portion on the photosensitive member surface. Start pre-exposure. At this time, the gap between the drum 2 and the belt 5c is about 200 μm. Next, a second pre-transfer exposure is started at a drum rotation angle position of about 3 degrees upstream of the primary transfer roller position in the drum rotation direction. Then, the third pre-transfer exposure is started at a drum rotation angle position of about 1 degree upstream of the primary transfer roller position in the drum rotation direction. Exposure time in the first pre-transfer exposure point 0.5 .mu.s, in the second pre-transfer exposure point 1 [mu] s, and 1.5μs in third pre-transfer exposure point. As a result, the surface potential of the non-image area of the drum 2 was lowered stepwise so that it would be about −300 V after the third pre-transfer exposure.

  In this way, in addition to the same effects as in the first embodiment, the exposure time is increased as the transfer nip is approached, thereby reducing the potential difference between the non-image portion potential and the image portion potential as close to the transfer nip as possible. can do. As a result, when pre-transfer before the transfer nip is performed, a pressing electric field due to a potential difference between the image portion and the non-image portion is maintained, and toner scattering during pre-transfer can be prevented.

  FIG. 15 shows the pre-transfer exposure position and the change in the surface potential of the non-image area and the image area on the drum 2 in this embodiment.

  In the present embodiment, the first pre-transfer exposure is performed at the drum rotation angle position of about 30 degrees upstream of the primary transfer roller position in the drum rotation direction with respect to the same region for only the non-image forming portion on the photoreceptor surface. Start. Next, the second pre-transfer exposure is started at a drum rotation angle position of about 20 degrees. Then, the third pre-transfer exposure is started at a drum rotation angle position of about 10 degrees. As a result, the surface potential of the non-image portion of the drum 2 was lowered stepwise so that the surface potential of the non-image portion of the drum 2 became −300 V after the third pre-transfer exposure. The pre-transfer exposure time for the first, second and third times was 1 μs. As a result, the surface potential of the non-image portion of the drum 2 was lowered stepwise so that it became about −300 V after the third pre-transfer exposure.

  By doing so, in addition to the same effects as in the first embodiment, it is possible to eliminate the waste of exposing the image portion, and it is possible to reduce power consumption.

  FIG. 16 shows the pre-transfer exposure position and the change in surface potential of the non-image area and the image area on the drum 2 in this embodiment.

  In the present embodiment, the first pre-transfer exposure is performed at the drum rotation angle position of about 30 degrees upstream of the primary transfer roller position in the drum rotation direction with respect to the same region for only the non-image forming portion on the photoreceptor surface. Start. Next, the second pre-transfer exposure is started at a drum rotation angle position of about 10 degrees. Then, the third pre-transfer exposure is started at a drum rotation angle position of about 1 degree. As a result, the surface potential of the non-image portion of the drum 2 was lowered stepwise so as to be 0V or substantially 0V after the third pre-transfer exposure. The exposure time for the first pre-transfer exposure was 1 μs, the exposure time for the second pre-transfer exposure was 1 μs, and the exposure time for the third pre-transfer exposure was 4 μs.

  By performing the pre-transfer exposure as described above, the surface potential of the non-image portion of the drum 2 is set to approximately 0 V when the transfer nip enters. At this time, regardless of the image portion and the non-image portion, all the organic EL light emitting elements in the direction perpendicular to the rotation direction of the drum 2 emit light when reaching this angle.

  Thus, in addition to the same effects as in the first embodiment, the applied transfer bias can be lowered by reducing the surface potential of the drum 2 while suppressing toner scattering on the drum 2. Further, transfer efficiency can be improved.

  Further, it is possible to suppress toner scattering due to non-image portion discharge that occurs when a low-resistance recording material (transfer material) is used.

  A pre-transfer exposure amount is set to a predetermined light amount at which the non-image portion potential does not become lower than the image portion potential (Japanese Patent Laid-Open No. 1-191168). In this configuration, non-image is caused by fluctuations in the image portion potential caused by changes in the charge amount of the photosensitive member over time, exposure amount fluctuations due to deterioration of the pre-transfer exposure element, or fluctuations in toner charge amount due to changes in wet temperature. The part potential and the image part potential did not become the desired potential, and toner scattering occurred.

  In order to avoid this, the pre-transfer exposure amount is controlled (Japanese Patent Laid-Open No. 10-186814). Specifically, the surface potential before and after the pre-transfer exposure on the image carrier is measured, and the exposure amount so that the non-image portion potential (absolute value) after exposure is larger than the image portion potential (absolute value) after exposure. To control. However, in order to control the exposure amount with this configuration, complicated control is required. In addition, since the amount of change in potential due to changes over time and environmental changes is small, accuracy is also required. Furthermore, if taking into consideration variations in the amount of light and the lens of the LED as a pre-transfer exposure element, a highly accurate pre-transfer exposure apparatus (including a control unit) is additionally required.

  In order to solve the above problems, in this embodiment, the surface potential on the image carrier is measured using a potential sensor or the like, and the transfer is performed according to the number of pre-transfer exposures or the pre-transfer exposure time determined based on the surface potential. Pre-exposure is performed. That is, the surface potential of the photoconductor layer is detected downstream of the fourth developing cartridge 4Bk, which is the final developing unit, in the drum rotation direction, and upstream of the primary transfer roller 5a, which is the transfer unit, in the drum rotation direction. Potential detecting means is provided. When the absolute value of the potential measurement value of the potential detecting means is smaller than the reference value, the main body control circuit unit controls to reduce the pre-transfer exposure amount in the pre-transfer exposure sequence. As a result, the potential of the non-image area and the image area is changed due to the fluctuation of the image portion potential caused by the change in the exposure amount due to the change in the charge potential of the photoconductor, the exposure element deterioration, or the change in the toner charge amount due to the change in the wet temperature. It is possible to suppress the scattering of toner that has not occurred at a desired potential.

  More specifically, in this embodiment, as shown in FIGS. 1 and 2, a sensor SV for measuring the surface potential of the drum 2 is provided. This potential sensor SV measures the non-image portion potential on the drum 2 at a position near the developing portion of the fourth developing cartridge 4Bk on the downstream side in the drum rotation direction from the developing portion of the fourth developing cartridge 4Bk. The measured potential information is input to the main body control circuit unit B.

  Here, the initial non-image portion potential on the drum 2 was −600V. It became about -570 V due to deterioration after endurance of 10,000 sheets. Therefore, the main body control circuit portion B calculates the exposure time by dividing this value by the number of exposures in the arithmetic processor. Here, the number of exposures was set to 3 in advance, and one exposure time was calculated. As a result, the exposure time for one exposure is 0.95 μs (in this embodiment, the exposure amount is set such that the 100 V potential is changed by the pre-transfer exposure of 1 μs). Thus, the surface potential of the drum 2 was set to −300 V after the third pre-transfer exposure. The state of pre-transfer exposure at this time is shown in FIG.

  This configuration performs precise control to form a latent image. Therefore, by diverting the main body control circuit part (controller part) B for pre-transfer exposure, it is not necessary to introduce new control, and cost reduction can be expected. Furthermore, highly accurate pre-transfer exposure control is possible. Further, the occurrence of variations in exposure becomes a serious problem during the formation of a latent image. Therefore, variations in exposure are eliminated by controlling the exposure amount. For this reason, it is not necessary to control the exposure amount variation again before the transfer at the time of the pre-transfer exposure.

  In this way, precise control is performed by pre-transfer exposure. As a result, the potential of the non-image area and the image area is changed by the fluctuation of the image portion potential caused by the variation of the exposure amount due to the change of the drum charging potential with time, the exposure element deterioration, or the variation of the toner charge amount due to the change of the wet temperature. It is possible to prevent a problem in which toner does not become a desired potential and toner scattering occurs.

  When performing pre-transfer exposure using a conventional LED, the exposure time is determined by the rotation speed of the image carrier. For this reason, there is a restriction even if the exposure time before transfer is increased. For example, the time during which a pixel of 600 dpi can be exposed is 350 μs when the image carrier surface speed is 120 mm / s.

  In the passive matrix driving of the digital photosensitive drum 2 as in the first to fifth embodiments, a separate scanning line is selected for the pre-transfer exposure, and a corresponding driver is attached to thereby reduce the exposure time for one transfer. Can be long. Here, the driving configuration is such that all the signal drivers are grounded and only the scanning driver is driven.

  In the printers of Embodiments 1 to 5, as described above, the rotation angle α of the drum 2 (FIG. 2) from the development site (development operation position) of the fourth color development cartridge 4Bk to the primary transfer roller position. There are about 50 degrees.

  Accordingly, if pre-transfer exposure is started from a position of 45 degrees upstream of the primary transfer roller position in the drum rotation direction, pre-transfer exposure can be performed for about 370 ms. By adopting the configuration as in the present embodiment, it is possible to perform exposure for a long time by continuous exposure, compared to the pre-transfer exposure using a conventional LED.

  On the other hand, when using the active matrix drive, the pre-transfer exposure time can be extended by using the charge accumulated in the storage capacitor. This enables pre-transfer exposure of about 1 ms.

In this way, at least the photosensitive layer is exposed not by multiple times of exposure, but by continuous pre-transfer exposure, that is, downstream of the developing unit in the drum rotation direction and upstream of the transfer unit in the drum rotation direction. A digital photosensitive drum is obtained by executing a pre-transfer exposure sequence in which a light emitting pixel portion of a light emitting element matrix layer corresponding to a non-image forming portion emits light and continuously exposes at least the same region as the non-image forming portion of the photosensitive layer. The surface potential of the second non-image forming portion can be brought close to approximately 0V.

  The image forming apparatus according to the embodiment is a one-drum type color image forming apparatus, but may be an inline color image forming apparatus having a plurality of drums. Also, a monocolor image forming apparatus can be provided.

Schematic cross-sectional view showing schematic configuration of electrophotographic image forming apparatus of embodiment Partial enlarged view of FIG. (A) is a longitudinal sectional view of the digital photosensitive drum, (b) is an enlarged view of one end side (drive side), and (c) is an enlarged view of the other end side (non-drive side). The perspective view which looked at the drive part and phase detection part of a digital photosensitive drum Schematic diagram of the layer structure of the digital photosensitive drum in the embodiment Schematic diagram of vertical and horizontal lattice structure of signal line group of signal line layer and signal line group of scanning line layer Flow chart of the outline of the manufacturing process of the digital photosensitive drum Process schematic diagram of the manufacturing process (1) Process schematic diagram of the manufacturing process (2) Process schematic diagram of the manufacturing process (Part 3) Process schematic diagram of the manufacturing process (4) Process schematic diagram of the manufacturing process (part 5) Process schematic diagram of the manufacturing process (Part 6) Block diagram of digital photoconductor drum drive circuit Digital photoconductor drum drive timing chart Data transfer block diagram Conceptual diagram of pre-transfer exposure in Example 1 Conceptual diagram of pre-transfer exposure in Example 2 Conceptual diagram of pre-transfer exposure in Example 3 Conceptual diagram of pre-transfer exposure in Example 4 Conceptual diagram of pre-transfer exposure in Example 5 Conceptual diagram showing the state of toner scattering by pre-transfer exposure Figure quoted from Japanese Patent Application Laid-Open No. 8-137165, which is a conventional example Figure quoted from Japanese Patent Application Laid-Open No. 11-316489 which is a conventional example

Explanation of symbols

  A..Electrophotographic image forming apparatus, 2..Digital photosensitive drum, 3 (a to d) .. Charging device, 4 (Y.M.C.Bk) .. Developing cartridge, 5..Intermediate transfer belt unit 33 .. Encoder wheel section, 34.. Phase detector, 40.. Cylindrical substrate, 50 .. Self-luminous device section, 51 .. Signal line (first electrode line) / scanning line (second electrode line) control section (Control circuit part), 52... Signal line layer, 52 e... Signal line (first electrode line), 53... Organic EL light emitting layer, 54 .. scan line layer, 54 a. Separating part, 61 .. Insulating layer (transparent insulating / gas barrier layer), 62 .. Transparent conductive layer, 70. SV ·· Potential sensor

Claims (5)

A rotatable image carrier, a charging means for charging the image carrier, a developing means for developing an electrostatic latent image formed on the image carrier as a developer image, and the developer image as a transfer medium In an image forming apparatus having a transfer means for transferring and a control means,
The image carrier has a light emitting element matrix layer, and a photosensitive layer laminated on the light emitting element matrix layer and charged by the charging means,
The control means forms an electrostatic latent image on the charged surface of the photosensitive layer by causing each light emitting pixel portion of the light emitting element matrix layer to emit light corresponding to image data and exposing the photosensitive layer. Light emission corresponding to at least a non-image forming portion of the photosensitive layer between a latent image forming sequence and an image carrier rotating direction downstream from the developing unit and an image carrier rotating direction upstream from the transfer unit. An image forming apparatus comprising: a pre-transfer exposure sequence in which a light emitting pixel portion of an element matrix layer portion emits light and is exposed a plurality of times in the same region as the at least non-image forming portion of the photosensitive layer. By the multiple exposure, the surface potential of the photoreceptor layer is
| Non-image forming part potential |> | Image forming part potential |
The image forming apparatus according to claim 1, wherein the relationship is satisfied. The image forming apparatus according to claim 1, wherein the surface potential of the non-image forming portion of the photosensitive layer is set to 0 V by the multiple exposure.   And a potential detecting means for detecting a surface potential of the photosensitive layer between an image carrier rotating direction downstream of the developing means and an image carrier rotating direction upstream of the transfer means, and the control means 4. The image forming apparatus according to claim 1, wherein when the absolute value of the potential measurement value of the potential detection means is smaller than the reference value, the pre-transfer exposure amount in the pre-transfer exposure sequence is reduced. A rotatable image carrier, a charging means for charging the image carrier, a developing means for developing an electrostatic latent image formed on the image carrier as a developer image, and the developer image as a transfer medium In an image forming apparatus having a transfer means for transferring and a control means,
The image carrier has a light emitting element matrix layer, and a photosensitive layer laminated on the light emitting element matrix layer and charged by the charging means,
The control means forms an electrostatic latent image on the charged surface of the photosensitive layer by causing each light emitting pixel portion of the light emitting element matrix layer to emit light corresponding to image data and exposing the photosensitive layer. Light emission corresponding to at least a non-image forming portion of the photosensitive layer between a latent image forming sequence and an image carrier rotating direction downstream from the developing unit and an image carrier rotating direction upstream from the transfer unit. An image forming apparatus comprising: a pre-transfer exposure sequence in which a light emitting pixel portion of an element matrix layer portion emits light and continuously exposes at least the same area as the non-image forming portion of the photosensitive layer.

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